Understanding the application-related features of sweet potato starch varying in multi-scale supramolecular structure

Abstract

Understanding the application-related features of sweet potato starch (SPS) is necessary for its utilization, which remains limited. Here, seven starches isolated from different sweet potato varieties (HA, SS, YSA, YSB, YSC, YSD, and YSE) were used. It was confirmed that the multi-scale structure possesses significant effects upon the application-related features of SPS. Relatively thinner crystalline lamellae contributed to less resistance to hydrothermal effects and thus increased peak viscosity (η_p) value, while thicker crystalline lamellae and smaller granule size resulted in elevated paste stability under shearing. The synergism of amylose content and molecular orders on digestion rate (k) was also observed, and a higher proportion of stable molecular orders and high thermal stability resulted in an attenuated k. Consequently, the YSA starch with the highest proportion (ca. 0.63) of stable long-range molecular orders (indicated by the high melting temperature: ca. 63 °C) within the starch granule could restrict enzymes' diffusion and permeation towards the starch matrices, and thus elevated resistant starch (79.66 %), possessing huge potential for designing low glycaemic index foods. Additionally, the higher amylose content of the HA starch (15.14 %) and the YSB starch (15.31 %) may contribute to the amylose aggregation and the amylopectin recrystallization, and thus increased gel strength.