Effects of soy protein hydrolysates on the growth and fermentation performances of brewer's yeast

Abstract

Summary Soy protein isolate was hydrolysed with A lcalase, P apain, F lavorzyme and P rotemax, respectively, and further fractioned by ultrafiltration. The resulting soy protein hydrolysates ( SPH ) and their ultrafiltration fractions were used to examine their effects on the growth and fermentation performances of brewer's yeast. Results showed that degree of hydrolysis, molecular weight distribution and amino acid composition of SPH significantly affected the growth, viability and fermentation performance of brewer's yeast. The SPH prepared from different proteolytic enzymes exhibited distinct growth‐ and fermentation‐promoting activity for brewer's yeast. The SPH treated with P rotemax for 9 h and with the molecular weight below 3 kDa showed the highest growth‐promoting activity and induced more rapidly reducing sugar consumption and higher ethanol production. The relatively lower molecular weight and the hydrophilic and electropositive amino acid residues ( L ys, H is, A rg and I le) in SPH might be responsible for its functionality, promoting the growth and fermentation of brewer's yeast.