Pasting and rheological properties of rice starch as affected by pullulan.

Effect of pullulan (PUL) on the pasting, rheological properties of rice starch (RS) was investigated. The swelling power, amylose leaching, and confocal laser scanning microscopy (CLSM) observation of the samples were also conducted to explore the possible interaction between starch and pullulan. Rapid visco-analysis (RVA) showed that PUL significantly changed viscosity parameters of rice starch-pullulan (RS-PUL) mixtures. Dynamic rheological measurements revealed that the modulus (G', G″) of the mixtures increased with the increase of pullulan concentration from 0.01% to 0.07%, but then decreased with the increase of pullulan concentration from 0.07% to 0.50%. The pasting and rheological properties of samples indicated that pullulan could blend well with rice starch and promote the gelatinization of starch granules at low concentration of pullulan, but suppress the gelatinization of starch granules at high concentration of pullulan. The results of swelling power, leached amylose and CLSM observation of samples further suggest that the interaction between starch and pullulan occurred in the RS-PUL system and the interaction was hypothesized to be responsible for these results.