PHYSICOCHEMICAL AND FUNCTIONAL PROPERTIES OF INDIVIDUAL AND BLENDED MICROWAVED STARCHES FROM TANNIA COCOYAM (XANTHOSOMA SAGITTOFOLIUM) AND PIGEON PEA (CAJANUS CAJAN)

Abstract

Modification of starch is necessary in order to engender a range of functionality. Tannia cocoyam and pigeon pea individual starches and their blends were irradiated in a microwave oven with a view to modifying their structures. The physicochemical, functional, pasting and morphological properties of the treated, un-treated (raw) starches and their blends were evaluated and compared. The amylose content for the treated starch samples ranged from 25.08 to 33.94 %, relative to the untreated starch samples 24.83 to 33.68 %, decreases in moisture content, ash content, and fat content were also observed following microwave treatment.Microwave irradiation also resulted in significant increases in dispersibility, water absorption capacity, solubility but reductions were recorded for bulk density, pH and swelling power with few exceptions. Rapid Visco Analyser studies showed that the irradiation caused significant reductions in pasting viscosity (except for M70CYS/30PPS and M50CYS/50PPS blends) and breakdown viscosity (except M50CYS/50PPS blend), whereas the pasting temperature increased for all the treated starches. From the Scanning Electron Micrographs, the microwaved starch granules appeared swollen and showed more aggregation than the raw starch granules. Possible industrial applications of the individual starches, microwave-treated starches and their blends are clearly suggested.