ABSTRACT
This study evaluated the effect of processing methods (boiling, roasting & sprouting) on the physio-chemical and antioxidant properties of pigeon pea varieties. The result of the proximate composition showed that the boiled white pigeon pea had the highest moisture content and fat content of 11.60% and 5.19% respectively, roasted brown pigeon pea had the highest ash and fibre content of 5.04% and 5.31% and protein value of 24.36% while the sprouted white pigeon pea had the highest carbohydrate value of 60.09%.The mineral composition showed that sprouted white pigeon pea had the highest calcium and iron content of 124.00mg/100g and 11.38mg/100g, respectively while boiled brown pigeon pea had the highest magnesium content of 80.65mg/100g. The result of the functional properties showed that the raw brown pigeon pea had the highest bulk density of 0.71g/g, roasted and boiled white pigeon peas had the highest oil absorption capacity of 2.97mg/ml, roasted white pigeon pea had the highest water absorption capacity and swelling index of 2.25g/ml and 3.51% respectively. Boiled brown pigeon pea had the highest wettability of 59.70% while the raw white pigeon pea had the highest gelatinization value of 84.000c. The anti-nutrient of the two pigeon pea varieties showed that the raw brown pigeon pea had the highest phytate and tannin contents of 2.55% and 0.94Mg/100g respectively while the raw white pigeon pea had the highest trypsin inhibitors content of 9.04Tiu/ng. The result of the anti-oxidant activity of the two varieties of pigeon peas showed that raw brown pigeon pea had the highest FRAP and Total flavonoid 7.86% and 1.02% respectively. The raw white pigeon pea had the highest total phenol of 137.05mg/100g. Boiled brown pigeon pea had the highest ABTS of 141.10% while the boiled white pigeon pea had the highest DPPH value of 103.25µg/ml.The findings of the study showed that the white variety of the pigeon pea had better proximate composition and mineral content and functional properties while the brown had highest anti-nutrients and anti-oxidant activity. Also roasted was observed to improve the nutritional properties of the pigeon peas.
TABLE OF CONTENTS
Cover Page
Title Page ii
Declaration iii
Certification iv
Dedication v
Acknowledgements vi
Table of Contents vii
List of Tables ix
List of figures x
List of plates xi
Abstract xii
CHAPTER 1: INTRODUCTION
1.1 Background information 1
1.2 Statement of the problem 2
1.3 Justification of the study 3
1.4 Objective of the study 3
CHAPTER 2: LITERATURE REVIEW
2.1 Legumes 5
2.1.1 Hard-to-cook Legumes 6
2.2 Pigeon pea 7
2.2.1 Nutritional Value of Pigeon Pea 8
2.2.2 Anti-nutrient factors of pigeon pea 10
2.2.3 Health benefits of pigeon pea 11
2.2.4 Food uses of pigeon pea 12
2.3 Roasting and its effect on legumes 13
2.4 Boiling and its effect on legumes 15
2.5 Fermentation and its effect On Legumes 16
2.6 Germination and its effect on legumes 17
2.7 Antioxidants 18
2.7.1 Mechanism of action of antioxidants 19
2.7.2 Methods of evaluating antioxidant activity 21
CHAPTER 3: MATERIALS AND METHODS
3.1 Sources of Raw Material 24
3.2 Sample preparation 24
3.2.1 Processing of pigeon pea flour 24
3.3 Method of analyses 27
3.4 Functional properties of pigeon pea seeds flour 27
3.4.1 Determination of bulk density 27
3.4.2 Determination of wettability 27
3.4.3 Determination of water absorption capacity 27
3.4.4 Determination of oil absorption capacity (OAC) 28
3.4.5 Determination of gelatinization temperature and time 28
3.4.6 Determination of swelling index (SI) 29
3.5 Proximate composition of pigeon pea seed flour 29
3.5.1 Determination of crude protein 29
3.5.3 Determination of moisture content 30
3.5.4 Determination of ash content 30
3.5.5 Determination of fat content 31
3.5.6 Determination of crude fibre 31
3.5.7 Determination of carbohydrate content 32
3.6 Mineral composition of pigeon pea seeds flour 32
3.6.1 Iron Determination 33
3.6.2 Magnesium Determination 33
3.6.3 Calcium Determination 34
3.7 Antioxidant activity of pigeon pea seed flour 34
3.7.1 Antioxidant activity determined by 2,2-Diphenyl-1-picrylhydrazyl(DPPH) 34
3.7.2 Antioxidant activity determined by Ferric Reducing Antioxidant Power (FRAP) 35
3.7.3 Antioxidant activity determined by ABTS+ radical cation 35
3.8 Antioxidant activity of pigeon pea seed flour 36
3.8.1 Determination extract preparation 36
3.8.2 Determination of total flavonoid 36
3.8.3 Determination of total polyphenol 36
3.9 Antinutrient factors of pigeon pea seed flour 37
3.9.1 Determination of phytate 37
3.9.3 Antioxidant activity determined by ABTS+ radical Cation 37
3.9.3 Determination of trypsin inhibitor 38
3.10 Experimental design 39
3.11 Statistical analysis 39
CHAPTER 4: RESULTS AND DISCUSSION
4.1 Proximate Composition 40
4.2 Mineral Composition 43
4.3 Functional Properties 45
4.4 Antinutrients of two pigeon pea varieties 49
4.5 Anti-oxidant Activity of two pigeon pea varieties 52
CHAPTER 5: CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion 55
5.2 Recommendations 55
REFERENCES 56
LIST OF TABLES
Table 4.1: Proximate composition of two pigeon pea varieties 41
Table 4.2: Minerals composition of the two pigeon pea varieties 44
Table 4.3: Functional Properties of Two Pigeon Pea Varieties 46
Table 4.4: Antinutrients of two pigeon pea varieties 50
Table 4.5: Anti-oxidant Activity of two pigeon pea varieties 53
LIST OF FIGURES
Figure 1: Process flow chart for pigeon pea seeds flour production 25
LIST OF PLATES
Plate 1: Raw white pigeon pea 26
Plate 2: Raw brown pigeon pea 26
Plate 3: Boiled white pigeon pea 26
Plate 4: Boiled brown pigeon pea 26
Plate 5: Sprouted white pigeon pea 26
Plate 6: Sprouted brown pigeon pea 26
Plate 7: Roasted white pigeon pea 26
Plate 8: Roasted brown pigeon pea 26
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Legumes belong to the family Leguminosae also known as Fabaceae. They are seeds enclosed in a pod (Kouris-Blazos and Belski, 2016) which their demand is increasing worldwide because of increased consumer awareness of their nutritional and health benefits (Brigide et al., 2014). Legumes are a good source of protein and B-group vitamins like folate (Kouris-Blazos and Belski, 2016). They are also source of essential minerals (like calcium, phosphorus, potassium, and magnesium) (Brigide et al., 2014; Kouris-Blazos and Belski, 2016) that plays physiological roles in human body (Mogobe et al., 2015). Recent years have seen more people substituting animal protein with vegetable protein; thus, further increasing the demand for legumes as they are the principal source of plant proteins (Brigide et al., 2014).
Pigeon pea (Cajanus cajan (L) Millsp) also known as redgram, congo pea, gungo pea, and no-eye pea belongs to the family of Leguminosae (Wu et al., 2009). It is a good source of protein, fiber, and minerals making it a good crop for the production of protein and fiber-fortified foods (Syed and Wu, 2018). Majority of the protein found within pulse seeds is in the form of storage proteins classified as globulins, albumins, and glutelins. Globulins make up about 65 % of the total protein in pigeon pea (Roy et al., 2010).Pigeon pea contains fatty acids. The main saturated fatty acid in pigeon pea is the palmitic acid which constitutes 15 to 25 % in the neutral lipids, 20 to 40 % in the glycolipids, and 26 to 30 % in the phospholipids (Ade-Omowaye et al., 2015). Pigeon pea is a good source of minerals like phosphorus, magnesium, iron, calcium, sulphur and potassium but low in sodium (Kunyanga et al., 2013). Pigeon pea have antioxidant potential, hypocholestrolemic, antimicrobial, anti-inflammatory and hepatoprotective effect (Saxena et al., 2010).
Processing of food crops is aimed at generating products stable in terms of shelf-life, nutrition and palatability (Fasoyiro et al., 2012). The methods involved in food processing vary widely, and the nutritive value of food may be improved or diminished depending on the methods employed (Otemuyiwa et al., 2018). Pigeon pea seeds like other legumes are usually consumed after processing either through boiling, roasting etc. Processing of this crop using appropriate method is vital, not only because it improves palatability of foods but also because it reduces the levels of anti-nutrients and toxins which impairs bioavailability of nutrients (Fasoyiro et al., 2012).
Antioxidants are indispensable group of food additives mainly because of their unique properties of extending the shelf-life of food products without any adverse effect on their sensory or nutritional qualities (Alam et al., 2012).Antioxidants are basically classified into two major types based on their source, i.e., natural and synthetic antioxidants (Pal et al., 2014). Antioxidant compounds like phenolic acids, polyphenols and flavonoids scavenge free radicals such as peroxide, hydro peroxide or lipid peroxyl and thus, inhibit the oxidative mechanisms that lead to degenerative diseases (Emad, 2014).
1.2 STATEMENT OF THE PROBLEM
In spite of the nutritional advantages of pigeon pea seeds. This legume is highly underutilized as food. Protein deficiency is a pathological conditions arising from inadequate consumption of protein, this results to kwashiorkor (Hamidu et al., 2013) and mainly affects low income families that can’t always afford animal protein. Pigeon pea can contribute in eradicating protein deficiency and other nutrient related health problems. presently research has been carried out on the effect of processing methods (boiling, roasting, fermentation and germination) on the physiochemical and antioxidant properties of some pigeon pea varieties is scarce. Processing of food crop can results to nutrient loss or again either by degradation which can occur by chemical changes such as oxidation or by leaching into the processing medium or by opening the food matrix to release the nutrients. Processing of pigeon pea and the determination of the physicochemical and antioxidant properties will add to knowledge on its nutrients and antioxidant contents and utilization.
1.3 JUSTIFICATION OF THE STUDY
Processing of pigeon pea seeds into flour will enhance its utilization in production of value added products and in turn enhance its consumption particularly among the low income families that can’t always afford animal protein due to its high cost. This will also contribute in curbing protein deficiency in Nigeria and as well reduce over dependency on imported flour for production of confectionaries, thereby saving Nigeria’s external currency earnings and reserve. Findings of this study will be of tremendous benefit to food professionals and as well be incorporated in Nigeria’s food composition table so that provision of dietary guidance using such food composition database as a reference material could be more effective. This study will provide information on the best processing method that will ensure adequate nutrient intake from pigeon pea seeds.
1.4 OBJECTIVES OF THE STUDY
The main objective of this study was to evaluate the effect of processing methods on the physiochemical and antioxidant properties of two pigeon pea varieties.
The specific objectives of the study were to:
i. Process two varieties of pigeon pea seeds using different methods (boiling, roasting, raw and sprouting)
ii. Determine the functional properties of the processed flours
iii. Determine the physicochemical properties of the processed flours
iv. Evaluate the antioxidant potential of the flour
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