The γ-oryzanol Content of Thai Rice Cultivars and the Effects of Gamma Irradiation on the γ-oryzanol Content of Germinated Thai Market Rice

Abstract

Thirty-nine Thai rice cultivars, including 17 non-colored rice cultivars and 22 colored rice cultivars (black rice cultivars and red rice cultivars), were investigated for γ-oryzanol content. The γ-oryzanol content of non-colored rice cultivars and colored rice cultivars was found to be 226.40 ± 17.50 μg/g to 411.80 ± 19.80 μg/g and 295.80 ± 15.40 μg/g to 459.80 ± 6.60 μg/g, respectively. Black rice cultivars seem to have higher γ-oryzanol content than do red rice and non-colored rice cultivars. The highest γ-oryzanol levels were identified in Khao Jao Dam Sa-Nit, a black rice cultivar, which contained 1.55 and 2.03 times more γ-oryzanol than Khao Man Bpoo, a red rice cultivar with lowest γ-oryzanol levels, and Khao Gor Kor 57, a non-colored rice cultivar with lowest γ-oryzanol levels, respectively. For further investigation, the effects of gamma irradiation on the γ-oryzanol content of four germinated Thai market rice cultivars, Khao Pathum Thani 1, Khao Gor Kor 31, Khao Gor Kor 41, and Khao Gor Kor 57, was investigated. The highest increase in γ-oryzanol content among the gamma irradiated rice cultivars was identified in Khao Pathum Thani 1 and Khao Gor Kor 31, which had γ-oryzanol levels approximately 1.27 times higher than that of the control rice (non-gamma irradiated rice). Our report contains basic knowledge about creating new rice lines that are rich in highly beneficial nutrients.