Physicochemical and economic aspects of rice grain quality
1989
Juliano, B.O. | Gonzales, L.A. (International Rice Research Inst., Los Banos, Laguna (Philippines))
Variety, environment, and processing affect rice grain quality. In addition to the grain properties readily discerned by consumers, physicochemical factors are important. Varietal differences in moisture adsorption stress tolerance (fissuring resistance) contribute to stable high head rice yields even when the grain is overripe. Relevant starch properties are the major factor: amylose (linear starch fraction) content screened by iodine colorimetry and starch final gelatinization temperature (GT) screened by alkali digestibility value and gel consistency (or viscosity). Amylose content is correlated positively with water absorption and volume expansion during cooking and with cooked rice hardness, and negatively with cooked rice stickiness. Nutritional value is indexed by protein content. Studies on consumer demand for rice indicate that domestic consumers in Southeast Asia are willing to pay an implicit premium for grain quality characteristics. Consumers significantly prefer better milled (low percentage of brokens) rice, aroma, and intermediate amylose content. The thinness of the world rice market and the variability of consumer domestic demand for rice quality from one country to another make it difficult to establish an international consumer demand for grain quality. IRRI [International Rice Research Inst., Los Banos, Laguna, Philippines] is currently undertaking research on domestic and international demand for rice quality.
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