Comparison on structure and physicochemical properties of starches from adzuki bean and dolichos bean

Abstract

The major carbohydrate in pulse is starch. The structure and physicochemical properties of starches from adzuki bean (AS) and dolichos bean (DS) were systematically compared in this work. Results showed that the differences in morphology (oval to kidney), crystal type (CA-type) and sugar linkage between AS and DS were minor. However, AS had lower amylose content (26.64%) and larger granule size than DS (31.85%). AS showed higher relative crystallinity, ratio of 1047/1022 cm−1, single helix and double helix content (26.27, 0.95, 4.55 and 37.61%) than those of DS (24.08, 0.92, 4.76 and 27.49%, correspondingly), while AS may have loss of molecular order. Moreover, two kinds of anomalous linkages were detected by methylation analysis in AS and DS. These features contributed to higher swelling power, solubility, light transmittance and freeze-thaw stability of AS. Meanwhile, AS exhibited lower pasting and gelatinization temperatures, enthalpy and better pasting stability. The study indicated that amylose content, granular and crystalline structure of AS and DS may be responsible to their different properties. Hence, the study will improve the scientific basis on starches from adzuki bean and dolichos bean, and facilitate their utilization.