清酒もろみにおける蒸米溶解の機作に関する研究
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概要
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In Japan, sake is a traditional beverage made from rice, rice-koji, and water. α-Amylase and glucoamylase are the most important enzymes in sake brewing; more recently, the role of acid protease has also been found to be important in the brewing process. The enzymes are usually supplied from rice-koji prepared by cultivating Aspergillus oryzae on steamed rice. It is known that at an early stage of sake moromi-mash fermentation, α-amylase extracted from rice-koji is adsorbed onto steamed rice in the sake moromi-mash, decreasing its activity in the mash. This study was carried out to explore the mechanism of adsorption of α-amylase produced from A. oryzae (Taka-amylase A; TAA) onto steamed rice in sake moromi-mash. α-Amylase was adsorbed onto white rice very well, but hardly adsorbed onto rice starch or deproteinized rice. We further found that α-amylase was adsorbed very well to oryzenin (glutelin), which makes up the greater part of rice protein. When acid protease attacked steamed rice in the sake moromi-mash, the protein in the rice decreased and the efficiency of α-amylase adsorption was reduced. From these results, the site of α-amylase adsorption in steamed rice was considered to be oryzenin. The results also suggest that α-amylase (TAA) combines well with proteins having basic amino acid residues, with intermolecular ionic bonding. It was presumed that ionic bonding occurred between the basic amino acid residues of oryzenin and the carboxyl groups of TAA, because oryzenin and TAA are oppositely charged in the sake moromi-mash (pH 4〜pH 4.5); the pI (isoelectric point) of TAA was 3.7 and that of oryzenin was 6.5. Finally, the use of acid protease and an α-amylase which does not adsorb onto rice was found to be the most effective means for sake moromi fermentation, promoting digestion of the steamed rice.
- 社団法人日本生物工学会の論文
- 1992-07-25