STORAGE CHANGES IN SOME CHEMICAL AND PHYSICAL PROPERTIES OF GROUNDNUT AND PALM OILS

TABLE OF CONTENTs

Title page ii
Certification iii
Dedication iv
Acknowledgements v
Title of contents vi
List of table xi
List of figures xii
Abbreviations xiv
Abstract xv

1.0 CHAPTER ONE: INTRODUCTION AND LITERATURE REVIEW
1.1 Introduction 1
1.1.1 Background of Problem 2
1.1.2 Statement of Problems 4
1.1.3 Justification of the Research Work 6
1.1.4 Scope of Work 6
1.1.5 Aim and Objectives 7
1.2 Literature Review 8
1.2.1 Vegetable Oil 8
1.2.1.1 Sources of Vegetable Oil 8
1.2.1.2 Characterization of Fats and Oils 9
1.2.2 Nonglyceride Components of Fats and Oils 12
1.2.2.1 Phospholipids 12
1.2.2.2 Tocopherols and Tocotrienols 14
1.2.2.3 Sterols 17
1.2.2.4 Pigments 17
1.2.2.5 Pesticides 19
1.2.2.6 Trace Metals 20
1.2.3.1 Applications of vegetable oil in Food Preparations 20
1.2.3.2 Industrial Applications 21
1.2.4 Palm Oil 22
1.2.4.1 Palm Oil Composition and Physical Properties 22
1.2.5 Peanut Oil 23
1.2.5.1 Peanut Oil Composition and Physical Properties 24
1.2.6 Vegetable Oil Extraction 25
1.2.6.1 Mechanical Pressing 26
1.2.6.2 Chemical Methods 26
1.2.6.5 Supercritical Fluid Extraction (SFE) 28
1.2.6.6 Steam Distillation 30
1.2.7 Vegetable Oil Refining 30
1.2.7.1 Degumming 31
1.2.7.2 Neutralizing 31
1.2.7.3 Bleaching 31
1.2.7.4 Winterizing 32
1.2.7.5 Dewaxing 32
1.2.7.6 Deodorizing 32
1.2.8 Oxidation of Vegetable Oil 33
1.2.8.1 Mechanisms of Autoxidation in Edible Oil 35
1.2.8.2 Mechanisms of Hydroperoxide Decomposition to form 37
Secondary Oxidation Products
1.2.8.3 Protection against Oxidative Deterioration 39
1.2.8.14 Synergistic Antioxidant Mixtures 48
1.2.9 Fats and Oils Analysis 49
1.2.9.1 N on-Fatty Impurities 50
1.2.9.2 Moisture Analysis 50
1.2.9.3 Trace Metals Analysis 51
1.2.9.4 Soap Analysis 51
2.1.9.5 Composition Analysis 52
1.2.9.6 Saponification Value 53
1.2.9.7 Iodine Value 53
1.2.9.8 Rancidity Analysis 56
1.2.9.9 Peroxide Value 56
1.2.9.10 Anisidine Value 58
1.2.9.11 Smoke Point 58
1.2.9.12 Colour and Appearance 59
1.2.9.13 Lovibond (British Standard) 60
1.2.10 UV Spectroscopy 61
1.2.10.1 Applications of UV spectroscopy for Vegetable Oil analysis 61
1.2.10.2 The Basic Principle of UV Spectroscopy 62
1.2.10.3 Instrumentation and Working of UV Spectroscopy 63
1.2.11 Electrical Conductivity 64

2.0 CHAPTER TWO: MATERIALS AND METHODS
2.1 Materials 67
2.2 Method 68
2.2.1 Determination of Peroxide Value 68
2.2.2 Determination of Iodine Value 69
2.2.3 Determination of electrical conductivity of the vegetable 71
oils
2.2.4 Determination of the absorbance at 233 nm of the UV 71
spectrum
2.2.5 Statistical Analysis 71

3.0 CHAPTER THREE: RESILTS AND DISCUSSION
3.1 Changes in properties of groundnut oil and palm oil over 74
storage
3.2 Correlation studies 78
3.3 Conclusion 88
3.4 Recommendation 89
REFERENCES 90

LIST OF TABLES

Table 3.1 Changes in the Peroxide Value (PV), Iodine Value (IV), Absorbance at
233nm (A233nm) and Electrical Conductivity (EC) of Groundnut Oil
and Palm Oil.

LIST OF FIGURES

Fig. 1: Reaction between fatty acids and glycerol to form triglyceride
Fig. 1.2: general structure of phospholipids

Fig. 1.3: General structure for tocopherol

Fig. 1.4: General structure of tocotrienol

Fig. 1.5: Beta Carotene

Fig. 1.6: Gossypol Fig 3.1 Changes in properties of groundnut oil over storage
Fig 3.2: Changes in the properties of palm oil over storage
Fig 3.3 Plot of Iodine Value (IV) against Peroxide Value (PV) for Groundnut Oil
Fig 3.4: Plot of Iodine Value (IV) against Peroxide Value (PV) for Palm Oil
Fig 3.5: Plot of Iodine Value (IV) against Absorbance at 233nm for Groundnut Oil
Fig 3.6: Plot of Iodine Value (IV) against Peroxide Value (PV) for Palm Oil
Fig 3.7 Plot of Iodine Value (IV) against Electrical Conductivity (EC) for Groundnut Oil
Fig 3.8: Plot of Iodine Value (IV) against Electrical Conductivity (EC) for Palm Oil
Fig 3.9: Plot of Electrical Conductivity (EC) against Absorbance at 233nm for Groundnut Oil
Fig 3.10: Plot of Electrical Conductivity (EC) against Absorbance at 233nm for Palm Oil
Fig 3.11: Plot of Electrical Conductivity (EC) against Peroxide Value (PV) for Groundnut Oil
Fig 3.12: Plot of Electrical Conductivity (EC) against Peroxide Value (PV) for Palm Oil
Fig 3.13: Plot of Peroxide Value (PV) against Absorbance 233nm (A233) For Groundnut Oil
Fig 3.14: Plot of Peroxide Value (PV) against Absorbance 233nm (A233) For Palm Oil

abbreviations
A233nm Absorbance at 233nanometer

EC Electrical conductivity

FA Fatty acid

IV Iodine value

GO Groundnut oil

UV Ultraviolet

PO Palm oil

PV Peroxide value

ABSTRACT

Groundnut oil (GO) and palm oil (PO) were stored in opaque plastic containers at room temperature and the peroxide value (PV), iodine value (IV), UV absorbance at 233nm (A233nm) and the electrical conductivity (EC) were determined every two days over a one-month period. The peroxide value and iodine value were determined using standard AOAC method. The absorbance values were determined with a UV/Vis. spectrophotometer and the electrical conductivity with a conductivity / DO meter. The peroxide value, absorbance and electrical conductivity increased while the iodine values decreased during storage. The changes in properties before and after storage for groundnut oil were: PV( 6.5 -15.5), IV(89.0-86.7 ), A233nm (0.380-0.798 ) and EC(4.06 -6.62). That for palm oil were PV(4.1 – 8.80), IV(52.9 – 49.0), A233nm(0.610-1.350) and EC(6.42-10.00). With respect to the relationship between the parameters, the graphs of IV/PV, IV/A233nm and IV/EC showed strong negative correlations, while the graphs of EC/A233nm, EC/PV and PV/A233nm showed strong positive correlations. The strongest correlation was obtained for the graph of EC/PV for PO with r = 0.989 (p < 0.05). The strong r values obtained for all the plotted graphs means that the chemical parameters used in the study are highly associated. The corresponding regression equations can be used to predict the value of one parameter when the other is known. This might be useful in routine industrial quality control.

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