Effect of different surface properties of nanosilica on retrogradation behavior and structures of thermoplastic cassava starch

Thermoplastic cassava starch (TPS) /nanosilica (nano-SiO2) composites were prepared by adding different surface properties of nanosilica. The effect of different surface properties of nano-SiO2 on the retrogradation kinetics, morphology, spherulites size, molecular interactions, short-range molecular structure and crystal type of TPS was investigated by differential scanning calorimetry (DSC), polarized light microscopy (PLM), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and 13C NMR. The results indicated that the retrogradation degree and rate of TPS containing hydrophobic nano-SiO2 were higher than that of hydrophilic nano-SiO2, and the spherulites were clearer. Hydrophobic nano-SiO2 could uniformly disperse in starch matrix. V-type crystal formed after adding hydrophilic nano-SiO2, and A + V types after adding hydrophobic nano-SiO2. The crystallinity of TPS adding hydrophobic nano-SiO2 was higher than that of hydrophilic nano-SiO2, but the crystal size and interplanar spacing were smaller. Hydrophobic nano-SiO2 could promote the formations of double helix structure and the ordered molecular structure.