Abstract: In this study, pasting and rheological properties of native potato starch, potato starch phosphate ester and cationic potato starch were determined in the respective presence and simultaneous absence of guar gum and xanthan gum. The results indicated that the presence of guar gum enhanced the peak viscosity and pasting temperature of all three kinds of potato starches and deteriorated the thermal stability of starch pastes. The peak viscosities of native potato starch and potato starch phosphate ester rose and the thermal stability and pasting temperature declined due to the presence of xanthan gum, compared to opposite changes observed for cationic potato starch. Dynamic rheological studies revealed that the addition of xanthan gum considerably raised the G＇ and G＇＇ values and declined the tanδvalue of each kind of potato starch. The dynamic rheological properties of cationic potato starch were affected most obviously. By contrast, guar gum had no obvious effect on the dynamic rheological properties of all three kinds of potato starches. In static rheological studies, we found that starch pastes remained pseudo-plastic fluids despite the presence of either guar gum or xanthan gum, with shorted lag ring area and improved stability. Native potato starch and potato starch phosphate ester were more obviously affected than cationic potato starch. Moreover, xanthan gum had more obvious effect than guar gum. Further, our studies demonstrated that gum-starch interactions play a vital role in pasting and rheological properties of gum-starch complexes.

Key words: potato starch, modified potato starch, guar gum, xanthan gum, pasting properties, rheological properties