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Weaning is a period of transition for the infant during which its diet changes in terms of consistency and source (Draper, 1994). The critical period for a child's growth and development is between 6 and 24 months. During this period, transition occurs from a diet based on mother's milk to another diet which is usually semi-solid to a more solid diet (Creed-Kanashiro et al; 1990). Such semi-solid or generally called weaning foods should ideally be easily digestible, have high energy density and low bulk (Ezeji and Ojimelukwe, 1993)
Incidentally, in Nigeria and many developing countries, commercially available weaning foods are too expensive for the average family, so nursing mothers often depend on traditional weaning foods which often are low in nutritive value (Okeiyi and Futrell, 1983). Meanwhile, there are many indigenous and unexploited legumes which can be processed and when properly complemented with commonly available carbohydrate sources will provide relatively-affordable weaning foods that will help alleviate protein-energy malnutrition and improve infant nutrition.
The energy density of an infant's weaning food must be sufficient to permit adequate caloric intake and meet the energy needs of the growing child (McGuire, 1991). Weaning foods are traditionally composed of staple cereals and legumes prepared either individually or as composite gruels (Aguilera and Lusas, 1989). Peanut, cowpea, wheat, millet are major agricultural products grown in many developing countries used in the formation of weaning foods. The formulation and development of nutritious weaning foods from local and readily available raw materials have received considerable attention in many developing countries (Schmidt, 1989). The commercially standardized foods are generally good, but quite costly. Hence, the development of low-cost high protein food supplements for weaning infants is gradually becoming recognized in developing countries where malnutrition is still common because traditional foods are not optimally utilized during infant weaning (Omer and Khalifa, 1975).
Prevalence of protein energy malnutrition (PEM) in infants after 6 months is high in Africa (Plahar and Hoyie, 1991) because infants at this stage of development require higher energy, proteins and vitamins. Most of the weaning foods consumed in communities of developing countries are deficient in essential nutrients (FAO. 1999). Poor feeding practices and frequent infectious diseases or a combination of the two are both major factors affecting physical growth and mental development of infants (FAO, 1999). In developing nations, most of the commercial weaning foods are often imported because there are no domestic infant food industries. Besides, the knowledge about food processing is limited and the process applied in infant food processing is delicate and may destroy nutrients. These imported foods are usually always quite expensive for income families and rural dwellers. Effective strategies are now been put in place to improve the nutritional status of weaning meals by promoting the use of high quality home prepared complementary foods and increasing the availability of low cost processed foods for poorer families (Davidson et al; 1986).
In many African countries, comprehensive information and data about introduction, types and compositions of weaning foods for infants are still lacking even though weaning patterns in these countries were found to vary widely due to regional differences in food supplies and food habits. The major criteria for good quality of weaning foods are high protein content, high caloric value, soft texture, low fiber, adequate infant vitamins and minerals, and absence of anti-nutritional factors (FAO, 1999). Cereal grains are relatively low in total protein and generally deficient in lysine, but have sufficient sulphur containing amino acids, the limiting factor in legumes (Shewry, 2007). These shortcomings can be overcome by appropriate blending of cereal products with legumes or fruits.
The world in general has been experiencing a dramatic increase in food prices. The FAO price index of commercial weaning foods surged 57% over the year (March 2007-March 2008) after a 9% increase in 2006. This rise in weaning food prices have given birth to increased poverty for low income earners and nursing mothers (FAO, 2009).
Research has shown that Sugar apple and sweet potato posses a wide variety of benefits, ranging from its nutritional characteristics to its wide medicinal advantages. In spite of these afore-mentioned properties, these food crops remain unexploited and overlooked in many parts of Africa and the world at large.
The present situation calls for a rapid reaction from government and private food industries to reduce importation and explored under-used available foods, in the preparation of weaning foods.
1.2 Justification of work
High cost of imported commercial weaning foods is a key factor for the formulation of traditional low-cost weaning foods. The high nutritional and beneficial health values of some traditionally grown food crops which have not gained recognition in the food industry. These food crops when incorporated into infant diet, can reduce the risk of malnutrition, and prevent infant susceptibility to infectious diseases. It is therefore for these reasons that this project seeks to focus on a way in which these unexploited food crops can be processed into infant meals, to produce an effective, low-cost weaning diet.
The objective of this study is to produce a weaning food formula with locally available materials and assess the nutritional composition of the weaning formula produced.
1.4 Specific objective
To formulate a weaning food from unexploited fruit and food crops and carry out nutritional (proximate and mineral) analysis on the formulated diet.
2.1 Nutrition in infants
Nutrition is an important aspect in the life of an infant even before birth and during the first year of life. Healthy nutrition in infants is essential for growth, development of bones and maturation of body cells and tissues which occur rapidly during the first year of life. A healthy infant's birth weight doubles by about five months and triples by one year and thus, infants have a higher basal metabolic rate about twice that of adults, based on body weight (Whitney and Rolfes, 1999). Such rapid growth requires both nourishment and sleep in abundance. Infants also need concentrated sources of nutrient and energy to support their tremendous growth and development (Wardlaw and Insel, 2000). When an infant is inadequately fed, there is risk of stunted growth and a range of biochemical changes that impair development to the extent of permanently damaging the infant's health (Wardlaw and Insel, 2000). Table 1, shows the recommended dietary allowance for infants and young children.
During the first three to six months of an infant's life, all nutrients required can be provided by the mother's breast milk and so, there's no need for the introduction of solid food before then (Trussel, 2003). By the age of six months, most infants need additional foods, the purpose of which is to complement the breast milk and make certain nutrients available to the child for continued growth and development (Akaninwor and okechukwu, 2004).
Table 1: Recommended dietary allowance for infants and children.
Source: (Nutritional information centre, 2007).
Exclusive breast feeding is very important within the first six months of life. It contains in adequate proportions all the nutrients an infant requires to maintain optimal health and growth and also, protects the baby from leading causes of infant death such as respiratory infection and diarrhea. Breast milk also stimulates the immune system (UNICEF, 1999). Breast milk also contains hundreds of anti-bodies and enzymes. Breast fed children are less susceptible to childhood infections and diseases. Breast feeding is a convenient form of feeding, as it requires no form of processing or use of special equipment. Breast feeding saves money and reduces the need for infant formula within this stage of infant life (Naylor, 2000).
Professionally, literature on infant feeding, in reference to weaning period, defines it as the transition from breast-feeding to complete reliance on other foods (Eschleman, 1991). The word 'wean' however means to accustom, but some authors have used it to mean a complete cessation of suckling. Others also indicate that weaning is the process of gradual introduction of other foods other than breast milk (Kazimi and Kazimi, 1979).
2.3 Weaning foods
Meaningfully, weaning food is intended to bridge the gap between infant breast feeding and introduction to more adult foods (Nout, 1993). So weaning period is ultimately defined as the whole period during which breast milk is being replaced by other foods and patterns of feeding (Knodle, 1980). According to WHO (1988), weaning is described as the introduction of fluids and foods other than breast milk and the transition to solid diet. There has recently been some confusion as to the ideal time to introduce complementary foods to an infant. The WHO has suggested that between four to six months is the best time for complementary foods. However, recent reviews of literature suggest that there is no advantage in introducing complementary foods before six months of age, except in individual cases (Naylor, 2000).
Nout (1993) reported that the total daily intake of weaning foods for development must supply 350kilo-joules of energy and 14g protein for a child weighing 7kg. According to the protein advisory group (PAG, 1971) guidelines for weaning foods, protein content should be 20%, fat levels up to 10%, moisture 5% to 10%, total ash not more than 5% (Badamosi et al; 1995). In recent times, many cereals and legumes have been used as weaning foods for infants and young children. Soybeans, cowpea, groundnuts, have all been used to formulate weaning diets. These cereals and legumes are usually mixed with the baby's milk or purred fruits or vegetables. Initially, only small amounts of food of a smooth constituency are required to teach the baby to take food from a spoon and get used to the texture of solids in the mouth. Weaning foods are generally blend so that the taste is not too far removed from milk with more sophisticated taste and textures being introduced as the baby grows older. Commercial weaning foods are designed to help provide a healthy mixed diet for babies. Products are developed using expert medical nutritional advice and follow current legislation (SI No 29472 1997, SI No 1999) and department of health recommendations for daily amounts of the major nutrients (Barners, 1989). They must also comply with specific regulations on baby foods as well as general food legislation. In addition, commercial baby food should;
Contain products that are consistent in composition and quality;
Ensure that nutritional content and eating quality is maintained throughout processing and packaging.
Be capable of being stored safely and maintain quality throughout their shelf-life; and
Be easy to prepare and appropriate for the recommended age group.
The weaning period represents a stage of rapid growth and development and the weaning diet must supply adequate energy in the form of carbohydrate, protein, fat and essential vitamins and minerals. Thus, when developing commercial weaning foods, manufacturers must take into account the following criteria:
Energy (calories) - Growth of infants depends on the provision of adequate calories for tissue building and energy expenditure (Barners, 1989). The total energy content of the infant's diet must be maintained with controlled limits. An insufficient energy intake in excess of requirements may lead to obesity. The 'energy density' (amount of energy in a given quantity of food) is therefore important. For example, high fibre foods have a low energy density, while sugar and fat have a high energy density (Barners, 1989).
Carbohydrate - This is the source of energy and its intake must be controlled. If given in excess, it may be converted to fat and store as such in the body. The type of carbohydrate that is included in the food is also important, as babies need carbohydrate that is easily digestible (Barners, 1989).
Protein - An adequate amount of protein must be provided in the diet, but excess protein must also be avoided. Protein is the principal material responsible for regeneration of damaged cells and worn-out tissues, and so should be incorporated into an infant's diet (Barners, 1989).
Fat - Infants must receive an adequate amount of fat, as it is the most important source of energy. Fat is also important to provide the body with essential fatty acids. Lack of these essential fatty acids could cause the infants skin to be thickened and dry (Barners, 1989).
Fiber - Unlike adults, infants do no benefit from high fiber intake and hence, fiber levels must be controlled. Fiber can interfere with the absorption of essential minerals in the body, and due to the small stomach capacity of infants, it is difficult to consume high fibrous foods (Barners, 1989).
Vitamins and minerals - Vitamins and minerals need to be added to infant formulas to help aid in easy digestion and easy bowel movement. Also, vitamins and minerals which may have been lost during processing may also be added to fortify the formula (Barners, 1989).
Additives - By law, artificial additives such as preservatives, colorings, artificial sweeteners, antioxidants are not permitted in commercial weaning foods. No artificial flavorings are also used in the production of commercial baby foods (Barners, 1989).
2.4 Nutritive value and nutritional problems of weaning foods in West Africa
Some traditional weaning foods in West Africa are of low nutritive value (Onofiok et al., 1992) and are characterized by low protein, low energy density and high bulk density. Maize pap or koko have been implicated in the etiology of protein- energy malnutrition (PEM) in children during the weaning period (Naismith, 1993). Table ; shows some traditional weaning foods fed to infants by West African mothers. Cereals constitute the primary basis for most of the traditional weaning foods in Africa.
Table 2: Summary of traditional weaning foods fed to infants by West African mothers.
Age of infant (months)
Fermented cereals from maize or sorghum
Fermented corn porridge
Cereal gruel from fermented maize or sorghum
Cereal gruel from fermented maize, millet or sorghum
Source: (Armar, 1989)
2.5 Strategies for solving weaning food problems in Africa
Ignorance and food taboos in West Africa often arise due to the consumption of weaning foods of low nutritional quality (Onofiok et al., 1992). Improving the nutritional quality and value of weaning foods will not eliminate the problem, but rather, training and educating of nursing mothers is necessary to change feeding practices. Nutritional education can easily be incorporated into primary health care programs (Onofiok et al., 1992). Varying the baby's diet, and practicing good hygiene when handling and storage of infant's diet can be included into the education program. The teaching and training of rural mothers can have a long term impact on weaning practices and nutritional status of children. In the Philippines, a weaning education program led to a reduction in the prevalence of malnutrition from 64% to 42% (Nnanyelugo et al., 1990). In Nigeria, the African child survival program yielded similar results. The governments of some West African nations are yet to realize the importance of the training education (Nnanyelugo et al., 1990).
2.6 Formulation and development of weaning foods of high nutritional value
Various methods may be used to improve the nutritive quality of weaning foods (Onofiok et al., 1992). The traditional West African weaning foods can be improved by combining locally available foods that complement each other in such a way that the new patterns of amino acids created by this combination is similar to that recommended for infants (Uwaegbute and Nnanyelugo, 1989). Cereals are deficient in lysine but have sufficient sulphur- containing amino acids that are limiting in legumes. Therefore, combining cereals and legumes has been found to produce amino acid patterns that adequately promote growth (Onofiok et al., 1992).
2.7 Nigerian weaning formulations
Many researchers have worked comprehensively on developing cereal-legume combinations in Nigeria. For example, Fashakin and ogunsola (1982) formulated nut-ogi (mixture of corn gruel and peanut). Akinrele and Edwards (1971) formulated soy-ogi (corn gruel and soya bean); and the collaborative research support program (CRSP) cowpea linkage project at the university of Nigeria, Nsukka formulated "cerebabe" (corn gruel plus cowpea). Other useful combinations include ogi and melon protein (corn gruel plus melon seed) and cowpea-ogi (Fashakin et al., 1989). Some of these combinations have been adopted by the food-processing industries and are available on the Nigerian market (Onofiok et al., 1992).
However, Fashakin et al (1989) observed that no single protein from the above sources was adequate to promote growth or enhance nitrogen retention as well as a milk-based diet. To this end, a mixture of cowpea, melon, soybean and ogi was found to be superior to any single protein source in protein efficiency ratio, net protein retention, biological value and net protein utilization (Fashakin et al., 1989).
2.8 Ghanaian weaning formulation
Low-cost, nutritious, well-balanced weaning foods rich in protein and energy have been produced from locally available foods in Ghana. One such weaning formulation is 'weanimix', a blend of legume (groundnut and cowpea) and cereal (maize) in the ratio 1:4 w/w (Onofiok et al., 1992).However, Takyi et al., (1991) suggested that 'alfalafa' could also be incorporated into the weaning diets of infants, as this legume was found to contain higher levels of protein, minerals and carotene and could support child growth better than normal composition of 'weanimix'
2.9 Sweet Potato
Sweet potato (ipomea batatas) is a very significant crop in the developing world and a traditional, but less important crop in some parts of the developed world. According to the United Nations food and agriculture organization (FAO) report in 1997, sweet potato is one of the seven crops in the world which produces over 135 hundred million metric tonnes of edible food products in the world annually. Only potato and cassava among the root and tuber crops produce as much. Of the total sweet potato production in the world, 80-85% is produced in china alone (FAO, 1997), with Asia having the next highest production and then followed by Africa and Latin America (Wanda, 1987).
Sweet potato, an important staple food crop in Nigeria is very valuable in the diet of the rural poor in the tropics. It is a low-input crop and is mainly used as a vegetable, a dessert, source of starch and animal feed (Odebode, 2004). In Nigeria, sweet potato is also eaten as a substitute for yam as a result of lower cost of production. This food crop is very important in many enclaves in Nigeria, though its potential is not well known, in spite of its nutritive and agronomic characteristics (Woolfe, 1992). Table 3 shows the nutritive value of sweet potato as compared with other crops.
Table 3: Nutrient value of sweet potato as compared with other crops
Nutrients per 100g edible portion
Vitamin C (mg)
Sweet potato (rare variety)
Sweet potato (yellow variety)
Sweet potato (orange-flesh variety)
Source: (Human nutrition in tropical Africa FAO, 1970)
2.9.1 Sweet potato and its potentials
Sweet potato is drought-resistant; it provides good ground cover and grows on soils with limited fertility. The roots and leaves are sources of carbohydrates, protein and minerals. It is eaten as a vegetable after boiling, baking or frying and sometimes sliced and sun-dried to produce chips, which are ground into sweet potato flour. The tubers can be boiled, baked or fried (Woolfe, 1992). Other sweet potato products in Nigeria include potato chips, sweet potato starch, alcohol, wine and animal feed (Odebode, 2004).
The high nutrient content of sweet potato, calls for a need to find an alternative utilization of the crop other than boiling, frying or baking that is acceptable and cheap to different care of people in the society (Odebode, 2004). Sweet potato is one of the food security crops in that, it could contribute to alleviating poverty of many rural dwellers through improved processing techniques (FAOSTAT, 1998). But, over the years, it has been reported that sweet potato has not received the appropriate consideration it deserves in the diets of Africans in general, especially despite the fact that it is produced and consumed in large quantities and has some nutritional and socio-economic functions. There is therefore the need to research various modes of processing sweet potato into other products like flours and starch, so that its importance becomes highly significant in the food industry (Odebode, 2004).
2.9.2 Nutritional quality of sweet potato
The nutritional qualities of sweet potato which are important in meeting human nutritional needs include: carbohydrates, protein, vitamins (A and C), fiber, iron and potassium. Due to the various roles that sweet potato plays in foods, the concept of nutritional quality and its contribution must be transformed to meet individual roles in the human diet. For instance, staple type diets could require high carbohydrate, protein and fiber. Similarly, supplemental types of sweet potato must have many of the same characteristics as staple types in terms of nutritional components. However, as they will not be used as major food components, the level of substituent may be more flexible (Mais, 2008).
2.9.3 Some major components of sweet potato
18.104.22.168 Dry matter
Sweet potato can contain as much as 44% dry matter (Moorthy, 2002). However, most commercial cultivars, especially in the United States contain about 20-30% dry matter (Hoover, 2000). The major component of dry matter is carbohydrate which makes up 90% in most cultivars. The major carbohydrate component is starch which in sweet potato is about 60-70% amylopectin and 30-40% amylose (Chen et al., 2002).
Sweet potato can contain as much as 50-55% sugar (Moorthy, 2002). Sucrose is the major form of sugar in raw uncooked roots, but glucose and fructose are also present in cooked roots. Major product of starch conversion in sweet potato is maltose, while the remainders of carbohydrates (primary cellulose, hemi-cellulose and pectin) are collectively called fiber (Moorthy, 2002).
22.214.171.124 Fiber content
The fiber content in sweet potato varies to a great extent depending on varieties and age of the crop, where fiber content increases with maturity. Fiber content in flour derived from tuber extractions may also vary to a greater extent, depending on the techniques and sieves used for the removal of fibrous materials. Sweet potato flour containing 2-3% has different composition as compared to the isolated starch having fiber values ranging between 0.1- 0.15% (Moorthy, 2002).
Fiber is an important nutritional contributor of sweet potatoes in human diet. Potential benefits of soluble dietary fiber includes reduction of bowel transit time (Kelsay, 1988), reduction of colorectal cancer, lowering of serum blood cholesterol, reduction of glucose metabolism and promotion of the growth of beneficial gut micro-flora (Brennan, 2005).
126.96.36.199 Protein content
In sweet potato, the protein is generally low, ranging from 1.0 to 14.2% (dry weight basis), with most levels varying between 1.0 and 8.5% (Bradbury, 1989). Sweet potato protein is of good quality and contains large amounts of amino acids except tryptophan and total sulphur amino acids when compared with FAO reference protein (Wanda, 1987).
2.10 Sugar apple
Sugar apple (Annona Squamosa), a member of the Annonaceae family, is a tropical and subtropical fruit tree that is widely distributed in Asia, Africa and the Americas (Nakasone et al., 1998). The sugar apple is an economically important tree in Taiwan especially, which makes it the largest commercial producer, followed by Spain, Australia and Peru (Yang,1998). It still remains foreign to many parts of the world, even though it is highly cultivated. In Nigeria, it is found in the rainforest and derived savannah zone either domesticated or growing wild. The ripe mature fruit is soft to touch. The outside of the fruit is scaly, while the pulp is white and juicy with brownish seeds.
Sugar apple has is a highly perishable fruit, due to its high respiration rate, extremely limited post-harvest shelf life, making handling, storage and distribution difficult (Yang, 1998). Therefore, developing new processing techniques to overcome short shelf-life problems is highly essential.
2.10.1 Nutritional composition of sugar apple
Sugar apple contains certain important nutritional properties, essential to meeting human nutritional needs, these include, carbohydrates, natural sugars, fiber, vitamins and minerals. Tables 5 and 6; show the proximate composition and mineral and vitamin composition of sugar apple respectively.
Table 5: Proximate composition of sugar apple
Composition (per 100gm)
Total soluble solids (Brix)
(Source: http//lifestyle.iloveindia/lounge/benefits of custard apple)
Table 6: Mineral and vitamin composition of sugar apple
(Source: http//lifestyle.iloveindia/lounge/benefits of custard apple)
2.10.2 Sugar apple and its benefits
Sugar apple has varying benefits, which are spread between the seeds, pulp, flesh, bark and even flowers. The pulp is a depot of vitamin C, which is an antioxidant and helps in neutralizing free radicals (http//lifestyle.iloveindia/lounge/benefits of custard apple). It also contains vitamin A which is good for the hair, eyes and healthy skin. Sugar apple is also a rich source of minerals such as magnesium, calcium and sodium, which play vital roles in relaxing muscles and protecting against diseases. It is also rich in dietary fiber which helps in discharge as it contains low fat levels, it is good for maintain optimum health (http//lifestyle.iloveindia/lounge/benefits of custard apple).
Sugar apple also serves as an expectorant, stimulant, coolant and haematinic and is useful in treating anemia. The seeds are rich sources of oil, protein and have insecticidal and abortifacient properties (http//lifestyle.iloveindia/lounge/benefits of custard apple).
MATERIALS AND METHOD
3.1.1 Weaning food ingredients
The raw materials to be used would include fresh sweet potato roots (yellow-flesh cultivar) obtained from the Volta region of Ghana, sugar apple fruits obtained from local central market, Kumasi, Ghana. In addition, soya bean milk extracted from fresh soya bean obtained from the local market, sucrose and vanilla flavoring.
Formulations were made with varying compositions of the raw materials using Statgrahpics Centurion software XV using the following constraints as shown in Table [No]. The detail of the formulation is shown in table 8.
Table [No] 7
Table 8; Formulations for product development
188.8.131.52 Preparation of sweet potato roots
Sweet potato puree will be prepared by washing, steam cooking at 70oC for 15mins and peeling of roots. It will then be mashed using a clean laboratory pestle and mortar to obtain a puree.
184.108.40.206 Preparation of sugar apple puree
The fresh fruit would be steam blanched at 60oC for 15mins. Using a kitchen knife, the flesh of the apple will be removed. The seeds will be separated from the pulp manually. The seed will then be oven dried at 65-70oC for 6 hours. The decorticated seeds will be milled and then pre-cooked.
220.127.116.11 Preparation of soya bean milk
Fresh sweet potato roots
Pulp + Milled Seed
Roasting and Milling
Fig 1: Flowchart for formulation of weaning diet.
3.2 PROXIMATE ANALYSIS
Proximate analysis would be carried out on both the raw samples and the formulated diet.
3.2.1 Moisture content
The moisture content will be determined according to the standard methods of the Association of Official Analytical Chemists (AOAC, 1995).
The moisture content in weighed sample is removed by heating the sample in an oven (under atmospheric pressure) at 105 Â± 1Â°C.
The difference in weight before and after drying is then calculated as a percentage of the initial weight of the sample.
A sample of 2 grams will be weighed into a pre-dried crucible and then placed into an oven set at 105Â°C for 5 hours. After drying, the covered samples are transferred to desiccators and cooled to room temperature before re-weighing. Results obtained will be recorded in duplicate and the mean value calculated.
3.2.2 Crude protein
Crude protein will be determined according to the method by (AOAC, 1995) using micro-kjeldahl nitrogen digestion and distillation method. 0.2g of oven dried sample will be weighed into a 100 ml Kjedahl flask. 0.4g of catalyst mixture and 3.5 ml of concentrated sulphuric acid will be added. The sample and contents will be heated on an electric heater for 2 hr. The sample will be cooled, diluted, and placed in the distillation apparatus, 20 ml of 40% NaOH will be added, and distilled for 7 min. The ammonia evolved will be collected in 10 ml of 2% boric acid solution, contained in a conical flask attached to the receiving end. The trapped ammonia is titrated against 0.02 ml HCl using a universal indicator (methyl red + bromocresol green).
3.2.3 Fat content
Crude fat content will be determined according to AOAC (1995) standard method.
The method determined the substances, which are soluble in petroleum ether (B.p, 40 - 60Â°C) and extractable under the specific conditions of Soxhlet Extraction Method. The dried ether extract is weighed and reported as percentage of the dry matter as crude fat.
A sample of 2g will be weighed into an extraction thimble and covered with cotton and placed in the soxhlet extractor. Then a round bottom flask, containing100ml petroleum ether will be attached to the extraction unit and the temperature adjusted to produce about 150 to 200 drops of the condensed solvent per minute for 8 hours. At the end of the distillation period, the flask will be disconnected from the unit and the solvent redistilled. The flask with the remaining crude ether extract will be put in an oven at 105Â°C for 3 hours and cooled to room temperature in a dessicator, it will then be re-weighed and the dried extract registered as crude fat.
3.2.4 Ash content
To determine the ash content of the samples, using AOAC (1994) Standard Method.
The inorganic materials are customary determined as a residue after being ignited at a specific heat degree.
A sample of 2 g will be weighed into a preheated, cooled weighed crucible. The crucible with the sample will be placed into 40 a muffle at 550-600Â°C until a constant weight is obtained. The weight of the residue after ashing is defined as the ash content and expressed as percentage based on the dry matter content of the original sample.
3.2.5 Crude fiber
Crude fiber will be determined according to the AOAC (1995). Two gram of de-fatted samples will be treated successively with boiling solutions of H2SO4 and KOH 0.26N and 0.23 N, respectively. The residue is separated by filtration, washed, dried, weighed and ashed at 500Â°C. The loss in weight resulting from ashing corresponds to crude fiber of the sample:
3.2.6 Available carbohydrate
Available carbohydrates will be calculated by subtracting the sum of fat, protein, crude fiber and ash as a percentage from 100 as described by AOAC (1995).
3.3 MINERAL ANALYSIS
Protocols used citied by
The trace elements will be determined according to the method described by Pearsons (1994). Two gram of dry sample will be weighed in a clean dry crucible. The crucible then placed in a muffle furnace for 2 hours at 550Â°C. The content of the crucible will be cooled and 10ml of 5 N HCI will be added and placed in a hot sand bath for about 10 - 15 minutes. The contents will be filtered with distilled water into a 50 ml volumetric flask and the filter paper will be washed with distilled water and made to volume (iron will be determined by atomic spectrophotometer. Potassium and sodium determined by flame photometer).
3.3.2 Potassium and sodium contents
The potassium (K+) and sodium (Na+) contents will be determined according to AOAC (1995) using corning 400 flame photometer; a 0.5 ml of the extract will be taken and diluted in a 50 ml conical flask with distilled water. The standard solutions of the KCI and NaCI will be prepared by dissolving 2.54 g and 3.33 g of KCI and NaCI, respectively, each in 1000 ml distilled water. A 10 ml of the solution will be taken and diluted with 1000 ml distilled water to give a 10 ppm concentration. The flame photometer will be adjusted to zero degree using distilled water as a blank and to 100 degree using standard solution (AACC, 2000).
3.3.3 Calcium and magnesium
Ca++ and Mg++ will be determined together by taking 2 ml of the extract in to a 50 ml conical flask. Twenty milliters of distilled water, 10 drops of buffer (6.7 g ammonium chloride in 57 ml conc. ammonium, diluted to 100 ml with distilled water and 3 - 4 drops of eriochrome blank (EB.T.) indicator (0.1 g eriochrome + 0.9 g hydroxylamine hydro-chloride will be dissolved in 20 ml of about 95%ethanol) then added to the extract. The mixture will be titrated with (0.1 N EDTA) until a blue color indicating the end point is reached.
The Mg++ content will be calculated by subtracting the calcium from Ca++ Mg++ contents (AACC, 2000).
3.3.4 Phosphorus determination
Analysis of phosphorus will be carried out according to the method of Chapman and Pratt (1982). 2ml of the extract will be pipetted into a 50 ml volumetric flask, 10ml of ammonium molybdate43 ammonium vanadate reagent [22.5 g of (NH4)6 MO7 O24 4 H2O in 400 ml distilled Water + 1.25 g ammonim vanadate in 300 ml boiling water + 250 ml conc. HNO3 then diluted to 1 liter] will be added. The contents of the flask will be mixed and diluted to volume. The density of the color will be read after 30 minutes at 470 nm using a colorimeter (AACC, 2000).