Bambara Groundnut – Effect Of Packaging Material And Oil Type On Sensory Properties And Microbial Stability
Bambara Groundnut – Effect Of Packaging Material And Oil Type On Sensory Properties And Microbial Stability
Bambara groundnut (Vigna subterranea), is one of the indigenous African crops currently receiving interest from researchers, because of its high yield and resistance to diseases (Hepper, 1970; Akande et al., 2009), as well as its adaptability to poor soils and rainfall. To place an order for the Complete Project Material, pay N5,000 to Then text the name of the Project topic, email address and your names to 08060565721.
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Then text the name of the Project topic, email address and your names to 08060565721.In Africa, it is the third eaten legume after groundnut (Arachis hypogea) and cowpea (Vigna unguiculata) (Omoikhoje, 2008). It serves as an important source of protein in the diets of a large percentage of the population, particularly to the poorer people, who cannot afford expensive animal protein (Bamishaiye et al., 2011). Bambara groundnut makes a balanced food, as it contains sufficient quantities of carbohydrates (65%), protein (16.25%) and fats (6.3%), with relatively high proportions of lysine and methionine (Brough and Azam-Ali, 1992; Omoikhoje, 2008).
Nigeria produced over 100,000 metric tonnes (Ashiedu, 1989; Olapade and Adetuyi, 2007), but Bambara groundnut is still one of the lesser utilized legumes in Nigeria (Alozie et al ., 2009). It has not been adequately exploited as human food because of constraints like hard to cook phenomenon, strong beany flavour, and presence of anti-nutrients and poor dehulling and milling characteristics (Enwere and Hung, 1996; Alozie et al., 2009). The freshly harvested pods are consumed cooked, shelled and eaten as a vegetable snack, while dry seeds are either roasted and eaten as snack in a manner similar to peanut when boiled (Alobo, 1999; Bamishaiye et al., 2011). The form in which the bambara groundnut seed is commonly consumed is Opka (bambara groundnut paste) (Enwere, 1998; Onyimonyi and Okeke, 2007). Okpa is well cherished food in the eastern part of Nigeria (Adumanya et al., 2012). The product is prepared after the seeds have been dehulled, milled into flour and then mixed with palm oil or crude palm fruit extract, water, salt, pepper and other spices. The paste is wrapped with banana leaves, transparent polyethene pack, tin and plastic containers, before steaming to form the product Okpa (Enwere, 1998).
In modern age, food packaging has become very important because of protection of product from contamination by macro and micro-organisms and their filth, prevention from loss or gain of moisture, shielding the product from Oxygen, and to facilitate handling (Ball, 1960; Butt et al., 2004). This places a high demand on selecting materials that provide the needed properties to maintain the quality of Opka, as faulty packaging can lead to quick deterioration of food (Okaka and Okaka, 2001). Moreover, the packaging type is known to affect the organoleptic properties of food, as a material such as low density polyethylene is a good water barrier but will scalp certain flavour and aroma compounds from foods (Cooksey, 2004). Thus, packaging material may also affect the organoleptic properties of Okpa. Also, the use of palm oil and crude palm fruit extract in Okpa preparation is common practice, but the effect of these oil types on the sensory properties of Okpa has not been documented. Therefore, the essence of this work was to investigate the effect of different packaging materials and oil type on the sensory properties and storage stability of bambara groundnut paste (Okpa).
The general objective of this study was;
To determine the effect of packaging material such as aluminium foil, nylon and uma leave or nylon and oil type on the sensory properties of bambara groundnut paste (Okpa).
The specific objectives were;
1. To determine the effect of packaging materials such as aluminum foil, nylon and uma leave or nylon on sensory properties of the product.
2. To determine the effect of oil source on the sensory properties of Okpa.
3. To establish the optimum packaging material and oil type for the production of Okpa.
4. To study the storage stability of the bambara groundnut paste (Okpa) produced and packaged in different materials.
LITERATURE REVIEW ON BAMBARA GROUNDNUT
Bambara groundnut (Vigna subterranea) is a tropical pulse (with underground pods), and is one of the legumes of papillionaceae sub family. It is a small herb with trifoliate leaves, which are palatable to domestic animals. The crop is indigenous to the tropical Africa (Kay, 1979; Olapade and Adetuyi, 2007). It originated in the Sahelian region of present day West Africa, from the Bambara tribe near Timbuktu, who now live mainly in central Mali (Nwanna et al., 2005), hence its name Bambara groundnut. The nuts are also known as Jugo beans (South Africa), Ntoyo Cibemba (Republic of Zambia), Gurjiya or Kwaruru (Hausa, Nigeria) Okpa (Igbo Nigeria), Epa-wro (Yoruba, Nigeria) and Nyimo beans (Zimbabwe).
In many regions of Africa, Bambara groungunt is the third most important legume after groundnut and cowpea. Of the total annual production of around 330,000 tonnes, approximately half is produced in West Africa (Coudert, 1984; Bamishaiye et al., 2011). Bambara groundnut is given less value and less priority in land allocation, because it is usually grown by women. Between 10-40% of the harvest is sold, the rest is consumed by the rural farmers themselves. Due to its low status, it is seen as snack or food supplement but not a lucrative cash crop (Sellschop, 1962; Doku and Karikari, 1970; Rachie and Silvestre, 1977; Linnemann, 1992). It can produce high yield levels with low input and is an ideal crop for farmers. It was found that about 98% of farmers in Swaziland regard Bambara groundnuts as a profitable crop (Sesay et al., 1999; Begemann et al., 2002) regarded as drought tolerant (Linnemann and Azam-Ali, 1993). Its drought tolerance is as a result of osmotic adjustment and low water loss through stomatal closure (Collinson et al; 1997). Bambara groundnut appear to reduce water loss under water stress and have the ability to recover from the effects of water stress after rainfall or irrigation (Vurayai et al., 2011). The seed of bambara groundnut is hard, smooth, usually round and varying in size up to about 1.5cm in diameter (Kay, 1979). It can also vary in colour from white, cream, dark brown, red or black and may be speckled or patterned with combinations of these colours (Adumanya et al., 2012). Bambara groundnut is a promising commodity, which needs more publicity, both as a crop and as a food.
2.1.1. VARIETIES AND CULTIVARS OF BAMBARA GROUNDNUT
According to Directorate plant production (2011), there are seven varieties of bambara groundnut, and these include;
• Black: Early maturing, usually small to medium sized kernels, mainly one seeded.
• Red: Late maturing, kernels are large. A good yielder, however it is prone to rotting onsite.
• Cream/black eye: A large kernel and a good yielder.
• Cream/brown eye: A large moderate kernel and a good yielder.
• Cream/no eye: very small pods and kernels. It mainly produces one seed and yields are lower.
• Speckled/flecked/spotted: purple colour predominates. Kernels are small, and pods are mainly one-seeded.
• Brown: contains variation between light and dark brown. Kernels are of medium to large size.
2.1.2 NUTRITIONAL COMPOSITION OF BAMBARA GROUNDNUT
Bambara groundnut can be used and does play an important role as a protein source. The seeds make a complete food as it contains sufficient quantities of protein, carbohydrates and fats. On the average, the seeds contain 54.5-69.3% carbohydrates, 17-24% protein and 5.3-7.8% fat, and gives 367-414 calories per 100kg (Caroline, 2000). The gross energy value of bambara groundnut seed is greater than that of other common pusles such as cowpea, lentil and pigeon pea (FAO, 1982). Ihekoronye and Ngoddy (1985), reported that it is richer than groundnut in essential amino acids such as isoleucine, leucine, lysine, methionine, phenylalanine, threonine and valine. The bean is an important source of food security, because it is highly nutritious, and is a good source of fibre, Calcium and Iron as indicated in Table 1. Calcium is important for blood clotting. It has been reported that the red seeds are useful in areas where Iron deficiency is a problem, as they contain almost twice as much as the cream seeds (Caroline, 2000). Iron is reported also to be very important in the functioning of the central nervous system (Vyas and Chandra, 1999; Adeyeye and Fagbohun, 2005). The crop contains about only 6% ether extract, therefore could not give a cash crop status, a great importance in food industry (Bamishaiye et al., 2011). The fatty acid composition of bambara groundnut oil is shown in Table 2, this indicates that the free fatty acid for bambara seed oil is suitable for edible purposes. Table 3, compares bambara seeds with other legumes as regards the nutrient content (FAO, 1982). The carbohydrate fraction of bambara groundnuts, is predominantly composed of starch and non-starch polysaccharides, with lesser amount of reducing and non-reducing sugar (Bamishaiye et al., 2011). Bambara groundnut also contains the vitamins thiamine, riboflavin, niacin and carotene, but it is very low in ascorbic acid (Oyenuga, 1968; Abdulsalami and Sheriff, 2010).
Table 1: Minerals Composition of Raw Bambara groundnut (mg/100g)nut.
Minerals Values Obtained
Source:(Abdulsami and Sheriff, 2010)
Table 2: Fatty acid composition of bambara groundnut oil.
Fatty Acid Content %
Source: (Kay, 1979)
Table 3: Energy and selected nutrients in legumes composition per 100g edible portion of dried mature whole seeds.
Nutrition% Bambara groundnut Cowpea Groundnut Jack bean Soybean
Moisture 10.1 11.5 7.3 11.2 10.2
Energy 370 340 548 348 400
Protein 16.0 22.7 25.4 21.0 35.1
Fat 6.0 1.6 45.3 3.2 17.7
Carbohydrate 65 61 21.6 61 32
Crude fibre N.D 4.2 2.1 7.6 4.2
Dietary fibre N.D. N.D 6.1 N.D. 11.9
Ash 3.0 3.0 2.4 3.6 5.0
Calcium 85 180 58 134 226
Iron (mg) 4.2 22 2.2 8.6 8.5
Nicotinic N.D. 1.5 16.8 3.1 2.2
Source: (FAO, 1982)
2.1.3 FUNCTIONAL PROPERTIES OF SOME LEGUMES
The functional properties of food are defined as those physico-chemical characteristics of food components, that determine the usefulness and successes of ingredients in food systems. Kinsella (1980), reported that the functional properties of foods can be used to define how such foods can be supplemented into existing foods and how they can replace more expensive protein in traditional foods. According to Ikegwu et al., (2009), functionality can be defined as any property of a food or food ingredient other than the nutritional ones that affects its utilization. Seed proteins should also possess the essential requisite functional properties for successful utilization in various food products. These functional properties are intrinsic physico-chemical characteristics, which affect the behaviour of properties in food systems during processing, manufacturing, storage and preparation (Eltayeb et al., 2011). The functionality of plant protein has been reported to be dependent upon the chemical characteristics influence on the functional properties of proteins, these include; moisture, temperature, pH, salt concentration, enzymes, or addition of ingredients (Johnson, 1970; Aremu et al., 2008).
Table: functional properties of jack bean, pigeon pea and cowpea seed flours found in Nigeria.
Parameter Jack bean Pigeon pea Cowpea
Capacity (%) 113.50+0.29b 148.17+0.35b
Water Absorption capacity (%) 128.29+0.50b 189.77+0.28a 188.20+0.09a
Foam capacity (%) 20.67+0.41a 3.53+0.36c 16.33+0.37a
Emulsion capacity (%) 71.73+0.44a 28.73+0.12c 46.40+0.22b
Least Gelation Concentration (%) 4.00+0.10b 6.00+0.10a 4.00+0.30b
Foam stability after 2hours (%) 10.33+0.41b 3.05+0.10c 415.70+0.31a
Emulsion stability after 24hours (%) 13.19+0.10b 13.93+0.18ab 15.20+0370a
Sources: (Arawande and Borokini, 2010)
2.1.4 ANTI-NUTRITIONAL COMPONENTS OF BAMBARA GROUNDUNT
Low levels of trypsin inhibitor and phenolic compounds have been identified in bambara groundnut seed (Poulter, 1981; Brough et al., 1993). The trypsin inhibitor is inactivated by autoclvaing but was discovered that substantial proportion of the trypsin inhibitor remained after heat treatment; total activity was reduced with presence of heat stable (tannin) and heat liable protein factor. Tannin is located mainly in the seed coat and their concentration is correlated with seed colour as it is in common beans. Poulter (1981) reported that the highest level of tannin was found in bambara groundnut accession with brown, red seed and lower tannin level accession with cream coloured seed. Tannin can be deleterious to livestock performances, though they also have interesting nutritional properties in some cases (by-pass protein in ruminants, anthelminthic effect). Bambara groundnut is reported to have anti-trypsin variety (landrace) (Tibe et al., 2007). Phytates are found in high proportions in bambara groundnut and are known to reduce cations availability (Calcium particularly) (Nwanna et al., 2005).
2.1.5 PROCESSING AND UTILIZATION OF BAMBARA GROUNDNUT
Bambara groundnut is grown mainly for its edible and nutritionally rich seeds. The dried seeds are sometimes roasted, and ground into fine flour or eaten whole in the young fresh state (Oyenuga, 1968). The method of processing bambara groundnut is similar to the method of processing other legumes, but usually, its processing involves dry milling.
Processing of bambara groundnut starts with cleaning of the seeds. They are manually or mechanically cracked and the seed coats that detach themselves from the cotyledons are winnowed off. The cotyledons are further ground into flour, sieved and the residue after sieving is used as animal feed (Onyimonyi and Okeke, 2007), or in the preparation of Okpa.
Alternatively, the seeds are soaked in water over night and at the end of soaking, the seed coats are removed manually. The seeds are often spread under the sun to reduce moisture content to about 8-10% before milling. The flour can then be mixed with palm oil, salt and pepper to obtain slurry, and other ingredients like crayfish, onions, uziza seeds may be added if desired, until consistency is achieved. The mixture is then wrapped in banana or plantain leaves, transparent polyethene pack or containers, steamed for 50minutes to 1hour (Enwere, 1998). The end product is “Okpa” (bambara groundnut paste). Okpa is relished by adolescents and adults. It is hawked by women and children, who prepared it to secondary schools’ refectories, where it is used as part of breakfast (Enwere and Hung, 1996). According to Ominawo et al., (2007), Okpa is a better diet for the diabetics than moin-moin, as they were found to have lower values of glycemic index and blood glucose response when Okpa was administered and this may be attributed to the higher crude fiber content of bambara nut than cowpea (moin-moin) (Onimawo, 1998). In many West African countries, the fresh pods are boiled with salt and pepper and eaten as a snack. In East Africa, the beans are roasted, then pulverized and used to make soup, with or without condiments. Zengeni and Mupamba (1995) reported that ripe dry seeds of bambara groundnut are roasted, broken into pieces, boiled, crushed and eaten as a relish with sazda. (maize meal porridge). In restaurants in Angola and Mozambique, boiled salted seeds are often served as appetizers (Akande et al., 2009).
Recently, a trial of bambara groundnut milk was carried out and its flavour and composition were found to be high to milks produced from cowpea, pigeon pea and soyabean (Obizoba and Egbuna, 1992). Bambara groundnut milk ranked first, while all other milks were found to be acceptable. It has been reported also in Zambia, that bambara groundnut is used for bread making (Brough et al., 1993). Commercial canning of bambara groundnut as gravy is a successful industry in Ghana (Swanevelder, 1998), the product was thus available throughout the year and over 40,000 cans of various sizes were produced annually (Doku and Karikari, 1971; Begemann, 1986; Akande et al., 2009). Bambara groundnut could also be used as composite flour, used for cereal based confectionaries like biscuit/cakes, bread (Addo and Oyeleke, 1986; Bamishaiye et al., 2011), where low calories and high fibre diet or foods is desirable. The use of bambara groundnut flour to supplement wheat flour was acceptable especially those from 80:20 Wheat flour: bambara groundnut flour blend (Alozie et al., 2009). Baby food such as pap can be fortified with bambara groundnut to improve its nutrient content (Fabiyi, E.F. personal communication; Akande et al., 2009). Meat analogue, a major type of texturized plant protein (TPP), which is extensively imitated meat product (Sheard et al., 1984) has been produced from bambara groundnut flour and this was observed to have desirable sensory properties.
Texturized plant protein is an excellent meat substitute in many dishes and they approximate the aesthetic qualities (primarily texture, flavour and appearance), and low chemical characteristics of specific types of meat. Thus, bambara groundnut can be used quite freely to replace the high priced lumps of meat for adequate nutrition (Okonkwo and Okpara, 2010).
According to Karikari (1971), some tribes in Congo roasted the seeds of bambara groundnut and pounded them for oil extraction, despite the relatively low oil content of the seed. Bambara groundnut can also be fermented. A known dawadawa type product is made from bambara groundnut using a solid substrate fermentation method (Barimalaa et al., 1994). Bambara groundnut has long been used as an animal feed. Several workers have successfully fed processed bambara groundnut to livestock animals such as poultry. (Oluyemi et al., 1976; Onwudike and Eguakun, 1994; Arijeniwa and Omoikhoje, 2004) and rabbits (Joseph et al., 2000; Akande, 2009) as well as pigs, where inclusion of 10% bambara wastes in the diets of weaner pigs will help produce cheaper and affordable pork (Onyimonyi and Okeke, 2007). The haulms were found to be palatable (Doku and Karikari, 1971), and the leaves were reported to be rich in Nitrogen and Phosphorus, and therefore suitable for livestock grazing (Rassel, 1960; Akande et al., 2009).
The extract from the nut, particularly the protein extracts can be used directly in cosmetic formulations and provides specific and notable effects (Bamishaiye et al., 2011). Bambara groundnut could be used for other purposes as curing nausea suffered by pregnant women by chewing and swallowing raw bean (Directorate plant production, 2011). The leaves are pounded with those of Lantana trifoliate or Mexican marigold, water is then added to make a solution which is used to wash livestock as a preventive against ticks as an inseciticide. Water from boiled maize and pulse mixture is drunk to treat diarrhoea (Bamishaiye et al., 2011).
2.1.6 FOOD PACKAGING
Packaging is the protection of materials by means of containers designed to isolate the contents, to some predetermined degree, from outside influences (Brennan and Day, 2006). In this way, the product is contained in a suitable environment within the package. The qualification to some predetermined degree is included in the definition as it is not always desirable to completely isolate the contents from the external environment. Packaging may be regarded as a preservation method in its own right or just an important adjunct to other methods of food preservation. Even though packaging may perform functions other than preservation, its most important role is to deliver to consumers fresh and manufactured foods of the expected quality.
Good packaging actually serves two purposes, which are essentially technical and presentational. Technical aspects in packaging is to extend the self life of the food by better protection from all hazards during storage. Presentational aspects are not concerned with shelf life but such packaging increases sales, by creating a brand image that the buyer instantly recognizes (Peter and Axtel, 1993; Butt et al., 2004).
2.1.7 OBJECTIVES OF PACKAGING FOODS
According to Akobundu (1996), foods are packaged, among other functions, to;
1. Prevent spillage and contamination (Physical, chemical, microbial).
2. Protect against chemical and physical change.
3. Ensure safer and easier transportation and
4. Above all, maintain consumer confidence. The packaging also identifies its content as to the manufacturer, type and quality, attracts or persuades buyers, ensures easy dispensation, and may provide nutritional and usage information.
2.1.8 FACTORS AFFECTING THE CHOICE OF A PACKAGING MATERIAL
126.96.36.199 MECHANICAL DAMAGE
Fresh, processed and manufactured foods are susceptible to mechanical damage. The bruising of soft fruits, the break up of heat processed vegetables and the cracking of biscuits are examples. Such damage may result from sudden impacts or shocks during handling and transport, vibration during transport by road, rail and air and compression loads imposed when packaging are stacked in warehouses or large transport vehicles. Appropriate packaging can reduce the incidence and extent of such mechanical damage (Brennan and Day, 2006).
188.8.131.52. PERMEABILITY CHARACTERISTICS
The rate of permeation of water vapour, gases (O2, CO2, N2 ethylene) and volatile odour compounds into or out of the package is an important consideration in the case of packaging films, laminates and coated papers. Foods with relatively high moisture contents tend to lose water to the atmosphere. This results in a loss of weight and degeneration in appearance and texture. Product with relatively low moisture contents will tend to pick up moisture, particularly when exposed to a high humidity atmosphere. According to Robertson (1993), permeability is the transfer of molecules from the product to the external environment, through package or from the external environment through the package, to the product. Thus, the permeability of the packaging material is one of the most critical features of the packaged for affecting the quality of the food product (Cooksey, 2004).
In the case of fatty foods, it is necessary to prevent egress of grease or oil to the outside of the package, where it would spoil its appearance and possibility interferes with the printing and decoration. Greaseproof and parchment papers may give adequate protection to dry fatty foods, such as chocolate and milk powder, while hydrophilic films or laminates are useful with wet foods such as meat or fish (Brennan and Day, 2006).
A package must be able to withstand the changes in temperature which it is likely to encounter, without any reduction in performance or undesirable change in appearance. This is of a particular importance when foods are heated or cooled in the package (Brennan and Day, 2006). For many decades, metal and glass containers were used for foods which were retorted in the package.
Many food components are sensitive to light, particularly at the blue and ultra-violet end of the spectrum. Vitamins may be destroyed, colours may fade and fats may develop rancidity when exposed to such light waves. For protection against light, pigmented wrappers and cartons perform adequately (Okaka and Okaka, 2001).
184.108.40.206 CHEMICAL COMPATIBILITY OF THE PACKAGING MATERIAL AND THE CONTENT OF THE PACKAGE
It is essential in food packaging that no health hazard to the consumer should arise as a result of toxic substances present in the packaging material, leaching into the contents. According to Robertson (1993), migration is the movement of molecules originally contained by the package, into the product. In the case of flexible packaging films, such substances may be residual monomers from the polymerization process or additives such as stabilizers, plasticizers, colouring materials. Other materials used for food packaging may result in undesirable chemicals migrating into foods. These include semi rigid and rigid plastic packaging materials, lacquers and sealing compounds used in metal cans, materials used in the closures for glass containers, additives and coatings applied to paper, board and regenerated cellulose films, wood, ceramics and textiles (Brennan and Day, 2006).
220.127.116.11 PROTECTION AGAINST MICROBIAL CONTAMINATION
Another role of the package may be to prevent or limit the contamination of the contents by micro-organisms from sources outside the package. This is most important in the case of foods that are heat sterilized in the package, where it is essential that post process contamination does not occur. The metal can has dominated this field for decades and still does. Some closures for glass containers are also effective barriers to contamination. Thus, food packaging is important for protection of product from contamination by micro-organisms and their filth (Butt et al., 2004).
Many packaging materials contain volatile compounds which give rise to characteristic odours. The content of a package may become tainted by absorption or solution of such compounds when in direct contact with the packaging materials. Food not in direct contact with the packaging material may absorb odour compounds present in the free space within the package. Paper, paper board and fibre board give off odours which may contaminate food (Brennan and Day, 2006). Printing solvents also have the capacity to migrate from the package into foods to cause off flavour (Halek and Levinson, 1988; Akobundu, 1996). Most polymers are relatively odour-free, but care must be taken in the selection of additives. Careful selection of such materials is necessary to lessen the risk of contamination of foods in this way (Ackermann et al., 1995; Akobundu, 1996).
2.1.9 INTERMEDIATE MOISTURE FOODS
Foods with improved microbial stability can be fabricated by reducing their water activity (aw). This parameter can be controlled by adjusting moisture content and by the presence of solutes (Torres, 1984). These products, called intermediate moisture foods (IMF’s) are microbiologically stable as long as aw<aw*
aw = aw (t, x, y, z)
= aw at any time (t) and any location (x, y, z,) within the intermediate moisture food.
aw* = Critical aw value
Above aw*, microbial growth is possible. Its value will depend upon parameters such as pH, concentration and type of preservative (s), expected microbial contamination (Torres, 1984). Therefore, intermediate moisture foods are semi-moist foods with about 25% (15-50%) moisture but with some of the water bound (and so unavailable to micro-organisms) by the addition of glycerol, sorbitol, salt or organic acids, so preventing the growth of micro-organisms. Water can exist in foods in various forms, as free water (tomato juice), as droplets of emulsified water (Butter), as water tied up in colloidal gels (jellies), as thin layer of adsorbed water (powder milk) or as chemically bound water of hydration (Sugar). While free and adsorbed water are easier to manipulate, some of the chemically bound water is extremely difficult to remove during drying (Okaka and Okaka, 2001). Water in food which is not bound to food molecules can support the growth of bacteria, yeasts and molds (Fungi). The term water activity (aw) refers to this unbound water. The value aw is thermodynamically defined as the ratio at a given temperature of the fugacity, f, of water in some given state, and its fugacity, if, in a state which for convenience, has been chosen as reference state (Reid, 1976; Torres, 1984).
Theoretical estimation of aw have included solutions theory based on the free energy model of Gibbs; theories about physical sorption if a surface can be distinguished (i.e. the structure formed by the common food polymers: proteins and carbohydrates): or a combination of both if the particular system requires so. Other models are the classifiable B.E.T. model and the empirical or semi-empirical Smith and Owine models (Iguedjtal et al., 2008). The GAB and BET equations predict the moisture content of the monolayer (xo) and are considered to be the most useful ones for determining the optimal moisture conditions for food stability during storage (Arslan and Togul; 2006). The term Xo is the amount of water (g water/g dry matter) that is strongly associated with all active sites of the adsorbent solid phase and its value is correlated to the stability of foods during storage (DYNA, 2011). The preservation and stabilization of a foods main properties during storage (example; its texture and microbiological stability) often require control of moisture content or water activity. Moisture content is an important criterion for judging food quality (Arslan and Togul, 2006) and water activity (aw) is an essential additional parameter for describing water availability and mobility in foods (Iguejtal et al., 2008). Establishing the relationship between equilibrium moisture content (EMC) and aw, also known as the sorption isotherm (adsorption or desorption) is important for understanding the stability of food stuffs (Labuzo and Hymann, 1998). The adsorption isotherm of a food describes the thermodynamic equilibrium state of water. It can be used to predict the shelf life of packaged moisture-sensitive products by modeling moisture uptake during food storage and distribution. It can also be used to determine the best storage methods, packaging materials, and ingredient selection (Lahsasni et al., 2004).
2.1.10 MICROBIOLOGICAL ASPECTS OF INTERMEDIATE MOISTURE FOODS
Intermediate moisture foods range in aw from 0.7 to 0.9 and in water content from 20 to 50% (Torres, 1984). These foods may be susceptible to mold growth, enzymatic degradation, or non enzymatic browning unless appropriate preventive measures are taken (Torres, 1984). Intermediate moisture food ingredients heat pretreatment was suggested to reduce microbial load. However, subsequent handling can cause contamination. Even though some products are cooked or pasteurized, slicing and packaging gives ample opportunity for recontamination and shelf life usually ends as a result of microbial growth . Another problem of surface contamination of intermediate moisture foods is that viable counts can be highly variable (Anderson et al., 1980; Torres, 1984).
2.1.11 PALM OIL
Palm oil is an edible plant oil and is derived from the mesocarp of the fruit of the oil palm (Elaies). The genus Elaies comprises two species, namely E. guineensis and E. oleifera, originating from West Africa, and the commercial planting material is mainly of this species.
Almost 90% of the world’s palm oil production is used as food. This has made demands that the nutritional properties of palm oil and its fractions be adequately demonstrated. The fatty acid composition of palm oil has thus, been the focus of attraction in determining its nutritional adequacy in relation to coronary heart disease (CHD) risk factors. Palmitic acid (44%) is the major saturated fatty acid in palm oil (Siew, 2000; Sambanthamurthi et al., 2000) and this is balanced by almost (39%) monounsaturated oleic acid sand 11% polyunsaturated linoleic acid, (5%) stearic acid and (1%) myristic acid. The minor components of interest in palm oil are vitamin E, caroteniods and an antioxidant-rich phenolic- flavoniod complex (Sambanthamurthi et al., 2000) recovered from the palm oil milling waste. The minor constituents can be divided into two groups. First groups consists of fatty acid derivatives such as partial glycerides (Monoglycerides, Diglycerides), phosphates, esters and sterols. The second group includes classes of compounds not related chemically to fatty acids. These are the hydrocarbons aliphatic alcohols, free sterols, tocopherols, pigments and trace metals.
The partial glycerides do not occur naturally in significant amounts except in palm oil from damaged fruits several minor nonglycerides are found in palm oil. They consist of sterols, triterpene alcohols, tocopherols, phospholipids, chlorophylls, caroteniods and volatile flavour components such as aldehydes and ketones. Tocopherols and tocotrienols are fat soluble vitamin E isomers and the major antioxidants of vegetable oils.
The pigmentation of palm fruits is related to their stage of maturity. Two classes of natural pigments occurring in crude palm oil are the caroteniods and the chlorophylls. Palm oil from young fruits contains more chlorophylls and less carotenoid than oil from mature or ripe fruits. The pigments in palm oil are involved in the mechanisms of autoixidation, photooxidation and antioxidation within the plant. Crude Palm oil has rich orange-red colour due to its high content of carotene (700-800 ppm), which are strictly polyene hydrocarbras, and a class of carotenoids. Carotenes account for 90% of the total carotenoids. Palm oil products are made using milling and reforming processes: first using fractionation, with crystallization and separation processes to obtain solid Stearin and liquid Olein fractions. Then melting and degumming removes impurities. Then the oil is filtered and bleached. Next, physical refining removes smells and colouration, to produce “refined bleached deodourized palm oil or RBDPO, and free sheer fatty acids which are used as raw materials in the manufacture of soaps, washing powder and other hygiene and personal care products.
Palm oil when consumed as part of a low fat diet (<30% energy) has been shown to be effective in maintaining desirable plasma cholesterol and lipoprotein cholesterol levels (Sundram, 1997). Monounsaturated oil rich in oleic acid are currently touted to be the healthiest of the edible fats in the human diet. While olive, rapeseed and canola have in excess of 60% of their fatty acid composition as cis-oleic acid, palm olein has about 48% of this monounsaturated acid. The question of whether their level of oleic acid in palm olein is adequate to result in a lipo-protein cholesterol profile that protects against coronary heart disease (CHD) was examined in a series of human trials. In these studies, the exchange between palm olein (rich in 16:0) and olive oil (rich 18:1) resulted in similar plasma and lipoprotein cholesterol values. This showed that in healthy normocholesterolaemic humans, palm olein could be exchanged for olive, canola and rapeseed oils (High oleic) without adversely affecting serum lipids and lipoprotein levels (Sundram, 1997). Thus palm olein apparently lacks cholerosterolemic effect.
2.1.12 CONSTRAINTS TO LEGUME UTILIZATION
Although legumes are rich in protein and carbohydrates, there are several factors that contributed to their under utilization. The main limitation includes their flatulence properties, prolonged cooking time, the presence of anti-nutritional factors and toxicity (Rachie, 1995). Dehuling has been a limiting factor in the preparation of flour from bambara that could produce acceptable moin-moin substitute, most especially with respect to the texture and flavour. The conventional method used always result into a product with very hard texture and strong beany flavour (Alobo, 1999).
Beany flavor is due to the action of enzymes, lipoxygenase on free fatty acid present in the seed, and it can be removed by inhibiting the activity of the enzymes . This can be done by boiling the seeds at ahigh temperature (75 – 850C), which results in denaturation of the enzymes lipoxygenase.
The complex sugar are soluble in water and if the legumes are pre-soaked for some hours and rinsed with water before cooking, the complex carbohydrates are usually washed away and flatulence is prevented (Kordylas, 1990).
The hard to cook phenomenon experienced in legumes especially after long storage periods is another major constraints to legume utilization. As the storage period of legumes increase, there is a tendency for the grain to develop hard to cook phenomenon (Sefa – Dedeh et al., 1979; Swanson et al., 1985). Thus, it takes longer time to cook legumes. With the current high cost of fuel (energy), this may constitute a great constraint to the utilization of legumes for food (Omoikhoje, 2008). Toxicity is any adverse physiological condition or response produced in a man or animal by a particular food or substance after consumption (Liener, 1977).Detoxification of most legumes can achieved the traditional methods of domestic preparation. However, proper care should be taken in legume preparation to ensure complete detoxification as some of these toxicants especially haemagglutinins are heat stable.
Anti – nutritional factors are substances that interfere with the normal digestion, absorption and utilization of food nutrients in the body systems of the human and animals. A number of these substances occur naturally especially in plant materials, mostly in legumes. Not withstanding the agronomic and nutritional advantages of legumes as a cheap protein source of many, especially low income persons, legumes have been reported to contain several anti-nutritional factors such as Beta-amino propioniriles, which casues lethism and haemolytic-debrile factor contained in legume like fava bean, which causes favism, goitrogenic factors and trypsin inhibitors.
Also, the lack of knowledge of the functional, chemical and nutritional properties of some legumes grown in developing countries is responsible for their less utilization in food formulations (Udensi et al., 1999).
Cream coloured variety of Bambara groundnut (Vigna subterranea), and all other ingredients required for the production of Okpa were purchased from Meat Market, Abakaliki, Ebonyi State, Nigeria.
3.2 BAMBARA GROUNDNUT FLOUR PRODUCTION
The bambara groundnut seeds were cleaned manually to remove all foreign materials, such dust, dirt, small branches and immature seeds. The selected seeds were cracked to detach the seed coats from the cotyledons, and winnowed off. The cotyledons were hammer milled, passed through a sieve to obtain fine flour.
Bambara groundnut flour
5.0 CONLUSION AND RECOMMENDATION
This study showed that Bambara groundnut flour has a high emulsification and oil absorption capacity, but low bulk density and water absorption capacity. The high emulsification and oil absorption capacities are needful for the stabilization of the oil/water emulsion, the colour, flavor and mouth-feel of Okpa, because of the generous amount of oil addition in its preparation. Okpa has a high content of moisture, ash, fat, protein and carbohydrate, and can serve as a balanced diet when consumed. The oil type used in its preparation has significant (P<0.05) effect on the sensory properties such as colour, aroma, texture and general acceptability. The packaging materials tested did not significantly affect neither sensory properties or the microbial quality of Okpa. However, obvious changes take place in Okpa quality while fresh and deterioration after 5days (120hrs) irrespective of the oil type and packaging material, when stored at ambient temperature.
1)It is recommended that bamabara groundnut flour should be more utilized in food formulations like soups and confectinary products where high emulsification and oil absorption capacities are needed.
2)It is also recommended that improper improper handling during post food preparation processes of Okpa should be avoided because recontamination can take place even through cooking is the last preparatory stage.
3)It is also recommended that Okpa is best consumed within a period of 5days from production during storage at ambient temperature, as it has many undesirable consequences after 5days both in its sensory and microbial quality.
Bambara Groundnut – Effect Of Packaging Material And Oil Type On Sensory Properties And Microbial Stability
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