Amazake’ is nutrient-rich and physiologically active Japanese traditional food made by fermenting steamed rice with ‘koji’ mold. In this study, vitamin E species were determined as liposoluble antioxidants in amazake and changes in their compositions were examined during fermentation. Six vitamin E species were detected in brown rice amazake (BRA), and the total vitamin E content in BRA was six-fold higher than that in white rice amazake. This was consistent with the high radical scavenging capacity of BRA, which corresponded with the total levels of vitamin E and ferulic acid (FA). Although vitamin E levels in brown rice powder decreased during presaccharification, their levels were almost constant throughout saccharification and remained high in the final BRA product, suggesting the liposoluble antioxidants were stable under amazake preparation conditions. 4-Vinylguaiacol (4-VG) was found in amazake, and its content markedly increased during BRA manufacturing. Rice koji contained high levels of 4-VG produced from FA by the biological action of koji. The liposoluble antioxidative activities in BRA were due to vitamin E and 4-VG, in addition to FA, a phenolic compound thought to be the major radical scavenger. These observations suggested the superiority of traditional fermentation using koji and the advantage of BRA containing liposoluble antioxidants, such as vitamin E and FA.
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