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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVING THE SENSORY QUALITY AND SHELF LIFE OF FRESH-CUT FRUIT PRODUCTS

Location: Food Processing and Sensory Quality Research

Title: Influence of amylose and protein contents on color of raw and cooked milled rice.

Authors
item Bett-Garber, Karen
item Champagne, Elaine
item Lea, Jeanne

Submitted to: United States Japan Natural Resources Protein Panel
Publication Type: Proceedings
Publication Acceptance Date: August 24, 2010
Publication Date: August 26, 2010
Citation: Bett Garber, K.L., Champagne, E.T., Lea, J.M. 2010. Influence of amylose and protein contents on color of raw and cooked milled rice. United States Japan Natural Resources Protein Panel.

Interpretive Summary: Rice consumers, particularly from countries for which rice is the staple, have strong preferences for the sensory properties of rice. Different countries have different requirements for the flavor and texture of rice, and within countries, a range of preferences can be found. However, when it comes to appearance, consumers worldwide desire raw and cooked rice with a high degree of whiteness. Little attention has been given to relating raw rice color to cooked milled rice color and, specifically, to determining the influence of amylose (a form of starch) and protein contents on the cooked color. In this study, the interrelationships of raw color, cooked color, amylose content, and protein content were determined using a set of 20 premium, aromatic and non-aromatic rice cultivars from rice-growing countries around the world. Higher protein contents were associated with whiter cooked rice and greater difference in whiteness between raw and cooked rice. Higher amylose contents were associated with less vivid and greener cooked rice. Rice with both low protein and low amylose had more vivid, but less white cooked rice than rice with higher amounts of these constituents. In general, rice goes from pale yellow to pale green and becomes less vivid or more gray upon cooking.

Technical Abstract: Traditionally, the color of milled rice is economically important. The whiter the rice the more it is preferred by consumers and the more value it has in the market place. Little attention has been given to relating raw rice color to cooked milled rice color and, specifically, to determining the influence of amylose and protein contents on the cooked color. Thus, the objective of this study was to determine the interrelationships of raw color, cooked color, amylose content, and protein content in rice using a set of 20 premium, aromatic and non-aromatic cultivars from rice-growing countries around the world. The rice cultivars were prepared according to customary cooking procedures within the countries of origin. Tristimulus color values (L*, a* and b*) were measured using the Hunter Miniscan XE Plus colorimeter on the rice before and after cooking. Chroma (C*) and hue angle were calculated from a* and b* values. Protein and amylose contents were not significantly correlated with the measured or calculated color measurements for raw rice. Protein and amylose showed moderate, significant associations with L* and a* and a*, b*, and C*, respectively, for cooked rice. Thus, higher protein contents were associated with whiter cooked rice and greater difference in whiteness between raw and cooked rice. Higher amylose contents were associated with less vivid and greener cooked rice. Rice with both low protein and low amylose had more vivid, but less white cooked rice than rice with higher amounts of these constituents. In general, rice goes from pale yellow to pale green and becomes less vivid or more gray upon cooking.

Last Modified: 9/2/2014
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