Studies on Microwave-Assisted Extraction of Drumstick Tree (Moringa oleifera) Seed Oil

ABSTRACT

The need for effective and efficient means of oil extraction has been a concern in recent time. Hence, this study aimed at the oil extraction from Moringa oleifera seeds using the Microwave-Assisted extraction method. The extraction process was modeled using Response Surface Methodology (RSM). Also, the evaluation of Moringa oleifera oil as a good feedstock for biodiesel production was carried out.

Oil was extracted from the M. oleifera seed kernel using Microwave-Assisted method and n-hexane as solvent of extraction. D-optimal design of the Response Surface Methodology (RSM) was used to generate 22 experiments for the oil extraction studies. Factors considered for the design were extraction time (4 – 12 min), power (180 – 540 W) and solute-solvent ratio (1:10 – 1:30). The modeling and optimization studies on the oil extraction were carried out using RSM. Properties of the oil extracted were determined using methods of Association of Official Analytical Chemists (AOAC).

The results showed that both RSM model had R2 value of 0.96. RSM predicted an optimum oil yield of 43.60% at optimal condition of 8 min, 540 W and solute-solvent ratio of 1:30. The acid value, specific gravity, iodine value, free fatty acid, refractive index, viscosity, peroxide value, saponification value and cetane number were determined as 3.03 mg/KOH/g; 0.874; 65.89 g I2/100; 1.536 mg/KOH/g; 1.4466; 13.0125 cSt; 8.4 meq/kg; 150.49 mgKOH/g oil and 64.16, respectively.

Thus, the results of this study demonstrated that M. oleifera is a high-yielding oil plant and the oil could serve as feedstock for biodiesel production.

 

 

 

TABLE OF CONTENTS

TITLE PAGE.…………………………………………………...…………………………….…......i

LETTER OF TRANSMITTAL.. ii

CERTIFICATION.. iii

DEDICATION.. iv

ACKNOWLEDGMENTS. v

ABSTRACT.. vi

TABLE OF CONTENTS. vii

LIST OF TABLES. xii

LIST OF FIGURES. xiii

LIST OF PLATES. xiv

CHAPTER ONE.. 1

INTRODUCTION.. 1

1.1 Background Information. 1

1.1.1 Drumstick Tree (Moringa oleifera)1

1.1.2 Microwave-Assisted Method of Extraction. 2

1.1.3 Response Surface Methodology (RSM)3

1.2 Scope of the Study. 4

1.3 Objectives of the Study. 4

1.4 Justification for the Study. 4

CHAPTER TWO.. 5

LITERATURE REVIEW... 5

2.1 Overview.. 5

2.1.1  Wet Rendering Method of Extraction. 5

2.1.2 Mechanical Press Method of Extraction. 5

2.1.3 Solvent Extraction Method. 6

2.2 Moringa oleifera. 6

2.2.1 Moringa oleifera Seed 7

2.2.2 Moringa oleifera Seed Oil10

2.2.3 Moringa oleifera oil: a potential source of biodiesel11

2.3 Microwave Assisted Extraction (MAE)13

2.3.1 Theory and Principle of Microwave heating. 13

2.2.2 Advantages and limitation of Microwave assisted extraction. 17

2.4 Physico-chemical Analysis of the Seed Oil17

2.4.1 Viscosity. 17

2.4.2 Specific Gravity. 17

2.4.3 Density 17

2.4.4 Moisture Content18

2.4.5 Refractive Index. 18

2.4.6 Acid Value. 18

2.4.7 Saponification Value. 18

2.4.8 Iodine Value. 18

2.4.9 Peroxide Value. 19

2.4.10 Cetane Number. 19

2.5 Experimental Design. 20

2.5.1 D-Optimal Design. 20

2.5.2 Response Surface Methodology (RSM)20

CHAPTER THREE.. 21

RESEARCH METHODOLOGY.. 21

3.1 Sample Collection and Preparation. 22

3.1.1 Drying. 22

3.1.2 Milling. 22

3.1.3 Design of Experiment22

3.2 Extraction of the Oil25

3.2.1 Reagents. 25

3.2.2 Equipment25

3.2.3 Oil Extraction Procedure. 25

3.3 Analysis of the Physicochemical Properties of the Oil extracted. 27

3.3.1 Specific Gravity Test27

3.3.2 Refractive Index Test27

3.3.3 Viscosity Test27

3.3.4 Moisture Content Test28

3.3.5 Free Fatty Acid Value (FFA)28

3.3.6 Iodine Value Test (Wij’s method)28

3.3.7 Saponification Value (S.V.) Test29

3.3.8 Acid Value Test29

3.3.9 Peroxide Value Test29

3.3.10 Cetane Number (CN)30

3.3.11 Mean Molecular Mass. 30

3.3.12 High Heating Value (HHV)30

3.3.13 American Petroleum Index (API)30

3.3.14 Diesel Index. 31

3.3.15 Aniline Point31

CHAPTER FOUR.. 32

RESULTS AND DISCUSSION.. 32

4.1: Modelling of the Design of the Extraction of the Moringa Seed oil32

4.2 Optimization of the Extracted Moringa Seed Oil44

4.3 Physiochemical Properties of the Extracted Moringa Seed oil46

CHAPTER FIVE.. 48

CONCLUSION AND RECOMMENDATION.. 48

5.1 Conclusions. 48

5.2 Recommendation. 49

REFERENCES. 50

 

 

LIST OF TABLES

Table 3.1:       Factors and their levels for D-optimal design ------------------------------------- 23

Table 3.2:       Three-Level Factor D-Optimal Design---------------------------------------------24

Table 4.1:       Observed oil yield at various runs conducted by varying the parameter-------35

Table 4.2:       Actual Values and Predicted Values by RSM ------------------------------------36

Table 4.3:       Analysis of variance (ANOVA) of regression equation for Response Surface   Quadratic model -----------------------------------------------------------------------37

Table 4.4:       Regression Coefficients and Significance of Response Surface

Quadratic ------------------------------------------------------------------------------ 38   

Table 4.5:       Physicochemical properties of the Moringa seed oil ---------------------------- 47

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LIST OF FIGURES

Figure 2.1:     Representation of the two heating modes: (a) by convection and (b)

                        by microwave energy (from Neas and Collins, 1988) ----------------------------16

Figure 4.1:     Plot of Predicted Oil Yield against Actual Oil Yield -----------------------------40

Figure 4.2:      Contour and 3-D view of MOSO (Moringa Seed oil) of Yield, Power

and Time at Solute/solvent Ratio of 1:10 ------------------------------------------41

Figure 4.3:      Contour and 3-D view of MOSO (Moringa Seed oil) of Yield, Power

                        and Time at Solute/solvent Ratio of 1:20 ------------------------------------------42

Figure 4.4:      Contour and 3-D view of MOSO (Moringa Seed oil) of Yield, Power

                        and Time at Solute/solvent Ratio of 1:30 ------------------------------------------43

Figure 4.5:     Predicted Optimal Yield by RSM ----------------------------------------------------45

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LIST OF PLATES

Plate 2.1:        Moringa oleifera (a) Dried pods (b) Seed kernel with husks

(c) Seed kernel without husk-------------------------------------------------------- 9

Plate 3.1:        Set up of the Microwave Assisted Extraction ------------------------------------ 26

Plate 4.1:        Extracted Moringa Seed Oil -------------------------------------------------------- 33