ABSTRACT
Cleaned Bambara groundnut seeds were
divided into four lots. Each lot was separately pretreated thus: germinated,
roasted, germinated and roasted, and unprocessed which served as control. Each
sample was ground, sieved, and extruded using single screw extruder. Consumer
preference test was done by a taste panel of 50 people who rated the products
on the attributes of colour, taste, flavour and overall acceptability using a
9-point hedonic scale. The treatment (roasting) given on the most preferred
product was adopted in producing composite of bambara and “acha” flour, which
was mixed with graded levels of carrot and other ingredients, and extruded. The
product samples were subjected to analyses for chemical composition, residual
anti-nutrients, physico-chemical and sensory properties using standard methods.
The samples were stored for six months under ambient conditions (28±2ºC) and
analysed at 2 months interval for moisture, texture, provitamin A (β-carotene)
and sensory properties. Extruded snacks from the composite of bambara groundnut,
hungry rice and carrot had high protein (15-16%), β-carotene (180-550.13mg/100g
retinol) and minerals (iron and zinc) contents. Inclusion of carrot to the
composite increased (p≤0.05) the β-carotene content of the product, when
compared with the control. There were no significant differences (p>0.05)
between the sensory qualities of the control and products with 5% to 15%
carrot. Extrusion cooking significantly (p<0.05) reduced moisture content
and brought about concentration of other proximate components. It also
significantly (p≤0.05) reduced phytate from 91.01-81.11mg/100g to
36.75-30.58mg/100g, tannin from 0.16mg-0.26/100g to 0.06-0.09mg/100g. Trypsin
inhibitor and haemagglutinin activities were reduced from 6.81-8.32mg/100g and
4.01-6.50Hu/mg protein, respectively, to undetectable levels. Extrusion cooking
improved protein digestibility of the snacks. β-carotene and minerals were not
significantly (p>0.05) affected by the extrusion cooking, while there was a
significant reduction (p<0.05) of vitamin C from 6.21-8.96mg/100g to
2.51-4.05mg/100g in the extruded snacks. Significant (p<0.05) reductions
were observed in vitamin B1(40-50%), B2(15-24%), B3(15-24%)
and B6(25-30%) content of the extruded snacks. Storage for six
months did not adversely influence the sensory characteristics of the developed
snacks. It is evident from the composition of the developed products that
protein-energy malnutrition and micronutrient deficiency problems can be
averted through dietary diversification and extrusion cooking technology.
TABLE OF CONTENTS
Title Page
Abstract
Table of Contents
Chapter One
1.0 Introduction
1.1 Statement of the Problem
1.2 Significance of the Study
1.3 Objectives of the Study
Chapter Two
2.0 Literature Review
2.1 Extruded Snacks
2.2 Legumes
2.2.1 Bambara groundnut
2.2.2 Processing of legumes
2.2.3 Milling and grinding
2.2.4 Soaking, boiling and steaming
2.2.5 Germination
2.2.6 Roasting
2.2.7 Preparation of protein concentrate
2.2.8 Canning of legumes
2.2.9 Quick cooking legumes
2.2.10 Nutritional importance of legumes
2.2.11 Antinutritional constituents of legumes
2.2.11.1 Protease (Trypsin) inhibitor
2.2.11.2 Phytates
2.2.11.3 Polyphenols (Tannins)
2.2.11.4 Cyanogens
2.2.11.5 Lectins
2.2.11.6 Effect of processing on legume food quality
2.2.11.7 Effect of processing methods on anti-nutrients
2.3 Extrusion cooking and its effect on food quality
2.3.1 Application of extrusion cooking
2.3.2 Advantages of extrusion cooking
2.3.3 Effect of extrusion cooking on protein quality
2.3.4 Effect of extrusion cooking on the anti-nutrients
2.3.5 Effect of extrusion cooking on amino acids
2.3.6 Effect of extrusion cooking on Maillard reaction
2.3.7 Effect of extrusion cooking on carbohydrates
2.3.8 Effect of extrusion cooking on vitamins
2.3.9 Effect of extrusion cooking on minerals
Chapter Three
3.0 Materials and Methods
3.1 Materials
3.2 Methods
3.2.1 Preparation of samples
3.4.0 Analysis of Raw Material and Product
3.4.1 Proximate composition
3.4.2.0 Mineral content analysis
3.4.2.1 Determination of phosphorus
3.4.2.2 Determination of Iron
3.4.2.3 Determination of calcium
3.4.2.4 Determination of potassium
3.4.2.5 Determination of manganese
3.4.2.6 Determination of copper
3.4.2.7 Determination of magnesium
3.4.3 In vitro protein digestibility
3.4.4 Functional properties
3.4.5 Determination of anti-nutritional factors
3.4.6.0 Determination of vitamins
3.4.6.1 β-carotene and Vitamin A
3.4.6.2 Vitamin B1
3.4.5.3 Vitamin B2
3.4.6.4 Niacin
3.4.6.5 Vitamin C
3.4.7.0 Experimental design/data analysis
Chapter Four
4.0 Results and Discussion
4.1 Effect of Processing Treatment on the Proximate Composition of
Bambara Groundnut
4.2 Effect of Processing Method of Some Anti-Nutritional Factors
4.3 Effect of Processing Methods on the Functional Properties of
Bambara Groundnut
4.4 Effect of Treatment Method on Consumer Acceptability of
Extruded Snacks
4.5 Proximate Composition of Hungry Rice “acha” and Fresh Carrot
4.6 Effect of Extrusion on the Proximate Composition of Bambara/
Acha Blends Fortified with Carrot
4.7 Sensory Qualities of Extruded Snacks
4.8 Effect of Extrusion on the Residual Anti-nutrients
4.9 Effect of Extrusion on in-vitro protein Digestibility
4.10 Effect of Extrusion on the Mineral Content of the Bambara
groundnut/Acha Blends Fortified with Carrot
4.11 Effect of Extrusion on the Vitamin Content of the Snacks
4.12 Effect of Storage on the Texture of the Extrudates
4.13 Effect of Storage on the Sensory Qualities of the Snacks
4.14 Effect of Storage on the Vitamin Content of the Snacks
Chapter Five
5.0 Conclusion and Recommendations
5.1 Conclusion
5.2 Recommendations
References
CHAPTER ONE
1.0 I N T R O D U C T I O N
In many developing countries such as Nigeria, malnutrition is an endemic dietary problem characterized by protein-energy malnutrition and micro-nutrient deficiency (Nnanyelugo, 1990; Bowley, 1995; Adelekan et al., 1997; WHO, 2005, 2006). In the past few years, efforts have been made to reduce or eliminate the problem globally. Dietary diversification has been suggested as the ultimate solution to malnutrition challenges. Dietary diversification involves the use of commonly available or consumed grains, legumes and other nutritious crops to meet the nutritional/dietary need of the population. Consequently, there is a need for baseline research to identify and exploit the potentials of locally available but under-utilized agricultural produce in nutritious product formulations.
Among the locally available under-utilized agricultural produce are bambara groundnut, hungry rice (“acha”) and carrot, whose utilization are presently limited to household level, even though they have potentials for industrial application. Bambara groundnut is an under-utilized indigenous African legume and one of the most important crops in the continent. Total production has been estimated to be over 300,000 tons per year (Poulter, 1981). It is an inexpensive source of high quality protein and the third most important legume in Africa, after cowpea and groundnut (Obizoba and Egbuna, 1992; Enwere and Hung, 1996). Despite this, its use is limited to household consumption in most parts of Nigeria. In Eastern States, the seed is used in the preparation of a steam gel popularly known as “Okpa” while in the Northern parts it is consumed in the form of meal or roasted snack. According to Poulter (1981), bambara groundnut contains 24% protein, 6-8% lysine, 1.3 methionine and 50% carbohydrate, it also contains reasonable quantities of minerals and vitamins.
Hungry rice commonly referred to as “acha”, “fonio” or “finni” is another under-utilised crop. It is estimated that over 101.3 tons is produced annually in Nigeria, mostly in the Northern States (Bauchi, Plateau and Kaduna) (CBN, 2005). Hungry rice is processed and consumed in a variety of ways such as “tuwo”, “kunnu”, “gote”, while whole grains are used in preparation of soup and porridge (Jideani, 1999). Hungry rice is reported to be uniquely rich in methionine and cystine (NRC, 1999). It also relatively evokes low sugar release on consumption, which is an advantage for diabetics (Ayo et al., 2003).
Carrot (Daucus carota) is one of the traditional root crops of Northern Nigeria. It is very rich in carotene the precursor of vitamin A, and contains appreciable amount of thiamine and riboflavin (Pederson, 1980). Carrot is fast acquiring the status of “lost crop” in the African continent because its local utilization is limited to direct eating in unprocessed form as snack (Pederson, 1980). There is need to diversify and popularize other means of utilizing carrot to derive maximum health benefit from its nutrient particularly carotenoids(carotene/β- carotene).
Blends of these nutrient dense agricultural produce could be exploited to develop nutritious shelf stable snacks, which could help in alleviating problems of protein-energy malnutrition and micronutrient deficiency prevalent in the country. However, to get maximum nutrient benefit from these crops, they need to be processed to reduce or remove inherent anti-nutrients that may interfere with the biological availability of the nutrients. Among the methods used in removing inherent anti-nutrients include roasting, germination, frying, cooking and recently extrusion cooking (Siegal and Fawcett, 1976; Rajawat et al., 1999, Nwabueze, 2006).
Extrusion cooking technology is a high temperature short time (HTST) technology. It has been extensively used in producing varieties of food products, especially in creation of novel food products and improvement of existing ones like snacks (Lowtan et al., 1985; Lasekan et al., 1996). It is considered a beneficial food processing technique, due to its effective destruction of growth inhibitors and contaminating micro-organisms (Tarte et al., 1989; Chang et al., 2001). It has also been shown to improve the nutritional quality of food products like snacks (Pham and Rosario, 1987, Rajawat et al., 1999; Nwabueze, 2006).
1.1 Statement of the problem
Most developing countries experience high burden of protein – energy malnutrition and severe micro-nutrient deficiencies, which have attracted the numerous interventions by major stakeholders, to mitigate the challenges. Dietary diversification involving the use of commonly available or consumed grains, legumes and other nutritious crops to meet the nutritional needs of the population has often been advocated. Consequently, the idea of production of nutrient dense ready-to-eat extruded snacks from blends of bambara groundnut, hungry rice (“acha”) and carrot....
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