Characteristics of rice alpha-glucosidase
2005
Iwata, H.(National Research Inst. of Brewing, Higashi-hiroshima, Hiroshima (Japan)) | Isogai, A. | Utunomiya, H. | Itani, T.
In our previous study, we showed that rice alpha-glucosidase is the key enzyme for nuka-sake brewing. To examine the characteristics of rice alpha-glucosidase, we first measured the activities of alpha-glucosidase and alpha-amylase in brewer's rice, common rice (nonglutinous), glutinous rice, and upland rice. Upland rice had the highest alpha-glucosidase activity among the four kinds of rice. We then examined the storage characteristics of rice alpha-glucosidase and alpha-amylase in a short-term storage test. At 30 deg C, ca 30% humidity, the alpha-glucosidase activity of brown rice was about 120% of that in the control, but at 15 deg C, 70% humidity it was 80%. These results suggest that rice alpha-glucosidase is more susceptible to the water content of rice than to temperature. We also measured the activities of alpha-glucosidase and alpha-amylase in rice stored for a long time. In rice stored for 16-21-years, the alpha-glucosidase activity was 35-69% of that in the control, while the alpha-amylase activity was only 6-13%.
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