Food Technology
Elham Ahmadi; Sara Panahi; Amirhossein Karimzadeh; Hamed Hassanzadeh; Mohammadyar Hosseini
Abstract
IntroductionIn recent years, with increasing concerns about food safety and environmental issues related to waste generated by non-degradable plastic packaging, study on novel biodegradable packaging materials has attracted the attention of researchers. Active packaging based on biopolymers, which offers ...
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IntroductionIn recent years, with increasing concerns about food safety and environmental issues related to waste generated by non-degradable plastic packaging, study on novel biodegradable packaging materials has attracted the attention of researchers. Active packaging based on biopolymers, which offers a sustainable and environmentally friendly way to improve food shelf life, considered one of such packaging technologies. Edible coatings and films, are a thin layer of edible compounds and biopolymers applied on the surface of foodproducts that play important role to control physicochemical, microbial and physiological changes in food. Gelatin is obtained from partial degradation of collagen. Due to its availability, relatively cheap price, biodegradability and good properties such as its excellent ability to form a film and reduce the transfer of oxygen, oil and moisture, it is highly regarded as an edible film and has antimicrobial and antioxidant activity. In general, the gelatin film showed high water absorption due to the presence of several hydrophilic groups, which may weaken the mechanical properties and water vapor transport of the film. For this reason, the combination of gelatin with other biopolymers such as chitosan, starch and gum is a suitable method to eliminate the drawbacks of gelatin-based films.Materials and MethodsTo prepare the composite film of the four formulations studied in this research, gelatin powder (3% by weight/volume of water) and glycerol (30% by weight/volume of gelatin powder) were added to deionized water and magnetically stirred for 10 minutes at 2400 RPM. To prepare an aqueous suspension of carboxymethyl cellulose, powder (CMC 2% by weight/volume of water) and glycerol (30% by weight/weight of carboxymethyl cellulose powder) were mixed with deionized water. This suspension was heated to boiling temperature and kept at this temperature for 15 minutes and then kept for 30 minutes at 90°C water bath and stirred. The G/CMC coating was also prepared by dissolving 40 grams of gelatin, 10 grams of carboxymethyl cellulose and glycerol (30% by weight/weight of polymer materials) in one liter of water. The mixture was stirred for 1 hour at 60 degrees Celsius. The mixture was then dried at 25-35 degrees Celsius. Different concentrations of the extract (0, 0.5, 0.75, 1.5 and 3.25%) were added to the mixture and stirred for 2 minutes. In the next step, the mixture was added to a plastic Petri dish with a diameter of 15 cm and placed under a vacuum hood for 1 hour. Then it was transferred to a fan oven and kept for 20 hours. In the final stage, the dried films were placed in a desiccator at room temperature for testing. The effect of different concentrations of Dorema aucheri extract for the production of edible films on the physicochemical, mechanical, antioxidant and antimicrobial properties was analyzed with one-way analysis of variance (ANOVA) and comparing the average data was performed based on Duncan's multi-range test using SPSS26 software at probability level of 0.05.Results and DiscussionThe highest tensile strength and elongation at break point and Young's modulus in the treatment was 1.5%. In all concentrations, solubility and permeability were significant (p<0.05). The lowest solubility was observed in the control. The highest permeability and turbidity were observed in the treatment of 1.5% Dorema aucheri extract. In all edible film treatments, the antioxidant property using DPPH radicals was significant (p<0.05). The results of the evaluation of the antimicrobial activity of the film with the help of diffusion discs showed that the maximum diameter of the inhibition halo in the concentration of 3.25% was related to Escherichia coli with an average halo diameter of 5.33 mm. Average halo diameter for Pseudomonas aeruginosaand Staphylococcus aureus was reported as 4 mm and 3.99 mm, respectively. The overall results showed that the addition of Dorema aucheri extract at a concentration of 1.5% produced films that, in addition to inhibiting the growth and proliferation of bacteria, have strength and can be used for perishable food.
Food Technology
Mahya Hosseinzadeh; Mohammadyar Hosseini; Mohammad Shahedi; Mehdi Kadivar
Abstract
IntroductionThe most important component of wheat proteins is gluten, and the most prominent bonds in gluten are disulfide bonds, which bind glutenin subunits. Therefore, oxidizing and reducing agents with great effects on the thiol-disulfide system of the dough can change the mechanical and rheological ...
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IntroductionThe most important component of wheat proteins is gluten, and the most prominent bonds in gluten are disulfide bonds, which bind glutenin subunits. Therefore, oxidizing and reducing agents with great effects on the thiol-disulfide system of the dough can change the mechanical and rheological properties of the dough. Due to the positive effects of ascorbic acid on the properties of the dough, it is used as a flour improver. To weaken the structure of the dough, reducing agents such as cysteine-L can be used, and by adding organic acids, increasing the specific volume and decreasing the moisture, the pH and hardness are observed in comparison with the control. This study is performed to evaluate the effect of adding reducing compounds, vitamin C and organic acids during the conditioning of wheat and their effect on the yield of the resulting pulp.Materials and MethodsFirst, Physical properties of wheat include: specific density, colorimetry, estimation of grain length, width and thickness, grain hardness, hectoliters, 1000-grain weight, grain moisture, degree of extraction were measured for the tested wheat. Moisture, pH, ash, particle size, fat, protein and zeal number tests were performed on wheat flour. From elementary cleaned and weighed wheat, 13 samples of 240 g each were weighed separately and poured into plastic bottles. One sample was conditioned with only 30 ml of distilled water and the other 12 samples were conditioned with the following solutions, respectively:1- Cysteine solution at three levels of 0.25, 0.5 and 0.75% by weight2- Citric acid solution in three levels of 0.3, 0.4 and 0.5% by weightVitamin C solution in three levels of 100, 150 and 200 ppm4- solution of 80 ppm vitamin C and 0.1% cysteine, solution of 100 ppm vitamin C and 0.2% cysteine, solution of 120 ppm vitamin C and 0.3% cysteineAfter 24 hours, the conditioned wheat samples were milled by a laboratory waltz mill, and then subsequent tests including gluten, sulfhydryl-disulfide, glutathione, and solvent retention capacity (SRC) were performed on the samples.Statistical analysis was performed using SAS statistical software in a randomized complete block design. Each measurement was performed in at least three replications and the means were compared at 95% confidence level with the least significant difference in LSD.Results and DiscussionThe results of physical tests on wheat grain and chemical tests on flour obtained by milling the wheat samples without adding additives during conditioning are presented in tables. The results of gluten, glutathione, sulfhydryl-disulfide and solvent storage capacity tests on samples of conditioned wheat flours are also presented. Based on the results of gluten and glutathione test, it was shown that ascorbic acid is oxidizing and strengthening the dough, but cysteine is reducing and weakening the dough. Simultaneous addition of cysteine and ascorbic acid strengthened the dough, adding citric acid to certain level strengthened the dough as exhibited in the gluten test. However, byond that level, weakened the dough, but in the glutathione test it was almost ineffective. The results of sulfhydryl-disulfide test showed that increasing the amount of vitamin C at three levels of 100, 150 and 200 ppm increases the number of disulfide bonds, although this increase was not in linear trend, which can be due to the limited number of groups of sulfhydryl with a suitable spatial arrangement for oxidation. Accordingly, the number of sulfhydryl groups is significantly reduced, although it does not reach zero. With the addition of reducing cysteine, the opposite trend was the case, as the number of thiol groups increased, the number of disulfide bonds and bridges decreased. The addition of organic acid had no significant effect on both parameters and showed that the performance of these two variables is independent. By adding both reducing and oxidizing compounds, it was found that the oxidizing effect of vitamin C is far greater than the reducing effect of cysteine. Regarding the solvent retention capacity test performed with 4 solvents of deionized water, 50% sucrose, 5% sodium carbonate and 5% lactic acid, the expected results are that the addition of cysteine has a reducing and weakening effect on the dough, adding vitamin C and cysteine + vitamin C strengthens the dough and the addition of citric acid initially strengthens the dough, but by increasing its level weakens the dough, but this effect is small and can beneglected . The results obtained by comparing the samples conditioned with cysteine, vitamin C, citric acid and cysteine + vitamin C, with the sample conditioned with distilled water in some additive levels matched the expected results, but in some cases did not.
