Bacterial Communities And Profile Of Aroma Compounds: A Correlation Study In The Process Of Jujube Brandy Fermentation

Jujube brandy,commonly known as Zaogangzi is a kind of special alcoholic beverage made out of Jujube,produced by solid fermentation and distillation.It produced in Hebei Province Taihang Mountains area,had thousands of years of brewing history.It’s of great significance to research the forming mechanism which determined the brandy’s yield and quality.The volatile compounds of jujube brandy had been studied in the early,however,the research about the relationships between bacterial compositions and aroma compounds has not been studied yet.This experiment take the fermented grains of jujube brandy as research object to study the composition of jujube brandy bacterial communities,the relationships of bacterial compositions with aroma compounds and physical and chemical indicators.Meanwhile,3 aroma-producing bacteria were selected.The main results are as follows:1.The physical and chemical indicators and aroma components in jujube brandy fermented grain were determined.Gas chromatography-mass spectrometry(GC/MS)was used to isolate and identify volatile compounds,a total of 48 volatile compounds were identified,comprising 22 esters,7 alcohols,5acids,7 aldehydes,4 ketones,and 3 phenols.In these aroma compounds,esters content is the highest.High performance liquid chromatography(HPLC)was used to identify amino acids and organic acids.Proline,aspartic acid and glutamic acid contents are the highest.Acetic acid,malic acid,lactic acid and succinic acid are the main organic acids in the jujube brandy fermentation.During the fermentation process,the pH value decreased obviously,the reducing sugar content,alcohol degree,moisture content and the temperature first increased and then decreased slowly.The total acid first increased,then decreased,and finally remained constant.2.16 S r DNA MiSeq sequencing technique was used to investigate bacterial composition in the jujube brandy fermented process.There are 413 bacteria genus were detected and classified,and 27 bacteria genus relative abundance over 1%,including Lactobacillus,Acetobacter,Lactococcus,Bacillus,Pseudomonas,et al.Among them,Lactobacillus and Acetobacter are in the dominant position.3.Partial least squares regression(PLSR)was used for elucidating the relationship between bacterial community and aroma compounds during the fermentation.The result shows that Lactobacillus significantly correlated with ethyl octanoate,phenethyl acetate and ethyl undecanoate.Acetobacter and Bacillus significantly linked with ethyl hexanoate,ethyl pelargonate,ethyl caprate,ethyl benzoate,Lactococcus and Pseudomonas seemed to be well correlated with ethyl laurate,ethyl tetradecanoate and ethyl 3-phenylpropionate.Burkholderia significantly correlated with isoamylol,benzyl alcohol,phenylethyl alcohol and benzeneacetaldehyde.Moreover,Acetobacter and Bacillus significantly linked with amino acids.Acetobacter and Lactobacillus positively correlated with moisture content and alcohol degree,and negatively correlated with reducing sugar content and pH value.Bacillus and Pseudomonas positively correlated with pH value and reducing sugar content,negatively correlated with moisture content and alcohol degree.4.Three aroma-producing bacteria were filtered from the fermented grains,and identified respectively for Bacillus Pumillus,Klebsiella Oxytoca and Bacillus Amyloliquefaciens.Pure culture fermentation product of 3 strains bacteria were determined by GC-MS,the common productions include acetic acid,benzyl alcohol,phenylethyl alcohol,2,3-butanediol,et al.Jujube juice fermentation model test with the 3 pure bacteria respectively,compared with blank control group,found that the volatile flavor substances content in experimental groups were higher than control group.It suggests that these bacteria have the ability to produce aroma substances.This paper studied the flavor substances and bacteria community diversity in the jujube brandy fermentation process,and carried on the correlation analysis.These results provided a train of thought for flavor adjustment,and provided theoretical supports to improve the quality of jujube brandy.