Saccharides Extracted from Rice Grains during Cooking Process and Effect of Monoglyceride on Them

Abstract

The saccharides extracted from rice grains with and without monoglyceride into aqueous layer during cooking process was investigated. Monoglyceride (0.5% of the rice) was added when the temperature of an electric rice cooker reached to 80°C. The aqueous layer was separated from rice by sieve at 0min., 5min. and 10min. after the starting period. The aqueous layer was further separated to two fractions, supernatant and residue, by centrifugation (12000rpm). After 10min. aqueous layer could not be separated, because it was perfectly absorbed into rice grains. The results were as following; 1) Amounts of saccharides in both fractions increased during cooking until 10min. 2) The supernatant of 0min. contained sucrose and glycerol except glucosides. Glucose and maltos increased until 5min. Amylose and dextrin increased until 10min.. 3) The residue contained amylose and partially hydrolyzed amylopectin, and amounts of the both components increased until 10min.. 4) Monoglyceride decreased amylose content in the residue of 10min., but pretreatment of the residue with DMSO revealed that little difference exist in amylose content between the both residue with and without monoglyceride. This observation suggested formation of amylose-monoglyceride complex in the residue. This complex should be absorbed again in the surface area of rice during cooking, hence the complex would significantly affect to physical properties of cooked rice.