IRANIAN JOURNAL OF FOOD SCIENCE AND TECHNOLOGY
Year:2013 | Volume:10 | Issue:40|Papers Count:16

In present study, the chemical (ash, protein, fat, minerals, and pH) and functional (ability in stabilizing emulsions and producing edible films) properties of the soluble and insoluble fractions of Persian gum were evaluated. The O/W emulsions were prepared using the soluble fraction at various concentrations vs. oil content. In order to prepare edible films, the soluble and insoluble fractions as well as whole gum were used at constant concentration (3 w/v%) in the presence of glycerol (up to 8 wt% based on the gum weight) at pH 8. According to the findings, the Persian gum was consisted of 70 and 30 wt% of insoluble and soluble fractions respectively, where their protein content was negligible (0.062 and 0.146 wt%). The emulsion E4 containing 2 w/v% of soluble fraction and 1 w/v% of oil had the maximum (~99% at room temperature) emulsifying stability index (ESI) up to 5 weeks which was even higher than gum Arabic as control. Moreover, these findings were proven by the optical density and particle size distribution data. In terms of film ability, our findings showed that the edible film containing 3 w/v% of soluble fraction and 4 w/w% of glycerol at pH 8 had the most acceptable characteristics regarding appearance and mechanical properties.

In this study, effects of freezing and two thawing methods on food quality of Persian sturgeon fillets (Acipenser persicus) were evaluated. Fresh Persian sturgeon fillets kept frozen at -20oC up to 4 months, and then thawed by two different thawing methods (in a microwave oven and in a refrigerator at 4oC). Freezing- thawing increased fat and decreased protein, moisture and ash contents. Thawing in microwave resulted in less decrease in moisture content compared to refrigerator thawing and caused an increase in protein content. Protein solubility decreased after freezing- thawing but it was significant only in few pHs (in both thawing methods).4 months frozen storage and then defrosting resulted in a decrease in –SH group content. The microbial count increased after freezing and thawing (p<0.05), however the increase was less after microwave thawing. Both thawing methods showed higher L* and b* values and smaller a* value compared to control sample (P<0.05).

This study was conducted to evaluate of the histamine levels in tuna samples by ELISA method used in cannery factories. For this purpose, three cannery factories (A, B and C) in Qazvin province were studied. Total of 96 samples were collected and examined. The results showed that all samples had histamine and the range of histamine value was different in all samples of three cannery factories. The range of histamine in the factories were 14.26-144.15, 19.47-127.75 and 30.79-75.46, respectively (A, B and C). Also based on results, histamine levels 76.11%, 57.3% samples (related to A and B respectively) were above the Standard level, While samples with histamine content above standard limit not detected on the cannery factory C. Ultimately, 5.11% of samples showed the histamine levels higher than the standard limit.

Yog-ice cream (frozen yogurt), is a kind of frozen desserts which has similar features with ice cream in physical and apparent characteristics. In this study, frozen yogurt was produced as a synbiotic product containing both probiotics and prebiotics. Lactobacillus Casei (LAFTI-L26) as a probiotic bacteria was added to low fat frozen yogurt in two types, free and encapsulated, and its survivability was evaluated during 30 days storage at -18oc.Prebiotic compound that was used in this study, was Inulin that added to frozen yogurt in different levels (0, 2.5 and 5% w/w). The viable cell number of L.casei in the free state in prepared low fat frozen yogurt mixture, was between 9.801-9.779 log cfu/ml at the first day, and after 30 days storage at -18oc, its viable number redused to 7.451-7.866 log cfu/ml. In samples of frozen yogurt containing L.casei that was encapsulated by sodium alginate whey protein concentration (wpc), the viable cell number of L.casei was 8.150-8.661 log cfu/ml at the first day that reduced to 6.650-7.477 log cfu/ml at the end of 30 days storage at -18oc.Totally , obtained results showed that encapsulation of lactobacillus casei in Alginate-Whey protein capsules, could significantly improve survivability of L.casei. (p<0.05) that the viable number of this bacteria in frozen yogurt containing encapsulated probiotic, was in the range of investigated levels by the International Dairy Federation (106-107 cfu/g).

In order to evaluate a few effective factors on traditional breads wastage in Zanjan, 30 bakeries of this town were randomly selected. With direct referring to bakeries and filling out the related forms, and evaluation the quality of used flour samples, it turned out that although 56.67 percent of bakers in this town, had over 20 year experience, almost none of them, had any scientific information on bread-making that has important factor in reducing bread wastage. About the important factors in bread-making, the results showed that almost all of the bakers, use of sourdough included with bakery yeast for fermentation but, only about 10 percent of the bakeries, considered the proper fermentation time. The results of bread baking revealed that about 57 percent of the bread baking machine had over the age of 15 years, this suggests that the machines are overused and they needs to be replaced. Overall, the amount of waste traditional breads of Zanjan, is calculated about 25.79 percent, which is remarkable, and much of it is includes Lavash bread (17.27 percent). Protein quantity and quality results of tested flour samples showed that the flour used in bakeries of Zanjan contain low level of protein (9.5 percent), and Zeleny and farynograph tests also indicates low protein quality of these samples.

Fermentation process of bread includes primary, middle and final sections. If dough is prepared by the traditional methods and immediately formed, in addition to the more energy consumption, the proper shape of dough will be affected and final product may have compressed texture, less porosity and specific volume and lower flavor and taste scores. Where the three section of fermentation performed, because of equal distribution of gas, more elasticity and formation and aromatic compound, the product has more porosity and taste and flavor. By considering the importance of this issue, the purpose of this study was the effect of primary fermentation time in three levels of 10, 15 and 20 minute, middle fermentation time on three levels of 5, 10 and 15 minute and final fermentation time on three levels of 25, 35 and 45 minute on crumb firmness, porosity, specific volume and sensory properties of Barbari bread. After comparing treatment with fully randomized factorial in p<0.05, the results showed the lowest firmness, the highest porosity and specific volume and the best score in sensory analysis was attribute to samples with primary fermentation time of 30 minute and final fermentation time of 45 minute. As compared to these treatments the greatest effect on improving the quality of Barbari bread was attributing to the sample with middle fermentation time of 10 minute.

The aim of this study was to compare the stability of chemical and physical characteristics of non-fat set yoghurt containing textured milk to those of non-fat and full fat set yoghurt during 14 days storage at 4±1oC. In order to produce non-fat yoghurt containing textured milk, the temperature of heated skim milk (85-90oC for 30-35 minutes) was reduced to 42-43oC and it was combined with 0, 10, 20, 30, 40 and 50 percent of textured milk. The chemical (pH, titratable acidity, protein, fat and total solid) and physical (colorimetrics, syneresis and water holding capacity) experiments were carried on non fat yoghurt containing textured milk, non-fat and full fat yoghurt during the first, seventh and fourteenth day of storage time in refrigerator. The results revealed that textured milk had no effect on the pH, titratable acidity, protein and fat content of yoghurts, but the storage time affected these factors (p<0.05), textured milk and storage time affected the amount of total solid in samples. Textured milk improved colorimetrics, syneresis and water holding capacity of yoghurts compared to non-fat yoghurt and this was observed during storage time too. The sample containing 30% of textured milk was the most similar one to the full fat yoghurt, so this yoghurt formulation is recommended to gain appropriate physical and chemical characteristics.

This project was carried out in order to Study of possibity of uses from Grape seed extract for prevention of melanosis in cultured shrimp and its instead to synthethic matterial. Treatments including of Grape seed extract processed with 10g/l concentration and control samples. The samples were kept at -18oC. Chemical and sensory examinations were carried out for a period of six months. No statistically significant difference was observed in peroxide value and free faty acids in test samples compared with the control samples during storage period (P>0.05). No statistically significant difference was observed in thiobarbotouric acid and pH in test and control samples during storage period (P>0.05). TVN (Total Volatile Nitrogen) and trimetylamin factors were decreased in test samples compared with control samples. Statistically significant difference was observed in TVN, moisture and trimetylamin in test and control samples during storage period (P<0.05). No statistically significant difference was observed in colour and melanosis in test samples compared with control samples during storage period (P>0.05). No statistically significant difference was observed in Humidity, protein, lipid and ash in test samples compared with the control samples (P>0.05).Test samples had better quality compared with the control samples. The covered samples had a favorable quality until the end of storage period. But, the control samples had a favorable quality for a period of 20 days.

Recently, tend to replacing membrane processing to conventional refining of vegetable oil has been developed. Ultrafiltration was conducted by a flat sheet PVDF membrane with two different MWCOs (50 KDa, M116, and 100 KDa, M183) at various temperatures and pressures (25–55oC and 2-5 bar). Monitoring of the primary and secondary oxidation products showed that the rejection of peroxides was more through the M183 membrane. In contrast, the M116 membrane was more effective in removing the conjugated dienes and carbonyl compounds. Also, results described that membrane processing was efficient at rejection of total polar compounds comparing in conventional refining.

In this research, we studied isolation of the cellulolitic fungi from the persimmon tree, grapevine, pomegranate tree and walnut soils. Among of them, persimmon soil was selected because of maximum cellulolitic fungi. Seven fungi werw isolated from persimmon soil, which three of them had suitable cellulose activity and they were identificated by 18S rRNA and named: Aspergillus niger MZM 89-a2, Penicillium decumbens ZHE 89-p3, Penicillium decumbens MMH 89-p1. Cellulase activities of these fungi were respectively (U/d): FPA 3.1671, 3.5740, 3.1812 and Avicelase 1.6605, 0.3869, 1.1451 and CMCase 2.950, 0.2644, 0.4604. Response surface activity (RSM) was studied to evaluate the effects of temperature, moisture content and particle size for FPA by Aspergillus niger MZM 89-a2. The optimum FPA was in temperature, moisture content and particle size respectively: 28.49oC, 66.62٪ and 1.5-2 (mm). The maximum predicted FPA was 4.35 (U/g) and obtained FPA under this condition was 4.42 (U/g), which indicates the efficacy of the model for prediction of FPA activity under different conditions of the medium.

Edible films and coatings are developed to improve quality and to extend shelf-life of food products. In this study, soy protein isolate was obtained from defatted soy flour by alkaline extraction and acid precipitation. Then edible films were prepared from soy protein isolate. The effects of protein concentrations and two plasticizers of glycerol and sorbitol on some physical and mechanical properties of the films were evaluated, using response surface methodology (RSM). The results showed that tensile strength, opacity, thickness and water vapor transmission rate (WVTR) were increased, while elongation of the films decreased by protein concentration. Increasing the concentration of glycerol and sorbitol increased WVTR, elongation, total color difference (DE), thickness and opacity, while declined tensile strength of the films. The model developed by RSM for the physical and mechanical properties of the films had high coefficient of multiple determination (R2>0.87) and significant F values. The models suggested that the concentration of soy protein and the type and concentrations of the plasticizers are the most influential factors with significant effects on the properties of soy protein isolate films.

Rice bran is a waste of milling factories of our country despite having nutritious ingredients normally used as animal feed and poultry. In this research, Initially, Three varieties of rice, including Tarom, Anbarbo and Hashemi were selected and heavy metals of them were analyzed and then In order to select the appropriate method of bran extract, Aoutoclave at a temperature of 100 and 120oC for the extraction of rice bran were used, and in order to provide treatment of drink, The rice bran extract in amounts of 5%, 10%, 15% and 20% were used in the formulation of orange drink. After packing and pasteurization, the samples were kept in the refrigerator for three months and physical and chemical characteristic were evaluated. Rheological properties of samples and rice bran extracts using Brookfield (at 5oC) were studied and results showed that by using of Aoutoclave extraction method, increasing temperature increased the amount of extraction of compounds found in rice bran. Investigation of rheological properties of the extracts suggests that extracts showed the behavior of a Newtonian fluid. The results also show that increasing the amount of rice bran extract in the formulation of drink, consistency coefficient decreased and the flow index increased. Investigation of consistency coefficient of treatments during storage indicates that consistency coefficients were slightly lower in the second and increased again in the third month.

Grape molasses is one of the famous by products of grape that more produced by traditional methods. In this research, some physicochemical properties of grape molasses such as SG, pH, total sugar, ash and rheological properties by using of a single cylinder rotary viscometer at three temperatures (25, 45 and 65oC) and three concentrations of 35, 50 and 76 were measured. Mathematical calculations in basis of Mitchka method shown that it is non-Newtonian and have dilatant behavior. Arrhenius model used for temperature dependence of consistency coefficient and activation energy calculated in range of 15.197 to 34.070 kJ/mol. Finally, by using of exponential relationship concentration dependence of consistency coefficient was evaluated.