Characteristics of Shoyu Color and Separation of Color Components

Abstract

The color of shoyu has been studied by using parameter of color tone and fractionating color components with DEAE-cellulose.
A linear relationship was found between the logarithm of absorbance (log A) and wave length (450_??_650 mμ) in the color distribution of shoyu and melanoidin prepared from model system. It is proposed that change in log A per 100 mμ (designated as _??_A) can be used as parameter for color tone. When _??_A is large, color distribution exhibits bright tone, and when _??_A is small, it exhibits dark tone. Color tone of shoyu was brightened by heating or aging in the mashing process, while it was darkened by oxidation. Similar result was observed in the color of melanoidin prepared by heating amino acid and xylose in aqueous solution.
After desalting of shoyu by Sephadex G-15, color material of shoyu was fractionated into 8 peaks by DEAE-cellulose with stepwise elution. Color tones of each peak darkened according to the order of elution. When shoyu was heated, bright tone of color components increased, while dark tone of color components increased when it was oxidized. However, _??_A of color components was unchanged by heating or oxidation. Similarly, it is observed that dark tone of color components increased and color tone of color components was unchanged when melanoidin from glycine-xylose system was oxidized.
Thus, it is suggested that color material formed by amino-carbonyl reaction and color of shoyu consist of various color components having color tone from yellowish brown to dark brown and that the color tone depends upon the variation of amount of color components.