According to Braide and Nwaoguikpe (2011), cocoyams are herbaceous perennial plants belonging to the family Araceae and are grown primarily for their edible roots, although all parts of the plant are edible. Cocoyam that are cultivated as food crops belong to either the genus colocasia or the genus xanthosoma and are generally composed of a large spherical corn (swollen underground storage stem), from which a few large leaves emerge.
Cocoyam can be classified into Colocasia species and xanthosoma species Colocasia species may also be referred to as taro, old cocoyam, arrowroot, eddoes, macabo or dasheen; it originated from south east or central Asia. Xanthosoma species may be referred to as tannia, yautia, new cocoyam or Chinese taro, it originated from central and South America.
Cocoyam possesses high nutritional values when compared with others like cassava and yam with substantial vitamin, mineral and proteinous contents. As a relatively well known staple crop in underdeveloped and developing countries, it can serve as a weaning food and its own leaves are sometime used as vegetable for cooking.
According to Braide and Nwaguikpe (2011), cocoyam is originally from the tropical and sub-tropical countries and studies reveal that it is among the least studied root plants. It is mostly cultivated in countries like Nigeria, Asia, Pacific, Island, Ghana and Japan due to its high importance. It produces two edible parts namely; the corms (tuber) and the leaves. Cocoyam is a great source of dietary fiber and starch that can generate energy to the body.
Surveys report that cocoyam production has tremendously increased from 1990s till present and this number is expected to increase more. Highest proportion of cocoyam production is recorded in Africa, then Asia, while the least proportion is from the Caribbean. Cocoyam is usually available throughout the year with other similar staple root crops such as yam, potato and cassava. Cocoyam are characterized by corms, stems, and leaves, however, they are differentiated in leaf attachment as some species have their leaves emerging near the centre while others have their stalks attached.
Origin and distribution
Various lines of ethno-botanical evidence suggest that cocoyam originated in south central Asia, probably in India or the Malay Peninsula. Wild forms occur in various parts of South Eastern Asia (purse glove 1972). From its centre of origins cocoyam spread Eastward to the rest of South East Asia and to China, Japan and the Pacific, Island. From Asia, cocoyam spread eastward to Arabic and the Mediterranean region. By 100 B.C, it was being grown in China and in Egypt.
It arrived on the East coast of Africa are 2,000 years ago, it was taken by voyagers, first across the continent to west Africa and latter on slave ship to the Caribbean. Today, cocoyam is pan-tropical in its distribution and cultivation. The greatest intensity of its cultivation and its highest percentage contribution to the diet occurs in the pacific Island. However, the largest area of cultivation is in West Africa, which therefore accounts for the greatest quantity of production. Significant quantities of cocoyam are also grown in the Caribbean and virtually all humid or sub-humid parts of Asia. It has been suggested that the edible type of cocoyam was developed and selected from cultivated cocoyam in china and Japan several centuries ago and it was later introduced to the West Indies and other parts of the world (purse glove 1972).
Morphology and anatomy
According to Enwelu, Asogwa, Nnaligi and Ezeano (2014), cocoyam is an herbaceous plant which grows to a height 1-2m. the plant consists of a central corm (lying) just below the soil surface) from which leaves grow upwards roots grown downwards, while corbels daughter corms and runners (stolons) grow laterally. The root system is fibrous and lies mainly in the top one meter of soil.
In the dasheen types of cocoyam, the corm is cylindrical and large. It is up to 30cm long and 15cm in diameter and constitutes the main edible part of the plant. In eddoes types, the corm is small, globoid and surrounded by several comely. The cormels and the daughter corms usually give rise to subsidiary shoots even while the main plant is still growing, but cormels tends to remain dormant and will only give rise to new shoots if left in the ground after the death of the main plant. Each cormel or each daughter corm has a terminal bud at its tip, and auxiliary buds in the axils of the numerous scale leaves all over its body.
Corms, cormels and daughter corms are quite similar in their internal structure. The outmost layer is a thick brownish perineum within this lays the starch filled ground parenchyma. Vascular bundles and latecomers ramify throughout the ground parenchyma. The density and woodiness of the corm increase with age.
Varieties of cocoyam
Richard (2011) stated that there are two varieties of cocoyam, namely, xanthosoma species and the coccasia species
- Xanthosoma species: xanthosoma species is one of the two types of cocoyam. The name is derived form the Greek words “xanthos” meaning “yellow”, and “soma” meaning “body”. This refers to the stigma or yellow inner tissues of this species of cocoyam: it is grown for its starchy corns, an important food staple of tropical region. It is popularly referred to as elephant ear (from, the purported resemblance of the leaf to an elephant’s ear). The leaves of most xanthosoma species are 40 – 200cm long, arrowhead – shaped or subdivided into three or as many as 18 segments (Akpan & Umoh, 2012).
- Colocasia species: colocasia species of cocoyam are herbaceous perennial plants with a large corm on or just below the ground surface. The leaves are large to very large, 20-150cm (7.9 – 59.1 in) long, with a arrow headed shape, dark green above and light green beneath, triangular – ovate, sub-rounded and mucronat at apex, tip of the basal lobes rounded (Carpenter & Steinke, 2010).
Common pest associated with cocoyam
Like any other crops and plants, cocoyam is susceptible to pesticides attacks and the common pest includes slugs that attack the corn thereby providing entry points for micro-organisms attack. Moreover, the pesticides attacks can cause the corns to start delaying two weeks after harvest. Cocoyam can also suffer from post harvest losses due to mechanical damage as well as microbial attacks on the corns during storage.
Insecticidal and microbial attacks of cocoyam can be prevented by the use of bactericides, insecticides, disease free planting materials, fungicides and proper cultivation methods.
Cultivation seasons and location
Braide and Nwagwikpe (2011), cocoyam is mostly cultivated in countries like Nigeria, Asia, Pacific island, Ghana and Japan. The highest proportion of cocoyam is recorded in Africa. Cocoyam is usually available throughout the year with other similar staple root crops such as yam, potato and cassava.
Uses of cocoyam
- The corms, which have a light purple colour due to phenolic pigments, are roasted, baked or boiled and the natural sugars give a sweet nutty flavor
- The starch is easily digestible and since the grains are fine and small, it is often used for baby food.
- Young cocoyam leaves and stems can be eaten after boiling twice to remove the acrid flavor and the leaves are a good source of vitamins A and C and contain more protein than the corms.
- Cocoyams cans also be processed into various food products used for industrial and culinary purposes.
- Africans usually blend cocoyam and use it as a thickener for baking and cooking soup such as oha soup and bitter leaf soup e.t.c
- It can also be cooked as porridge and the leaves can be use for cooking soups.
- Inspect the corm thoroughly to make sure the corms are firm and that you are satisfied wholesomely.
- It is a right claim the softness of the corns whether in part or whole is a clear sign that the cocoyam is damaged.
- Press the corn right round to ensure the firmness is unquestionable.
- Ensure that you buy cocoyam that is devoid of cracks and physical wounds as much as you can.
Nutritional value per 100g
Cocoyam cooked without salt
Energy 594kg (142kcal)
Dietary fiber 5.1g
Thiamine (B1) 0.107mg (9%)
Riboflavin (B2) 0.028mg (2%)
Niacin (B3) 0.51mg (3%)
Pantothenic acid (B5) 0.336mg (7%)
Vitamin B6 0.331mg (25%)
Folate (B9) 19mg (5%)
Vitamin C 5mg (6%)
Vitamin E 2.93mg (20%)
Calcium 18mg (2%)
Iron 0.72mg (6%)
Magnesium 30mg (8%)
Manganese 0.449mg (21%)
(Source: USDA National Nutrient Database, 2014)
Phosphorus 76mg (11%)
Potassium 484mg (10%)
Zinc 0.27mg (3%)
Cocoyam leaves, raw
Nutritional value per 100g
Energy 177kg (42kcal)
Dietary fiber 3.7g
Vitamin A Equiv. 241mg (30%)
Beta-carotene 2895mg (27%)
Lutein zeaxanthin 1932mg
Thiamine (B1) 0.209mg (18%)
Riboflavin (B2) 0.456mg (38%)
Niacin (B3) 1.513mg (10%)
Vitamin B6 0.146mg (11%)
Folate (B9) 126mg (32%)
Vitamin C 52mg (63%)
Vitamin E 2.02mg (13%)
Vitamin K 108.6mg (103%)
Calcium 107mg (11%)
Iron 2.25mg (17%)
Magnesium 45mg (13%)
Manganese 0.714mg (34%)
Phosphorus 60mg (9%)
Potassium 648mg (14%)
Zinc 0.41mg (4%)
(Source: USDA National Nutrient Database, 2014)
Health benefits of cocoyam
The health benefit of cocoyam includes:
- Its ability to improve digestion
- It lowers blood sugar level
- It prevents certain types of cancer
- Protect the skin
- Boost vision health
- Increase circulation
- Decrease blood pressure
- Aid immune system
- Prevents heart diseases
- Supports muscle and nerve health
Ability to improve digestion
One of the most important functions of cocoyam root in the diet is its role in digestion. The high level of dietary fiber found in cocoyam (a single serving contains 27% of the daily requirement of dietary fiber) makes it very important for supporting our gastrointestinal health. Fiber helps to add bulk to our bowel movement, thereby helping food move through the digestive tract and facilitating improved digestion.
Cocoyam roots also play an important part for the anti-oxidant activity in our body. The high levels of vitamin A, Vitamin C and various other phenolic anti-oxidants found in cocoyam root boost our immune system and help eliminate dangerous free radical from our system. Free radicals are the dangerous by products of cellular metabolism that can cause health cells to mutate and turn into cancerous cells. Cryptoxanthin is a substance found in cocoyam root, it boost our immune system and help eliminate dangerous free radicals from our system. Cryptoxanthin is directly connected to a lower chance of developing both lung and oral cancer.
Lowers blood sugar levels
Dietary fiber can also help lower the chances of developing diabetes because it regulates the release of insulin and glucose in the body.
Blood pressure and heart
Cocoyam root contains a significant level of potassium, which is another of the essential minerals that we need to remain healthy and functional. Potassium helps to relieve stress and pressure on blood vessels and arteries by relaxing the veins and blood vessels.
As mentioned above, cocoyam root contains various antioxidants, including beta – carotene and cryptoxanthin. These antioxidants can help to improve vision as well, by preventing the free radical from ocular cells and causing macular degeneration or cataracts.
Between vitamin E and A, our skin is well protected when we add cocoyam root to our diets. Both of these essential vitamins work to eliminate skin conditions and boost overall cellular health meaning that our wounds and blemish heal faster. Cocoyam root is nature’s little secret for healthier skin.
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