Effects Of Drying Methods On Nutrient Contents Of Moringa Oleifera (Lam.) Leaves

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Effects Of Drying Methods On Nutrient Contents Of Moringa Oleifera (Lam.) Leaves


Abstract


The study was carried out to determine the effect of drying methods on the nutrient contents of Moringa oleifera at the Agric. Chemical Laboratory (Usmanu Danfodiyo University Sokoto) and The Energy Research Field of Sokoto Energy Center, Sokoto. Fresh leaves were collected and cleaned then dried using different drying methods viz. shade drying, solar drying, oven drying and sun drying. The treatments were analyzed for proximate and mineral contents using standard methods. Statistical analysis indicates that moisture was lowest in solar drying (2.67%). Shade drying produces the lowest lipid content (2.33%). High protein content was recorded under shade drying (28.50%). Overall, shade drying was noted to preserve the nutrient contents of Moringa oleifera better. In view of economic importance of Moringa, there is need to educate the local populace on the best method of preserving this vegetable.


Chapter One


1.0 Introduction

Moringa oliefera Lam. commonly referred to simply as “Moringa” belongs to the kingdom Plantae, Order Brassicales, Family Moringacacae, Genus Moringa and Species Moringa oliefera. Moringa oliefera is native to the Indian subcontinent and has become naturalized in the tropical and subtropical areas of the world. It is the most widely cultivated species of the Genus Moringa, which is the only genus in the Family Moringacacae. It is an exceptionally nutritious vegetable tree with a variety of potential uses. Moringa olieferatrees are well naturalized in the northern parts of Nigeria where the leaves are popularly known as ‘zogala’ and widely consumed by populace (Pallavi and Dipika, 2010).

The plant is described as a fast-growing plant and drought resistant crop variety. It can survive in less fertile soil (Fahey, 2005, Anwar et al., 2007). The tree itself is rather slender, with drooping branches that grow to approximately 10-12m in height. The “moringa” tree is grown mainly in semi-arid, tropical and subtropical areas. While it grows best in sandy soil, it also tolerates poor soil, including coastal areas. Moringa oliefera tree has a wide-open typically umbrella-shaped crown and usually, a single stem which tends to be deeply rooted. The wood is soft and its bark is light (Anwar et al., 2007).

The moringa leaves are excellent, concentrated source ofproteins, vitamins and minerals. Out of the 120 vegetable species tested for their nutrient content, antioxidant activity, and the facility with which they are grown and processed, moringa oliefera leaves were top ranked by the World Vegetable Centre (AVRDC) (Moyo, et al., 2011). However, seasonal variation and varieties has been reported to have effects on the nutritional content. This is similar to the reports of Rodrigues, et al. (2011) on the effects of meteorological conditions on antioxidant flavonoids in Portuguese cultivar of white and red onions.

The Moringa oliefera leaves either fresh or processed into dried powder, can be used as an everyday food item in a multitude of ways: in ready-made meals, juices, breads, pasta, fritters, condiments, tea and instant soups. It can be used in households, school cafeterias, dispensaries, maternity wards, rehabilitation centers as well as in restaurants and supermarkets (Armelle and Melanie, 2010). Moringaoliefera leaf is an exceptional resource for developing countries. Processed or fresh, the Moringa olieferaleaves are not only a new, promising source of income and employment, but also outstanding, nutritionally rich vegetables for families and markets (Foidl, et al., 2001).
The Morigaoliefera plant leaves contain very high level of nutrients. The Moringa olieferatree however, is a deciduous plants and it sheds its leaves in the dry season.

Food provides the body with chemical substances known as nutrients, which in turn furnish the body with energy, regulate body processes and promote growth and repair of body tissues. When food is selected wisely and consumed in sufficient quantity, it provides all the nutrients which the body needs in the proportion required to function properly (FAO, 1988).

Some of the nutrients supplied by food are called essential nutrients because they cannot be synthesized in the body, at least in the amounts needed, and they enable the body to maintain good health.

Other nutrients used by the body are known as non-essential nutrients. They, too, come from chemical substances supplied by food, or from their breakdown products which may be synthesized into nutrients in the body. The body’s supply of essential nutrients comes preformed in food; non-essential nutrients are, generally speaking, constructed in the body from chemical substances supplied in the food (FAO, 1988).

All studies of the interaction of nutrients in humans indicate the need for a balanced diet. Clinical reports show that Individuals with a deficiency in one nutrient, such as a vitamin, often have deficiencies in other nutrients as well. The presence or absence of one essential nutrient may also affect the availability, absorption, metabolism or dietary need for other nutrients. There are six main types of nutrients: Carbohydrates, Proteins, Fats, Vitamins, Minerals, Water (FAO, 1988).

Except for water, each of these classes of nutrients is made up of several different chemical substances, some of which are essential nutrients. Water is, of course, also essential for human survival. The energy nutrient, that is carbohydrates, proteins and fats, are converted in the body to simpler compounds that may be reassembled into body compounds or may he oxidized, releasing energy. This energy is expressed in terms of kilocalories or kilojoules (FAO, 1988). Carbohydrates, fats, proteins and vitamins are organic chemical substances. That is, their chemical structures contain carbon. Minerals and water are inorganic substances, almost all of which do not contain carbon.
Carbohydrates include starches, sugars and many other compounds. The important classes of carbohydrate are polysaccharides (many of which are starches), disaccharides and monosaccharide (which are sugars). In the presence of sunlight, through the process known as photosynthesis, green plants are able to synthesis carbohydrates by trapping water from the ground and carbon dioxide from the air. In this process, oxygen from the carbon dioxide is released and returned to the atmosphere. When carbohydrate is synthesized in a green plant, much of it is stored in the plant cells as cellulose and starch (which are polysaccharides) and glucose (a monosaccharide) (FAO, 1988).
Dietary fibre, another form of carbohydrate, is important in proper bowel function. Meals must include fibrous roughage supplied mostly by vegetables. Finally, foods that are usually considered for their carbohydrate content, for example cereals, also supply significant quantities of protein, and the B vitamins (FAO, 1988).

Proteins are very large molecules made up of many amino acids linked together. Some amino acids are known as essential amino acids because they cannot be synthesized in the body in large enough amounts to meet the body’s needs. The other amino acids are considered non-essential because the body is able to synthesize sufficient amounts when amino groups are available in the body.

In general, proteins supply essential amino acids which the body uses in making new tissue and repairing tissue proteins damaged in the continuous wear and tear of the body processes. These functions account for increased protein requirements during such periods of growth as infancy, childhood, adolescence and pregnancy (FAO, 1988).
The term lipid is used to refer to a fat, oil or other fat- like substance found in food and used in the body. However, the term fat is more generally used and understood. Fats, like carbohydrates, are made up of carbon, hydrogen and oxygen. Fats contain more carbon and lees oxygen than carbohydrates and thus have greater energy value. One of the ways humans store energy in their bodies for future use is in the form of fat. Some plants, in addition to storing energy as carbohydrate, also store fat in their nuts, seeds, seed germs and fruits. In eastern Africa; foodstuffs of this group help to supply needed dietary fats (FAO, 1988).

The term mineral means an element or compound in a solid, crystalline and inorganic form. In nutrition, minerals are commonly referred to as mineral elements or, in the case of those present or required in small amounts, a- trace elements or trace minerals. Although the analysis of mineral ash shows the presence of more, there are only 22 mineral elements essential to good human nutrition. They are classified as: Macronutrient elements which include: calcium, chloride, magnesium, phosphorous, potassium, Sulphur, sodium. Micronutrient elements which include: arsenic, chromium, cobalt, copper, fluoride, iodine, iron, manganese, molybdenum, nickel, selenium, silicon, tin, vanadium and zinc (FAO, 1988).

Collectively about 4 to 5 percent of body weight is in the form of minerals, compared with 14 to 16 percent of protein and 12 to 20 percent of fat. Mineral elements have many essential roles to play in body metabolism or as constituents of body tissue. Many of them are indirectly involved in the growth process. Most minerals are obtained from foods in which they exist as salts and organic compounds. Highly refined foods and foods such as sugar contain few minerals (FAO, 1988).

Drying as a form of processing ensures the availability of perishable products all year round (Habouet al., 2003). Drying method is used in Nigeria for preserving leafy vegetable and example of such vegetables is leaf of Moringaoleifera. Drying leafy vegetable increase their shelf life upon storage (Eklouet al., 2006). The need for well established data on the nutrients composition of food is of great importance in identifying and solving nutritional problem in the society.

Drying agricultural produce by sun drying is widely used in most of the developing countries of the tropical region. However, solar drying is an elaboration of sun drying and was the most hygienic method of drying (Bala and Woods, 1994). The leaves of Moringaoleifera are preserved traditionally using sun drying (open air) and this is associated with possible contamination by microorganisms, infestation by insects and rodents. Their quality can be diminished and even become inedible (Diamante and Munro, 1993).


1.1 Statement of the Research Problem

The need to meet nutritional requirements through adequate food supplies and proper selection of diet has been a basic determinant of stability and progress, since human being require food to pursue essential functions such as growth, development and reproduction (Onimawo, 2001). Hunger and malnutrition are highly prevalent in the developing countries. FAO (2001) reported that absolute number of food-unsecured in developing world increased from 780 million to 798 million. In Nigeria, about 7.8 million people were undernourished in 1995-1997 and increased 9.1 million in 1999-2001 (SCN, 2004).


1.2 Justification

The justification of this research is based on the fact that Moringaoleifera leaves can be a source of income and employment to some individuals. It is also used for many purposes including medicine, food, oil, industrial purpose e.t.c. Leafy vegetables are very much prone to attack by pathogens especially fungi if not adequately preserved. The best drying method if applied will go a long way in ensuring the food security of the local people.


1.3 Aim and Objectives

The main aim of this research work is to investigate the effect of different drying methods on the proximate and other nutrient composition of Moringa oliefera leaves. The specific objectives are:

  1. To determine the effects of various drying methods on the proximate composition of the leaves of Moringaoleifera.
  2. To determine the effects of various drying methods on the mineral composition of the leaves of Moringaoleifera.

Chapter Five


5.0 Discussion

From the result obtained, shade dried treatment is significantly higher than the other treatments. The value obtained may noted to be higher than the value (6.35%) reported by Mbah et al. (2012).Removal of moisture by heat generally improves the digestibility of foods, increases concentration of nutrients and can make some nutrients more available (Morris et al., 2004). Moisture contents of fruit and vegetables provide an enabling environment for growth of micro-organisms, thus it has to be reduced if vegetables and fruits have to be preserved or kept for long time to be used and this may inhibit autolytic enzymes (Ladanet al., 1997). From the four different treatments, solar dried treatment was found to be most effective due to it low moisture content as it can decrease deterioration and can have long shelf life.

Potassium in shade dried treatment has found to be significantly higher than solar dried, oven dried and sun dried treatments. Higher potassium level in shade dried treatment. The higher lipid contents in solar and sun dried treatments could not be and added advantage over the fresh sample for use as a therapy and are vital for bone (Dzomekuet al., 2006).

Lower protein values for solar and oven dried treatment from this research shows that macro nutrients value decreases when dried under heat. The result tallied with the assertion of Laden et al. (1997) that heat reduces the nutrients values of tomatoes. The significant decrease of macro nutrients upon drying may be attributed to the stability of the bonds involved in them. The intensity of heat applied due to efficiency of the dryers was found t be commensurate with the decrease in protein content. Morris et al. (2004) reported losses of these macro nutrients especially protein due to application of heat.

The higher lipid contents in solar and sun dried treatments could not be considered as a good source of lipid, which is in agreement with the fact that green leafy vegetables are ‘Heart friendly food’ (Pallavi and Dipika, 2010). The lipid content of shade and oven dried treatments were found to be lower and most effective in terms of lipid than solar and sun dried treatments. This enhances the storage life of the flour due to the reduction in chance of developing rancid flavor and may not be a good source of fat soluble vitamins. Lipid can be used as basis in determining, processing temperatures as well as the auto-oxidation which can lead to rancidity (affect flavor of food).

Higher fiber content for solar and oven dried treatments could be due to dehydration and concentration of dry matter. Fiber has useful role in providing roughage that aids digestion (Lisa, 1997). Higher fiber content in diets have been reported to have resulted in increased in the removal of carcinogen, potential mutagens and steroids. Solar dried treatment was statistically higher in carbohydrate content and can be a good source of energy for animals and human beings. However, sun dried, oven dried and shade dried treatments are statistically different to each other and statistically lower than solar dried treatment.

Solar and oven dried treatments in calcium were higher than that of shade and sun dried treatments. It is also of remarkable interest that the dried Moringa leaves have high deposit of mineral elements. Calcium was observed to be higher compared with other plant sources (Nkafamiyaet al., 2010). It is required for formation and maintenance of bones and teeth thus, preventing osteoporosis. It is also needed for normal blood clotting and nervous function. Also, it can be seen that in Sodium shade dried treatment is significantly higher than solar dried, oven dried and sun dried treatments. However, the three treatments (solar, oven and sun dried) were found to be statistically similar to each other and lower than shade dried treatment.

Shade dried, solar dried, oven dried and sun dried in Nitrogen are significantly different to each other. Shade dried treatment is statistically higher than the other three treatments. The results from this research work indicate that mineral element composition of Moringa oleifera vary with drying method. There is no known explanation regarding unusual observation. However, it may be due to environmental, genetic factors and the method of analysis employed. The higher Ash composition of solar followed by oven, shade and sun dried treatments (having lowest and comparable values) may indicate higher mineral elemental composition of leaves of Moringa oleifera.
Shade dried and sun dried treatments in Magnesium were found to be significantly higher and similar to each other, while solar dried and oven dried treatments are lower than sun dried and shade dried treatment. Also, it can be seen that in phosphorus shade dried is significantly higher (P>0.05) than sun dried, solar and oven dried treatment. The higher calcium and phosphorus in the dried treatment are vital for bone a similar observation was reported with tomatoes by (Ladanet al., 1997).


5.1 Conclusion

It can be concluded that drying generally improves the nutrient contents of Moringaoleifera leaves. There is no significant effects (P< 0.05) between the four treatments on the Nitrogen and Protein contents of Moringaoleifera. Oven dried treatment have higher content of Fiber, while shade dried treatment have higher content of Protein, Phosphorus,

Potassium and Sodium. It is therefore recommended that Moringaoleifera leaves should be dried using shade drying method due to the higher retention of some essential minerals.


5.3 Recommendation

  1. Further research should be carried out on the effect of drying methods on the Vitamins and anti-nutrients, since moringa oleifera is a cheap source of nutrients. It should be used in food supplementation, fortification and complementation (especially in infant feed).
  2. There should be proper education in various communities on the economic and nutritional importance of shade drying, solar drying, oven drying and sun drying food preservation.

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