Study On Fermentation Technology And Flavor Compounds Of Wheat Beer With Multiple Strains

As the craft beer market has become more and more popular,craft beer has grown significantly.Among them,the top fermented wheat beer is favored by more and more consumers because of its unique advantages of rich ester flavor and has huge market potential.However,most wheat beer in the market is fermented by a single strain,so this study conducted an innovative research on the basis of wheat beer,and adopted the mixed fermentation of multiple strains to explore its flavor characteristics and advantages.This article adopts D303,D07,D09,D10,D11,five typical all for wheat beer brewing yeast strains,wort liquid medium was used to simulate the wheat beer brewing process,yeast inoculation quantity 6 x 10~6cells/m L,20?under training,daily monitoring of a single strain fermentation,yeast strain growth curve,alcohol resistant ability,sugar consumption,heat resistance,acid resistance,determination of sugar content of the medium,ethyl production situation,until the end of the fermentation.On the basis of the experimental results,select D10 and D11,2 strains of yeast mixed fermentation experiments,each inoculation ratio 1:1,at the same time this two strains of yeast,the co-inoculation amount reached about 6×10~6cells/m L.According to the screening results,the optimum growth conditions of yeast under different conditions were analyzed by orthogonal experiment,and the brewing process was optimized by response surface methodology.The physical and chemical indexes and flavor substances of the finished wine were tested,and the comprehensive evaluation was carried out with the combination of sensory evaluation.The experimental results showed that the growth trend of yeast strains D10 and D11was roughly the same.D10 had a residual sugar of 4.8°P,D11 had a faster sugar lowering rate and a lower residual sugar of 3.8°P.The highest alcohol tolerance of yeast strain D11 was 15%,and that of yeast strain D10 was 5%.The highest heat resistance temperature of D10 and D11 strains was 35?,and they had good acid resistance,and they still grew well at p H 4.Through orthogonal test,the optimal growth scheme of multiple strains of yeast was as follows:sugar content of wort was 11°P,p H value was5.5,alcohol content was 5%.The wheat beer brewed by yeast strain D10 contains the largest amount of ester compounds,so it has the strongest aroma.In the co-culture process of D10 and D11,the factors affecting the growth of yeast strains were studied,such as nutrients,alcohol content,fermentation metabolites,etc.,and it was found that no cell filtrate had an interaction with the growth of yeast.The optimum brewing process was determined by response surface test.The optimized brewing conditions were as follows:fermentation temperature 20?,inoculation ratio of yeast strains D10 65%,inoculation quantity of yeast strains 2.3×10~7cells/m L.The flavor compounds,including esters,higher alcohols,volatile organic acids and acetaldehyde,were detected by gas chromatography-mass spectrometry(GC-MS).Wheat beer fermented by multiple strains has high content of ethyl acetate and isoamyl acetate,which determines the strong flavor of beer.High alcohol content,but alcohol-ester ratio is less than 5,give the wine mellow,at the same time,will not make the drinker show“headache”phenomenon.Mixed-fermentation with multiple strains can reduce the acetic acid content of wheat beer and reduce the acerbity of wheat beer,which can balance the flavor coordination of wheat beer.The most important aldehyde in mature beer is acetaldehyde,which is a normal intermediate product formed during alcohol fermentation.The concentration of acetaldehyde in wheat beer fermented by multiple strains was 3.07355mg/L,which was low and in line with the threshold value of 8?10mg/L.The original concentration of the finished wheat beer was 12.6°P,soaking capacity was 198s,p H 4.6,alcohol content was 5.34%vol,total acid was 1.6m L/100 m L,diacetyl was 0.04mg/L,color was 5.2 EBC,turbidity was 28.9 EBC,bitterness was 11 IBU,and true fermentation degree was 66.8.The physical and chemical indexes of the finished wheat beer were in line with the national standard.Combined with sensory evaluation,the sensory evaluation score of multi-strain fermented wheat beer was 96.8 points,and the wine body color was golden yellow.The foam is white and rich,and the hanging time is longer.The aroma contains malt wheat fragrance,hop fragrance and fermented ester fragrance,and each fragrance reaches the common balance point,no different fragrance;the taste is clean and neat,the taste is pure;full bodied,fresh and killing,it is a typical German wheat beer in line with national industry standards.