Abstract

The edible natural pigments extracted from plant organs become steadly popular to consumer because of those physiological functions desirable for food preservation and human health in recent years. There are a number of colored rice genotypes from light brown to blackish purple via reddish brown and purple. Some researchers reported their results on extraction recipes and identification of chemical structure of the pigments from the colored rice. The pigments extracted from colored rices can be largely divided into two types of anthocyanin and tannin pigments. Anthocyanin pigments are mainly contained in purple or blackish purple rice while tannin pigments are mainly contained in brown or reddish brown rice. Some brownish purple rices showed two peaks of tannin and anthocyanin pigments simultaneously. Purple rices showed better extraction of pigments in $0.1\%$ HCl-contained $80\%$ methanol or $0.5\%$ malic-acid-contained $80\%$ ethanol, while red rices revealed better extraction of pigments in $0.01\%$ citric-acid-contained $80\%$ ethanol. The anthocyanin pigments are generally unstable to heat, light and acidity of solution. The pigments extracted from colored rice can be preserved stably under the dark and cool(<$5^{\circ}C$) condition and at pH $2.0\~4.0$. The anthocyanin pigments of purple rice are mainly composed by cyanidin-3-glucoside (chrysanthemin). The other pigment fractions in purple rice were identified to peonidin-3-gluco-side, malvidin-3-galactoside(uliginosin) and cyanidin-3-ramnoglucoside(keracyanin). The pericarp coloration of purple rices is controlled by three complimentary genes C (anthocyanin), A(activator) and $Pl^{w}$(purple leaf) genes, while the red rices are expressed by complimentary interaction between Rc(basic substance of pigment) and Rd(distribution of pigment) genes or C and $Pl^{w}$ genes. Recently, the antioxidation and antimutagenic activity in main component of anthocyanin pigments extracted from colored rice were identified. The natural pigments from colored rice can be useful for beverages, cakes, ice scream, cosmetic and so on.

Keywords

• Colored rice;
• Plant pigments;
• Anthocyanin;
• Tannin;
• Antioxidants;
• Food additives