THE ROLE OF LACTIC-ACID BACTERIA IN YOGURT FERMENTATION

The fermentation of milk to yogurt is dependent on the production of lactic acid from fermentable sugars by the symbiosis of Streptococcus thermophilus and Lactobacillus bulgaricus. The proteolysis of milk proteins by lactobacilli contributes to the growth of S. thermophilus in addition to influencing the texture and taste of the final product. Other products of fermentation, such as polysaccharides, vitamins, volatiles and antimicrobial substances, contribute to the quality of the final product. The presence of bacterial cells or the metabolites which they produce may have a positive effect on different aspects of human health.