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Understanding red rices—Difference and similarities.
J. MANFUL (1), C. C. Grimm (2), J. Gayin (3). (1) Africa Rice Center, Cotonou, , Benin; (2) USDA-SRRC, New Orleans, LA, U.S.A.; (3) University of Guelph, Department of Food Science, Guelph, ON, Canada

Oryza glaberrima, most commonly known as “red rice” in reference to the red pericarp, and Oryza sativa are the two forms of rice that are cultivated. In terms of growing area, O sativa outstrips O glaberrima. Cooking time is usually longer than white rice as their pasting temperatures are higher than white rice and they have a nutty flavor and sweeter taste. Red rice being usually whole grains is a good source of three kinds of anti-oxidants, water soluble, insoluble and fat soluble. Due to their brittle grains, red rice varieties give lower head rice yields. While compounds such as 4-ethylphenol (musty) and 2, 4-heptadienal (fruity) have been found to be pear to O glaberrima, others such as 2-ethyl-1-hexanol and alpha-copaene have been found in relatively larger concentrations in red rice than white rice. In terms of amylose content, red rices are mostly intermediate and high amylose rice types. Comparative studies of the thermal and molecular characteristics of starches of red and white rices showed both differences and similarities. While their melting transition temperatures were similar, red rices had higher gelatinization transition temperatures than the sativas. The starches of both types showed A-type X-ray diffraction pattern. Although starches from both species were similar in terms of the major group of short B-chains in their amylopectins, red rices had greater amount of “fingerprint” Bfp-chains and higher degree of polymerization than white rices.

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