ANTI-NUTRITIONAL CONSTITUENT OF COLOCASIA ESCULENTA ...

A.2.3.3
A.2.3.4
U.3.4.1
iii. Roasting: Amadumbe samples were roasted in a baking pan in an oven
for 30 minutes at 180 0 C.
The processed samples were sun-dried and then milled into a fine powder, which was
stored in bottles until used.
Proximate composition
Protein, moisture, carbohydrate, ash and crude fat contents were determined as descnbed
in AOAC methods (1990). The crude protein content was calculated by converting the
nitrogen content determined by the micro-Kjeldahl method (N x 6.25). The moisture
content was determined by oven-drying at II0 0 C to a constant weight. The total
carbohydrate and starch contents were percolated with ethanol and perchloric acid
respectively and then reacted with anthrone (Hansen and Msller, 1975). Ash content was
determined by incineration of the samples, the weights of which were known, in a
furnace oven. Fat content was determined gravimetrically by extraction, using petroleum
ether on a Soxhlet extraction unit. The dried residue was quantified gravimetrically and
expressed as percentage oflipid.
Fatty acid composition in Amadnmbe
Lipid extraction
Purple and white Amadumbe samples from Esikhawini local market were separately
extracted with a methanol-ehloroform (2:1, v/v) mixture over 24 hours in an oven shaker
at room temperature. This was then filtered under suction and the residue re-extracted
with a methanol-ehloroform-water (2.5:1.3:1, v/v) mixture for another 24 hours. The
filtrates were combined and then separated in the separating funnel into chloroform and
water fractions. The chloroform layer was then mixed with 30 ml of benzene and dried
under vacuum. The residuallipids were weighed and redissolved in a minimal volume of
a methanokhloroform mixture and stored in the fridge (Bligh and Dryer, 1959).
36