THE CHEMICAL COMPOSITION AND ORGANOLEPTIC ATTRIBUTES OF LESSER-KNOWN VEGETABLES AS CONSUMED IN NJIKOKA LOCAL GOVERNMENT AREA, ANAMBRA STATE, NIGERIA.

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                                               ABSTRACT

 This study determined the chemical composition and organoleptic attributes of three selected vegetables consumed in Njikoka local government area, Anambra state, Nigeria. The vegetables used for the study were Ipomea batatas, Portulaca olercea and Corchorus tridens purchased from local market in Enugwu-Ukwu, Njikoka local government area, Anambra State, Nigeria. The vegetables were processed (sun and shade dried). The fresh samples served as the controls. Nine yam dishes based on fresh, sun and shade dried of the vegetables were prepared. The vegetable samples and the dishes were analysed for nutrient and antinutrient  contents using modern assay techniques. The results demonstrated that shade and sun drying increased various nutrients. The nutrient values for the dishes were lower than those of the vegetable samples. The sensory evaluations of the dishes were generally accepted by the judges as judged by the results. The nutrient content of these lesser-known vegetables and their dishes are promising. These vegetables and their dishes could upgrade the micronutrient densities of some of our traditional d es based only on popular vegetables that are scarce during dry season.

                                                      CHAPTER ONE

  1.            Introduction

           There are many micronutrient deficiency disease in Njikoka local government area of Anambra state. This is due to low consumption of fruits and vegetables. This was based on the results of   Nigeria food consumption and nutrition survey 2001 – 2003. In Nigeria ecosystem, there are variety of fruits and vegetables both cultivated and wild ones.

           However, their consumption is inadequate mostly among children within the ages of 3 – 5 years. Besides, these well known vegetables, there are many lesser – known fruits and vegetables that might be very good sources of various micronutrients that have been investigated.

            Much interest on nutrient composition, processing and utilization of these lesser- known fruits and vegetables are scarce. In Njikoka local government area of Anambra State, there are many vegetables that are used for preparation of various traditional soups. However, due to poor nutrition education these vegetables are not utilized. These vegetables are mostly consumed by the poor or low income groups in the community.

       According to Tope-Ajayi (2004), proper nutrition provides adequate strength, protection against disease and assist in quick recovery from illnesses. Recent national and local surveys have revealed staggering prevalence of undernourishment among children under 5 years of age. Nearly every child is stunted and one in ten (1:10) is wasted. The common specific  nutritional disorders include protein-energy malnutrition (PEM), anaemia due to iron, vitamin A and iodine deficiencies. Nutrient deficiencies that are most common during childhood and adolescence are iron, calcium, zinc and vitamin A. Adequate amount of these minerals and vitamins must be included in the diet (Lucas, 1996).

          The information on cultivation, preparation, processing and consumption of these vegetables mostly consumed by the poor or low income groups in the society are rare in Njikoka local government area. It is imperative that these vegetables should be investigated for their seasonality, nutrients, antinutrients and food toxicant composition. The thrust of this work was to study the nutritional qualities of Corchorus tridens (Malvaceae), Portulaca oleracea (Portulacaceae, Purslane) and Ipomea batatas (Sweet potatoes) vegetables used in the area to prepare some traditional dishes consumed during festival and non –festival events.

1.2   Statement of the problem

Micronutrient deficiency disorders such as anaemia, goiter, growth retardation and others are common among children under 5 years of age and pregnant women. Insufficient iron intake is the leading cause of iron deficiency anaemia (Neuman, 1991). Young children and their mothers are often called an (at risk) groups because they frequently develop some health problems. These could be prevented if the parents knew and understood the causes of diseases and ways to avoid it. This will be achieved through nutrition education by nutritionists, dieticians, “home-economists”as well as health practitioners and others (Jelliffe, 1991). Copper is a constituent of a number of enzymes. It is also needed for haemoglobin synthesis. Zinc is found as a metallic complex of a number of enzymes. A deficiency of the zinc in the diet leads to skin lesions and may be a cause of dwarfism, hypogonadism and anaemia. All these nutritional deficiency disorders can be corrected by consumption of adequate diet, especially inclusion of abundant fruits and vegetables in the diets.

  1.  Objective of the study

   General objective

            The general objective of the study was to identify some lesser-known vegetables and determine chemical compositionand organoleptic attributes of the dishes based on them as consumed in Njikoka local government area, Anambra State, Nigeria.

The specific objectives of the study were to:

  1. identify these vegetables and the reasons they are sparingly utilized.
  2. process these vegetables and determine their nutrient composition and the acceptance of the yam dishes prepared with the vegetables.
  3. Determine antinutrients content of these vegetables and dishes
  1.  Significance of the study

                This study will be very important to reduce malnutrition especially with the increasing need to educate the public on the need to prevent micronutrient deficiency disorders. These disorders could be prevented through production, preparation and consumption of adequate diets containing plentiful fruits and vegetables.

                 The results of the study will provide data base to eliminate or reduce to the barest minimum the problems of micronutrient deficiency disorders, especially in Njikoka local government area. The results would be good tools for nutrition educators, clinical nutritionists and dieticians to educate and counsel mothers in government hospitals. Community nutritionists and home economic extension workers would use the information to train housewives who prepare different dishes with locally available vegetables and other staples would find the results useful by learning better methods to produce, prepare and consume these foods. Doctors and nurses would benefit from this study because the results would enable them to offer advice and counseling to their clients who have micronutrient deficiency disorders. Mothers would utilise these vegetables much more effectively in their homes. They will cultivate these vegetables in gardens around their houses for use in family menu.

CHAPTER TWO

2.0   Literature review

2.1   Common purslane (portulaca oleracea) local name: ntioke (Igbo).

Common purslane is considered a weed in the united states (http://.enwikipedia.org /wiki/portulaca_olercea). However, it is consumed as green leafy vegetable in many countries including Nigeria.  It has a slightly sour and salty taste. It is consumed throughout much of Europe and Asia. Australian aborigines used its seed to prepare seedcakes.

Description of common purslane

        Portulaca oleracea (common purslane also known as verdolage, pigweed, little hogweed or pusley). It is an annual succulent in the family of portulaceae. Its height may be up to 40cm. it is a native of India and Middle East. However, it is naturalized elsewhere. In some regions, it is consider an invasive weed. There is evidence that the species was in Crawford lake deposits (Ontario) in 1430-89. It is suggested that it reached North America in the pre-Columbian era.(http://en.wikipedia.org/wiki/portulaca_oleracea). It has smooth, reddish mostly prostrate stem and alternate leaves clustered at stem joints and ends. The yellow flowers have five regular parts and are up to 6mm wide. The flowers first appear in late spring and continue into midfall. The flowers open singly at the centre of the leaf clusters for only a few hours on sunny mornings. Seeds are formed in a tiny pod, which open when the seeds mature. Purslane has a taproot with fibres secondary root that enable it to tolerate poor compacted soil and drought.

Uses

     It can be used fresh as a salad, or cooked like spinach. Its mucilaginous quality is the reason it is suitable for preparation of delicious soup and stews.

Medical usage

In Greek popular medicine, purslane is used as a remedy for constipation and inflammation of the urinary system. In antiquity, its healing properties were thought so reliable that Pliny advised wearing the plant as an amulet to expel all evil.

2.2   Malvaceae (Corchorus tridens) local name:ariraa (Igbo)

     Corchorus is a genus of about 40-100 species of flowering plants in the family malvaceae. It is native to tropical and subtropical regions throughout the world. Different common names are used in different contexts, with jute applying to the fibre produced from the plant, molokhia (with many similar transliterations from the Egyptian arabic) applied to the leaves used as a vegetable. Corchorus has been a staple Egyptian food ever prior to the time of Pharaohs. Other names in English include Bush okra, .nalta jute, jute mallow and Jew’s mallow. In Japan the vegetable is known as moroheiya. It is a popular leafy vegetable in the Ilocos region of the Philippines.

Description of Corchorus tridens

         Malvaceae (Corchorus tridens). The plants are tall , usually annual herbs reaching a height of 2-4m, unbranched or with only a few side branches. The leaves are alternate, simple, lanceolate, 5-15cm long, with an acuminate tip and a finely serrated or lobed margin. The flowers are small (2-3cm diameter) and yellow , with five petals, tCe fruit is a many seeded capsule. It thrives almost anywhere and can be grown year round.

Uses

           The plants genus of corchorus satisfy the world with great amounts of fibre needs. The fibres from these plants are the most widely cultivated vegetable fibre after cotton. The leaves are used as a green leafy vegetable. The seeds are  used as flavouring and its dried leaves are used as used as herbal tea.

2.3  Sweet potato leaf (Ipomea batatas) local name: akwukwo nduku (Igbo)

        The sweet potato (Ipomea batatas) is a dicotyledonous plant which belongs to the family Convulvulacea. Amongst the approximately 50 genera and more than 1000 species of this family,, only  Ipomea batatas is a crop plant whose large, starchy, sweet tasting tuberous roots are more important root vegetable (Purseglove, 1991; Woolfe, 1992). The young leaves and shoots are sometimes consumed as greens. It is native to Africa and Asia.

Description 

         The genus Ipomea that contains the sweet potato includes several garden flowers called morning glories, though the term is not usually extended to Ipomea batatas. Some cultivars of Ipomea batatas are grown as ornamental flowers.

                  This plant is an herbaceous perennial vine. It bears alternate heart shaped or palmately lobed leaves and medium sized sympetalous flowers. The edible tuberous root is long and tapered, with a smooth skin whose colour ranges between red, purple, brown and white. Its flesh ranges from white through yellow, orange and purple. Sweet potatoes are native to the tropical parts of the South America. Sweet potatoes were domesticated in South America at least 5000 years ago. They spread early throughout the region, including the Caribbean.

Cultivation

                The plant does not enjoy frost. It grows best at an average temperature of 24oC  (75of), abundant sunshine and warm nights. Annual rainfalls of 750-1000mm are considered most suitable, with a minimum of 500mm in the growing season. The crop is sensitive to drought at the tuber initiation stage, 50-60 days after planting. It is not tolerant to water-logging, as it may cause tuber rots and reduce growth of storage roots if aeration is poor (Ahn, 1993). Sweet potatoes rarely flower when the daylight is longer than 11 hours, as is normal outside the tropics.

            They are mostly propagated by stem or root cuttings or by adventitious roots called “slips” that grow out from the tuberous roots during storage.

            They grow well in many farming conditions. They have a few natural enemies as such pesticides are rarely needed for adequate growth. Sweet potatoes are grown on a variety of soils. However, well-drained light and medium textured soils with a PH range of 4-5-7.0 are more favourable  for the plant (Woolfe, 1992; Ahn, 1993). Swee4t potatoes are  grown in poor soil with little fertilizer. However, sweet potatoes are very sensitive to alminium toxically and dies about 6 weeks after planting if lime is not applied at planting in this types of soil (Woolfe, 1992). Sweet potatoes are sown by vine cutting rather than seeds, as such they rare relatively easy to plant. The rapidly growing vines shade out weeds as such little weeding is needed. In the tropics, the crop is maintained in the ground and harvested as needed for market or home consumption. In temperature regions, sweet potatoes are most often grown on larger farms and harvested prior to frosts set in.

Uses.

            Sweet potatoes leaves are a common side dish in Taiwanese cuisine. It is often boiled with garlic, vegetables oil and dashed with salt prior to serving. The young leaves and vine tips of sweet potato leaves are widely consumed as a vegetable in West African countries (Guinea, Sierra Leone and Liberia for example), as well as in  North Eastern Uganda, East Africa (Abidin, 2004).

            In the Philippines, sweet potato tops or tendrils abound and feature in many of their native dishes, know locally as “Talbos ng Kamote” Filipinos have learned to cook this lowly vegetable in a variety of ways, too many to mention. They usual being simple steamed by placing them on top of steeping rice and consumed with some salty dip. (http.//www.happycow.net/blog/?p=52). The leaves and shoots are edible, the starchy tuberous roots are by far the most important product. In some tropical areas, they are a staple food crop. The vines of sweet potatoes form useful dry foliage crop for ruminants.

They last throughout the dry season as such they serve as source of supplementary feeding when grazing are rather scarce. Industrially, the tubers of sweet potatoes are used as a source of starch, glucose syrup and alcohol. This is because they have free sugars as well as starch. In the Philippines, it is widely believed that lactating mothers fed sweet potato improves their breast milk production.

2.4       Chemical composition and nutritional value

Moisture content

            Fresh leafy vegetables have high moisture content. The moisture for the dried vegetable varies. Moisture content of raw and dry Corchorus tridens leaves were 23, 7 and 27.4%, respectively.

Energy

            Leafy vegetables are not good sources of dietary energy. Fresh leaves of sweet potatoes (1 cup serving) contains 1.2kj (www.freedieting.com/calories/sweetpotatoleaves.html). Fresh sweet potato leaves (1 cup serving) contains 2.2kj carbohydrate.

Protein

            Overall fresh green leafy vegetables have crude protein which ranges from 1.5 to 1.7%. Many reports indicate that green leafy vegetable proteins are low in sulphur amino acids. Corchorus contained the most protein (19-25% (dry weight) of the seven plants analysed in Niger. Fresh sweet potato leaves (1 cup serving ) contains 1.4kj protein.

THE CHEMICAL COMPOSITION AND ORGANOLEPTIC ATTRIBUTES OF LESSER-KNOWN VEGETABLES AS CONSUMED IN NJIKOKA LOCAL GOVERNMENT AREA, ANAMBRA STATE, NIGERIA.