In vitro digestion, physicochemical and structural properties of rice starch dual-treated with radio frequency dry heating and annealing treatment

In vitro digestion, physicochemical and structural properties of rice starch dual-treated with radio frequency dry heating and annealing treatment | 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 In vitro digestion, physicochemical and structural properties of rice starch dual-treated with radio frequency dry heating and annealing treatment Yifei Dong, Xinyu Li, Yan Cui, Liang Zhang, Xiaoting Xuan, Ruiling Lv, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4370667/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 Radio frequency dry heating treatment combined with annealing treatment (RFDHT-ANN) was applied in this study to investigate the effects of the combined treatment on the digestibility, pasting properties, and multiscale structure of rice starch (RS). In practice, the combined modification treatment did not change the crystal type but resulted in a change in the microscopic morphology of RS. The dual treatment improved the amylose content, solubility, particle size, relative crystallinity and gelatinization transition temperature but declined the starch's swelling power. The lowest enzymatic digestibility was found with a decrease of 9.05% of rapidly digestible starch but an increment of 1.69% of slowly digestible starch and 7.38% of resistant starch. Compared with native starch, the characteristic peak of modified starches at 20.2° (2θ) was weakened. Furthermore, the dual treatment noticeably decreased the gelatinating viscosity of RS. This study provides innovative ideas for improving starch-based, slowly digestible foods in the future. Radio frequency dry heating Annealing Rice starch Digestibility Multiscale structure Pasting properties Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction Public awareness of the threat to human health from chronic diseases is growing, so health-promoting foods with low glycemic index (GI) and slow digestibility properties have received an increasing focus. Rice is one of the primary sources of carbohydrates, which is the main energy source in most people’s diets. However, compared to other starchy foods, rice and rice-based foods are easily digested by the human gastrointestinal tract and lead to a high GI, which may increase the risk of diet-related illnesses such as type 2 diabetes and cardiovascular diseases (Miller et al., 1992 ). Therefore, reducing the digestibility rate of food products made of rice is significant for improving health-promoting foods. Starch is the main component of rice, accounting for 60–80% of its mass (Li et al., 2020 ). Academics categorize starch into rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) based on its digestion rate (Zhang et al., 2022 ). SDS and RS can contribute to avoiding the risk of rapid blood glucose elevation caused by continuous glucose release, thereby alleviating the burden on the human body’s blood glucose regulation system (Wang et al., 2014 ). Therefore, controlling the composition of starch by decreasing the content of RDS or improving the content of SDS or RS to reduce the digestibility properties of the starch has attracted more and more attention (Chi et al., 2024 ). Annealing (ANN) is a hydrothermal treatment that improves the thermostability and physicochemical properties of starch. ANN is performed in excessive (> 60%, v/v) or intermediate (~ 40%, v/v) water, at a moderate temperature (among the glass transition temperature and the pasting temperature of starch) (Chen et al., 2022 ). ANN may disrupt the least stable structures of starch, leading to recrystallization or rearrangement of starch molecular chains (Guo et al., 2020 ). ANN can also enhance the gelatinization characteristics of starch (Chi et al., 2019 ), reduce its swelling power and solubility (Yadav et al., 2013 ), and strengthen the microcrystalline structure of starch, making it difficult for enzymes to penetrate and hydrolyze starch internally, thus reducing the rate of starch hydrolysis (Zheng et al., 2023 ). However, the effects of ANN on starch vary depending on the sources. It has noticeable effects on some starches but has significant effects on other starches, possibly due to the interlacing of starch chains and branching starch, which hinders the movement and rearrangement of starch, thus limiting the effectiveness of annealing treatment (Zhong et al., 2020 ). In addition, the rigidity structure of native starch granules may limit the annealing efficiency (Chi et al., 2019 ). Dry heating treatment (DHT) is another environmentally friendly method for starch modification. It can change the physicochemical properties of starch without damaging its granular structure. Zhou et al. ( 2021 ) found that dry heating treatment improved the relative crystallinity, paste properties and solubility of quinoa starch. A reduction in the digestibility of potato starch Zhang et al. ( 2023 ) and dioscorea starch Vashisht et al. ( 2017 ) was found after DHT. Therefore, dry-heating treated starch is expected to achieve better reorganization and rearrangement of the starch structure during the subsequent annealing process, significantly inhabiting the starch hydrolysis. Radiofrequency (RF) heating has advantages such as volumetric heating, deep penetration, high efficiency and suitability for heating low-moisture materials compared to traditional DHT (Dong et al., 2023 ; Liao et al., 2020 ). It has high heating efficiency, and low energy consumption, and is more in line with the concept of energy conservation and emission reduction. RF electromagnetic waves can cause oscillations and migrations of polar molecules in starch, which may change the formation of starch molecular chains, thereby changing the crystallinity structure of starch. Recently, studies have reported that RF energy modified the physicochemical properties and multiscale structure of rice starch (Zhang et al., 2023 ), buckwheat starch (Xu et al., 2023 ) and sweet potato starch (Zhou et al., 2023 ). Chi et al. ( 2019 ) reported that dry heating combined with annealing treatment declined the digestibility while improving the pasting temperature of maize starch and photo starch. The modification effect of single annealing treatment is limited. Zhong et al. ( 2020 ) found that microwave pretreatment with appropriate intensity promoted the effectiveness of annealing treatment, and the combined treatment promoted the physicochemical and structural properties of rice starch. Radio frequency dry heating treatment combined with annealing treatment (RFDHT-ANN) is an environmentally friendly starch modification technology, which has received great acceptance for no chemical reagents use. To our knowledge, there is currently no research on using RFDHT-ANN to regulate the in vitro digestibility of rice starch. We hypothesize that this combined modification can impact the digestion characteristics of rice starch by altering its starch composition and multiscale structure. Based on this, this study aimed to investigate the effects of the combined modification on the digestible properties of rice starch and systematically explore the change of physicochemical properties and multiscale structures of the starch, with the hope of providing innovative ideas for expanding the applications of rice starch and developing starch-based slowly digestible foods in the future. Material and methods Materials Rice starch was purchased from Shanghai Yuanye Bio-Technology Co., Ltd (Shanghai China). Pepsin (CAS: 9001-75-6, 1:15000), pancreatin (CAS:8049-47-6, from porcine pancreas, USP specifications) and amyloglucosidase (CAS: 9032-08-0, 2000 U/mL ~ 3300 U/mL) were purchased from Aladdin Co. (Shanghai, China). The glucose oxidase-peroxidase (GOPOD) kit was purchased from Aladdin Co. (Shanghai, China) to determine glucose content. All other chemical reagents used in this study were of analytical grade. Sample preparation The dually modified (RFDHT-ANN) starch samples were obtained in successive two steps. Firstly, the normal rice starch was heated for 2 h at the 5-kW, 27.12 MHz pilot-scale RF system, and the schematic diagram of the RF system is shown in Fig. 1 . The starch samples after RFDHT were mixed with distilled water (1:6 (w/v)) homogenously in a polypropylene plastic box and sealed using plastic wrap, then subjected to annealing treatment in a drying oven at 55 ℃ for 12 h. Then the mixture was centrifugated (5000 r/min and 20 min). The precipitate was collected and dried using a freeze dryer (Freezone 4.5L, Labconco Corporation, Kansas, MO, USA). Single-modified starches were prepared by RFDHT (RF dry heat at 110 ℃ for 2 h) or annealing treatment (hydrothermal treatment at 55 ℃ for 12 h). The dry heat-treated starch and annealing-treated starch were labeled RS-RFD and RS-A, respectively. The dually modified starch was labeled RS-RFD-A. Particle size distribution The particle size of modified and native rice starch was recorded by using a laser particle size analyzer LS13 320 XR (Beckman Coulter Ltd., America). Each RS sample was dispersed in distilled water at 2 mg/mL concentration. The mixed sample was stirred at room temperature for 30 min, and then measured by the laser particle size analyzer. The value of (D (4,3)) was calculated. Analysis of granular microscopic morphology The microstructure of the native and modified starches was investigated by scanning electron microscopy (SEM) (G300, Zeiss, Germany). The images were collected at an accelerating voltage of 5.0 kV and magnified 1500× and 6000×. Amylose content measurement The amylose content was estimated by using a commercial assay kit (Suzhou Grace Biotechnology Co., Ltd, Suzhou, China). The experimental results were repeated and averaged. Swelling power and solubility Swelling power (SP) and solubility of starches were measured by using the method of Zhang et al. ( 2022 ) and slightly modified. Briefly, accurately weighing 0.1 g of starch sample with a 50 mL centrifuge tube, then recording the total mass (W 1 ) of the sample and centrifuge tube. Afterward, the starch sample was dispersed into 5mL distilled water, and the starch dispersion was heated at different temperatures of 50, 60, 70, 80, and 90 ℃ for 30 min in a water bath with continuous shaking (150 rpm). Finally, the mixture was cooled to room temperature and centrifugated (3500 r/min and 10 min). The supernatant was decanted in a glass tray and tried at 105 ℃ for 8 h, then the total mass (W 2 ) of the centrifuge tube and precipitate. The residue obtained after drying indicates the amount of starch dissolved in water. The SP was calculated using the following equation, SP = \(\frac{{W}_{2}-{W}_{1}}{weight of starch}\) (1) In vitro digestibility The digestibility property of rice starch was measured according to the method of Zhang et al. ( 2022 ) with some modifications. Briefly, starches (300 mg) were added to 20 mL sodium acetate buffer (0.1 mol/L) and boiled water bath for 20 min, to make it gelatinized thoroughly. The gelatinized starch samples were incubated in a water bath at 37 ℃ for 10 min. Then 20 mL of pepsin solution was added to the reaction mixtures and incubated at 37°C for 20 min. Afterwards, 10 mL enzyme mixtures containing pancreatin and amyloglucosidase were added into reaction mixtures, and incubated at 37°C for 120 min. At different intervals (0, 20, and 120 min), hydrolysate (1 mL) was obtained and mixed with 4 mL anhydrous ethanol, followed by centrifugated (5000 g and 15 min). The released glucose content was measured by using a glucose oxidase-peroxidase kit. The fractions of RDS, SDS and RS were recorded according to the glucose content at various time intervals, the equations as follows: RDS (%) =(G 20 -F)×0.9×100/T (2) SDS (%) = (G 120 -G 20 ) ×100/T (3) RS (%) =(1-RDS-SDS)×100 (4) Where F indicates the amount of free glucose; T is the total starch weight; G 20 and G 120 represent the content of glucose released within 20 and 120 min of hydrolysis, respectively. Analysis of the short-range order structures The analysis of short-range order structure was carried out using Fourier transform-infrared spectroscopy (FT-IR) via the KBr pressed disc method. Briefly, the starch sample was mixed with KBr (1/100, w/w), then the mixture was ground thoroughly and then pressed into transparent sheets, and Fourier transform infrared patterns were collected in a darkroom. Acquisition resolution 4 cm − 1 , scan range 400–4000 cm − 1 . The number of sample scans was 32. The spectra were analyzed using Peakfit 4.12 software. The absorbance ratio 1047/1022 (R 1047/1022 ) reflects the changes in starch short-range order structures of rice starch. The intensity ratio of the absorption bands at 1047 cm − 1 and 1022 cm − 1 was measured according to the method of (Zhong et al., 2020 ). Crystalline structure analysis with X-ray diffraction The long-range order structures of starch samples were analyzed with an X-ray diffractometer (mod D8, Bruker Inc., Karlsruhe, Germany). The diffraction profiles were collected in the range from 5° to 40° (2θ). The area of crystalline peaks and amorphous region were analyzed by MDI Jade 6.0. The relative crystallinity (RC) of rice starch samples was measured by using the method of Wu et al. ( 2016 ). Differential scanning calorimetry (DSC) analysis of starch The thermal properties of starch samples were measured by using a differential scanning calorimeter (DSC-1 STARe, Mettler-Toledo). Briefly, starch (3 mg) and distilled water (9 mg) were added to an aluminum crucible. The crucible was sealed and equilibrated (4 ℃, 12 h) to allow the starch to mix well with water. The crucible was scanned from 25 ~ 95°C at a rate of 10°C/min. The gelatinization transition (T 0 , T p , and T c ), and gelatinization enthalpy (ΔH) were calculated by instrument software. Pasting properties The pasting properties of rice starch before and after modification were measured by the rapid viscosity analyzer (TECH MASTER, Perten Instruments, Sweden). The starch samples (3g, dry basis) and distilled water (25 g) were mixed in an aluminum RVA canister to form the dispersion. The specific operation was performed based on the method of (Zhang et al. 2022 ). The gelatinization temperature (GT), peak viscosity (PV), final viscosity (FV), through viscosity (TV), breakdown, setback (SB) and peak time (PT) were recorded. Statistical analysis All data are the mean of triplicate experiments. The results were analyzed using Microsoft Excel software (Microsoft, USA) and MDI Jade 6.0 software (Materials data, USA), and the data were presented as means ± standard deviations. One-way ANOVA was analyzed by IBM SPSS statistical software, version 22.0 (SPSS Inc., Chicago, IL, USA). Statistical significance was set at p < 0.05. Results and discussion Particle size distribution The particle size of RS exhibits a profound correlation with its functional properties, including gelatinization, stability, and gel-forming capabilities (Luo et al., 2021 ). Figure 2 delineates the particle size distribution curves for both native and modified starches, while Table 1 concisely summarizes the volume mean diameter (D (4,3)) for these starch variants. As shown in Fig. 2 and Table 1 , compared with normal RS, the particle size distribution curves of modified starches shifted to the right and the D (4,3) of modified starches noticeably increased compared to the native one, indicating that modification treatment improved the particle size of RS. The possible reason is the action of moisture and thermal energy during annealing treatment (ANN) led to the reorganization of the starch granules, which increased the volume of starch granules. In addition, the partial gelatinization of starch granules and the improvement of amylose and amylopectin interaction during radio frequency dry heating treatment (RFDHT) resulted in the aggregation of starch granules, thereby increasing the particle volume (Hong et al., 2023 ). Prior research has elucidated that variances in particle size precipitate alterations in the digestibility characteristics of starch (Sun et al., 2023 ). An increased particle size diminishes the surface area of starch granules, potentially impeding the enzymatic accessibility of amylase to the starch substrate (Paz-Yépez et al., 2019). The RS-RFD-A had larger particle sizes than those of RS-A and RS-RFD, suggesting that the combined treatment more effectively inhibits starch hydrolysis. Granular microscopic morphology SEM micrographs of the native and modified starches are shown in Fig. 3 . Normal rice starch granules are irregular polyhedrons with sharp edges and angles, and some grooves and fissures are distributed on their surface. These obtained results are consistent with the findings of Zhong et al. ( 2020 ) and Bian & Chung, ( 2016 ). Don’t like native starch, the sharp edges and angles of starch granules were eroded and the starch structure was recombined after ANN. These phenomena indicated that ANN destroyed the micrographs of starch granules, which may be ascribed to the gelatinization of some starch granules during annealing leading to the collapse of the starch structure. What’s more, the likely reason is that sufficient moisture accelerates the rearrangement of starch chains. In contrast, there was no significant change in the surface structure (×1500 and 6000 magnification) of starch after RFDHT, while there were some holes and fissures in the surfaces of starch (×6000 magnification). The appearance of these holes and fissures may be due to the high temperature accelerates the reorganization of amylose and amylopectin, leading to starch granules' collapse (Y.-l. Zhou et al., 2021 ). The combination treatment showed a similar surface structure to the single ANN. The results indicated that the effect of ANN on the microscopic morphology of rice starch granular is more obvious. Amylose content The amylose content (AC) across different samples is concisely summarized in Table 1 . The AC of native starch, RS-A, RS-RFD, and RS-RFD-A were 181.26, 168.60, 202.29 and 187.47 mg/g, respectively. It is noticed that the AC decreased by 7.17% after ANN, which was a significant ( p < 0.05) difference compared with native starch. This outcome aligns with the antecedent observations delineated by (Singh et al. 2011 ). The likely reasons are (1) an enhancement of the perfect crystalline structure; (2) rearrangement of starch chains; and (3) augmented interactions between amylose molecules and between amylose and amylopectin (Hoover & Vasanthan, 1994 ). Conversely, compared with native and RS-A, RS-RFD-A and RS-RFD showed a higher AC. This finding suggests that the impact of RFDHT on the AC of rice starch granules is markedly pronounced during the combined treatment process. The increment of amylose leaching may be ascribed to high temperatures resulting in the degradation of α-1,6 glucose bonds during DHT (Ge et al., 2021 ; G. Liu et al., 2023 ). In addition, electromagnetic irradiation may lead to the oscillatory migration of polar molecules and breaks the linkages (M. Wang et al., 2019 ). Accordingly, starch digestibility is affected by AC. The investigation revealed that starch variants with elevated amylose content exhibit heightened resistance to enzymatic digestion (Oh, Bae, & Lee, 2018 ). Swelling power and solubility The impacts of different temperatures (50–90 ℃) on the solubility and SP of rice starch before and after modification are summarized in Table 2 . It has been observed that the solubility and SP of all starch samples appeared to increase with the increase in temperatures and the highest value was obtained at 90 ℃ (Table 2 ). Elevated temperatures facilitate the disruption of starch granular structures, thereby accelerating the amylose leaching out and promotes the granules swelling (M. Xu et al., 2018 ). At all tested temperatures, the solubility of modified starches was higher than that of native ones. Conversely, the swelling power of the modified starches was observed to be lower in comparison to that of normal rice starch. RS-RFD showed a higher solubility compared with untreated starch, a finding corroborated by the studies conducted by Zhang et al. and Gou et al. (Gou et al., 2019 ; Q. Zhang et al., 2023 ). This enhancement in solubility may be attributed to increased amylose leaching during RFDHT (Table 1 ). ANN led to an improvement in rice starch solubility, a phenomenon that contrasts with the findings of previous studies by Yadav et al. ( 2013 ) and Liu et al. ( 2015 ). One plausible explanation for this discrepancy could be the variation in resources and treatment methodologies employed in these studies. Furthermore, the gelatinization of certain starch fractions during ANN may also contribute to this observed phenomenon. Compared with ANN and RFDHT, the combined treatment showed higher solubility, indicating that RFDHT and ANN had a synergistic effect. On the contrary, modified starches showed a lower SP than native ones. On the one hand, the result may be attributed to the degree of crystalline perfection improved and the enhancement of amylose-amylopectin interaction during ANN (Yadav et al., 2013 ). On the other hand, the SP of starch declined during RFDHT, because high temperature resulted in starch structure rearrangement, thereby enhancing the starch chain interaction, which was ascribed to a decrease in the SP during RFDHT (Ge et al., 2021 ). Compared with the single modified treatment, the dual treatment showed the minimum SP (12.15 g/g) at 90 ℃. The likely reason is that high temperature degrades the α-1,4 and α-1,6 glucose bonds and increases the molecular structures during RFDHT. Subsequently, these modified structures and small components easily were recombined during ANN, thereby regulating the SP of the starch. In vitro digestibility The hydrolysis profiles of native starch, RS-A, RS-RFD, and RS-RFD-A are meticulously illustrated in Fig. 4 . The relative proportion of RDS, SDS and RS are summarized in Table 3 . As depicted in Fig. 4 , the total hydrolysis of all starch samples exhibited an increasing trend as the digestion time extended. All starch samples had the highest hydrolysis rate in the first 20 min, primarily due to the rapid hydrolysis of RDS. This phenomenon contributed to the overall higher hydrolysis rate of the starch samples. The total hydrolysis of native starch reached 70.08% in the first 20 min, which was significantly ( p < 0.05) higher than modified starch. This observation intimates that the modification protocols efficaciously attenuated the susceptibility of amylase to starch. The starch exhibited lower RDS content but higher SDS and RS content after ANN compared with native starch. These outcomes can be ascribed to the enhanced interplay between amylose molecules and/or amylose-amylopectin, coupled with the elevation in perfect crystalline architecture during ANN (Zheng et al., 2023 ). These structural changes make it more challenging for enzymes to penetrate and hydrolyze starch internally (Su et al., 2020 ). RFDHT treatment reduced RDS content and increased RS content when compared to the native starch, suggesting that RFDHT reduces starch's susceptibility to amylase. The higher SR and lower RDS levels observed may be attributed to the rearrangement of starch structure and improved interactions between starch chains during RFDHT (Q. Zhang et al., 2023 ). RS-RFD-A exhibited the lowest RDS content (61.03%), and the highest SDS (14.23%) and RS content (24.74%) among other starch samples. The results suggest that RFDHT-ANN had a synergistic effect on rice starch digestibility, possibly due to the dual treatment's influence on the interaction of starch chains and the subsequent limitation of amylase's accessibility to starch. Based on these findings, it can be conclusively stated that the RFDHT-ANN treatment markedly ( p < 0.05) diminished the in vitro digestibility of rice starch by lowering RDS levels while elevating SDS and RS contents. The combined modification approach demonstrated superior efficacy in attenuating the digestibility attributes of starch compared to singular modification protocols. Changes in short-range orders of starch samples The evaluation of the short-range order structure of starch commonly relies on FT-IR spectroscopy. Furthermore, the absorbance at 1047 cm − 1 corresponds to the crystalline order, while the absorbance at 1022 cm − 1 indicates the presence of amorphous regions in starch, the absorbance ratio can be used to assess the extent of the short-range structure in starch (Gou et al., 2019 ). The FT-IR spectra and R 1047/1022 values of the rice starch before and after modification are displayed in Fig. 5 (A) and Table 1 , respectively. As depicted in Fig. 5 (A), there was no observable appearance or disappearance of distinctive peaks in any of the modified starch samples, and none of the three treatments exhibited a significant ( p < 0.05) alteration in the FT-IR spectral pattern. This suggests that no novel functional groups or covalent bonds were formed in rice starch after modification. However, the ratio of the absorbance at 1050 cm − 1 to that at 1022 cm − 1 exhibited changes in the modified starch samples. As shown in Table 1 , the R 1050/1020 of native starch, RS-A, RS-RFD, and RS-RFD-A were 1.39, 1.30, 1.37, and 1.44, respectively. The R1050/1020 value of RS-A was significantly lower than those of the starch samples ( p < 0.05). These findings contradicted the results reported by Zhong et al. ( 2020 ) and Wang et al. ( 2017 ), who concluded that ANN had no significant impact on the short-range structure of rice starch. The perhaps reason is the variation in resources and treatment methodologies employed in these studies. However, the RFDHT-ANN sample exhibited the highest intensity ratio (1.44), which was significantly higher than that of native starch, RS-A, and RS-RFD. These findings suggest that the combined modification of RFDHT and ANN led to an enhancement in the short-range order structure, surpassing that achieved through individual modification treatments. Crystalline structure The XRD patterns and relative crystallinity (RC) of RS before and after modification are summarized in Fig. 5 (B) and Table 1 , respectively. Normal RS and modified RS had a typical A-type crystallinity structure with primary diffraction peaks at about 15.1°, 17.2°, 18°, 20.2° and 23° (2θ) (Fig. 5 (B)). These results indicated that ANN, RFDHT and the dual treatment did not change the crystal type of rice starch. However, the diffraction intensity was changed after modification treatment, the similar results have been reported by Zhang, et al. ( 2022 )d Liu et al. ( 2015 ). The characteristic peak of modified starches at 20.2° (2θ) was weakened in Fig. 5 (B), a possible explanation is that the effect of moisture and thermal energy destroyed the long-range order structures of rice starch. The RC of native starch, RS-A, RS-RFD and RS-RFD-A were 28.31%, 27.25%, 26.60% and 27.95%, respectively. The analysis of variance showed that there was no significant ( p > 0.05) change in the RC of rice starch before and after modification. However, compared with other starches, RS-RFD showed the lowest RC, the likely reason is the degradation of the crystallinity region or the increment of the amorphous region after RF dry heating (Q. Sun et al., 2014 ). Thermal properties of rice starch samples analysis Thermal properties indicate the thermal stability or denaturation degree of starch. The thermal characteristics of native starch, RS-A, RS-RFD and RS-RFD-A were evaluated by Differential Scanning Calorimetry (Fig. 6 (A)), and the related thermal transition parameters are summarized in Table 1 , respectively. As shown in Fig. 6 (A), the exothermic peak of the modified starch sample shifted to the right relative to the native starch, the result indicated that modification treatment changed the thermal properties of rice starch. The onset (T 0 ), peak (T p ) and conclusion gelatinization temperature (T c ) reflect the gelatin properties of starch. As shown in Table 1 , the starch after modification showed higher values of T 0 , T p and T c than that of native starch, indicating that modification treatment improved the transition temperatures of starch. The results may be ascribed to the interaction of amylose and amylopectin was enhanced during modification treatment, which limited the mobility of the amylopectin chains resulting in increased transition temperatures (T 0 , T p and T c ) (Yadav et al., 2013 ). Compared to the single treatment, the dual treatment significantly increased the transition temperatures of rice starch, indicating that RFDHT with ANN had a synergetic effect. Gelatinization enthalpy (ΔH) indicates the ratio of crystal region to amorphous regions in the double helix structure of starch. The ΔH of native starch, RS-A, RS-RFD and RS-RFD-A were 1.80, 1.29, 1.41 and 1.47, respectively. The ΔH was significantly declined ( p < 0.05) after modification treatment than that of native ones, these results can be due to the partial unwinding in the double helix structure of starch during heating (Q. Zhang et al., 2023 ). However, the synergetic treatment showed a higher ΔH compared with the ANN and RF dry heating treatment. The reason is that the double helix structure that was destroyed by high temperature recombined during subsequent ANN. These observations revealed that the combined treatment had a better effect in improving the thermal stability of starch than the single treatment. Pasting properties The pasting profiles and the pasting parameters of modified and native starches are shown in Fig. 6 (B) and Table 4 , respectively. It is noticed that native and modified rice starches showed noticeably different pasting profiles (Fig. 6 (B)), which indicated that modification treatment changed the pasting properties of RS. As shown in Table 4 , the RS-RFD showed higher pasting viscosities (peak viscosity, final viscosity, trough viscosity, breakdown, and setback) compared with native ones, this is consistent with the previous research on rice starch and quinoa starch modified by DHT (Qiu et al., 2015 ; Zhou et al., 2021 ). Peak viscosity (PV) represents the maximum viscosity, which is related to the degree of swelling of starch granules and leaching of amylose from starch granules (Kong et al., 2015 ; Zheng et al., 2023 ). Final viscosity (FV) represents the viscosity at the cool phase. Compared with normal rice starch (1105.00 cP and 1286.02 cP), the RS-RFD showed a higher PV (1199.67 cP) and FV (1329.33 cP). The increment of PV might be ascribed to the higher amylose content after RFDHT. In addition, the increment of FV at the cooling phase may be due to the aggregation of amylose molecules (Zhou et al., 2021 ). After ANN and the combined treatment, the PV (609.00 and 562.00 cP) and FV (866.34 and 797.67) of starch significantly declined than that of native one, which may be attributed to the swelling and the amylose leaching of starch granules were resisted during ANN. Interestingly, RS-RFD-A had the lowest PV, indicating the combination of RFDHT and ANN had a better effect on starch thermal ability improvement. Through viscosity (TV) is the lowest viscosity at the end heating phase (Sharma et al., 2013 ). The results indicated that the TV of RS-RFD increased than that of the native one, but ANN and the dual treatment significantly ( p < 0.05) declined the TV. The increment of TV may be due to the starch granules destroyed during RFDHT. Breakdown (BD) represents the difference between peak viscosity and through viscosity and reflects the shear resistance of the starch (Xu et al., 2018 ). Setback (SB) reflects the tendency of paste to retrograde during the cool phase (Li et al., 2016 ), which is the difference between final viscosity and through viscosity. As shown in Table 4 , RS-RFD showed higher BD and SB than the native counterpart, which can be attributed to the weakening of the ordered structure of the starch, leading to the starch granules being easily destroyed. Compared to other starch samples, RS-RFD-A showed the lowest BD and SB, this result indicated that the dually treated starch had more resistance to shearing and that it had higher pasting stability. After modifying treatment, the peak time (PT) and gelatinization temperature (GT) did not significantly ( p > 0.05) change among native starch and modification-treated starches. However, compared with normal rice starch and RS-RFD, the GT of RS-RFD-A improved, indicating that the temperature required for starch gelatinization increased after the combined treatment. This may be due to the enhancement of amylose-amylopectin and/or amylose-amylopectin interactions during the combined treatment, which caused the starch more difficult to be gelatinized. Above all, the lower paste viscosity and higher pasting temperature of RFDHT combined annealing treated starch samples indicated that the starch granule structures were strengthened and the enhancement of intra-molecular bonding ability, which caused the increment in pasting stability of the dually treated-starch sample. Conclusions The study investigated the impacts of the combination of RFDHT and ANN on the digestible properties, physicochemical properties and multiscale structure of RS. The combined modification significantly decreased the SP but increased the particle size, solubility and AC of the starch. In addition, the combination treatment showed the lowest enzymatic digestibility by decreasing the content of RDS but increasing the content of SDS and RS. Compared with single modified treatment, the dual treatment conspicuously reduced the pasting viscosities but improved the gelatinization transition temperature, thereby significantly improving the gelatinization and thermal stability of the starch. The combination treatment of RFDHT and ANN has been proven with potential to limit the enzymatic digestibility of RS. Further, the dually modified RS can be combined with rice flour or other cereal flour to develop starch-based slowly digestible foods in the future. Declarations Conflicts of Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Contributions Yifei Dong: Investigation, Data curation, Writing original draft; Xinyu Li: Resources, Methodology; Yan Cui: Resources, Methodology; Liang Zhang: Resources, Methodology; Xiaoting Xuan: Resources, Methodology; Ruiling Lv: Resources, Methodology; Xingquan Liu: Resources, Methodology; Jiangang Ling: Supervision, Resources, Project administration, Writing - review & editing; Suhong Li: Supervision, Resources, Project administration, Writing - review & editing. Funding This study was supported by the Science and Technology Innovation 2025 Major Project of Ningbo (No.2022Z182). References Bian, L., & Chung, H.-J. (2016). Molecular structure and physicochemical properties of starch isolated from hydrothermally treated brown rice flour. Food Hydrocolloids, 60 , 345-352. doi: https://doi.org/10.1016/j.foodhyd.2016.04.008 Chen, X., Zhang, Z., Ji, N., Li, M., Wang, Y., Xiong, L., & Sun, Q. (2022). 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Food Hydrocolloids, 113 , 106532. doi: https://doi.org/10.1016/j.foodhyd.2020.106532 Tables Table 1 Particle distribution, AC, short-range ordered degree (R 1047/1022 ) and thermal parameters of the native and modified RS. Sample D (4,3) (nm) AC (mg/g) R 1050/1020 T 0 (℃) T p (℃) T c (℃) ΔH (J/g) Native 1406.00 ± 81.65 c 181.26 ± 1.90 bc 1.39 ± 0.00 ab 63.12 ± 0.33 ab 66.77 ± 0.75 b 73.08 ± 0.07 b 1.80 ± 0.11 a RS-A 1901.00 ± 126.58 bc 168.60 ± 14.22 c 1.30 ± 0.02 a 64.59 ± 3.15 ab 68.81 ± 1.39 ab 73.83 ± 0.20 ab 1.29 ± 0.17 b RS-RFD 2367.33 ± 458.12 ab 202.29 ± 7.69 a 1.37 ± 0.04 ab 61.19 ± 1.00 b 67.21 ± 3.00 ab 72.46 ± 2.63 b 1.41 ± 0.14 b RS-RFD-A 2797.50 ± 392.31 a 187.47 ± 4.14 ab 1.44 ± 0.02 a 67.37 ± 2.80 a 71.38 ± 2.08 a 75.17 ± 1.83 a 1.47 ± 0.05 ab Values are means (±SD) of triplicate samples. a-c The same letter in one column means no significant difference ( p > 0.05). Table 2 The SP and solubility of the native and modified RS Sample Solubility (%) SP (g/g) 50 60 70 80 90 50 60 70 80 90 Native 2.78 ± 0.46 Cb 2.86 ± 0.16 Cb 4.13 ± 0.89 Cb 6.30 ± 0.46 ABba 8.09 ± 1.79 Ba 3.52 ± 0.39 Ad 6.12 ± 0.27 Ac 7.41 ± 0.19 Ac 10.16 ± 0.40 Ab 15.82 ± 1.53 Aa RS-A 3.44 ± 0.68 BCd 4.48 ± 0.69 Acd 5.39 ± 0.36 Bbc 6.73 ± 0.21 ABb 9.47 ± 0.96 Ba 2.56 ± 0.11 Be 5.45 ± 0.20 BCd 7.45 ± 0.11 Ac 8.78 ± 0.07 Bb 14.19 ± 0.45 Aba RS-RFD 4.17 ± 0.05 ABc 5.07 ± 0.32 Bc 5.40 ± 1.01 Bbc 7.04 ± 1.28 ABb 10.47 ± 0.80 Ba 2.03 ± 0.07 Bd 5.87 ± 0.27 Abc 6.70 ± 0.91 Ac 8.81 ± 0.68 Bb 13.93 ± 0.68 Aba RS-RFD-A 4.77 ± 0.41 Ac 7.06 ± 0.44 Ab 7.67 ± 0.98 Ab 8.13 ± 0.31 Ab 14.79 ± 0.44 Aa 1.93 ± 0.50 Be 4.91 ± 0.32 Cd 6.82 ± 0.29 Ac 8.38 ± 0.60 Bb 12.15 ± 0.54 Ba Values are means (±SD) of triplicate samples. a-e The same letter in one row means no significant difference ( p > 0.05); A-C The same letter in one column means no significant difference ( p > 0.05). Table 3 The content of RDS, SDS and RS in native and modified RS Sample RDS (%) SDS (%) RS (%) Native 70.08% ± 2.26 a 12.54% ± 2.34 b 17.38% ± 4.50 b RS-A 67.14% ± 1.05 ab 13.11% ± 1.32 ab 19.74% ± 2.36 ab RS-RFD 65.19% ± 0.84 bc 12.61% ± 1.31 b 22.20% ± 1.29 ab RS-RFD-A 61.03% ± 2.68 c 14.23% ± 3.92 a 24.74% ± 1.7 a Values are means (±SD) of triplicate samples. a-c The same letter in one column means no significant difference ( p > 0.05). Table 4 Pasting parameters of the native and modified RS Sample PV/cP TV/cP BD/cP FV/cP SB/cP PT/min GT/℃ Native 1105.00 ± 16.97 b 901.33 ± 8.26 a 203.67 ± 8.73 b 1286.02 ± 7.12 a 384.67 ± 1.70 a 6.89 ± 0.03 a 94.55 ± 0.05 a RS-A 609.00 ± 3.56 c 583.33 ± 6.65 b 25.67 ± 5.72 d 866.34 ± 23.72 b 282.67 ± 29.10 b 6.67 ± 0.11 a 94.57 ± 0.09 a RS-RFD 1199.67 ± 31.85 a 932.67 ± 31.98 a 267.01 ± 6.38 a 1329.33 ± 87.95 a 396.67 ± 57.04 a 6.80 ± 0.14 a 94.55 ± 0.28 a RS-RFD-A 562.00 ± 4.08 c 505.33 ± 17.91 c 56.67 ± 14.06 c 797.67 ± 52.95 b 292.33 ± 70.71 b 6.49 ± 0.22 a 94.72 ± 0.24 a Values are means (±SD) of triplicate samples. a-d The same letter in one column means no significant difference ( p > 0.05). Additional Declarations No competing interests reported. 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2","display":"","copyAsset":false,"role":"figure","size":63927,"visible":true,"origin":"","legend":"\u003cp\u003eParticle size distribution of the native and modified RS\u003c/p\u003e","description":"","filename":"Onlinefloatimage2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4370667/v1/7dd9217b2df5cc91dfbe231a.jpg"},{"id":56246663,"identity":"e2406cb1-d8f2-438d-8d35-8a7d132ee9c8","added_by":"auto","created_at":"2024-05-10 11:17:06","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":528381,"visible":true,"origin":"","legend":"\u003cp\u003eScanning electron microscopy (SEM) images (at × 1500 and × 6000 magnification) of the native and modified RS\u003c/p\u003e","description":"","filename":"Onlinefloatimage3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4370667/v1/a649b2476b75a486d0985ab2.jpg"},{"id":56246551,"identity":"d0b6f2ad-618b-49ec-8914-f9921a1dc393","added_by":"auto","created_at":"2024-05-10 11:16:59","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":56570,"visible":true,"origin":"","legend":"\u003cp\u003eThe total hydrolysis curves of the native and modified RS\u003c/p\u003e","description":"","filename":"Onlinefloatimage4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4370667/v1/669008bc0c0301567329aad8.jpg"},{"id":56246554,"identity":"655b0f6c-6eae-431d-a32e-30c79d89254d","added_by":"auto","created_at":"2024-05-10 11:16:59","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":602834,"visible":true,"origin":"","legend":"\u003cp\u003eThe FT-IR spectra (A) and X-ray diffraction patterns and relative crystallinity (B) of the native and modified RS\u003c/p\u003e","description":"","filename":"Onlinefloatimage5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4370667/v1/3f77fd60a8e25ff3917bb2f8.jpg"},{"id":56246562,"identity":"2da4384e-31e4-46a9-a51c-9632d63e48fb","added_by":"auto","created_at":"2024-05-10 11:17:01","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":474419,"visible":true,"origin":"","legend":"\u003cp\u003eThermal properties (A) and pasting profiles (B) of the native and modified RS\u003c/p\u003e","description":"","filename":"Onlinefloatimage6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4370667/v1/6246fffe08e4b91aa55cc04d.jpg"},{"id":58252952,"identity":"6df6a66d-0f66-4e2b-a9c1-0391c1e4d14b","added_by":"auto","created_at":"2024-06-13 04:07:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2618634,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4370667/v1/5d0410ba-1214-49e0-9fd6-eda59737cd0c.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"In vitro digestion, physicochemical and structural properties of rice starch dual-treated with radio frequency dry heating and annealing treatment","fulltext":[{"header":"Introduction","content":"\u003cp\u003ePublic awareness of the threat to human health from chronic diseases is growing, so health-promoting foods with low glycemic index (GI) and slow digestibility properties have received an increasing focus. Rice is one of the primary sources of carbohydrates, which is the main energy source in most people\u0026rsquo;s diets. However, compared to other starchy foods, rice and rice-based foods are easily digested by the human gastrointestinal tract and lead to a high GI, which may increase the risk of diet-related illnesses such as type 2 diabetes and cardiovascular diseases (Miller et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1992\u003c/span\u003e). Therefore, reducing the digestibility rate of food products made of rice is significant for improving health-promoting foods. Starch is the main component of rice, accounting for 60\u0026ndash;80% of its mass (Li et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Academics categorize starch into rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) based on its digestion rate (Zhang et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). SDS and RS can contribute to avoiding the risk of rapid blood glucose elevation caused by continuous glucose release, thereby alleviating the burden on the human body\u0026rsquo;s blood glucose regulation system (Wang et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Therefore, controlling the composition of starch by decreasing the content of RDS or improving the content of SDS or RS to reduce the digestibility properties of the starch has attracted more and more attention (Chi et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAnnealing (ANN) is a hydrothermal treatment that improves the thermostability and physicochemical properties of starch. ANN is performed in excessive (\u0026gt;\u0026thinsp;60%, v/v) or intermediate (~\u0026thinsp;40%, v/v) water, at a moderate temperature (among the glass transition temperature and the pasting temperature of starch) (Chen et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). ANN may disrupt the least stable structures of starch, leading to recrystallization or rearrangement of starch molecular chains (Guo et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). ANN can also enhance the gelatinization characteristics of starch (Chi et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), reduce its swelling power and solubility (Yadav et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2013\u003c/span\u003e), and strengthen the microcrystalline structure of starch, making it difficult for enzymes to penetrate and hydrolyze starch internally, thus reducing the rate of starch hydrolysis (Zheng et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). However, the effects of ANN on starch vary depending on the sources. It has noticeable effects on some starches but has significant effects on other starches, possibly due to the interlacing of starch chains and branching starch, which hinders the movement and rearrangement of starch, thus limiting the effectiveness of annealing treatment (Zhong et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). In addition, the rigidity structure of native starch granules may limit the annealing efficiency (Chi et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDry heating treatment (DHT) is another environmentally friendly method for starch modification. It can change the physicochemical properties of starch without damaging its granular structure. Zhou et al. (\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) found that dry heating treatment improved the relative crystallinity, paste properties and solubility of quinoa starch. A reduction in the digestibility of potato starch Zhang et al. (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) and dioscorea starch Vashisht et al. (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) was found after DHT. Therefore, dry-heating treated starch is expected to achieve better reorganization and rearrangement of the starch structure during the subsequent annealing process, significantly inhabiting the starch hydrolysis. Radiofrequency (RF) heating has advantages such as volumetric heating, deep penetration, high efficiency and suitability for heating low-moisture materials compared to traditional DHT (Dong et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Liao et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). It has high heating efficiency, and low energy consumption, and is more in line with the concept of energy conservation and emission reduction. RF electromagnetic waves can cause oscillations and migrations of polar molecules in starch, which may change the formation of starch molecular chains, thereby changing the crystallinity structure of starch. Recently, studies have reported that RF energy modified the physicochemical properties and multiscale structure of rice starch (Zhang et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), buckwheat starch (Xu et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) and sweet potato starch (Zhou et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eChi et al. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) reported that dry heating combined with annealing treatment declined the digestibility while improving the pasting temperature of maize starch and photo starch. The modification effect of single annealing treatment is limited. Zhong et al. (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) found that microwave pretreatment with appropriate intensity promoted the effectiveness of annealing treatment, and the combined treatment promoted the physicochemical and structural properties of rice starch. Radio frequency dry heating treatment combined with annealing treatment (RFDHT-ANN) is an environmentally friendly starch modification technology, which has received great acceptance for no chemical reagents use. To our knowledge, there is currently no research on using RFDHT-ANN to regulate the in vitro digestibility of rice starch. We hypothesize that this combined modification can impact the digestion characteristics of rice starch by altering its starch composition and multiscale structure. Based on this, this study aimed to investigate the effects of the combined modification on the digestible properties of rice starch and systematically explore the change of physicochemical properties and multiscale structures of the starch, with the hope of providing innovative ideas for expanding the applications of rice starch and developing starch-based slowly digestible foods in the future.\u003c/p\u003e"},{"header":"Material and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003eMaterials\u003c/h2\u003e\n \u003cp\u003eRice starch was purchased from Shanghai Yuanye Bio-Technology Co., Ltd (Shanghai China). Pepsin (CAS: 9001-75-6, 1:15000), pancreatin (CAS:8049-47-6, from porcine pancreas, USP specifications) and amyloglucosidase (CAS: 9032-08-0, 2000 U/mL\u0026thinsp;~\u0026thinsp;3300 U/mL) were purchased from Aladdin Co. (Shanghai, China). The glucose oxidase-peroxidase (GOPOD) kit was purchased from Aladdin Co. (Shanghai, China) to determine glucose content. All other chemical reagents used in this study were of analytical grade.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003eSample preparation\u003c/h2\u003e\n \u003cp\u003eThe dually modified (RFDHT-ANN) starch samples were obtained in successive two steps. Firstly, the normal rice starch was heated for 2 h at the 5-kW, 27.12 MHz pilot-scale RF system, and the schematic diagram of the RF system is shown in Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. The starch samples after RFDHT were mixed with distilled water (1:6 (w/v)) homogenously in a polypropylene plastic box and sealed using plastic wrap, then subjected to annealing treatment in a drying oven at 55 ℃ for 12 h. Then the mixture was centrifugated (5000 r/min and 20 min). The precipitate was collected and dried using a freeze dryer (Freezone 4.5L, Labconco Corporation, Kansas, MO, USA). Single-modified starches were prepared by RFDHT (RF dry heat at 110 ℃ for 2 h) or annealing treatment (hydrothermal treatment at 55 ℃ for 12 h). The dry heat-treated starch and annealing-treated starch were labeled RS-RFD and RS-A, respectively. The dually modified starch was labeled RS-RFD-A.\u003c/p\u003e\n \u003cdiv id=\"Sec5\" class=\"Section3\"\u003e\n \u003ch2\u003eParticle size distribution\u003c/h2\u003e\n \u003cp\u003eThe particle size of modified and native rice starch was recorded by using a laser particle size analyzer LS13 320 XR (Beckman Coulter Ltd., America). Each RS sample was dispersed in distilled water at 2 mg/mL concentration. The mixed sample was stirred at room temperature for 30 min, and then measured by the laser particle size analyzer. The value of (D (4,3)) was calculated.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003eAnalysis of granular microscopic morphology\u003c/h2\u003e\n \u003cp\u003eThe microstructure of the native and modified starches was investigated by scanning electron microscopy (SEM) (G300, Zeiss, Germany). The images were collected at an accelerating voltage of 5.0 kV and magnified 1500\u0026times; and 6000\u0026times;.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003eAmylose content measurement\u003c/h2\u003e\n \u003cp\u003eThe amylose content was estimated by using a commercial assay kit (Suzhou Grace Biotechnology Co., Ltd, Suzhou, China). The experimental results were repeated and averaged.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003eSwelling power and solubility\u003c/h2\u003e\n \u003cp\u003eSwelling power (SP) and solubility of starches were measured by using the method of Zhang et al. (\u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e) and slightly modified. Briefly, accurately weighing 0.1 g of starch sample with a 50 mL centrifuge tube, then recording the total mass (W\u003csub\u003e1\u003c/sub\u003e) of the sample and centrifuge tube. Afterward, the starch sample was dispersed into 5mL distilled water, and the starch dispersion was heated at different temperatures of 50, 60, 70, 80, and 90 ℃ for 30 min in a water bath with continuous shaking (150 rpm). Finally, the mixture was cooled to room temperature and centrifugated (3500 r/min and 10 min). The supernatant was decanted in a glass tray and tried at 105 ℃ for 8 h, then the total mass (W\u003csub\u003e2\u003c/sub\u003e) of the centrifuge tube and precipitate. The residue obtained after drying indicates the amount of starch dissolved in water. The SP was calculated using the following equation,\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003cp\u003eSP = \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\frac{{W}_{2}-{W}_{1}}{weight of starch}\\)\u003c/span\u003e\u003c/span\u003e (1)\u003c/p\u003e\n \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\n \u003ch2\u003eIn vitro digestibility\u003c/h2\u003e\n \u003cp\u003eThe digestibility property of rice starch was measured according to the method of Zhang et al. (\u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e) with some modifications. Briefly, starches (300 mg) were added to 20 mL sodium acetate buffer (0.1 mol/L) and boiled water bath for 20 min, to make it gelatinized thoroughly. The gelatinized starch samples were incubated in a water bath at 37 ℃ for 10 min. Then 20 mL of pepsin solution was added to the reaction mixtures and incubated at 37\u0026deg;C for 20 min. Afterwards, 10 mL enzyme mixtures containing pancreatin and amyloglucosidase were added into reaction mixtures, and incubated at 37\u0026deg;C for 120 min. At different intervals (0, 20, and 120 min), hydrolysate (1 mL) was obtained and mixed with 4 mL anhydrous ethanol, followed by centrifugated (5000 g and 15 min). The released glucose content was measured by using a glucose oxidase-peroxidase kit. The fractions of RDS, SDS and RS were recorded according to the glucose content at various time intervals, the equations as follows:\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003cp\u003eRDS (%) =(G\u003csub\u003e20\u003c/sub\u003e-F)\u0026times;0.9\u0026times;100/T (2)\u003c/p\u003e\n \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\n \u003cp\u003eSDS (%) = (G\u003csub\u003e120\u003c/sub\u003e-G\u003csub\u003e20\u003c/sub\u003e) \u0026times;100/T (3)\u003c/p\u003e\n \u003cdiv id=\"Sec13\" class=\"Section4\"\u003e\n \u003cp\u003eRS (%) =(1-RDS-SDS)\u0026times;100 (4)\u003c/p\u003e\n \u003cp\u003eWhere F indicates the amount of free glucose; T is the total starch weight; G\u003csub\u003e20\u003c/sub\u003e and G\u003csub\u003e120\u003c/sub\u003e represent the content of glucose released within 20 and 120 min of hydrolysis, respectively.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\n \u003ch2\u003eAnalysis of the short-range order structures\u003c/h2\u003e\n \u003cp\u003eThe analysis of short-range order structure was carried out using Fourier transform-infrared spectroscopy (FT-IR) via the KBr pressed disc method. Briefly, the starch sample was mixed with KBr (1/100, w/w), then the mixture was ground thoroughly and then pressed into transparent sheets, and Fourier transform infrared patterns were collected in a darkroom. Acquisition resolution 4 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, scan range 400\u0026ndash;4000 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The number of sample scans was 32. The spectra were analyzed using Peakfit 4.12 software. The absorbance ratio 1047/1022 (R\u003csub\u003e1047/1022\u003c/sub\u003e) reflects the changes in starch short-range order structures of rice starch. The intensity ratio of the absorption bands at 1047 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1022 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was measured according to the method of (Zhong et al., \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\n \u003ch2\u003eCrystalline structure analysis with X-ray diffraction\u003c/h2\u003e\n \u003cp\u003eThe long-range order structures of starch samples were analyzed with an X-ray diffractometer (mod D8, Bruker Inc., Karlsruhe, Germany). The diffraction profiles were collected in the range from 5\u0026deg; to 40\u0026deg; (2\u0026theta;). The area of crystalline peaks and amorphous region were analyzed by MDI Jade 6.0. The relative crystallinity (RC) of rice starch samples was measured by using the method of Wu et al. (\u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\n \u003ch2\u003eDifferential scanning calorimetry (DSC) analysis of starch\u003c/h2\u003e\n \u003cp\u003eThe thermal properties of starch samples were measured by using a differential scanning calorimeter (DSC-1 STARe, Mettler-Toledo). Briefly, starch (3 mg) and distilled water (9 mg) were added to an aluminum crucible. The crucible was sealed and equilibrated (4 ℃, 12 h) to allow the starch to mix well with water. The crucible was scanned from 25\u0026thinsp;~\u0026thinsp;95\u0026deg;C at a rate of 10\u0026deg;C/min. The gelatinization transition (T\u003csub\u003e0\u003c/sub\u003e, T\u003csub\u003ep\u003c/sub\u003e, and T\u003csub\u003ec\u003c/sub\u003e), and gelatinization enthalpy (\u0026Delta;H) were calculated by instrument software.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\n \u003ch2\u003ePasting properties\u003c/h2\u003e\n \u003cp\u003eThe pasting properties of rice starch before and after modification were measured by the rapid viscosity analyzer (TECH MASTER, Perten Instruments, Sweden). The starch samples (3g, dry basis) and distilled water (25 g) were mixed in an aluminum RVA canister to form the dispersion. The specific operation was performed based on the method of (Zhang et al. \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e). The gelatinization temperature (GT), peak viscosity (PV), final viscosity (FV), through viscosity (TV), breakdown, setback (SB) and peak time (PT) were recorded.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\n \u003ch2\u003eStatistical analysis\u003c/h2\u003e\n \u003cp\u003eAll data are the mean of triplicate experiments. The results were analyzed using Microsoft Excel software (Microsoft, USA) and MDI Jade 6.0 software (Materials data, USA), and the data were presented as means\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviations. One-way ANOVA was analyzed by IBM SPSS statistical software, version 22.0 (SPSS Inc., Chicago, IL, USA). Statistical significance was set at \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Results and discussion","content":"\u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003eParticle size distribution\u003c/h2\u003e \u003cp\u003eThe particle size of RS exhibits a profound correlation with its functional properties, including gelatinization, stability, and gel-forming capabilities (Luo et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e delineates the particle size distribution curves for both native and modified starches, while Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e concisely summarizes the volume mean diameter (D (4,3)) for these starch variants. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, compared with normal RS, the particle size distribution curves of modified starches shifted to the right and the D (4,3) of modified starches noticeably increased compared to the native one, indicating that modification treatment improved the particle size of RS. The possible reason is the action of moisture and thermal energy during annealing treatment (ANN) led to the reorganization of the starch granules, which increased the volume of starch granules. In addition, the partial gelatinization of starch granules and the improvement of amylose and amylopectin interaction during radio frequency dry heating treatment (RFDHT) resulted in the aggregation of starch granules, thereby increasing the particle volume (Hong et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Prior research has elucidated that variances in particle size precipitate alterations in the digestibility characteristics of starch (Sun et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). An increased particle size diminishes the surface area of starch granules, potentially impeding the enzymatic accessibility of amylase to the starch substrate (Paz-Y\u0026eacute;pez et al., 2019). The RS-RFD-A had larger particle sizes than those of RS-A and RS-RFD, suggesting that the combined treatment more effectively inhibits starch hydrolysis.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003eGranular microscopic morphology\u003c/h2\u003e \u003cp\u003eSEM micrographs of the native and modified starches are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Normal rice starch granules are irregular polyhedrons with sharp edges and angles, and some grooves and fissures are distributed on their surface. These obtained results are consistent with the findings of Zhong et al. (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) and Bian \u0026amp; Chung, (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eDon\u0026rsquo;t like native starch, the sharp edges and angles of starch granules were eroded and the starch structure was recombined after ANN. These phenomena indicated that ANN destroyed the micrographs of starch granules, which may be ascribed to the gelatinization of some starch granules during annealing leading to the collapse of the starch structure. What\u0026rsquo;s more, the likely reason is that sufficient moisture accelerates the rearrangement of starch chains. In contrast, there was no significant change in the surface structure (\u0026times;1500 and 6000 magnification) of starch after RFDHT, while there were some holes and fissures in the surfaces of starch (\u0026times;6000 magnification). The appearance of these holes and fissures may be due to the high temperature accelerates the reorganization of amylose and amylopectin, leading to starch granules' collapse (Y.-l. Zhou et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The combination treatment showed a similar surface structure to the single ANN. The results indicated that the effect of ANN on the microscopic morphology of rice starch granular is more obvious.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec22\" class=\"Section2\"\u003e \u003ch2\u003eAmylose content\u003c/h2\u003e \u003cp\u003eThe amylose content (AC) across different samples is concisely summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The AC of native starch, RS-A, RS-RFD, and RS-RFD-A were 181.26, 168.60, 202.29 and 187.47 mg/g, respectively. It is noticed that the AC decreased by 7.17% after ANN, which was a significant (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) difference compared with native starch. This outcome aligns with the antecedent observations delineated by (Singh et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). The likely reasons are (1) an enhancement of the perfect crystalline structure; (2) rearrangement of starch chains; and (3) augmented interactions between amylose molecules and between amylose and amylopectin (Hoover \u0026amp; Vasanthan, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e1994\u003c/span\u003e). Conversely, compared with native and RS-A, RS-RFD-A and RS-RFD showed a higher AC. This finding suggests that the impact of RFDHT on the AC of rice starch granules is markedly pronounced during the combined treatment process. The increment of amylose leaching may be ascribed to high temperatures resulting in the degradation of α-1,6 glucose bonds during DHT (Ge et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; G. Liu et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). In addition, electromagnetic irradiation may lead to the oscillatory migration of polar molecules and breaks the linkages (M. Wang et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Accordingly, starch digestibility is affected by AC. The investigation revealed that starch variants with elevated amylose content exhibit heightened resistance to enzymatic digestion (Oh, Bae, \u0026amp; Lee, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e \u003cdiv id=\"Sec23\" class=\"Section3\"\u003e \u003ch2\u003eSwelling power and solubility\u003c/h2\u003e \u003cp\u003eThe impacts of different temperatures (50\u0026ndash;90 ℃) on the solubility and SP of rice starch before and after modification are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. It has been observed that the solubility and SP of all starch samples appeared to increase with the increase in temperatures and the highest value was obtained at 90 ℃ (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Elevated temperatures facilitate the disruption of starch granular structures, thereby accelerating the amylose leaching out and promotes the granules swelling (M. Xu et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). At all tested temperatures, the solubility of modified starches was higher than that of native ones. Conversely, the swelling power of the modified starches was observed to be lower in comparison to that of normal rice starch.\u003c/p\u003e \u003cp\u003eRS-RFD showed a higher solubility compared with untreated starch, a finding corroborated by the studies conducted by Zhang et al. and Gou et al. (Gou et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Q. Zhang et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). This enhancement in solubility may be attributed to increased amylose leaching during RFDHT (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). ANN led to an improvement in rice starch solubility, a phenomenon that contrasts with the findings of previous studies by Yadav et al. (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) and Liu et al. (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). One plausible explanation for this discrepancy could be the variation in resources and treatment methodologies employed in these studies. Furthermore, the gelatinization of certain starch fractions during ANN may also contribute to this observed phenomenon. Compared with ANN and RFDHT, the combined treatment showed higher solubility, indicating that RFDHT and ANN had a synergistic effect.\u003c/p\u003e \u003cp\u003eOn the contrary, modified starches showed a lower SP than native ones. On the one hand, the result may be attributed to the degree of crystalline perfection improved and the enhancement of amylose-amylopectin interaction during ANN (Yadav et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). On the other hand, the SP of starch declined during RFDHT, because high temperature resulted in starch structure rearrangement, thereby enhancing the starch chain interaction, which was ascribed to a decrease in the SP during RFDHT (Ge et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Compared with the single modified treatment, the dual treatment showed the minimum SP (12.15 g/g) at 90 ℃. The likely reason is that high temperature degrades the α-1,4 and α-1,6 glucose bonds and increases the molecular structures during RFDHT. Subsequently, these modified structures and small components easily were recombined during ANN, thereby regulating the SP of the starch.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec24\" class=\"Section2\"\u003e \u003ch2\u003eIn vitro digestibility\u003c/h2\u003e \u003cp\u003eThe hydrolysis profiles of native starch, RS-A, RS-RFD, and RS-RFD-A are meticulously illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The relative proportion of RDS, SDS and RS are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. As depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, the total hydrolysis of all starch samples exhibited an increasing trend as the digestion time extended. All starch samples had the highest hydrolysis rate in the first 20 min, primarily due to the rapid hydrolysis of RDS. This phenomenon contributed to the overall higher hydrolysis rate of the starch samples. The total hydrolysis of native starch reached 70.08% in the first 20 min, which was significantly (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) higher than modified starch. This observation intimates that the modification protocols efficaciously attenuated the susceptibility of amylase to starch.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe starch exhibited lower RDS content but higher SDS and RS content after ANN compared with native starch. These outcomes can be ascribed to the enhanced interplay between amylose molecules and/or amylose-amylopectin, coupled with the elevation in perfect crystalline architecture during ANN (Zheng et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). These structural changes make it more challenging for enzymes to penetrate and hydrolyze starch internally (Su et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). RFDHT treatment reduced RDS content and increased RS content when compared to the native starch, suggesting that RFDHT reduces starch's susceptibility to amylase. The higher SR and lower RDS levels observed may be attributed to the rearrangement of starch structure and improved interactions between starch chains during RFDHT (Q. Zhang et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). RS-RFD-A exhibited the lowest RDS content (61.03%), and the highest SDS (14.23%) and RS content (24.74%) among other starch samples. The results suggest that RFDHT-ANN had a synergistic effect on rice starch digestibility, possibly due to the dual treatment's influence on the interaction of starch chains and the subsequent limitation of amylase's accessibility to starch.\u003c/p\u003e \u003cp\u003eBased on these findings, it can be conclusively stated that the RFDHT-ANN treatment markedly (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) diminished the in vitro digestibility of rice starch by lowering RDS levels while elevating SDS and RS contents. The combined modification approach demonstrated superior efficacy in attenuating the digestibility attributes of starch compared to singular modification protocols.\u003c/p\u003e \u003cdiv id=\"Sec25\" class=\"Section3\"\u003e \u003ch2\u003eChanges in short-range orders of starch samples\u003c/h2\u003e \u003cp\u003eThe evaluation of the short-range order structure of starch commonly relies on FT-IR spectroscopy. Furthermore, the absorbance at 1047 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to the crystalline order, while the absorbance at 1022 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e indicates the presence of amorphous regions in starch, the absorbance ratio can be used to assess the extent of the short-range structure in starch (Gou et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The FT-IR spectra and R\u003csub\u003e1047/1022\u003c/sub\u003e values of the rice starch before and after modification are displayed in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e (A) and Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, respectively. As depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e (A), there was no observable appearance or disappearance of distinctive peaks in any of the modified starch samples, and none of the three treatments exhibited a significant (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) alteration in the FT-IR spectral pattern. This suggests that no novel functional groups or covalent bonds were formed in rice starch after modification. However, the ratio of the absorbance at 1050 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to that at 1022 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e exhibited changes in the modified starch samples.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, the R\u003csub\u003e1050/1020\u003c/sub\u003e of native starch, RS-A, RS-RFD, and RS-RFD-A were 1.39, 1.30, 1.37, and 1.44, respectively. The R1050/1020 value of RS-A was significantly lower than those of the starch samples (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). These findings contradicted the results reported by Zhong et al. (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) and Wang et al. (\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), who concluded that ANN had no significant impact on the short-range structure of rice starch. The perhaps reason is the variation in resources and treatment methodologies employed in these studies. However, the RFDHT-ANN sample exhibited the highest intensity ratio (1.44), which was significantly higher than that of native starch, RS-A, and RS-RFD. These findings suggest that the combined modification of RFDHT and ANN led to an enhancement in the short-range order structure, surpassing that achieved through individual modification treatments.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec26\" class=\"Section3\"\u003e \u003ch2\u003eCrystalline structure\u003c/h2\u003e \u003cp\u003eThe XRD patterns and relative crystallinity (RC) of RS before and after modification are summarized in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e (B) and Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, respectively. Normal RS and modified RS had a typical A-type crystallinity structure with primary diffraction peaks at about 15.1\u0026deg;, 17.2\u0026deg;, 18\u0026deg;, 20.2\u0026deg; and 23\u0026deg; (2θ) (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e (B)). These results indicated that ANN, RFDHT and the dual treatment did not change the crystal type of rice starch. However, the diffraction intensity was changed after modification treatment, the similar results have been reported by Zhang, et al. (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2022\u003c/span\u003e)d Liu et al. (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The characteristic peak of modified starches at 20.2\u0026deg; (2θ) was weakened in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e (B), a possible explanation is that the effect of moisture and thermal energy destroyed the long-range order structures of rice starch.\u003c/p\u003e \u003cp\u003eThe RC of native starch, RS-A, RS-RFD and RS-RFD-A were 28.31%, 27.25%, 26.60% and 27.95%, respectively. The analysis of variance showed that there was no significant (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05) change in the RC of rice starch before and after modification. However, compared with other starches, RS-RFD showed the lowest RC, the likely reason is the degradation of the crystallinity region or the increment of the amorphous region after RF dry heating (Q. Sun et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2014\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec27\" class=\"Section3\"\u003e \u003ch2\u003eThermal properties of rice starch samples analysis\u003c/h2\u003e \u003cp\u003eThermal properties indicate the thermal stability or denaturation degree of starch. The thermal characteristics of native starch, RS-A, RS-RFD and RS-RFD-A were evaluated by Differential Scanning Calorimetry (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e (A)), and the related thermal transition parameters are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, respectively. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e (A), the exothermic peak of the modified starch sample shifted to the right relative to the native starch, the result indicated that modification treatment changed the thermal properties of rice starch.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe onset (T\u003csub\u003e0\u003c/sub\u003e), peak (T\u003csub\u003ep\u003c/sub\u003e) and conclusion gelatinization temperature (T\u003csub\u003ec\u003c/sub\u003e) reflect the gelatin properties of starch. As shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, the starch after modification showed higher values of T\u003csub\u003e0\u003c/sub\u003e, T\u003csub\u003ep\u003c/sub\u003e and T\u003csub\u003ec\u003c/sub\u003e than that of native starch, indicating that modification treatment improved the transition temperatures of starch. The results may be ascribed to the interaction of amylose and amylopectin was enhanced during modification treatment, which limited the mobility of the amylopectin chains resulting in increased transition temperatures (T\u003csub\u003e0\u003c/sub\u003e, T\u003csub\u003ep\u003c/sub\u003e and T\u003csub\u003ec\u003c/sub\u003e) (Yadav et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Compared to the single treatment, the dual treatment significantly increased the transition temperatures of rice starch, indicating that RFDHT with ANN had a synergetic effect. Gelatinization enthalpy (ΔH) indicates the ratio of crystal region to amorphous regions in the double helix structure of starch. The ΔH of native starch, RS-A, RS-RFD and RS-RFD-A were 1.80, 1.29, 1.41 and 1.47, respectively. The ΔH was significantly declined (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) after modification treatment than that of native ones, these results can be due to the partial unwinding in the double helix structure of starch during heating (Q. Zhang et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). However, the synergetic treatment showed a higher ΔH compared with the ANN and RF dry heating treatment. The reason is that the double helix structure that was destroyed by high temperature recombined during subsequent ANN. These observations revealed that the combined treatment had a better effect in improving the thermal stability of starch than the single treatment.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec28\" class=\"Section2\"\u003e \u003ch2\u003ePasting properties\u003c/h2\u003e \u003cp\u003eThe pasting profiles and the pasting parameters of modified and native starches are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e (B) and Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, respectively. It is noticed that native and modified rice starches showed noticeably different pasting profiles (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e (B)), which indicated that modification treatment changed the pasting properties of RS. As shown in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, the RS-RFD showed higher pasting viscosities (peak viscosity, final viscosity, trough viscosity, breakdown, and setback) compared with native ones, this is consistent with the previous research on rice starch and quinoa starch modified by DHT (Qiu et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Zhou et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003ePeak viscosity (PV) represents the maximum viscosity, which is related to the degree of swelling of starch granules and leaching of amylose from starch granules (Kong et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Zheng et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Final viscosity (FV) represents the viscosity at the cool phase. Compared with normal rice starch (1105.00 cP and 1286.02 cP), the RS-RFD showed a higher PV (1199.67 cP) and FV (1329.33 cP). The increment of PV might be ascribed to the higher amylose content after RFDHT. In addition, the increment of FV at the cooling phase may be due to the aggregation of amylose molecules (Zhou et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). After ANN and the combined treatment, the PV (609.00 and 562.00 cP) and FV (866.34 and 797.67) of starch significantly declined than that of native one, which may be attributed to the swelling and the amylose leaching of starch granules were resisted during ANN. Interestingly, RS-RFD-A had the lowest PV, indicating the combination of RFDHT and ANN had a better effect on starch thermal ability improvement.\u003c/p\u003e \u003cp\u003eThrough viscosity (TV) is the lowest viscosity at the end heating phase (Sharma et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). The results indicated that the TV of RS-RFD increased than that of the native one, but ANN and the dual treatment significantly (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) declined the TV. The increment of TV may be due to the starch granules destroyed during RFDHT.\u003c/p\u003e \u003cp\u003eBreakdown (BD) represents the difference between peak viscosity and through viscosity and reflects the shear resistance of the starch (Xu et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Setback (SB) reflects the tendency of paste to retrograde during the cool phase (Li et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), which is the difference between final viscosity and through viscosity. As shown in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, RS-RFD showed higher BD and SB than the native counterpart, which can be attributed to the weakening of the ordered structure of the starch, leading to the starch granules being easily destroyed. Compared to other starch samples, RS-RFD-A showed the lowest BD and SB, this result indicated that the dually treated starch had more resistance to shearing and that it had higher pasting stability.\u003c/p\u003e \u003cp\u003eAfter modifying treatment, the peak time (PT) and gelatinization temperature (GT) did not significantly (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05) change among native starch and modification-treated starches. However, compared with normal rice starch and RS-RFD, the GT of RS-RFD-A improved, indicating that the temperature required for starch gelatinization increased after the combined treatment. This may be due to the enhancement of amylose-amylopectin and/or amylose-amylopectin interactions during the combined treatment, which caused the starch more difficult to be gelatinized.\u003c/p\u003e \u003cp\u003eAbove all, the lower paste viscosity and higher pasting temperature of RFDHT combined annealing treated starch samples indicated that the starch granule structures were strengthened and the enhancement of intra-molecular bonding ability, which caused the increment in pasting stability of the dually treated-starch sample.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThe study investigated the impacts of the combination of RFDHT and ANN on the digestible properties, physicochemical properties and multiscale structure of RS. The combined modification significantly decreased the SP but increased the particle size, solubility and AC of the starch. In addition, the combination treatment showed the lowest enzymatic digestibility by decreasing the content of RDS but increasing the content of SDS and RS. Compared with single modified treatment, the dual treatment conspicuously reduced the pasting viscosities but improved the gelatinization transition temperature, thereby significantly improving the gelatinization and thermal stability of the starch. The combination treatment of RFDHT and ANN has been proven with potential to limit the enzymatic digestibility of RS. Further, the dually modified RS can be combined with rice flour or other cereal flour to develop starch-based slowly digestible foods in the future.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eConflicts of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eContributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eYifei Dong: Investigation, Data curation, Writing original draft; Xinyu Li: Resources, Methodology; Yan Cui: Resources, Methodology; Liang Zhang: Resources, Methodology; Xiaoting Xuan: Resources, Methodology; Ruiling Lv: Resources, Methodology; Xingquan Liu: Resources, Methodology; Jiangang Ling: Supervision, Resources, Project administration, Writing - review \u0026amp; editing; Suhong Li: Supervision, Resources, Project administration, Writing - review \u0026amp; editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was supported by the Science and Technology Innovation 2025 Major Project of Ningbo (No.2022Z182).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBian, L., \u0026amp; Chung, H.-J. 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Effects of repeated and continuous dry heat treatments on the physicochemical and structural properties of quinoa starch. \u003cem\u003eFood Hydrocolloids, 113\u003c/em\u003e, 106532. doi: https://doi.org/10.1016/j.foodhyd.2020.106532\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e\u0026nbsp; Particle distribution, AC, short-range ordered degree (R\u003csub\u003e1047/1022\u003c/sub\u003e) and thermal parameters of the native and modified RS.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"610\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"10.801963993453356%\"\u003e\n \u003cp\u003eSample\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.53027823240589%\"\u003e\n \u003cp\u003eD (4,3) (nm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.402618657937808%\"\u003e\n \u003cp\u003eAC (mg/g)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.456628477905074%\"\u003e\n \u003cp\u003eR\u003csub\u003e1050/1020\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.76595744680851%\"\u003e\n \u003cp\u003eT\u003csub\u003e0\u003c/sub\u003e (℃)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.801963993453356%\"\u003e\n \u003cp\u003eT\u003csub\u003ep\u003c/sub\u003e (℃)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.620294599018003%\"\u003e\n \u003cp\u003eT\u003csub\u003ec\u003c/sub\u003e (℃)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.620294599018003%\"\u003e\n \u003cp\u003e\u0026Delta;H (J/g)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"10.801963993453356%\"\u003e\n \u003cp\u003eNative\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.53027823240589%\"\u003e\n \u003cp\u003e1406.00 \u0026plusmn; 81.65\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.402618657937808%\"\u003e\n \u003cp\u003e181.26 \u0026plusmn; 1.90\u003csup\u003ebc\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.456628477905074%\"\u003e\n \u003cp\u003e1.39 \u0026plusmn; 0.00\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.76595744680851%\"\u003e\n \u003cp\u003e63.12 \u0026plusmn; 0.33\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.801963993453356%\"\u003e\n \u003cp\u003e66.77 \u0026plusmn; 0.75\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.620294599018003%\"\u003e\n \u003cp\u003e73.08 \u0026plusmn; 0.07\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.620294599018003%\"\u003e\n \u003cp\u003e1.80 \u0026plusmn; 0.11\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"10.801963993453356%\"\u003e\n \u003cp\u003eRS-A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.53027823240589%\"\u003e\n \u003cp\u003e1901.00 \u0026plusmn; 126.58\u003csup\u003ebc\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.402618657937808%\"\u003e\n \u003cp\u003e168.60 \u0026plusmn; 14.22\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.456628477905074%\"\u003e\n \u003cp\u003e1.30 \u0026plusmn; 0.02\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.76595744680851%\"\u003e\n \u003cp\u003e64.59 \u0026plusmn; 3.15\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.801963993453356%\"\u003e\n \u003cp\u003e68.81 \u0026plusmn; 1.39\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.620294599018003%\"\u003e\n \u003cp\u003e73.83 \u0026plusmn; 0.20\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.620294599018003%\"\u003e\n \u003cp\u003e1.29 \u0026plusmn; 0.17\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"10.801963993453356%\"\u003e\n \u003cp\u003eRS-RFD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.53027823240589%\"\u003e\n \u003cp\u003e2367.33 \u0026plusmn; 458.12\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.402618657937808%\"\u003e\n \u003cp\u003e202.29 \u0026plusmn; 7.69\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.456628477905074%\"\u003e\n \u003cp\u003e1.37 \u0026plusmn; 0.04\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.76595744680851%\"\u003e\n \u003cp\u003e61.19 \u0026plusmn; 1.00\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.801963993453356%\"\u003e\n \u003cp\u003e67.21 \u0026plusmn; 3.00\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.620294599018003%\"\u003e\n \u003cp\u003e72.46 \u0026plusmn; 2.63\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.620294599018003%\"\u003e\n \u003cp\u003e1.41 \u0026plusmn; 0.14\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"10.801963993453356%\"\u003e\n \u003cp\u003eRS-RFD-A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.53027823240589%\"\u003e\n \u003cp\u003e2797.50 \u0026plusmn; 392.31\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.402618657937808%\"\u003e\n \u003cp\u003e187.47 \u0026plusmn; 4.14\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.456628477905074%\"\u003e\n \u003cp\u003e1.44 \u0026plusmn; 0.02\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.76595744680851%\"\u003e\n \u003cp\u003e67.37 \u0026plusmn; 2.80\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.801963993453356%\"\u003e\n \u003cp\u003e71.38 \u0026plusmn; 2.08\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.620294599018003%\"\u003e\n \u003cp\u003e75.17 \u0026plusmn; 1.83\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.620294599018003%\"\u003e\n \u003cp\u003e1.47 \u0026plusmn; 0.05\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eValues are means (\u0026plusmn;SD) of triplicate samples. \u003csup\u003ea-c\u003c/sup\u003eThe same letter in one column means no significant difference (\u003cem\u003ep\u003c/em\u003e \u0026gt; 0.05).\u003c/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2\u003c/strong\u003e\u0026nbsp; The SP and solubility of the native and modified RS\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"557\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.515260323159785%\" rowspan=\"2\"\u003e\n \u003cp\u003eSample\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"46.49910233393178%\" colspan=\"5\"\u003e\n \u003cp\u003eSolubility (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"43.98563734290844%\" colspan=\"5\"\u003e\n \u003cp\u003eSP (g/g)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"10.515873015873016%\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.119047619047619%\"\u003e\n \u003cp\u003e60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.119047619047619%\"\u003e\n \u003cp\u003e70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.30952380952381%\"\u003e\n \u003cp\u003e80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.325396825396826%\"\u003e\n \u003cp\u003e90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.325396825396826%\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.515873015873016%\"\u003e\n \u003cp\u003e60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.325396825396826%\"\u003e\n \u003cp\u003e70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.325396825396826%\"\u003e\n \u003cp\u003e80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.119047619047619%\"\u003e\n \u003cp\u003e90\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.515260323159785%\"\u003e\n \u003cp\u003eNative\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.515260323159785%\"\u003e\n \u003cp\u003e2.78 \u0026plusmn; 0.46\u003csup\u003eCb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.156193895870736%\"\u003e\n \u003cp\u003e2.86 \u0026plusmn; 0.16\u003csup\u003eCb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.156193895870736%\"\u003e\n \u003cp\u003e4.13 \u0026plusmn; 0.89\u003csup\u003eCb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.23339317773788%\"\u003e\n \u003cp\u003e6.30 \u0026plusmn; 0.46\u003csup\u003eABba\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.43806104129264%\"\u003e\n \u003cp\u003e8.09 \u0026plusmn; 1.79\u003csup\u003eBa\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.43806104129264%\"\u003e\n \u003cp\u003e3.52 \u0026plusmn; 0.39\u003csup\u003eAd\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.515260323159785%\"\u003e\n \u003cp\u003e6.12 \u0026plusmn; 0.27\u003csup\u003eAc\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.43806104129264%\"\u003e\n \u003cp\u003e7.41 \u0026plusmn; 0.19\u003csup\u003eAc\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.43806104129264%\"\u003e\n \u003cp\u003e10.16 \u0026plusmn; 0.40\u003csup\u003eAb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.156193895870736%\"\u003e\n \u003cp\u003e15.82 \u0026plusmn; 1.53\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.515260323159785%\"\u003e\n \u003cp\u003eRS-A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.515260323159785%\"\u003e\n \u003cp\u003e3.44 \u0026plusmn; 0.68\u003csup\u003eBCd\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.156193895870736%\"\u003e\n \u003cp\u003e4.48 \u0026plusmn; 0.69\u003csup\u003eAcd\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.156193895870736%\"\u003e\n \u003cp\u003e5.39 \u0026plusmn; 0.36\u003csup\u003eBbc\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.23339317773788%\"\u003e\n \u003cp\u003e6.73 \u0026plusmn; 0.21\u003csup\u003eABb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.43806104129264%\"\u003e\n \u003cp\u003e9.47 \u0026plusmn; 0.96\u003csup\u003eBa\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.43806104129264%\"\u003e\n \u003cp\u003e2.56 \u0026plusmn; 0.11\u003csup\u003eBe\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.515260323159785%\"\u003e\n \u003cp\u003e5.45 \u0026plusmn; 0.20\u003csup\u003eBCd\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.43806104129264%\"\u003e\n \u003cp\u003e7.45 \u0026plusmn; 0.11\u003csup\u003eAc\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.43806104129264%\"\u003e\n \u003cp\u003e8.78 \u0026plusmn; 0.07\u003csup\u003eBb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.156193895870736%\"\u003e\n \u003cp\u003e14.19 \u0026plusmn; 0.45\u003csup\u003eAba\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.515260323159785%\"\u003e\n \u003cp\u003eRS-RFD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.515260323159785%\"\u003e\n \u003cp\u003e4.17 \u0026plusmn; 0.05\u003csup\u003eABc\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.156193895870736%\"\u003e\n \u003cp\u003e5.07 \u0026plusmn; 0.32\u003csup\u003eBc\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.156193895870736%\"\u003e\n \u003cp\u003e5.40 \u0026plusmn; 1.01\u003csup\u003eBbc\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.23339317773788%\"\u003e\n \u003cp\u003e7.04 \u0026plusmn; 1.28\u003csup\u003eABb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.43806104129264%\"\u003e\n \u003cp\u003e10.47 \u0026plusmn; 0.80\u003csup\u003eBa\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.43806104129264%\"\u003e\n \u003cp\u003e2.03 \u0026plusmn; 0.07\u003csup\u003eBd\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.515260323159785%\"\u003e\n \u003cp\u003e5.87 \u0026plusmn; 0.27\u003csup\u003eAbc\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.43806104129264%\"\u003e\n \u003cp\u003e6.70 \u0026plusmn; 0.91\u003csup\u003eAc\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.43806104129264%\"\u003e\n \u003cp\u003e8.81 \u0026plusmn; 0.68\u003csup\u003eBb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.156193895870736%\"\u003e\n \u003cp\u003e13.93 \u0026plusmn; 0.68\u003csup\u003eAba\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.515260323159785%\"\u003e\n \u003cp\u003eRS-RFD-A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.515260323159785%\"\u003e\n \u003cp\u003e4.77 \u0026plusmn; 0.41\u003csup\u003eAc\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.156193895870736%\"\u003e\n \u003cp\u003e7.06 \u0026plusmn; 0.44\u003csup\u003eAb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.156193895870736%\"\u003e\n \u003cp\u003e7.67 \u0026plusmn; 0.98\u003csup\u003eAb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.23339317773788%\"\u003e\n \u003cp\u003e8.13 \u0026plusmn; 0.31\u003csup\u003eAb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.43806104129264%\"\u003e\n \u003cp\u003e14.79 \u0026plusmn; 0.44\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.43806104129264%\"\u003e\n \u003cp\u003e1.93 \u0026plusmn; 0.50\u003csup\u003eBe\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.515260323159785%\"\u003e\n \u003cp\u003e4.91 \u0026plusmn; 0.32\u003csup\u003eCd\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.43806104129264%\"\u003e\n \u003cp\u003e6.82 \u0026plusmn; 0.29\u003csup\u003eAc\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.43806104129264%\"\u003e\n \u003cp\u003e8.38 \u0026plusmn; 0.60\u003csup\u003eBb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.156193895870736%\"\u003e\n \u003cp\u003e12.15 \u0026plusmn; 0.54\u003csup\u003eBa\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eValues are means (\u0026plusmn;SD) of triplicate samples. \u003csup\u003ea-e\u003c/sup\u003eThe same letter in one row means no significant difference (\u003cem\u003ep\u003c/em\u003e \u0026gt; 0.05); \u003csup\u003eA-C\u003c/sup\u003eThe same letter in one column means no significant difference (\u003cem\u003ep\u003c/em\u003e \u0026gt; 0.05).\u003c/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3\u003c/strong\u003e\u0026nbsp; The content of RDS, SDS and RS in native and modified RS\u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eSample\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eRDS (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eSDS (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eRS (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eNative\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e70.08% \u0026plusmn; 2.26\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e12.54% \u0026plusmn; 2.34\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e17.38% \u0026plusmn; 4.50\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eRS-A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e67.14% \u0026plusmn; 1.05\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e13.11% \u0026plusmn; 1.32\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e19.74% \u0026plusmn; 2.36\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eRS-RFD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e65.19% \u0026plusmn; 0.84\u003csup\u003ebc\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e12.61% \u0026plusmn; 1.31\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e22.20% \u0026plusmn; 1.29\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003eRS-RFD-A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e61.03% \u0026plusmn; 2.68\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e14.23% \u0026plusmn; 3.92\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"25%\"\u003e\n \u003cp\u003e24.74% \u0026plusmn; 1.7\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eValues are means (\u0026plusmn;SD) of triplicate samples. \u003csup\u003ea-c\u003c/sup\u003eThe same letter in one column means no significant difference (\u003cem\u003ep\u003c/em\u003e \u0026gt; 0.05).\u003c/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 4\u0026nbsp;\u003c/strong\u003ePasting parameters of the native and modified RS\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"573\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"15.505226480836237%\"\u003e\n \u003cp\u003eSample\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003ePV/cP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003eTV/cP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003eBD/cP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003eFV/cP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003eSB/cP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.020905923344948%\"\u003e\n \u003cp\u003ePT/min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.498257839721255%\"\u003e\n \u003cp\u003eGT/℃\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"15.505226480836237%\"\u003e\n \u003cp\u003eNative\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003e1105.00 \u0026plusmn; 16.97\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003e901.33 \u0026plusmn; 8.26\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003e203.67 \u0026plusmn; 8.73\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003e1286.02 \u0026plusmn; 7.12\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\" valign=\"top\"\u003e\n \u003cp\u003e384.67 \u0026plusmn; 1.70\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.020905923344948%\" valign=\"top\"\u003e\n \u003cp\u003e6.89 \u0026plusmn; 0.03\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.498257839721255%\" valign=\"top\"\u003e\n \u003cp\u003e94.55 \u0026plusmn; 0.05\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"15.505226480836237%\"\u003e\n \u003cp\u003eRS-A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003e609.00 \u0026plusmn; 3.56\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003e583.33 \u0026plusmn; 6.65\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003e25.67 \u0026plusmn; 5.72\u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003e866.34 \u0026plusmn; 23.72\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\" valign=\"top\"\u003e\n \u003cp\u003e282.67 \u0026plusmn; 29.10\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.020905923344948%\" valign=\"top\"\u003e\n \u003cp\u003e6.67 \u0026plusmn; 0.11\u003csup\u003ea\u003c/sup\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.498257839721255%\" valign=\"top\"\u003e\n \u003cp\u003e94.57 \u0026plusmn; 0.09\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"15.505226480836237%\"\u003e\n \u003cp\u003eRS-RFD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003e1199.67 \u0026plusmn; 31.85\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003e932.67 \u0026plusmn; 31.98\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003e267.01 \u0026plusmn; 6.38\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003e1329.33 \u0026plusmn; 87.95\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\" valign=\"top\"\u003e\n \u003cp\u003e396.67 \u0026plusmn; 57.04\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.020905923344948%\" valign=\"top\"\u003e\n \u003cp\u003e6.80 \u0026plusmn; 0.14\u003csup\u003ea\u003c/sup\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.498257839721255%\" valign=\"top\"\u003e\n \u003cp\u003e94.55 \u0026plusmn; 0.28\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"15.505226480836237%\"\u003e\n \u003cp\u003eRS-RFD-A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003e562.00 \u0026plusmn; 4.08\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003e505.33 \u0026plusmn; 17.91\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003e56.67 \u0026plusmn; 14.06\u003csup\u003ec\u003c/sup\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\"\u003e\n \u003cp\u003e797.67 \u0026plusmn; 52.95\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.195121951219512%\" valign=\"top\"\u003e\n \u003cp\u003e292.33 \u0026plusmn; 70.71\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.020905923344948%\" valign=\"top\"\u003e\n \u003cp\u003e6.49 \u0026plusmn; 0.22\u003csup\u003ea\u003c/sup\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.498257839721255%\" valign=\"top\"\u003e\n \u003cp\u003e94.72 \u0026plusmn; 0.24\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eValues are means (\u0026plusmn;SD) of triplicate samples. \u003csup\u003ea-d\u003c/sup\u003eThe same letter in one column means no significant difference (\u003cem\u003ep\u003c/em\u003e \u0026gt; 0.05).\u003c/p\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":"Radio frequency dry heating, Annealing, Rice starch, Digestibility, Multiscale structure, Pasting properties","lastPublishedDoi":"10.21203/rs.3.rs-4370667/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4370667/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eRadio frequency dry heating treatment combined with annealing treatment (RFDHT-ANN) was applied in this study to investigate the effects of the combined treatment on the digestibility, pasting properties, and multiscale structure of rice starch (RS). In practice, the combined modification treatment did not change the crystal type but resulted in a change in the microscopic morphology of RS. The dual treatment improved the amylose content, solubility, particle size, relative crystallinity and gelatinization transition temperature but declined the starch's swelling power. The lowest enzymatic digestibility was found with a decrease of 9.05% of rapidly digestible starch but an increment of 1.69% of slowly digestible starch and 7.38% of resistant starch. Compared with native starch, the characteristic peak of modified starches at 20.2\u0026deg; (2θ) was weakened. Furthermore, the dual treatment noticeably decreased the gelatinating viscosity of RS. This study provides innovative ideas for improving starch-based, slowly digestible foods in the future.\u003c/p\u003e","manuscriptTitle":"In vitro digestion, physicochemical and structural properties of rice starch dual-treated with radio frequency dry heating and annealing treatment","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-05-10 11:15:38","doi":"10.21203/rs.3.rs-4370667/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":"18b57082-7d2d-4db9-8f0d-9346e1e73614","owner":[],"postedDate":"May 10th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-06-13T03:59:18+00:00","versionOfRecord":[],"versionCreatedAt":"2024-05-10 11:15:38","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4370667","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4370667","identity":"rs-4370667","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}