Effect of Hydrocolloids on the Rheological Properties of Wheat Starch.

The rheological properties of 5% starch alone and in the presence of 0"5%
guar, locust bean or xanthan gums were studied using a Rheotest 2 viscometer
at different temperatures. The 5% starch alone exhibited non-
Newtonian behaviour at 30°C, but upon gelatinization it exhibited
non-Newtonian shear thinning behaviour. In the presence of 0"5% guar,
locust bean or xanthan gum at 30*C itself, the flow behaviour index 'n' of
starch dispersions decreased and ranged between 0.83 and 090 indicating
shear thinning or pseudoplastic behaviour of the starch-gum dispersions.
After gelatinization, the effect of these gums was higher than at 30°C and
the flow behaviour index "n' decreased from t~64 to 0"34, 0.45 and t~25 in
the presence of 0"5% guar, locust bean and xanthan gum respectively.
None of the starch or starch-gum pastes studied exhibited the yield value
in the range of shear rates studied.