Effects of phosphate salts on extrusion behaviour of rice

A study on the effect of addition of Na2HPO4, and NaH2PO4 with a change of process variables, on the extrusion behaviour of rice grits, was made. The extruder die pressure and specific energy consumption (SEC) and extrudate properties such as expansion, density, water absorption and water solubility indices, aqueous dispersion viscosity, before and after cooking, and shear-thinning index were analysed. Second order polynomials were used to model extruder parameter and product characteristics. Addition of NaH2PO4 to rice grits decreased die pressure, SEC of extruder and expansion of extrudates, and increased water absorption and solubility indices and aqueous dispersion viscosities of extrudates. Na2HPO4 also showed a similar effect on die pressure, SEC of extruder and expansion of extrudates whereas the reverse was observed for water absorption and solubility indices and aqueous dispersion viscosities of extrudates.