ABSTRACT
Extruded strips were produced from different blends of orange-fleshed sweet potato (Ipomea batatas), mungbean flour (vigna radiata) and cassava (manihot esculenta) flours with substitution ratios of 0:0:100, 50:50:0, 40:50:10, 30:60:10, 20:70:10 and 10:80:10 and labeled as samples 102, 201, 301, 401, 501 and 601, respectively. The strips were evaluated for proximate composition, vitamin, mineral content (Fe, K and Zn) physical and sensory qualities using standard methods. The moisture content of the strips ranged from 4.78-6.13%. The Ash contents were below 4% for all the blends. The protein contents increased with an increase in substitution with mungbean flour while sample 101 - extruded strips from 100% cassava flour (reference sample) showed the highest value for carbohydrates (64.64%). The fibre content ranged from 4.04 to 6.15% and fat content reduced with an increased substitution with orange- flesh sweet potato flour (20.94-21.39%). The energy value ranged from 445.70 to 451.18 kcal/100 g which was within the limit recommended for ready-to- eat foods. Vitamin A increased with increased substitution with orange-fleshed sweet potato (35.04- 56.73 mg/kg) which is significantly higher than the control at 2.08 mg/kg. The Iron, potassium and Zinc of the strips ranged from 0.37 to 8.46, 4.13 to 224.28 and 0.87 to 1.83 respectively. Results from the physical evaluation of the strips revealed that the thickness and length of the strips were significantly different (p<0.05) from each other. The result of the sensory evaluation showed that the overall acceptability of the samples produced compared favorably with the control. It may, therefore be concluded from the strength of this work that the extruded strips produced from 30% orange flesh sweet potato flour, 60% mungbean flour and 10% cassava flour could substantially reduce foreign exchange on wheat importation and great contribution towards the use of natural plant materials to improve the nutritional status of the vulnerable groups especially children.
TABLE OF CONTENTS
Title Page i
Declaration ii Certification iii
Dedication iv
Acknowledgements v
Table of Contents vi
List of Tables ix
List of Figures x
List of Plate xi
Abstract xii
CHAPTER 1: INTRODUCTION
1.1 Background information 1
1.2 Statement of the problem 3
1.3 Justification of the study 4
1.4 Objective of the study 4
CHAPTER 2: LITERATURE REVIEW
2.1 Description of Orange-Flesh Sweet Potato Roots 6
2.1.1 Nutritional Value of Orange-Flesh Sweet Potato Roots 6
2.1.2 Health Benefits of Orange-Flesh Sweet Potato Roots 9
2.1.2 Processing and Utilization of Orange-Flesh Sweet Potato Roots 10
2.2 Mungbean Seeds 11
2.2.1 Nutritional Value of Mungbean Seeds 12
2.2.2 Health Benefits of Mungbean Seeds 13
2.2.3 Processing and Utilization of Mungbean Seed 15
2.3 Description of Cassava Roots 17
2.4 Composite Flour and Its Applications in Extruded Snacks 17
2.4 Extrusion Process 19
CHAPTER 3: MATERIALS AND METHODS
3.1 Sources of Raw Material 21
3.2 Processing of Raw Material 22
3.2.1 Processing of Orange-Fleshed Sweet Potato 22
3.2.2 Processing of Mungbean 23
3.3 Formulation of Composite Flour 26
3.4 Proximate Analysis 29
3.4.1 Determination of Moisture Content 29
3.4.2 Determination of Ash Content 30
3.4.3 Determination of Fat Content 31
3.4.4 Determination of Crude Fibre 31
3.4.5 Determination of Crude Protein 31
3.4.6 Determination of Carbohydrate Content 32
3.5.7 Energy Value 33
3.5 Vitamin Analysis 33
3.5.1 Determination of Vitamin A 33
3.5.2 Determination of Vitamin C 34
3.6 Mineral Analysis 35
3.6.1 Determination of Potassium 35
3.6.2 Determination of Iron 35
3.6.3 Determination of Zinc 35
3.7 Physical Composition 36
3.8 Sensory Analysis 36
3.9 Experimental Design 37
3.10 Statistical Analysis 37
CHAPTER 4: RESULTS AND DISCUSSION
4.1 Pictorial representation of the sweet potato, mungbean-cassava strips 38
4.2 Proximate Composition of Sweet Potato, Mungbean, Cassava-Strips 39
4.2.1 Moisture Content 39
4.2.2 Crude Protein Content 41
4.2.3 Fat Content 42
4.2.4 Crude Fibre 42
4.2.5 Ash Content 43
4.2.6 Carbohydrate Content 44
4.2.7 Energy Value 45
4.3 Vitamin Composition of Sweet Potato, Mungbean, Cassava-Strips 46
4.3.1 Vitamin C 46
4.3.2 Vitamin A 48
4.4 Mineral Composition of Sweet Potato, Mungbean, Cassava-Strips 50
4.4.1 Potassium Concentration 50
4.4.2 Iron Concentration 52 4.4.3 Zinc 52
4.5 Physical Characteristics of Sweet Potato, Mungbean, Cassava-Strips 53
4.6 Sensory Evaluation of Sweet Potato, Mungbean, Cassava-Strips 55
CHAPTER 5: CONCLUSSION AND RECOMMENDATIONS
5.1 Conclusion 58
5.2 Recommendations 58
REFERENCES 60
LIST OF TABLES
3.1: Formulation of composite flour (%) 26
3.2: Recipe for production of extruded strips 27
4.1: Proximate Composition of sweet potato, mungbean-cassava strips 40
4.2: Vitamin composition of sweet potato, mungbean-cassava strips 47
4.3: Mineral composition of sweet potato, mungbean-cassava strips 51
4.4: Physical characteristics of sweet potato, mungbean-cassava strips 54
4.5: Sensory evaluation of sweet potato, mungbean-cassava strips 56
LIST OF FIGURES
Figure 3.1: Flow diagram for processing of whole mungbean flour 24
Figure 3.2: Flow diagram for processing of orange fleshed sweet potato flour 25
Figure 3.3: Flow chart for the production of extruded strips 28
LIST OF PLATES
Plate 3.1: Orange flesh sweet potato 21
Plate 3.2: Mungbean seeds 21
Plate 3.3: Orange flesh sweet potato flour 22
Plate 3.4: Mungbean flour 23
Plate 4.1: OFSPF0:MBF0:CF100 58
Plate 4.2: OFSPF50:MBF50:CF0 58
Plate 4.3: OFSPF40:MBF50:CF10 58
Plate 4.4: OFSPF30:MBF60:CF10 58
Plate 4.5: OFSPF20:MBF70:CF10 58
Plate 4.6: OFSPF10:MBF80:CF10 58
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Extrusion is one of the adopted processing techniques by food industries which employ mixing, forming, texturing and cooking to develop a novel food product (Gulati, 2016; Singh et al., 2016). Food extrusion has been widely used to provide ready to eat foods and snacks that depend on the expansion at the die to produce the desired texture and size (Brennan et al., 2013). With the increase in business pressure, companies are searching for new ways to market their products (Gulati, 2016).
In the food processing business, extrusion cooking provides an opportunity to create new products and to improve existing ones. Extrusion cooking can be utilized in developing countries to convert indigestible cereals into products that are both digestible and palatable. The commonly used raw materials in the extrusion process are those that have substantial quantity of protein and starch (Pawar et al., 2014).
Strips are extruded food product done by frying or oven drying. Food extrusion has been widely used to provide ready to eat foods and snacks that depend on the expansion at the die to produce the desired texture and size (Navale et al., 2015). Being ready to eat food, it is important to fortify them (it) with protein sources such as mungbean etc. (Khanam et al., 2013). Flour is a fine powder made by grinding cereal grains or other starchy foods (Figoni, 2010).
Composite flour can be described as a mixture of several flours obtained from roots and tubers, cereals, legumes etc, with or without the addition of wheat flour (Okpala et al., 2013). Composite flour is a name given to any mixture of two or more flour usually obtained from maize, yam, sorghum, cereal, coco yam, wheat etc (i.e., the partial replacement of wheat flour with any other flour). It is conventionally intended to refer to a dilution of wheat flour with other local flour. Composite flour refers to a mixture of two or more flour usually obtained from any of maize, sorghum, rice, cassava etc with or without the addition of wheat (Iwe et al., 2017)
Orange-fleshed sweet potatoes (Ipomoea batatas) have emerged as one of the most promising plant sources of β-carotene, the pro-vitamin A (Mitra, 2012). A 100- 150 g serving of boiled tubers of orange-fleshed sweet potato can supply the daily requirement of vitamin A for young children which can protect them from blindness (Mitra, 2012). Along with the β-carotene, the pro- vitamin A, the young children and adults can also get adequate amount of calories, vitamin C and other micronutrients through increased consumption orange-fleshed sweet potato.
Mungbean (Vigna radiata) as a food legume is an important crop originated from India and cultivated traditionally throughout Asia especially India, Pakistan, Thailand and Philippines (Rani et al., 2018). It has not been widely domesticated in tropical Africa (Idoko and Avavb, 2013). It is been processed to the use as an ingredient in both savory and sweet dishes. There are few varieties of mungbean available of which some have green seeds while others are brown in color. Its seed is a good source of dietary protein which contains high level of folate and iron than that of other legumes. It has high nutritional potentials and has been recently introduced in Nigeria (Onwurafor et al., 2014). The consumption of mungbean proteins can fulfill the essential amino acids requirement with the exception of the sulphur containing amino acids (Zhu et al., 2018).
Additionally, mungbean has been shown to offer some pharmacological benefits such as antitumor effects, as well as antioxidant and antifungal activities (Tang et al., 2014). These beans have a slightly sweet taste and are sold fresh as sprouts and as dried beans. They are high in nutrients like potassium, magnesium and fiber, manganese, folate, copper, zinc and various B vitamins (Ahmad et al., 2017). This study therefore evaluates the quality of extruded strips produced from blends of orange-flesh sweet potato and mungbean flour.
1.2 STATEMENT OF PROBLEM
Naturally, strip is a ready to eat food consumed among adults and children and it contains little or no carotenoid. The deficiency vitamin A which causes poor sight and may result to total blindness is very common to children and adults (Ndong, 2012). Also, the protein content of ready to eat food is very little which provides the body with sufficient nutrients. More so, protein energy malnutrition (PEM) which arises as a result of insufficient consumption of protein and energy is known to result to high rate of death particularly among children.
Economically, the continual production of snacks using imported wheat flour would continue to affect Nigeria’s finances and gross GDP negatively. Notably, several indigenous crops have been investigated as a possible replacement for wheat flour in confectionery production, however, studies on quality characteristics of extruded product from a blend of cassava, sweet potato and mungbean with the intent of exploiting two largely available indigenous crops is yet to be conducted.
Alternative ways of exploiting the commercial, nutritional and health benefits of orange-flesh sweet potato and mungbean was investigated. This study therefore, aimed at finding alternative ways of exploiting the commercial, nutritional and health benefits of sweet potato and mungbean.
1.3 JUSTIFICATION OF THE STUDY
Strip is a convenient and attractive inexpensive food product consumed by both young and old, therefore is needed to be developed, which will be rich in adequate nutrients. This brings about the using of mungbean (Legume) because of its high protein content and adopting root tuber (sweet potato) because of the presence of carotenoid which serves as antioxidants.
Also, the invention of strips produced from blends of orange-flesh sweet potato and mungbean flour will increase the number of the varieties of strips existing in market. It communicates other ways sweet potatoes could be processed thereby increasing the additional value of sweet potatoes. Increased utilization of mungbean is also communicated. More so, this study will assist in making information available to researchers interested in this research area. This study aid in the furnishing the snack producing industries with adequate information on how to process affordable snack from locally available staples, thereby diversifying the use of orange flesh sweet potato and mungbean in food system.
1.4 OBJECTIVES OF THE STUDY
The main objective of this work was to evaluate the quality of extruded strips produced from blends of orange-flesh sweet potato and mungbean flour.
The specific objectives were to:
i. Produce flour from orange-flesh sweet potato and mungbean respectively.
ii. Formulate composite flour of different ratios from orange-flesh sweet potato and mungbean flour.
iii. Produce strips from blends of orange flesh sweet potato and mungbean using manual extruder.
iv. Determine the proximate, vitamin and mineral compositions of the strips produced.
v. Evaluate the sensory attributes of the strips produced.
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