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Impact of Presoaking on Flavor of Cooked Rice

¹USDA ARS Southern Regional Research Center, New Orleans, LA. ²Corresponding author. Phone: 504-286-4448. Fax: 504-286-4430. E-mail address: elaine.champagne@ars.usda.gov

Soaking rice in water for 30 min or longer before cooking is traditionally practiced in Japan, Korea, and other Asian countries. When soaked, the rice grains hydrate, develop cracks, and water is absorbed. Soaking facilitates uniform cooking and shortens cooking time. The cooked kernel is usually less firm. The present study was undertaken to determine the effects of presoaking on the flavor of cooked rice and whether flavor differences are associated with textural changes that could influence retention of aroma compounds. Eleven samples of short, medium, and long grain milled rice representing scented and nonscented rice and a wide range of amylose contents were presented to a descriptive sensory panel. For the set of all rice samples, undesirable sewer/animal flavor significantly increased and sweet taste significantly decreased with presoaking for 30 min. For individual rice samples, significantly higher sewer/animal intensity was observed with presoaking for the 2 Basmati rice samples and one of the U.S. long grain rice samples. When presoaked, sweet taste was significantly lower in one of the Basmati and Jasmine rice samples, the U.S. medium grain rice, and one U.S. long grain rice. Water-like metallic was also significantly higher in one presoaked Basmati sample. Presoaking also resulted in significant increases in summed negative flavor attributes and significant decreases in summed positive flavor attributes for the set of all rice samples. The effects of presoaking on texture, as measured by TPA hardness and chewiness, did not explain the observed increases in negative flavor attributes. An increase in free sulfur-containing free amino acids with presoaking could have resulted in an increase of their breakdown products, thereby contributing to the increase in sewer/animal flavor. The decreases in sweet taste and summed positive flavor attributes were likely the result of masking caused by the increases in sewer/animal and summed negative flavor attributes.