[in Japanese]

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[in Japanese]

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[in Japanese]

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In liquid cultures, the acid-unstable α-amylase (AU-amylase) of Aspergillus kawachii was produced at almost the same level as in a maltose medium when glycerol or glucose was used as a carbon source, while its production level was low compared with TAKA-amylase production by A. oryzae in a maltose medium. Although a sequence analysis showed an extensively high homology with TAKA-amylase gene, the AU-amylase gene depicted 64 base pairs of depletion in the promoter region. From the reporter gene analysis, it was suggested that the low expression level of AU-amylase was caused by deletion of the promoter region, while the unique expression mode on various carbon sources was due to the strain itself. In a manner similar to AU-amylase production, glucoamylase was also produced in A. kawachii (but not in A. oryzae) when glycerol or glucose was used as a carbon source.

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The relationship between the flavor of Imo-Shochu and the MTA (mono-terpene alcohols) was studied. The MTA investigated here were linalool, nerol, geraniol, citronelool, and α-terpineol. The results of thresholds for a 25% ethanol solution were 40-1000μg/l. The flavor evaluation tests for nerol and citronelool showed the ‘Imo-Itamisyu’. The ‘Imo-Itamisyu’ is a special flavor and was often detected with damaged sweet potatoes.
Abundant MTA were found in the stressed sweet potatoes, whereas there were none in the fresh sweet potatoes. The concentrations of MTA in Imo-Shochu produced from soft rot roots were found to be approximately 78 times higher than in those produced from healthy sweet potatoes. Furthermore, ‘Imo-Shochu’ produced from stressed sweet potatoes has a quality similar to a Muscat flavor; however, this could be ‘Imo-Itamisyu’.

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