RELATIONSHIP BETWEEN BITTERNESS OF BREWER’S YEAST HYDROLYSATE AND HYDROPHOBIC AMINO ACID CONTENT
Keywords:bitterness, enzymatic hydrolysis, amino acids, protein hydrolysates, brewer’s yeast spent.
Brewer’s yeast spent, 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 source, it was
hydrolysed by different methods. Protein hydrolysate products are normally mixtures of peptides
and amino acids. Protein hydrolysates have 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,
we used enzymatic mixture alcalase and flavourzyme, yeast treatment methods to hydrolyse
brewer’s yeast. The hydrolysate and fractions of protein hydrolysate obtained after filtration with
10 kDa and 3 kDa filters were used for determination of bitterness and hydrophobic amino acids
content. The bitter taste of hydrolysate was determined by sensory method (using quinine
standard) and amino acid content was analysed by HPLC method. The result showed the close
relationship between bitter taste and hydrophobic amino acid content. The bitter taste of protein
hydrolysate was reduced as the hydrophobic amino acid content decreased. When the bitter taste
(equivalent to quinine concentration) decreased from 16.25 μmol/l to 3.59 μmol/l, the total
content of hydrophobic amino acids in protein hydrolysate reduced from 1653 μg/ml to 932
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