Color, Pigments and Antioxidant Quality of Red Yeast Rice (angkak) Fermented by Various Rice Varieties

Abstract

The present study was designed to investigate color, pigments and antioxidant quality of methanolic extract of Monascus fermented various Thai varieties of rice compared with their unfermented rice. The glutinous rice (RD6) and non-glutinous rices (Khao Gaw Diaw 35, Khao Dawk Mali 105, Khao Dawk Mali Surin and Pathumthani 1) were fermented by Monascus sp. PSRU03 for 10 days at 30°C and dryness. The results showed that the L* value (lightness color) of rice was 63-69% decreased after fermentation, while the a* value (redness color) was 1,044-1,239% increased. The pigments and total extractable phenolic compounds were only found in monascal rice with the contents of 108.70 (RD6) – 353.4 (Khao Dawk Mali 105) units/g DM and 7.94 (RD6) – 12.33 (Khao Dawk Mali 105) mg GAE/g DM, respectively. In addition, yellow pigment was found to be the major constituent with 48-56% proportion of total pigments. Furthermore, antioxidant activity of red yeast rice extracts evaluated by DPPH radical scavenging and inhibition on lipid peroxidation methods was found to be better than the unfermented rice extracts and non-glutinous red yeast rice showed higher antioxidant activity than glutinous rice product.