Structure, gelatinization, and digestion characteristics of starch from Chinese wild rice

Abstract

Two wild rice starches were isolated from Erhai in Dali, Yunnan Province (EWR) and Xinghua in Taizhou, Jiangsu Province (XWR), China, and compared with black rice (BR) starches, its structure, gelatinization and starch digestibility in vitro were studied. The results showed that the apparent amylose content of starches in EWR and XWR was 19.82% and 20.33%, respectively. The starch granules were irregular polygons and all were A-type crystals, with relative crystallinity of 25.6%~26.65%, similar short-range ordered structure and layered structure, and the thickness of the semi-crystalline layer ranged from 9.82 nm to 9.97 nm. XWR and EWR starches had exhibited the same gelatinization temperature range, enthalpy of gelatinization (ΔHgel) and swelling power, but XWR starches was higher than EWR in the gelatinization temperature and lower than EWR in the solubility. The rapidly digestible starch (RDS) content of wild rice starches in the two regions was low, only 3.63% and 37.32%, whether it was raw starches or gelatinized starches. After gelatinization, the RDS and slowly digestible starch (SDS) content were significantly increased and the resistant starch (RS) content was decreased, but the RS content was still higher than the common grains. Therefore, the wild rice starches are more suitable for processing and producing resistant starch products. Extracting starch from Chinese wild rice can provide guidance and reference for its application in edible and non-edible products, and promote the development and utilization of Chinese wild rice. Abbreviations: EWR, wild rice from Erhai in Dali, Yunnan Province; XWR, wild rice from Xinghua in Taizhou, Jiangsu Province; RDS, rapidly digestible starch; SDS, slowly digestible starch; RS resistant starch; TS, total starch; To, onset temperature of gelatinization; Tp, peak temperature of gelatinization; Tc, conclusion temperature of gelatinization; ∆Hgel, enthalpy of gelatinization.