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.

本研究旨在探究嗜热链球菌（Streptococcus thermophilus）CICC 6038与德氏乳杆菌保加利亚亚种（Lactobacillus delbrueckii subsp. bulgaricus）CICC 6047之间的共生关系。此外，本研究考察了二者不同接种比例对发酵的影响，并针对最优接种比例下的单菌发酵与混合菌发酵乳，开展了发酵特性及贮藏稳定性对照实验。研究发现，六种接种比例（1:1、2:1、10:1、19:1、50:1、100:1）下，发酵乳达到pH 4.6所需时长（tpH4.6）以及贮藏期间的pH变化量（ΔpH）均存在差异。通过统计模型评估最优接种比例，最终选定19:1这一比例，该比例展现出较高的酸化速率与较低的后酸化程度，贮藏50天后pH值维持在4.2至4.4之间。