摘要：本文从传统发酵制品中获得乳酸菌，以丁二酮为指标筛选出丁二酮产量较高的乳酸菌，作为发酵剂用于切达干酪的制作，经过初筛、复筛，选出产丁二酮含量最高，为41.43mg/L的一株乳酸菌，经16SrDNA鉴定为干酪乳杆菌。将其作为发酵剂与商业菌种复配用于切达干酪的制作，并于其他三株实验室中的菌株做对比，综合筛选出最适宜作为发酵剂的菌种。经过切达干酪的制作及后熟过程，利用GC-MS及感官评价进行测定，结果显示筛选出的菌种2-30制作的切达干酪在后熟后感官评价较优，后熟后的切达干酪测得的风味物质种类及含量最高，为最适宜作为干酪发酵乳酸菌的菌种。

关键词：丁二酮；筛菌；鉴定；切达干酪；风味

Screening of high-yielding two ketone Lactobacillus and its effect on flavor formation of Cheddar cheese

Abstract:

In this paper, a lactic acid bacteria with high yield of two ketones was selected from the traditional fermented products with two ketones, which was used as a fermentor to make cheddar cheese. After screening and screening, a strain of Lactobacillus with the highest content of two ketones about 41.43mg/L was selected and identified by 16SrDNA as Lactobacillus casei. It was used as a fermentative and commercial strain to make cheddar cheese, and compared with the other three strains in the laboratory, so as to evaluate its effect on the flavor formation of Cheddar cheese.After the process of Cheddar cheese making and after ripening, GC-MS and sensory evaluation were used to test it. The results showed that the sensory evaluation of Cheddar cheese made by the screened strains was better after the back ripening, and the type and content of the flavor substances measured by cheddar cheese after ripening were the highest, which was the most suitable for the strain of cheese fermented Lactobacillus.

Keyword：

Butyl two ketone; sieve bacteria; identification; cheddar cheese; flavor

目录

1 引言 4

1.1干酪起源及定义 4

1.2干酪分类 4

1.3干酪的良好风味物质 4

1.4切达干酪风味的影响因素 5

1.4.1奶的成分 5

1.4.2切达干酪的加工工艺 5

1.4.3发酵剂乳酸菌 5

1.5干酪中的特征性风味物质 6

1.6 丁二酮的检测方法 7

1.7干酪风味物质的分析方法 7

1.7.1GC-MS 7

1.7.2感官评价法 8

1.8研究目的及意义 8

1.9 本课题研究的主要内容 8

2 实验材料和方法 9

2.1 实验材料 9

2.1.1实验材料、试剂及样品信息 9

2.1.2 主要仪器及设备 9

2.2 实验方法 10

2.2.1高产丁二酮菌株的筛选 10

2.2.3  酶标法测定丁二酮含量 11

2.2.4 菌种的鉴定 11

2.2.5 切达干酪的制作 12

2.2.6 GC-MS测定 13

2.2.7 感官评定 13

3 结果与讨论 14

3.1丁二酮标准曲线的绘制 14

3.2菌株筛选的结果 14

3.3菌种鉴定的结果 15

3.3.1菌落的微生物形态观察 15

3.3.2 PCR电泳 16

3.3.3测序结果及进化树 17

3.4切达干酪中挥发性风味物质含量的测定 17

3.5 切达干酪的感官评定 22

4.结论 27

致   谢 28

参考文献 29

1 引言

1.1干酪起源及定义

干酪是一种营养价值很高的发酵乳制品，它含有丰富的蛋白质、脂肪及全部的必需氨基酸、维生素和矿物质等。蛋白质、钙、核黄素是干酪组成成分中最重要的营养成分。干酪中含有钙、磷、镁等重要的矿物质。干酪中脂溶性维生素的含量取决于干酪的脂肪含量，原料奶中80%～85%的会进入干酪。食用100g干酪可以补充每天所必需的100%的VB2、27%的VB12和15%的叶酸。干酪含有如此多的营养成分，易消化吸收，不易致肥，因此被营养学家封为理想的食品，誉之为“奶黄金”，乳业皇冠上的“珍珠”。