Effect of RD43 rice (Oryza sativa L.) On starch digestibility, physicochemical properties, glycemic responses and food applications

Abstract

RD43 rice (Oryza sativa L.) is a cross-breed between Khao Jow Hawm Suphan Buri and Supan Buri1. It is characterized as a low amylose content, soft texture, and mild fragrance. However, its potential of metabolic health effect and food application remains unknown. In the present study, daily consumption of RD43 rice containing 14.10 g of undigestible starch for 12 weeks showed a significant reduction in fasting plasma glucose, insulin, HbA1c, and HOMA-IR in prediabetic participants. Furthermore, a significant decrease in body composition including body weight, body mass index, total body fat, and waist circumference was observed after the consumption of RD43 rice at 6th and 12th week. In comparison with conventional rice in Taiwan (Taiken9), ingestion of RD43 rice showed a significantly reduction in fasting plasma insulin and HOMA-IR at 12th week. In physicochemical and functional properties found that RD43 rice flour had higher amylose content (19.04%) than Hom Mali rice flour. It presented an irregular polyhedral shape and manifested a V-type crystalline structure and less crystallinity, which lead to a significant reduction of the water absorption index (WAI), swelling power (SP), water solubility index (WSI), gelatinization temperature, and pasting properties. Moreover, it had lower starch digestibility than Hom Mali rice flour due to a lower content of rapidly digestible starch (RDS) and higher content of undigestible starch. RD43 rice flour also exhibited a greater ability to disrupt cholesterol micellization and bind bile acids. In food application, steamed muffin made from RD43 rice flour showed lower starch digestibility than Hom Mali steamed muffin with no alterations of sensory attributes. Moreover, the substitution of wheat flour with RD43 rice flour (10-40% w/w) into noodles decreased starch digestibility, hydrolysis index, and RDS content together with increasing undigestible starch content. Comparing to the control noodles, 30% RD43 rice flour noodles slightly elevated WAI, swelling index (SI), cooking loss, and lightness (L*) as well as reduced redness (a*), yellowness (b*), and hardness with similar overall acceptability. In healthy men, consumption of 30% RD43 noodle caused a reduction in postprandial plasma glucose with increasing postprandial glucagon-like peptide-1 (GLP-1) and peptide tyrosine–tyrosine (PYY). In conclusion, RD43 rice has potential for food manufacturing and controlling glycemic, appetite as well as body composition in humans.