酸奶中几种益生菌菌群数量的分析研究
酸奶是一种对人体的健康发挥着重要作用的乳制品，而其中的益生菌正是酸奶发挥这种作用的关键所在。对其中益生菌菌群数量的分析研究，可以帮助我们了解到酸奶中益生菌的生长特点，杂菌的污染状况，从而判断出酸奶在室温下的存放期限。本实验通过平板菌落计数法和比浊法来绘制酸奶中保加利亚乳杆菌、双歧杆菌和嗜热链球菌的生长曲线，通过血球计数板计数法来测定酸奶中益生菌的总菌数，来判断酸奶中杂菌污染的情况。结果测得三种益生菌基本在20个小时之后就开始衰亡，而益生菌的总菌数却在不断增长，说明酸奶在室温下有大量杂菌生长。保加利亚乳杆菌，双歧杆菌和嗜热链球菌都属于革兰氏阳性菌，这三种菌均能利用葡萄糖、乳糖、淀粉和硝酸盐，在发酵过程中都不产气。嗜热链球菌不能利用甘露醇，双歧杆菌不能利用柠檬酸盐。
关键词：酸奶，保加利亚乳杆菌，双歧杆菌，生长曲线，嗜热链球菌
Study on the number of probiotics in yoghurt
Abstract: Yoghurt is a kind of dairy product, which probiotics playing a significant role in the health of human body. The analysis of the number of probiotic bacteria in yoghurt can help us to comprehend the growth characteristics of probiotics and the contamination of miscellaneous bacteria in yoghurt, so as to determine the storage time of yogurt at room temperature. This experiment is to determine the growth curves of Lactobacillus bulgaricus, Bifidobacterium and Streptococcus thermophilus in yoghurt by plate colony counting and turbidimetry, determining the contamination of the bacteria in yogurt. The results show that the three probiotics began to die after 20 hours, but the total number of probiotics was increasing, indicating that yoghurt had a large number of miscellaneous bacteria growing at room temperature. Lactobacillus bulgaricus, Bifidobacterium and Streptococcus thermophilus all belong to Gram-positive bacteria, which can use glucose, lactose, starch and nitrate, and they do not produce gas during the fermentation process. Streptococcus thermophilus cannot use mannitol, and Bifidobacteria cannot use citrate.
Key words: yogurt Lactobacillus bulgaricus Bifidobacterium growth curves
Streptococcus thermophilus
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