1.0 INTRODUCTION
1.1 Background of the study / Statement of problem
In Nigeria, biscuit constitute a popular cereal food consumed by the young and the old due to its low cost compared with other processed foods, good nutritional quality and availability in different forms, varied taste and longer shelf-life (Hussein et al., 2011).They are ready to eat, convenient and inexpensive food products, containing digestive and dietary principles of vital importance (Kulkarni, 1997). Biscuits are made from wheat flour with the addition of other ingredients such as salt, fat, sugar, baking powder, milk, and flavouring agents (Oyewole et al., 1996). Neil (2002) reported that wheat (Triticum spp.) grain is a staple food used to make flour for leavened, flat and steamed breads, biscuits, cookies, cakes, breakfast cereal, pasta, noodles, and couscous and for fermentation to make beer, other alcoholic beverages. Biscuits are nutritive snacks produced from unpalatable dough that is transformed into appetizing product through the application of heat in the oven (Olaoye et al., 2007).
Biscuits are mostly produced from wheat flour (Ihekoronye and Ngoddy, 1985). However, Okpala and Okoli (2011) noted that, in many regions of the world, wheat flour is unavailable or uneconomical. Thus in such countries like Nigeria, they have to rely on importation of wheat flour to sustain the production of snacks or exclude wheat product from the diet. Studies revealed that, the demand for snacks and pastry product is on the increase and the cost of the products has become very expensive (Sanful and Darko, 2010).
Attempts have been made to produce flour from other cereals apart from wheat as well as composite flour from different food categories. Flour produced from cereals, legumes and tubers only will have a nutritional value inferior to those produced from a combination of cereals legumes or tubers (Barber et al, 2010). In selecting the components to be used in composite flour blends, the material should be readily available culturally acceptable and provide an increased nutritional potential (Akobundu et al 1998). The major or mandatory ingredients in bread making are flour, water and yeast (Osuji, 2006). The flour should have good amylase activity; the moisture content should be satisfactory (Giami et al., 2004). Milligan et al (1981) defined composite flour as a mixture of flours, starches and other ingredients intended to replace wheat flour totally or partially in bakery and pastry products. Aside the purpose of composite technology initiated by the (Food and Agriculture Organization in 1994) being to reduce cost of support for temperate countries by encouraging the use of indigenous crop such as yam, cassava, maize and others in partial in partial substitution of the wheat flour (Satin,1998), the FAO also reported that application of composite flour in various food product would be economically advantageous if the imports of wheat could be reduced or even eliminated, and that demand for bread and pastry product could be met by the use of domestically grown products instead of wheat (Jisha et al.,2008). The importance of various bakery products including biscuit in the current eating habits suggests that they can serve as vehicles for important nutritional components (Ivanovski, 2012). This has created a need for the development of nutritionally beneficial and functional foods (Angioloni and Collar, 2011), hence the use of yam flour and gum Arabic in preparing a nutritious yet acceptable biscuit. The use of non-wheat flours like water yam flour in making composite biscuit is constrained by a number of challenges. It has been reported as the composite biscuit level of substitution with other flours in wheat flour increased, biscuit quality progressively reduced (Yaseen et al., 2010; Conforti and Davis, 2006; Dhingra and Jood, 2004). The reduction in quality attributes has been attributed to gluten dilution which leads to reduction of flour strength and gas retention capacity (Muranga et al., 2010; which ultimately leads to reduced sensory appeal for most composite breads necessitating the use of bread improvers and dough strengtheners (Yaseen et al., 2010).
Gum Arabic has a high solubility in water i.e. up to 50%, forming a colourless, tasteless solution. In addition its interaction with other chemical compounds is minimal (Salif, 2008). Its viscous and adhesive properties are of importance in the bakery industry especially where non-wheat flours are used. This is because such bakery products require polymeric substances that mimic the viscoelastic properties of gluten in the dough (Toufeili et al., 1994). Gums have other important properties such as controlling the pasting properties of food and improving the moisture content. They also maintain overall product quality during storage (Mohamed, 2010). Hydrocolloids (Gum Arabic) have specifically found a wide application as additives in baked product manufacture. The functional effects of hydrocolloids stem from their ability to modify dough or batter rheology (handling) and keeping qualities of finished baked product (Shittu et al., 2009). They are often used as gluten substitutes in gluten-free bread (Toufeili et al., 1994). The replacement of wheat flour requires the development of an adequate substitute in terms of functionality, cost and availability. Attempts have been made to produce flour from other cereals apart from wheat as well as composite flour from different food categories.
Recently, the use of yam flour as evolved in the bakery world for cake and biscuits (Ukpabi, 2010). Wheat flour is lacking one some essential amino acids such as lysine, methionine and threonine (Ihekoronye and Ngoddy, 1985). The deficient nutrient can be supplemented through the use of composite flour. Gluten is present in only wheat flour; the use of yam flour reduces the textural of biscuit especially in biscuit type, where strength is dependent on some appropriate level of gluten development (Okaka and Anjekwu, 1980) flour and the cost of importation of wheat flour, led to the use of yam flour in the present study.
For many years Nigeria has been relying on importation of wheat and wheat flour for its bakery industry. Importation of wheat flour has led to high cost of production of baked products like Biscuits. Inadequate wheat is grown locally to meet the demand of industries that uses wheat in making baked foods. Water yam is abundantly produced in Nigeria, as a result unconsumed yam are lost due to lack of post-harvest storage facilities. Such importations have led to high production costs for baked products, resulting in skyrocketing retail prices of baked products making the majority of the rural communities unable to purchase such products. Past research has demonstrated that (Dioscorea alata) flour can be partially substituted for wheat flour in the baking of biscuits, bread and cookies. This offers great opportunity to reduce over reliance on wheat flour as the only raw material for biscuits, bread and cookie making, and also should reduce retail prices of baked products.
1.2 Aims and objectives of this research
1.3 Scope of study
The present study is limited to the production of biscuit from water yam (Dioscoreaalata) flour using gum Arabic as a binder or thickener and determination of its physicochemical analysis and sensory attributes. The study will be done in hopes of producing highly acceptable biscuit from wheat-water yam composite flour in which will be improved with gum Arabic.