{"paper_id":"2653ee0a-6bb5-43b2-90b2-8386bf628cdd","body_text":"The impact of heat treatments on the content of beneficial substances in the most consumed vegetables in Slovakia | 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 The impact of heat treatments on the content of beneficial substances in the most consumed vegetables in Slovakia Judita Lidiková, Natália Čeryová, Marek Šnirc, Marek Bobko, Janette Musilová, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-1584531/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 In the present study, we investigated the effects of heat treatment (boiling in water, steaming) on ​​changes in the content of vitamin C, total polyphenols, and changes in antioxidant activity in garlic, onion, pepper, potatoes, and tomatoes. In the obtained extracts of the mentioned raw and heat-treated vegetables, we determined the content of vitamin C by HPLC, the content of total polyphenols by Folin- Ciocalteau colorimetric method, as well as the antioxidant activity (DPPH assay, ABTS assay, FRAP assay). The obtained results showed that the content of vitamin C, as well as the content of total polyphenols in the monitored vegetables after heat treatment (cooking in water), was significantly reduced (P < 0.05) compared to the content of these bioactive substances in raw vegetables. A slight decrease in vitamin C and total polyphenol content was recorded in the steamed samples. This decrease was not statistically significant for all these crops. Determination of antioxidant activity again showed a more significant decrease in antioxidant activity values (P < 0.05) (DPPH, ABTS, FRAP) after boiling in water than after steaming. The heat treatment has a significant impact on the change in the content of monitored bioactive substances in the analyzed vegetables. Based on our achieved results, steaming appears to be a more gentle way in terms of preserving natural antioxidants, which can significantly contribute to the elimination of oxidative stress in our organism. heat treatment vegetables vitamin C total polyphenols antioxidant activity Figures Figure 1 Figure 2 Figure 3 Introduction Allium vegetables ( Allium L. ) , as well as potatoes ( Solanum tuberosum L.), peppers ( Capsicum annuum L .), and tomatoes ( Solanum lycopersicum L .) are commonly consumed types of vegetables in Slovakia. They are an integral part of the preparation of many meals and dishes in fresh or technologically modified form. These most cultivated and also the most consumed crops with a long tradition are characterized by a high content of biologically active phytomolecules. Optimal intake of phytochemicals and a nutritionally balanced diet supplemented with specific ingredients such as some antioxidant polyphenolic compounds play a key role in maintaining health and have the potential to reduce the risk of diseases of civilization [ 1 – 3 ]. The genus Allium , which also includes onion ( Allium cepa L.) and garlic ( Allium sativum L.), is a rich source of polyphenols. It is characterized by a high content of flavonoids such as quercetin, kaempferol, and their glycosides, phenolic acids such as β-coumaric acid, caffeic acid, and sinapic acid [ 4 ], anthocyanins, sulfur compounds, and saponins [ 5 , 6 ]. The major organosulfur compounds in the genus Allium are allylcysteines, S-alkenyl-L-cysteine ​​sulfoxides, thiosulfinates, and sulfides [ 7 ]. These substances are precursors of flavors and fragrances and some have antioxidant properties [ 8 ]. S-allylcysteine ​​sulfoxide reduces cholesterol, increases the activity of enzymes that protect against electrophilic agents, improves insulin sensitivity, and tends to increase nutrient absorption and assimilation [ 9 ]. Potatoes, peppers, and tomatoes are vegetables whose general consumption in Slovakia is high and regular consumption of these crops can ensure the supply of a sufficient amount of polyphenolic substances to the human body. Polyphenols are considered to be very important antioxidants in the human diet that are able to prevent the formation of free radicals with harmful effects on health and are therefore important in reducing the risk of diseases of civilization [ 10 ]. Potatoes contain a number of compounds with high nutritional value, are an excellent source of energy, and contain secondary metabolites that are useful for human health [ 11 ]. They are considered a rich source of polyphenols. They contain polyphenols from 4 classes such as phenolic acids (chlorogenic, cryptochlorogenic and neochlorogenic, vanillic, caffeic acid), flavonols (rutin), flavan-3-ols (catechin), and anthocyanins [ 12 , 13 ]. Due to its rich content of phytonutrients and bioactive substances, potatoes are considered a functional food and their consumption improves the health of the gastrointestinal tract as well as the intestines [ 14 ]. From an agricultural point of view, pepper is one of the most important crops, not only in Slovakia but also worldwide [ 15 ]. The bioactive substances found in peppers are known for their analgesic, antiobesity, cardio protective, and dietary properties. Pepper has strong anti-inflammatory effects, helps to increase the overall immunity of the body, and helps proper digestion. Due to its low-calorie content and zero fat content, pepper is an ideal supplement to the daily diet [ 16 ]. It contains compounds with antioxidant activity, which is attributed to the ability of these compounds to capture singlet molecular oxygen, reactive oxygen species, peroxyl radicals, and reactive nitrogen species [ 15 ]. Of the polyphenolic compounds, they contain phenolic acids such as vanilla, gallic, cinnamic, p-hydroxybenzoic, p-coumaric, and ferulic acids, which contribute significantly to the antioxidant activity of peppers [ 17 ]. Of the flavonoids, pepper contains vanillin, quercetin, rutin and luteolin [ 3 ]. Carotenoids represent important dyes that are also found in peppers. Capsanthin, capsorubin, zeaxanthin, β-carotene, and β-cryptoxanthin have been identified from carotenoids in peppers [ 18 ]. Tomatoes ( Solanum lycopersicum L.) are widely grown around the world and are becoming increasingly popular in both fresh and processed forms. Tomatoes are a rich source of carotenoids, 80% of which are lycopene [ 19 ]. This natural antioxidant is known to protect against several diseases, inhibits the growth of many cancer cells, is particularly beneficial against prostate cancer [ 20 ], and has antidiabetic activity [ 9 ]. Phenolic compounds such as chlorogenic acid, naringin, resveratrol, and quercetin have been found in tomato peel and seeds [ 21 , 22 ]. Of the phenolic acids, tomatoes are also characterized by protocatechuic acid and 2,5-dihydroxybenzoic acid [ 23 ]. The presence of these key antioxidants contributes greatly to the antioxidant activity of tomatoes. Vegetables, which are either eaten fresh or cooked before consumption, are one of the most important components of a human diet. Vegetable processing is said to significantly affect its nutritional and sensory value. Choosing the right technological operation is very important for maintaining the quality of vegetables and their products in terms of the content of healthy substances. The content of phytochemicals in vegetables depends on different technological conditions of processing, on their stability during processing, which is influenced by sensitivity and stability to oxidation, thermal degradation and is influenced by pH as well as redox potential [ 9 ]. Therefore, this study aimed to monitor the impact of heat treatment on the content of bioactive substances and antioxidant activity of vegetables that are most consumed in Slovakia. Materials And Methods The following plant material, chemicals, and methods were used in the study. Materials Five vegetables, namely tomato ( Solanum lycopersicum L.), pepper ( Capsicum annuum L.), potato ( Solanum tuberosum L.), onion ( Allium cepa L.), and garlic ( Allium sativum L.) were analyzed in this study. All chemicals used for all analysis; methanol (99,8%), methanol (80%), gallic acid, DPPH (2,2ʹ-diphenyl-1-picrylhydrazyl), Trolox (2,5,7,8-tetramethylchroman-2-carboxylic acid), ABTS (2,2ʹ-azino-bis (3-ethylbenzthiazoline-6-sulfonic) acid, (p.a.), TPTZ (2,4,6-tri (2-pyridyl) -s-triazine), Na 2 CO 3 , K 2 S 2 O 8 , HPLC standards (purity range 98.0–99.9%): methanol (HPLC grade), acetonitrile (gradient HPLC grade), and phosphoric acid (ACS grade) were purchased from Sigma-Aldrich (Sigma-Aldrich, USA). Double deionized water (ddH2O) was treated (0.054 µS.cm − 1 ) in a Simplicity 185 purification system (Millipore, UK). Folin-Ciocalteau reagent used for the determination of total phenolic content was purchased from Merck (Germany). Extracts were prepared by shaking 25 g of homogenized sample in 80% methanol on the Unimax 2010 horizontal shaker (Heidolph Instrument GmbH, Germany) for 12 hours. The solution were then filtered through Munktell No. 390 filtrating paper (Munktell & Filtrac, Germany) and stored in the closed 50 mL vial tubes. Heat treatment Potatoes, onion and garlic were peeled. From the pepper, seeds were removed. Vegetables were then chopped into smaller pieces, and underwent heat treatment. For boiling, samples were added to boiling distilled water (samples:water = 1:5), and cooked for 10 minutes. For steaming, samples were steamed above boiling distilled water for 10 minutes. Vitamin C content Vitamin C content was determined by high performance liquid chromatography (HPLC) system. Samples of raw and cooked vegetables were homogenized using Grindomix GM 2000 Retsch, 2000 rpm, for 30 sec. 5 g of homogenate was weighted and 50 mL of 3% meta-phosphoric acid (MPA) was added. The extracts were bathed for 5 minutes on ultrasonic bath Bandelin Sonorex Digitec DT 510 F, (Bandelin electronic GmbH & Co, Germany), centrifuged on Hettich® Universal 320/320 R centrifuge (Sigma-Aldrich, USA), and then decanted through 55 mm Whatman filter papers (Sigma-Aldrich, MO, USA). Supernatants were filtered through 0.45 µM membrane filters (Millipore, MA, USA). The separations were carried out on column Cortecs 18 (C18) 2.7 µm, 4.6 mm x 150 mm (Waters Corporation, MA, USA). The reverse phase of liquid chromatography method was used for the determination of vitamin C content by isocratic elution by wavelength 254 nm. The mobile phases comprise methanol and water from Purification system (Simplicity 185; Millipore SAS, Molsheim, France) which was used to provide double deionized water (ddH2O, 18.2 MΩ/cm, 20°C (5:95, v/v) and volume of injection was 10 µl. Temperature of the column during the analyses was adjusted at 25°C and the retention times were app. 5 minutes. The peak was read at 254 nm using an UV detector and quantification was determined via external calibration against ascorbic acid. Total polyphenol content Total polyphenol content was determined by Folin - Ciocalteau colorimetric method [ 24 ]. Folin – Ciocalteu phenol reagent (Merck, Germany), 20% Na 2 CO 3 (Sigma Aldrich, USA), and distilled water were used. 0.1 mL of extract was pipetted into 50 mL volumetric flask. 0.85 mL of Folin Ciocalteau reagent was added, and after 3 minutes, 5 mL of 20% Na 2 CO 3 was added. The mixture was stirred, and flask was filled with distilled water to the mark. Flasks were left for 2 hour at laboratory temperature, and then measured against blank solution at 765 nm, using Shimadzu UV/VIS scanning spectrophotometer. Total polyphenol content was expressed as mg of gallic acid equivalent in 1 kg of dry matter, based on the calibration curve (R² = 0.995) Antioxidant activity using DPPH Radical Scavenging Capacity Assay Antioxidant activity was measured by DPPH radical scavenging assay [ 25 ]. DPPH •+ radical (2,2-diphenyl-1-picrylhydrazyl) (Sigma Aldrich, USA) and methanol (Sigma Aldrich, USA) were used to produce working DPPH solution. 1 mL of extract was pipetted into 3.9 mL of working DPPH solution, stirred, and left in dark. After 10 minutes, solution was measured against blank solution at nm, using Shimadzu UV/VIS scanning spectrophotometer. Antioxidant activity was expressed as mmol of Trolox equivalent in 1 kg of dry matter, based on the calibration curve (R² = 0.992). Antioxidant activity using ABTS assay Antioxidant activity was determined using ABTS assay [ 26 ]. ABTS •+ radical cation − (2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (Sigma Aldrich, USA), potassium persulfate (K 2 S 2 O 8 ) (Sigma Aldrich, USA), and acetate buffer (pH = 4.3) were used to produce working ABTS solution. 0.05 mL of extract was pipetted into 3 mL of ABTS solution, stirred and left in the dark. After 20 minutes, absorbance was measured against blank solution at nm, using Shimadzu UV/VIS scanning spectrophotometer. Antioxidant activity was expressed as mmol of Trolox equivalent in 1 kg of dry matter, based on the calibration curve (R² = 0.993). Antioxidant activity using FRAP assay Antioxidant activity was determined using the FRAP assay [ 27 ]. TPTZ − (2,4,6-tris(2-pyridyl)-S-triazine) (Sigma Aldrich, USA), ferric chloride (FeCl 3 ) (Sigma Aldrich, USA), and acetate buffer (pH = 3.5) were used to produce working FRAP solution. 0.05 mL of extract was pipetted into 3 mL of FRAP solution, stirred, and left in dark. After 20 minutes, absorbance was measured against blank solution at 593 nm, using Shimadzu UV- 1800 UV/ Visible Scanning Spectrophotometer, Shimadzu, Japan. Antioxidant activity was expressed as mmol of Trolox equivalent in 1 kg of dry matter, based on the calibration curve (R² = 0.996) Statistical analysis All the tested variables did not follow the normal distribution according to the Shapiro-Wilk test, therefore Kruskal-Wallis and Dunn pairwise comparison with the Bonferroni correction were performed to find the significant differences between the tested variables. The Spearman correlation test was used to analyze the relationships between the tested variables. All calculations were performed using Jamovi software (version 2.2.5) [ 28 – 33 ]. Results And Discussion Most vegetables go through a severe heat treatment before consumption. Different cooking methods have a great influence on the phytochemical profile of vegetables and their biological properties [ 34 ]. Heat treatment of vegetables is generally considered to be largely responsible for the loss and development of undesirable color, texture, taste, and nutritional quality of food. Thermal degradation can lead to a reduction of thermolabile compounds such as vitamins C, A, E, and some polyphenols and can also affect the antioxidant activity of the vegetables consumed. In the present article, we dealt with the analysis of selected substances with a beneficial effect that are found in commonly grown as well as economically available vegetables in Slovakia, which include peppers, tomatoes, potatoes, as well as onions, and garlic. Commonly available, traditional vegetables are of great importance to many countries in the world and their consumption has a significant beneficial effect on the human body. Heat treatment is one of the various types of technological processing that is used to process food raw materials into meals. The most common methods of heat treatment are cooking, steaming, and stewing. The risk of unwanted substances is roasting, baking, frying, and grilling. As the temperature rises, some important nutrients may be lost and harmful substances may form. On the other hand, the advantages of heat treatment include microbial safety, elimination or minimization of the content of some anti-nutritional and toxic substances, as well as increased digestibility of food raw materials. In our work, we monitored changes in the content of bioactive substances by cooking and steaming. Vitamin C content, total polyphenol content and antioxidant activity of analyzed raw, boiled and steamed vegetables are shown in Table 1 . and Table 2 . Table 1 Vitamin C content and total polyphenol content in analyzed samples Vitamin C (mg.kg − 1 DM) TPC (mg GAE.kg − 1 DM) Type/ Treatment Raw Boiling Steaming Raw Boiling Steaming Garlic 137 ± 62.3 b 66 ± 21.8 a 106 ± 46.4 b 1487 ± 325 a 597 ± 79.4 b 701 ± 101.1 c Onion 786 ± 342.2 b 336 ± 128.4 a 654 ± 295.3 b 6557 ± 3207 a 3715 ± 1579.4 a 4903 ± 2051.4 a Pepper 2725 ± 577.2 a 998 ± 130.2 b 1741 ± 124.8 c 8102 ± 1242 b 3354 ± 641.2 a 6888 ± 739.1 b Potato 691 ± 68.7 a 335 ± 20.3 b 560 ± 31.8 c 1522 ± 1114 a 623 ± 357 a 1325 ± 924.3 a Tomato 2091 ± 194.6 a 875 ± 208.4 b 1662 ± 170.1 c 3714 ± 188 b 2631 ± 231.4 a 3663 ± 377.5 b Different lowercase letters indicate a significant difference between tested parameters Table 2 Antioxidant activity of analyzed samples DPPH (mmol TE.kg − 1 DM) ABTS (mmol TE.kg − 1 DM) FRAP (mmol TE.kg − 1 DM) Type/ Treatment Raw Boiling Steaming Raw Boiling Steaming Raw Boiling Steaming Garlic 3.4 ± 1.05 b 1.56 ± 0.39 a 1.81 ± 0.34 a 4.17 ± 1.06 b 2.36 ± 0.73 a 3.18 ± 0.63 a 3.58 ± 1.22 b 1.65 ± 0.51 a 2.52 ± 0.83 a, b Onion 13.7 ± 6.4 b 5.64 ± 3.38 a 7.8 ± 4.58 a, b 18.61 ± 9.57 b 7.17 ± 3.49 a 14.76 ± 8.09 b 10.82 ± 5.22 b 4.48 ± 1.79 a 11.44 ± 6.42 b Pepper 21.56 ± 6.02 b 10.6 ± 3.11 a 21.01 ± 5.03 b 29.95 ± 8.28 b 12.62 ± 4.9 a 27.35 ± 8.7 b 24.69 ± 3.13 b 11.26 ± 4.68 a 22.51 ± 2.82 b Potato 3.36 ± 0.63 b 1.77 ± 0.4 a 2.92 ± 0.45 b 5.75 ± 1.18 b 3.69 ± 1.43 a 4.25 ± 0.84 a 2.27 ± 0.86 b 1.53 ± 0.54 a, b 1.52 ± 0.27 a Tomato 11.84 ± 1.71 b 5.49 ± 0.94 a 11.99 ± 2.46 b 17.69 ± 2.66 b 8.69 ± 1.52 a 15.69 ± 1.87 b 13.9 ± 1.3 a 7.75 ± 0.6 b 12.39 ± 1.2 c Different lowercase letters indicate a significant difference between tested parameters Vitamin C content The obtained results indicated that in raw samples of the analyzed vegetables, pepper contains the most vitamin C (2725 ± 577.2), while garlic contained the least vitamin C (137 ± 62.3). Peppers ( Capsicum annuum L.) and garlic ( Allium sativum L.) are important crops usually consumed as food. Based on our results, we can rank the most consumed crops in our territory (Slovakia) based on vitamin C content in the following order: pepper ˃ tomato ˃ potato ˃ onion ˃ garlic. Based on our results, we can state that the highest content of vitamin C was recorded in raw - uncooked samples of the monitored crops. Vitamin C content varies depending on species, variety but also on growing conditions. Vitamin C is thermolabile and significantly degradable at higher temperatures. Increased temperature and long cooking time can cause more serious losses of vitamin C. The type of vegetables, as well as the method of cooking, can have a significant effect on this decrease. Temperature is an important factor that promotes the oxidation of L-ascorbic acid to L-dehydroascorbic acid, which is converted to inactive 2,3-diketo gluconic acid due to hydrolysis and lactone ring opening [ 35 , 36 ]. During the heat treatment, the vitamin C content was lost compared to the raw samples. The recorded decrease in vitamin C content in all monitored crops compared to unheated samples was statistically significant (P < 0.05). These losses in the monitored crops ranged from 51.52–63.5%, with the lowest loss in vitamin C content recorded in potatoes and the highest loss in peppers. As another heat treatment, we used steam cooking. Steaming is a heat treatment in a space that is filled with flowing steam, most often at a temperature of 100 ° C, and it is a heat transfer in a contact manner from steam to heat-treated vegetables. Steam cooking is the most advantageous technique to prevent the loss of water-soluble compounds. Steam cooking showed a smaller decrease in vitamin C content in samples of individual vegetables compared to uncooked samples, which can be expressed in the following order: pepper (36.11%) ˃ garlic (22.62%) ˃ tomatoes (20.50%) potatoes (18.95%) > onion (16.79%). We can state that the lowest loss in the content of vitamin C after heat treatment by steaming was recorded in onions and the highest loss was recorded in peppers. The observed decrease in vitamin C content in the monitored steam-treated samples compared to unheated samples in the case of garlic and onion was not statistically significant (P < 0.05). Our findings correspond to previous research by Pellegrini et al. [ 37 ], that cooking causes greater losses in vitamin C content and is more harmful than steaming. Akdaş & Bakkalbaş [ 38 ] examined different cooking methods and concluded that the content of water-soluble phytochemicals was significantly reduced by boiling. Lee et al. [ 39 ], Duan et al. [ 40 ] evaluated the effect of different heat treatments on vitamin C content in several vegetables. The authors also reported a significant decrease in vitamin C by cooking, while steaming and microwave cooking reported smaller losses in vitamin C content. Using a minimum amount of water for cooking with a shorter cooking time should lead to fewer losses in the vitamin C content of vegetables. Buratti et al. [ 41 ], examining three methods of heat treatment (cooking, stewing, and microwaving), found that the largest losses were caused by cooking in water and the smallest losses in vitamin C content were recorded by microwave treatment. A significant decrease in the content of vitamin C in cooked vegetables is also reported by Rana et al. [ 42 ] who report that this may cause this vitamin to leach into the water. Mieszczakowska-Frąc et al. [ 43 ] state that heat losses can be 20–90% depending on the temperature level, the duration of the heat treatment as well as the contact with oxygen. As it is known that the content of vitamin C also affects the content of other nutrients [ 44 ], it is important to monitor the effect of heat treatments on the content of this vitamin as well as on the quality of final products. Statistical analysis of results determined differences between Vitamin C content in boiled garlic and raw or steamed garlic samples. For onion, differences were also determined between boiled and raw or steamed samples. For pepper, potato and tomato, differences were determined between raw and boiled, raw and steamed, and boiled and steamed samples. Total polyphenol content The analyzed vegetables are widely used as an important part of many cooked foods, but they may lose some of their biological activity during this process. Cooking can lead to many physical and chemical changes in the structure of plants. Based on our measured results, we can state that the highest values of total polyphenols were recorded in raw samples of the monitored vegetables (Table 1 .) Based on the decrease of total polyphenols by cooking vegetables in water, the monitored vegetables can be arranged in the following order: garlic (59.8%) > potato (59%) > pepper (58.6%) > onion (43.34%) ˃ tomato (29.16%). We can state that the lowest loss in the content of total polyphenols after heat treatment by cooking in water was recorded in tomatoes and the highest loss was recorded in garlic. During steam treatment, the content of total polyphenols in individual vegetables ranged from 701 ± 101.1 mg.kg − 1 to 6888 ± 739.1 mg.kg − 1 and the measured losses represented lower values (1.37–52.8%) than in cooking. The decrease in the content of polyphenols during heat treatment by steaming can be expressed in the following order: garlic (52.8%) ˃ onion (25.22%) ˃ pepper (14.98%) potato (12.9%) ˃ tomato (1.37%). Şengül et al. [ 45 ] focused on the effect of cooking, steaming, and microwaving on the total content of polyphenols in vegetables. In their study, they state that the content of total polyphenols in vegetable samples decreased by 4.09–53.39% during cooking. During steaming of vegetables, which is especially popular in Asian countries, they recorded losses of total polyphenols from 4.87 to 35.64%. During the heating of vegetables in the microwave, they recorded a slight increase in total polyphenols. Our results correspond to their study, as we also recorded significant losses in cooking and steaming individual vegetables. In their research, they point out that the degree of degradation of polyphenolic compounds depends on the processing time and the size of the vegetables. Gunathilake et al. [ 46 ] reported that for some vegetables, cooking can have an adverse effect in terms of reducing the content of total polyphenolic compounds, which in particular causes the diffusion of polyphenolic compounds into boiling water. Our results correspond to the above statement, as we recorded a reduction in the content of total polyphenols in all monitored vegetable samples. Dolinsky et al. [ 47 ] recorded 64–82% loss of polyphenolic compounds by heat treatment - steaming of vegetables. Our results correspond to the results of their measured losses of polyphenols. Wu et al. [ 48 ] reported that thermal degradation occurs during the cooking of vegetables, which causes a reduction in phytochemicals in cooked vegetables, or that a plant matrix can be softened, which increases the extractability of the phytochemicals of cooked vegetables. Prolonged cooking of vegetables changes the appearance, taste and reduces the content of total polyphenols and flavonoids. Among the main factors that affect these biologically valuable substances during cooking are the cooking time of vegetables and also the ratio of vegetables and water. The losses of polyphenolic compounds can be explained by the fact that they are polar compounds that \"leach\" into boiling water. It is important to note that the more water used in cooking, the greater the loss of total polyphenol content in vegetables during cooking. From the above, steam cooking is considered to be a more gentle heat treatment of vegetables with soluble polyphenols [ 47 ]. The reduction in the content of total polyphenol compounds after heat treatment may be related to the Maillard reaction, as polyphenol compounds are also involved in this reaction. During the Maillard reaction, the reaction products increase, and the content of polyphenolic compounds decreases [ 34 ]. Statistical analysis of results determined differences between total polyphenol content in raw and boiled, raw and steamed, and boiled and steamed garlic samples. For pepper and tomato, differences were determined between boiled and raw or steamed samples. Antioxidant activity The values of antioxidant activity (AOA) measured by three methods (DPPH, ABTS, FRAP) in the monitored vegetables at different types of heat treatment are given in Table 2 . The highest values of antioxidant activity were determined in raw samples of monitored vegetables. We recorded an increase in AOA in only two cases. It was the antioxidant activity of tomatoes after steaming (DPPH method), where we recorded a 1.26% increase in AA compared to the raw sample. We also recorded an increase in the AOA value of the onion after heat treatment by steaming (FRAP method) by 5.73%. In both cases, this slight increase was statistically insignificant (P > 0.05). This slight increase in AOA can be explained by the improved extractability and softening of the matrix by the heat treatment. During heat treatment by cooking, we recorded losses of antioxidant activity determined by the DPPH method in the range from 47.32–58.80%. Using the ABTS method, these losses ranged from 35.80-61.47%, and using the FRAP method, AOA values ranged from 32.60–58.90%. We can state that in all three methods of determining the AOA, we determined the lowest AOA losses in potatoes and the highest AOA losses were recorded in onions. We recorded lower losses of AOA values by steam treatment. Using the DPPH method, these losses ranged from 2.55–46.76%. The decrease in AOA value using the ABTS method varied in the range from 8.68–26.08% and when using the FRAP method we recorded AOA losses in the range from 8.83–33.04%. We recorded the lowest AOA losses using all three methods in peppers. The highest AOA losses in the ABTS and FRAP methods were found in potatoes, but using the DPPH method, the highest AOA loss was recorded in garlic. The influence of the method of heat treatment of vegetables on the value of antioxidant activity has been confirmed in several studies. Jiménez-Monreal et al. [ 49 ] confirmed that microwave heating leads to the lowest losses of antioxidant activity in 20 vegetables and cooking leads to the largest losses of antioxidant activity, which corresponds to the results in our work. Heat treatment of vegetables by boiling in water can cause the release of ascorbic acid or other antioxidant, water-soluble substances from the tissue into the water [ 50 ]. Decreases in antioxidant activity after cooking in tomatoes have also been reported [ 51 ]. Çubukçu et al. [ 52 ] similarly report a reduction in the AOA of onions and garlic, as the oxidation process induced by heat treatment leads to the degradation of antioxidant components. On the other hand, Managa et al. [ 53 ] reported an increase in AOA (determined by FRAP) in steamed vegetables. According to these authors, this increase could be due to the polymerization of phenols during cooking, as the polymerization of procyanidins is reported to increase antioxidant activity. The antioxidant properties of the present polyphenolic compounds also depend on the presence, number, and location of functional groups. Heat treatment can lead to a modification of the structure as well as to a change in the antioxidant activity of bioactive substances. Steaming is generally said to be one of the more economical methods of heat treatment of vegetables. Preti et al.[ 54 ], and Soares et al. [ 55 ] concluded that steam cooking is a better way to heat vegetables than cooking in water, in terms of preserving antioxidants. Similarly, Kosewski et al. [ 56 ] reported a reduction in the antioxidant potential of most of the monitored vegetables after heat treatment compared to raw vegetables. Several papers state that changes in total polyphenol content and antioxidant activity depend on the vegetables themselves, heat treatment methods, temperature but also on the type of disruption of cell structures (cutting, chopping, extrusion) as well as the amount of water used [ 48 , 57 ]. Berinyuy et al. [ 51 ] state that the significant factors influencing the losses of bioactive substances as well as the AOA values are considered to be the temperature of individual technological modifications and the time of action. Our obtained results suggest that the nutritional value as well as the functional properties (antioxidant activity) of the vegetables of interest, which are the most grown in Slovakia, can be protected by a suitable choice of cooking method. Statistical analysis of results determined differences between antioxidant activity measured by DPPH assay of raw garlic samples and boiled or steamed garlic samples. For onion, pepper, potato and tomato, differences were determined between boiled and raw or steamed samples. Statistical analysis of results determined differences between antioxidant activity measured by ABTS assay of raw garlic samples and boiled or steamed garlic samples. For potato, differences were also determined between raw and boiled or steamed samples For onion, pepper, and tomato, differences were determined between boiled and raw or steamed samples. Statistical analysis of results determined differences between antioxidant activity measured by FRAP assay of raw garlic samples and boiled garlic samples. For onion and pepper, differences were determined between boiled and raw or steamed samples. For potato, differences were determined between raw and steamed samples. For tomato, differences were determined between raw and boiled samples, raw and steamed samples, and boiled and steamed samples. As follows from the Fig. 1 and Fig. 2 , we can state that the impact of technological modifications has a statistically demonstrable effect on the change in the content of monitored bioactive substances in the crops most cultivated in Slovakia. Conclusion In this work, we focused on evaluating the content of selected bioactive substances and changes in antioxidant properties of the most consumed vegetables in Slovakia, both in raw form and after heat treatment by cooking and steaming. We can conclude that both methods of cooking affected the content of the monitored bioactive substances as well as the antioxidant activity in selected vegetables. The most significant losses of total polyphenols, vitamin C, and antioxidant activity were recorded in samples of boiled vegetables. Steam cooking can be included among those heat treatments, the use of which better preserves the original content of healthy substances in vegetables. Consumption of vegetables and especially the content of beneficial bioactive substances, the content of which can be changed by thermal treatments, can mitigate the adverse effects of some diseases of civilization. Further studies are needed to optimize the way vegetables are cooked, taking into account all factors, to gain additional knowledge in order to maintain the content of valuable health-promoting substances in the vegetables consumed. Declarations Funding This publication was supported by the Operational Program Integrated Infrastructure within the project: Demand-driven Research for the Sustainable and Innovative Food, Drive4SIFood 313011V336, cofinanced by the European Regional Development Fund. Conflict of Interest The authors declare no conflict of interest. Ethics Approval Not applicable. Consent to Participate Not applicable. Consent for Publication Not applicable Data Availability Statement The authors declare that the data supporting the findings of this study are available within the article. Author Contributions Statement The authors declare that the data supporting the findings of this study are available within the article. J.L wrote the main manuscript text and conceived of the presented idea, N.Č. performed the measurements, translated and revised manuscript, M.Š. did the statistical analysis and prepared figures, M.B verified the analytical methods, J.M. and A.V. were involved in planning and supervised the work, A.V. acquired a funding, A.B. and T.B. designed the experiments All authors reviewed the manuscript. References Cory H, Passarelli S, Szeto J, Tamez M, Mattei J (2018) The Role of Polyphenols in Human Health and Food Systems: A Mini-Review. 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Int J Food Sci Technol 43(3):560–567. https://doi.org/10.1111/j.1365-2621.2006.01504.x Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {\"props\":{\"pageProps\":{\"initialData\":{\"identity\":\"rs-1584531\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":true,\"archivedVersions\":[],\"articleType\":\"Research Article\",\"associatedPublications\":[],\"authors\":[{\"id\":102314035,\"identity\":\"d1c7b5f5-8d4a-492b-bc4c-6b75db5888e1\",\"order_by\":0,\"name\":\"Judita 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treatment\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Figure2.jpg\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-1584531/v1/5ee5f4668db1c7f1f7a834c5.jpg\"},{\"id\":21166963,\"identity\":\"166a1431-69f7-4a88-b26f-5cfbe7ae9ffa\",\"added_by\":\"auto\",\"created_at\":\"2022-05-06 15:40:30\",\"extension\":\"jpg\",\"order_by\":3,\"title\":\"Figure 3\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":114043,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eSpearman correlation - relationships between individual monitored parameters\\u003c/p\\u003e\\u003cp\\u003e\\u003cbr\\u003e\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Figure3.jpg\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-1584531/v1/8d8786296504f905da0a4d63.jpg\"},{\"id\":21166964,\"identity\":\"e1bec2d4-6e3a-4332-9761-9e22f062e0db\",\"added_by\":\"auto\",\"created_at\":\"2022-05-06 15:40:33\",\"extension\":\"pdf\",\"order_by\":0,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"manuscript-pdf\",\"size\":592606,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"manuscript.pdf\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-1584531/v1/cf880a28-3960-4ed8-a328-d3251d36bb30.pdf\"}],\"financialInterests\":\"No competing interests reported.\",\"formattedTitle\":\"The impact of heat treatments on the content of beneficial substances in the most consumed vegetables in Slovakia\",\"fulltext\":[{\"header\":\"Introduction\",\"content\":\"\\u003cp\\u003eAllium vegetables (\\u003cem\\u003eAllium\\u003c/em\\u003e L.\\u003cem\\u003e)\\u003c/em\\u003e, as well as potatoes (\\u003cem\\u003eSolanum tuberosum\\u003c/em\\u003e L.), peppers (\\u003cem\\u003eCapsicum annuum L\\u003c/em\\u003e.), and tomatoes (\\u003cem\\u003eSolanum lycopersicum L\\u003c/em\\u003e.) are commonly consumed types of vegetables in Slovakia. They are an integral part of the preparation of many meals and dishes in fresh or technologically modified form. These most cultivated and also the most consumed crops with a long tradition are characterized by a high content of biologically active phytomolecules. Optimal intake of phytochemicals and a nutritionally balanced diet supplemented with specific ingredients such as some antioxidant polyphenolic compounds play a key role in maintaining health and have the potential to reduce the risk of diseases of civilization [\\u003cspan additionalcitationids=\\\"CR2\\\" citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR3\\\" class=\\\"CitationRef\\\"\\u003e3\\u003c/span\\u003e].\\u003c/p\\u003e \\u003cp\\u003eThe genus \\u003cem\\u003eAllium\\u003c/em\\u003e, which also includes onion (\\u003cem\\u003eAllium cepa\\u003c/em\\u003e L.) and garlic (\\u003cem\\u003eAllium sativum\\u003c/em\\u003e L.), is a rich source of polyphenols. It is characterized by a high content of flavonoids such as quercetin, kaempferol, and their glycosides, phenolic acids such as β-coumaric acid, caffeic acid, and sinapic acid [\\u003cspan citationid=\\\"CR4\\\" class=\\\"CitationRef\\\"\\u003e4\\u003c/span\\u003e], anthocyanins, sulfur compounds, and saponins [\\u003cspan citationid=\\\"CR5\\\" class=\\\"CitationRef\\\"\\u003e5\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR6\\\" class=\\\"CitationRef\\\"\\u003e6\\u003c/span\\u003e]. The major organosulfur compounds in the genus \\u003cem\\u003eAllium\\u003c/em\\u003e are allylcysteines, S-alkenyl-L-cysteine ​​sulfoxides, thiosulfinates, and sulfides [\\u003cspan citationid=\\\"CR7\\\" class=\\\"CitationRef\\\"\\u003e7\\u003c/span\\u003e]. These substances are precursors of flavors and fragrances and some have antioxidant properties [\\u003cspan citationid=\\\"CR8\\\" class=\\\"CitationRef\\\"\\u003e8\\u003c/span\\u003e]. S-allylcysteine ​​sulfoxide reduces cholesterol, increases the activity of enzymes that protect against electrophilic agents, improves insulin sensitivity, and tends to increase nutrient absorption and assimilation [\\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e]. Potatoes, peppers, and tomatoes are vegetables whose general consumption in Slovakia is high and regular consumption of these crops can ensure the supply of a sufficient amount of polyphenolic substances to the human body. Polyphenols are considered to be very important antioxidants in the human diet that are able to prevent the formation of free radicals with harmful effects on health and are therefore important in reducing the risk of diseases of civilization [\\u003cspan citationid=\\\"CR10\\\" class=\\\"CitationRef\\\"\\u003e10\\u003c/span\\u003e]. Potatoes contain a number of compounds with high nutritional value, are an excellent source of energy, and contain secondary metabolites that are useful for human health [\\u003cspan citationid=\\\"CR11\\\" class=\\\"CitationRef\\\"\\u003e11\\u003c/span\\u003e]. They are considered a rich source of polyphenols. They contain polyphenols from 4 classes such as phenolic acids (chlorogenic, cryptochlorogenic and neochlorogenic, vanillic, caffeic acid), flavonols (rutin), flavan-3-ols (catechin), and anthocyanins [\\u003cspan citationid=\\\"CR12\\\" class=\\\"CitationRef\\\"\\u003e12\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR13\\\" class=\\\"CitationRef\\\"\\u003e13\\u003c/span\\u003e]. Due to its rich content of phytonutrients and bioactive substances, potatoes are considered a functional food and their consumption improves the health of the gastrointestinal tract as well as the intestines [\\u003cspan citationid=\\\"CR14\\\" class=\\\"CitationRef\\\"\\u003e14\\u003c/span\\u003e]. From an agricultural point of view, pepper is one of the most important crops, not only in Slovakia but also worldwide [\\u003cspan citationid=\\\"CR15\\\" class=\\\"CitationRef\\\"\\u003e15\\u003c/span\\u003e]. The bioactive substances found in peppers are known for their analgesic, antiobesity, cardio protective, and dietary properties. Pepper has strong anti-inflammatory effects, helps to increase the overall immunity of the body, and helps proper digestion. Due to its low-calorie content and zero fat content, pepper is an ideal supplement to the daily diet [\\u003cspan citationid=\\\"CR16\\\" class=\\\"CitationRef\\\"\\u003e16\\u003c/span\\u003e]. It contains compounds with antioxidant activity, which is attributed to the ability of these compounds to capture singlet molecular oxygen, reactive oxygen species, peroxyl radicals, and reactive nitrogen species [\\u003cspan citationid=\\\"CR15\\\" class=\\\"CitationRef\\\"\\u003e15\\u003c/span\\u003e]. Of the polyphenolic compounds, they contain phenolic acids such as vanilla, gallic, cinnamic, p-hydroxybenzoic, p-coumaric, and ferulic acids, which contribute significantly to the antioxidant activity of peppers [\\u003cspan citationid=\\\"CR17\\\" class=\\\"CitationRef\\\"\\u003e17\\u003c/span\\u003e]. Of the flavonoids, pepper contains vanillin, quercetin, rutin and luteolin [\\u003cspan citationid=\\\"CR3\\\" class=\\\"CitationRef\\\"\\u003e3\\u003c/span\\u003e]. Carotenoids represent important dyes that are also found in peppers. Capsanthin, capsorubin, zeaxanthin, β-carotene, and β-cryptoxanthin have been identified from carotenoids in peppers [\\u003cspan citationid=\\\"CR18\\\" class=\\\"CitationRef\\\"\\u003e18\\u003c/span\\u003e]. Tomatoes (\\u003cem\\u003eSolanum lycopersicum\\u003c/em\\u003e L.) are widely grown around the world and are becoming increasingly popular in both fresh and processed forms. Tomatoes are a rich source of carotenoids, 80% of which are lycopene [\\u003cspan citationid=\\\"CR19\\\" class=\\\"CitationRef\\\"\\u003e19\\u003c/span\\u003e]. This natural antioxidant is known to protect against several diseases, inhibits the growth of many cancer cells, is particularly beneficial against prostate cancer [\\u003cspan citationid=\\\"CR20\\\" class=\\\"CitationRef\\\"\\u003e20\\u003c/span\\u003e], and has antidiabetic activity [\\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e]. Phenolic compounds such as chlorogenic acid, naringin, resveratrol, and quercetin have been found in tomato peel and seeds [\\u003cspan citationid=\\\"CR21\\\" class=\\\"CitationRef\\\"\\u003e21\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR22\\\" class=\\\"CitationRef\\\"\\u003e22\\u003c/span\\u003e]. Of the phenolic acids, tomatoes are also characterized by protocatechuic acid and 2,5-dihydroxybenzoic acid [\\u003cspan citationid=\\\"CR23\\\" class=\\\"CitationRef\\\"\\u003e23\\u003c/span\\u003e]. The presence of these key antioxidants contributes greatly to the antioxidant activity of tomatoes.\\u003c/p\\u003e \\u003cp\\u003eVegetables, which are either eaten fresh or cooked before consumption, are one of the most important components of a human diet. Vegetable processing is said to significantly affect its nutritional and sensory value. Choosing the right technological operation is very important for maintaining the quality of vegetables and their products in terms of the content of healthy substances. The content of phytochemicals in vegetables depends on different technological conditions of processing, on their stability during processing, which is influenced by sensitivity and stability to oxidation, thermal degradation and is influenced by pH as well as redox potential [\\u003cspan citationid=\\\"CR9\\\" class=\\\"CitationRef\\\"\\u003e9\\u003c/span\\u003e]. Therefore, this study aimed to monitor the impact of heat treatment on the content of bioactive substances and antioxidant activity of vegetables that are most consumed in Slovakia.\\u003c/p\\u003e\"},{\"header\":\"Materials And Methods\",\"content\":\"\\u003cp\\u003eThe following plant material, chemicals, and methods were used in the study.\\u003c/p\\u003e \\u003cdiv id=\\\"Sec3\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eMaterials\\u003c/h2\\u003e \\u003cp\\u003eFive vegetables, namely tomato (\\u003cem\\u003eSolanum lycopersicum\\u003c/em\\u003e L.), pepper (\\u003cem\\u003eCapsicum annuum\\u003c/em\\u003e L.), potato (\\u003cem\\u003eSolanum tuberosum\\u003c/em\\u003e L.), onion (\\u003cem\\u003eAllium cepa\\u003c/em\\u003e L.), and garlic (\\u003cem\\u003eAllium sativum\\u003c/em\\u003e L.) were analyzed in this study.\\u003c/p\\u003e \\u003cp\\u003eAll chemicals used for all analysis; methanol (99,8%), methanol (80%), gallic acid, DPPH (2,2ʹ-diphenyl-1-picrylhydrazyl), Trolox (2,5,7,8-tetramethylchroman-2-carboxylic acid), ABTS (2,2ʹ-azino-bis (3-ethylbenzthiazoline-6-sulfonic) acid, (p.a.), TPTZ (2,4,6-tri (2-pyridyl) -s-triazine), Na\\u003csub\\u003e2\\u003c/sub\\u003eCO\\u003csub\\u003e3\\u003c/sub\\u003e, K\\u003csub\\u003e2\\u003c/sub\\u003eS\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e8\\u003c/sub\\u003e, HPLC standards (purity range 98.0\\u0026ndash;99.9%): methanol (HPLC grade), acetonitrile (gradient HPLC grade), and phosphoric acid (ACS grade) were purchased from Sigma-Aldrich (Sigma-Aldrich, USA). Double deionized water (ddH2O) was treated (0.054 \\u0026micro;S.cm\\u003csup\\u003e\\u0026minus;\\u0026thinsp;1\\u003c/sup\\u003e) in a Simplicity 185 purification system (Millipore, UK). Folin-Ciocalteau reagent used for the determination of total phenolic content was purchased from Merck (Germany).\\u003c/p\\u003e \\u003cp\\u003eExtracts were prepared by shaking 25 g of homogenized sample in 80% methanol on the Unimax 2010 horizontal shaker (Heidolph Instrument GmbH, Germany) for 12 hours. The solution were then filtered through Munktell No. 390 filtrating paper (Munktell \\u0026amp; Filtrac, Germany) and stored in the closed 50 mL vial tubes.\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec4\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eHeat treatment\\u003c/h2\\u003e \\u003cp\\u003ePotatoes, onion and garlic were peeled. From the pepper, seeds were removed. Vegetables were then chopped into smaller pieces, and underwent heat treatment.\\u003c/p\\u003e \\u003cp\\u003eFor boiling, samples were added to boiling distilled water (samples:water\\u0026thinsp;=\\u0026thinsp;1:5), and cooked for 10 minutes. For steaming, samples were steamed above boiling distilled water for 10 minutes.\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec5\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eVitamin C content\\u003c/h2\\u003e \\u003cp\\u003eVitamin C content was determined by high performance liquid chromatography (HPLC) system. Samples of raw and cooked vegetables were homogenized using Grindomix GM 2000 Retsch, 2000 rpm, for 30 sec. 5 g of homogenate was weighted and 50 mL of 3% meta-phosphoric acid (MPA) was added.\\u003c/p\\u003e \\u003cp\\u003eThe extracts were bathed for 5 minutes on ultrasonic bath Bandelin Sonorex Digitec DT 510 F, (Bandelin electronic GmbH \\u0026amp; Co, Germany), centrifuged on Hettich\\u0026reg; Universal 320/320 R centrifuge (Sigma-Aldrich, USA), and then decanted through 55 mm Whatman filter papers (Sigma-Aldrich, MO, USA). Supernatants were filtered through 0.45 \\u0026micro;M membrane filters (Millipore, MA, USA). The separations were carried out on column Cortecs 18 (C18) 2.7 \\u0026micro;m, 4.6 mm x 150 mm (Waters Corporation, MA, USA). The reverse phase of liquid chromatography method was used for the determination of vitamin C content by isocratic elution by wavelength 254 nm. The mobile phases comprise methanol and water from Purification system (Simplicity 185; Millipore SAS, Molsheim, France) which was used to provide double deionized water (ddH2O, 18.2 MΩ/cm, 20\\u0026deg;C (5:95, v/v) and volume of injection was 10 \\u0026micro;l. Temperature of the column during the analyses was adjusted at 25\\u0026deg;C and the retention times were app. 5 minutes. The peak was read at 254 nm using an UV detector and quantification was determined via external calibration against ascorbic acid.\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec6\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eTotal polyphenol content\\u003c/h2\\u003e \\u003cp\\u003eTotal polyphenol content was determined by Folin - Ciocalteau colorimetric method [\\u003cspan citationid=\\\"CR24\\\" class=\\\"CitationRef\\\"\\u003e24\\u003c/span\\u003e]. Folin \\u0026ndash; Ciocalteu phenol reagent (Merck, Germany), 20% Na\\u003csub\\u003e2\\u003c/sub\\u003eCO\\u003csub\\u003e3\\u003c/sub\\u003e (Sigma Aldrich, USA), and distilled water were used. 0.1 mL of extract was pipetted into 50 mL volumetric flask. 0.85 mL of Folin Ciocalteau reagent was added, and after 3 minutes, 5 mL of 20% Na\\u003csub\\u003e2\\u003c/sub\\u003eCO\\u003csub\\u003e3\\u003c/sub\\u003e was added. The mixture was stirred, and flask was filled with distilled water to the mark. Flasks were left for 2 hour at laboratory temperature, and then measured against blank solution at 765 nm, using Shimadzu UV/VIS scanning spectrophotometer. Total polyphenol content was expressed as mg of gallic acid equivalent in 1 kg of dry matter, based on the calibration curve (R\\u0026sup2; = 0.995)\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec7\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eAntioxidant activity using DPPH Radical Scavenging Capacity Assay\\u003c/h2\\u003e \\u003cp\\u003eAntioxidant activity was measured by DPPH radical scavenging assay [\\u003cspan citationid=\\\"CR25\\\" class=\\\"CitationRef\\\"\\u003e25\\u003c/span\\u003e]. DPPH\\u003csup\\u003e\\u0026bull;+\\u003c/sup\\u003e radical (2,2-diphenyl-1-picrylhydrazyl) (Sigma Aldrich, USA) and methanol (Sigma Aldrich, USA) were used to produce working DPPH solution. 1 mL of extract was pipetted into 3.9 mL of working DPPH solution, stirred, and left in dark. After 10 minutes, solution was measured against blank solution at nm, using Shimadzu UV/VIS scanning spectrophotometer. Antioxidant activity was expressed as mmol of Trolox equivalent in 1 kg of dry matter, based on the calibration curve (R\\u0026sup2; = 0.992).\\u003c/p\\u003e \\u003cdiv id=\\\"Sec8\\\" class=\\\"Section3\\\"\\u003e \\u003ch2\\u003eAntioxidant activity using ABTS assay\\u003c/h2\\u003e \\u003cp\\u003eAntioxidant activity was determined using ABTS assay [\\u003cspan citationid=\\\"CR26\\\" class=\\\"CitationRef\\\"\\u003e26\\u003c/span\\u003e]. ABTS\\u003csup\\u003e\\u0026bull;+\\u003c/sup\\u003e radical cation \\u0026minus;\\u0026thinsp;(2,2\\u0026prime;-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (Sigma Aldrich, USA), potassium persulfate (K\\u003csub\\u003e2\\u003c/sub\\u003eS\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e8\\u003c/sub\\u003e) (Sigma Aldrich, USA), and acetate buffer (pH\\u0026thinsp;=\\u0026thinsp;4.3) were used to produce working ABTS solution. 0.05 mL of extract was pipetted into 3 mL of ABTS solution, stirred and left in the dark. After 20 minutes, absorbance was measured against blank solution at nm, using Shimadzu UV/VIS scanning spectrophotometer. Antioxidant activity was expressed as mmol of Trolox equivalent in 1 kg of dry matter, based on the calibration curve (R\\u0026sup2; = 0.993).\\u003c/p\\u003e \\u003c/div\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec9\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eAntioxidant activity using FRAP assay\\u003c/h2\\u003e \\u003cp\\u003eAntioxidant activity was determined using the FRAP assay [\\u003cspan citationid=\\\"CR27\\\" class=\\\"CitationRef\\\"\\u003e27\\u003c/span\\u003e]. TPTZ \\u0026minus;\\u0026thinsp;(2,4,6-tris(2-pyridyl)-S-triazine) (Sigma Aldrich, USA), ferric chloride (FeCl\\u003csub\\u003e3\\u003c/sub\\u003e) (Sigma Aldrich, USA), and acetate buffer (pH\\u0026thinsp;=\\u0026thinsp;3.5) were used to produce working FRAP solution. 0.05 mL of extract was pipetted into 3 mL of FRAP solution, stirred, and left in dark. After 20 minutes, absorbance was measured against blank solution at 593 nm, using Shimadzu UV- 1800 UV/ Visible Scanning Spectrophotometer, Shimadzu, Japan.\\u003c/p\\u003e \\u003cp\\u003eAntioxidant activity was expressed as mmol of Trolox equivalent in 1 kg of dry matter, based on the calibration curve (R\\u0026sup2; = 0.996)\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec10\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eStatistical analysis\\u003c/h2\\u003e \\u003cp\\u003eAll the tested variables did not follow the normal distribution according to the Shapiro-Wilk test, therefore Kruskal-Wallis and Dunn pairwise comparison with the Bonferroni correction were performed to find the significant differences between the tested variables. The Spearman correlation test was used to analyze the relationships between the tested variables. All calculations were performed using Jamovi software (version 2.2.5) [\\u003cspan additionalcitationids=\\\"CR29 CR30 CR31 CR32\\\" citationid=\\\"CR28\\\" class=\\\"CitationRef\\\"\\u003e28\\u003c/span\\u003e\\u0026ndash;\\u003cspan citationid=\\\"CR33\\\" class=\\\"CitationRef\\\"\\u003e33\\u003c/span\\u003e].\\u003c/p\\u003e \\u003c/div\\u003e\"},{\"header\":\"Results And Discussion\",\"content\":\"\\u003cp\\u003eMost vegetables go through a severe heat treatment before consumption. Different cooking methods have a great influence on the phytochemical profile of vegetables and their biological properties [\\u003cspan citationid=\\\"CR34\\\" class=\\\"CitationRef\\\"\\u003e34\\u003c/span\\u003e]. Heat treatment of vegetables is generally considered to be largely responsible for the loss and development of undesirable color, texture, taste, and nutritional quality of food. Thermal degradation can lead to a reduction of thermolabile compounds such as vitamins C, A, E, and some polyphenols and can also affect the antioxidant activity of the vegetables consumed.\\u003c/p\\u003e \\u003cp\\u003eIn the present article, we dealt with the analysis of selected substances with a beneficial effect that are found in commonly grown as well as economically available vegetables in Slovakia, which include peppers, tomatoes, potatoes, as well as onions, and garlic. Commonly available, traditional vegetables are of great importance to many countries in the world and their consumption has a significant beneficial effect on the human body. Heat treatment is one of the various types of technological processing that is used to process food raw materials into meals. The most common methods of heat treatment are cooking, steaming, and stewing. The risk of unwanted substances is roasting, baking, frying, and grilling. As the temperature rises, some important nutrients may be lost and harmful substances may form. On the other hand, the advantages of heat treatment include microbial safety, elimination or minimization of the content of some anti-nutritional and toxic substances, as well as increased digestibility of food raw materials. In our work, we monitored changes in the content of bioactive substances by cooking and steaming.\\u003c/p\\u003e \\u003cp\\u003eVitamin C content, total polyphenol content and antioxidant activity of analyzed raw, boiled and steamed vegetables are shown in Table\\u0026nbsp;\\u003cspan refid=\\\"Tab1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003e. and Table\\u0026nbsp;\\u003cspan refid=\\\"Tab2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e.\\u003c/p\\u003e \\u003cp\\u003e \\u003cdiv class=\\\"gridtable\\\"\\u003e\\u003ctable float=\\\"Yes\\\" id=\\\"Tab1\\\" border=\\\"1\\\"\\u003e \\u003ccaption language=\\\"En\\\"\\u003e \\u003cdiv class=\\\"CaptionNumber\\\"\\u003eTable 1\\u003c/div\\u003e \\u003cdiv class=\\\"CaptionContent\\\"\\u003e \\u003cp\\u003eVitamin C content and total polyphenol content in analyzed samples\\u003c/p\\u003e \\u003c/div\\u003e \\u003c/caption\\u003e \\u003ccolgroup cols=\\\"7\\\"\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c1\\\" colnum=\\\"1\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c2\\\" colnum=\\\"2\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c3\\\" colnum=\\\"3\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c4\\\" colnum=\\\"4\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c5\\\" colnum=\\\"5\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c6\\\" colnum=\\\"6\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c7\\\" colnum=\\\"7\\\"\\u003e\\u003c/div\\u003e \\u003cthead\\u003e \\u003ctr\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c1\\\"\\u003e\\u0026nbsp;\\u003c/th\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"3\\\" nameend=\\\"c4\\\" namest=\\\"c2\\\"\\u003e \\u003cp\\u003eVitamin C (mg.kg\\u003csup\\u003e\\u0026minus;\\u0026thinsp;1\\u003c/sup\\u003e DM)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"3\\\" nameend=\\\"c7\\\" namest=\\\"c5\\\"\\u003e \\u003cp\\u003eTPC (mg GAE.kg\\u003csup\\u003e\\u0026minus;\\u0026thinsp;1\\u003c/sup\\u003e DM)\\u003c/p\\u003e \\u003c/th\\u003e \\u003c/tr\\u003e \\u003c/thead\\u003e \\u003ctbody\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eType/ Treatment\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eRaw\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003eBoiling\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003eSteaming\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003eRaw\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eBoiling\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c7\\\"\\u003e \\u003cp\\u003eSteaming\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eGarlic\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e137\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;62.3\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e66\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;21.8\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e106\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;46.4\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e1487\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;325\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e597\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;79.4\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c7\\\"\\u003e \\u003cp\\u003e701\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;101.1\\u003csup\\u003ec\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eOnion\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e786\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;342.2\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e336\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;128.4\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e654\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;295.3\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e6557\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;3207\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e3715\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;1579.4\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c7\\\"\\u003e \\u003cp\\u003e4903\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;2051.4\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003ePepper\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e2725\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;577.2\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e998\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;130.2\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e1741\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;124.8\\u003csup\\u003ec\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e8102\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;1242\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e3354\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;641.2\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c7\\\"\\u003e \\u003cp\\u003e6888\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;739.1\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003ePotato\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e691\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;68.7\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e335\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;20.3\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e560\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;31.8\\u003csup\\u003ec\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e1522\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;1114\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e623\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;357\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c7\\\"\\u003e \\u003cp\\u003e1325\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;924.3\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eTomato\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e2091\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;194.6\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e875\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;208.4\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e1662\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;170.1\\u003csup\\u003ec\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e3714\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;188\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e2631\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;231.4\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c7\\\"\\u003e \\u003cp\\u003e3663\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;377.5\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003c/tbody\\u003e \\u003c/colgroup\\u003e \\u003ctfoot\\u003e \\u003ctr\\u003e\\u003ctd colspan=\\\"7\\\"\\u003eDifferent lowercase letters indicate a significant difference between tested parameters\\u003c/td\\u003e\\u003c/tr\\u003e \\u003c/tfoot\\u003e \\u003c/table\\u003e\\u003c/div\\u003e \\u003c/p\\u003e \\u003cp\\u003e \\u003cdiv class=\\\"gridtable\\\"\\u003e\\u003ctable float=\\\"Yes\\\" id=\\\"Tab2\\\" border=\\\"1\\\"\\u003e \\u003ccaption language=\\\"En\\\"\\u003e \\u003cdiv class=\\\"CaptionNumber\\\"\\u003eTable 2\\u003c/div\\u003e \\u003cdiv class=\\\"CaptionContent\\\"\\u003e \\u003cp\\u003eAntioxidant activity of analyzed samples\\u003c/p\\u003e \\u003c/div\\u003e \\u003c/caption\\u003e \\u003ccolgroup cols=\\\"10\\\"\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c1\\\" colnum=\\\"1\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c2\\\" colnum=\\\"2\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c3\\\" colnum=\\\"3\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c4\\\" colnum=\\\"4\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c5\\\" colnum=\\\"5\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c6\\\" colnum=\\\"6\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c7\\\" colnum=\\\"7\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c8\\\" colnum=\\\"8\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c9\\\" colnum=\\\"9\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c10\\\" colnum=\\\"10\\\"\\u003e\\u003c/div\\u003e \\u003cthead\\u003e \\u003ctr\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c1\\\"\\u003e\\u0026nbsp;\\u003c/th\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"3\\\" nameend=\\\"c4\\\" namest=\\\"c2\\\"\\u003e \\u003cp\\u003eDPPH (mmol TE.kg\\u003csup\\u003e\\u0026minus;\\u0026thinsp;1\\u003c/sup\\u003e DM)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"3\\\" nameend=\\\"c7\\\" namest=\\\"c5\\\"\\u003e \\u003cp\\u003eABTS (mmol TE.kg\\u003csup\\u003e\\u0026minus;\\u0026thinsp;1\\u003c/sup\\u003e DM)\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colspan=\\\"3\\\" nameend=\\\"c10\\\" namest=\\\"c8\\\"\\u003e \\u003cp\\u003eFRAP (mmol TE.kg\\u003csup\\u003e\\u0026minus;\\u0026thinsp;1\\u003c/sup\\u003e DM)\\u003c/p\\u003e \\u003c/th\\u003e \\u003c/tr\\u003e \\u003c/thead\\u003e \\u003ctbody\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eType/ Treatment\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eRaw\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003eBoiling\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003eSteaming\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003eRaw\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eBoiling\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c7\\\"\\u003e \\u003cp\\u003eSteaming\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c8\\\"\\u003e \\u003cp\\u003eRaw\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c9\\\"\\u003e \\u003cp\\u003eBoiling\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c10\\\"\\u003e \\u003cp\\u003eSteaming\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eGarlic\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e3.4\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;1.05\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e1.56\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;0.39\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e1.81\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;0.34\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e4.17\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;1.06\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e2.36\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;0.73\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c7\\\"\\u003e \\u003cp\\u003e3.18\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;0.63\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c8\\\"\\u003e \\u003cp\\u003e3.58\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;1.22\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c9\\\"\\u003e \\u003cp\\u003e1.65\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;0.51\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c10\\\"\\u003e \\u003cp\\u003e2.52\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;0.83\\u003csup\\u003ea, b\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eOnion\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e13.7\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;6.4\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e5.64\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;3.38\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e7.8\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;4.58\\u003csup\\u003ea, b\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e18.61\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;9.57\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e7.17\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;3.49\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c7\\\"\\u003e \\u003cp\\u003e14.76\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;8.09\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c8\\\"\\u003e \\u003cp\\u003e10.82\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;5.22\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c9\\\"\\u003e \\u003cp\\u003e4.48\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;1.79\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c10\\\"\\u003e \\u003cp\\u003e11.44\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;6.42\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003ePepper\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e21.56\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;6.02\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e10.6\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;3.11\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e21.01\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;5.03\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e29.95\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;8.28\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e12.62\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;4.9\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c7\\\"\\u003e \\u003cp\\u003e27.35\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;8.7\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c8\\\"\\u003e \\u003cp\\u003e24.69\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;3.13\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c9\\\"\\u003e \\u003cp\\u003e11.26\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;4.68\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c10\\\"\\u003e \\u003cp\\u003e22.51\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;2.82\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003ePotato\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e3.36\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;0.63\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e1.77\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;0.4\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e2.92\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;0.45\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e5.75\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;1.18\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e3.69\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;1.43\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c7\\\"\\u003e \\u003cp\\u003e4.25\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;0.84\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c8\\\"\\u003e \\u003cp\\u003e2.27\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;0.86\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c9\\\"\\u003e \\u003cp\\u003e1.53\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;0.54\\u003csup\\u003ea, b\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c10\\\"\\u003e \\u003cp\\u003e1.52\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;0.27\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eTomato\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e11.84\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;1.71\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e5.49\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;0.94\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e11.99\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;2.46\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e17.69\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;2.66\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e8.69\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;1.52\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c7\\\"\\u003e \\u003cp\\u003e15.69\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;1.87\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c8\\\"\\u003e \\u003cp\\u003e13.9\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;1.3\\u003csup\\u003ea\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c9\\\"\\u003e \\u003cp\\u003e7.75\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;0.6\\u003csup\\u003eb\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c10\\\"\\u003e \\u003cp\\u003e12.39\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;1.2\\u003csup\\u003ec\\u003c/sup\\u003e\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003c/tbody\\u003e \\u003c/colgroup\\u003e \\u003ctfoot\\u003e \\u003ctr\\u003e\\u003ctd colspan=\\\"10\\\"\\u003eDifferent lowercase letters indicate a significant difference between tested parameters\\u003c/td\\u003e\\u003c/tr\\u003e \\u003c/tfoot\\u003e \\u003c/table\\u003e\\u003c/div\\u003e \\u003c/p\\u003e \\u003cdiv id=\\\"Sec12\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eVitamin C content\\u003c/h2\\u003e \\u003cp\\u003eThe obtained results indicated that in raw samples of the analyzed vegetables, pepper contains the most vitamin C (2725\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;577.2), while garlic contained the least vitamin C (137\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;62.3).\\u003c/p\\u003e \\u003cp\\u003ePeppers (\\u003cem\\u003eCapsicum annuum\\u003c/em\\u003e L.) and garlic (\\u003cem\\u003eAllium sativum\\u003c/em\\u003e L.) are important crops usually consumed as food. Based on our results, we can rank the most consumed crops in our territory (Slovakia) based on vitamin C content in the following order: pepper ˃ tomato ˃ potato ˃ onion ˃ garlic. Based on our results, we can state that the highest content of vitamin C was recorded in raw - uncooked samples of the monitored crops. Vitamin C content varies depending on species, variety but also on growing conditions. Vitamin C is thermolabile and significantly degradable at higher temperatures. Increased temperature and long cooking time can cause more serious losses of vitamin C. The type of vegetables, as well as the method of cooking, can have a significant effect on this decrease. Temperature is an important factor that promotes the oxidation of L-ascorbic acid to L-dehydroascorbic acid, which is converted to inactive 2,3-diketo gluconic acid due to hydrolysis and lactone ring opening [\\u003cspan citationid=\\\"CR35\\\" class=\\\"CitationRef\\\"\\u003e35\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR36\\\" class=\\\"CitationRef\\\"\\u003e36\\u003c/span\\u003e].\\u003c/p\\u003e \\u003cp\\u003eDuring the heat treatment, the vitamin C content was lost compared to the raw samples. The recorded decrease in vitamin C content in all monitored crops compared to unheated samples was statistically significant (P\\u0026thinsp;\\u0026lt;\\u0026thinsp;0.05). These losses in the monitored crops ranged from 51.52\\u0026ndash;63.5%, with the lowest loss in vitamin C content recorded in potatoes and the highest loss in peppers.\\u003c/p\\u003e \\u003cp\\u003eAs another heat treatment, we used steam cooking. Steaming is a heat treatment in a space that is filled with flowing steam, most often at a temperature of 100 \\u0026deg; C, and it is a heat transfer in a contact manner from steam to heat-treated vegetables. Steam cooking is the most advantageous technique to prevent the loss of water-soluble compounds.\\u003c/p\\u003e \\u003cp\\u003eSteam cooking showed a smaller decrease in vitamin C content in samples of individual vegetables compared to uncooked samples, which can be expressed in the following order: pepper (36.11%) ˃ garlic (22.62%) ˃ tomatoes (20.50%) potatoes (18.95%)\\u0026thinsp;\\u0026gt;\\u0026thinsp;onion (16.79%). We can state that the lowest loss in the content of vitamin C after heat treatment by steaming was recorded in onions and the highest loss was recorded in peppers. The observed decrease in vitamin C content in the monitored steam-treated samples compared to unheated samples in the case of garlic and onion was not statistically significant (P\\u0026thinsp;\\u0026lt;\\u0026thinsp;0.05).\\u003c/p\\u003e \\u003cp\\u003eOur findings correspond to previous research by Pellegrini et al. [\\u003cspan citationid=\\\"CR37\\\" class=\\\"CitationRef\\\"\\u003e37\\u003c/span\\u003e], that cooking causes greater losses in vitamin C content and is more harmful than steaming. Akdaş \\u0026amp; Bakkalbaş [\\u003cspan citationid=\\\"CR38\\\" class=\\\"CitationRef\\\"\\u003e38\\u003c/span\\u003e] examined different cooking methods and concluded that the content of water-soluble phytochemicals was significantly reduced by boiling. Lee et al. [\\u003cspan citationid=\\\"CR39\\\" class=\\\"CitationRef\\\"\\u003e39\\u003c/span\\u003e], Duan et al. [\\u003cspan citationid=\\\"CR40\\\" class=\\\"CitationRef\\\"\\u003e40\\u003c/span\\u003e] evaluated the effect of different heat treatments on vitamin C content in several vegetables. The authors also reported a significant decrease in vitamin C by cooking, while steaming and microwave cooking reported smaller losses in vitamin C content.\\u003c/p\\u003e \\u003cp\\u003eUsing a minimum amount of water for cooking with a shorter cooking time should lead to fewer losses in the vitamin C content of vegetables. Buratti et al. [\\u003cspan citationid=\\\"CR41\\\" class=\\\"CitationRef\\\"\\u003e41\\u003c/span\\u003e], examining three methods of heat treatment (cooking, stewing, and microwaving), found that the largest losses were caused by cooking in water and the smallest losses in vitamin C content were recorded by microwave treatment. A significant decrease in the content of vitamin C in cooked vegetables is also reported by Rana et al. [\\u003cspan citationid=\\\"CR42\\\" class=\\\"CitationRef\\\"\\u003e42\\u003c/span\\u003e] who report that this may cause this vitamin to leach into the water.\\u003c/p\\u003e \\u003cp\\u003eMieszczakowska-Frąc et al. [\\u003cspan citationid=\\\"CR43\\\" class=\\\"CitationRef\\\"\\u003e43\\u003c/span\\u003e] state that heat losses can be 20\\u0026ndash;90% depending on the temperature level, the duration of the heat treatment as well as the contact with oxygen.\\u003c/p\\u003e \\u003cp\\u003eAs it is known that the content of vitamin C also affects the content of other nutrients [\\u003cspan citationid=\\\"CR44\\\" class=\\\"CitationRef\\\"\\u003e44\\u003c/span\\u003e], it is important to monitor the effect of heat treatments on the content of this vitamin as well as on the quality of final products.\\u003c/p\\u003e \\u003cp\\u003eStatistical analysis of results determined differences between Vitamin C content in boiled garlic and raw or steamed garlic samples. For onion, differences were also determined between boiled and raw or steamed samples. For pepper, potato and tomato, differences were determined between raw and boiled, raw and steamed, and boiled and steamed samples.\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec13\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eTotal polyphenol content\\u003c/h2\\u003e \\u003cp\\u003eThe analyzed vegetables are widely used as an important part of many cooked foods, but they may lose some of their biological activity during this process. Cooking can lead to many physical and chemical changes in the structure of plants.\\u003c/p\\u003e \\u003cp\\u003eBased on our measured results, we can state that the highest values of total polyphenols were recorded in raw samples of the monitored vegetables (Table\\u0026nbsp;\\u003cspan refid=\\\"Tab1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003e.) Based on the decrease of total polyphenols by cooking vegetables in water, the monitored vegetables can be arranged in the following order: garlic (59.8%)\\u0026thinsp;\\u0026gt;\\u0026thinsp;potato (59%)\\u0026thinsp;\\u0026gt;\\u0026thinsp;pepper (58.6%)\\u0026thinsp;\\u0026gt;\\u0026thinsp;onion (43.34%) ˃ tomato (29.16%).\\u003c/p\\u003e \\u003cp\\u003eWe can state that the lowest loss in the content of total polyphenols after heat treatment by cooking in water was recorded in tomatoes and the highest loss was recorded in garlic.\\u003c/p\\u003e \\u003cp\\u003eDuring steam treatment, the content of total polyphenols in individual vegetables ranged from 701\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;101.1 mg.kg\\u003csup\\u003e\\u0026minus;\\u0026thinsp;1\\u003c/sup\\u003e to 6888\\u0026thinsp;\\u0026plusmn;\\u0026thinsp;739.1 mg.kg\\u003csup\\u003e\\u0026minus;\\u0026thinsp;1\\u003c/sup\\u003e and the measured losses represented lower values (1.37\\u0026ndash;52.8%) than in cooking.\\u003c/p\\u003e \\u003cp\\u003eThe decrease in the content of polyphenols during heat treatment by steaming can be expressed in the following order: garlic (52.8%) ˃ onion (25.22%) ˃ pepper (14.98%) potato (12.9%) ˃ tomato (1.37%).\\u003c/p\\u003e \\u003cp\\u003eŞeng\\u0026uuml;l et al. [\\u003cspan citationid=\\\"CR45\\\" class=\\\"CitationRef\\\"\\u003e45\\u003c/span\\u003e] focused on the effect of cooking, steaming, and microwaving on the total content of polyphenols in vegetables. In their study, they state that the content of total polyphenols in vegetable samples decreased by 4.09\\u0026ndash;53.39% during cooking. During steaming of vegetables, which is especially popular in Asian countries, they recorded losses of total polyphenols from 4.87 to 35.64%. During the heating of vegetables in the microwave, they recorded a slight increase in total polyphenols. Our results correspond to their study, as we also recorded significant losses in cooking and steaming individual vegetables. In their research, they point out that the degree of degradation of polyphenolic compounds depends on the processing time and the size of the vegetables. Gunathilake et al. [\\u003cspan citationid=\\\"CR46\\\" class=\\\"CitationRef\\\"\\u003e46\\u003c/span\\u003e] reported that for some vegetables, cooking can have an adverse effect in terms of reducing the content of total polyphenolic compounds, which in particular causes the diffusion of polyphenolic compounds into boiling water. Our results correspond to the above statement, as we recorded a reduction in the content of total polyphenols in all monitored vegetable samples.\\u003c/p\\u003e \\u003cp\\u003eDolinsky et al. [\\u003cspan citationid=\\\"CR47\\\" class=\\\"CitationRef\\\"\\u003e47\\u003c/span\\u003e] recorded 64\\u0026ndash;82% loss of polyphenolic compounds by heat treatment - steaming of vegetables. Our results correspond to the results of their measured losses of polyphenols. Wu et al. [\\u003cspan citationid=\\\"CR48\\\" class=\\\"CitationRef\\\"\\u003e48\\u003c/span\\u003e] reported that thermal degradation occurs during the cooking of vegetables, which causes a reduction in phytochemicals in cooked vegetables, or that a plant matrix can be softened, which increases the extractability of the phytochemicals of cooked vegetables. Prolonged cooking of vegetables changes the appearance, taste and reduces the content of total polyphenols and flavonoids. Among the main factors that affect these biologically valuable substances during cooking are the cooking time of vegetables and also the ratio of vegetables and water. The losses of polyphenolic compounds can be explained by the fact that they are polar compounds that \\\"leach\\\" into boiling water. It is important to note that the more water used in cooking, the greater the loss of total polyphenol content in vegetables during cooking. From the above, steam cooking is considered to be a more gentle heat treatment of vegetables with soluble polyphenols [\\u003cspan citationid=\\\"CR47\\\" class=\\\"CitationRef\\\"\\u003e47\\u003c/span\\u003e].\\u003c/p\\u003e \\u003cp\\u003eThe reduction in the content of total polyphenol compounds after heat treatment may be related to the Maillard reaction, as polyphenol compounds are also involved in this reaction. During the Maillard reaction, the reaction products increase, and the content of polyphenolic compounds decreases [\\u003cspan citationid=\\\"CR34\\\" class=\\\"CitationRef\\\"\\u003e34\\u003c/span\\u003e].\\u003c/p\\u003e \\u003cp\\u003eStatistical analysis of results determined differences between total polyphenol content in raw and boiled, raw and steamed, and boiled and steamed garlic samples. For pepper and tomato, differences were determined between boiled and raw or steamed samples.\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec14\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003eAntioxidant activity\\u003c/h2\\u003e \\u003cp\\u003eThe values of antioxidant activity (AOA) measured by three methods (DPPH, ABTS, FRAP) in the monitored vegetables at different types of heat treatment are given in Table\\u0026nbsp;\\u003cspan refid=\\\"Tab2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e. The highest values of antioxidant activity were determined in raw samples of monitored vegetables. We recorded an increase in AOA in only two cases. It was the antioxidant activity of tomatoes after steaming (DPPH method), where we recorded a 1.26% increase in AA compared to the raw sample. We also recorded an increase in the AOA value of the onion after heat treatment by steaming (FRAP method) by 5.73%. In both cases, this slight increase was statistically insignificant (P\\u0026thinsp;\\u0026gt;\\u0026thinsp;0.05). This slight increase in AOA can be explained by the improved extractability and softening of the matrix by the heat treatment.\\u003c/p\\u003e \\u003cp\\u003eDuring heat treatment by cooking, we recorded losses of antioxidant activity determined by the DPPH method in the range from 47.32\\u0026ndash;58.80%. Using the ABTS method, these losses ranged from 35.80-61.47%, and using the FRAP method, AOA values ranged from 32.60\\u0026ndash;58.90%. We can state that in all three methods of determining the AOA, we determined the lowest AOA losses in potatoes and the highest AOA losses were recorded in onions. We recorded lower losses of AOA values by steam treatment.\\u003c/p\\u003e \\u003cp\\u003eUsing the DPPH method, these losses ranged from 2.55\\u0026ndash;46.76%. The decrease in AOA value using the ABTS method varied in the range from 8.68\\u0026ndash;26.08% and when using the FRAP method we recorded AOA losses in the range from 8.83\\u0026ndash;33.04%. We recorded the lowest AOA losses using all three methods in peppers. The highest AOA losses in the ABTS and FRAP methods were found in potatoes, but using the DPPH method, the highest AOA loss was recorded in garlic.\\u003c/p\\u003e \\u003cp\\u003eThe influence of the method of heat treatment of vegetables on the value of antioxidant activity has been confirmed in several studies. Jim\\u0026eacute;nez-Monreal et al. [\\u003cspan citationid=\\\"CR49\\\" class=\\\"CitationRef\\\"\\u003e49\\u003c/span\\u003e] confirmed that microwave heating leads to the lowest losses of antioxidant activity in 20 vegetables and cooking leads to the largest losses of antioxidant activity, which corresponds to the results in our work. Heat treatment of vegetables by boiling in water can cause the release of ascorbic acid or other antioxidant, water-soluble substances from the tissue into the water [\\u003cspan citationid=\\\"CR50\\\" class=\\\"CitationRef\\\"\\u003e50\\u003c/span\\u003e]. Decreases in antioxidant activity after cooking in tomatoes have also been reported [\\u003cspan citationid=\\\"CR51\\\" class=\\\"CitationRef\\\"\\u003e51\\u003c/span\\u003e]. \\u0026Ccedil;ubuk\\u0026ccedil;u et al. [\\u003cspan citationid=\\\"CR52\\\" class=\\\"CitationRef\\\"\\u003e52\\u003c/span\\u003e] similarly report a reduction in the AOA of onions and garlic, as the oxidation process induced by heat treatment leads to the degradation of antioxidant components. On the other hand, Managa et al. [\\u003cspan citationid=\\\"CR53\\\" class=\\\"CitationRef\\\"\\u003e53\\u003c/span\\u003e] reported an increase in AOA (determined by FRAP) in steamed vegetables. According to these authors, this increase could be due to the polymerization of phenols during cooking, as the polymerization of procyanidins is reported to increase antioxidant activity. The antioxidant properties of the present polyphenolic compounds also depend on the presence, number, and location of functional groups. Heat treatment can lead to a modification of the structure as well as to a change in the antioxidant activity of bioactive substances. Steaming is generally said to be one of the more economical methods of heat treatment of vegetables.\\u003c/p\\u003e \\u003cp\\u003ePreti et al.[\\u003cspan citationid=\\\"CR54\\\" class=\\\"CitationRef\\\"\\u003e54\\u003c/span\\u003e], and Soares et al. [\\u003cspan citationid=\\\"CR55\\\" class=\\\"CitationRef\\\"\\u003e55\\u003c/span\\u003e] concluded that steam cooking is a better way to heat vegetables than cooking in water, in terms of preserving antioxidants. Similarly, Kosewski et al. [\\u003cspan citationid=\\\"CR56\\\" class=\\\"CitationRef\\\"\\u003e56\\u003c/span\\u003e] reported a reduction in the antioxidant potential of most of the monitored vegetables after heat treatment compared to raw vegetables. Several papers state that changes in total polyphenol content and antioxidant activity depend on the vegetables themselves, heat treatment methods, temperature but also on the type of disruption of cell structures (cutting, chopping, extrusion) as well as the amount of water used [\\u003cspan citationid=\\\"CR48\\\" class=\\\"CitationRef\\\"\\u003e48\\u003c/span\\u003e, \\u003cspan citationid=\\\"CR57\\\" class=\\\"CitationRef\\\"\\u003e57\\u003c/span\\u003e]. Berinyuy et al. [\\u003cspan citationid=\\\"CR51\\\" class=\\\"CitationRef\\\"\\u003e51\\u003c/span\\u003e] state that the significant factors influencing the losses of bioactive substances as well as the AOA values are considered to be the temperature of individual technological modifications and the time of action. Our obtained results suggest that the nutritional value as well as the functional properties (antioxidant activity) of the vegetables of interest, which are the most grown in Slovakia, can be protected by a suitable choice of cooking method.\\u003c/p\\u003e \\u003cp\\u003eStatistical analysis of results determined differences between antioxidant activity measured by DPPH assay of raw garlic samples and boiled or steamed garlic samples. For onion, pepper, potato and tomato, differences were determined between boiled and raw or steamed samples.\\u003c/p\\u003e \\u003cp\\u003eStatistical analysis of results determined differences between antioxidant activity measured by ABTS assay of raw garlic samples and boiled or steamed garlic samples. For potato, differences were also determined between raw and boiled or steamed samples For onion, pepper, and tomato, differences were determined between boiled and raw or steamed samples.\\u003c/p\\u003e \\u003cp\\u003eStatistical analysis of results determined differences between antioxidant activity measured by FRAP assay of raw garlic samples and boiled garlic samples. For onion and pepper, differences were determined between boiled and raw or steamed samples. For potato, differences were determined between raw and steamed samples. For tomato, differences were determined between raw and boiled samples, raw and steamed samples, and boiled and steamed samples.\\u003c/p\\u003e \\u003cp\\u003eAs follows from the Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003e and Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e, we can state that the impact of technological modifications has a statistically demonstrable effect on the change in the content of monitored bioactive substances in the crops most cultivated in Slovakia.\\u003c/p\\u003e\\u003c/div\\u003e\"},{\"header\":\"Conclusion\",\"content\":\"\\u003cp\\u003eIn this work, we focused on evaluating the content of selected bioactive substances and changes in antioxidant properties of the most consumed vegetables in Slovakia, both in raw form and after heat treatment by cooking and steaming. We can conclude that both methods of cooking affected the content of the monitored bioactive substances as well as the antioxidant activity in selected vegetables. The most significant losses of total polyphenols, vitamin C, and antioxidant activity were recorded in samples of boiled vegetables. Steam cooking can be included among those heat treatments, the use of which better preserves the original content of healthy substances in vegetables. Consumption of vegetables and especially the content of beneficial bioactive substances, the content of which can be changed by thermal treatments, can mitigate the adverse effects of some diseases of civilization. Further studies are needed to optimize the way vegetables are cooked, taking into account all factors, to gain additional knowledge in order to maintain the content of valuable health-promoting substances in the vegetables consumed.\\u003c/p\\u003e\"},{\"header\":\"Declarations\",\"content\":\"\\u003cp\\u003e\\u003cstrong\\u003eFunding\\u0026nbsp;\\u003c/strong\\u003eThis publication was supported by the Operational Program Integrated Infrastructure within the project: Demand-driven Research for the Sustainable and Innovative Food, Drive4SIFood 313011V336, cofinanced by the European Regional Development Fund.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eConflict of Interest\\u003c/strong\\u003e The authors declare no conflict of interest. \\u0026nbsp;\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eEthics Approval\\u003c/strong\\u003e Not applicable.\\u0026nbsp;\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eConsent to Participate\\u003c/strong\\u003e Not applicable.\\u0026nbsp;\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eConsent for Publication\\u003c/strong\\u003e Not applicable\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eData Availability Statement\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eThe authors declare that the data supporting the findings of this study are available within the article.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eAuthor Contributions Statement\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eThe authors declare that the data supporting the findings of this study are available within the article.\\u003c/p\\u003e\\n\\u003cp\\u003eJ.L wrote the main manuscript text and \\u0026nbsp;conceived of the presented idea, N.Č. performed the measurements, translated and revised manuscript, M.\\u0026Scaron;. did the statistical analysis and prepared figures, M.B verified the analytical methods, J.M. and A.V. were involved in planning and supervised the work, A.V. acquired a funding, A.B. and T.B. designed the experiments\\u003c/p\\u003e\\n\\u003cp\\u003eAll authors reviewed the manuscript.\\u003c/p\\u003e\"},{\"header\":\"References\",\"content\":\"\\u003col\\u003e\\u003cli\\u003e\\u003cspan\\u003eCory H, Passarelli S, Szeto J, Tamez M, Mattei J (2018) The Role of Polyphenols in Human Health and Food Systems: A Mini-Review. 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Int J Food Sci Technol 43(3):560\\u0026ndash;567. \\u003cspan class=\\\"ExternalRef\\\"\\u003e\\u003cspan class=\\\"RefSource\\\"\\u003ehttps://doi.org/10.1111/j.1365-2621.2006.01504.x\\u003c/span\\u003e\\u003cspan address=\\\"10.1111/j.1365-2621.2006.01504.x\\\" targettype=\\\"DOI\\\" class=\\\"RefTarget\\\"\\u003e\\u003c/span\\u003e\\u003c/span\\u003e\\u003c/span\\u003e\\u003c/li\\u003e\\u003c/ol\\u003e\"}],\"fulltextSource\":\"\",\"fullText\":\"\",\"funders\":[],\"hasAdminPriorityOnWorkflow\":false,\"hasManuscriptDocX\":true,\"hasOptedInToPreprint\":true,\"hasPassedJournalQc\":\"\",\"hasAnyPriority\":false,\"hideJournal\":true,\"highlight\":\"\",\"institution\":\"\",\"isAcceptedByJournal\":false,\"isAuthorSuppliedPdf\":false,\"isDeskRejected\":\"\",\"isHiddenFromSearch\":false,\"isInQc\":false,\"isInWorkflow\":false,\"isPdf\":false,\"isPdfUpToDate\":true,\"isWithdrawnOrRetracted\":false,\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"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\":\"heat treatment, vegetables, vitamin C, total polyphenols, antioxidant activity\",\"lastPublishedDoi\":\"10.21203/rs.3.rs-1584531/v1\",\"lastPublishedDoiUrl\":\"https://doi.org/10.21203/rs.3.rs-1584531/v1\",\"license\":{\"name\":\"CC BY 4.0\",\"url\":\"https://creativecommons.org/licenses/by/4.0/\"},\"manuscriptAbstract\":\"\\u003cp\\u003eIn the present study, we investigated the effects of heat treatment (boiling in water, steaming) on ​​changes in the content of vitamin C, total polyphenols, and changes in antioxidant activity in garlic, onion, pepper, potatoes, and tomatoes. In the obtained extracts of the mentioned raw and heat-treated vegetables, we determined the content of vitamin C by HPLC, the content of total polyphenols by Folin- Ciocalteau colorimetric method, as well as the antioxidant activity (DPPH assay, ABTS assay, FRAP assay). The obtained results showed that the content of vitamin C, as well as the content of total polyphenols in the monitored vegetables after heat treatment (cooking in water), was significantly reduced (P\\u0026thinsp;\\u0026lt;\\u0026thinsp;0.05) compared to the content of these bioactive substances in raw vegetables. A slight decrease in vitamin C and total polyphenol content was recorded in the steamed samples. This decrease was not statistically significant for all these crops. Determination of antioxidant activity again showed a more significant decrease in antioxidant activity values (P\\u0026thinsp;\\u0026lt;\\u0026thinsp;0.05) (DPPH, ABTS, FRAP) after boiling in water than after steaming. The heat treatment has a significant impact on the change in the content of monitored bioactive substances in the analyzed vegetables. Based on our achieved results, steaming appears to be a more gentle way in terms of preserving natural antioxidants, which can significantly contribute to the elimination of oxidative stress in our organism.\\u003c/p\\u003e\",\"manuscriptTitle\":\"The impact of heat treatments on the content of beneficial substances in the most consumed vegetables in Slovakia\",\"msid\":\"\",\"msnumber\":\"\",\"nonDraftVersions\":[{\"code\":1,\"date\":\"2022-05-06 15:35:28\",\"doi\":\"10.21203/rs.3.rs-1584531/v1\",\"editorialEvents\":[{\"type\":\"communityComments\",\"content\":0}],\"status\":\"published\",\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"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\":\"973ec018-3a5e-4b8b-b33c-9cbece19cf35\",\"owner\":[],\"postedDate\":\"May 6th, 2022\",\"published\":true,\"recentEditorialEvents\":[],\"rejectedJournal\":[],\"revision\":\"\",\"amendment\":\"\",\"status\":\"posted\",\"subjectAreas\":[],\"tags\":[],\"updatedAt\":\"2022-05-06T15:35:29+00:00\",\"versionOfRecord\":[],\"versionCreatedAt\":\"2022-05-06 15:35:28\",\"video\":\"\",\"vorDoi\":\"\",\"vorDoiUrl\":\"\",\"workflowStages\":[]},\"version\":\"v1\",\"identity\":\"rs-1584531\",\"journalConfig\":\"researchsquare\"},\"__N_SSP\":true},\"page\":\"/article/[identity]/[[...version]]\",\"query\":{\"redirect\":\"/article/rs-1584531\",\"identity\":\"rs-1584531\",\"version\":[\"v1\"]},\"buildId\":\"WrCJVZZCHTDjtuVLN7oU0\",\"isFallback\":false,\"isExperimentalCompile\":false,\"dynamicIds\":[84888],\"gssp\":true,\"scriptLoader\":[]}","source_license":"CC-BY-4.0","license_restricted":false}