| Ester substances are important flavor substances in fermented products such as Baijiu and vinegar.In order to increase the content of esters and thus the quality of Baijiu and vinegar,it is of great significance to screen strains with high production of esterase from the natural environment and study their biological characteristics.In this paper,high-yield esterase strains were isolated and screened from red heart daqu and fresh Baijiu tartare used in Shanxi Fragrant Baijiu Production based on flavor and enzyme-producing properties,and their biological characteristics and application effects in Shanxi Baijiu and vinegar were studied.The improvement of quality and efficiency provides the basis for high-quality bacteria resources.The findings are as follows:(1)Three strains were isolated from Shanxi Red Heart Daqu and Fresh Bream,named Hm,Ym,and Bm.By measuring the enzyme-producing performance and ester-producing ability of the three strains,and analyzing its volatile components by HS-SPME-GC-MS,a high-yielding esterase strain Hm was obtained by comparison.It reached(14.75±0.08)U/g,the relative content of ?-phenylethanol with rose flavor in volatile components reached 47.32%,and the total ester content reached(4.98g±0.03)g/L.According to morphological and molecular biological identification,the strain was Monascus ruber and was named Monascus ruber Hm.The optimum growth temperature of the strain was 30?,the optimum p H was 4-6,the sugar content tolerance was 70%,and the ethanol tolerance was 9%.Its ability to catalyze hexanoic acid and ethanol is(14.75±0.04)U/g,its ability to catalyze acetic acid and ethanol is(10.32±0.06)U/g,and its ability to catalyze lactic acid and ethanol is(5.76±0.09)U/g;Compared with ordinary Daqu and esterified red yeast rice,the esterification of three kinds of acids and alcohols was stronger.(2)The single-factor test,Plackett-Burman test,and Box-Benhnken test were used to optimize the fermentation process of high-yield esterase from Monascus Hm.The optimum process conditions were determined as fermentation time 7d,fermentation temperature 30?,inoculation amount 10%,initial p H 6,60% moisture content,esterification power can reach(14.75±0.08)U/g.(3)By comparing the four different fermentation methods of Daqu fermentation,single strain pure breed fermentation,strain and Daqu compound enhanced fermentation,and Saccharomyces cerevisiae fermentation,it was found that the Baijiu produced by strain Hm fermentation had the best quality and the total ester content was(1.27±0.00)g/L,compared with the blank control,the total ester content of Daqu fermentation was significantly increased by 21%(P<0.05);and the types and contents of volatile components in 8 samples were detected by the HS-SPME-GC-MS method.The composition and content of the Baijiu sample fermented by the strain Hm have increased,especially the esters,which makes the aroma of the Baijiu sample more mellow and harmonious,and has a clear rose grape aroma.This shows that the single strain Hm can replace Daqu as a fermentation agent in the traditional Baijiu brewing,improve the quality of Baijiu.(4)The physical and chemical indexes of vinegar samples obtained by adding different kojis in the fermentation stage of alcohol and acetic acid in vinegar were measured.It was concluded that when the strain Hm and Daqu were added in the alcoholic fermentation stage for intensive fermentation,the food was obtained by fermentation.The total acid of vinegar reached(4.04±0.01)g/100 m L,and the total ester content reached(1.31±0.004)g/L.Compared with the vinegar produced by fermentation of Daqu,the total acid was significantly increased by 19%(P<0.05),the total ester content was significantly increased by26%(P<0.05),and the vinegar had a clear rose grape aroma and a long aftertaste.This shows that in the saccharification and alcohol fermentation stages of brewed vinegar,the addition of strain Hm and Daqu to enhance fermentation can improve the quality of vinegar. |
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