Assessment of the oil release of spray-dried gum arabic/citronella oil microcapsules depending on the production parameters

Assessment of the oil release of spray-dried gum arabic/citronella oil microcapsules depending on the production parameters | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Assessment of the oil release of spray-dried gum arabic/citronella oil microcapsules depending on the production parameters Dilayda Kanmaz, Serkan Yildiz, Serpil Koral Koc, Gizem Manasoglu, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5930577/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Functionalization by using essential oils is an environmentally friendly approach that can be adapted to many industries. However, the oxidative sensitive and high volatile structures of the essential oils inhibit their potential. Microencapsulation enables the essential oils to be coated and protected by a wall material. The protection and the release of the confined essential oil depend on the morphologies of the microcapsules thus their production parameters. Therefore, selection of the appropriate microencapsulation parameters is crucial. This study aims to determine the optimum parameters to produce gum arabic/citronella essential oil (GA/CEO) spray-dried microcapsules. The effects of wall-to-core ratio, inlet temperature, and feed rate were investigated. Twenty-seven GA/CEO microcapsule samples were produced by using three wall-to-core ratios (3:1, 4:1, 6:1 v/v), three inlet temperatures (120, 150, 180°C), and three feed rates (1, 2.5, 5 mL/min). The morphology, particle size, oil efficiency, and oil release of the microcapsules were evaluated by considering the production parameters. The analyses revealed that GA/CEO microcapsules with smooth surfaces and homogeneous particle sizes were successfully produced. The oil efficiency of the microcapsules ranged between 20–90%, depending on the production parameters. The release rates of CEO varied between 37.8–89.5%. In conclusion, the microcapsules produced with a wall-to-core ratio of 4:1, temperatures above 150°C, and feed rates above 2.5 mL/min have potential for applications where prolonged release are expected. Microcapsule Spray drying Citronella oil Gum arabic Release behavior Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction Essential oils and their components are odoriferous, complex natural mixtures that can be extracted from different parts of aromatic plants such as flowers, fruits, leaves, seeds, roots, barks, and stems (Hüsnü et al. 2007 ; Shaaban et al. 2012 ). In addition to their multifunctional properties, they have attracted attention for many years due to their natural and eco-friendly characteristics and have been utilized in various industries (Mohammed et al. 2020 ; Tariq et al. 2022 ). However, essential oils are volatile compounds that are highly sensitive to environmental factors such as temperature, light, humidity, oxygen, and interaction with other chemical components. Therefore, their industrial applications might be challenging (Burt 2004 ; Bakry et al. 2016 ). Microencapsulation is an effective and preferred technology for exceeding these limits and improving the handling properties of these compounds by protecting core material, enhancing stability, and providing controlled release (Fang and Bhandari 2010 ; Carvalho et al. 2019 ). Microencapsulation is the process of creating small capsules by coating tiny solid, liquid, or gas particles with a protective wall (encapsulating agent) that isolates the core compound from the external environment (Gharsallaoui et al. 2007 ). Although the application method selection depends on several factors, spray drying is one of the oldest and most widely preferred techniques, especially for encapsulating flavors and essential oils (Re 1998 ; Veiga et al. 2019 ). In addition to being a flexible, fast, continuous, repeatable, and economical process with low operating costs, the variety of encapsulating matrices, the high retention efficiency, and the stability of compounds are also advantages of the method (Sousa et al. 2022 ; Altay et al. 2024 ). The process involves atomizing liquid droplets into a hot drying medium, leading to rapid water evaporation, which results in a quick wall formation and immediate entrapment of the core material (Tonon et al. 2011 ; Mejia-Argueta et al. 2021 ). Optimization of spray drying parameters is crucial as they directly impact the encapsulation performance, properties, and quality of the final product (Mohammed et al. 2020 ; Altay et al. 2024 ). Citronella essential oil (CEO), discovered in 1910 (Katz et al. 2008 ), is one of the essential oils that stands out with its antimicrobial, antibacterial, antifungal, antiparasitic, antispasmodic, insect repellent, carminative, flavoring activity, and ecological pesticide properties (Nerio et al. 2010 ; Dutta et al. 2016 ; Devi et al. 2021 ). It is obtained from the leafy parts of the Cymbopogon species and has a pale to dark yellow color (Lis-Balchin 2006 ). There are two primary sources of CEO in trade: Ceylon type, obtained from Cymbopogon nardus, and Java type from Cymbopogon winterianus. Approximately 80% of CEO consists of citronellal (33.9%), geraniol (18.1%), and citronellol (11.1%) monoterpenes (Beneti et al. 2011 ; Wany et al. 2013 ). It is utilized in various industries such as cosmetics (soap, perfumery), camping and outdoor products (sprays, candles, and lotions), food, agriculture, pharmaceuticals, textiles, medicine, veterinary, and aromatherapy due to its beneficial properties (Ali et al. 2017 ; Singh et al. 2017 ; Khounvilay et al. 2019 ). CEO, registered by the US Environmental Protection Agency (US EPA) especially as an insect-repellent ingredient for skin application, is one of the most widely used natural mosquito-repellent oils on the market (Katz et al. 2008 ; Nerio et al. 2010 ; Maia and Moore 2011 ). However, it has some drawbacks when used directly: It is sensitive to oxidative degradation, provides short-term protection due to its high volatility at high temperatures (Agrawal et al. 2017 ), rapidly evaporating behavior (Solomon et al. 2012 ), and it may cause sensitivity and irritation on human skin when used directly or in high amounts (Songkro et al. 2012 ; Yadav et al. 2014 ). Therefore, like many essential oils, an accurate and efficient encapsulation process is necessary to overcome its limitations (Yingngam et al. 2019 ). In the literature, there are some studies evaluating the mosquito-repellent properties of microcapsules containing CEO (Solomon et al. 2012 ; Ribeiro et al. 2016 ; Songkro et al. 2018 ; Sariişik et al. 2022 ; Tariq et al. 2022 ; Murtaza et al. 2023 ). Several studies explored encapsulating CEO using different wall materials and methods for various applications. In previous research, acacia gum (Yingngam et al. 2019 ), tamarin gum (Khounvilay et al. 2018 ), gum arabic (GA)/maltodextrin, GA/whey protein concentrate powder, maltodextrin/whey protein concentrate powder (Duarte et al. 2023 ), skimmed milk powder/whey protein concentrate (Baranauskiene et al. 2006 ), chitosan/gelatin (Aziz et al. 2016 ), GA/gelatin (Bezerra et al. 2016 ; Tariq et al. 2022 ), gelatin/maltodextrin and whey protein isolate/GA (Aisyah et al. 2022 ), gelatin/ acacia gum (Songkro et al. 2018 ), gelatin and sodium alginate (De Matos et al. 2018 ), ethyl cellulose (Sariişik et al. 2022 ), poly (e-caprolactone) (PCL) (Pardini et al. 2021 ) were utilized as wall materials to encapsulate CEO. The choice of wall material is crucial in the microencapsulation process, as it is one of the primary factors affecting encapsulation efficiency and the stability of the produced powders (Alvarenga Botrel et al. 2012 ). GA, a natural polysaccharide, is highly favored as a wall material in microencapsulation technology due to its numerous beneficial properties. These include high solubility and low viscosity in aqueous solutions, the ability to produce stable emulsions with most oils in a wide pH range, excellent retention of volatile substances during drying, and effective film forming capabilities (Jafari et al. 2008 ; Mohammed et al. 2020 ). Tupuna et al. ( 2018 ) stated that GA is a more effective wall material than maltodextrin in terms of encapsulation efficiency. Various methods, including coacervation (Solomon et al. 2012 ; Aziz et al. 2016 ; Bezerra et al. 2016 ; Songkro et al. 2018 ; Aisyah et al. 2022 ; Tariq et al. 2022 ), electrospraying (Pardini et al. 2021 ), emulsion extrusion (Murtaza et al. 2023 ), and spray drying (Baranauskiene et al. 2006 ; Khounvilay et al. 2018 ; Khounvilay et al. 2019 ; Yingngam et al. 2019 ; Duarte et al. 2023 ;), were used to encapsulate CEO. Microcapsules find a wide range of applications in different industries, including textiles. Textile surfaces can gain different functions by application of various microcapsules. This paper presents a systematic study to determine the appropriate emulsion concentration and process parameters to obtain GA/CEO microcapsules by spray drying. To the best of our knowledge, there is no detailed study concerning both the concentration of the wall-to-core and the spray drying conditions for the microcapsule production of CEO in GA. The microcapsules were evaluated by means of their morphology, size distribution, oil efficiency, and release behavior. The results were discussed by considering the effects of the production parameters. We believe that the findings of this study would provide insight into further research about the production of microcapsules via spray drying. Experimental Materials GA (Sigma-Aldrich) was utilized as the wall-forming polymer. CEO (Cymbopogon winterianus; Florame), with a density of 0.8587 g/mL, was used as the core material. Ethyl alcohol (Tekkim), with a purity of > 99.9%, and distilled water were employed as solvents. Preparation of the microcapsules The CEO was diluted in ethyl alcohol at a concentration of 15% (w/v) at room temperature. Considering previous studies (Duarte et al. 2023 ), the amount of oil in the emulsion was kept at the maximum level. The GA, which will form the microcapsule wall, was dissolved in pure water at 70°C by stirring on a magnetic stirrer for 5 hours to be prepared at two different concentrations of 30% and 40% (w/v). Then, microencapsulation emulsion solutions were obtained by adding the CEO solution dropwise to the GA solutions cooled to 30°C at room temperature. Three different emulsion solutions with GA/CEO ratios of 3:1, 4:1 and 6:1 (v/v) were prepared using 30% and 40% GA in 60/40 wall/core formulation and 30% GA in 75/25 wall/core formulation, respectively. The prepared emulsions were kept at rest for 6 hours to observe that phase separation did not occur. Viscosity of the emulsions was measured at 100 rpm using a Brookfield Viscosimeter at standard room temperature. The viscosity values for microencapsulation emulsions of 3:1, 4:1, and 6:1 were 22.4, 60.8, and 44.8 cP, respectively. The emulsions were dried and transformed into microcapsules in an inert nitrogen environment using the Buchi S-300 Advanced Spray Dryer Device equipped with a two-fluid nozzle (0.7 mm). Three different inlet temperatures (120, 150, and 180°C) and feed rates (1, 2.5, and 5 mL/min) were studied during production. The spray gas and drying air flow rates were kept constant at 1800 L/h and 35 m 3 /h, respectively. Outlet temperatures were recorded below 55°C. The microcapsule powders were collected in glass containers, and analyses were conducted immediately. Powder yield (the ratio of the weight of microcapsules produced to the weight of microcapsules that should theoretically be obtained) was determined by weighing the produced microcapsule powder with a digital precision scale. The powder yields changed in the range of 55–76%. Variable parameters and microcapsule codes are given in Table 1 . Table 1 Process parameters and sample codes Sample code Wall/core ratio (v/v) Inlet temperature (°C) Feed rate (mL/min) 3:1_120_1 3:1 120 1 3:1_120_2.5 3:1 120 2.5 3:1_120_5 3:1 120 5 3:1_150_1 3:1 150 1 3:1_150_2.5 3:1 150 2.5 3:1_150_5 3:1 150 5 3:1_180_1 3:1 180 1 3:1_180_2.5 3:1 180 2.5 3:1_180_5 3:1 180 5 4:1_120_1 4:1 120 1 4:1_120_2.5 4:1 120 2.5 4:1_120_5 4:1 120 5 4:1_150_1 4:1 150 1 4:1_150_2.5 4:1 150 2.5 4:1_150_5 4:1 150 5 4:1_180_1 4:1 180 1 4:1_180_2.5 4:1 180 2.5 4:1_180_5 4:1 180 5 6:1_120_1 6:1 120 1 6:1_120_2.5 6:1 120 2.5 6:1_120_5 6:1 120 5 6:1_150_1 6:1 150 1 6:1_150_2.5 6:1 150 2.5 6:1_150_5 6:1 150 5 6:1_180_1 6:1 180 1 6:1_180_2.5 6:1 180 2.5 6:1_180_5 6:1 180 5 Characterization of the microcapsules Size distribution analysis Particle size distribution was measured with a Horiba LA-960V2 Particle Size Analysis Test Device using laser diffraction. Distilled water was used as dispersant. The refractive index of CEO was set at 1.470. Three percentiles (D 10 , D 50 , and D 90 ), volume-weighted average size (D 4,3 ), and span index of the volume distribution were determined. The span index was calculated according to the Eq. 1. Span index = (D 90 – D 10 ) / D 50 (1) Scanning electron microscopy (SEM) analysis SEM analyses were applied to observe the morphology of the microcapsules using a Carl Zeiss AG-EVO 40XVP Scanning Electron Microscope. In order to make the samples conductive, the samples were coated with gold/palladium prior to the analysis. Fourier Transform Infrared Spectroscopy (FTIR) analysis GA and CEO presence in the microcapsule were examined over one sample (Sample code: 4:1_180_5) by FTIR analyses with a Shimadzu IR-Tracer100 FTIR device. Thirty-two scans were performed in the 500–4000 cm − 1 wavenumber range with a resolution of 4 cm − 1 . Essential oil efficiency GA and CEO mounts in the microcapsules was determined through thermogravimetric analysis (TGA) with a Shimadzu DTG-60H TGA device. During the experiments, samples were loaded in aluminum pans along with the standard reference aluminum. TGA thermograms were recorded from room temperature to 500°C at a rate of 10°C/min. The weight loss up to 100°C was evaluated as the water loss in the sample. The weight loss between 100 and 250°C was measured as CEO loss. The essential oil efficiency was calculated using the following Eq. 2: CEO efficiency (%) = (W TGA / (W MICROCAPSULE / R CEO )) x 100 (2) where W TGA (mg) is CEO amount determined from TGA, W MICROCAPSULE (mg) is the amount of the microcapsule produced, and R CEO is the theoretical CEO ratio in the microcapsule (can be taken as 4 for the 3:1 wall/core, 5 for the 4:1 wall/core, and 7 for the 6:1 wall/core). CEO Release During the TGA, the time-dependent release behavior of CEO-loader microcapsules was also investigated. For this purpose, the amount of CEO change in the microcapsules was determined over a period of 150 minutes at a constant temperature of 40°C. The obtained mass changes were transferred to Excel, and a graph of the cumulative CEO release percentage over time was plotted. Results and discussion Morphology of the microcapsules SEM images of the microcapsules are given in Fig. 1 – 3 . SEM images showed that, in general, the microcapsules aggregated, there were dents in their structures, their spherical forms were distorted, and there were variations in their size distributions. It is known that spray-dried microcapsules may have dents in their structures, and they often aggregate (Rosenberg et al. 1985 ; Ghosh 2006 ; Gharsallaoui et al. 2007 ). On the other hand, the microcapsules had smooth surfaces without any cracks or pores, which is important to increase the oil retention. Tendency to aggregate, and defects in the spherical form on the surface depend on many parameters, such as wall thickness, emulsion viscosity, spray gas pressure/temperature/flow rate, the surface tension of the oil, and drying temperature. It was concluded that microcapsules, especially those with a wall/core ratio of 6:1, show an evident agglomeration, and this will pose a problem in terms of dispersion in the production processes where they will be used. Chemical structure of the microcapsules FTIR analysis was conducted on one of the produced microcapsules to identify the characteristic peaks of CEO and GA. Figure 4 and Table 2 present the infrared spectra of CEO, GA, and one of the GA/CEO microcapsules (4:1_180_5). CEO contains various terpenes in its structure. For the spectrum of CEO, the peaks corresponds to the variety of terpenes in its structure. Therefore, the peaks observed in CEO corresponds to the chemical functional groups of these terpenes, primarily citronellal, citronellol, and geraniol (Songkro et al. 2012 ). In the spectrum, the peak at 3375 cm − 1 can be attributed to the free O − H stretching vibration, which is related to the citronellol and geraniol in CEO. These two components are the primary alcohols of CEO and can participate in intermolecular hydrogen bonding resulting an increasing O − H bond length (Truzzi et al. 2021 ). The peak around ~ 3000 − 2800 cm − 1 corresponds to C − H stretching (Ben-Fadhel et al. 2022 ). Another characteristic group of CEO is the aldehyde of citronellal. The peaks at 2725 and 1726 cm − 1 appeared due to the H − C terminal aldehydic stretching and C = O stretching of aldhyte (Truzzi et al. 2021 ). Other characteristic peaks of CEO at 1641, 1377, and 1008 cm − 1 appeared due to the O − H bend, deformation of C − O−H group, and C − O stretch, respectively (Songkro et al. 2012 ). For GA, the characteristic bands at 3600 − 3000, 3000 − 2800, 1600, and 1000 cm − 1 appeared due to the presence of hydrogen bonded O − H group, the presence of sugars, alkane, and aldehyde C − H stretch, stretching of C = O of the carboxylic group, and presence of glycosidic linkage, respectively (Daoub et al. 2018 ; Thombare et al. 2023 ). For the GA/CEO microcapsule, the large peaks around ~ 3600 − 3300 cm − 1 , which correspond to O − H stretching vibration for CEO and hydrogen bonded O − H group for GA, is also observed in the same range. The peak which indicates the C–H stretching was appeared around ~ 3000 − 2800 cm − 1 . The peaks at 1726 and 1641 cm − 1 for CEO shifted to 1720 and 1604 cm − 1 for GA/CEO, respectively. Deformation of C − O−H group of CEO was detected at 1377 cm − 1 . Moreover, a sharpened peak at 1043 cm − 1 was observed. This peak can be attributed to the C − O stretch of CEO, and glycosidic linkage of GA. It was confirmed that the characteristic peaks of CEO and GA were detected on the GA/CEO microcapsule indicating the successful integration of CEO into GA. Table 2 Functional groups of CEO and GA Peak number CEO Specific wavenumber (cm − 1 ) Functional group-chemical bond 1 3600 − 3300 O − H stretching vibration 2 3000 − 2800 C–H stretching 3 2725 H − C terminal aldehydic stretching 4 1726 C = O stretching of aldehyde 5 1641 O − H bend 6 1377 deformation of C − O−H group 7 1008 C − O stretch GA 8 3600 − 3300 hydrogen bonded O − H group 9 3000 − 2800 C − H stretching 10 1600 stretching of C = O of the carboxylic group 11 1000 glycosidic linkage GA/CEO microcapsule 12 3600 − 3300 O − H stretching vibration & hydrogen bonded O − H group 13 3000 − 2800 C–H stretching 14 1720 C = O stretching of aldehyde 15 1604 stretching of C = O of the carboxylic group 16 1377 deformation of C − O−H group 17 1043 C − O stretch & glycosidic linkage Particle size analysis of the microcapsules The particle size analyses of the microcapsules produced under different parameters are presented in Table 3 . Particle size distribution can be affected by emulsion viscosity, feed temperature, and feed rate. The span index of the microcapsules showing a unimodal distribution varied between 0.49–2.72. The span index, which indicates polydispersity of the microcapsules and quantifies the breadth of the particle size distribution (Tan and Nakajima 2005 ; Oliveira et al. 2010 ), showed that the produced particles were homogeneous. The results showed that the average sizes of microcapsules produced at wall-to-core ratios of 3:1, 4:1, and 6:1 with varying inlet temperatures and feed rates were ranged between 1 and 9 µm. Studies in the literature (Rosenberg et al. 1988 ; Laohasongkram et al. 2011 ; Saleem et al. 2017 ; Yue et al. 2020 ; Chaturvedi and Chakraborty 2022 ; Ixtaina et al. 2022 ) have reported that the average size of microcapsules prepared via spray-drying with various oils ranges from 3 to 15 µm. As the microcapsule size decreased, the increase in the tendency to agglomerate was also seen in SEM images. Table 3 Particle size analysis results Sample code Average size (µm) D10* (µm) D50* (µm) D90* (µm) Span index 3:1_120_1 2.84 1.03 2.09 5.47 2.12 3:1_120_2.5 1.39 0.51 1.02 2.35 1.80 3:1_120_5 1.75 0.79 1.41 3.01 1.57 3:1_150_1 1.85 0.86 1.58 3.22 1.49 3:1_150_2.5 6.13 1.00 1.95 5.69 2.41 3:1_150_5 4.86 0.57 1.19 3.33 2.32 3:1_180_1 7.72 5.94 7.57 9.78 0.51 3:1_180_2.5 7.95 5.96 7.62 9.85 0.51 3:1_180_5 8.10 6.05 7.93 10.42 0.55 4:1_120_1 1.01 0.97 1.69 3.44 1.46 4:1_120_2.5 2.69 1.03 2.03 5.17 2.04 4:1_120_5 1.28 0.57 1.09 2.19 1.49 4:1_150_1 7.76 5.93 7.59 9.85 0.52 4:1_150_2.5 8.03 6.00 7.87 10.29 0.55 4:1_150_5 3.43 1.10 2.29 7.33 2.72 4:1_180_1 1.61 0.80 1.43 2.65 1.29 4:1_180_2.5 8.72 6.74 8.56 11.03 0.50 4:1_180_5 3.53 1.14 2.56 7.27 2.39 6:1_120_1 1.48 0.85 1.35 2.29 1.07 6:1_120_2.5 1.74 0.66 1.55 3.07 1.55 6:1_120_5 2.35 1.04 1.91 4.18 1.64 6:1_150_1 2.56 0.83 1.57 4.91 2.60 6:1_150_2.5 1.21 0.11 1.14 1.72 1.41 6:1_150_5 1.54 0.80 1.42 2.47 1.18 6:1_180_1 8.64 6.60 8.48 11.01 0.52 6:1_180_2.5 7.32 5.53 7.19 9.33 0.53 6:1_180_5 8.73 6.78 8.58 11.01 0.49 * D10, D50 and D90 values ​​indicate the size below 10%, 50% and 90% of the cumulative volume, respectively An increase in the average size values was observed with the increase of the temperature from 120°C to 150 and 180°C. This result was associated that high temperatures caused the structures to form early and did not allow them to shrink. At low temperatures, more shrunken and, therefore smaller diameter particles were obtained in agreement with the literature (Reineccius 2004 ; Tonon et al. 2011 ). In the spray drying method, emulsion viscosity is crucial in determining particle size (Xie et al. 2010 ). A general increase in the average size values ​​was observed with the increase in emulsion viscosity from 22.4 cP to 44.8 and 60.8 cP. Low viscosity emulsions such as 3:1 are easily atomized into small particles during spray drying. When viscosity increases, the fluidity of the liquid decreases, which increases the surface tension of the liquid, making it difficult for droplets to break up. This increases the average size of the microcapsules, as in 6:1 and 4:1. However, above a critical viscosity value, the interface between the core and wall may not form properly, which may reduce the size of the microcapsules (Park et al. 2001 ; Song et al. 2005 ). Increasing the emulsion feed rate generally affected the average particle size. In particular, increasing the feed rate to 5 mL/min produced particles with the highest sizes. With increasing feed flow rate, the mass transfer between the formed droplets and the surrounding gas slowed down, resulting in larger particles (Ilic et al. 2009 ; Hee et al. 2017 ). Essential oil efficiency of the microcapsules Oil efficiency is defined as the ratio of the measured oil content in the microcapsules to the theoretical oil content. Oil efficiency value is an indicator of the essential oil loss during the process of microencapsulation. It is a critical parameter for determining the effectiveness and quality of encapsulated oils. Higher oil efficiency values are essential for more effective and sustained release. The oil efficiency is significantly influenced by the characteristics of the wall/core materials, the specifications of the emulsion, and the conditions of the spray drying process (Jafari et al. 2008 ; Mohammed et al. 2020 ). Studies have reported efficiencies exceeding 70% for various essential oils (Duarte et al. 2023 ), whereas CEO has been capsulated with efficiencies ranging between 65 and 70% (Baranauskiene et al. 2006 ). Figure 5 presents the oil efficiency results as a function of the wall-to-core ratio in the microcapsules. In this study, oil efficiency for the microcapsules produced under different parameters ranged approximately from 20 to 90%. Too low or high temperatures can adversely affect the efficiency of oil in microcapsule production. When the air inlet temperatures are low, it becomes more challenging and delayed to form a solid membrane layer on the surface of the droplets that are sent from the atomizer to the spray drying chamber. As a result, the essential oils within the droplets evaporate more easily, leading to a decrease in efficiency (Gharsallaoui et al. 2007 ; Mohammed et al. 2020 ). When examining the effect of the inlet temperature on oil efficiency, it was observed that efficiency generally increased with rising temperature. Oil efficiency values at 180°C were usually higher than those at 150°C for constant wall concentration and feed rates; however, the lowest results were generally observed at an inlet temperature of 120°C. Similarly, many researchers working on the encapsulation of various oils noted that the efficiency improved with increasing inlet temperature (Bhushan et al. 2017 ; Kalkan et al. 2017 ; Basyigit et al. 2020). Higher air temperature shortens the time required for crust formation, which prevents oil from spreading further onto the particle surface. This results in maximum retention of volatiles. (Huang et al. 2014 ; Murali et al. 2016 ). The 180°C inlet temperature, which generally provides the highest oil efficiency results, also coincides with the temperature range (160–220°C) in the literature, which is expressed as the sufficiently high inlet temperature leads to the rapid formation of the semi-permeable membrane on the droplet surface (Jafari et al. 2008 ). Feed rate is one of the most important parameters affecting microcapsule formation in the spray drying method. It should be adequate to ensure that the liquid evaporates before the particles contact the drying chamber wall (Veiga et al. 2019 ). Generally, better oil efficiency results were obtained at 2.5 and 5 mL/min feed rates compared to 1 mL/min, while keeping the wall-to-core ratio and inlet temperature constant. These findings were consistent with studies reporting higher efficiency by increasing the feed rate (Seddighi Pashaki et al. 2016 ; Geranpour et al., 2019 ). Alvarenga Botrel et al. ( 2012 ) also stated that the improvement in oil retention at high feed rates may be due to the rapid formation of the semi-permeable membrane due to the higher solids content in the drying chamber. However, as an exceptional case, the highest efficiency value was observed at the lowest feed rate of 1 mL/min in samples produced at 180°C temperature with 3:1 wall/core ratio. It is also stated in the literature (Alvarenga Botrel et al. 2012 ) that high oil efficiency can be achieved in high inlet temperature/low feed rate combinations. It is crucial to determine the amount of wall material required to enhance the retention of essential oils and prevent changes caused by oxidation and chemical interactions or volatilization (Alvarenga Botrel et al. 2012 ; Veiga et al. 2019 ). Research indicates that the key factor affecting the retention of volatiles and the encapsulation efficiency during spray drying is the concentration of dissolved solids in the feed emulsion. When comparing wall-to-core ratios of 3:1 and 6:1, both using 30% GA, the samples with 6:1 ratio exhibited higher oil efficiency results than those with 3:1. According to Frascareli et al. ( 2012 ) oil concentration is a critical factor affecting efficiency; specifically, a higher oil concentration typically leads to lower efficiency. Considering that the 6:1 emulsions contained less oil and more gum than the 3:1 samples, these findings align with the existing literature. The effects of oil and gum concentrations on oil efficiency and retention can also be related to emulsion viscosity to some extent. As stated in the Materials section, the viscosity of 4:1 emulsions prepared with 40% GA was higher than that of 3:1 and 6:1 emulsions due to the higher solid content (60.8 cP). The highest oil efficiency results were generally achieved with the 4:1 wall-to-core ratio. This can be related to the fact that the higher viscosity emulsions can lead to decreased internal circulations and oscillations of the droplets and reduce the time needed for crust formation. Additionally, in emulsions with higher solid content, oil diffusion to the drying particle surface becomes more difficult, resulting in enhanced oil retention and efficiency (Jafari et al. 2008 ; Tonon et al. 2011 ). Oil release from the microcapsules The release rate of CEO from microcapsules is influenced by various factors such as the properties of GA and CEO, the structure and sizes of the microcapsules, and the interaction between GA and CEO. The release process occurs in three stages: i) gradual gasification of CEO, ii) burst release of CEO, and iii) CEO diffusion and completion of release (Zhang et al. 2020 ). Figure 6 – 8 show the cumulative release profiles of CEO from microcapsules prepared with wall-to-core ratios of 3:1, 4:1, and 6:1, respectively. It could be seen that the microcapsules exhibited an initial burst release ranging approximately between 22–48% in the first 10 minutes. Although cumulative burst release reached up to ⁓50% for all groups, 4:1 and 6:1 showed lower initial burst release rates in general. The initial burst release is affected by various parameters such as, oil efficiency, polymer relaxation, cross-linking between oil and wall material, oil content on or close to the surface of microcapsule, pore size and distribution of the wall material, wall thickness, incomplete removal of solvent, etc. (Dima et al. 2016 ; Mehran et al. 2020 ; Zhang et al. 2020 ). At lower temperatures, less crosslinking, poor wall formation, or higher wall porosity may occur allowing the essential oil to diffuse more easily to the surface and escape rapidly resulting in higher burst release. In contrast, denser and more compact wall structures can be formed at higher temperatures reducing the burst release. Our results showed that most of the microcapsules produced at temperatures below 180°C exhibited higher burst release which may be related to these factors. The release profiles gradually reached equilibrium under the effect of diffusion with different release rates at the end of 150 minutes. The release rates of CEO varied between 37.8–89.5%, 51.7–77.5%, and 40.3–60.8% for the microcapsules with a wall-to-core ratio of 3:1, 4:1, and 6:1, respectively. It is evident that the release rate of microcapsules with a wall-to-core ratio of 3:1 remained within a relatively wide range, while 4:1 and 6:1 exhibited similar and narrower ranges. Among all groups, 6:1 samples showed a slower release rate. The slow release rate of 6:1 samples can be attributed to the stronger interaction between GA and CEO (Zhang et al. 2020 ). Conclusion Herein we presented a systematic study to determine the appropriate emulsion concentration and process parameters to obtain GA/CEO microcapsules by spray drying. CEO being an interesting additive for several applications, was successfully encapsulated in GA using the spray drying method. Process parameters, such as the wall-to-core ratio, inlet temperature, and feed rate, were investigated to determine their impacts on the properties of the microcapsules. Results indicated that high inlet air temperatures (150 and 180°C) and high emulsion feed rates (2.5 and 5 mL/min) were the best spray drying conditions for the encapsulation of CEO in GA considering the oil efficiency. Also, the highest oil efficiency values (85.5–90.5%) were obtained with a wall-to-core ratio of 4:1. Viscous emulsions and high inlet temperatures in the microencapsulation process resulted in larger particle sizes. Despite some agglomeration and dents in the capsule images, generally, spherical shapes with crack-free surfaces were achieved. The burst release values of all the samples at the end of the first 10 minutes were approximately 50% for all groups, and the release profiles gradually reached equilibrium under the effect of diffusion with varying release rates at the end of 150 minutes. The findings of the study indicate that GA/CEO microcapsules with desired properties can be produced by spray-drying. Being prominent with its mosquito-repellent properties, sustained and prolonged release of CEO is expected for a long-term effect. An alternative approach to achieve this can be embedding the GA/CEO microcapsules into the fiber structure, especially nanofibers. Based on the results, the microcapsules produced with 4:1 wall-to-core ratio at high temperatures can be a promising alternative for a sustained and prolonged release. Declarations Ethics approval and consent to participate Not applicable Consent for publication All authors consented to this publication. Conflict of interest The authors declare that there is no conflict of interest regarding the publication of this article. Funding This study was supported financially by The Scientific Research Commission of Bursa Uludag University (Project Number: FAY-2023-1410). Author Contribution D.K., G.M., C.A.G. and R.C. prepared the emulsions, produced the microcapsules, collected and analyzed the data; S.K.K., S.Y., M.T. and S.D.G characterized the microcapsules, performed the oil release study, collected and analyzed the data; E.K. designed and planned the research, interpreted the data. All authors discussed the results, and wrote, read, edited the final manuscript. 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University","correspondingAuthor":false,"prefix":"","firstName":"Sebnem","middleName":"Duzyer","lastName":"Gebizli","suffix":""},{"id":409398343,"identity":"c6a87e58-1fc3-4481-91b2-f4447b520b67","order_by":8,"name":"Esra Karaca","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA50lEQVRIiWNgGAWjYDACHgglx8DOwCABZh4gUosxAzNCC2MDMVoSG4jWws9z+NmHHzV26RsO8xje+PGLQY7vRgL74wo8WiR724xn9hxLzgVqMbbs7WMwlryRwNh4Bo8Wg/NAb/A2MIO0mEnw9jAkbgBpwecy+/Psnxn/NtSnGwC1SP7tYagnqMWAt8eYmbfhcAJIizTPD4YEA0JaJM6cKWaWOXbccOZhtmJr2QYJw5lnHjbOxKeFvyd9M+Obmmp5vuPNG2+++WMDZCQf+IhPCypgbANFDYGYRAN/SFE8CkbBKBgFIwUAAM8gTn5n0r7vAAAAAElFTkSuQmCC","orcid":"","institution":"Bursa Uludağ University","correspondingAuthor":true,"prefix":"","firstName":"Esra","middleName":"","lastName":"Karaca","suffix":""}],"badges":[],"createdAt":"2025-01-30 13:23:20","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5930577/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5930577/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":75312487,"identity":"dcb219dc-1553-42ff-8f54-6f246f7172a3","added_by":"auto","created_at":"2025-02-03 09:14:33","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":82642,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of GA/CEO microcapsules produced with 3:1 wall-to-core ratio (the scale bar shows 10 µm)\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5930577/v1/5139c3efdb95c1edcaea9185.jpg"},{"id":75312486,"identity":"9ae75ef4-25b1-4578-92fa-ecc2d57425e8","added_by":"auto","created_at":"2025-02-03 09:14:33","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":87079,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of GA/CEO microcapsules produced with 4:1 wall-to-core ratio (the scale bar shows 10 µm)\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5930577/v1/fcbacf06d0bb874ad002164a.jpg"},{"id":75312488,"identity":"ed6e1895-1558-4057-9cae-c76186d200ff","added_by":"auto","created_at":"2025-02-03 09:14:33","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":81783,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of GA/CEO microcapsules produced with 6:1 wall-to-core ratio (the scale bar shows 10 µm)\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5930577/v1/0387caa93fb08b9a8ead543c.jpg"},{"id":75312497,"identity":"57b48309-7f0f-439a-825d-b8968116150e","added_by":"auto","created_at":"2025-02-03 09:14:33","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":40668,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR spectra of CEO, GA, and GA/CEO microcapsule (4:1_180_5)\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5930577/v1/20375870dfe435b3a262da75.jpg"},{"id":75313002,"identity":"565f4952-bcad-4a6b-a0ba-958301ecada5","added_by":"auto","created_at":"2025-02-03 09:22:33","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":57849,"visible":true,"origin":"","legend":"\u003cp\u003eOil efficiency results of GA/CEO microcapsules with wall-to-core ratio; a)3:1, b)4:1, c)6:1\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5930577/v1/08984b6babe3ddc2b03d9337.jpg"},{"id":75312500,"identity":"b3d4d9d4-3fd2-42a3-be51-cead1b3b9e09","added_by":"auto","created_at":"2025-02-03 09:14:33","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":49639,"visible":true,"origin":"","legend":"\u003cp\u003eCEO release from GA/CEO microcapsules produced with 3:1 wall-to-core ratio The inset shows the CEO release within the first 10 minutes\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5930577/v1/5ec1b2c2fdef921c82e559ad.jpg"},{"id":75312502,"identity":"d912cc7c-625f-418b-ac2c-e211e0a716d8","added_by":"auto","created_at":"2025-02-03 09:14:34","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":47302,"visible":true,"origin":"","legend":"\u003cp\u003eCEO release from GA/CEO microcapsules produced with 4:1 wall-to-core ratio The inset shows the CEO release within the first 10 minutes\u003c/p\u003e","description":"","filename":"7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5930577/v1/f5c5a2618e5a1c9fbf8a6b8e.jpg"},{"id":75313003,"identity":"73b96791-9ed2-41a0-8e98-450b14386c72","added_by":"auto","created_at":"2025-02-03 09:22:33","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":45500,"visible":true,"origin":"","legend":"\u003cp\u003eCEO release from GA/CEO microcapsules produced with 6:1 wall-to-core ratio The inset shows the CEO release within the first 10 minutes\u003c/p\u003e","description":"","filename":"8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5930577/v1/ef2561c6bb047bd4d62b83af.jpg"},{"id":76586951,"identity":"c32e45be-100b-48ce-aa7a-ae71adf4c239","added_by":"auto","created_at":"2025-02-18 16:01:47","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1619464,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5930577/v1/19216b4b-7810-415d-b048-5870231c8fc7.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Assessment of the oil release of spray-dried gum arabic/citronella oil microcapsules depending on the production parameters","fulltext":[{"header":"Introduction","content":"\u003cp\u003eEssential oils and their components are odoriferous, complex natural mixtures that can be extracted from different parts of aromatic plants such as flowers, fruits, leaves, seeds, roots, barks, and stems (H\u0026uuml;sn\u0026uuml; et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Shaaban et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). In addition to their multifunctional properties, they have attracted attention for many years due to their natural and eco-friendly characteristics and have been utilized in various industries (Mohammed et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Tariq et al. \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). However, essential oils are volatile compounds that are highly sensitive to environmental factors such as temperature, light, humidity, oxygen, and interaction with other chemical components. Therefore, their industrial applications might be challenging (Burt \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Bakry et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Microencapsulation is an effective and preferred technology for exceeding these limits and improving the handling properties of these compounds by protecting core material, enhancing stability, and providing controlled release (Fang and Bhandari \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Carvalho et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Microencapsulation is the process of creating small capsules by coating tiny solid, liquid, or gas particles with a protective wall (encapsulating agent) that isolates the core compound from the external environment (Gharsallaoui et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). Although the application method selection depends on several factors, spray drying is one of the oldest and most widely preferred techniques, especially for encapsulating flavors and essential oils (Re \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e1998\u003c/span\u003e; Veiga et al. \u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). In addition to being a flexible, fast, continuous, repeatable, and economical process with low operating costs, the variety of encapsulating matrices, the high retention efficiency, and the stability of compounds are also advantages of the method (Sousa et al. \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Altay et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The process involves atomizing liquid droplets into a hot drying medium, leading to rapid water evaporation, which results in a quick wall formation and immediate entrapment of the core material (Tonon et al. \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Mejia-Argueta et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Optimization of spray drying parameters is crucial as they directly impact the encapsulation performance, properties, and quality of the final product (Mohammed et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Altay et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eCitronella essential oil (CEO), discovered in 1910 (Katz et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2008\u003c/span\u003e), is one of the essential oils that stands out with its antimicrobial, antibacterial, antifungal, antiparasitic, antispasmodic, insect repellent, carminative, flavoring activity, and ecological pesticide properties (Nerio et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Dutta et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Devi et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). It is obtained from the leafy parts of the Cymbopogon species and has a pale to dark yellow color (Lis-Balchin \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). There are two primary sources of CEO in trade: Ceylon type, obtained from Cymbopogon nardus, and Java type from Cymbopogon winterianus. Approximately 80% of CEO consists of citronellal (33.9%), geraniol (18.1%), and citronellol (11.1%) monoterpenes (Beneti et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Wany et al. \u003cspan citationid=\"CR79\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). It is utilized in various industries such as cosmetics (soap, perfumery), camping and outdoor products (sprays, candles, and lotions), food, agriculture, pharmaceuticals, textiles, medicine, veterinary, and aromatherapy due to its beneficial properties (Ali et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Singh et al. \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Khounvilay et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). CEO, registered by the US Environmental Protection Agency (US EPA) especially as an insect-repellent ingredient for skin application, is one of the most widely used natural mosquito-repellent oils on the market (Katz et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Nerio et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Maia and Moore \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). However, it has some drawbacks when used directly: It is sensitive to oxidative degradation, provides short-term protection due to its high volatility at high temperatures (Agrawal et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), rapidly evaporating behavior (Solomon et al. \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), and it may cause sensitivity and irritation on human skin when used directly or in high amounts (Songkro et al. \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Yadav et al. \u003cspan citationid=\"CR81\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Therefore, like many essential oils, an accurate and efficient encapsulation process is necessary to overcome its limitations (Yingngam et al. \u003cspan citationid=\"CR83\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). In the literature, there are some studies evaluating the mosquito-repellent properties of microcapsules containing CEO (Solomon et al. \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Ribeiro et al. \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Songkro et al. \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Sariişik et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Tariq et al. \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Murtaza et al. \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eSeveral studies explored encapsulating CEO using different wall materials and methods for various applications. In previous research, acacia gum (Yingngam et al. \u003cspan citationid=\"CR83\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), tamarin gum (Khounvilay et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), gum arabic (GA)/maltodextrin, GA/whey protein concentrate powder, maltodextrin/whey protein concentrate powder (Duarte et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), skimmed milk powder/whey protein concentrate (Baranauskiene et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2006\u003c/span\u003e), chitosan/gelatin (Aziz et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), GA/gelatin (Bezerra et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Tariq et al. \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), gelatin/maltodextrin and whey protein isolate/GA (Aisyah et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), gelatin/ acacia gum (Songkro et al. \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), gelatin and sodium alginate (De Matos et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), ethyl cellulose (Sariişik et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), poly (e-caprolactone) (PCL) (Pardini et al. \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) were utilized as wall materials to encapsulate CEO. The choice of wall material is crucial in the microencapsulation process, as it is one of the primary factors affecting encapsulation efficiency and the stability of the produced powders (Alvarenga Botrel et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). GA, a natural polysaccharide, is highly favored as a wall material in microencapsulation technology due to its numerous beneficial properties. These include high solubility and low viscosity in aqueous solutions, the ability to produce stable emulsions with most oils in a wide pH range, excellent retention of volatile substances during drying, and effective film forming capabilities (Jafari et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Mohammed et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Tupuna et al. (\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) stated that GA is a more effective wall material than maltodextrin in terms of encapsulation efficiency. Various methods, including coacervation (Solomon et al. \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Aziz et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Bezerra et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Songkro et al. \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Aisyah et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Tariq et al. \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), electrospraying (Pardini et al. \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), emulsion extrusion (Murtaza et al. \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), and spray drying (Baranauskiene et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Khounvilay et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Khounvilay et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Yingngam et al. \u003cspan citationid=\"CR83\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Duarte et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2023\u003c/span\u003e;), were used to encapsulate CEO.\u003c/p\u003e \u003cp\u003eMicrocapsules find a wide range of applications in different industries, including textiles. Textile surfaces can gain different functions by application of various microcapsules. This paper presents a systematic study to determine the appropriate emulsion concentration and process parameters to obtain GA/CEO microcapsules by spray drying. To the best of our knowledge, there is no detailed study concerning both the concentration of the wall-to-core and the spray drying conditions for the microcapsule production of CEO in GA. The microcapsules were evaluated by means of their morphology, size distribution, oil efficiency, and release behavior. The results were discussed by considering the effects of the production parameters. We believe that the findings of this study would provide insight into further research about the production of microcapsules via spray drying.\u003c/p\u003e"},{"header":"Experimental","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eMaterials\u003c/h2\u003e \u003cp\u003eGA (Sigma-Aldrich) was utilized as the wall-forming polymer. CEO (Cymbopogon winterianus; Florame), with a density of 0.8587 g/mL, was used as the core material. Ethyl alcohol (Tekkim), with a purity of \u0026gt;\u0026thinsp;99.9%, and distilled water were employed as solvents.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003ePreparation of the microcapsules\u003c/h3\u003e\n\u003cp\u003eThe CEO was diluted in ethyl alcohol at a concentration of 15% (w/v) at room temperature. Considering previous studies (Duarte et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), the amount of oil in the emulsion was kept at the maximum level. The GA, which will form the microcapsule wall, was dissolved in pure water at 70\u0026deg;C by stirring on a magnetic stirrer for 5 hours to be prepared at two different concentrations of 30% and 40% (w/v). Then, microencapsulation emulsion solutions were obtained by adding the CEO solution dropwise to the GA solutions cooled to 30\u0026deg;C at room temperature. Three different emulsion solutions with GA/CEO ratios of 3:1, 4:1 and 6:1 (v/v) were prepared using 30% and 40% GA in 60/40 wall/core formulation and 30% GA in 75/25 wall/core formulation, respectively. The prepared emulsions were kept at rest for 6 hours to observe that phase separation did not occur. Viscosity of the emulsions was measured at 100 rpm using a Brookfield Viscosimeter at standard room temperature. The viscosity values for microencapsulation emulsions of 3:1, 4:1, and 6:1 were 22.4, 60.8, and 44.8 cP, respectively.\u003c/p\u003e \u003cp\u003eThe emulsions were dried and transformed into microcapsules in an inert nitrogen environment using the Buchi S-300 Advanced Spray Dryer Device equipped with a two-fluid nozzle (0.7 mm). Three different inlet temperatures (120, 150, and 180\u0026deg;C) and feed rates (1, 2.5, and 5 mL/min) were studied during production. The spray gas and drying air flow rates were kept constant at 1800 L/h and 35 m\u003csup\u003e3\u003c/sup\u003e/h, respectively. Outlet temperatures were recorded below 55\u0026deg;C. The microcapsule powders were collected in glass containers, and analyses were conducted immediately. Powder yield (the ratio of the weight of microcapsules produced to the weight of microcapsules that should theoretically be obtained) was determined by weighing the produced microcapsule powder with a digital precision scale. The powder yields changed in the range of 55\u0026ndash;76%.\u003c/p\u003e \u003cp\u003eVariable parameters and microcapsule codes are given in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eProcess parameters and sample codes\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSample code\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWall/core ratio\u003c/p\u003e \u003cp\u003e(v/v)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eInlet temperature\u003c/p\u003e \u003cp\u003e(\u0026deg;C)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFeed rate\u003c/p\u003e \u003cp\u003e(mL/min)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3:1_120_1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e120\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3:1_120_2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e120\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3:1_120_5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e120\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3:1_150_1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e150\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3:1_150_2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e150\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3:1_150_5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e150\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3:1_180_1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e180\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3:1_180_2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e180\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3:1_180_5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e180\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4:1_120_1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e120\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4:1_120_2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e120\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4:1_120_5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e120\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4:1_150_1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e150\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4:1_150_2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e150\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4:1_150_5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e150\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4:1_180_1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e180\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4:1_180_2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e180\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4:1_180_5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e180\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6:1_120_1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e120\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6:1_120_2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e120\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6:1_120_5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e120\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6:1_150_1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e150\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6:1_150_2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e150\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6:1_150_5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e150\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6:1_180_1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e180\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6:1_180_2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e180\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6:1_180_5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e180\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e\n\u003ch3\u003eCharacterization of the microcapsules\u003c/h3\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eSize distribution analysis\u003c/h2\u003e \u003cp\u003eParticle size distribution was measured with a Horiba LA-960V2 Particle Size Analysis Test Device using laser diffraction. Distilled water was used as dispersant. The refractive index of CEO was set at 1.470. Three percentiles (D\u003csub\u003e10\u003c/sub\u003e, D\u003csub\u003e50\u003c/sub\u003e, and D\u003csub\u003e90\u003c/sub\u003e), volume-weighted average size (D\u003csub\u003e4,3\u003c/sub\u003e), and span index of the volume distribution were determined. The span index was calculated according to the Eq.\u0026nbsp;1.\u003c/p\u003e \u003cp\u003eSpan index = (D\u003csub\u003e90\u003c/sub\u003e \u0026ndash; D\u003csub\u003e10\u003c/sub\u003e) / D\u003csub\u003e50\u003c/sub\u003e (1)\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eScanning electron microscopy (SEM) analysis\u003c/h3\u003e\n\u003cp\u003eSEM analyses were applied to observe the morphology of the microcapsules using a Carl Zeiss AG-EVO 40XVP Scanning Electron Microscope. In order to make the samples conductive, the samples were coated with gold/palladium prior to the analysis.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eFourier Transform Infrared Spectroscopy (FTIR) analysis\u003c/h2\u003e \u003cp\u003eGA and CEO presence in the microcapsule were examined over one sample (Sample code: 4:1_180_5) by FTIR analyses with a Shimadzu IR-Tracer100 FTIR device. Thirty-two scans were performed in the 500\u0026ndash;4000 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e wavenumber range with a resolution of 4 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eEssential oil efficiency\u003c/h3\u003e\n\u003cp\u003eGA and CEO mounts in the microcapsules was determined through thermogravimetric analysis (TGA) with a Shimadzu DTG-60H TGA device. During the experiments, samples were loaded in aluminum pans along with the standard reference aluminum. TGA thermograms were recorded from room temperature to 500\u0026deg;C at a rate of 10\u0026deg;C/min. The weight loss up to 100\u0026deg;C was evaluated as the water loss in the sample. The weight loss between 100 and 250\u0026deg;C was measured as CEO loss. The essential oil efficiency was calculated using the following Eq.\u0026nbsp;2:\u003c/p\u003e \u003cp\u003eCEO efficiency (%) = (W\u003csub\u003eTGA\u003c/sub\u003e / (W\u003csub\u003eMICROCAPSULE\u003c/sub\u003e / R\u003csub\u003eCEO\u003c/sub\u003e)) x 100 (2)\u003c/p\u003e \u003cp\u003ewhere W\u003csub\u003eTGA\u003c/sub\u003e (mg) is CEO amount determined from TGA, W\u003csub\u003eMICROCAPSULE\u003c/sub\u003e (mg) is the amount of the microcapsule produced, and R\u003csub\u003eCEO\u003c/sub\u003e is the theoretical CEO ratio in the microcapsule (can be taken as 4 for the 3:1 wall/core, 5 for the 4:1 wall/core, and 7 for the 6:1 wall/core).\u003c/p\u003e\n\u003ch3\u003eCEO Release\u003c/h3\u003e\n\u003cp\u003eDuring the TGA, the time-dependent release behavior of CEO-loader microcapsules was also investigated. For this purpose, the amount of CEO change in the microcapsules was determined over a period of 150 minutes at a constant temperature of 40\u0026deg;C. The obtained mass changes were transferred to Excel, and a graph of the cumulative CEO release percentage over time was plotted.\u003c/p\u003e"},{"header":"Results and discussion","content":"\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eMorphology of the microcapsules\u003c/h2\u003e \u003cp\u003eSEM images of the microcapsules are given in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003cp\u003eSEM images showed that, in general, the microcapsules aggregated, there were dents in their structures, their spherical forms were distorted, and there were variations in their size distributions. It is known that spray-dried microcapsules may have dents in their structures, and they often aggregate (Rosenberg et al. \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e1985\u003c/span\u003e; Ghosh \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Gharsallaoui et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). On the other hand, the microcapsules had smooth surfaces without any cracks or pores, which is important to increase the oil retention.\u003c/p\u003e \u003cp\u003eTendency to aggregate, and defects in the spherical form on the surface depend on many parameters, such as wall thickness, emulsion viscosity, spray gas pressure/temperature/flow rate, the surface tension of the oil, and drying temperature. It was concluded that microcapsules, especially those with a wall/core ratio of 6:1, show an evident agglomeration, and this will pose a problem in terms of dispersion in the production processes where they will be used.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eChemical structure of the microcapsules\u003c/h2\u003e \u003cp\u003eFTIR analysis was conducted on one of the produced microcapsules to identify the characteristic peaks of CEO and GA. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e and Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e present the infrared spectra of CEO, GA, and one of the GA/CEO microcapsules (4:1_180_5).\u003c/p\u003e \u003cp\u003eCEO contains various terpenes in its structure. For the spectrum of CEO, the peaks corresponds to the variety of terpenes in its structure. Therefore, the peaks observed in CEO corresponds to the chemical functional groups of these terpenes, primarily citronellal, citronellol, and geraniol (Songkro et al. \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). In the spectrum, the peak at 3375 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e can be attributed to the free O\u0026thinsp;\u0026minus;\u0026thinsp;H stretching vibration, which is related to the citronellol and geraniol in CEO. These two components are the primary alcohols of CEO and can participate in intermolecular hydrogen bonding resulting an increasing O\u0026thinsp;\u0026minus;\u0026thinsp;H bond length (Truzzi et al. \u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The peak around ~\u0026thinsp;3000\u0026thinsp;\u0026minus;\u0026thinsp;2800 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to C\u0026thinsp;\u0026minus;\u0026thinsp;H stretching (Ben-Fadhel et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Another characteristic group of CEO is the aldehyde of citronellal. The peaks at 2725 and 1726 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e appeared due to the H\u0026thinsp;\u0026minus;\u0026thinsp;C terminal aldehydic stretching and C\u0026thinsp;=\u0026thinsp;O stretching of aldhyte (Truzzi et al. \u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Other characteristic peaks of CEO at 1641, 1377, and 1008 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e appeared due to the O\u0026thinsp;\u0026minus;\u0026thinsp;H bend, deformation of C\u0026thinsp;\u0026minus;\u0026thinsp;O\u0026minus;H group, and C\u0026thinsp;\u0026minus;\u0026thinsp;O stretch, respectively (Songkro et al. \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e2012\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eFor GA, the characteristic bands at 3600\u0026thinsp;\u0026minus;\u0026thinsp;3000, 3000\u0026thinsp;\u0026minus;\u0026thinsp;2800, 1600, and 1000 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e appeared due to the presence of hydrogen bonded O\u0026thinsp;\u0026minus;\u0026thinsp;H group, the presence of sugars, alkane, and aldehyde C\u0026thinsp;\u0026minus;\u0026thinsp;H stretch, stretching of C\u0026thinsp;=\u0026thinsp;O of the carboxylic group, and presence of glycosidic linkage, respectively (Daoub et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Thombare et al. \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eFor the GA/CEO microcapsule, the large peaks around ~\u0026thinsp;3600\u0026thinsp;\u0026minus;\u0026thinsp;3300 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which correspond to O\u0026thinsp;\u0026minus;\u0026thinsp;H stretching vibration for CEO and hydrogen bonded O\u0026thinsp;\u0026minus;\u0026thinsp;H group for GA, is also observed in the same range. The peak which indicates the C\u0026ndash;H stretching was appeared around ~\u0026thinsp;3000\u0026thinsp;\u0026minus;\u0026thinsp;2800 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The peaks at 1726 and 1641 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for CEO shifted to 1720 and 1604 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for GA/CEO, respectively. Deformation of C\u0026thinsp;\u0026minus;\u0026thinsp;O\u0026minus;H group of CEO was detected at 1377 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Moreover, a sharpened peak at 1043 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was observed. This peak can be attributed to the C\u0026thinsp;\u0026minus;\u0026thinsp;O stretch of CEO, and glycosidic linkage of GA. It was confirmed that the characteristic peaks of CEO and GA were detected on the GA/CEO microcapsule indicating the successful integration of CEO into GA.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eFunctional groups of CEO and GA\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePeak\u003c/p\u003e \u003cp\u003enumber\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eCEO\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpecific wavenumber (cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFunctional group-chemical bond\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3600\u0026thinsp;\u0026minus;\u0026thinsp;3300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eO\u0026thinsp;\u0026minus;\u0026thinsp;H stretching vibration\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3000\u0026thinsp;\u0026minus;\u0026thinsp;2800\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC\u0026ndash;H stretching\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2725\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eH\u0026thinsp;\u0026minus;\u0026thinsp;C terminal aldehydic stretching\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1726\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC\u0026thinsp;=\u0026thinsp;O stretching of aldehyde\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1641\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eO\u0026thinsp;\u0026minus;\u0026thinsp;H bend\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1377\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003edeformation of C\u0026thinsp;\u0026minus;\u0026thinsp;O\u0026minus;H group\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1008\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC\u0026thinsp;\u0026minus;\u0026thinsp;O stretch\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eGA\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3600\u0026thinsp;\u0026minus;\u0026thinsp;3300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ehydrogen bonded O\u0026thinsp;\u0026minus;\u0026thinsp;H group\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3000\u0026thinsp;\u0026minus;\u0026thinsp;2800\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC\u0026thinsp;\u0026minus;\u0026thinsp;H stretching\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1600\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003estretching of C\u0026thinsp;=\u0026thinsp;O of the carboxylic group\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eglycosidic linkage\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eGA/CEO microcapsule\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3600\u0026thinsp;\u0026minus;\u0026thinsp;3300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eO\u0026thinsp;\u0026minus;\u0026thinsp;H stretching vibration \u0026amp; hydrogen bonded O\u0026thinsp;\u0026minus;\u0026thinsp;H group\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3000\u0026thinsp;\u0026minus;\u0026thinsp;2800\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC\u0026ndash;H stretching\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1720\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC\u0026thinsp;=\u0026thinsp;O stretching of aldehyde\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1604\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003estretching of C\u0026thinsp;=\u0026thinsp;O of the carboxylic group\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1377\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003edeformation of C\u0026thinsp;\u0026minus;\u0026thinsp;O\u0026minus;H group\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1043\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC\u0026thinsp;\u0026minus;\u0026thinsp;O stretch \u0026amp; glycosidic linkage\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eParticle size analysis of the microcapsules\u003c/h2\u003e \u003cp\u003eThe particle size analyses of the microcapsules produced under different parameters are presented in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Particle size distribution can be affected by emulsion viscosity, feed temperature, and feed rate. The span index of the microcapsules showing a unimodal distribution varied between 0.49\u0026ndash;2.72. The span index, which indicates polydispersity of the microcapsules and quantifies the breadth of the particle size distribution (Tan and Nakajima \u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Oliveira et al. \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2010\u003c/span\u003e), showed that the produced particles were homogeneous.\u003c/p\u003e \u003cp\u003eThe results showed that the average sizes of microcapsules produced at wall-to-core ratios of 3:1, 4:1, and 6:1 with varying inlet temperatures and feed rates were ranged between 1 and 9 \u0026micro;m. Studies in the literature (Rosenberg et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e1988\u003c/span\u003e; Laohasongkram et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Saleem et al. \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Yue et al. \u003cspan citationid=\"CR84\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Chaturvedi and Chakraborty \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Ixtaina et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) have reported that the average size of microcapsules prepared via spray-drying with various oils ranges from 3 to 15 \u0026micro;m. As the microcapsule size decreased, the increase in the tendency to agglomerate was also seen in SEM images.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eParticle size analysis results\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSample code\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAverage size (\u0026micro;m)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eD10*\u003c/p\u003e \u003cp\u003e(\u0026micro;m)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eD50*\u003c/p\u003e \u003cp\u003e(\u0026micro;m)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eD90*\u003c/p\u003e \u003cp\u003e(\u0026micro;m)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eSpan index\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3:1_120_1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3:1_120_2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.80\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3:1_120_5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.79\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.57\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3:1_150_1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.49\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3:1_150_2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e6.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.41\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3:1_150_5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e4.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.32\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3:1_180_1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e7.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e7.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e9.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.51\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3:1_180_2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e7.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e7.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e9.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.51\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3:1_180_5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e8.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e7.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e10.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.55\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4:1_120_1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.46\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4:1_120_2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.04\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4:1_120_5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.49\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4:1_150_1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e7.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e7.59\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e9.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.52\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4:1_150_2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e8.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e7.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e10.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.55\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4:1_150_5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.72\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4:1_180_1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.29\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4:1_180_2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e8.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e8.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e11.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4:1_180_5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.39\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6:1_120_1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.07\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6:1_120_2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.66\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.55\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6:1_120_5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e4.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.64\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6:1_150_1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e4.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.60\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6:1_150_2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.41\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6:1_150_5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.18\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6:1_180_1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e8.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e8.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e11.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.52\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6:1_180_2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e7.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e7.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e9.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.53\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6:1_180_5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e8.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e8.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e11.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.49\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"6\"\u003e* D10, D50 and D90 values ​​indicate the size below 10%, 50% and 90% of the cumulative volume, respectively\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eAn increase in the average size values was observed with the increase of the temperature from 120\u0026deg;C to 150 and 180\u0026deg;C. This result was associated that high temperatures caused the structures to form early and did not allow them to shrink. At low temperatures, more shrunken and, therefore smaller diameter particles were obtained in agreement with the literature (Reineccius \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Tonon et al. \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn the spray drying method, emulsion viscosity is crucial in determining particle size (Xie et al. \u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). A general increase in the average size values ​​was observed with the increase in emulsion viscosity from 22.4 cP to 44.8 and 60.8 cP. Low viscosity emulsions such as 3:1 are easily atomized into small particles during spray drying. When viscosity increases, the fluidity of the liquid decreases, which increases the surface tension of the liquid, making it difficult for droplets to break up. This increases the average size of the microcapsules, as in 6:1 and 4:1. However, above a critical viscosity value, the interface between the core and wall may not form properly, which may reduce the size of the microcapsules (Park et al. \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Song et al. \u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e2005\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIncreasing the emulsion feed rate generally affected the average particle size. In particular, increasing the feed rate to 5 mL/min produced particles with the highest sizes. With increasing feed flow rate, the mass transfer between the formed droplets and the surrounding gas slowed down, resulting in larger particles (Ilic et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Hee et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eEssential oil efficiency of the microcapsules\u003c/h2\u003e \u003cp\u003eOil efficiency is defined as the ratio of the measured oil content in the microcapsules to the theoretical oil content. Oil efficiency value is an indicator of the essential oil loss during the process of microencapsulation. It is a critical parameter for determining the effectiveness and quality of encapsulated oils. Higher oil efficiency values are essential for more effective and sustained release. The oil efficiency is significantly influenced by the characteristics of the wall/core materials, the specifications of the emulsion, and the conditions of the spray drying process (Jafari et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Mohammed et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Studies have reported efficiencies exceeding 70% for various essential oils (Duarte et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), whereas CEO has been capsulated with efficiencies ranging between 65 and 70% (Baranauskiene et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2006\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e presents the oil efficiency results as a function of the wall-to-core ratio in the microcapsules. In this study, oil efficiency for the microcapsules produced under different parameters ranged approximately from 20 to 90%. Too low or high temperatures can adversely affect the efficiency of oil in microcapsule production. When the air inlet temperatures are low, it becomes more challenging and delayed to form a solid membrane layer on the surface of the droplets that are sent from the atomizer to the spray drying chamber. As a result, the essential oils within the droplets evaporate more easily, leading to a decrease in efficiency (Gharsallaoui et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Mohammed et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). When examining the effect of the inlet temperature on oil efficiency, it was observed that efficiency generally increased with rising temperature. Oil efficiency values at 180\u0026deg;C were usually higher than those at 150\u0026deg;C for constant wall concentration and feed rates; however, the lowest results were generally observed at an inlet temperature of 120\u0026deg;C. Similarly, many researchers working on the encapsulation of various oils noted that the efficiency improved with increasing inlet temperature (Bhushan et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Kalkan et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Basyigit et al. 2020). Higher air temperature shortens the time required for crust formation, which prevents oil from spreading further onto the particle surface. This results in maximum retention of volatiles. (Huang et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Murali et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The 180\u0026deg;C inlet temperature, which generally provides the highest oil efficiency results, also coincides with the temperature range (160\u0026ndash;220\u0026deg;C) in the literature, which is expressed as the sufficiently high inlet temperature leads to the rapid formation of the semi-permeable membrane on the droplet surface (Jafari et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2008\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eFeed rate is one of the most important parameters affecting microcapsule formation in the spray drying method. It should be adequate to ensure that the liquid evaporates before the particles contact the drying chamber wall (Veiga et al. \u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Generally, better oil efficiency results were obtained at 2.5 and 5 mL/min feed rates compared to 1 mL/min, while keeping the wall-to-core ratio and inlet temperature constant. These findings were consistent with studies reporting higher efficiency by increasing the feed rate (Seddighi Pashaki et al. \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Geranpour et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Alvarenga Botrel et al. (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) also stated that the improvement in oil retention at high feed rates may be due to the rapid formation of the semi-permeable membrane due to the higher solids content in the drying chamber. However, as an exceptional case, the highest efficiency value was observed at the lowest feed rate of 1 mL/min in samples produced at 180\u0026deg;C temperature with 3:1 wall/core ratio. It is also stated in the literature (Alvarenga Botrel et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) that high oil efficiency can be achieved in high inlet temperature/low feed rate combinations.\u003c/p\u003e \u003cp\u003eIt is crucial to determine the amount of wall material required to enhance the retention of essential oils and prevent changes caused by oxidation and chemical interactions or volatilization (Alvarenga Botrel et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Veiga et al. \u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Research indicates that the key factor affecting the retention of volatiles and the encapsulation efficiency during spray drying is the concentration of dissolved solids in the feed emulsion. When comparing wall-to-core ratios of 3:1 and 6:1, both using 30% GA, the samples with 6:1 ratio exhibited higher oil efficiency results than those with 3:1. According to Frascareli et al. (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) oil concentration is a critical factor affecting efficiency; specifically, a higher oil concentration typically leads to lower efficiency. Considering that the 6:1 emulsions contained less oil and more gum than the 3:1 samples, these findings align with the existing literature. The effects of oil and gum concentrations on oil efficiency and retention can also be related to emulsion viscosity to some extent. As stated in the Materials section, the viscosity of 4:1 emulsions prepared with 40% GA was higher than that of 3:1 and 6:1 emulsions due to the higher solid content (60.8 cP). The highest oil efficiency results were generally achieved with the 4:1 wall-to-core ratio. This can be related to the fact that the higher viscosity emulsions can lead to decreased internal circulations and oscillations of the droplets and reduce the time needed for crust formation. Additionally, in emulsions with higher solid content, oil diffusion to the drying particle surface becomes more difficult, resulting in enhanced oil retention and efficiency (Jafari et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Tonon et al. \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eOil release from the microcapsules\u003c/h2\u003e \u003cp\u003eThe release rate of CEO from microcapsules is influenced by various factors such as the properties of GA and CEO, the structure and sizes of the microcapsules, and the interaction between GA and CEO. The release process occurs in three stages: i) gradual gasification of CEO, ii) burst release of CEO, and iii) CEO diffusion and completion of release (Zhang et al. \u003cspan citationid=\"CR85\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e show the cumulative release profiles of CEO from microcapsules prepared with wall-to-core ratios of 3:1, 4:1, and 6:1, respectively. It could be seen that the microcapsules exhibited an initial burst release ranging approximately between 22\u0026ndash;48% in the first 10 minutes. Although cumulative burst release reached up to ⁓50% for all groups, 4:1 and 6:1 showed lower initial burst release rates in general. The initial burst release is affected by various parameters such as, oil efficiency, polymer relaxation, cross-linking between oil and wall material, oil content on or close to the surface of microcapsule, pore size and distribution of the wall material, wall thickness, incomplete removal of solvent, etc. (Dima et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Mehran et al. \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Zhang et al. \u003cspan citationid=\"CR85\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAt lower temperatures, less crosslinking, poor wall formation, or higher wall porosity may occur allowing the essential oil to diffuse more easily to the surface and escape rapidly resulting in higher burst release. In contrast, denser and more compact wall structures can be formed at higher temperatures reducing the burst release. Our results showed that most of the microcapsules produced at temperatures below 180\u0026deg;C exhibited higher burst release which may be related to these factors.\u003c/p\u003e \u003cp\u003eThe release profiles gradually reached equilibrium under the effect of diffusion with different release rates at the end of 150 minutes. The release rates of CEO varied between 37.8\u0026ndash;89.5%, 51.7\u0026ndash;77.5%, and 40.3\u0026ndash;60.8% for the microcapsules with a wall-to-core ratio of 3:1, 4:1, and 6:1, respectively. It is evident that the release rate of microcapsules with a wall-to-core ratio of 3:1 remained within a relatively wide range, while 4:1 and 6:1 exhibited similar and narrower ranges. Among all groups, 6:1 samples showed a slower release rate. The slow release rate of 6:1 samples can be attributed to the stronger interaction between GA and CEO (Zhang et al. \u003cspan citationid=\"CR85\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eHerein we presented a systematic study to determine the appropriate emulsion concentration and process parameters to obtain GA/CEO microcapsules by spray drying. CEO being an interesting additive for several applications, was successfully encapsulated in GA using the spray drying method. Process parameters, such as the wall-to-core ratio, inlet temperature, and feed rate, were investigated to determine their impacts on the properties of the microcapsules.\u003c/p\u003e \u003cp\u003eResults indicated that high inlet air temperatures (150 and 180\u0026deg;C) and high emulsion feed rates (2.5 and 5 mL/min) were the best spray drying conditions for the encapsulation of CEO in GA considering the oil efficiency. Also, the highest oil efficiency values (85.5\u0026ndash;90.5%) were obtained with a wall-to-core ratio of 4:1. Viscous emulsions and high inlet temperatures in the microencapsulation process resulted in larger particle sizes. Despite some agglomeration and dents in the capsule images, generally, spherical shapes with crack-free surfaces were achieved. The burst release values of all the samples at the end of the first 10 minutes were approximately 50% for all groups, and the release profiles gradually reached equilibrium under the effect of diffusion with varying release rates at the end of 150 minutes.\u003c/p\u003e \u003cp\u003eThe findings of the study indicate that GA/CEO microcapsules with desired properties can be produced by spray-drying. Being prominent with its mosquito-repellent properties, sustained and prolonged release of CEO is expected for a long-term effect. An alternative approach to achieve this can be embedding the GA/CEO microcapsules into the fiber structure, especially nanofibers. Based on the results, the microcapsules produced with 4:1 wall-to-core ratio at high temperatures can be a promising alternative for a sustained and prolonged release.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eEthics approval and consent to participate\u003c/h2\u003e \u003cp\u003eNot applicable\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent for publication\u003c/strong\u003e \u003cp\u003eAll authors consented to this publication.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eConflict of interest\u003c/h2\u003e \u003cp\u003eThe authors declare that there is no conflict of interest regarding the publication of this article.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThis study was supported financially by The Scientific Research Commission of Bursa Uludag University (Project Number: FAY-2023-1410).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eD.K., G.M., C.A.G. and R.C. prepared the emulsions, produced the microcapsules, collected and analyzed the data; S.K.K., S.Y., M.T. and S.D.G characterized the microcapsules, performed the oil release study, collected and analyzed the data; E.K. designed and planned the research, interpreted the data. All authors discussed the results, and wrote, read, edited the final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors would like to thank to The Scientific Research Commission of Bursa Uludag University for the financial support in the research project (FAY-2023-1410)\u003c/p\u003e\u003ch2\u003eData availability\u003c/h2\u003e \u003cp\u003eThe research data will be available from the corresponding author upon request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAghbashlo M, Mobli H, Madadlou A, Rafiee S (2013) Influence of wall material and inlet drying air temperature on the microencapsulation of fish oil by spray drying. Food Bioproc Tech 6:1561-1569. https://doi.org/10.1007/s11947-012-0796-7\u003c/li\u003e\n\u003cli\u003eAgrawal N, Maddikeri GL, Pandit AB (2017) Sustained release formulations of citronella oil nanoemulsion using cavitational techniques. 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Powder Technol 355:372-385. https://doi.org/10.1016/j.powtec.2019.07.065\u003c/li\u003e\n\u003cli\u003eYue H, Qiu B, Jia M et al (2020) Development and optimization of spray‐dried functional oil microcapsules: oxidation stability and release kinetics. Food Sci Nutr 8:4730-4738. https://doi.org/10.1002/fsn3.1684\u003c/li\u003e\n\u003cli\u003eZhang R, Huang L, Xiong X et al (2020) Preparation and release mechanism of lavender oil microcapsules with different combinations of coating materials. Flavour Fragr J 35:157-166. https://doi.org/10.1002/ffj.3547\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Microcapsule, Spray drying, Citronella oil, Gum arabic, Release behavior","lastPublishedDoi":"10.21203/rs.3.rs-5930577/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5930577/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eFunctionalization by using essential oils is an environmentally friendly approach that can be adapted to many industries. However, the oxidative sensitive and high volatile structures of the essential oils inhibit their potential. Microencapsulation enables the essential oils to be coated and protected by a wall material. The protection and the release of the confined essential oil depend on the morphologies of the microcapsules thus their production parameters. Therefore, selection of the appropriate microencapsulation parameters is crucial. This study aims to determine the optimum parameters to produce gum arabic/citronella essential oil (GA/CEO) spray-dried microcapsules. The effects of wall-to-core ratio, inlet temperature, and feed rate were investigated. Twenty-seven GA/CEO microcapsule samples were produced by using three wall-to-core ratios (3:1, 4:1, 6:1 v/v), three inlet temperatures (120, 150, 180\u0026deg;C), and three feed rates (1, 2.5, 5 mL/min). The morphology, particle size, oil efficiency, and oil release of the microcapsules were evaluated by considering the production parameters. The analyses revealed that GA/CEO microcapsules with smooth surfaces and homogeneous particle sizes were successfully produced. The oil efficiency of the microcapsules ranged between 20\u0026ndash;90%, depending on the production parameters. The release rates of CEO varied between 37.8\u0026ndash;89.5%. In conclusion, the microcapsules produced with a wall-to-core ratio of 4:1, temperatures above 150\u0026deg;C, and feed rates above 2.5 mL/min have potential for applications where prolonged release are expected.\u003c/p\u003e","manuscriptTitle":"Assessment of the oil release of spray-dried gum arabic/citronella oil microcapsules depending on the production parameters","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-02-03 09:14:28","doi":"10.21203/rs.3.rs-5930577/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"6c05db48-9c88-4eab-af4e-00cdb8db14dd","owner":[],"postedDate":"February 3rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-02-18T15:53:39+00:00","versionOfRecord":[],"versionCreatedAt":"2025-02-03 09:14:28","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5930577","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5930577","identity":"rs-5930577","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}