Journal of Food Processing & Technology

Abstract

The Effect of Heat Inactivating Process on Biochemical, Microbiological and Sensory Characteristics of Iranian Drink Based on Fermented Milk (Doogh)

Elaheh Ahmadi, Amir Mohammad Mortazavian and Reza Mohammadi

This study investigates the effects of heat inactivating processing of yogurt bacteria compared with other sequential inoculation on biochemical, microbiological, and sensory characteristics of typical Iranian drink based on fermented milk (Doogh). The yogurt bacteria (Streptococcus thermophilus and Lactobacillus delbrueckiis sp. bulgaricus) were used in all treatments. Bifidobacterium animlis spp. lactis PTCC 1631 was used as probiotic bacteria. A pH, titrable acidity, redox potential, fermentation time, and viability of probiotic organisms were analyzed during fermentation and over the refrigeration storage for21 days at 5°C. Also, the sensory attributes of treatments were determined at the end of fermentation. The greatest (p<0.05) mean pH drop rate was observed in BlY-40-4.5 treatment (B. animlis spp. lactis PTCC 1631 was co-cultured with yogurt starter bacteria and incubated at 40°C until final pH 4.5).In addition, the greatest viability of bifidobacteria was observed in this treatment. The viability of bifidobacteria strains was significantly higher in heat inactivating treatments than non-heat treated treatments. This process didn’t have positive effect on sensory properties of Doogh. The most acceptability in taste, texture, and mouth feel and appearance tolerability were observed in co-culture treatment in this study.