Mirin-Making Using Long-Life Koji with Low Water Content

概要

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In an attempt to store koji longer than is now possible at room temperature, we investigated ways in which to dry it. Dried koji with a water activity (Aw) of 0.77 containing 0.11 g of water/g solid was prepared from fresh koji with an Aw of 0.88 containing 0.39 g of water/g of solid. Drying was found to be more efficient above 50℃. The most suitable conditions were at 55℃ under 760 mm Hg of pressure for 5-6 h (Method I) when fresh koji was prepared with crushed rice. This dried koji had 84% or more of the original enzyme activity. Other methods, such as drying at 55℃ under 20 mm Hg of pressure for 6 h (Method II), and drying by mixing fresh koji with dried steamed rice powder at 23℃ for 24 h (Method III) were also examined. For retaining enzyme activity after drying, Method III was theoretically the best. In practice, however, Method I was found to be efficient and inexpensive. For dried koji made using Method I, the α-amylase and neutral protease activities were 80% and over 90%, respectively, of the baseline values after 6 months of storage at 30℃. The number of bacteria in the dried koji was small, but the number of thermotolerant bacteria was almost unchanged. For mirin manufactured using dried koji which was stored for 4 months, the yield, properties and sensory qualities of the mirin were essentially the same as those obtained using fresh koji.
公益社団法人日本生物工学会の論文
1987-12-25