Abstract:The cassava starch was taken as the research object, which was modified by changing the type, content and ratio of enzymes. The structures of modified cassava starch were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), polarizing microscope (PLM) and differential scanning calorimetry(DSC). The results showed that with the increase of enzyme content, the ratio of glucoamylase and protease, the particle size of starch decreases and the surface is eroded in a large area to form pits. The crystalline region of starch is also hydrolyzed by enzyme to form hollow structure. The cross extinction of granule of starch was weakened or even disappeared. Different enzyme content, ratio and the addition of protease treatment did not make starch molecules form new functional groups. The diffraction angle 2θ of natural tapioca starch has diffraction peaks at 5.6 °, 15 °, 17.2 °, 22 ° and 24 °, indicating that the formation of B crystal. The starch modified by enzyme showed the A type crystal with diffraction peaks at 15 °, 17.1 °, 18 ° and 23 °. Enzyme modification delayed the gelatinization temperature of cassava starch from 65.43 ℃ to 69.11 ℃. The results show that different enzyme dosage, enzyme ratio and enzyme type will hydrolyze the surface and inside of cassava starch particles, and cause different structural changes. The experiment is helpful to reveal the mechanism of enzyme modification on cassava starch, and provides a theoretical basis for further research on the application of cassava starch.
