Screening And Fermentation Characteristics Of Wheat Beer Yeast

With the rapid development of new technologies for beer and the increasing demand for diversified consumers,wheat beer has been sought after by consumers because of its unique taste.The classic wheat beer typically has a fresh,mellow texture,a turbid appearance and a rich"banana"and"clove"aroma.And this special aroma is produced by the metabolism of some Saccharomyces cerevisiae during the fermentation process.In this dissertation,wheat yeast was screened and the fermentation process was optimized by studying the yeast fermentation characteristics and the detection of flavor substances.From the seven Saccharomyces cerevisiae preserved in the laboratory,wheat brewer's yeast was screened by detecting the flavor of beer and the flocculating property of yeast,and finally two wheat beer yeasts WE and SA suitable for the above fermentation were screened out.The optimization of the fermentation process was performed on the yeast WE and SA,respectively,and it was found that the fermentation rate of the WE yeast during the fermentation at 20?was fast,the apparent fermentation degree was high,and the fermentation period was 11 days.Combined with the content of flavor substances,the optimal fermentation temperature of WE yeast was determined as 20?and the inoculum size was 4×10~6cells/mL.When the SA yeast was fermented at 22?,the characteristic flavor of isoamyl acetate and ethyl acetate in wheat beer was both.In accordance with the above criteria for fermented wheat beer,the acetaldehyde content is lower than that at 18?and 20?,which is conducive to beer maturation.Therefore,the optimal fermentation main temperature for judging the SA yeast strain is 22?,and the inoculation amount is 8×10~6cells/mL.As the concentration of brewer's yeast increases,the turbidity of beer will also increase,resulting in opaque appearance of turbidity,and with the prolonged storage time,precipitation will easily occur,and people will easily misunderstand beer spoilage.It was found through experiments that the suspension rate of wheat brewer's yeast decreased as the storage time prolonged,but stored at a low temperature of 5°C,the glucose concentration and maltose concentration was 0.4%-1.6%(w/v),and the mannose concentration was?1.2%(w/v)and carrageenan concentration in the 0.001%-0.004%(w/v)conditions conducive to increase the yeast suspension.