Team:NEU China B/background
Background
In life, people often view yogurt as a kind of flavor drink. It is better in taste and more nutritious than milk, and can better regulate the intestinal flora of the human body. After fermentation, the fatty acids in yogurt increased twice as much as the raw materials. These changes make yogurt easier to digest and absorb, and the availability of various nutrients increases.
In the process of fermentation, lactate（lactic acid） is one of the most important materials. As a condiment in yogurt processing, it can improve the taste, inhibit the growth of harmful bacteria and enhance the effect of antioxidant [1].
The lactate fermentation in yogurt belongs to the lactate fermentation mechanism, and the lactate fermentation mechanism starts from E. coli. This system is used by many bacteria. Lactobacillus bulgaricus and Streptococcus thermophilus, which are commonly used in yogurt production, also use this system.
The key technology of yogurt processing is the selection of lactobacillus and the control of fermentation temperature and PH value. Lactate can improve the quality of yogurt by controlling its PH value [2]. When it is 23 ~ 45 ℃, lactobacillus grow best. It can produce a large amount of lactate during the fermentation. It can make the milk acidity up to 3000 T; When it comes to 22 ~ 30 ℃, streptococcus grow best [3]. It can make the milk acidity up to 1000 T.
Therefore, it is critical to detect the concentration of lactate in the process of yogurt production.
Reference
1. Shengli Yin, Jian Du, Chen Xu, Research status and application of lactic acid bacteria[J]. Food Technology, 2012, 37(9):25—29.
2. JOHN R P , ANISHA G S, NAMBOOTHIRI K M,et al. Direct lactic acid fermentation; Focus on simultaneous saccharification and lactic acid production[J]. Biotechnology Advance, 2009, 27(2)： 145-152.
3. Junlin Wu, Jianling Bai, Shuping Mo. Study on fermentation technology of lactic acid bacteria R8 high density process[J]. Modern food Technology, 2018, 34(2):164—170.