ABSTRACT
Protein energy malnutrition and Vitamin A deficiency remains a major problem in Nigeria and Sub Saharan Africa. As a result, this study was aimed at developing acceptable and nutrient- dense biscuits using Vitamin A bio-fortified crop, Orange-fleshed sweet potatoes and locally underutilized crop, Bambara groundnut at different substitution levels with wheat flour. Biscuits were produced from composite flour blends obtained from Bambara groundnut (BGF) (Vigna subterranean L.verdc), Orange fleshed sweet potato (OFSPF) (Ipomoea batatas), and wheat flour (Triticum aestivum). In order to reduce the level of trans fatty acids in the biscuit, Sunflower oil was used to replace margarine. The resulting flour blends were analysed for functional and anti-nutritional properties while the biscuit samples were subjected to nutritional and sensory evaluations. The results were subjected to Statistical Analysis of Variance (ANOVA) and means were separated using the Duncan multiple range test and judged significant at 95% confidence level (P<0.05). The Protein, Fibre, Ash and Carbohydrate content of the biscuit samples were found to significantly (P<0.05) increase as the level of substitution with Bambara nut increased. On the other hand, there was a significant decrease in the Moisture and Fat content of the biscuit samples as the level of substitution with Bambara nut increased. The Provitamin A content of the samples was found to increase as OFSPF and BGF were included in the samples. However, Vitamin B3 content reduced significantly with increase in BGF substitution. The results obtained also showed that tannin and phytate content of the flour blends were in the range of 0.09 to 0.14mg/100g and 0.07 to 0.15mg/100g respectively. There were found to be within the acceptable limits for human consumption. The bulk density, oil absorption capacity, water absorption capacity, swelling index, foam capacity and foam stability of the flour blends were found to increase significantly when the level of Bambara nut was increased. The sensory attributes of the biscuits showed that biscuit samples from wheat flour (control) had the highest rating for all the attributes. However, biscuit samples made from wheat-OFSPF blends (W80-O20) and wheat- OFSPF and BGF (W60-O20-B20) compared favourably with the control sample with the later having the highest general acceptability score. Other biscuit samples were generally acceptable to the panel as they scored above 5 which is the minimum acceptable score in a 9 point hedonic scale. Generally, no sensory attribute contributed less than 50% to the general acceptability thus indicating that all attributes had a significant contribution to the general acceptability of the biscuit samples.
TABLE OF CONTENTS
TITLE PAGE i
CERTIFICATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
TABLE OF CONTENTS v
LIST OF TABLES viii
LIST OF FIGURES ix
ABSTRACT x
CHAPTER 1
INTRODUCTION 1
1.1 Statement of problem 5
1.2 Objectives of the study 8
1.2.1 General objective 8
1.2.2 Specific objectives 8
1.3 Significance of study 8
CHAPTER 2
LITERATURE REVIEW 10
2.1 Biscuits 10
2.2 Brief history of sweet potato 11
2.2.1 Varieties of sweet potato 12
2.2.2 Utilization of sweet potato 12
2.2.3 Anti-nutrients in sweet potato 13
2.2.4 Orange-fleshed sweet potato 14
2.2.5 Nutrient composition of orange fleshed sweet potato 14
2.3 Brief history of Bambara groundnut 17
2.3.1 Nutrient composition of Bambara groundnut 19
2.3.2 Utilization of Bambara groundnut 20
2.3.3 Anti-nutritional factors in Bambara groundnut 21
2.3.4 Processing methods of overcoming ANF’s effect in Bambara groundnut 22
2.4 Origin and distribution of wheat 23
2.4.1 Types of wheat 24
2.4.1.1 Major cultivated species of wheat 24
2.4.2 Nutritional content of wheat 25
2.4.3 Utilization 26
2.5 Baking technology 27
2.5.1 Baking ingredients 27
CHAPTER 3
MATERIALS AND METHODS 29
3.1 Source of raw materials 29
3.2 Preparation of raw materials 29
3.2.1 Production of orange-fleshed sweet potato flour 29
3.2.2 Production of Bambara groundnut flour 30
3.2.3 Formulation of blends 32
3.3 Determination of functional properties of the flour blends 32
3.3.1 Water absorption capacity 32
3.3.2 Oil absorption capacity 32
3.3.3 Bulk density 33
3.3.4 Foam capacity and foam stability 33
3.3.5 Swelling index 33
3.4 Determination of Anti-nutritional factor 34
3.4.1 Determination of Tannin content 34
3.4.2 Determination of phytate content 35
3.5 Production of Biscuits 35
3.5.1 Production of biscuits from the composite flours with sunflower oil 36
3.5.2 Production of biscuits from wheat flour with margarine (control) 36
3.6 Proximate composition of biscuit samples 37
3.6.1 Determination of moisture content 37
3.6.2 Determination of protein content 37
3.6.3 Determination of crude fibre 38
3.6.4 Determination of fat content 39
3.6.5 Determination of ash content 39
3.6.6 Determination of carbohydrate content 40
3.7 Vitamin content determination 40
3.7.1 Determination of Vitamin A 40
3.7.2 Determination of Niacin 41
3.8 Mineral content determination 41
3.8.1 Determination of potassium content 41
3.8.2 Determination of calcium content 42
3.8.3 Determination of Iron content 43
3.9 Sensory evaluation 44
3.9.1 Statistical analysis of data 44
CHAPTER 4
RESULTS AND DISCUSSION 45
4.1 Nutrient content of the biscuit sample 45
4.1.1 Proximate composition of the biscuit samples 45
4.1.2 Vitamin content of the biscuit samples 50
4.1.3 Mineral content of the biscuit samples 52
4.2 Anti-nutrient properties of the flour blends 55
4.3 Functional properties of the flour blends 57
4.4 Sensory scores of the biscuit samples 61
CHAPTER 5
CONCLUSION AND RECOMMENDATION 67
5.1 CONCLUSION 67
5.2 RECOMMENDATION 68
LIST OF TABLES
Table 2.1: Nutrient composition of orange fleshed sweet potato flour 16
Table 2.2: Sweet potatoes (Ipomea batatas) raw nutrition value per 100g 17
Table 2.3: Nutritional status of Bambara compared to other common legumes 18
Table 2.4: Mineral content (mg100g-1) in raw Bambara nut and its fermented flour 19
Table 2.5: Anti-nutritional factors (mg100g-1) in raw Bambara nut and its fermented flour 22
Table 2.6: Amino acid content (g100g-1) of raw Bambara nut and its fermented flour 23
Table 2.7: Nutritional information on wheat flour 25
Table 3.1: Percentage formulations of the flour blends 32
Table 3.2: Recipe for the production of biscuit from the composite flours with sunflower oil 35
Table 3.3: Recipe for the production of biscuit from wheat flour with margarine 36
Table 4.1: Proximate composition (%) of the biscuit samples 46
Table 4.2: Vitamin content (mg/100g) of biscuit samples 51
Table 4.3: Mineral content (mg/100g) of biscuit samples 53
Table 4.4: Anti-nutritional factors in the flour blends 56
Table 4.5: Functional properties of the flour blends 58
Table 4.6: Sensory scores of the biscuit samples 62
Table 4.7: Contribution of sensory attributes to the general acceptability of the biscuit samples 65
LIST OF FIGURES
Figure 1: Flow chart for the production of orange fleshed sweet potato 30
Figure 2: Flow diagram for the preparation of Bambara groundnut flour 31
Figure 3: Flow diagram for biscuit production 31
CHAPTER 1
INTRODUCTION
Protein Energy Malnutrition (PEM) continues to be the major nutritional problem resulting from under-nutrition that affects children in most of the developing world (Muller and Krawinkel, 2005). Africa is home to over 70 million undernourished children (World Food Programme (WFP), 2008; World health organization (WHO), 2010). In this region, poverty causes food shortages and most vulnerable populations survive predominantly on starchy staples such as maize, wheat, rice, sorghum, millet and cassava, with little or no meat and dairy products (Mayer et al., 2008). The protein nutritional quality of these staple foods is poor and lysine is the most limiting amino acid (United States Department of Agriculture (USDA), 2008). The problem is further compounded by the Human Immunodeficiency Virus/Acquired Immune Deficiency Syndrome (HIV/AIDS) epidemic that has increased the number of vulnerable children. Strategies that have been used to address protein deficiencies include food diversification (FAO, 1997), fortification of food with indispensable amino acids, supplementation with good quality protein, improvement of protein quality by plant breeding and genetic engineering, and minimising the damage to the nutritional value of protein during food processing and storage (Friedman, 2004).
Cereals constitute the most suitable vehicle for delivering proteins to at-risk populations because of their widespread consumption, stability and versatility (Bulusu et al., 2007). The production of novel cereal-based food products designed to provide additional proteins to the daily diet has increased (Vitali et al., 2008). These products include nutritionally improved biscuits designed to reduce the risk of developing nutrient deficiency diseases. Some reasons for their increased popularity are their low cost compared to other processed foods, varied taste, ease of availability and longer shelf-life (Sudha et al., 2007). To augment the protein quality, the concept of cereal-legume complementation by blending cereal and legume flours can be applied (FAO/WHO 1994; Hooda and Jood, 2005).
Today, plant proteins play a significant role in human nutrition particularly in developing countries where average protein intake is less than the required. Proteins of high biological value (such as meat, egg and milk which are also referred to as animal protein) are expensive for developing countries like Nigeria, where a majority of the masses are poor (Obizoba and Anyika, 1994). Due to inadequate supplies of animal proteins, there has been a c onstant research for new protein sources for use as both functional food ingredients and nutritional supplements (Ezeuh, 1977; Bahadoran and Mirmiran, 2014; Maphosa and Jideani, 2017). The need for strategic development in the use of inexpensive local resources in the production of staple foods has been promoted by organizations such as the Food and Agricultural Organization (FAO) and the United Nations refugee feeding programs (FAO/WHO, 1994; Awogbenja and Ndife, 2012). This led to the initiation of the composite flour program, the objective of which was to seek ways of substituting flours, starches and protein concentrates from indigenous crops, for as much wheat as possible in baked products (WHO, 1994).
Mepba et al. (2007) stated that many researchers have studied the physical and baking properties of composite biscuits from starchy staples like cassava, cocoyam, plantain, etc. Oluwole and Karim (2006) produced biscuit from various blends of Bambara, cassava and wheat flours respectively. In a research carried out by Ayo et al. (2014), Bambara groundnut flour was added to Acha based Fura, which is a semi solid dumpling cereal usually made from pearl millet. Adelekan and Oyewole (2010) carried out an investigation on the supplementation of ogi with soybean flour and concluded that the protein content of the composite flour increased. Work also carried out by Aminigo and Akingbala (2004) on the fortification of maize with okra seed (defatted and roasted) at 20% inclusions indicated that the protein content increased by 122% for defatted flour and 106% for roasted flour. Baker et al. (2010), investigated the effect of soybean protein on sorghum and concluded that the protein content of the composite flour increased by two fold. Mariam (2005), carried out a research in the formation of a composite blend weaning porridge using de-hulled rice, groundnut, Bambara groundnut and carrot in the ratios 60:20:10:10% w/w basis. Mohsen et al. (2009) achieved a 12 to 20% increase in protein content by substituting wheat with 5 to 20% soy protein isolate. Similarly, Singh et al. (2000) and McWatters (1978) doubled protein content in wheat biscuits by substituting 20 and 30%, respectively, wheat flour with defatted soy flour (DSF). There are also reports of biscuits made using sorghum flour (Badi and Hoseney, 1976) or pre-gelatinised sorghum flour dough (Dendy, 1993). The production of sorghum-legume composite biscuits has been reported by Hikeezi (1994) who supplemented sorghum with peanut or sunflower flours raising the protein content to 16%. Mridula et al. (2007) showed that biscuits of acceptable quality can be made using wheat-sorghum composites with 10 to 50% sorghum and 5% DSF.
Sweet potato is a member of the Convolvuaceae family, and it is a dicotyledonous root vegetable plant with large starchy, sweet-tasting, tuberous roots. Besides the tubers, the young leaves and shoot are also consumed sometimes as greens. Sweet potato (Ipomoea batatas) is the only member of the over 1,000 species of the Convolvuaceae family and the approximately 50 genera that is of significant importance, some others are used locally, but many are actually poisonous. Potato is the world's most widely grown tuber crop and the fourth largest food crop in terms of fresh produce after rice, wheat, and maize (Khaliduzzaman et al., 2010).
Orange-fleshed sweet potato (OFSP) flour can serve as a source of energy and nutrients, β-carotene (pro-vitamin A), minerals (Ca, P, Fe, Zn and K) and can add natural sweetness, color, flavor and dietary fiber to processed food products (Woolfe, 1992).The potato was introduced in 2007 by Harvest Plus, a part of the consultative group on International Agricultural Research (CGIAR) program on Agriculture for Nutrition and Health. OFSP is a highly nutritious crop that has health benefits for pregnant women, new mothers and young children. Processing OFSP into flour can make it more acceptable as a traditionally processed food and the possibility of incorporating β-carotene in biscuits. The high fibre content of orange fleshed sweet potato flour increases its utility in various new food products development. Addition of various proportions of OFSP flour in wheat flour can increase the fibre and carotenoid nutritive value that helps in lowering the wheat gluten level and prevent Celiac disease (Tilman et al., 2003).
Bambara groundnut is a herbaceous annual legume and grows for not more than 20cm in height. It belongs to the Fabacea family, subfamily Papilionodease (Mkandawire, 2007; Murevanhema and Jideani, 2013). Bambara groundnut is also known as nyimo in Shona, dithloo in Setswana, indlubu in Ndebele (Murevanhema and Jideani, 2013). The legume has two variants, Vigna subterranean variety spontanea is the wild variety whilst the Vigna subterranean variety subterranean is the domesticated one (Swanevelder, 1998). Bambara groundnut falls in the same family as peanuts (Arachis hypogaea) and cowpea (Vigna unguiculata) (Mkandawire, 2007). As a legume, Bambara groundnut is high in protein that plays an important role in human nutrition. A detailed study shows that it contains 20-26% crude protein (high in lysine; 6.6%); and makes an excellent source of supplementing proteins in the diet (Asselberg, 1998). Bambara groundnut has a high vitamin and mineral content like iron, phosphorous and calcium. It also has a high content of crude fibre and high levels of sulphur containing amino acids which are limited in cereals. These compositions gives Bambara groundnut its high nutritive and health value (Asselberg, 1998).
In Nigeria, biscuits are one of the most consumed cereal foods apart from bread, because they are readily available in local shops as ready- to-eat, convenient and inexpensive food products containing digestive and dietary principles of vital importance (Kulkarni, 1997). Biscuits are produced as nutritive snacks from unpalatable dough that is transformed into appetizing products through the application of heat in the oven (Olaoye et al., 2007).
It is in light of this that this work seeks to address the problem of Protein Energy Malnutrition and vitamin A deficiency using supplementation and fortification as food based approaches targeted against malnutrition.
1.1 STATEMENT OF THE PROBLEM
Malnutrition is a devastating problem in Nigeria, not only to its people, but also to its security and economy.. Amongst the malnutrition problems, PEM and VAD have been the major public health problems for decades, particularly in Africa and parts of Southern Asia (Müller and Krawinkel, 2005). PEM is a prevalent health condition among under-five children in developing countries and contributes directly or indirectly to almost half of under 5 mortalities globally (Stipanuk, 2006). It is a macronutrient deficiency disease resulting from an inadequate intake and/or utilization of protein and energy, and mainly affects children most because of their higher needs for protein and energy per kilogram body weight compared to adults (Stipanuk, 2006). On the average, the PEM associated mortality in Sub-saharan Africa is between 25 and 35%. It is estimated that approximately 20% of children younger than five years in developing Nigeria are underweight and 30% have stunted growth while 8% are wasted (UNICEF, 2016). The main cause of PEM in developing countries is dependence on a single starchy staple for virtually all the protein and energy requirements (Onis and Blossner, 1997). This is mainly due to the high cost of first class proteins (Jamabo and Onwukwe. 2010).
Different approaches have been taken in an effort to curb protein energy malnutrition. These include the bio-fortification of foods, supplementation as well as the dietary approach of fortifying foods using nutritionally richer foods (Pandey and Urquia, 2007). The use of cereal-legume based foods is therefore advocated as alternative protein and energy source for infants and adult food products. The nutritional complementarity of cereals and legumes has long been recognized (Aykroyd, 1982; Mensah and Tomkins, 2003). It has been recognized that cereals are deficient in total nitrogen and the essential amino acids, Lysine and Tryptophan (Davidson et al., 1980). On the other hand, legumes are deficient in sulphur containing amino acids, Methionine and Cystine but rich in Tryptophan and Lysine ((Davidson et al., 1980). When cereals and legumes are judiciously selected and combined, a desirable pattern of amino acids comparable to or higher than the reference protein is obtained (Nnam, 2001). Among the legumes widely cultivated in Nigeria, Bambara groundnut (vigna subterranea) is among the underutilized. It has not been adequately exploited as human food because of constraints like hard to cook phenomenon, strong beany flavour, presence of anti-nutrients and poor de-hulling and milling characteristics (Enwere and Hung, 1996).
Vitamin A deficiency (VAD) is a major public health risk in developing countries; children and pregnant/lactating women being the most vulnerable. It increases children’s risk to common illnesses and impairs children’s growth, development, vision and immune system and in severe cases results in blindness and death. In women, vitamin A deficiency increases the risk of death during pregnancy, as well as giving birth to low weight children (Tumwegamire et al., 2004). The World Health organization (WHO) has classified Vitamin A deficiency as a public health problem affecting about one third of children aged 6 to 59 months with the highest rates in sub-Saharan Africa (48%) (UNICEF, 2016).Young children are at risk of developing vitamin A deficiency due to their increased need during growth and their vulnerability to infections; Measures to prevent and control VAD were adopted in Rome (1992) at which the priority of food based approaches were emphasized. The benefits of food based approaches such as micronutrient fortification are that they are preventative, cost-effective and sustainable. Orange-fleshed sweet potato (OFSP) has been reported to be among food based approaches to provide a cheap source of beta-carotene as a source of vitamin A (Low et al., 2001).
A present day dietary concern is the consumption of a large amount of fat and sugar. With the growing incidence of obesity and diabetes, low calorie foods have gained immense popularity. Most well-maintained strategies in terms of fat reduction diets involve either the use of low-fat foods or fat substitutes or modifications such as trimming of fat from foods (Chandana and Navaratne, 2015). High fat consumption is associated with the development of various metabolic disorders such as obesity and diabetes, which, in turn, increase the risk of cardiovascular diseases and some types of cancer (Micha and Mozaffarian, 2010). Edible vegetable oils are very important component of humane diet. The beneficial effects of vegetable oils are basically due to their high content of unsaturated fattty acids and their valuable bioactive compounds, which have been found to decrease the risk of cardiovascular disease (CVD) (Arshad et al., 2008). Sunflower oil is able to withstand high temperatures and is thus a good choice when frying and baking foods. Sunflower oil is generally considered a premium oil because of its light color, high level of unsaturated fatty acids, bland flavor and high smoke points.. Sunflower oil in particular, besides their technological aspects, has interesting nutritional benefits, anti-oxidant and anti-cholesterolemic activities due to gelator features (Bot et al., 2009) and a polyunsaturated fatty acid rich profile. Sunflower oil seeds are a rich source of linoleic acid, which is one of the nutritionally essential fatty acids (Jacob and Leelavathi, 2007)
Biscuits are the largest category of snack foods among baked products worldwide (Ait-ameur et al., 2008). In Nigeria, like many other developing countries, the increasing phenomenon of urbanization coupled with the growing number of working mothers have contributed greatly to the popularity and increased consumption of snack foods especially biscuits. They are popular snacks among children. They offer a valuable vehicle of supplementation with protein and other nutrients because of their popularity, relatively low cost, varied taste, ease of availability, high nutrient density and long shelf-life (Sudha et al 2007).
It is against this backdrop that this study was designed to complement the amino acid content of wheat flour with Bambara groundnut by providing a complete blend of all the essential amino acids in the flour and their products and also to fortify wheat flour with vitamin A through the use of orange fleshed sweet potatoes thereby producing nutrient dense biscuits and to evaluate its nutrient content and sensory characteristics. The result of this study will provide a recipe in an acceptable form that will increase the utilization of Bambara groundnut and orange fleshed sweet potatoes thus reducing wheat importation.
1.2 OBJECTIVES
1.2.1 General Objective
The General objective of the study is to determine the nutrient content and sensory characteristics of biscuits produced from wheat, orange-fleshed sweet potato and Bambara nut flour blends.
1.2.2 Specific objectives:
The Specific objectives of the study are to:
1. Produce flours from wheat, orange fleshed sweet potato and Bambara groundnut.
2. Produce composite flour blends from the different flours
3. Evaluate the functional properties (Oil absorption capacity, Water absorption capacity, Swelling index, Bulk density, Foam capacity and stability) of the flour
4. Evaluate the anti-nutrient (Tannin and Phytate) components in the flour
5. Produce biscuits from the composite flours using sunflower oil as a substitute for margarine in the recipe.
6. Evaluate the nutrient content (Proximate composition, Vitamin A content, Niacin, Potassuim, Calcium and Iron) of the baked biscuits.
7. Evaluate the sensory characteristics of the baked biscuits.
1.3 SIGNIFICANCE OF THE STUDY
The findings of this study will be useful to the Ministry of Health, Home Makers, Entrepreneurs who specialize in producing baked goods, Food and nutrition lecturers, Home economics lecturers, the students of Human Nutrition and Dietetics and the Nation as a whole.
Ministry of health: The findings of this research work will provide evidence on the feasibility of micronutrient fortification and nutrient supplementation using locally available foods transformed into composite flour to be used in making a variety of products thereby making it possible for this approach to be incorporated into food based strategies targeted at combating malnutrition.
The Home Makers: These are the people who take care of the homes and all food preparation is done or initiated by them. The findings of this study will help them to know that the sweet potatoes they have been utilizing only by boiling, frying and using to prepare pottage etc. and the Bambara groundnut they have been utilizing only roasted and using to make puddings known locally as Okpa can also be processed into flour and used to make baked goods for family consumption.
The Entrepreneurs: will find this work useful because their main aim is to maximize profit. Availability of cheap flours produced from orange-fleshed sweet potato and Bambara nut which can be used to substitute wheat flour in various proportions will help them achieve that aim.
Food and Nutrition Lecturers: will also find the study useful because the findings of the study will be very useful instructional materials for their students.
Home Economics Lecturers: will also find this work useful because they will use it in instructing their students during practical classes on pastry production.
The students of Human Nutrition: will find this study very helpful because the findings will serve as a guide for future research works.
The Nation: This will convince them to set up easily affordable and accessible mills where these flours can be produced in large industries and will be supplied to industries that produce baked goods. This will serve as a source of revenue for the Nation as a whole.
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