Influence of resistant starch and slowly digestible starch on rice texture.

Authors: Bett Garber, Karen; Lea, Jeanne; Watson, Michael; McClung, Anna; Chen, Ming Hsuan

Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2016
Publication Date: 7/2/2017
Citation: Bett Garber, K.L., Lea, J.M., Watson, M.A., Mcclung, A.M., Chen, M. 2017. Influence of resistant starch and slowly digestible starch on rice texture.. Rice Technical Working Group Meeting Proceedings. 2016:170.

Interpretive Summary: Seven diverse starch varieties were evaluated for fourteen sensory texture attributes. Three varieties were different from the other four for nine texture attributes. The percent of apparent amylose had some effect, but resistant starch was responsible for several of these differences.

Technical Abstract: Rice, comprised mainly of starch, serves as a significant source of caloric energy world-wide, therefore differences in starch digestibility are important to human health. Rice starch consists of three forms based on digestibility, rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS). With the increasing incidence of diabetes, there is interest in developing rice varieties which have less rapidly digestible starch, however it is unclear if that would impact palatability. The objective of this study was to assess the association of rice starch digestibility with cooked rice texture. Seven rice cultivars that differed in starch composition were milled, cooked, and presented to a descriptive panel for evaluation of 14 texture attributes. In addition, apparent amylose (AA) content and rapid visco analyzer viscosities (RVA) were determined. Principal component (PC) analysis was used to discover relationships between rice starch composition, texture attributes and physicochemical properties. Among the varieties, eleven of the texture attributes were significantly affected by resistant starch content. Eight of those attributes were different based on slowly digestible starch content. Greater contents of resistant starch caused the cooked rice to be harder, more springy, have greater intactness of chewed particles, required greater number of chews prior to swallowing, and have greater amounts of residual particles after swallowing. In contrast, greater contents of rapidly digestible starch caused the cooked rice to have more initial starchy coating, more surface slickness, to be more sticky, have a more uniform bite, and be more cohesive during mastication. The apparent amylose content impacted the results, but the unexplained nuances were elucidated by the interactions of three starch fractions. PC analysis of texture attributes and starch fractions resulted in three PC’s explaining 92.3% of the variance. PC1 (75.2%) was explained by apparent amylose content. PC2 (9.95%) was explained by the resistant starch content. PC3 (7.01%) was explained by slowly digestible starch content. PC analysis on RVA viscosities and starch fractions resulted in the three PC’s explaining 87.6% of variance. PC1 (49.1%) was explained by apparent amylose content, while PC2 (27.3%) was explained by resistant starch. PC3 (10.8%) was explained by slowly digestible starch content. These results demonstrate that in addition to apparent amylose content the starch fractions influence for the cooking quality.