Physicochemical and Pasting Properties of Starch Extracted from Four Yam Varieties

Abstract

Yams are not among the most common sources of industrial starch, which are mostly imported at a cost. Exploiting alternative sources of starch would lessen the burden of its importation. Starches from four local varieties of Dioscorea rotundata namely Pona, Labreko, Asobayere and Muchumudu were analyzed for their physicochemical and functional properties. Results obtained showed significant differences (p<0.05) in some physicochemical properties (moisture, ash, starch yield and pH). Moisture, ash, starch yield, pH, amylose, amylopectin, swelling power, solubility and water binding capacities ranged from 7.22 to 7.82%, 024 to 0.86%, 12.61 to 20.89%, 5.57 to 6.25, 27.48 to 31.55%, 68.45 to 72.52%, 10.57 to 12.48%, 8.52 to 9.32% and 175.25 to 182.69% respectively. Asobayere had the highest starch yield (20.89%) and may be exploited for starch production. There were significant differences (p<0.05) in the pasting properties. The pasting temperature ranged from 75.10 (Asobayere) to 77.30°C (Muchumudu). Peak temperature ranged from 81.7 (Asobayere) to 94.8°C (Muchumudu). Peak viscosity for Asobayere, Pona, Labreko and Muchumudu were 726, 614, 685 and 639 BU respectively. Final viscosity ranged from 385 (Pona) to 817 BU (Muchumudu). Values of 385 (Asobayere), 142 (Labreko), 293 (Pona) and 25 BU (Muchumudu) were observed for breakdown viscosity. Labreko had the highest value of 337 BU and Pona the lowest value of 79 BU for setback viscosity. Muchumudu may be used industrially in products that require high unit yield, low viscosity and paste stability at low temperatures. Asobayere and Labreko may be used for foods that require thick and cohesive paste such as fufu and pounded yam due to its high pasting viscosities. Yam starches can be exploited for diverse uses.