Fermentation properties of Lactic acid bacteria from traditional dairy products and application in yogurt

In this study, four strains of L.bulgaricus and four strains of S.thermophilus, which were isolated from traditional dairy products, were investigated for the fermentation parameters and application in yogurt. Strains were fermented by skim milk culture medium.Fermentation properties such as fermentation time, main flavor substance, p H, titration acidity, viscosity and water holding capacity were determined. Strains with superior fermentation performance were further fermented with different ratios.Fermentation parameters and sensory parameters of the fermented milk were assayed.The results showed that Lb.YNF-5and St.GST-6 were selected as the strains with superior fermentation performance. The best ratio was Lb.YNF-5 ∶ St.GST-6 =1∶ 1, giving the best quality of yogurt with fermentation time of 5.8 h, viscosity of 7186.47 m Pa·s, the sensory evaluation score of76 points.In summary, Lb.YNF-5 and St.GST-6 could be good candidates potential of application as yoghurt starter cultures.