Abstract
Study was planned to modify the properties of rice starch with the use of different hydrocolloid gums. Pasting, rheological, textural and thermal properties of rice starch blends prepared with 0.5 and 2% replacement with arabic, xanthan, okra, flaxseed, cress seed and fenugreek gums were investigated by rapid visco analyzer measurements (RVA), hybrid rheometer, texture analyzer and differential scanning calorimeter (DSC). Peak viscosity was increased by the addition of all gums except arabic gum which decreased the peak viscosity when compared to control. Data obtained from hybrid rheometer revealed that dynamic mechanical loss tangent (tan delta) was increased by the inclusion of fenugreek and flaxseed gums, that shows an increase in viscous character because of the greater change in loss modulus (G '') than storage modulus (G'). It supports the hypothesis that there was interaction between amylose and these gums in the composite system. Consistency coefficient (k) was increased by the addition of xanthan, fenugreek and flaxseed gums at 25 degrees C. The data of flow behavior index (n) indicate that rice starch gum blends exhibited more psuedoplasticity than those of the control except flaxseed and okra gums. Activation energy values revealed that addition of gums regardless of their concentrations had increased the heat dependency of rice starch except xanthan which behaved contrarily. The hardness was significantly decreased with the inclusion of arabic, xanthan, cress seed and okra gums irrespective of their concentrations as compared to the control. The data obtained from DSC clarified that onset temperature (To) and peak temperatures (Tp) were increased as a function of gum type and their concentrations.