INFLUENCE OF FACTORS ON THE BITTERNESS AND SENSORY TASTE IN PROTEIN HYDROLYSATE FROM SPENT

Abstract

Spent brewer’s yeast, obtained after the main fermentation stage, is a rich- in-protein source (protein content accounts for 48 - 50 % dry matter). In order to use efficiently this protein source for using in food industry, it was hydrolysed by different methods into mixtures of peptides and amino acids. So that it has a wide range of applications in food. It can be used as emulsifying agents in a number of applications such as salad dressings, spreads, ice cream, coffee whitener, cracker, and meat products like sausages. However, bitterness in hydrolysates is one of the major undesirable aspects for various applications in food processing. In this study, influences of factors (E/S ratio, pH and temperature) on bitterness of hydrolysate were studied to choose the best hydrolysis conditions by using flavourzyme, alcalase and neutrase. The bitterness of hydrolysate was determined by intensity sensory method (using quinine standard) and amino acid content was analysed by HPLC method. The result showed that bitterness of brewer’s yeast hydrolysate by flavourzyme is the lowest and that by neutrase is the highest. In particular, the bitterness of hydrolysates have reached values of 15.2–40.42 µmol quinine/l (FH - flavourzyme hydrolysate), 21–64.99 µmol quinine/l (AH - alcalase hydrolysate) and 34.62–64.26 µmol quinine/l (NH - neutrase hydrolysate), respectively. The hydrolysis conditions in using flavourzyme were chosen at 50 oC, pH 7, E/S ratio 7.1U/g and in using alcalase - at 55 oC, pH 8, ratio E/S 7.2 U/g, respectively. At this conditions, bitterness reached values 15.44 µmol quinine/l (in FH) and 21.16 µmol quinine/l (in AH).