Physical, chemical and antioxidant properties of pigmented rice grown in Southern Thailand

Eight varieties of pigmented rice grown in southern Thailand, as a dehusked grain, were studied for their chemical compositions, antioxidant properties and color parameters. Moisture, protein, lipid, crude fiber and ash contents of all varieties were in the ranges of 5.96-8.19, 6.63-8.46, 1.44-3.47, 0.16-0.35 and 1.35-2.15 g/100 g (db), respectively. The iron and polyphenol contents in these rice samples were in the range of 0.91-1.66 mg/100 g and 58-329 mg GAE/100 g sample, respectively. The antioxidant capacity of dehusked rice grain extract was positively correlated (p 0.01) with polyphenol content (r =0.923). Rice grain color parameters (L*, a* and b*) had negative correlations (p 0.01) with iron content (r = -0.646, -0.654 and -0.791), polyphenol (r = -0.893, -0.851 and -0.928) and antioxidant capacity (r = -0.794, -0.629 and -0.770). The results showed that dark purple grain has higher iron content, polyphenol content and antioxidant capacities than red brown grain. This study can guide in the selection and production of rice varieties with enhanced nutritional qualities, suggesting the use of color parameters as a practical indicator of some key nutritional characteristics.