In the present study, we investigated the estimation method for the enzyme digestibility of steamed rice grains for sake making using alkali / urea solubility. Visual observation of the alkali / urea concentration solubilizing rice grains showed significant correlations with the DSC(= Differential Scanning Calorimeter)gelatinization temperature, the enzyme digestibility of steamed rice grains, and the retrogradation of steamed rice grains. The absorbance of iodine staining after soaking rice grains in urea solutions measured using a spectrophotometer also showed significant correlations with the enzyme digestibility of steamed rice grains and the retrogradation of steamed rice grains. Therefore, the enzyme digestibility of steamed rice grains for sake making can be estimated easily by the alkali / urea concentration solubilizing rice grains and the absorbance of iodine staining after soaking the rice grains in a urea solution. However, the polishing ratio and the moisture content of rice grains influenced the urea concentration solubilizing rice grains, although the existence of a white-core did not. In conclusion, these methods will be useful to estimate the enzyme digestibility of steamed rice grains for sake making, if the estimation standards according to the polishing ratio and moisture content of the rice grains can be determined.
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