保加利亚乳杆菌的发酵特性及其在牦牛酸乳中的应用

Fermentation Characteristics of Lactobacillus bulgaricus and Application in Yak Fermented Milk

为了筛选应用于牦牛酸乳发酵的乳杆菌,研究了8株野生乳杆菌在脱脂乳体系中的生长和产酸特性,结合气相色谱-质谱联用技术(GC-MS)分析单株发酵脱脂乳酸乳的挥发性风味组成,从中选取了4株既可快速产酸又能产生特色风味酸乳的乳杆菌,并结合感官分析评价单株发酵牦牛酸乳的挥发性风味特性。结果显示,风味喜好度高的牦牛酸乳含有较高的酯类、醛类物质,其中酯类质量比在9.82μg/kg左右,醛类物质质量比在174.64μg/kg左右;酸类、醚类、醇类物质含量在一定范围内处于较低水平,其中酸类物质质量比在366.51~495.84μg/kg,醚类物质质量比在5.05μg/kg及以下,醇类物质质量比在1.42μg/kg及以下。全脂牦牛乳凝乳时间长,在发酵过程中脂肪易被酯解生成膻味物质即中短链脂肪酸、部分酮类等;因此,产生较高含量的果香类物质如酯类、醛类和较低含量的膻味物质的发酵菌株将有助于提升牦牛酸乳的品质,在牦牛酸乳制品的生产中具有潜在应用价值。

In order to screen Lactobacillus to ferment yak milk rapidly with characteristic flavor,the growth of 8 strains of wild Lactobacillus and acid production were studied. The volatile flavor composition of single-strain fermented skim milk was analyzed by gas chromatography-mass spectrometry（ GC-MS）.The 4 wild Lactobacillus strains could not only ferment skim milk rapidly but also provide characteristic volatile flavor to fermented yak milk,combined with the sensory analysis to evaluate the volatile flavor characteristics of the yak yogurt. The results showed that yak yogurt with high flavor preference contained higher esters and aldehydes,with esters content of 9. 82 μg/kg and aldehydes content of 174. 64 μg/kg.Acids,sulfur compounds and alcohols were lower in these samples than the others,and the contents of acids were between 366. 51 and 495. 84 μg/kg. Meanwhile,the content of sulfur compounds was below5. 05 μg/kg and the contents of alcohols were less than 1. 42 μg/kg. The gelation of whole yak milk took a long time in the fermentation process and the hydrolysis by lipase generated the off-flavor components,most of which are short-chain fatty acids and some ketones,etc. The strains which can result in higher levels of fruity substances such as esters,aldehydes will help to improve the quality of yak yogurt and have potential application for the development of yak dairy products.