Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/27/2017
Publication Date: 5/1/2017
Citation: Chen, M., Bergman, C.J., McClung, A.M., Everette, J.D., Tabien, R. 2017. Resistant starch: variation among high amylose rice varieties and its relationship with apparent amylose content, pasting properties and cooking methods. Food Chemistry. doi:10.1016/j.foodchem.2017.04.170. Interpretive Summary: Physiologically, resistant starch is considered similar to soluble, fermentable dietary fiber. Its consumption, reportedly, improves gut health, adiposity and insulin resistance, and decreases cardiovascular disease risk factors and colon cancer risk. We evaluated a set of 40 high amylose rice varieties from around the world for resistant starch levels in cooked rice and found an approximately 2-fold difference. The highest ones had more than two-fold greater resistant starch levels than typical US long-grain rice. Two cooking methods were compared to evaluate the effects of water-to-rice ratio and the duration of cooking time on resistant starch levels using six varieties that had different functional properties. No difference in resistant starch level was found suggesting that preparing rice by common cooking methods does not degrade the resistant starch levels we report here. This research shows that that high resistant starch rice varieties can be developed through breeding and suggests that such rice can be part of a healthy diet.
Technical Abstract: Resistant starch (RS), which is not hydrolyzed in the small intestines, has proposed health benefits. We evaluated a set of 40 high amylose rice varieties for RS levels in cooked rice and approximately a 1.9-fold difference was found. The highest ones had more than two-fold greater RS concentration than a US long-grain intermediate-amylose rice. Multiple linear regression analyses were performed using data from all varieties, grown in three environments, either including all varieties or grouped by their genetic variant-types (paste viscosity-types distinguished by Waxy gene variants and gelatinization temperature-types by Starch Synthase IIa gene mutations), and results showed that apparent amylose content and pasting temperature were strong predictors of RS. Six varieties that varied for RS, paste viscosity and gelatinization temperature were cooked at a fixed rice-to-water ratio/time and in excess water/minimum-cook-time; no difference in RS concentration in the available carbohydrate of cooked rice was observed between the two methods. This indicates that cooking method does not degrade RS. This research shows that high resistant starch rice varieties can be developed through breeding and suggests that such rice can be part of a healthy diet.