Comparative Assessment of the Chemical Composition of Three Varieties of Cowpea Flours
Chapter One
Objectives of the Study
The Objective of the study was to examine the chemical composition of flours from three varieties cowpea seeds.
CHAPTER TWO
LITERATURE REVIEW
History, Origin and Distribution
Cowpea was domesticated in Africa, presumably in the northeastern part of the continent in present day Ethiopia. The progenitor of the modern cultivated V. u. unguiculata is probably the wild annual form, V. unguiculata var. spontanea. In support of the idea that the crop originated in northeastern Africa, Steele (2006) noted that the variability of the wild relative V. unguiculata spp. Dekindtiana which has also been considered as a possible progenitor of cultivated cowpea is greater in that part of Africa than in West Africa. Pasquet and Baudoin (2001) likewise support a Horn of Africa origin based on ethnobotanical, linguistic, as well as phyto-geographical considerations. Still, some scientists have considered West Africa a possible site of origin because of the high variability of V. u. dekindtiana in this region (Faris, 2005).
Lack of archeological records for cowpea cultivation hinders efforts to establish its site of origin unequivocally. Like its New World relative, common bean, cowpea may prove to have two or more sites of origin. The current consensus seems to be that domesticated cowpea originated in the northeastern region of sub-Saharan Africa (Smartt, 2005) and spread westward and southward from there. This Horn of Africa origin is also supported by recent studies using molecular markers (Ba et al., 2004).
Morphological and Phenological Characteristics
Cowpea is an herbaceous warm-season annual that is similar in appearance to common bean except that leaves are generally darker green, shinier, and less pubescent. Cowpeas also are generally more robust in appearance than common beans with better developed root systems and thicker stems and branches. Plant growth habit can be erect, semi-erect, prostrate (trailing), or climbing depending mostly on genotype, although photoperiod and growing conditions can also affect plant stature. Most cowpea accessions have indeterminate stem and branch apicies. Early flowering cowpea genotypes can produce a crop of dry grain in 60 d, while longer season genotypes may require more than 150 d to mature depending on photoperiod. Flowers are borne on racemes on 15- to 40-mm peduncles that arise from the leaf axils. Two or three pods per peduncle are common, and often four or more pods are carried on a single peduncle if growing conditions are very favorable. The presence of these long peduncles is a distinguishing feature of cowpea, and this characteristic also facilitates hand harvesting (Ba et al., 2004).
Cultivated cowpea seed weighs between 8 and 32 mg and ranges from round to kidney shaped. Pods are cylindrical and may be curved or straight, with between 8 and 15 seeds per pod. The seed coat can be either smooth or wrinkled and of various colors including white, cream, green, buff, red, brown, and black. Seed may also be speckled or patterned. Seeds of well-known cowpea types, such as “blackeye pea” and “pinkeye,” are white with a round irregular-shaped black or red pigmented area encircling the hilum, giving the seed the appearance of an eye.
Emergence is epigeal (similar to common bean and lupin), where the cotyledons emerge from the ground during germination. This type of emergence makes cowpea more susceptible to seedling injury, since the plant does not regenerate buds below the cotyledonary node. The open display of flowers in and above the canopy and the presence of extrafloral nectaries contribute to the attraction of insects. Cowpea primarily is self-pollinating, but out crossing rates as high as 5% have been recorded and care needs to be taken to avoid out crossing during the production of breeder and foundation seed, or unacceptable levels of “off-types” will result (Steele and Mehra, 2000).
Cowpea is a short day plant, and many cowpea accessions exhibit photoperiod sensitivity with respect to floral bud initiation and development, while others are day neutral (Ehlers and Hall, 1996; Craufurd et al., 1997). For some genotypes, the degree of sensitivity to photoperiod (extent of delay in flowering) is modified by temperature (Wein and Summerfield, 2000; Ehlers and Hall, 1996). In West Africa, selection for differing degrees of photosensitivity or differences in juvenility has occurred in different climatic zones such that pod ripening coincides with the end of the rainy season in a given locale, regardless of planting date, which is often variable due to the variable onset of wet seasons (Steele and Mehra, 2000).
This attribute allows pods to escape damage from excessive moisture and pathogens. Photoperiod sensitivity, when appropriately deployed in a breeding program, can be valuable to ensure crop maturity after wet seasons or before drought or cold weather limits crop growth. However, it may constrain the direct usefulness of an otherwise desirable cultivar to a small area of adaptation or even to a specific season within this restricted area.
Cultivated cowpeas have been divided into five cultivar groups based mainly on pod and seed characteristics (Pursglove, 2008; Pasquet, 1999). Cultivar group Unguiculata is the largest and includes most medium- and large-seeded African grain and forage-type cowpeas. Cultivar group Melanophthalmus includes “blackeye pea”-type cowpea with large, somewhat elongated seeds with wrinkled seed coats and fragile pods (Pasquet, 1998).
Members of cultivar group Biflora (also known as “catjang”) are common in India and characterized by their relatively small smooth seeds borne in short pods that are held erect until maturity. Cultivar group Textilis is a rather rare form of cowpea with very long peduncles that were used in Africa as a source of fiber. Cultivar group Sesquipedialis (known as “yardlong bean,” “long bean,” “Asparagus bean,” or “snake bean”) is widely grown in Asia for production of its very long (40 to 100 cm) green pods that are used as “snap” beans. Despite the striking differences in morphological characteristics among the cultivar groups, there are no practical barriers to hybridization or recombination between members of the different groups.
CHAPTER THREE
MATERIALS AND METHODS
Materials Source
Three varieties of cowpea (Oloyin, Sokoto and Drum beans) were purchased from the main market in Owo with other ingredients such as pepper, maggi, onions, oil and nylon.
Preparation of Samples
Preparation of Cowpea Flour
The cowpea flour was prepared as described in figure 3.1. Cowpea seeds were manually sorted to remove impurities; it was soaked in water at room temperature (35oC) for 10 mins to soften the testa, which was manually removed and washed off. The cleaned cotyledons were oven dried at 60oC for 24 hours and milled into flour using disc attrition mill, followed by sieving (300-m aperture). All flour samples were kept in high density polythene until needed (Fig. 3.1).
CHAPTER FOUR
RESULTS AND DISCUSSION
Results
Table 4.1: Chemical composition of flours from three varieties of Cowpea
CHAPTER FIVE
CONCLUTION AND RECOMMENDATIONS
Conclusion
Production of flour from three varieties of “oloyin”, “sokoto” and “drum” serves as means of preservative and utilization of the product there by alleviating the post-harvest problem associated with agricultural production. It reduces the preparation and cooking time, reduce low digestibility and anti-nutritional factor in the product. The proximate composition of the flour samples revealed that oloyin bean flour has the highest fat, ash and fibre content, sokoto bean flour have the lowest moisture content indicating longer shelf life of the flour sample, while drum was recorded to have the highest protein content. The energy value of the flour sample was higher in sokoto bean sample, followed by oloyin bean sample, oloyin was recorded to have the highest value of phytic acid.
Recommendations
On the basis of the work done, I will like to recommend that further work should be carried out on the followings
- Study the storage of cowpea and its nutritional effect
- Examine the consumer acceptability of the finished product of “moin moin”.
- Examine the effect of the cereal flour on the finished product.
REFERENCES
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