CHAPTER ONE
1.0 INTRODUCTION
1.1 Background of Study
Starch is a substance found in abundance in nature. Starch exists in powdered form, which does not dissolve in cold water or alcohol (Bemiller and Whistler, 2009). Kavlani et al., (2012) reported starch as a biodegradable, economical and a rich polysaccharide molecule which occurs in nature. Starch or ‘amyla’ is a polysaccharide carbohydrate which made up of greater amount of glucose units joined together by glycosidic bonds (Abbas et al., 2010). Starch contains two types of molecules; the linear and helical amylose and branched amylopectin. Starch generally contains 20-25 % amylose and 75-80 % amylopectin depending on the type of plant, (Ihekoronye and Ngoddy, 1985; Gotlieb and Capelle, 2005). Starch is produced by all green plants as an energy store and in humans, as an important energy source. Starches are found in various food sources such as potatoes, wheat, rice, yam, cocoyam, cassava and other foods with varied appearance based on their sources. Starch is a carbohydrate that has high functionality in unmodified state and highly reactive causing them to be modified physically, chemically or enzymatically to meet precise needs.
Starch could be prepared in native form. These raw or native starches produced retain their original structure and characteristics and are called “native starches” (Madu et al., 2011). There are unmodified forms of starch. Starch in the unmodified form has limited use in the food industry and other non-food industries due to their weak-bodied, cohesive properties (Ihekoronye and Ngoddy, 1985; Nyerhovwo, 2004; Steve, 2011). Starch form rubbery pastes when heated and undesirable gels when the pastes are cooled, with weak hydration, swelling and structural organization. Starch impacts a high viscosity; native starch cannot be used at much more than 6 % solids. This makes manufacturers generally opt for starches with better behavioral characteristic than those gotten from native starches. The properties of starches can be improved by applying various modification methods. Starches undergo modification so as to change the properties of unmodified or native starch and chemical modifications on starches have markedly altered their physicochemical and functional properties compared with their native forms (Rusli et al., 2004).
Starch has many applications in various industries. For example, starch is used in the manufacture of paper and paper products, in manufacturing of drugs in pharmaceuticals industries, and also used in textile industries, beverages and other industrial products (Agbo and Odo, 2010; Uzoma and Ibe, 2011). Starch can be applied in several functional areas like adhesion, antistaling, binding, clouding, dusting, emulsion stabilization, encapsulation, flowing aid, foam strengthening, gelling, glazing, moisture retention, molding, shaping, stabilizing and thickening (Bemiller and Whistler, 2009). Starch is used in the production of puddings, cake, candy, ice cream, popular beverages, both alcoholic and non-alcoholic and preparation of soups, sauces and meat products.
Mucuna slonei (Ukpo) is found in the tropical and sub-tropical areas of the world. ‘Ukpo’, belongs to the family leguminosae and sub-family caesalpiniacea. Ukpo is a climbing wooden vine that twines through the rain forest trees likes botanical boa constrictors (Ukachukwu, 2000). The seed pods of ‘Ukpo’ are covered with dense whiskers- like hairs called trichomes, which can be very painful when they come in contact with the skin. This serves as a protection from predators (Ukachukwu, 2000). Legumes are functional foods that promote good health and have therapeutic properties. They are important ingredients of a balanced human diet in many parts of the world due to their high protein and starch contents. In Nigeria, there are legumes that are not really recognized and have remained unexplored and underutilized (Arinathan et al., 2003). They include those that are eaten as legumes (Pigeon peas; Cajanus cajan, Bambara groundnut; Voandzeia subterranean) and those used as thickeners, stabilizers or processed as condiments (Akparata; Afzelia africana, Achi; Brachystegia eurycoma a, Ukpo; Mucuna sloanei, etc.).
Mucuna sloanei (Ukpo) is a food thickener originated from Asia and came to the western hemisphere through Mauritus (Nkpa, 2004). The local names of Mucuna sloanei in various dialets include ‘ukpo’ in Ibo, ‘yerepe’ in Yoruba and ‘karasau’ in the Hausa (Ayozie, 2010). The other species of Mucuna throughout the tropical regions of the world includes Mucuna Urensi; Mucuna pruries; and Mucuna veracruz (Ezeoke, 2010). Ukpo have been found to be used as flours in most states in Nigeria including Imo, Anambra, Akwa- Ibom and Ondo States. The seed is processed into flour and are used as thickeners, emulsifiers and flavouring agents in traditional soups for eating ‘garri’, pounded yam or cocoyam and cassava ‘fufu’ due to the high level of their gum contents. Ukpo is nutritionally important and is an economic source of protein, carbohydrate, calories as well as certain vitamins and minerals. These nutrients are essential to human health and nutrition. Mucuna sloanei (Ukpo) contains between 6-19 % crude protein; 39.8 - 61.49 % carbohydrates; 1.84- 5.9 % fat and 11.24-17.10 % vitamins (Ene – bong, 1992; Ajayi et al., 2006).
1.2 Statement of problem
Long before now, Mucuna sloanei (Ukpo) was effectively used as soup thickeners in native areas of South-East and South-South region of Nigeria. However, the use of Mucuna sloanei (Ukpo) had declined and other soup thickeners have replaced Mucuna sloanei (Ukpo) in various applications. This had led to lower demand of Mucuna sloanei in various industries. Ever since then this reduced demand has caused many farmers and market traders to lose interest in the agriculture of Mucuna sloanei. Mucuna sloanei gives a distinctive dark colouration when wet milling and during its use in the preparation of food. This has also been the reason for its neglect over the years therefore making Mucuna sloanei an underutilized crop in this age and time.
There is need to explore several new techniques of processing and applying this underutilized crop in the food industry as a source of food supply to this increasing population and the world at large. This will bring more awareness for use to the food crop and also help save the crop from going into extinction.
Justification of the study
Mucuna sloanei cultivation is fast going into extinction as a result of lack of utilization in most homes and industries in Nigeria. Over the years, industries have found replacement to Mucuna sloanei which has resulted in reduction in their usage ever since then. The lack of competitive market access for this crop have been a major disadvantage to their contribution to agricultural development which is as a result of less attentiveness to researches of these starches and the competitive nature of starch in food industries and other industries at large. The production of starches that has the same properties as those used in the industries will give way for its utilization and increase in cultivation by farmers.
Successful production of starch will help to meet both local and international demands by means of exportation beyond the shores of Nigeria. This will in turn create employment opportunities and generate revenue for Nigeria. The application of this starch depends largely on its properties and so improving the need of Mucuna sloanei seed as domestic food crop to industrial use justifies this study.
1.4 Aim of the study
The aim of this study is to isolate starch from Mucuna sloanei (Ukpo) seed, evaluate functional, physicochemical, pasting properties and produce new products for the purpose of food diversification
1.5 Objectives of the study
To isolate starch from Mucuna sloanei (Ukpo) seeds and test for their application in composite cookies production.
To determine the proximate composition of Mucuna sloanei (Ukpo) starch.
To determine the amylose and amylopectin content of Mucuna sloanei (Ukpo) starch.
To evaluate the physicochemical and pasting properties of Mucuna sloanei (Ukpo) starch.
