Calcium oxalate and physico-chemical properties of cocoyam (Colocasia esculenta and Xanthosoma sagittifolium) tuber flours as affected by processing

Calcium oxalate and some physico-chemical properties of flours from three cultivars of Colocasia spp. (coco-india, ede-ofe and inimbu) and one Xanthosoma sp. (ede-uhie) — steeped (30 °C), boiled (90 °C) and roasted (165 °C) — were compared with those of untreated flours. Results showed that boiling effected the highest oxalate reduction, especially in inimbu. The highest rate of change of oxalate reduction was also observed in inimbu for up to 30 min of boiling. Edeofe superceded it afterwards, even up to the 60th minute of processing. Gelatinization temperature decreased, and water and oil absorption capacities increased markedly due to the three processes. Boiling and roasting effected reduction in cold-paste viscosity, while an inconsistent trend resulted from steeping. Statistical analysis using an analysis of variance (ANOVA) technique (P < 0.01) showed that the effects of cultivar and process time were significant on the calcium oxalate due to steeping and boiling. Process time variation in steeping and boiling of inimbu on both water and oil absorption was significant. On the other hand, only the effect of cultivar on viscosity of both steeped and boiled samples was significant.