Physicochemical Properties of Native and Heat Moisture Treated Starches of White and Red Cocoyam (Colocasia esculenta) Varieties

Abstract

White and red cocoyam starches were physically modified by heat moisture treatment at 16, 24 and 32 % moisture levels. The functional and pasting properties of the modified and native starches were evaluated using standard methods. The swelling power at 60oC, water absorption capacity, oil absorption capacity, least gelation concentration, packed bulk density and loose bulk density of heat moisture treated white and red cocoyam starches ranged between 1.90 - 2.18 and 1.89 – 2.21; 1.00 – 1.80 ml/g and 0.80 – 1.60 ml/g; 1.40 – 1.80 ml/g and 1.20 – 1.40 ml/g; 8.00 – 10.00% and 8.00 – 10.00%; 0.51 – 0.62 g/ml and 0.54 – 0.64 g/ml; 0.41 – 0.51 g/ml and 0.43 – 0.53 g/ml respectively. For both white and red cocoyam starches, heat moisture treated starches at 16% moisture content level had the highest swelling power in the temperature range 60oC to 90oC; also starches treated at 32% moisture level had the highest water absorption capacity, oil absorption capacity, packed bulk density and loose bulk density. Red cocoyam native starch had higher peak, trough, breakdown, final and setback viscosity than white cocoyam starch. Heat moisture treatment generally increased the pasting properties of white cocoyam starch. The modification of red cocoyam starch at moisture levels of 16% and 24% reduced the pasting properties, however at higher moisture level, the pasting properties increased. These results suggest that moisture level of cocoyam starches influence their physicochemical properties during heat moisture modification; this will increase the array of food products in which the starches can be used.