Antioxidants in milling fractions of black rice cultivars

Coloured rice, particularly black rice, has been shown to possess bioactive properties, and rice bran contains high levels of several antioxidant compounds. The aim of this study was to quantify the major antioxidant compounds in the milling fractions of black rice. Whole black rice of two cultivars (Oryza sativa cv. Heugjinjubyeo and O. sativa L. Heugkwangbyeo) was milled into rice bran and endosperm using the gradual milling system (85% milling degree). Relatively high levels of free polyphenols and flavonoids from two cultivars were found in the bran fractions (98.5 and 81.0 mg of polyphenols and 19.8 and 15.1 mg of flavonoids) while low levels were found in endosperm fractions. Compared to free polyphenols and flavonoids, low levels of bound polyphenols and flavonoids were found in all fractions. The black rice bran contained most of the antioxidant compounds, including phytic acid, γ-oryzanol, anthocyanins, and vitamin E homologues.