摘 要：本实验以市场上所售伊利风酸乳（原）为研究对象，通过平板计数法分别测定酸奶样品在4℃、37℃和常温（25℃）下保存期内乳酸菌数量，同时模拟酸奶购买过程，即将4℃下保存的酸奶放置常温下5个小时，测定这一过程中乳酸菌的数量动态变化。将实验结果对比国家标准（GB19302-2010）规定的酸奶质量标准检查酸奶样品是否合格。实验结果表明，酸奶样品在 4℃保存时，整个保质期内乳酸菌的数量符合国家食品安全标准；酸奶样品在37℃条件下保存时，第优尔天乳酸菌的数量就已经达不到国家食品安全标准的规定数量；酸奶在常温条件下可以保存八天不变质，此外，模拟酸奶的购买过程显示：酸奶的购买过程不会对酸奶的品质有大的影响。
关键词：酸奶；乳酸菌数量；平板计数法3847
Dynamic Study on Lactic Acid Bacteria Number of Yogurt on the Market in Shelf Life
Abstract: In this experiment, we used yili yoghurt (natural) as the esearch object, respectively counted the number of three samples of lactic acid bacteria (one sample was at temperature 4℃,one was 37℃ and one was 25℃,which was room .)by the plate count method.One yogurt sample stored under 4℃ was placed under the normal temperature for 5 hours, the number dynamic change of lactic acid bacteria in the process was reckoned. (GB19302-2010) by comparing the national standard of check qualified yogurt yogurt quality standards. results show that 4℃ is the most suitable temperature to store yogurt, during the warranty period, the number of lactic acid bacteria in line with the national food safety standards; the time is the shortest Under the condition of 37℃, the number of lactic acid bacteria have not meet the national food safety standards from the sixth day; Yogurt can be saved eight days under normal temperature without metamorphism, yogurt buying process will not have big effect on the quality of the yogurt.
Key words: Yogurt; Lactic acid bacteria number; Plate count method
目 录
摘 要 1
Abstract 1
引言 2
1. 材料与方法 2
1.1 试验样品 2
1.2 主要试剂与仪器 2
1.2.1 试剂 2
1.2.2 主要仪器 3
1.3 培养基 3
1.3.1 培养基主要成分 3
1.3.2 培养基的的配制及其灭菌 3
1.4 实验方法 3
2. 实验过程 3
2.1 准备 3
2.2 样品稀释 4
2.3 平板制作及菌落培养 4
2.4 菌落计数 4
2.5 实验重复 4
3. 结果 5
3.1 菌落观察结果 5
3.2 菌落计数结果 5
3.2.1 在4℃条件下储存的酸奶中乳酸菌数的动态变化 5
3.2.2 在常温条件下储存的酸奶中乳酸菌数的动态变化 6
3.2.3 在37℃条件下储存的酸奶中乳酸菌数的动态变化 7
3.2.4 储存酸奶购买过程中乳酸菌数量动态变化 8
3.2.5 不同温度下酸奶中乳酸菌数量变化对比 9
4. 分析与讨论 9
参考文献 10
致谢 12,3847
市售酸奶保存期内乳酸菌数的动态研究
引言
酸奶中含有大量的活性乳酸菌，可定居在人体鼻粘膜或消化道等处，乳酸菌代谢产生的乳酸能降低肠道内的pH值，抑制肠道中腐败菌的生长，减弱腐败菌的产毒作用，从而文持体内微循环环境。但乳酸菌活菌体的数量需达到一定程度才有可能使乳酸菌定植在人体的肠道内，文护人体健康[1]。对市售酸奶保存期内乳酸菌数的动态研究对于了解市场上所售酸奶质量是否合格，饮用对人体是否有益具有重要意义。 市售酸奶保存期内乳酸菌数的动态研究:http://www.youerw.com/shiping/lunwen_323.html