Screening Of High-Yield Esterase Strain And Its Application In Fruit Cheese

Cheese is gradually accepted by Chinese consumers as a highly nutritious food.The main reason that restricts the popularization of cheese in China is that the flavor of cheese is traditional and single.Therefore,it is imminent to improve the traditional cheese flavor.Fruit flavors are accepted by most Chinese,while ethyl butyrate is a characteristic material of fruit flavor.Streptococcus thermophilus can metabolize tributyrin to form ethyl butyrate.This article from Streptococcus thermophilus,Lactobacillus casei,Lactobacillus paracasei and Lactobacillus rhamnosus selected strains of high yield of ethyl butyrate,and the strain as an auxiliary fermentation agent used in cheese,verified in Fruit flavors in cheese.The research provided the theoretical basis for the development of fruit flavor cheese.The main research is as follows:1.High-yield esterase strain screening.Sixty-six strains of lactic acid bacteria were screened by gas chromatography(GC),and 32 strains of ethyl butyrate obtained from the preliminary screening were screened for esterase activity.The activity of ethyl butyrate esterase Eight strains with high esterase activity were obtained from the strains above 1.83 μmol aNA/mg protein·mine.The eight strains were evaluated for acid production,autolysis and ethyl butyrate production in liquid environment.Finally,X8 This strain of bacteria 6h titration acidity of 0.003±0.000 moL/L,the autolysis rate of 38.10±0.07%,the amount of ethyl butyrate in the liquid environment at 193.06±5.76 nmoL/100g paste,so X8 relative to the other The strains produce low acid,high self-solubility,liquid ethyl butyrate production ability,and more able to adapt to the cheese environment.2.Strains produce cheese flavor verification.SPME-GC-MS combined with sensory evaluation of X8 strain as an auxiliary fermentation agent on the cheddar cheese flavor.In the experimental group,1011 cfu/L of X8 and 3.3 mmoL/L of tributyrin were added into the milk simultaneously,the highest yield of ethyl butyrate was 0.15±0.01 μg/kg after 30 days of maturity.Sensory evaluation The results confirmed that the group produced the most significant fruit flavors.3.This experiment screened a strain of Streptococcus thermophilus strain X8,which produced high yields of butyrate ethyl ester and was consistent with the basic properties of the auxiliary starter,which had the highest esterase activity and the highest ability to produce ethyl butyrate in a liquid environment.The esterase of this strain can promote the formation of ethyl butyrate of tributyrin and ethanol in the cheese during cheese ripening.That is,the strain X8 can significantly enhance the fruit flavor of cheese during cheese ripening.