Yeast extract is a soluble concentrate extracted from yeast such as Saccharomyces species (Brewer's yeast, Baker's yeast) and Torula yeast, and is used widely as a flavor enhancer containing inosinic acid and guanylic acid. It is manufactured by autolysis with endogenous enzymes, or by enzymatic treatment using exogenous enzymes.
Flavor components are classified into a nucleic acid type, protein type, and trace component type. Main flavor components of a nucleic acid type are inosinic acid (IMP) and guanylic acid (GMP). Yeast extract is manufactured using exogenous enzymes in the following steps; (1) destruction of mainly cell walls with enzymes for extraction of RNA, (2) production of adenylic acid and guanylic acid by treatment with nuclease (Enzyme RP-1G) that degrades DNA and RNA, and (3) conversion of adenylic acid to tasty inosinic acid by treatment with deaminase (Deamizyme 50000G ).
The flavor components of a protein type are amino acids and peptides. They are produced by treatment with protease (ProteAX , Protease M "Amano" SD) or peptidase (Peptidase R). Improvement of flavor is attained by converting glutamine released from yeast proteins to glutamic acid by treatment with glutaminase (GLUTAMINASE SD-C100S).
