ANTI-NUTRITIONAL CONSTITUENT OF COLOCASIA ESCULENTA ...

The crude fat analysis ofZululand Colocasia esculenta species is shown in Table A3.lb.
Crude fat content ranged from 0.73 to 1.54 per cent in the unprocessed tubers. The total
fat content for the Amadumbe tubers is within the range ofvalues that have been reported
for cocoyam (Sefa-Dedeh and Agyir-Sackey, 2004). The proximate composition for fat
was also found to be similar to or higher than that ofpotato and sweet potato (Noman et
al., 2007). These values are relatively higher than otherroot and tuber crops (Aghor-Eghe
and Rickard, 1990; Rickard and Coursey, 1981). As was expected, the fried tubers had a
higher level offat (10.58 per cent to 15.05 per cent) than the raw tubers or those cooked
using another method in this investigation.
The main functions ofproteins are growth and replacement of lost tissues in the animal
body. The variations in the mean values of the protein content of the different varieties
were distinct Environmental factors such as duration of growing season, length of day,
rainfull, light intensity and temperature, as well as agronomic factors such as plant
density, wild plants or soil fertility, can influence protein content (Robertson et al., 1962;
Singh et aI., 1972; McLean et al., 1974). All the tubers had a protein content ofless than
six per cent, as is generally the case with most starchy root crops. Similar low protein
levels have been reported for other cocoyam and taro varieties (Onayemi and Nwigwe,
1987; Aghor-Egbe and Rickard, 1990; Sefa-Dedeh and Agyir-Sackey, 2004). Amadumbe
is normally consumed with other vegetables, a practice that undoubtedly complements
the poor protein content ofthe tuber.
For each Amdumbe variety, processing methods showed no apparent or consistent effect
on the moisture, ash and protein contents. Fat content only increased drastically with
frying. The differences in processing may therefore be due to various differences in other
components (Moakwa and Sefa-Dedeh, 2001). Variations in the nutritional composition
ofroots and tubers from different places have been attrIbuted to variations in the genetic
background, as well as to varying climatic, seasonal and the agronomic factors
(Onwueme,1982).
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