Effects Of Dominant Microorganism Strains On The Metabolites And Vinegar Flavor During Brewing Process In The Traditional Brewing Process Of Liangzhou Fumigated Vinegar

The microbial species in the brewing process of Liangzhou fumigated Vinegar are complex and diverse,and the dominant flora plays a crucial role in vinegar brewing.In this paper,five dominant microbial strains obtained from Liangzhou fumigated Vinegar were used as research objects,the growth characteristics of 5 single strains were researched.Based on the simulation test of vinegar solid-state fermentation by inoculating the different combination strains,the dynamic changes of the main metabolites during the fermentation process were analysised,the volatile substances of the fermented grains in the end of the fermentation were detected and their sensory quality was evaluated.The aim is to clarify the influence of the dominant strains on the metabolites and vinegar flavor during the fermentation process,and to provide a theoretical basis and a source of strains for the modern industrialization of traditional vinegar brewing.The main results obtained in this study are as follows:1.Three dominant strains were screened from Liangzhou fumigated vinegar,including high-yield alcoholic yeast,lactic acid bacteria and acetoin-producing Bacillus,which were identified by molecular biology as Clavispora lusitaniae,Lactobacillus paracasei and Bacillus zhangzhouensis.2.The growth characteristics of the five dominant strains were studied.The results showed that the five strains had a short delay time and could enter the logarithmic phase quickly and grew rapidly in the logarithmic phase.Among them,C.lusitaniae had better pH tolerance and alcohol tolerance;H.uvarum can not rapidly grow and metabolize acetoin under the conditions of high alcoholicity and low pH,however,it was suitable for production of acetoin at pH 6;Both L.paracasei and A.pasteurianuss have good acidogenic ability under low pH and high alcoholic conditions,the acid production at pH 4 was 9.28 g/L and 46.10 g/L,respectively,the acid production under the condition of 7% alcohol was 12.60 g/L and 63.60g/L,respectively.B.zhangzhouensis has a good pH tolerance and alcohol tolerance,and the yield of acetoin is 32.29 g/L at 5% alcohol.3.The dynamic changes of main metabolites in the simulated vinegar solid fermentation were determined.In the alcohol fermentation stage,C.lusitaniae single strain fermentation can rapidly produce a large amount of alcohol;alcoholicity increased by 15.4% when L.paracasei and C.lusitaniae mixed fermentation;H.uvarum,C.lusitaniae and L.paracasei mixed fermentation effect is the most excellent.In the acetic acid fermentation stage,large amounts of acetic acid and acetoin were produced while C.lusitaniae and A.pasteurianuss were mixed.The total acid content of C.lusitaniae,A.pasteurianus,and L.paracasei mixedferments increased by 12%,the content of acetoin increased by 89.79%;The total acid content and acetoin content of the vinegar obtained by the mixed fermentation of five dominant strains were the highest,which were 46.38 g/L and 15.87 g/L,respectively.4.The optimal strains combination for solid fermentation vinegar was determined,and the influence of each dominant strain on the characteristic flavor of the fumigated vinegar was verified.While the combination of H.uvarum,C.lusitaniae,L.paracasei,A.pasteurianuss and B.zhangzhouensis mixed fermentation,it produced more varieties and higher content of the characteristic flavor substances of Liangzhou fumigated Vinegar than other combinations.The content of acetoin,butadione and tetramethylpyrazine produced by the combination fermentation of five strains of vinegar was higher than that of Liangzhou fumigated Vinegar,however,the contents of esters such as ethyl acetate and phenylethyl acetate were lower.Among them,C.lusitaniae plays a key role in the formation of benzene ethanol,phenyl ethyl acetate and tetramethylpyrazine.H.uvarum was able to metabolize a certain amount of tetramethylpyrazine and butadiene.C.lusitaniae and H.uvarum jointly promoted the formation of ethyl acetate.A.pasteurianuss and L.paracasei were the main microorganisms that produced acetoin.L.paracasei was not conducive to the formation of tetramethylpyrazine.B.zhangzhouensis was beneficial to the formation of tetramethylpyrazine.5.The feasibility of inoculating dominance flora for brewing vinegar was evaluated.The results of sensory evaluation showed that the quality of vinegar produced by co-fermentation of the five dominant strains was the best,especially the addition of L.paracasei could improve the taste and flavor of vinegar,which was the closest to the quality of traditional Liangzhou vinegar.In a word,the five dominant strains in the trial were co-fermented to produce vinegar,which could maintain the quality of vinegar.It was proved that these dominant strains played decisive role in the formation of characteristic flavors during the process of brewing Liangzhou fumigated vinegar.They can provide the source of fermentative strains for modernization of traditional vinegars.