Influences of lactic acid bacteria producing lipase on fatty acids of mutton fermented sausage

Lipase can determine the accumulation and production of flavor substances in most meat processing. The lipase-producing strains were often added in fermented meat products, in order to improve the flavor of products. In this study, the lactic acid bacteria was screened to investigate the influence of this strain on fatty acids of fermented sausage, due to its high lipase-producing ability. The lipase-producing activity of lactic acid bacteria usually depends on the size of the transparent circle that produced from the decomposition of tributyrin during the metabolism. Meanwhile, it is necessary to combine the variation in expression level of lipase genes Lip0069 and Lip0893. The lactic acid bacteria with high lipase production ability were selected and fermented to produce fermented sausage. The natural fermentation ZR group and the addition of lipolytic enzyme M group were used as control. Samples were taken on 0, 2, 4, 6, 12 and 24 days to analyze the effects of lactic acid bacteria at different fermentation stages on fatty acid composition in fermented sausages. The results showed that among the 10 strains, 6 strains produced lipase during metabolism of which Lactobacillus helveticus, TR1-1-3 had the strongest activity of producing enzyme (P<0.05), and fluorescence quantitative PCR detection showed that the expression levels of lipase genes Lip0069 and Lip0893 in strain TR1-1-3 were the highest. The effect of Lactobacillus on fatty acid composition of fermented sausage showed that during the sausage was fermented, dried, matured and refrigerated at 4 ℃ There were 34 fatty acids that detected in the experimental group of fermented sausage, including 16 kinds of Saturated Fatty Acids (SFA), 9 kinds of Monounsaturated Fatty Acids (MUFA), and 9 kinds of Polyunsaturated Fatty Acids (PUFA). The high content of SFA was mainly composed of myristic acid (C14:0), palmitic acid (C16:0) and stearic acid (C18:0), during the low-temperature cold storage at 4℃, the SFA content in the natural fermentation ZR group and the added starter TR1-1-3 group decreased in the proportion of fatty acids, while the M group added with enzyme preparations increased, and the SFA ratio in other groups did not change significantly (P>0.05). The high contents of MUFA were mainly oleic acid (C18:1C9), palmitoleic acid (C16:1), heptadecenoic acid (C17:1), and tetradecenoic acid (C14:1). The PUFA with high content included linoleic acid (C18:2C9), linolenic acid (C18:3N6, C18:3N3), arachidonic acid (C20:4), and docosahexaenoic acid (C22:6, docosahexaenoic acid, DHA). After two days of fermentation in experimental group TR1-1-3 and ZF22, the content of MUFA increased significantly (P<0.05), compared with that of nontreatment. The content of MUFA in the five experimental groups reached the peak on the 12th day, and the increasing proportion of TR1-1-3 was the highest, indicating that there was a significantly different from the experimental group ZR, M (P<0.05). The PUFA content of experimental group TR1-1-3 changed significantly after two days of fermentation (P<0.05). After 12 days, the PUFA content of experimental group TR1-1-3 remarkably increased by 54.17%, and there was a significant difference compared with other experimental groups (P<0.05). The content of SFA, MUFA and PUFA in all experimental groups showed an upward trend from 0 to 12 days, and the trend of 12 to 24 d changed slowly. The results demonstrated that Lactic acid bacteria TR1-1-3 can reduce the proportion of SFA in fatty acids in meat products, while can significantly accelerate the increase rate, and content of MUFA and PUFA. This finding can provide a promising prospect to improve the fat characteristics of sausage and other fermented meat products.