Studies on rheological properties of tamarind kernel powder, its derivatives and their blends with maize starch

Abstract

Pasting and flow properties of cooked solutions of tamarind kernel powder (TKP), its car☐ymethyl and hydroxypropyl derivatives, exhibited shear dependent and pseudoplastic flow behaviour characteristics. Chemical modification decreased the shear dependence of the solution viscosity as the degree of substitution increased. The solutions did not exhibit a yield stress at the concentrations studied. The effect of TKP and its car☐ymethyl and hydroxypropyl derivatives, at different concentrations, on the rheological properties of maize starch dispersions was also studied. The seed gum associated with starch, and the effect was maximum at 10% concentration of the former in the blend. This was evident by the lowering of pasting temperature and the synergistic increase in pseudoplasticity and yield value of the blend pastes. The TKP derivatives also showed maximum association with starch at 10% concentration in the blend but, in comparison to TKP, the degree of association decreased. Thus, the pasting temperature of the blend increased while the pseudoplasticity and yield value decreased as a function of DS/MS. At higher levels of modification, the association was decreased. These results have been explained on the basis of molecular association of the seed gum and its derivatives with starch molecules.