Chemical composition of processed tender leaves and husks of cowpea and organoleptic attributes of their soups

Thesis Abstract

The study examined the chemical composition of fresh, sundried tender leaves and husks of cowpea
‘Adengee’ (Vigna unguiculata) and organoleptic attributes of their traditional soups. Information on
processing, preparation and utilization of soup meals based on cowpea leaves and husks were obtained
during the focus group discussion. The tender leaves and husks were parboiled and sundried.
Proximate, micronutrients, phytochemicals and antinutrient levels were determined using standard
procedures. The soups based on fresh and sundried leaves and husks were analysed prior to sensory
evaluation. The data collected were statistically analysed using means, standard deviation and standard
error. All values were based on residual moisture. Protein for dried leaves was higher (p<0.05) (39.24
vs. 21.98 and 13.95%) than those of fresh leaves and dried husks. Dried leaves and husks had lower fat
than the control (1.31 and 0.75 vs. 9.10%) (p<0.05). Sun drying increased ash in both dried leaves and
husks (14.74 and 10.86 vs. 4.82%). The lower value for fibre in the dry samples was rather surprising
(14.20 and 20.42 vs.25.13%) (p<0.05). Carbohydrate significantly increased more in dried husks than
in dried leaves. (53.76 Vs. 30.22%) (p<0.05).The micronutrients in both dried leaves and husks were
reduced due to their volatile nature. Tannins, saponins, flavonoids and polyphenols decreased
significantly (p<0.05) in processed samples due to drying. Soups based on dried leaves (DS) had
higher protein (p<0.05) relative to the soup based on dried husks (HS) and fresh leaves (FS) (34.40
vs.34.10 and 33.30%).

Similarly, husks based soups had higher fat (34.10 vs.34.05 and
31.44%)(p<0.05) Ash was higher in dried leaves based soup(7.83%) and fresh leaves soup (7.20%).
Fibre for the husks based soup was higher (p<0.05) relative to fresh and dried leaves based soups
(6.13 vs.5.58 and 6.11%, respectively). The carbohydrate levels were generally appreciable. All soups
had appreciable levels of calcium, phosphorus and iron. These minerals varied significantly amongst
the soups (p<0.05). Zinc and iodine also differed (p<0.05).β-carotene content of soup based on fresh
leaves was higher (p<0.05) relative to those based on dried leaves and husks (6.08 vs.5.07 and
5.46RE).Vitamin C varied significantly (0.90 to 1.10mg) in soups based on fresh leaves and dried
husks. Tannins, saponins, polyphenols and flavonoids in soups based on fresh leaves and dried husks
were comparable. Anti nutrients levels in all soups were generally low. Scores for all organoleptic
attributes of the three soups were more than half (6.17 to 7.70) of the 9-point scale. The soups were
generally acceptable. As judged by the results, cowpea leaves, husks and their soups have high
nutrient potentials to justify its cultivation, consumption promotion and diversification. Consumption
related information such as nutritional properties should be packaged and extensively promoted to
broaden the knowledge of health and nutritional benefits of consuming cowpea leaves and husks. The
results demonstrate that, there is a potential in developing multi-purpose varieties with good
performance, which are well-yielding in both leaves and seeds. Therefore, production related
information, such as variety, yields and cultivation practices as well as processing should be packaged
and made available to extension personnel and governmental agricultural research institutes that often
have a good outreach to farmers.