Study On Fermentation Technology And Flavor Substances Of Stout Sour Beer

With the development of China’s economy and the enrichment of consumers’material lives,traditional industrial beer is increasingly unable to meet people’s needs,and thus requires continuous innovation in the market to meet consumers’needs.This article innovatively combined the classic representatives of two craft beers.In this experiment,single factor experiment,orthogonal experiment and response surface experiment model were used to produce a stout style sour beer by fermentation technology.Using barley malt,crystalline malt,caramel malt,rye malt,lactic acid bacteria,hops and brewer’s yeast as raw materials.We studied the influence of three important factors on the brewing process of stout style sour beer by single factor experiment:the proportion of crystalline malt in the brewing process,p H of the end point of wort acidification and the type of lactic acid bacteria added.The best technological parameters and significant values of important factors in the brewing process of stout style sour beer were verified based on the scores of sensory evaluation and orthogonal test.Further optimize the brewing process of stout style sour beer.Brewer’s yeast was an important source of flavor substances in beer,so three brewer’s yeast,US-05,S-04and BRY-97,were used for fermentation.After fermentation,physical and chemical indexes of the three finished beers were detected and analyzed.The non-volatile organic acids of wort and beer before and after fermentation were analyzed and compared by HPLC.HS-SPME was used to detect and analyze the volatile flavor substances in the fermentation products of three different yeasts,and the performance of the three brewers was comprehensively evaluated by sensory evaluation.Finally,the best brewer’s yeast for brewing stout style sour beer was selected.Response surface method was used to further optimize the brewing process of stout style sour beer.Single factor experiments were carried out by selecting the holding time of saccharification process at 72℃,the amount of lactic acid bacteria added in wort acidification process and the amount of yeast inoculated in fermentation process.With sensory score as response value,saccharification process holding time at 72℃as independent variable A,lactic acid bacteria addition as independent variable B and yeast addition as independent variable C,a response surface experimental model with three factors,three levels and response value were designed to explore the optimal brewing process parameters.Experimental conclusion:The proportion of barley malt in the raw material was70%,the proportion of caramel malt was 5%,the proportion of dark malt was 5%,the proportion of crystalline malt was 20%,the saccharification was held at 72°C for 20min,the p H at the end of acidification was 3.8,the lactic acid bacteria was used Lactobacillus casei,the addition of lactic acid bacteria was 1×10~7CFU/m L,the yeast type was BRY-97,and the yeast inoculum was 0.80 g/L,which was the best brewing process parameter.Under this brewing process,the average score of sensory evaluation of stout style sour beer was 57 points,the alcohol content was 6.98%vol,the fermentation level was 73%,the p H was 3.67 and other physical and chemical indicators also met the national standard.The beer fermented under this brewing process had the best flavor,harmonious taste,balanced sour and bitter taste,rich and delicate foam,and strong taste,which was the optimal brewing conditions.