Antioxidant properties of rice grains with light brown, red and black pericarp colors and the effect of processing

The present work evaluated the concentration of total soluble phenolic compounds (TSPCs) and antioxidant activity (AOA) of rice grains with light brown, red and black pericarp colors and the processing effect on the concentration of TSPCs in the grain. Brown rice grains of ten ecotypes and six cultivars with red pericarp, one with a black pericarp and one with a light brown pericarp color, were evaluated. The concentration of TSPCs and AOA of rice grains with different processing (brown, polished, parboiled brown and parboiled polished) was determined, and the concentration of TSPCs was also determined in raw and cooked grains. Significant differences were observed in the concentrations of TSPCs and AOAs among genotypes with higher values obtained for grains with red and black pericarp colors, and a positive and significant correlation between these parameters was found. Parboiling reduced the TSPCs concentration in the grains due to the loss of part of them in the processing water, thermal decomposition and, possibly, interaction with other components. This reduction is related to the lower AOA in these grains. In a similar way, cooking also reduced the concentration of TSPCs, especially in brown and polished grains. (C) 2011 Elsevier Ltd. All rights reserved.