Abstract
The effect of potassium phosphate on potato and chickpea (CP) starches pasting, rheological, and textural properties were investigated using differential scanning calorimetry, rapid visco-analyser (RVA), viscometer, and texture analyser. Starch parameters were determined in 0.5, 1.0, and 1.5 M potassium phosphate at pH=5, 7, and 9, while distilled water was used as a control. Significant drop in the peak viscosity of potato starch was recorded in the presence of potassium phosphate at pH=5, but increased at pH=9 at the same salt concentration. CP starch exhibited significant increase in peak viscosity at higher pH and mixed behaviour in 1.5 M. The setback of potato starch increased significantly at pH=9 and 1.5 M salt concentration, while CP starch exhibited higher setback when cooked in 0.5, 1.0, and 1.5 M at higher pH. The peak gelatinisation temperature was higher in salt compared to the control, but CP starch showed gradual decrease at higher pH. The shear rate/shear stress data was fitted into power law model, where the flow behaviour index (n) was n<1 suggesting pseudoplasticity, whereas the consistency coefficient decreased at higher temperature indicating lower viscosity. The effect of salt concentration on CP starch was more pronounced compared to potato starch. The data was also fitted into Arrhenius equation to establish the effect of temperature on the activation energy (Ea), where CP starch exhibited higher Ea compared to potato starch. Higher gel hardness was noticed for both starch samples cooked in potassium phosphate compared to the control.