Optimization of survivability of Lactobacillus casei LAFTI-L26 and the physicochemical properties of functional flavored set yogurt containing grape syrup

In this study, the effect of a grape syrup and storage time on the physicochemical, microbial, and sensory properties of yogurt were evaluated using the response surface method. The amount of grape syrup and storage time were in the range of 0-5% and 1-21 days, respectively. The results of the statical analysis showed that with increasing the amount of grape syrup and storage time, the number of Lactobacillus casei were increased and decreased, respectively (p<0.05). With increasing grape syrup, the moisture content and acidity decreased and ash, pH, and syneresis increased (p<0.05). During storage time, pH decreased and acidity and syneresis increased (p<0.05). The results of the microbial test showed that with increasing grape syrup and storage time, the molds count was decreased (p<0.05). The results of sensory evaluation also showed that by increasing the amount of grape syrup, the score of color, flavor, and texture increased (p< 0.05). According to the obtained results, for producing bio-yogurt, grape syrup at 5% and the storage time about 7 days found to be the optimal processing conditions.