Fermentation of ang‐kak in plastic bags and regulation of pigmentation by initial moisture content

Abstract

A method of producing ang‐kak (Chinese red rice) in plastic bags by Monascus sp. NP1 was developed. Advantages of the procedure are described. Fermentation of rice of various moisture contents gave results that agreed with previous findings that ang‐kak could be produced only at a relatively low initial moisture level. The mechanism by which the initial substrate moisture content regulated pigmentation was clarified. It was found that glucoamylase activity increased with increase in initial substrate moisture content. Therefore at high moisture content, as high enzyme activity was produced, glucose was rapidly liberated in amounts that inhibited pigmentation. The sugar was then transformed to ethanol. Addition of various amounts of glucose to rice of low moisture content before fermentation confirmed that the sugar at certain concentration had an inhibitory effect on pigmentation.