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The effect of addition of a commercial enzyme derived from Bacillus Polymyxa type IX on Iranian UF-Feta cheese during a 60- day ripening period on chemical composition, pH and proteolysis of cheese samples was investigated. No Significant differences were observed in the chemical composition between experimental and control cheeses. ​​In experimental cheese, pH values were significantly (P< 0.05) higher throughout whole ripening period and at 60d  it was 4.6 and 4.77 in control and experimental cheeses, respectively. Soluble nitrogen in pH=4.6 was significantly (P< 0.05) higher in experimental cheese at 45 and 60d.  At 60d, this index was 6.38 and 7.73% in the control and experimental treatments, respectively. Significant difference in the level of trichloroacetic acid (TCA) 12% was also observed at 45 and 60d. Urea- polyacrylamide gel electrophoresis of the pH 4.6-insoluble fractions showed that αs₁-casein was hydrolysed faster than the β-casein. Intact αs₁-casein values from 100 % on the first day reached to 82.93 % and 71.24 % and in β- casein reached to 90.28 and 90.56% at 60d in control and experimental cheeses, respectively. The concentration of total free amino acids in whole ripening period was significantly (P< 0.05) higher in experimental cheese and at the end of the ripening period was 0.68 versus 0.54 in control cheese (mg Glycine/g cheese). Levels of individual free amino acids were also different between treatments.

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Goat's milk yogurt has a high nutritional value and digestibility and less allergenicity than cow's milk products. The problem with goat's milk yogurt is the specific taste that results from the high concentrations of volatile fatty acids that cause goat's taste and limit consumers acceptance of this product. In this research, the effects of adding 20% pineapple and peach nectar on physicochemical (dry matter, fat, protein, acidity, synersis, water holding capacity and viscosity) and sensory properties of goat's milk yogurt during 28 days of refrigerated storage were evaluated. The results showed that adding nectar significantly reduced the amount of dry matter (p <0.05). In nectar-containing samples, dry matter content had increasing trend during storage. Fat and protein levels were significantly lower than control samples (p <0.05). The pH of nectar containing yogurts during storage was significantly lower and its acidity was significantly higher than that of control yogurt (p <0.05). The trend of synersis changes in nectar-containing yogurt samples was rising in the first week and then decreased until the end of the storage period and the process of changes in water storage capacity was initially decreasing and then increasing. The viscosity increased during the first week and then decreased significantly until the end of the storage period (p <0.05). The viscosity of nectar-containing yogurt samples was significantly lower than that of control sample (p <0.05). Sensory evaluation results showed that the highest overall acceptance score was given to the sample containing pineapple nectar (4.66, 4.46) and the lowest overall acceptance score to the sample containing peach nectar (3.36, 3.33) due to its dark color and sour taste on the 1st and 14th days respectively . Based on the experiments, the use of pineapple nectar is a good method in order to cover goat taste in goat's milk yogurt with preserved its qualitative characteristics.

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In this research, attenuated culture of thermophilic lactobacillus helveticus - B02 was used as an adjunct culture in the production of UF white cheese and proteolysis and lipolysis were evaluated as indicators of ripening during a 60-day period. The chemical composition and pH were not affected by the addition of attenuated culture. Water-soluble nitrogen and Non-protein nitrogen in experimental cheese were significantly higher. Urea-PAGE of insoluble fractions of cheese samples showed that the hydrolysis of αs1-casein in experimental cheese increased from the 45th day of ripening and was significantly higher. The amount of free fatty acids increased over time in both treatments. Palmitic acid (C16: 0) and oleic acid (C18: 1) had the highest concentrations of free fatty acids in both treatments. In cheese containing attenuated starter on the 60th day, the levels of free fatty acids of C4: 0, C6:0, C18:0 and C18:1 were significantly higher, compared to the control treatment (P <0.05). The levels of other fatty acids in the two treatments did not show a significant difference. Addition of attenuated adjunct culture had a positive effect on the development of proteolysis and to some extent lipolysis in UF white cheese.