Investigating the role and mechanism of water in E-beam modified sweet potato starch: Multi-scale structure, physicochemical properties, and in vitro digestibility

Aiming to investigate the role and mechanism of the effect of water on the structural, physicochemical, and in vitro digestible properties of starch during irradiation processing. This work used water pretreatment of sweet potato starch (12%, 25%, 50%, 75% and 100% water content) and then modification by E-beam (6, 12 and 24 kGy). The results showed that E-beam treatment preserved the polarization cross, growth rings, crystal types and FT-IR patterns of sweet potato starch. Also, E-beam induced the water molecule activation and free radical production, thus promoting starch degradation. Moreover, the short-range ordered structure, relative crystallinity, molecular weight, long-chain proportion, ΔH, viscosity and swelling power of starch decreased with increasing E-beam irradiation dose. In contrast, the short-chain proportion, solubility, and resistant starch content were improved. In addition, a synergistic effect was found between the water pretreatment and E-beam, i.e., the higher the water content of the starch, the deeper the modification by E-beam. Results obtained in this study can partially elucidate the role of water content in E-beam-modified starch and provide a basis for E-beam treatment of starch-based foods under different water levels.