تأثیر افزودن آنزیم پروتئاز تجاری بر پروتئولیز پنیر سفید فراپالایش ایرانی

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.