Adding Casein Hydrolytic Peptides to Improve the Processing Characteristics of Yogurt

Yogurt was prepared from raw milk added with peptides from bromelain hydrolyzed casein at different concentrations (0.1%, 0.3% and 0.5%), and the changes in physicochemical, microbial and flavor characteristics of yogurt during fermentation and cold storage were determined. The results showed that adding casein hydrolytic peptides (CHP) accelerated the pH decline during the late fermentation period, and reduced the fermentation time of yogurt. When 0.1% CHP was added, the fermentation time was reduced by 34 minutes compared to the control group. Microrheological measurement showed that adding CHP decreased the elasticity index (EI) and fluidity index (FI), but increased the macroscopic viscosity index (MVI) of yogurt during the late fermentation period. Scanning electron microscopy showed that the yogurt samples in each group had a porous network structure. Proper addition of CHP (0.1%) improved the colloid structure and made the network structure of yogurt more compact and uniform. During the cold storage of yogurt, adding CHP increased the count of viable starter bacteria, and promoted the formation of flavor compounds such as acids, aldehydes and ketones, and adding 0.3% CHP reduced the EI value of yogurt. With increasing addition of CHP from 0.3% to 0.5%, the hardness and adhesiveness of yogurt decreased gradually, but water-holding capacity, cohesiveness and viscosity did not significantly change. The results of this study provide technical references for the application of CHP in yogurt processing and the improvement of product quality and functionality.