Optimizations of Probiotic Yogurt Formulation Containing Eggplant Puree Based on Analytic Hierarchy Process

The aim of this study was to evaluate the effect of incorporation of eggplant puree (0-45%) on physicochemical properties (pH, acidity, color and syneresis), sensorial parameters (odor and taste, color, and texture) and survival of probiotics in yogurt after 1, 4, 7, 10 and 14 days of storage. Furthermore, Analytic Hierarchy Process (AHP) was used to determine the best probiotic eggplant yogurt according to the assessed parameters. The results showed that by increasing the amount of eggplant puree, the extent of acidity, syneresis and lightness (L*) decreased while the pH increased. Incorporating eggplant puree caused significant (P<0.05) reduction of probiotic bacteria at the beginning of storage time. However, during the storage period this status contrarily changed, in such  a way that yogurt samples containing a higher concentration of eggplant puree at the end of storage had a higher count. This was probably due to prebiotic effect of eggplant puree and the lower pH of yogurt sample. According to data analysis by AHP, yogurt sample contained 30% of eggplant puree with the weight of 0.171 being the best formula compared with the others. The results showed that incompatibility rate was 0.08 and as this value was lower than 0.1, the obtained results had an acceptable reliability and credibility. Based on the results of this research, the manufactured eggplant probiotic yogurt having an acceptable sensory and probiotic properties may be introduced as a functional food product. Furthermore, due to prebiotic capability of the eggplant puree, it could be used in various probiotic products.