The Research On The Influence Of Contamination Of Lactobacillus Brevis (49#) In The Different Stages Of Beer Fermentation Process On The Beer Quality

Beer has been known as the safe beverage, which is not easy to be spoiled, because of its excellent microorganical stability. However, beer fermentation is a complex process, although spoilage is rarely happened, there are still some spoilage microorganisms called beer spoilage bacteria that can grow well in the beer, Lactobacillus brevis is the most common beer spoilage bacteria significantly influenced in the beer fermentation.This test was carried out by simulating the beer fermentation process, and inoculating 49# in different stages of beer fermentation(beer fermentation stage, beer storagestage, the finished beer culture stage). The research was performed in two ways to study the influence of contamination of 49# on the beer quality in beer fermentation process, one is with the same bacteria concentration, and the other is with the different bacteria concentration. The flavour compounds, organic acids, biogenic amines and sugar of periodic samples in different stages of the beer fermentation process were analyzed by GC and HPLC to study the influence of Lactobacillus brevis(49#) in the beer fermentation process.The same amount of 49# was inoculated in the different stages of beer fermentation process. Periodic sampling in different stages of the beer fermentation process to study on the aspects of the flavor compounds, organic acids, biogenic amines and sugar, was used to make an inspect on influence of contamination of the same of Lactobacillus brevis(49#) in the different stages of beer fermentation process on the beer quality. The research findings were as follows: Virtually, 49# has no significant impact on the content of sugars and flavor compounds produced during the fermentation of beer. For the biogenic amines, inoculating 49# in each stage along with the progress of the beer fermentation, would slightly decrease the amount of tryptamine and histamine in beer. But as long as the contamination of 49# occurs in any stage of beer fermentation, the amount of beer tyramine will significantly increase. For the organic acids found, inoculating 49# in each stage along with the progress of the beer fermentation would slightly increase the amount of glyoxylate. And the amount of lactic acid would increase when the contamination of 49# occurs in the beer storage stage.Different amount of 49#(0.5%, 1%, 2%) was inoculated in the different stages of beer fermentation process. Periodic sampling in different stages of the beer fermentation process to study on the aspects of the flavor compounds, organic acids, biogenic amines and sugar, was used to make an inspect on the influence of contamination of different amount of Lactobacillus brevis(49#) in each stage of beer fermentation process on the beer quality. The research findings were as follows: inoculating different amount of 49# didn’t influence significantly on the flavor compounds but influence some extent on the organic acids in beer. Since 49# was assigned as lactic acid bacteria, it is obviously the amount of lactic acid would be increase in beer. Inoculating different amount of bacteria do some effect on the biogenic amines in beer, among which tyramine was influenced most significantly and tryptamine was influenced slightly in beer. Beer fermentation is a sugar consuming process, so different amount of bacteria make little effect in the sugar content in beer but influence slightly on the amount of maltose.