Production And Application Of Acidulated Malt For Beer Brewing

Acidulated malt is a specialty malt containing lactic acid,which can be used to improve the productivity and quality of wort and to regulate the flavor of beer.At present,China mainly relies on imported commercial acidulated malt,which is very expensive.Due to the lack of specialized domestic strains for acidulated malt production,the current small-scale preparation of acidulated malt suffers from insufficient acidity and the safety hazard of possible biogenic amines.This study designed demand-oriented screening indexes,screened lactic acid bacteria with high amylolytic activity,high acid production capacity and low biogenic amine production from barley and green malt samples for acidulated malt preparation.Furthermore,this study optimized the process to produce high quality acidulated malt,analyzed the quality of acidulated malt in depth,and finally applied the acidulated malt to beer brewing.The main research contents and conclusions were as follows:（1）A strain of lactic acid bacteria with high amylolytic activity,high total acid production capacity（calculated by lactic acid）and low biogenic amine production was screened from barley and green malt,with amylolytic activity of 4.43 U·m L^-1,total acid production capacity of 12.9 g·L^-1 and total biogenic amine production of 10.15 mg·L^-1.It was identified as Lactobacillus plantarum ZL-36 by 16S r DNA sequence analysis and could grow at barley germination temperature of 14°C.（2）In this study,the preparation process of acidulated malt was optimized.The 3%L.plantarum ZL-36 was added on day 1 of germination,green malt germinated for 4 days was transferred into water containing 1%yeast extract（water to malt dry weight ratio of 1:1）and fermented at 30°C for 48 h.The acidulated malt was obtained by drying at the end of fermentation,and the total acid content reached 3.4 g·100 g^-1,which was 36.00%higher than that of imported commercial acidulated malt.Scanning electron microscope observation and microbial community structure analysis showed that L.plantarum ZL-36 could quickly adapt to the environment of the malt surface,become the dominant bacteria and inhibit the growth of aerobic heterotrophic microorganisms.（3）Compared with basal malt,lactic acid soaked acidulated malt and commercial acidulated malt,the total acid,the content ofα-amino nitrogen and extract was higher,and the p H of mash decreased significantly in this study.The free amino acid content of acidulated malt was significantly higher than basal malt,commercial acidulated malt and lactic acid soaked acidulated malt,which were 43.76%、12.64%and 26.66%higher respectively.The free amino acid composition was more conducive to beer flavor control.The fermentable sugar composition analysis showed that the distribution and proportion of glucose,fructose,sucrose,maltose and maltotriose in the four kinds of malts were close.Compared with the other three kinds of malts,acidulated malt had the highest content of malic acid,lactic acid,acetic acid,citric acid and total organic acid content.The biogenic amine content of the acidulated malt was 14.86 mg·kg^-1,which was not significantly different from the basal malt,lower than that of the commercial acidulated malt and the acidulated malt produced with L.plantarum ZL-36had no safety concerns regarding biogenic amines.（4）Beer brewing experiments showed that the addition of acidulated malt shortened the fermentation period.Compared to lactic acid soaked acidulated malt and commercial acidulated malt,the acidulated malt had better sensory evaluation and reached 90.0.The addition of 15%acidulated malt can result in mellow taste in beer.The flavor composition analysis showed that the addition of acidulated malt increased the content of esters,alcohols and volatile acids in beer,which increased by 12.61%,7.68%and 14.61%compared to basal malt,respectively.