CHAPTER ONE

INTRODUCTION

1.1 background to the study

Infants and young children suffer from malnutrition in most developing countries. The growth of infant in the first and second year of life is very rapid and breast milk alone cannot meet the child’s nutritional requirements.  The infant needs supplementary feeding starting from 46 months (Achinewhu, 1987; Ijarotimi and Famurewa, 2006). Many brands of preparatory foods have been developed and marketed; however these brands are too expensive and therefore are beyond the economics of low income families. The high price of proprietary weaning food and animal proteins combined with faulty feeding practices are mostly responsible for aggravating malnutrition among children (Dutra-de –Olivera, 1991). Protein energy malnutrition (PEM) generally occurs during the crucial transitional phase when children are weaned from liquid to semi solid or fully adult foods. Children therefore require nutritionally balanced calorie-dense supplementary foods in addition to mother’s milk (Berggren, 1982; Cameroon and Hafvander, 1971). Several studies have reported that most of the weaning foods consumed by children in many parts of developing nations are deficient in essential macro and micro nutrients (Levin et al., 1993; Brabin and Coulter, 2003; Milward and Jackson, 2004). In view of this nutritional problem, several strategies have been used to formulate weaning food (Lalude and Fashakin, 2006; Ijarotimi and Ashipa, 2006; Ijarotimi and Bakare, 2006) through a combination of locally available under-ultilized food crops that complement each other.

Tigernut (Cyperus esculentus) is an underutilized readily available crop in Nigeria. It belongs to the family of Cyperaceae, which produce rhizomes from the base and are somewhat spherical. The tubers contain significant amount of protein, fat, minerals and vitamins (Alobo and Ogbogo, 2007; Oladele and Aina, 2007). In addition, tigernut tubers could be used for the treatment of flatulence, indigestion, diarrhea, dysentery and excessive thirst (Chevallier, 1996). The use of such readily available underexploited crop to complement with legumes such as soybeans in developing a simple household low cost weaning food hold promise in alleviation  of infant  malnutrition. The challenge therefore is to develop a nutrient dense supplementary infant food from locally available underutilized crops that could be adoptable at the household level.

1.2 Uses Of Soybeans

When the farmer sells soybeans to a grain dealer, the beans may then go to a number of ultimate destinations. When processed, a 60-pound bushel will yield about 11 pounds of crude soybean oil and 47 pounds of soybean meal. Soybeans are about 18% oil and 38% protein. Because soybeans are high in protein, they are a major ingredient in livestock feed. Soybeans are processed for their oil (see uses below) and meal (for the animal feed industry). A smaller percentage is processed for human consumption and made into products including soy milk, soy flour, soy protein, tofu and many retail food products. Soybeans are also used in many non-food (industrial) products.

Some soybeans are needed to produce another crop each year. High quality soybeans are grown, harvested and purchased by the seed industry to be used as seed for the next year’s crop.  Researchers in the seed industry focus on developing new soybean varieties with outstanding characteristics including high yield, lodging resistance, nematode resistance, herbicide tolerance, and many other desirable characteristics.

Food for Humans

Nearly all soybeans are processed for their oil. Soy processors (such as Cargill & ADM) take the raw soybeans and separate the oil from the meal. The oil may be refined for cooking and other edible uses, or sold for biodiesel production or industrial uses. The processors bake the high-protein fiber that is left after the oil is removed and sell it for animal feed.

Soybean oil is used in cooking and frying foods. Margarine is a product made from soybean oil. Salad dressings and mayonnaises are made with soybean oil.

Some foods are packed in soybean oil (tuna, sardines, etc.)  Baked breads, crackers, cakes, cookies and pies usually have soybean oil in them.

Feed for Animals

The high-protein fiber (that which remains after processing has removed the oil) is toasted and prepared into animal feed for poultry, pork, cattle, other farm animals and pets.  The poultry and swine industries are major consumers of soybean meal. Over half of the soybeans processed for livestock feed are fed to poultry, about one-quarter is fed to swine, and the rest is used for beef cattle, dairy cattle and pet food.

Soy protein is increasingly found in fish food, both for home aquariums and for the fish grown for eating.  Most marine species were fed fish meal at one time, but the scarcity and increasing cost of fish meal has led producers to switch to high protein soymeal for a variety of marine species. Around the world, soy protein may be found in feed for most animals.

Other Uses

Biodiesel —  biodiesel fuel for diesel engines can be produced from soybean oil by a simple process called transesterification. This process removes the glycerine from the oil, leaving soy biodiesel.  Soy biodiesel is cleaner burning than petroleum-based diesel oil.  Its use reduces particulate emissions, and it is non-toxic, renewable and environmentally friendly.

Biocomposites are building materials made from recycled newspaper and soybeans. They replace other products traditionally made from wood, such as furniture, flooring, and countertops.

Particleboard, laminated plywood and finger-jointed lumber are made with soy-based wood adhesives.

Soy products are also found in many popular brands of home and commercial carpet, and in auto upholstery applications.

Soy oil produces an environmentally friendly solvent that safely and rapidly removes oil from creeks, streams and shorelines without harming people, animals and the environment. Soy is an ingredient in many industrial lubricants, solvents, cleaners and paints.

Candles made with soybean oil burn longer but with less smoke and soot.

SoyInk is superior to petroleum-based inks because soy ink is not toxic, renewable and environmentally friendly, and it cleans up easily.

Soy crayons made by the Dixon Ticonderoga Company replace the petroleum used in regular crayons with soy oil making them non-toxic and safer for children.

Soy-based lubricants are as good as petroleum-based lubricants, but can withstand higher heat. More importantly, they are non-toxic, renewable and environmentally friendly.

Soy-based hydraulic fluid and rail flange lubricants are among the more recent products developed with check-off funds.

Soy based foams are currently being developed for use in coolers, refrigerators, automotive interiors and even footwear.  Beginning in 2007, Ford Mustangs and other vehicles rolled off the production line with soy foam in the seats.  New uses in the automotive and equipment industry followed, including lubricants, body parts, interiors and seating.

1.3 Composition Of Soybeans

A study by Ruth Ogbemudia at University of Benin revealed that there is low moisture content of 8.07% implies that it can be stored for a very long time since moisture which is an important medium for multiplication of microorganisms is very low in the flour sample. The ash content 4.29% is indicative that the flour sample could be important sources of minerals. The high protein content 37.69% of the sample suggests that it could be used in the management of protein deficiency cases such as Kwashiorkor. This means the sample could be used in improving the palatability of foods in which they are incorporated. The high crude fat content of 28.2% suggests that soya bean may be a viable source of oil, going by their crude fat contents. Most legumes contain 1.5% crude fat. Soya bean crude fat is very high compared to most legumes because it is an oilseed. The sample contained 5.44% fibre though relatively low, but the presence of fibre in foods is known to be beneficial. Fibre has some physiological effects in the gastrointestinal, tract. These effects include variation in faecal water, faecal bulk and transit time and elimination of bile acids and neutral steroids which lower the body cholesterol pool. The high carbohydrate contents16.31% of the sample suggests that the flour sample could be used in managing protein-energy malnutrition since there is enough quantity of carbohydrate to derive energy from in order to spare protein so that protein can be used for its primary function of building the body and repairing worn out tissues rather than as a source of energy.

1.4 Nutritional Quality Of Soybeans

The high calcium content of 300.36 mg/100 g suggests that the flour sample could be used in complementary foods to help build the bones and teeth since calcium is one of the main components of teeth and bones. Calcium also plays a role in blood clotting . Magnesium is involved in making proteins and releasing energy and helps hold calcium in the enamel of the teeth. Iron is used in the management of iron deficiency anemia since iron is a vital part of red blood cells that carry and release oxygen. Phosphorus is closely linked with calcium. The two minerals combine to form calcium phosphate, which gives bones their rigid structure. Sodium is needed in the body in a small amount to help maintain normal blood pressure and normal function of muscles and nerves. Zinc helps the immune system fight off invading bacteria and viruses. The body needs zinc to make proteins and DNA, the genetic material in all cells and also helps in wound healing and the breakdown of carbohydrates. Also, zinc is below the permissible level of 50 and 100mcg/g in grains and beans. Cadmium was not detected in the soya bean flour sample.

1.5 Antinutritional Factors

The ANFs present in the raw and processed soybean are protease inhibitors 45-60 mg/g CP and 4-8 mg/g CP; Lectins 50-200 mg/g and 50-200 mg/g; Glycinin 150-200 mg/g and 40-70 mg/g; β-conglycin 50-100 mg/g and 10-40 mg/g; Saponins 0.5% and 0.6%; Oligosaccharides 14% and 15%; Phytic acid 0.6% and 0.6% (Van Eys et al., 2004).

1.6 Trypsin Inhibitors:

Trypsin inhibitors are Kunitz factor and Bowman-Birk factor (Winiarska-Mieczan, 2007) found in raw soybeans that inhibit protease enzymes in the digestive tract. They reduce trypsin activity (a protease enzyme secreted by the pancreas) and, to a lesser extent, chymotrypsin (Norton 1991), and, therefore, impair protein digestion by monogastric animals and some young ruminant animals (Leiner, 1994).

Feeding raw soybeans to monogastric animals like poultry and swine is not recommended as the presence of trypsin inhibitors and lectins will result in stunted growth, reduced feed efficiency and pancreatic hypertrophy (Leiner, 1994). Plant breeders have successfully developed lines of soybeans that are devoid of Kunitz inhibitors. This has reduced the amount of processing required to treat this type of soybean (Liener and Tomlinson, 1981). Eliminating the Bowman-Birk inhibitors from soybeans has proven to be more difficult (Livingstone et al., 2007) but progress is being made and commercial varieties devoid of trypsin inhibitors will likely be developed in the future. Trypsin inhibitors are sensitive to denaturation by heat treatment. The vast majority of soybean products used for livestock feeds are heat-treated in order to eliminate any anti-nutritional effects associated with feeding raw soybeans.

The activity of these inhibitors in soybean products may be decrease by toasted or heated processes. The right warming up of soybean and its products eliminate above 90% of antitrypsin activity. The animals of several species differently react on trypsin inhibitors in feeds. Goslings and chickens are more sensitive on the present trypsin inhibitors than piglets and calves. There are a new cultivars of soybean in which the level of trypsin inhibitors were reduced to 10mg/kg of seeds (Kulasek et al., 1995). 

Lectins:

 Lectins are glycoproteins capable to agglutinate erythrocytes and bind sugar components.  Lectins are not broken down in the gut, attach to mucosa cells damaging the intestinal wall and reducing the absorption of nutrients (Pusztai, 1991). 

Lectins are heat sensitive and are therefore only present at residual levels in soybean products. Heat treatment to inactivate antinutritional factors in soy products is less efficient for antigen than for trypsin inhibitors or lectins (Van Eys et al., 2004). The level of soy lectins can be estimated by measuring the hemagglutination activity. 

Goitrogenic factors: 

These, similarly, are glycosides belonging to the isoflavinic group, some of which like genistin; have goitrogenic activity resulting in enlargement of the thyroid gland and a reduction in the activity of thyroxine secreted by the thyroid itself.

1.8 Soyabeans Saponins:                                                                                                                            

Although they appear in low levels they can decrease feed palatability.

Rachitogenic factors: 

These factors are associated principally with genistin (about 0.10% of raw soybeans) which interfere with calcification of bone. Turkeys are particularly sensitive.

Phytic acid: 

Phytic acid complexes with certain minerals - such as calcium, phosphorus, magnesium, copper, iron and zinc - reducing their bioavailability. Levels of phytate in soybeans range from 1.0 - 2.3 percent. 

Phytates and oligosaccharides are not destroyed by the heat treatment.

Antigens:

The two most important antigenic proteins in soybean are glycinin and β-conglycinin. The level of glycinin and β-conglycinin can be measured by a specific competitive inhibition ELISA using anti-soy globulin (Heppell et al., 1987).

1.9 Protein Quality Of Soyabeans

Protein quality is a function of the amino acid profile and the proportion of each amino acid that is available to the animal. When soybean meals are intended for monogastric feeding it is well known that proper heat processing has a dramatic positive effect on amino acid digestibility, consequence of the destruction of anti-nutritional factors. However, overheating can result in a decrease in both concentration and digestibility of several amino acids, especially lysine. The reduction in digestibility is due to the Maillard reaction which binds free amino acids to free carbonyl groups (i.e., from carbohydrates). The Maillard reaction-end products are not bio-available for all livestock species.

Several methods used to determine protein quality of soybean products for monogastric species are urease index, KOH protein solubility, protein dispersability index (PDI) and nitrogen solubility index (NSI).

Urease Index:

The primary purpose of the urease assay is to determine if soybean meal has been sufficiently heated to destroy most of the anti-nutritional factors. Urease index values of 0.05 to 0.2 pH rise are considered for properly processed soybean meal (Dudley-Cash, 1999). Values above 0.2 indicated under-heating and values below 0.05 indicated over-heating. But it is not useful to determine excessive heat treatment.

KOH protein solubility:

Raw soybean and well heat processed soybean products should have a protein solubility around 90%. KOH solubility is a good index for determining over processing of soybean meal, but it is not a sensitive index for monitoring under processing of soybean meal.

Protein dispersability index (PDI):

Determination of PDI is the best method of evaluating soybean for both under heating and overheating. The PDI method measures the amount of soy protein dispersed in water after blending a sample with water in a high-speed blender. 

Nitrogen Solubility Index (NSI):

 The water solubility of soybean protein can also be measured with a technique called Nitrogen Solubility Index. 

 The two methods differ in the speed and vigor at which the water containing the soybean product is stirred. In animal nutrition the PDI method is used.

1.10 Aims And Objectives

Therefore, the objective of the study was to evaluate the nutritional and sensory characteristics of soybean and tigernut based infant food.

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