Structural characteristics and physicochemical properties of field pea starch modified by physical, enzymatic, and acid treatments

In order to meet industrial demands, field pea starch was modified by autoclaving (ACP), microwave cooking (MCP), and combined treatments of autoclaving with ultrasonication (UP), acid hydrolysis (AHP), or pullulanase debranching (PDP). The influence of different processing treatments on the structural and physicochemical characteristics of pea starch was investigated by X-ray diffraction (XRD), solid-state C-13 nuclear magnetic resonance ((CNMR)-C-13), Fourier transform infrared spectroscopy (FT-IR), small angle X-ray scattering (SAXS), differential scanning calorimeter (DSC), and scanning electron microscope. Processing of pea starch tended to decrease the long-range structural order with relatively lower values of crystallinity observed from XRD, whereas the double helical structure which is arranged at short range scale was enhanced to certain extents after different treatments. Microwave cooking was shown to be less effective than other treatments in promoting the formation of stabilized double helical structure, with the lowest values of crystallinity, degree of order (DO), double helix content, and gelatinization enthalpy obtained for MCP based on XRD, FT-IR, (CNMR)-C-13, and DSC observations. The experimental results also suggested that autoclaving had a less pronounced effect than the combined treatments of autoclaving-debranching, acid hydrolysis-autoclaving, and ultrasound-autoclaving on facilitating the formation of short-range ordered structure, with significantly lower values of DO, and double helix content obtained for ACP compared with AHP, PDP, and UP. This study was expected to provide a theoretical basis for the better understanding of the structure-processing-functionality relationship of starch polymers and to help the food industry to design novel starch materials with desirable functional properties.