Effect Of Wheat Gluten Protein Hydrolysates On The Proliferation And Metabolism OF Yeast And Beer Brewing

Wheat gluten protein hydrolysates with different molecular characteristics were preparedby using controlled enzymatic hydrolysis technology. The effect of wheat gluten proteinpeptides on the growth and fermentation performance of yeast was examined in order toclarify the effectiveness of wheat gluten protein peptides in improving the fermentationperformance of yeast, and in making up the defects of the very high gravity brewing. Resultscan be concluded as follows:(1) Three commercial proteases (Alcalase, Protamex, Pancreatin) were used tohydrolysis wheat gluten protein, and the effects of different wheat gluten protein hydrolysateson propagation and fermentationperformance ofbrewer’s yeast were studied. Results showedthat wheat gluten protein hydrolysates with different degree of hydrolysis (DH) varied inpropagation and fermentation-promoting activity for yeast strains. Hydrolysates withPancreatin (DH16%) showed the highest propagation-promoting activity and could promoteyeast fermentation significantly, which resulted in the increases of biomass by37.0%and thefermentation time was reduced significantly by14%.(2) Four kinds of worts with different nitrogen compositions were used to examine theireffects on fermentation performance of brewer’s yeast. Results showed that both the nitrogencomposition and level had significant impacts on the yeast biomass accumulation, ethanolproduction, free amino nitrogen and sugars consumption rates. Worts supplemented with0.3%wheat gluten hydrolysates promoted significantly the growth and fermentation ofbrewer’s yeast.(3) The absorption pattern of peptides with different molecular weights (Mw) in yeastcells during wort fermentation was investigated. Yeast cells assimilated peptides with variousMw differently during fermentation. Peptides with Mw below1kDa decreased quickly and the rate of assimilation was more than50%at the end of fermentation, while for those withMw above10kDa almost could not be assimilated by yeast. Different level and nitrogencomposition had impact on the yeast fermentation performance, and peptides with Mw below1kDa were yeast’s favorite nitrogen.(4) Effects of wheat gluten protein peptides with different Mw on propagation andfermentation performance of brewer’s yeast were studied. Results showed that peptides withdifferent Mw varied in propagation and fermentation-promoting activity for yeast strainsunder the very high gravity brewing. Peptides (Mw <3kDa) showed the highest propagation-promoting activity and could promote yeast fermentation significantly. Supplementation withthese peptides during fermentation resulted in the increases of biomass, ethanol yield and theutilization rate of free amino nitrogen by30%,5%and11%, respectively. Moreover, the smallmolecular peptides (Mw <3kDa) had more suitable proportion amino acids, made thealcohols increase and the esters decrease, while supplementation with small molecularpeptides brought more harmonious taste.