STUDIES ON PHYTATES, POLYPHENOLS AND OTHER ANTINUTRITIONAL FACTORS IN COWPEA (Vigna^ unguiculata (L.) Walp.)
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Date
1988
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MPKV, UNIVERSITY LIBRARY RAHURI
Abstract
The present investigations were undertaken to study
the distribution of proximate principles, polyphenols,
phytate phosphorous and trypsin inhibitors in different
parts of cowpea seeds and, to study the effects of processing
practices viz., dehulling, soaking, cooking and
germination on the nutritional quality of cowpea.
The seeds of three cultivars varying in seed size
and colour were used for the study. The colour of the
seeds was white in the case of Local (NI-434). It was red
with white spots in the case of Pusa Nylon and red in the
case of T-3 variety. The seed index ranged from 8.0 to
12.2gper 100 seeds. The protein content of whole seeds
ranged from 26.3 to 28.5 % while crude fat, ash and
carbohydrate contents were in the range of 1.94 to 2.12 %,
3.88 to 4.26 % and 65.4 to 67.5 %, respectively. The polyphenols
content was found to be maximum (0.88 %) in red
coloured seeds (T-3) and minimum (0.54 %) in white seeded
cultivar (Local). Most of the phytate-phosphorus (91.9 to
92.5 %) and trypsin inhibitor activity (93.6 to 95.1 %)
were contributed by cotyledons while seed coat contained
most of the seed polyphenol (68.5 to 7Jf.© %).
Dehulling of cowpea seeds caused a significant
increase in the levels of proteins, crude fat, phytate-P
and trypsin inhibitor activity and significant reduction
in carbohydrates, minerals and polyphenols. Cooking of
cowpea seeds resulted a decrease in proteins, minerals,
carbohydrates, polyphenols, phytate-P and trypsin inhibitor
activity. There was a decrease in carbohydrates, minerals,
polyphenols and trypsin inhibitors and increase in crude
fat and phytate-P" content of cowpea seeds as result of
dehulling followed by cooking. Soaking of cowpea seeds
caused decrease in carbohydrate, minerals, polyphenols,
phytate-P and trypsin inhibitor activity. Germination of
cowpea seeds upto 72 hrs. caused a gradual increase in
proteins and crude fat and a decrease in carbohydrates,
minerals, polyphenols, phytate-P and trypsin inhibitor
activity.
Both tannic acid and purified polyphenols of cowpea
formed complexes with cowpea proteins and bovine serum
albumin. However, the concentration of cowpea polyphenols
required to demonstrate the formation of such complexes
was relatively higher than pure tannic acid. The results
indicated that polyphenols in cowpea seeds at low concentration
might not be harmful for protein utilization.
Further investigations on the effect of processing
and utilization of cowpeas in ready-to-serve extruded,
fermented and bakery products, weaning foods, etc., would
help in reducing the antinutritional factors and improving
the nutritional functionality of cowpea proteins. This
would in turn help to improve the utilization of cowpea as
human food.
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