Physicochemical properties of microwaved starch blends from cocoyam (Xanthosoma sagittifolium) and pigeon pea (Cajanus cajan) for industrial applications

Abstract

The extracted cocoyam starch (100CYS) and pigeon pea starch (100PPS) were blended in three ratios (70CYS/30PPS, 50CYS/50PPS and 30CYS/70PPS) (%, w/w) and microwaved. The aim was to alter the compositional and some physicochemical properties of the starches to enhance their functionality for industrial applications. The microwave-irradiated starch samples resulted in decrease in moisture, lipid and ash contents of the modified starch samples but an increase in the protein content. The apparent amylose (AAM) content of the modified control starches increased and that of the treated starch blends (SBs) decreased upon microwave (MW) radiation. For the MW-irradiated SBs, the values of bulk density, dispersibility, water absorption capacity and pH were in the range 0.75-0.83g/mL, 82.0-86.0%, 75.00- 91.38% and 6.7-7.2, respectively. MW modification increased the swelling power (SP) of the modified SBs (M50CYS/PPS, M70CYS/30PPS) but decreased the SP of the remaining starch samples. Apart from M100PPS, MW irradiation resulted in increase in water solubility index of the remaining modified starch samples (starch blends and 100CYS). The MW-irradiated control starches decreased for peak, trough, final and setback viscosities. In contrast, these pasting viscosity parameters increased when SBs were MW-modified. With the exception of the 50CYS/50PPS blend, MW radiation lowered the breakdown viscosity of modified control starches and starch blends, whereas the pasting temperatures of the studied starches increased. Keywords: Cocoyam starch, pigeon pea starch, physicochemical properties, microwave modification, starch blends