Effect of the milk fat content and starter culture selection on proteolysis and antioxidant activity of probiotic yogurt

Abstract

In this study, the effects of milk fat content -0%, 2% and 3.5%- and starter culture<br>-autochthonous or commercial- on physicochemical properties, degree of<br>proteolysis, antioxidant activity and viability of Lactobacillus acidophilus, within<br>21 days storage of probiotic yogurt at 5 1 C were investigated. Statistical<br>analysis showed that the type of starter culture had a significant effect -P &lt; 0.05-<br>on proteolysis and antioxidant activity, in such a way that both of them were<br>increased until the 14th day of storage but they decreased after this period.<br>Similarly, the pH value of all samples decreased during storage time. It ranged<br>from 3.84-4.34 and 4.18e4.43 for yogurt samples made by autochthonous and<br>commercial starter culture, respectively. According to the results, the survival of<br>Lactobacillus acidophilus decreased during storage time -P &lt; 0.05-, although it<br>stood at recommended levels for health effects -at least 106 cfu/ml in traditional<br>yogurt-. Milk fat content did not have significant effect on the survival of<br>probiotic organisms -P &lt; 0/05-.