Proximate Composition of Cocoyam Varieties (Red and White Cocoyam) Collected From Owo, Local Government
Aims and Objectives of the Study
This research study aims to determine the nutritional/proximate composition of two varieties of cocoyam; Xanthosoma sagittifolium (Red cocoyam) and Xanthosomaatrovirens (White cocoyam) grown in Owo, Ondo State.
Origin and History of Cocoyam
Xanthosoma spp. originate from tropical America (Crop Trust, 2010); most probably, Central and South America (Ramanatha et al., 2010), where the species are believed to have been domesticated from the wild (Bermejo and León, 2004). Xanthosoma spp. are listed as invasive in many areas of the world (French Polynesia, Florida, the Galápagos Islands, Puerto Rico, and Costa Rica) in addition to being intentionally introduced to several other regions including Africa and Asia (Crop Trust 2010). It is a more recent introduction to Ghana and West Africa compared with the other prominent genus, Colocassia, which is speculated as being native to the sub-region (Doku, 2006), since there is no known period of introduction of the crop. Xanthosoma is therefore referred to as “new cocoyam” in West Africa. Brown (2000) traced its introduction to West Africa as far as the 16th and 17th centuries, but Wright (2000) reported its introduction to Ghana in 1843 (19th century) by the West Indian Missionaries: There is paucity of information on the species in the region between the 17th and 19th centuries.
Taxonomy and Nomenclature of Cocoyam
Cocoyam, in most literature, is a collective name for species of the two most cultivated genera, Colocasia and Xanthosoma, of the edible aroids from the family Araceae (Opara, 2003; Ramanatha et al., 2010). Both genera have diverse species and a wide geographical distribution, spanning the tropical and subtropical regions of Oceania, Asia, and Africa. Thus, each has several local, traditional, and scientific names (CABI 2013). This, coupled with the morphological similarities between species in genera, has contributed to the confusion in the use of terminologies for their identification (CABI, 2013; Vaneker and Slaats, 2013).
Colocasia has 11 – 16 identified species (CABI 2013; Long and Liu, 2001) with the most common, Colocasia esculenta, being ascribed with two botanical varieties, Colocasia esculenta varesculenta (commonly referred to as dasheen) and Colocasia esculenta varantiquorium (commonly referred to as eddoe). The two are commonly referred to as taro and old cocoyam in most communities of West Africa (Doku, 2006). However, this nomenclature has been challenged in recent years with some botanists referring to the two varieties as different species (CABI 2013; Crop Trust 2010; Opara, 2003; Ramanatha et al., 2010). Thus, there is the need for a taxonomic review of the species to facilitate the dissemination and use of scientific data on the genera.
The genus, Xanthosoma, has been ascribed with 50–60 species (Stevens, 2012), and all cultivated varieties are currently grouped under four species: X. sagittifolium, X. caracu, X. atrovirens, and X. nigrum (X. violaceum) (CABI 2014; FAO 2013). Of these, the two most cultivated and economically important ones are X. sagittifolium and X. nigrum (Vaneker and Slaats, 2013). The foregoing classification is however disputable as some identified species cannot be put under any of the four groups (FAO 2013). This further necessitates the need for a taxonomic review. For simplicity, it is the norm for researchers to refer to all clones of cultivated edible Xanthosoma spp. as X. sagittifolium (FAO 2013), posing a hindrance to accurate dissemination and use of scientific data on the genus.
The original range of the genus is uncertain (CABI 2014). It is however generally agreed to be highly versatile in its requirements for growth and ease of adaptation to new locations making it an optimal choice crop for many climates (CABI 2014; Vaneker and Slaats, 2013), and a potential food security measure for developing economies. The existing confusion on its taxonomy and nomenclature, however, is a major drawback to utilization of available scientific data from different areas of indigene in seeking to tap the full potential of Xanthosoma spp. (Crop Trust 2010; Ramanatha et al., 2010). To date, any meaningful study on its food use must be assessed on the basis of available species in a given location without researchers having the liberty to accurately exploit existing data from other studies as is commonly performed for other root and tuber crops. In spite of Xanthosoma spp. being the main edible aroid in West Africa (Opara, 2003), and Ghana in particular (Acheampong et al., 2015; Ramanatha et al., 2010), there is a dearth of studies on the properties of indigenous cultivated varieties to inform its industrial application and food use (Acheampong et al., 2015; Opara, 2003; Ramanatha et al., 2010).
Not-withstanding the confusion in the taxonomy and nomenclature, Colocasia esculenta (L.) Schott is largely referred to as taro and Xanthosoma sagittifolium (L.) Schott as tannia, and the two are called cocoyam(s) (CABI 2013; Crop Trust 2010; Doku, 2006; Opara, 2003; Ramanatha et al., 2010). In West Africa, Colocasia spp. is called “old cocoyam/yam” and Xanthosoma spp. is called “new cocoyam/yam” because the former is said to be native to the region whereas the latter was introduced (Doku, 2006; Karikari, 2009). For the purposes of this review, the use of the word cocoyam refers to Xanthosoma sagittifolium (L.) Schott.
Existing Knowledge and Uses of Cocoyam
Existing Knowledge on Cocoyam
Cocoyam farmers remain the main custodians of production and varietal information of the crop in West Africa (Acheampong et al., 2015; Ramanatha et al., 2010). Most varieties currently cultivated in the subregion are believed to be landraces introduced by the Portuguese and or West Indian missionaries (Doku, 2006; Onokpise et al., 1999; Ramanatha et al., 2010). Currently, there are two commercially cultivated varieties (Acheampong et al., 2015) from the earlier reported 4–5 landraces in Ghana (Doku, 2006; Karikari, 2009), and three released but not yet commercially cultivated varieties (Acheampong et al., 2015). The landraces are generally distinguished by the color of the peeled cormels resulting in red, white, and yellow varieties with corresponding words in local dialects used for their identification (Doku, 2006; Onokpise et al., 1999).
Locals also differentiate their cooking properties based on their cooked texture and required cooking time to give soft and firm/hard texture, as well as short and long cooking varieties, respectively (Doku, 2006; Karikari, 2009). Available information on Nigerian landraces has advanced a step further in ascertaining the true taxa (Osuji and Nwala, 2015) and some processing properties of indigenous varieties (Falade and Okafor, 2013, 2014; Ojinnaka, Akobundu, and Iwe, 2009) but same is not true for Ghana and other West African countries. The knowledge gap on in- depth processing properties of cultivated varieties is a major drawback to establishing the full potential of Xanthosoma sagittifolium through development of novel food products and other industrial uses.
MATERIALS AND METHODS
Two varieties of Cocoyam X. sagittifolium (Red cocoyam) and X. atrovirens (White cocoyam)used in the research work was purchased from a local market in Owo, Ondo State. The cocoyam was purchased wholesome, that is, it was free from rot and had no physical damage. Equipment, chemicals (reagents) and other facilities used in the research work were obtained from the laboratories of the Department of Food Science and Technology, Rufus Giwa Polytechnic Owo, Ondo State.
Production of Cocoyam Flour
The fresh corms of the red and white cocoyam was collected, washed in running tap to remove sand and stone, peeled, washed again and shredded into thin slices/size or thickness. After which the slices were spread thinly on drying trays and sundried for 2 days. The dried samples were packed from the sun, cooled and stored in a polyethylene bag. After which it was milled using attrition mill. Then the flour was sieved using a 60 mesh sieve. The cocoyam flour was stored in air tight bottles, labeled and kept in a cool dry place for further analysis as shown in figure 1 below.
RESULTS AND DISCUSSION
Table 4.1: Results for Proximate analysis of Red and White Cocoyam
CONCLUSION AND RECOMMENDATIONS
The present study revealed that white cocoyam flour has an appreciable quantity of ash content, crude fiber, protein and carbohydrate content, but the quantity of fat and moisture content is relatively low. However, X. atrovirens (white cocoyam) variety was found to be nutritionally superior to X. sagittifolium (red cocoyam) and other varieties in terms of carbohydrate content, moisture content, ash, content, crude protein and fibre content.
Based on the present revealed results on white cocoyam, it is therefore recommended that white cocoyam consumption should be encouraged both for children and adult as a cheap dietary nutrients source for the promotion of good health. And also, the potential use of white cocoyam should be utilized to the fullest by food industries due to its nutritional qualities.
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