|Bett Garber, Karen|
|LINSCOMBE, STEVEN - Louisiana State University Agcenter|
Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 12/30/2019
Publication Date: N/A
Technical Abstract: Resistant starch (RS) is a type of dietary fiber that resists digestion in the small intestine and passes to the colon to be fermented by microbiota. Its consumption is reported to improve gut health and insulin resistance while decreasing cardiovascular disease risk factors and the risk of colon cancer. Rice varieties higher in resistant starch are known to have lower glycemic index. Previously we identified non-mutant high-RS/high-amylose rice varieties from two diverse sets of germplasm collections. However, because amylose content is known to influence cooked rice texture, the impact of the higher RS content on sensory attributes needs to be understood. Eight high-RS rice varieties, five having high-amylose- weak paste viscosity (HAWP) and three having high-amylose-strong paste viscosity (HASP), along with US varieties of L202 (HAWP), Dixiebelle (HASP), Wells (intermediate-amylose), and Hidalgo (low-amylose), were selected for the study. All varieties were grown in field studies conducted in Arkansas and Louisiana. Apparent amylose content, protein and paste viscosity were determined. Fourteen cooked rice texture attributes which were divided into four chewing phases were evaluated by a human sensory panel. RS, the average of the 2 growing locations, of these eight high RS rice varieties ranged from 3.6-4.4%, and were 24-55%, 86-131% and 19- to 24-times greater than those of the high-amylose varieties (L202 and Dixiebelle), Wells, and Hidalgo, respectively. Across all high amylose rice varieties, RS correlated with apparently amylose content (r= 0.8). When only the intermediate gel temperature types were included, RS was correlated with pasting temperature (r= - 0.83). Cooked rice texture is known to differ based upon paste viscosity curves as measured by RVA, thus, the comparison of texture attributes of cooked rice was carried out within each of the HAWP and HASP classes separately along with the high-amylose US varieties (L202 and Dixiebelle), as well as, with the intermediate amylose variety, Wells. The texture attributes of most of the high-RS HAWP were not significantly different from those of L202 but were significantly different from Wells for 4 of the 5 attributes in phase I (evaluated with tongue without chewing)– initial starch coating, slickness, roughness and stickiness to lips; 1 of the 3 attributes in phase II (evaluated at first bite) – cohesiveness; 1 of the 3 attributes in phase III (evaluated during chewing) – uniformity of bite, and none of the 3 attributes in phase IV (evaluated after chewing or swallowing). The texture attributes of most of the high-RS HASP were not significantly different from those of Dixiebelle but were significantly different from those of Wells for 5 of the 5 attributes in phase I – initial starch coating, slickness, roughness, stickiness to lips, and stickiness between grains; 1 of the 3 attributes in phase II – cohesiveness; 2 of the 3 attributes in phase III (2 of 3) – cohesiveness of mass and uniformity of bite; and 1 of the 3 attributes in phase IV (1 of 3) – intactness of masticated particles. In conclusion, regarding the range in RS observed in these germplasm lines, higher RS content does not result in changes in cooked rice texture as compared with US varieties that have the same amylose/paste viscosity types, but they do hold promise to increase the nutritional and health beneficial value of rice.