Utilization of brewer's yeast cells for the production of food-grade yeastextract. Part 1. effects of different enzymatic treatments on solid and protein recovery and flavor characteristics

Yeast extract was produced from brewer's yeast of a beer factory by combine d enzymatic treatments using endoprotease, exoprotease, 5'-phosphodiesteras e, and adenosine monophosphate (AMP)-deaminase. Effects of enzyme combinati on, enzyme dosages and treatment sequence on the recovery of solid and prot ein, flavor and compositional characteristics were investigated. Exoproteas e dosage strongly affected the recovery of protein and degree of hydrolysis (DH) and sensory characteristics. When the yeast cells were treated using optimal combination of endoprotease and exoprotease (0.6% Protamex(TM) and 0.6% Flavourzyme(TM)), high solid recovery (48.3-53.1%) and the best flavor profile were obtained. Among various treatment sequences using multiple en zymes, treatment with protease followed by nuclease resulted in the highest 5'-guanosine monophosphate (5'-GMP) content. The optimal concentrations of both 5'-phosphodiesterase and AMP-deaminase were found to be 0.03%. After treatments using optimal combination of enzyme, enzyme dosages and treatmen t sequence for four enzymes, a high solid yield of 55.1% and 5'-nucleotides content of 3.67% were obtained. (C) 2000 Published by Elsevier Science Ltd .