Quality Evaluation Of Whole Wheat And Orange Flesh
Sweet Potatoes Composite Flour Blends Fortified With Soybean Flour
Chapter One
Introduction
1.1 Background of study
Bread is one of the most widely consumed food products in the world and the bread making technology is probably one of the oldest known technology (Selomulyo and 2hov, 2007). It is an important stable food in both developing and developed countries and constitutes one of the important sources of nutrients including carbohydrate, protein, minerals, and vitamins as well as fibre in the diets of many people worldwide. Bread is traditionally produced from wheat (Triticum aestivum L.) flour. Region with unfavourable climatic conditions for wheat cultivation depend on wheat importation to fulfill their demands. The inability of some countries to sustain their wheat import for making wheat based foods makes it imperative that some substitutes for wheat must be made in bread preparation (Rai et al., 2012). Compositing wheat flour with locally available cereals and root crops is a way of reducing over reliance on wheat importation in countries with unfavorable climatic conditions for wheat production. It also encourages the agricultural sector and focuses on the use of composite flour for bread.
Flat bread is simple bread made from flatten dough of flour, water, salt with or without yeast and other optional ingredients (Al-Dmoor, 2012). It has a large surface area and a very thin crumb. Flat breads have been the oldest and well known bread type of the world. Their popularity and demand is growing owing to their versatile form, taste, texture and ease of use. Because flat breads are made from flour of high extraction rate, their colour, texture and chew ability are affected directly by the levels of aluerone layer, bran and germ in the flour (Al-Dmoor, 2012). In many countries, flat bread could be considered a suitable carrier for increasing the dietary intake of several micro nutrients, vitamins and proteins, due to its widespread geographical distribution and high frequency of consumption (Al-Dmoor, 2012).
Whole-grain wheat flour is used in baking to increase fibre content and to provide vitamins from the bran layers of the kernel. Whole wheat flour is a coarse –textured flour ground from the entire wheat kernel and thus contains the bran, germ and endosperm. Every part of the wheat grain supplies elements needed by the human body. Whole wheat flour therefore contains all the nutrient in the whole grain. Nutritionally, whole wheat is a rich source of vitamins, minerals, protein, fat and fibre while the refined grain is mostly starch (Mannay and Shadaksharaswany, 2005). Recent findings on the health implications of whole grains, precisely their bioactive fractions, have underlined the potential status of wheat and other cereals as functional foods, which can reduce the risks for several chronic diseases including the type 2 diabetes, cardiovascular diseases, obesity, and some cancer (Scal and Brownlee, 2015, Zhang et al., 2018). Usually, whole grain is milled to leave just the endosperm for white flour, the by-products of bran and germ discarded. Wheat therefore, is perhaps the most popular energy grain for the production of confectionery products because of the unique properties of its protein (gluten) which combines strength and elasticity required to produce bread, cookies, cakes and pastries such as spaghetti, macaroni, and noodles of desirable texture and flavor (Potter and Hotchkiss, 2006; Akhar et al., 2008). Much efforts have been made to enrich bakery products especially bread with non-wheat flour so as to increase the dietary fibre content, yet maintain the desirable eating qualities (Banu et al., 2012).
Orange- fleshed sweet potato is gaining importance as the cheapest source of antioxidant having several physiological attributes like anti-oxidation, anti-cancer and protection against liver injury and is most suiting as biofortified crop to combat malnutrition in small and marginal farming community (Nestel et al. 2006). Orange fleshed sweet potato has considerable potential to contribute to a food based approach to tackle the problem of vitamin A deficiency, a major public health concern of the poorer sections. The orange-fleshed sweet potato consumption is an alternative to increase nutrient intakes from biofortified crops (Nestel et al. 2006). Therefore, the production of flour from orange fleshed sweet potato increases the product life and facilitates its incorporation in the diet, in combination with other foods. Flour, when prepared from roots with high beta-carotene content, is a rich source of provitamin A, which has beneficial effects on human health, such as improving immunity and reduction of degenerative diseases as cancer, cardiovascular disease, cataracts and macular degeneration. However, there is a need to optimize the process conditions and storage of the flour in order to reduce the loss of carotenoids and other nutrients (Rodriguez-Amaya et al. 2011).
Soy bean is a legume which has its proteins closely relating with animal protein and with a high-protein quantity, close to 40–45% of the total solids (Goyal et al., 2012). They are among the best sources of plant-based proteins, their protein content ranges from 36-56% of the dry weight (Grieshop and Fahey, 2001). Soybeans contain significant amounts of phytic acid, dietary minerals and B vitamins (Grieshop and Fahey, 2001). The soybean is economically the most important bean in the world providing vegetable protein for millions of people and ingredients for hundreds of chemical products. Moreover, phytochemicals like isoflavones contained in soybeans are effective cancer preventive agents for lowering risks of various cancers, its also involved in prevention of osteoporosis through its phytoestrogen effect and in the prevention of neovascularization in ocular conditions. (Zhu et al., 2005). Hence soybean is regarded as the richest source in food value of plant food consumed in the world (Bekebian, 2000, Mannay and Shadaksharaswany, 2005: Giami and Ndife et al., 2011). Due to its nutritional benefits, its has been referred to as “the protein hope of the future” (Islam et al., 2007).
Statement of the Problem
As a result of unfavourable climatic conditions, the quality of weed produced in Nigeria is below the local demand. Consequently, Nigeria is still importing weed into the country to augment local production and this has negative effect on the economy of the country.
Orange Fleshed Sweet Potato dose not only have short shelf life but is underutilized in Nigeria despite its nutritional and health promoting properties.
Both wheat and orange fleshed sweet potato are high in carbohydrate but low in protein content. Continuous consumption of product made from them has the potentials of contributing to the protein-energy malnutrition that is still prevalent in most communities in Nigeria.
Justification of the study
Partial replacement of wheat flour with orange fleshed sweet potato would reduce the quality of wheat required for the production of pastry product and the amount of foreign exchange needed for wheat importation.
Successful production of acceptable flatbread from composite of whole wheat, orange fleshed sweet potato and soy flours would increase the utilization of both orange fleshed sweet potato and soy bean that are produced in Nigeria, create wider product variety and may generate employment opportunities.
In addition, soy bean proteins are high in lysine but low in sulphur containing amino acids whereas cereals protein are deficient in lysine but have high amount of sulphur containing amino acids. Therefore, the combination of cereal grains with legume proteins would improve the amino acid profile of the final product and the product could be used to address the problems of protein energy malnutrition in Nigeria.
Also, since orange fleshed sweet potato is rich in β-carotenoid, its incorporation in the composite flour would help to improve the vitamin A content of the produce flat bread.
General Objectives of the study
The general objective of the study was to evaluate the effect of substituting whole wheat and orange flesh sweet potato composite flour with soy bean flour on the functional properties of the blends and quality of flat bread made from the blends.
Specific Research Objectives
The specific research objectives of the study where to:
Produce composite flour from blend of whole wheat and orange fleshed sweet potato flour fortified with soybean flour.
Evaluate some functional properties in the flour blends.
Determine the proximate composition, minerals, vitamins, and sensory properties of flat bread produced from the flour blends.
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