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United States Department of Agriculture

Agricultural Research Service

Title: Comparison of Physicochemical Properties and Starch Structure of Red Rice and Cultivated Rice

Authors
item Patindol, James - UNIV. OF AR
item Flowers, Amber - UNIV. OF AR
item Kuo, Meng-I - FU-JEN UNIV., TAIWAN
item Wang, Ya-Jane - UNIV. OF AR
item Gealy, David

Submitted to: Journal of Agriculture and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 7, 2006
Publication Date: March 7, 2006
Citation: Patindol, J., Flowers, A., Kuo, M., Wang, Y., Gealy, D.R. 2006. Comparison of physicochemical properties and starch structure of red rice and cultivated rice. Journal of Agriculture and Food Chemistry. 54(7):2712-2718.

Interpretive Summary: Red rice is considered a noxious weed in rice fields of the southern United States and many other parts of the world, primarily because it is the same species as cultivated rice, and therefore difficult to control in the rice crop, and because it has an undesirable red seed coat that is difficult to remove during milling. Several different red rice biotypes are found in the U.S. Although red rice seeds are often present as contaminants in commercial rice, little is known about their physical/chemical characteristics that are known to affect cooking quality in rice. Thus, representative red rice types from the southern U.S. were studied for their physical, milling, pasting and thermal (energy absorption) properties, chemical composition, and starch fine structure relative to popular cultivated medium-grain (Bengal) and long-grain (Wells) commercial rice varieties. All red rice samples were medium-grain but their physical/chemical properties were different from those of Bengal. Their amylose (non-branched starch molecules) and protein were generally higher, and their amylopectin (highly branched starch molecules) structure consisted of a higher percentage of the shorter branch chains and a lower percentage of the longer branch chains. Red rice starch pasting and thermal properties were similar to those of Wells. The red rice samples can be classified into two major clusters according to their kernel properties: one cluster with more resemblance to Wells, and another cluster with more resemblance to Bengal. Kernel starch structure and physical/chemical properties of red rice may offer an alternative way of classifying red rice in addition to traditional visually observable and genetic indices. Understanding the similarities and differences in these properties between red rice and commercial rice may improve insights into the effects of red rice contamination on overall rice grain quality.

Technical Abstract: Sixteen red rice accessions from southern United States were studied for their physical, milling, pasting and thermal properties, chemical composition, and starch fine structure relative to cultivated medium-grain and long-grain rice varieties. All red rice samples were medium-grain but their physicochemical properties were different from those of Bengal, a cultivated medium-grain rice. Their apparent amylose and crude protein were generally higher, and their amylopectin structure consisted of a higher percentage of the shorter branch chains (DP6-24) and a lower percentage of the longer branch chains (DP25-65). Red rice starch pasting and thermal properties were similar to those of Wells, a long-grain rice cultivar. The red rice samples can be classified into two major clusters according to their kernel properties by hierarchical cluster analysis: one cluster with more resemblance to Wells, and another cluster with more resemblance to Bengal. Starch structure and kernel physicochemical properties may offer an alternative way of classifying red rice in addition to phenotypic and genetic indices.

Last Modified: 9/21/2014
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