Physical properties of pregelatinized and granular cold water swelling maize starches at different pH values.

The aim of this study was to investigate the influence of pH changes (3, 5, 7 and 9) on physical properties of pregelatinized (PG) and granular cold water swelling (GCWS) maize starches. In acidic pH, PG starches were fragmented; however, GCWS starches mainly reserved their granular integrity but were shriveled. For both modified starches the water absorption, cold water viscosity, textural parameters, turbidity and freeze-thaw stability of the samples decreased whereas water solubility increased at pH 3 and 5. On the other hand, alkaline pH did not bring about evident changes on morphology of PG starch but the surface of GCWS starch became smoother. Water absorption, solubility, rheological and mechanical properties, freeze-thaw stability and turbidity of the starch pastes increased at high pH values. Overall, both starches were more stable at alkaline pH compared to acidic pH values and GCWS starch was more resistance to pH changes than PG starch.