Fermentation characteristics and post-acidification of yogurt by Streptococcus thermophilus CICC 6038 and Lactobacillus delbrueckii subsp. bulgaricus CICC 6047 at optimal inoculum ratio
This study aimed to investigate the symbiosis between Streptococcus thermophilus CICC 6038 and Lactobacillus delbrueckii subsp. bulgaricus CICC 6047. In addition, the effect of their different inoculum ratios was determined, and comparison experiments of fermentation characteristics and storage stability of milk fermented by their mono-cultures and co-cultures at optimal inoculum ratio were performed. We found the time to obtain pH 4.6 (tpH4.6) and ∆pH during storage varied among six inoculum ratios (1:1, 2:1, 10:1, 19:1, 50:1, 100:1). By the statistical model to evaluate the optimal ratio, the ratio of 19:1 was selected which exhibited high acidification rate and low post-acidification with pH values remaining 4.2 – 4.4 after a 50-day storage.