[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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When making the Japanese traditional spirit shochu, the pitching is commonly carried out by the addition of a volume of about 0.6% of fermenting mash. The re-pitching procedure is called “Sashimoto”. As a result of repeated sashimotos to the mash prepared with barley-koji, the yeast purity of S4 was found to decrease by a contamination of a wild yeast, WS1. On the other hand, repeating sashimotos for the mash prepared with rice-koji, the yeast purity was maintained at a high level. To clarify this finding, we investigated the differences in chemical components between barley-koji and rice-koji which affected the shochu yeast and wild yeast. In early stage of shochu mash, the amounts of glucose, formol-nitrogen and many amino acids, especially arginine, were extracted more from rice-koji than barley-koji. When arginine was added to barley shochu mash, the yeast purity of S4 was maintained at a higher level than that of the control（mash with no arginine added）during the repeated sashimotos. The higher assimilability of arginine of shochu yeast S4 may have caused the strain to be a hybrid of shochu yeast S2 and sake yeast K-1601 having a high assimilability of arginine. The results described above show that throughout repeated sashimotos, if the contents of glucose and nitrogen（amino acids）are kept at high levels during the entire fermentation period of shochu mash, the purity of shochu yeast S4 was kept higher, despite a high ethanol condition at the final stage of fermented mash. Another reason that the yeast purity of S4 was kept higher level under the high stress condition was that the plasma membrane H^＋-ATPase activity of S4 was higher than that of WS1, thereby ensuring S4's tolerance against high stress condition, and brought about a high growth rate. We concluded that to keep the purity of shochu yeast at a high level during repeated sashimotos depends on the yeast's specific growth rate, which was effected by the components of extracts from the koji used in the mash.

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Recently, the properties of Thai non-broken rice for the production of awamori have varied significantly among shipments imported from Thailand, and these variations make the production of awamori difficult. In the present study, we investigated the starch and protein properties of Thai rice used for awamori production compared with Nipponbare, which is used as a cultivar for sake making, because these properties have the possibilities of affecting the water absorption ratio and enzyme digestibility of steamed rice grains. The results of individual alkali solubility testing and DSC（＝ Differential Scanning Calorimeter）analyzing showed that the shipments of Thai rice have mixtures of different properties in gelatinization temperature and alkali solubility. The Thai rice of high gelatinization temperature had a lower content of short-chain（DP6-8 ＝ Degree of polymerization）of amylopectin structure than that of low temperature gelatinization and Nipponbare. This result indicated that the difference of the amylopectin structure was due to the starch synthase IIa activity from a previous report. The starch in Thai rice with a high gelatinization temperature retrogradated faster than that with a low gelatinization temperature. The analysis of protein composition showed no clear difference between the Thai rice with high gelatinization temperature and that with low gelatinization temperature although intense 60kDa protein bands were observed in Thai rice. From the above results, the mixture of cultivars in Thai rice may influence treatments of materials for the production of awamori.

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