Brewing And Volatile Analysis Of A Tea Beer Fermented By Eurotium Cristatum And Ale Yeast

Beer is a famous beverage in the world.It is yeast which could generate the metabolites during the brewing period form the unique flavor of beer.Fuzhuan brick tea is one of dark teas,and “Golden Flower”-Eurotium cristatum is the key fungus which form the unique flavor of Fuzhuan brick tea.In this study,green tea and Eurotium cristatum were added during the stage of the wort boiling and the stage of beer fermentation,respectively.And we brewed a tea beer which mixed fermentation of ale yeast and Eurotium cristatum.Tea beer which brewed by the above method formed the unique flavor,and added the potential health care function because of Eurotium cristatum.Inspired by the special phenomenon and unique aroma during the process of fermentation in mixed fermentation tea beer,we speculated that Eurotium cristatum have relation with the behavior of yeast fermentation.Therefore,we hypothesized that there is interaction relationship between Eurotium cristatum and yeast during their metabolic process which lead to the final flavor of tea beer.In this study,three sample fermentation groups were set: yeast and Eurotium cristatum mixed fermentation group;yeast fermentation group alone,namely,the mixed fermentation group(Samples of yeast mixed with Eurotium cristatum)and a single fungal fermentation mixed group(yeast and Eurotium cristatum were separately mixed in a separate fermentation broth of tea wort).On this basis,the author conducted a sensory evaluation analysis based on triangular text,as well as GC-MS analysis.The experimental data were analyzed by multivariate data analysis including principal component analysis(PCA)and orthogonal correction partial least squares analysis(OPLS-DA).The results of this study are as follows:(1)Mixed fermentation tea beer in the fermentation process showed a unique fermentation phenomenon,such as gas production speed,foam delicate.From the physical and chemical indexes during the fermentation period,we found that the fermentation of Eurotium cristatum and the fermented yeast was more efficient:(a)improved the utilization rate of the microbial fermentation to the carbon source;(b)made the fermentation of the tea beer.(2)In the triangular test,all reviewers were able to accurately find a significant difference between the samples.The mixed fermentation group of beer has an amber and marked color,transparent and clear,all the tasting staff agreed that it has a strong ester incense(fruity,floral),pure taste,contain a slight bitter taste and a soft coordination of wine.While the mixture of single fungus fermentation group showing light yellow color,liquor turbidity,ester fragrance is not rich,slightly bitter taste.The fermentation of beer yeast and Eurotium cristatum changed the color,smell and taste of beer.This shows that the volatile components of the mixed fermented beer is not the simple plus of Eurotium cristatum metabolism and yeast metabolism.(3)Based on the qualitative and relative quantitative analysis by GC-MS,the author found that the volatile components of the two groups were significantly different.Some substances of esters,terpenes,alcohols,phenols,aldehydes and ketones changed significantly for the addition of Eurotium cristatum.OPLS-DA analysis revealed 10 significant differences between the two groups of samples.Most of these differential compounds are esters.The results of this study confirmed the hypothesis preliminary.The addition of the Eurotium cristatum did affect the fermentation process of the fermented tea brew yeast,and the introduction of the Eurotium cristatum in the tea beer fermentation stage could improve the color,smell and taste of the tea beer,the content of yeast typical metabolites(esters,volatile higher alcohols)also changed.