Thermal Treatment Effects on the Calcium Oxalate and Mineral Contents of Xanthosoma Atrovirens (ede ocha): a Cocoyam Species

Abstract

The extent to which the irritant in cocoyam can be destroyed and removed during thermal treatment and the resultant effect of the treatment on the mineral content and influence of tuber thickness are investigated in this study. Wholesome tubers of cocoyam (Xanthosoma atrovirens) were selected and subsequently cleaned, peeled, washed and size reduced into various dimensions (1cm, 3cm and 5cm thickness). The various dimensions were subjected to boiling and samples were withdrawn at intervals of 0, 30, 60, 90 and 120 min. The boiled samples were further sliced into smaller sizes; dried in an air- oven at a temperature of 55°C to a constant weight, milled into flour and packed in polythene material and stored in dry condition. The design of the study fitted into 3 (dimension) x 5 (boiling duration) factors. The flours generated were subjected to calcium oxalate and mineral loss or gain analyses. Significant reduction in calcium oxalate occurred at p< 0.05 as the boiling time interval increased. The highest removal of calcium oxalate occurred for the 1.0 cm thickness in which the acrid taste was found to disappear after boiling for 60 min. However the oxalate in the 3.0 cm and 5.0cm thickness were found to disappear after boiling for 120 min. Similarly, mineral losses were significant at intervals of boiling time used for the study. The 1.0 cm thickness showed the highest loss of potassium from the initial value of 1099.27mg/100g flour at 0.0 min to 586.77mg/100g after 120 min. The 3.0 cm, with the initial potassium value 1100.30 mg/100g was reduced to a value of 598.20 mg/100g after 120 min boiling, while the 5.0 cm thickness had potassium value reduced to 607.97 mg/100g at 120 min boiling from the initial potassium value of and 1101.77mg/100g. Also, reductions in minerals were observed for magnesium, phosphorus and calcium. Tuber thickness and boiling duration are the controlling factors in calcium oxalate and mineral loss. It might be recommended that cocoyam be cut to size thickness of 1.0cm since it gave reduced time of cooking of 60 min which resulted to the disappearance of calcium oxalate in the cooked material and energy saving..

Keywords: Xanthosoma Atrovirens; tuber thickness; boiling time; calcium oxalate; mineral loss.