ANTI-NUTRITIONAL CONSTITUENT OF COLOCASIA ESCULENTA ...

sugars were estimated from standard graphs, prepared using potato starch (starch) and glucose
(soluble sugar).
B.A.l.S Protein determination (Kjeldahl method ofnitrogen determination)
B.A.l.S.l Digestion
I g of the dried and ground sample was transferred into a digestion flask. One Kjeldahl
tablet and IQ ml of concentrated H2S04 were added to each flask. The blank was prepared
using the tablet and concentrated H2S04. The mixture was cautiously heated on the
digestion stand in a fume cupboard until the acid became clear. When the digestion was
completed, samples were removed to cool, 2 ml of distilled water was added and the
samples were cooled again.
B.A.l.S.2 Distillation
B.A.l.S.3 Titration
5 ml ofthe sample and 20 ml ofNaOH solution were added to the digestion flask. A conical
flask was prepared by adding 10 ml of saturated boric acid and 6 drops ofmixed indicator
(0.0172 g bromocresol green and 0.0078 g methyl red) so that the condenser tip was
immersed. Distillation was completed and 30 ml ofthe distillate was collected in the conical
flask. The tip ofthe condenser was removed from the conical flask.
The distillate was titrated with 0.05 M Hel to a pink endpoint. The crude protein content of
the Amadumbe tubers was calculated from the results, using a factor of 6.25 to convert the
amount ofnitrogen to crude protein.
B.A.l.SA Fatty acid determination
lA.l.5.4.l Lipid extraction [Bligh and Dyer (1959»)
50 g of Amadumbe were extracted with ISO ml of methanol-chloroform (2:1, v/v) mixture
overnight in the oven shaker. The homogenate was filtered and the filter residue was re­
extracted overnight with a mixture ofmethanol-chloroform (2: I, v/v) and 40 ml of distilled
244