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 degrees 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.