ANTI-NUTRITIONAL CONSTITUENT OF COLOCASIA ESCULENTA ...

determine fatty acid composition. Petroleum ether extracts only non-polar lipids, while
methanol-chloroform extracts both non-polar and polar lipids.
Iodine values are used to measure the relative degree ofuusaturation in fats. This value
calculated from fatty acid composition may give a value closely related to the number of
double bonds present in the fat.
The standard for oleic acid was used to determine fatty acid composition ofAmadumbe
by comparing the molecular weights given by each peak to relative retention times. The
results showed that the investigated Amadumbe extract contained oleic acid, linolenic
and linoleic acid, with linoleic acid being the most abundant. This is in agreement with
studies undertaken by Hussain et al. (1984), who determined that palmitic, oleic and
linoleic acids were the main fatty acids in Colocasia esculenta (L.) Schott, with linoleic
acid predominating.
A.4.4 Anti-nutritional factors
The nutritional value ofany food product depends largely on the availability and qnality
of the nutrients as well as the presence of anti-nutritional factors. Anti-nutrients are
known to reduce the availability ofnutrients to animals and humans (Rackis et a11986;
Gupta, 1987). The higher the concentration of the metabolites, the greater the risk they
pose to the health of the consumer. During domestic processing, anti-nutrients are partly
removed and their toxicity is lowered. Nevertheless, consuming large quantities of food
with anti-nutrients may still result in a health risk. The screening of the two varieties of
Amadumbe tubers from the three geographical areas revealed no specific pattern in the
anti-nutrient levels. It was therefore decided to process only the two varieties from the
local Esikhawini areas because of ease of collection. This screening was conducted to
determine the efficiency of the local processing methods (boiling, frying and roasting)
employed in detoxifying the anti-nutrients present in the raw materials.
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