Washing rice before cooking is common to remove dust and any remaining bran produced by the milling process. In this study, the effect of washing procedure on the textural properties of cooked rice, and its relations to starch leaching and the molecular structure of leached starch are investigated. Statistical analysis indicated that the washing procedure does not significantly affect either hardness or stickiness of cooked rice, but the interaction between rice variety and washing times on stickiness is significant. The components of leached materials, chain-length distribution (CLD), and molecular size of leached starch are significantly different from those of the surface materials, but not largely varied between rices with different washing times, which helps explain the molecular mechanism of the causes of these textural results. This indicates for the first time that, the adhering materials on the surface of raw rice grains do not contribute to the texture of cooked rice.
Keywords: Amylopectin; Amylose; Chain-length distribution; Hardness; Leached materials; Molecular size; Rice washing; Stickiness.
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