Abstract:Cassava starch was modified using enzymes of different types at various amounts and at different ratios. The structures of the modified cassava starch were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), polarizing microscopy (PLM), and differential scanning calorimetry (DSC). The results show that with a larger enzyme dosage, a higher glucoamylase ratio, and the addition of protease, the particle size of starch decreases and particle surface erodes over a large area to form pits. The crystalline region of starch is also hydrolyzed by enzymes to form a hollow structure. The cross extinction of starch granules was weakened or even disappeared. Different enzyme dosages and ratios, as well as the addition of protease, did not cause starch molecules to form new functional groups. The 2θ diffraction angle of natural cassava starch exhibited diffraction peaks at 5.6 °, 15 °, 17.2 °, 22 °, and 24 °, indicating the formation of B crystals. The starch modified by enzymes demonstrated the A crystal patterns with diffraction peaks at 15 °, 17.1 °, 18 °, and 23 °. Enzyme modification increased the gelatinization temperature of cassava starch from 65.43 ℃ to 69.11 ℃. The results suggest that different enzyme dosages, ratios and types will cause different structural changes by hydrolyzing the surface and inside of cassava starch particles. The findings help to reveal the mechanism of enzyme modification on cassava starch, providing a theoretical basis for further research on the application of cassava starch.
