DISTRIBUTION OF FREE AMINO-ACIDS IN THE RICE KERNEL AND KERNEL FRACTIONS AND THE EFFECT OF WATER SOAKING ON THE DISTRIBUTION

The distribution of free amino acids within the milled-rice kernel was determined using the flours prepared consecutively by abrasive milling from the outer to the inner layers of the kernel. All free amino acids except arginine were present in the greatest quantities in the outermost layer of the 5%- milled kernel with a decreasing concentration gradient toward the center. Water soaking of the flours brought about increases in the contents of most amino acids and decreases in the glutamate and taurine contents. Taking into account the discriminative localization at the peripheral region of the milled-rice kernel and changes in contents during water soaking, glutamate, gamma-aminobutyric acid (Gaba), and arginine can be assumed to contribute to the taste of cooked rice. Gaba content in the germ increased remarkably with soaking under a slightly acidic condition, which indicates the potential for rice germ to be included in the diet of people with hypertension.