Preparation of resistant sweet potato starch by steam explosion technology using response surface methodology

Purpose: To obtain the optimal conditions and analyze the structure, gelatinization, and digestion characteristics of resistant sweet potato starch prepared by steam explosion (SE) technology.
Methods: A response surface method was used to investigate the effects of explosion pressure, pressure-holding time and autoclaving time on digestion resistance of sweet potato starch. The resulting resistant sweet potato starch was identified by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and for in vitro starch digestion rate.
Results: The optimum preparation conditions for resistant sweet potato starch were explosion pressure, 2.1 MPa; pressure-holding time, 56 s; and autoclaving time, 26 min. Under these conditions, digestion resistance of sweet potato starch of up to 37.73 ± 0.86 % was obtained. Infra-red spectra indicate that no new chemical groups appeared in the structure of the resistant starch. Furthermore, a gelatinisation-induced endothermic peak was observed in the DSC thermogram of potato starch at about 160 °C. The in vitro digestion data showed that the in vitro digestion rate had undergone a significant decrease.
Conclusion: Sweet potato starch treated by SE and autoclaving has lower digestibility and therefore, can potentially be used in food or medicine for diabetic patients.

Keywords
Resistant sweet potato starch; Steam explosion; Digestion resistance; Starch digestion rate; Response surface methodology