不同品牌的发酵型酸奶中乳酸菌含量调查分析
摘 要：乳酸菌含量是评价产品对于人体营养与保健作用的重要指标，选取三种品牌酸奶对其乳酸菌含量和酸奶中蛋白质、pH值、酸度值在37℃条件下一周变化情况进行调查分析从而了解不同品牌酸奶的差异。新的酸奶国家标准（GB19302-2010）中规定产品中的乳酸菌数不得低于1×106 cfu/mL，酸度值不得低于70 °T，蛋白质含量不得低于2.9 g/100 g。经检测，三种品牌酸奶的乳酸菌含量均达到国家标准，符合国家要求的乳酸菌个数指标，但三种品牌酸奶乳酸菌含量具有一定差异。短期内在37℃条件下不同品牌酸奶的pH值、酸度、蛋白质含量虽然随着时间也发生不同程度的变化，但是仍然符合国家规定的质量标准。
关键词：酸奶；乳酸菌；酸奶指标
Investigation and Analysis on the Content of Lactic Acid Bacteria of Different Brands of Yogurt
Abstract：The content of lactobacillus is a crucial indicator to evaluate human nutrition and health function of a product; thereby three kinds of brand yoghourt are selected, and by observing the variations of their lactobacillus content, protein, pH value, and acidity value at a temperature of 37 degrees Celsius in a week, an investigation and analysis are to be carried out so as to get to know the difference of various brand yoghourt. The new national standard (GB19302-2010) regulates that the number of lactobacillus should not be less than 1*106 cfu/mL, acidity value should not below 70°T, and the protein content should not be less than 2.9 g/100 g. According to the inspection, the lactobacillus content of the three brand yoghourt are all up to the national standard, which are all in accordance with the indicator of lactobacillus number; whereas there exists discrepancy of the lactobacillus content among the three brand yoghourt. At the temperature of 37 degrees Celsius, although the pH value, acidity value and protein content of the three brand yoghourt vary to different extents over time, they still conform with the national quality standard.
Key words：Yoghurt；Lactic Acid Bacteria；Yoghurt Indicators
目 录
摘 要 1
Abstract 1
引言 1
1.材料与方法 2
1.1实验器材 2
1.1.1材料 2
1.1.2药品 2
1.1.3仪器 2
1.2菌落测定 3
1.2.1 LAB半固体培养基的配方 3
1.2.2操作流程 3
1.3酸奶指标的测定 4
1.3.1酸奶的保存 4
1.3.2测量方法 4
2.结果与分析 5
2.1菌落形态观察结果 5
2.2菌落计数结果 6
2.2.1 A品牌酸奶乳酸菌含量测定 6
2.2.2 B品牌酸奶乳酸菌含量测定 6
2.2.3 C品牌酸奶乳酸菌含量测定 6
2.2.4测定结果分析 6
2.3酸奶指标测定结果 7
2.3.1酸奶pH值变化 7
2.3.2酸奶酸度值变化 8
2.3.3酸奶蛋白质含量变化 8
3.结论 10
参考文献 10
致谢 12,3991
引言
酸奶是以鲜奶（或通过奶粉复原）经乳酸菌混合发酵并冷藏而成的一种活菌饮品[1]。其中的乳酸菌经过发酵作用后，鲜奶中的部分乳糖会转变为乳酸等有机酸，这对肠道内的有害物质会起到一定的抑制作用[2]。同时，这些乳酸菌也可促进人体中胃液的分泌以及对钙质的吸收。因此，长期饮用酸奶不仅可改善消化不良、便秘等情况，也可为人们提供丰富的营养[3,4]。因此，酸奶已经成为一种时尚饮品，深受广大消费者喜爱[5]。