半固体状米糖化物を用いる清酒製造

Abstract

Instead of the parallel fermentation which is generally practised in sake making, we developed a step-by-step fermentation of moromi where the fermentation took place following a mashing process including steaming of rice and saccharification of the steamed riceSaccharification of steamed rice results in a sugar-rich solution containing some rice in a semi-solid state.The solution has been called reishu, a sweet drink. Firstly, methods to saccharify steamed rice in various states were compared.When the mixture of steamed rice, rice koji, and water was incubated at 55°C or 15°C, the steamed rice in the crushed state yielded 43 w/w% glucose at 55°C for 20 h incubation the largest amount among the other states of the steamed rice.After centrifuging of reishu, 9 to 43% of the reishu volume became supernatant (clear liquid). Some contamination problem with wild yeasts in reishu made (at 15°C) from crushed or pounded rice after steaming was solved by addition of ethanol (3% as a final) to the mixture and covering the top of the mixture with a thin plastic film.Tests on sake making with the use of reishu showed that reishu made from brown rice fermented more vigorously than that made from polished rice.Sake resulted from the fermentation test had higher acidity than that produced by the parallel fermentation.We think that the developed method would lead to make various kinds of sake, for example, sake with low alcohol content.