Understanding Aspects of Carbohydrate Quality in Rice Related to Differences in Gastric Emptying Rate

Abstract

White rice is considered to have lower nutritional quality compared to brown rice due to the loss of its bran fiber during processing. However, components besides bran fiber that may improve the physiological effects of white rice, such as amylose content, slowly digestible starch (SDS) and resistant starch (RS), should be further defined. Delayed gastric emptying is associated with extended energy delivery and increased satiety, and may be influenced by these components. Temperature‐cycling was used to increase the SDS and RS fractions in moderately high amylose varieties of cooked white rice (~24 – 29% amylose) with digestion rates monitored in vitro for comparison with brown rice. Gastric emptying rates of rice in human subjects (n=12) were then measured using a 13C‐labeled octanoic acid breath test. In vitro starch digestion indicated that the SDS and RS fractions, in the moderately high amylose white rice, were increased following temperature cycling to levels similar to those in brown rice. Moderately high amylose varieties of white and brown rice also contained more SDS and RS in vitro, and trended to more delayed gastric emptying rates compared to the low amylose rice varieties. However, more delayed gastric emptying rates were still seen with brown rice. This may be a result of properties other than starch digestibility or amylose content that affect gastric emptying rate, such as those related to degradation of the physical form in the stomach.This research was supported by the Whistler Center for Carbohydrate Research and the Ingestive Behavior Research Center.