Biochemical, microbiological, and sensory properties of probiotic yogurt made from Iranian native strains compared to commercial strains

This study was performed to evaluate the effects of using native and commercial probiotic strains on biochemical, microbiological, and sensory properties of yogurt. The viability of probiotic bacteria in all samples exceeded 6 log CFU/ml required to provide health benefits. The native Iranian Lactobacillus casei showed the highest viability throughout storage (8.5 log CFU/ml at the end of storage). Three distinct phases were observed in pH, acidity, and redox potential during the fermentation of all samples. Commercial L. casei strain had the lowest mean acidity increase rates and the longest incubation times. The growth of Lactobacillus delbrueckii ssp. Bulgaricus and Streptococcus thermophilus in probiotic yogurt was improved compared to the control yogurt. The control sample had the lowest score in all sensory parameters evaluated. Overall, yogurt containing native Iranian L. casei strain is recommended because of its good sensory and microbial properties. Practical applications Among different functional food products, probiotic dairy products are of great interest and yogurt is the most popular probiotic carrier. In most cases, commercial strains of Lactobacillus and bifidobacteria are incorporated into yogurt and native strains have not been studied widely. In this regard, isolation, characterization, and investigation of the effect of their application in dairy products can be promising in the development of functional dairy products with acceptable qualitative characteristics.