Protein Quality of High Protein Rice Obtained by Spraying Urea on Leaves before Harvest

Abstract

By spraying urea solution on leaves at the heading stage, high protein rice of 11% protein content was obtained without any loss in total amount of harvest. The protein quality of high protein rice was evaluated and compared with that of regular rice obtained without spraying urea solution. Assessment of amino acid contents in brown and polished rices and brans showed that the high protein rice contained approximately 44% more protein in its endosperm than the regular rice. Stepwise extraction of rice proteins with different solvents showed that 70% of the extra protein in the high protein rice was glutelin. Amino acid scores of the high protein and regular rices were not significantly different. Although there was no difference in electrophoretic pattern between the proteins of the two rices, the high protein rice showed more intense bands. Endosperm protein of rice is composed of two major subunits of approximately 32,000 and 21,000 in molecular weight. There was no difference between the high protein and regular rices in biological value, net protein ratio or net protein utilization. These results reveal that the high protein rice discussed in the present paper contains in its endosperm more protein of an equivalent quality than the regular rice.