Physicochemical Properties and Pasting Behaviours of Selected Tropical Tubers

Abstract

Proximate compositions, physicochemical properties and minerals of starches extracted from the corms and cormels of white cocoyam (Colocasia esculenta), corms of red cocoyam (Colocasia esculenta) and bitter yam (Dioscorea dumetorum) were determined using standard methods. The ranges of proximate compositions (%) in terms of crude protein, ash, fat, crude fibre, carbohydrates by difference and moisture contents were 1.17±0.01-2.09±0.01, 1.72±0.02-1.88±0.02, 0.33±0.01-0.52±0.01, 0.46±0.01-0.69±0.02, 85.61±0.05-86.03±0.19 and 9.36±0.02-10.10±0.10 respectively. The studies showed that the increasing order of bulk densities of the samples was red cocoyam corms<white cocoyam corms<white cocoyam cormels=bitter yam. Starches of the corms of both cultivars exhibited higher values of water absorption capacity than the starch of white cocoyam cormels. The highest value of least gelation concentration, 15.00±0.02% was significantly similar (p<0.05) for the starches of white cocoyam cormels and bitter yam. The values of amylose (%), swelling power (g/g) and solubility (%) ranged between 16.50±0.01 and 25.15±0.01, 8.03±0.01-11.21±0.01 and 7.35±0.01-8.44±0.01 respectively. Bitter yam starch was most viscous (329.50 RVU) with peak stability (181.83 RVU) at 61.950C in 5.18 mins.