Effect Of Cooking On The Profile Of Phenolics, Tannins, Phytate, Amino Acid, Fatty Acid And Mineral Nutrients Of Whole-Grain And Decorticated Vegetable Cowpea (Vigna Unguiculata L. Walp)

An experiment was conducted to determine the profile of phenolics,
tannins, phytate, amino acid, fatty acid and mineral nutrients in whole-grain
and decorticated vegetable cowpea before and after cooking. Two cowpea
varieties: C-152-White, having big grain and S-1552-White, having small grain
with black eye were used for the study. Decortication of cowpea grain resulted
in significant reduction (P � 0.05) of total phenolics, total tannins and phytate
contents of the two cowpea varieties. Comparison showed that cooking resulted
in 19, 28, 28 and 37% losses in phenolics in whole-grain C-152, decorticated
C-152, whole-grain S-1552 and decorticated S-1552, respectively. After
cooking, whole-grain and decorticated C-152 retained 52.1 and 57.7% tannins
while S-1552 retained 59.4 and 49.5%, respectively. In the whole grain, C-152
lost 72.2% phytate after cooking while S-1552 lost 70.3%. For the decorticated
samples, C-152 lost 72.4% phytate after cooking while S-1552 lost 71.2%. For
the two cowpea varieties, decortication resulted in significant (P � 0.05) losses
of Ca, Fe, Mn, Mg, Zn, K and Cu while there was no significant effect on protein
and amino acid profile. Cooking did not cause any significant change in the
mineral nutrient composition of either the whole-grain or decorticated cowpea.
For the two cowpea varieties, bulk of the fat consisted of palmitic acid
(23.2–27.3%) and stearic acid (53.5–59.8%) in the ratio of 1:2, approximately.
Upon cooking, losses of crude protein were recorded in the whole-grain and
decorticated samples of the two cowpea varieties.