Rheological characterization of cold water soluble rice (Oryza sativa) starch lactates and citrates prepared via alcoholic-alkaline method

The present study prepared citrates and lactates from rice starch which were then given alcoholic-alkaline treatment to produce cold water soluble (CWS) starches. These chemically modified starches were then compared in terms of rheological parameters to their hot water soluble starches (without alcoholic-alkaline treatment). FTIR spectra showed characteristic peak between 1710-1727 cm^-1 which confirmed esterification of starch via citrate and lactate groups. All samples demonstrated viscoelastic character i.e. storage moduli (G') exceeded loss moduli (G″). Both CWS and HWS starch citrates prepared by addition of 40 g citric acid to 100 g of starch exhibited highest G' and G″ suggesting highly structured and strong gels. Dynamic frequency and temperature sweep clearly showed that alcoholic alkaline treatment disrupted the granular conformity due to gelatinization of starch and as a result CWS starches were more susceptible to break down. Steady shear flow test confirmed that all samples were non-Newtonian while results of In-shear structural recovery measurements indicated anti-thixotropic behavior of CWS starch lactates.