Effect of curdlan and xanthan polysaccharides on the pasting, rheological and thermal properties of rice starch.

The effects of microbial polysaccharides xanthan and curdlan on the pasting, viscoelastic properties and retrogradation of rice starch were studied. The additions of xanthan and curdlan increased the peak viscosities and decreased the final viscosities. The breakdown viscosities were increased by the curdlan addition, but were decreased by the xanthan addition. The dynamic viscoelastic results showed that the addition of xanthan in rice starch significantly increased storage modulus and loss modulus. The rice starch gel with xanthan addition exhibited higher resistances to the stress and produced a stronger microstructure network. The creep recovery data were well fitted by a 4-element Burger's model. Differential scanning calorimetry showed that the addition of curdlan and xanthan decreased the melting enthalpy values and retarded the retrogradation of the rice starch gel during storage at 4 °C for 12 days. The pasting and thermal results demonstrated that the addition of xanthan could significantly inhibited the retrogradation of rice starch. It was concluded that the addition of curdlan and xanthan modified the rheology of rice starch gel in different ways and interacted under different models based on their molecular structures.