A method for evaluating the quality of
koji from various analytical data was proposed.
Koji was digested in a solution containing acetate buffer, pH 5.0, at 55°C for 5 hr, and the filtrate of digestswas analyzed for specific gravity (Bé degree), glucose and amino acids. Moisture content (KM) of
koji was also determined. From these results, true digestion value (SS), true saccharification value (ST), total potency (TR=SS×ST), true amino acidity (S A), saccharification ratio (1/SS), amino acid ratio (SA/TR), and true glucose (SG) were calculated by equations respectively defined. When values of
koji for highly ranked sake (
ginjo-koji) and for common sake were compared during the process of
koji making, changes in measured values other than SA were smaller for the former
koji than for the latter at the time of
shimai-shigoto (2 nd mixing operation) and thereafter. When properties of
koji were plotted in a 3-axle radar chart prepared from axles of TR, SA/TR, and ST/TR,
koji for highly ranked sake showed lower TR and higher SA/TR than
koji for common sake. A 5-axle radar chart prepared from axles of SS, ST, SA, KM and SG showed that
koji for highly ranked sake gave almost regular pentagonal shapes, while
koji for lowly ranked sake gave irregular pentagonal shapes having high KM and SG.
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