Release of Proteolysis Products with ACE-Inhibitory and Antioxidant Activities in Probiotic Yogurt Containing Different Levels of Fat and Prebiotics

In this study, the effects of prebiotic ingredients (inulin and wheat fiber) and fat percentage (0, 2 and 3.5%) on physicochemical properties, degree of proteolysis, antioxidant and ACE-inhibitory activity within 21 days storage of yogurt containing probiotic Lactobacillus casei at 5 ± 1 °C were evaluated. The results of statistical analysis showed that the application of prebiotics led to a significant increase in water-holding capacity, proteolysis and ACE-inhibitory activity of samples. The degree of proteolysis in yogurt increased as storage time elapsed (P < 0.05) but when proteolysis exceeded a certain threshold, this trend began to decline. Also, during storage time, water holding capacity reduced initially but increased thereafter. Moreover, based on our findings, the survival of L. casei, in samples treated with inulin and wheat fiber, increased significantly as compared to the control sample (P < 0.05) whereas the fat percentage did not reflect significant (P < 0.05) effect on the survival of probiotic bacteria. Furthermore, prebiotic ingredients and the presence of probiotic cultures had significant (P < 0.05) effect on the antioxidant activity of samples.