EXTRACTION OF PALM OIL FROM PALM MESOCARP USING

SUB-CRITICAL R134a

ANA NAJWA MUSTAPA

UNIVERSITI TEKNOLOGI MALAYSIA

iii

To my beloved family and friends

iv

ACKNOWLEDGEMENT

I would like to thank all people who have assisted me in the completion of this project. I deeply thank Prof. Dr. Zainuddin Abdul Manan, my main supervisor, for his invaluable advice, discussions and professional support during the course of this work. I also wish to express thank and my appreciation to my co-supervisor Prof. Ir. Dr. Mohd. Omar bin Ab Kadir, for his guidance, creative idea and for providing the facilities for conducting extraction experiments in Special Equipments Laboratory at Environmental Technology Division, Universiti Sains Malaysia (USM). I am also indebted to him for providing the financial supports for analysis of Scanning Electron Microscope (SEM) and Gas Chromatography (GC).

I would like to thank Assoc. Prof Dr. Nik Norulaini for her guidance, valuable idea and for helping me with practical matters concerning this thesis. I would like to thank my colleagues, Dr. Mohd Azizi Che Yunus, Wahyu Setianto, Abu Hanifah and Anuar Omar for their pleasant and stimulating discussions and invaluable practical help in completing my experimental work and this thesis.

I want to express my appreciation and love for my family. To my parents Mustapa Mohammad and Wan Naimah Wan Yusoff, my brothers Ameer Hazim and Aidy Asyraf, thank you so much for the support, love and patience. I could not survive during the hardships without them. Special appreciations and thanks to all my friends especially Sabariah Samsun, Hazana Razali, Shalima and Kavitha who provided emotional, logistical and physical support, and for their cheerfulness. Finally, I express my thanks to those who have inspired and encouraged me directly or indirectly throughout the project. Your contributions are so precious to me.

v

ABSTRACT

Experiments involving extraction of palm oil from treated palm fleshy

mesocarp were carried out using a dynamic method to determine palm oil yield and

solubility in sub-critical 1,1,1,2-tetrafluoroethane (R134a). Effects of crucial process

parameters including R134a pressure, temperature and flowrate as well as sample

pre-treatment on palm oil yield and solubility were examined. R134a pressure was

varied from 60 to 100 bar whereas temperature, from 40o to 80oC. The palm oil

extracts were analyzed using gas chromatography (GC) analysis and ultraviolet-

visible (UV-Vis) Spectrophotometer to determine the compositions of fatty acids and

β-carotene extracted. The experiments were designed using response surface

methodology (RSM) to model the extraction yield of palm oil as a function of

pressure and temperature. The experimental palm oil solubility data was

successfully correlated using Chrastil model, density-based model and temperature-

pressure (T-P) model by means of multiple regressions for prediction purposes. The

coefficient of determination, R2, values for the empirical models were 93.68%,

96.38% and 93.97%, respectively. Analysis of variance (ANOVA) showed that palm

oil yields and solubility were highly temperature-dependent and moderately pressure-

dependent, with p-value of <0.05 at 95% significant level. Sub-critical R134a was a

suitable solvent for palm oil extraction since the degree of extraction (defined as the

ratio of yield by R134a to Soxhlet) was 93.34%. Substantial oil yields and solubility

at much lower pressure than those required by supercritical carbon dioxide proved

that sub-critical R134a is an alternative solvent for palm oil extraction even though

supercritical carbon dioxide leads to higher oil yields.

vi

ABSTRAK

Pengekstrakan minyak kelapa sawit daripada mesokarpa buah sawit

dilakukan secara eksperimen melalui satu kaedah dinamik untuk menentukan

keterlarutan minyak sawit dan kebolehan pengekstrakan di dalam subgenting

(1,1,1,2-tetrafluoroethane) R134a dengan mengambil kira kesan parameter proses

termasuk tekanan, suhu, kadar alir R314a dan rawatan sampel. Tekanan bagi R134a

diubah dari 60 ke 100 bar manakala suhu adalah dari 40o ke 80oC. Ekstrak minyak

sawit yang dianalisis melalui kromatografi gas dan Spektrofotometer UL-Nampak

untuk menentukan komposisi asid lemak dan β-carotina yang diekstrak. Eksperimen

telah direkabentuk melalui kaedah permukaan sambutan (RSM) untuk permodelan

hasil pengekstrakan minyak sawit terhadap suhu dan tekanan sistem. Data

keterlarutan minyak sawit yang diperolehi telah berjaya berkolerasi menggunakan

model Chastil, model berasaskan ketumpatan dan model suhu-tekanan (T-P) melalui

kaedah regresi berganda. Nilai pekali penentuan, R2, bagi setiap model empirikal

tersebut adalah 93.68%, 96.38% and 93.97%. Analisis varians (ANOVA)

menunjukkan keterlarutan dan hasil ekstrak minyak sawit adalah sangat dipengaruhi

oleh suhu dan separa dipengaruhi oleh tekanan apabila p-value<0.05 pada 95% tahap

kepentingan bagi kedua-dua faktor suhu dan tekanan. Keputusan eksperimen

menunjukkan pelarut R134a boleh diaplikasikan proses pengekstrakan minyak sawit

memandangkan darjah pengekstrakannya terhadap pengekstrakan Soxhlet mencapai

sehingga 93.34%. Keterlarutan dan hasil pengekstrakan yang tinggi walau pada

tekanan rendah membuktikan pelarut R134a boleh diaplikasikan dalam

pengekstrakan minyak sawit. Bagaimanapun, pelarut karbon dioksida lampau

genting memberikan kadar ekstrasi yang lebih tinggi daripada pelarut subgenting

R134a.

vii

TABLE OF CONTENTS

CHAPTER TITLE PAGE

THESIS STATUS DECLARATION

SUPERVISORS DECLARATION

DECLARATION ON COOPERATION

TITLE PAGE i

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES xii

LIST OF FIGURES xiv

LIST OF ABBREVIATIONS / SYMBOLS /

NOTATIONS

xvii

LIST OF APPENDICES xxi

1 INTRODUCTION

1.1 Outlook of Palm Oil Industry 1

1.2 Palm Oil Extraction

1.2.1 Conventional Processing

1.2.2 Carotenoids in Palm Oil

3

4

6

1.3 Supercritical Fluid Extraction (SFE)

Technology

7

1.4 Advantages of SFE Technology 7

viii

1.5 Problem Background 9

1.6 Problem Statement 10

1.7 Research Objectives 11

1.8 Scope of Work 11

1.9 Research Contributions 12

1.10 Thesis Outline 13

2 FUNDAMENTAL THEORY

2.1 Introduction 15

2.2 Characterization of Palm Oil 16

2.2.1 Triglycerides and Fatty Acids 17

2.2.2 Minor Components in Palm Oil 19

2.2.3 Carotenes 20

2.3 Determination of Solvent 21

2.3.1 1,1,1,2-Tetrafluoroethane (R134a) as a

Solvent

25

2.3.2 Characteristics of R134a 26

2.3.3 R134a Solvating Power 27

2.4 Solute-Solvent Compatibility 28

2.5 Sub-critical Condition 29

2.6 Principles of Sub- and Supercritical Extraction

Process

31

2.6.1 Physical Properties of Sub-critical Fluid 33

2.7 Method of Solubility Measurement 36

2.7.1 Dynamic Method 36

2.8 Important Parameter Affecting Supercritical

Extraction Process

38

2.8.1 Moisture Content 38

2.8.2 Sample and particle size 40

2.8.3 Solvent Flowrate 41

2.8.4 Pressure 42

2.8.5 Temperature 42

ix

2.9 Profile of extraction curves 43

2.10 Conclusion 45

3 LITERATURE REVIEW

3.1 Extraction of Vegetable Oils Using SFE

Technology

46

3.1.1 Extraction of Palm Oil 47

3.2 Solubility of Solutes in Supercritical Fluids 48

3.2.1 Solubility of Vegetables Oils in

Supercritical Fluids

50

3.3 Reviews on Extraction with R134a 55

3.4 Extraction and Recovery of Active Compounds 58

3.4.1 Carotenes 58

3.5 Response Surface Design 61

3.6 Correlation for Solubility Prediction 63

3.7 Conclusion 65

4 METHODOLOGY

4.1 Introduction 66

4.2 Selection of Operating Parameters 67

4.3 Sampling and Materials 69

4.4 Sample Pre-treatment 69

4.4.1 Uncooked-chopped (UC) palm fruits 70

4.4.2 Cooked-Flaked (CF) palm fruits 71

4.4.3 Uncooked-Flaked (UF) palm fruits 72

4.5 Determination of Moisture Content 73

4.6 Soxhlet Extraction 73

4.7 Solubility Measurement 74

4.7.1 Flowrate Selection 75

4.7.2 Correlation of Solubility Behaviour 75

4.8 Experimental Design for Response Surface 76

4.9 Sub-critical R134a Extraction 77

4.9.1 Expression of Results 78

x

4.9.2 Sub-critical Extraction Procedure 79

4.10 Analysis of β-Carotene Concentration 81

4.10.1 Expression of Results 81

4.11 Fatty Acid Methyl Esters (FAME) Analysis 82

4.11.1 Materials and Apparatus 82

4.11.2 Preparation of Fatty Acid Methyl Esters

(FAME)

82

4.11.3 Analysis Method 83

4.11.4 Expression of Results 83

5 RESULTS AND DISCUSSION

5.1 Introduction 85

5.2 Moisture Content of Treated Palm Mesocarp 86

5.3 Optimum Flowrate for Solubility Studies 87

5.4 Extraction of several prepared sample 90

5.4.1 Soxhlet Extraction 91

5.4.2 Sub-critical R134a Extraction 91

5.4.3 Scanning Electron Microscope (SEM) of

Samples

94

5.5 Extraction Yield of Palm Oil 97

5.5.1 Effect of Pressure 98

5.5.2 Effect of Temperature 106

5.5.3 Effect of R134a Flowrate 109

5.6 Effect of Pressure and Temperature on the

Solubility Performance

112

5.6.1 Pressure Effect on Solubility 113

5.6.2 Temperature Effect on Solubility 114

5.7 Comparison with Literature 116

5.8 Comparison between R134a and CO2 119

5.8.1 Extraction Performance 120

5.8.2 Economic Factor 124

5.9 Solubility of β-carotene 125

5.10 Fatty Acid Methyl Esters (FAME) Analysis 130

xi

5.10.1 Fatty Acids Composition 133

5.11 Solubility Behaviour Modeling 136

5.11.1 Density-based Model 136

5.11.2 T-P-based Model 140

5.12 Response Surface Modeling of Palm Oil Yield 142

5.13 Statistical Analysis 145

6 CONCLUSIONS AND RECOMMENDATIONS

6.1 Conclusion 147

6.2 Recommendations for Future Work 149

REFERENCES 151-163

APPENDICES A - E 164-170

xii

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Fatty Acid Composition of Malaysian Palm Oil (Fui,

1996)

18

2.2 Triglycerides composition of Malaysian palm oil

(Fui, 1996)

18

2.3 Physical properties of carotenes 21

2.4 Advantages and disadvantages of the most

commonly used supercritical fluids (De Castro,

1994)

22

2.5 Various Solvent as SFs with Critical Properties 23

2.6 Physical properties of selected solvents (Corr, 2002) 24

2.7 Dielectric constants and dipole moments for various

solvent

28

2.8 The advantages and disadvantages of dynamic

method of solubility measurement

37

3.1 Literature survey of the previous study on the

application of R134a solvent in the SFE technology

57

3.2 Literature survey solubility measurements of β-carotene

and in supercritical CO2 60

3.3 Solubility of β-carotene in R134a 61

4.1 Sub-critical extraction condition 68

4.2 Treatment and Coded-levels of the independent

variables for Full 32 Factorial design

76

4.3 Experimental design for Full 32 Factorial design 77

5.1 Moisture content of different types of palm

mesocarp samples

87

xiii

5.2 Characteristics of solubility and yield at various

flowrate at 60 bar and 80oC

88

5.3 Oil yield by Soxhlet extraction for different sample

pre-treatment

91

5.4 Solubility of palm oil from several prepared palm

mesocarp

93

55 Palm oil yield percentages at various pressure and

temperature

97

5.6 Solubility and extraction yield of palm oil in subcritical

R134a at 40o, 60o and 80oC and up to 100 bar 112

5.7 Characteristics of CO2 and R134a at several

pressure-temperature

122

5.8 Comparison of costs between CO2 and R134a 124

5.9 Standard of fatty acids characteristics 131

5.10 Fatty acids standard obtained using GCMS 133

5.11 Constant for Chrastil equation 137

5.12 Model parameters estimated for several vegetable

oils using Chrastil model

138

5.13 Comparison between Chrastil and non-empirical

equation

140

5.14 Operating conditions and experimental and predicted

data from multiple regression of T-P-based model

142

5.15 Experimental conditions and estimation results for

palm oil yield by Response Surface Design

143

5.16 Regression coefficient for palm oil yield 143

xiv

LIST OF FIGURES

FIGURE NO. TITLE PAGE

1.1 Comparison of palm oil with others oil crops for year

2006 (MPOC and MPOB, 2007)

2

1.2 A Comparison of export of palm oil between Malaysia and

others producer (MPOC and MPOB, 2007)

2

1.3 Anatomy of oil palm fruit (MPOC and MPOB, 2007) 3

1.4 Flow diagram of conventional processing 4

2.1 Crude palm oil composition 17

2.2 Classification of minor constituent in crude palm oil 20

2.3 Molecule structure of 1,1,1,2-tetrafluoroethane 26

2.4 An example of phase diagram of pure indicating a point

of supercritical and subcritical region

30

2.5 Phase diagram of a pure material and the thermodynamic

state of various separation processes (Rizvi, et. al,1994) 32

2.6 Flow diagram of a separation process (Brunner, 2005) 33

2.7 Reduced density–reduced pressure including several

reduced temperature for supercritical and subcritical region

(De Castro, 1994)

34

2.8 Solvent power and transport properties of near critical

and supercritical fluids (Griffith, 2001)

35

2.9 Influence of sample size and extraction time on the

efficiency of SFE of PCB-52 with CO2 (De Castro,

1994)

40

2.10 Extraction curves for artemisinin from Artemisia annua

leaves, indicates the profile of overall extraction curves

(Quispe-Condori et al., 2005)

44

xv

3.1 Solubility of components of homologous series in

SCCO2 (Brunner, 1994)

49

3.2 Solubility of lipids in sub-critical R134a as a function

temperature 50

3.3a

3.3b

Solubility of caffeine in supercritical CO2, Solubility of

naphthalene in ethylene (Brunner, 1994) 51

3.4 Solubility of Evening Primrose Oil (EPO) in compressed

CO2 as a function pressure at various temperatures. □-20, Δ-

35, ○-50oC. Source: Lee et al., (1999) 52

3.5 Solubility of triglycerides of palm oil in various gases as a

function of the difference between system temperature and

the critical temperature of the solvents (Brunner, 1994) 54

3.6 Correlation of Cupuaçu fat solubility (C, g/l) as a function

of solvent density (d, g/l) (Azevedo et al., 2003) 64

4.1 Sample of Uncooked-Chopped (UC) Palm Mesocarp 70

4.2 Sample of Cooked-Flaked (CF) Palm Mesocarp 72

4.3 Sample of Uncooked-Flaked (UF) Palm Mesocarp 72

4.4 Schematic diagram of the R134a extraction apparatus (A:

R134a cylinder, B: Chiller (set at -5oC), C: HPLC Pump, D:

Oven (set the extraction temperature 40-80oC). E:

Extraction cell, F: Back-pressure regulator (BPR), G: Vial

collector and H: Mass Flow Meter 80

5.1 Independency of solubility on flowrates 89

5.2 Time needed to extract maximum achievable oil as a

function of R134a flowrate

89

5.3 Effect of sample pre-treatment on palm oil extraction at

60 bar and 80oC.

92

5.4 SEM image of chopped palm mesocarp after extraction

of oil. The broken cells and depleted of oil are

provedcomponents

95

5.5 SEM image of chopped palm mesocarp after extraction.

The deflated cells observed

95

5.6 SEM image of chopped palm mesocarp. Starch

xvi

aggregates in intact cell. 96

5.7 SEM image of cooked palm (CF) mesocarp after

extraction

96

5.8 Effect of pressure on palm oil extraction at 40oC as a

function of extraction time

99

5.9 Effect of pressure on palm oil extraction at 60oC as a

function of extraction time

99

5.10 Effect of pressure on palm oil extraction at 80oC as a

function of extraction time

100

5.11 Effect of pressure on palm oil extraction at 40oC as a

function of mass of R134a used

105

5.12 Effect of pressure on palm oil extraction at 60oC as a

function of mass of R134a used

105

5.13 Effect of pressure on palm oil extraction at 80oC as a

function of mass of R134a used

106

5.14 Effect of temperature on palm oil extraction at 60 bar as

a function of extraction time

107

5.15 Effect of temperature on palm oil extraction at 80 bar as

a function of extraction time

107

5.16 Effect of temperature on palm oil extraction at 100 bar

as a function of extraction time

108

5.17 Effect of flowrate on palm oil extraction at 60 bar and

80oC

110

5.18 Effect of flowrate as a function of extraction time at 60

bar and 80oC

111

5.19 Palm oil solubility as a function of pressure at different

temperatures

113

5.20 Palm oil solubility as a function of temperature at

different pressure

115

5.21 Solubility comparison between palm oil and several oils

and fats at 60 bar

117

5.22 Relative deviation between palm oil and several oils

and fats

118

xvii

5.23 Comparison of palm oil solubility in terms of reduced

pressure

118

5.24 Comparison of extraction performance between

supercritical CO2 and sub-critical R134a at 100 bar and

40oC

120

5.25 Comparison of extraction performance between

supercritical CO2 and sub-critical R134a at 80 bar and

60oC

123

5.26 Typical curve of β-carotene concentration in oil fraction

at 80oC

126

5.27 Solubility of β-carotene in sub-critical R134a as a

function of pressure

128

5.28 Comparison of carotene solubilities among several works 129

5.29 GC chromatogram profile of standard solution for fatty

acid

131

5.30 GCMS chromatogram for standard fatty acid solution 132

5.31

GC chromatogram of fatty acids at 80 bar and 80oC.

Peaks: (1) C14:0 (myristic acid), (2) C16:0 (palmitic

acid), (3) C18:2 (linoleic acid), (4) C18:1 (oleic acid),

(5) C18:0 (stearic acid).

134

5.32 Comparison between experimental and predicted

solubility by Chrastil’s equation

137

5.33 Comparison between experimental and predicted

solubility by non-empirical density model

139

5.34 Regression plot on palm oil solubility as a function of

pressure

141

5.35 Pareto chart indicates the significant level for each

parameter

144

5.36 Extraction yield of palm oil as a function of pressure

and temperature at 3ml/min; a) response surface b)

contour plots

145

xviii

LIST OF ABBREVIATIONS / SYMBOLS / NOTATIONS

Abbreviations

AAD - Average absolute deviation

AAPD - Average absolute percentage deviation

CF - Cooked-flaked

CFC - Chlorofluorocarbons

CO2 - Carbon dioxide

CPO - Crude palm oil

C12:0 - Lauric acid

C14:0 - Myristic acid

C16:0 - Palmitic acid

C16:1 - Palmitoleic acid

C18:0 - Stearic acid

C18:1 - Oleic acid

C18:2 - Linoleic acid

C18:3 - Linolenic acid

C20:0 - Arachidic acid

DG - Diacylglycerols

EPO - Evening Primrose oil

FAME - Fatty acid methyl esters

FDA - Food and Drug Administration

FFA - Free fatty acids

FFB - Fresh fruit bunch

GC - Gas chromatography

GCMS - Gas chromatography mass spectrophotometer

GRAS - Generally Recognised as Safe

HC - Hydrocarbons

xix

HCFC - Hydroclorofluorocarbon

HFCs - Hydroflourocarbons

HPLC - High-pressure liquid chromatography

MDI - Metered dose inhaler

MG - Monoglycerides

N2O - Dinitrogen Monoxide

OF - Objective function

Pc - Critical pressure

Pr - Reduced pressure

PCB - Polychlorobiphenyls

POO - Palmitoyl-dioleoyl-glycerol

POP - Dipalmitoyl-oleoyl-glycerol

PPO - Dipalmitoyl-oleoyl-glycerol

SCF - Supercritical fluid

SEM - Scanning Electron Microscope

SFE - Supercritical fluid extraction

SF6 - Sulphur Hexafluoride

TIC - Total Ion Chromatogram

TG - Triglycerides

UC - Uncooked-chopped

UF - Uncooked-flaked

VOC - Volatile organic compound

Symbols

α - Alpha

β - Beta

μ - Dipole moment

ε - Dielectric constant

π* - Polarity/polarizability parameter

a1 - Constant depends on total heat of reaction

a2 - Constant depends on molecular weights of solute and fluid

c - Solubility

k1 - Slope of the solubility isotherm

xx

∆H - Heat of reaction

ρf - Density of fluid

Y - Total oil yields in sub-critical as g oil/g sample

aij - Coefficient of the function

P - Absolute pressure

PC - Critical pressure

Pr - Reduced pressure ≡ P / PC

T - Absolute temperature in Kelvin

TC - Critical temperature

Tr - Reduced temperature ≡ T / TC

S - Palm oil solubility (g oil/kg R134a used)

R2 - Regression coefficient

ρ - R134a density

Notations

Subscripts

calc - Denotes calculated value

exp - Denotes experimental value

f - Denoted fluid

xxi

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Calculated density of R134a from data in

Tillner-Roth and Baehr (1994)

164

B Calculation of viscosity of R134a 165

C An example of Total Ion Chromatography

(TIC). The figure show the TIC of C16:0

167

D Percentages of fatty acids at various

pressure and temperature

168

E Statistical Analysis Results 169

CHAPTER 1

INTRODUCTION

1.1 Outlook of Palm Oil Industry

Palm oil is an important source of food and a major source of lipid. Steady

increase in the world population increases the demand for palm oil as an important

source of edible oils and fats. Almost 90% of the world palm oil production is

traded as edible oils and fats. Palm oil also account for about 13% of the total world

production of oils and fats, and is expected to overtake soybean oil as the most

important vegetable oil (Sundram et al., 2003). This phenomenon arises due to the

unique characteristics of palm oil, particularly its potential health benefits.

Therefore, high yields of the oil palm throughout the year are essential to meeting

the high global expert market demand.

The oil palm produces the highest tonnage of oil per hectare per year with

minimum use of land see Figure 1.1. The Figure 1.1 shows a comparison of oil palm

with other major oil crops in the world. The average yield of oil palm produced in a

year was 3.74 tonne/hectare/year and contributed to 31.11% of the world’s total oil

crop production. This followed by soybean oil (29.78%), rapeseed oil (15.50%) and

sunflower oil (9.37%) (MPOC and MPOB, 2007).

2

Figure 1.1: Comparison of palm oil with other oil crops for year 2006

(MPOC and MPOB, 2007)

Currently, most of the world’s production of palm oil comes from South-East

Asia, in particular Malaysia and Indonesia (Sundram et al., 2003). Malaysia and

Indonesia continues to be the largest contributors, with the respective average of

51% and 36% production of palm oil between the periods of 2002-2006 as shown in

Figure 1.2 (MPOC and MPOB, 2007). Therefore, as the biggest producer and

exporter of palm oil and palm oil products, Malaysia plays an important role in

fulfilling the growing global needs for oils and fats.

Ann

ual E

xpor

ts o

f Pal

m O

il (m

ilton

nes)

Indonesia Others Malaysia

Figure 1.2: A Comparison of export of palm oil between Malaysia and other

producer (MPOC and MPOB, 2007).

3

1.2 Palm Oil Extraction

Palm oil is produced from the fruit of oil palm tree (Elaeis Guineensis) which

originated in West Guinea. The average weight of each bunch varies between 10-

30kg and individual fruits are generally in the range of 8-20g. As shown in Figure

1.3, the individual fruit are made up of an outer skin (the exocarp), a pulp

(mesocarp) containing the palm oil in a fibrous matrix; a central nut consisting of a

shell (endocarp); and the kernel (the seed), which itself contains an oil, quite

different from palm oil, resembling coconut oil (Sundram et al., 2003).

Palm mesocarp

Kernel shell Exocarp

Palm kernel

Figure 1.3: Anatomy of oil palm fruit

(MPOC and MPOB, 2007)

A unique feature of the oil palm is that it produces two types of oil - palm oil

is extracted from mesocarp, and palm kernel oil is extracted from the palm kernel.

Palm oil is rich in carotenoids, (pigments found in plants and animals) from which it

derives its deep red colour, and the major component of its triglycerides is the

palmitic acid which is a saturated fatty acid; hence it is a viscous semi-solid, under

ambient typical condition and becoming solid fat in temperate climates.

4

1.2.1 Conventional Processing

The common technique of extracting palm oil from fruits in Malaysian palm

oil milling is by mechanical pressing using hydraulic press or screw press. In the

pre-processing stage, fruits bunches are collected from the plantation and delivered

to the mill as soon as possible to avoid the increase of undesired content i.e. free

fatty acid (FFA) due the enzymatic reaction. The oil extraction process involves

several steps namely sterilization, bunch stripping or threshing, digestion of fruits,

followed by extraction of oil and clarification and purification as shown in Figure

1.4.

Bunch Sterilization

Bunch Threshing

Figure 1.4: Flow diagram of conventional palm oil extraction process.

SHELL & FIBRE

EMPTY BUNCH

Fruit Digestion

NUT & FIBRE Pulp Pressing Nut Recovery

Oil Clarification Nut Polishing

Nut CrackingOil Purifying

Kernel Separation Oil Drying

Kernel Storage Oil Storage

5

Fresh fruit bunches are steam sterilized at around 140oC for a period of 75 to

90 minutes. The sterilizing or steaming of the fruits are to facilitate separation and

threshing of bunches to free the palm fruit. However, the main objectives are to

deactivate hydrolytic enzymes responsible for the breakdown of oil to free fatty acid,

to coagulate and facilitate the breaking of oil cells. In the bunch threshing step, the

fruits are stripped and separated from fruit bunches in a rotary drum. Fruits are

knocked out of the bunch as they passed through the stripper. The detached fruits

are collected and conveyed into the digester (Mustapa, 2004).

Digestion involves the meshing up of the fruits under steam-heated

conditions and pressing out the crude palm oil. Generally, twin-screw press is used

to press out the oil from the digested mesh. The crude oil is further purified and

dried for storage. The solid wastes from the milling operations are empty fruit

bunches, palm fibre, and palm kernel shell. The residue from the press consists of a

mixture of fibre and palm nuts which were then processed to produce palm kernel.

Normally, the extraction rates of fresh fruit bunch are dependent on the size and

weight of fruits. Fruits weighing more than 20 kilograms would typically an

extraction rate of between 19–21%, whereas fruits weighing is less than 10

kilograms, typically will have oil extraction rate of about 15–16% (Mustapa, 2004).

The best quality crude palm oil quality must have FFA percentage of less

than 5% whereas the moisture content is less than 0.1% and the percentage of dirt is

not more than 0.01%. The highly rated commercial oil palm fruit is type Tenera, a

hybrid of Durra and Pisifera (Baryeh, 2001 and Sundram et al., 2003). Tenera has a

shell of less than 3mm thick 60-96 % mesocarp, 3-20% shell and 3-15% kernel

making it tenable to high extraction yield.

6

1.2.2 Carotenoids in Palm Oil

One of the uniqueness of palm oil is, its high content of carotenoids. Typical

crude palm oil contains 500-700ppm of carotenes. Together with tocopherols,

carotenoids contribute to the stability and nutritional value of palm oil. Therefore,

the extraction and recovery of the carotenes would give a significant added value to

the oil. Unfortunely, these valuable carotenes are destroyed and removed during

conventional palm oil refining to give a light coloured oils as required consumers,

rendering them unavailable for recovery and use (Ooi et al., 1996 and Gast et al.,

2001).

Besides, the conventional processing of palm oil also leaves high content of

carotenoids in pressed palm fibers. The pressed palm fibers found are a good source

of carotene. The residual palm fibers from palm oil production contain between 4000

and 6000 ppm of carotenoids, six times higher than that found in crude palm oil

(Franca and Meireless, 1997). Until now, the residue is a waste product which is

typically burned in palm oil mills, regardless of the high carotenoid contents.

(Birtigh et al., 1995 and Franca and Meireless, 1997).

A number of methods have been developed to recover and extract

carotenoids from crude palm oil including solvent extraction, adsorption,

precipitation and transesterification-distillation. However, to-date, only

transesterification-distillation and transesterification-solvent extraction have been

scaled-up to industrial practise. These methods are energy-intensive processes since

the esters must be vacuum-distilled and the carotenes may undergo thermal

degradation. As an alternative SFE technology was introduced more than 20 years

ago to take advantage of the lower operating temperature preventing degradation of

carotene during extraction. The SFE method has wide attention due its advantages

over traditional processing technology.

7

1.3 Supercritical Fluid Extraction (SFE) Technology

Supercritical fluid extraction (SFE) is a powerful technique in a separation

process which uses a supercritical fluid (SCF) as a solvent. The behaviour of

supercritical fluids observation was first observed and reported by Baron Cagniard

de la Tour in 1822. From his early experiments, the critical point of a substance was

first discovered. However, the first workers to demonstrate the solvating power of

supercritical fluids for solids were Hannay and Hogarth in 1879. They found that

increasing the pressure caused the solutes to dissolve and that decreasing the

pressure caused the dissolved materials to precipitate as a “snow”. This behaviour is

fundamental to the understanding of the supercritical fluids extraction (SFE)

technology (Taylor, 1996).

A pure component is said to be in supercritical state when its temperature and

pressure are higher than the critical values (Tc and Pc, respectively). The fluid

above the Tc and Pc cannot be liquefied regardless of the applied pressure. It has

desirable properties that make it suitable for challenging an extraction process i.e.

changes with a slight variation in pressure and temperatures near the critical point.

The fluid exhibits high density similar to liquids, and low viscosity similar to gases.

The high densities of SCFs contribute to greater solubilization of compounds while

low viscosity enables penetration in solids and allows flow with less friction. On the

other hand, surface tension and heat of vaporization is relatively very low for SCFs

(De Castro, 1994).

8

1.4 Advantages of SFE technology

The applications of SFE technology have developed as a faster and less

solvent-intensive alternative to traditional extraction schemes as a result of the

critical fluids having more promising properties over conventional solvent.

Supercritical fluid extraction (SFE) methods involves a few steps, thereby leading to

short analysis time and reduced sample transfer, and hence smaller analytical errors.

In addition, by using SFE technology, the recovery of analytes is precisely and

reliability compared to conventional method i.e. Soxhlet extraction as isolation of the

analytes is completes. This is due to the solvent power, polarity and temperature of

SCF that play role as primary factor to a success extraction process. The crude oils

obtained from SFE method are easily be refined compared to conventional method

since the SFE extracts contain fewer impurities (De Castro, 1994). Throughout the

SFE process technology, the raw materials and extracts are not subjected to elevated

temperatures, thereby minimising the risk of product thermal degradation. In

addition, by supercritical fluid extraction technology the operating condition can be

operated under a wide range to extract selectively the any active compound or to

produce with improved functional or nutritional characteristics.

SFE technology is cleaner and less hazardous than conventional extraction

since 90% of the technology applications developed so far use CO2 as a solvent,

which is non-toxic and inflammable properties. Unlike liquid solvents (n-hexane,

ether, methylene chloride), supercritical CO2 poses no fire risk and leaves no

environmentally hazardous wastes. The properties of gas-like diffusivity and

viscosity, zero surface tension, and liquid-like density combined with the pressure-

dependent solvent power of a supercritical fluid have provided the stimulation for

applying supercritical fluid (SCF) technology to a range of separations problems

experienced in many segments of industry (Taylor, 1996).

9

1.5 Problem Background

Currently, SFE applications have been very limited, and are focused on the

use of CO2 as a supercritical solvent as alternative to conventional separation, i.e.

Soxhlet extraction. In fact, supercritical CO2 has been accepted as a common and

standard supercritical solvent and is the most popular and typically employed as a

solvent for most supercritical extraction applications. Even though SFE technology

has been established and known during the past 30 years, however,

commercialization of the technology is still limited (Rizvi et al., 1986). There are

only a few industrial SFE applications that have been reported such as for

decaffeination of coffee and tea and extraction of hops for brewing (Rizvi et al.,

1986 and Ooi et al., 1996).

This limitation may be attributed to the high capital investment associated

with plant start-up and intense operation due the higher pressure of up to 500 bar

required by using carbon dioxide as a solvent to allow satisfactory extraction or

fractionation process (Rizvi et al., 1986). The high-pressure operation can

contribute to the high capital cost and operating cost to maintain the high pressure.

This is one of the factors that have contributed to the limited the commercialisation

of SFE process using CO2.

Some attempts have been made to use carbon dioxide at low pressure ranging

from 40-100 bar. However, it was found that the solubility of the compound of

interest in CO2 is rather low (Maxwell, 1996, Catchpole and Von Kamp, 1997 and

Catchpole et al., 1998). Previously, Stahl et al. (1980) had studied the extraction of

seed oils by liquid CO2, found that the inferior mass transport properties and solute

fluxes caused the approach for oilseed processing inadequate. In addition, King and

Bott (1993) has noted that there is no economic incentive in the near-critical CO2

process.

The discovery of a new or alternative low-pressure solvent having the same

advantages as that of CO2 is therefore necessary in order to capitalise on the

superiority of SFE technology over traditional technique. Subcritical R134a is

10

suggested as a low-pressure alternative (Catchpole and Proells, 2001 and Wood et

al., 2002) to supercritical CO2 since it has been found to have comparable solvent

properties to CO2 (Lagalante et al., 1998) in addition to being able to extract analytes

at low temperature and pressure (Hansen et al., 2000 and Simões and Catchpole,

2001).

In addition, numerous SFE applications have focused on the extraction of

vegetables and seeds such as soybean (Lee et al., 1991), canola (Fattori et al., 1988

and Temelli, 1992), Buriti (Franca et al., 1999), sunflower (Krimiti et al., 2001 and

Salgın et al., 2005), and palm kernel (Hassan et al., 2000) using SC-CO2 to recover

valuable minor components such as tocopherols and β-carotene. The extraction of

palm oil using SFE technology is envisioned to have a great outlook (Bharat, 2003).

However, extraction of palm oil from its fruits using SC-CO2 has been found to be

relatively rare as compared to the application of SFE on other vegetable oils

(Bisunadan, 1993 and Lau et al., 2006). Until today, there has been no reported

study on the use of R134a as an alternative to CO2 solvent for the supercritical

extraction and recovery of palm oil and its valuable minor components.

1. 6 Problem Statement

Until today, the commercialization of SFE technology has been rather

limited. High operation cost associated with high operating pressure needed by CO2

as a solvent is one of the key factors that limit the commercialisation of SFE

technology (Rizvi et al., 1986, Catchpole and Proells, 2001, and Simões and

Catchpole, 2002). It is envisioned that the discovery of an alternative solvent that

allows operations at significantly lower pressure relative to those required using CO2

solvent can overcome the practical limitations towards commercialisation. For the

solvent to be viable, it should enable the process to achieve comparable or better

performance in terms of maximising oil yields while maintaining the quality and

stability of the oil through elimination of undesirable compounds. In achieving

11

economical and cleaner process, it is envisioned that R134a has a promising

potential to replace CO2 for the extraction of crude palm oil based on SFE

technology.

1.7 Research Objectives

The aims of this research are:

a) To investigate the capability of R134a as an alternative to CO2 solvent by

determining yields and solubility of palm oil in sub-critical R134a solvent at

various pressure and temperature using SFE technology.

b) To investigate the potential of R134a to recover the valuable minor

components by measuring the concentration of extracted β-carotene.

1.8 Scope of Work

In order to explore the viability of using R134a as a new solvent, it is

essential to establish fundamental data such as solubility. Palm oil extraction from

its oil palm fleshy mesocarp was performed to investigate the capability of sub-

critical R134a as alternative low-pressure solvent to CO2 by determining the yields

and solubility of palm oil in sub-critical R134a. The potential of R134a solvent to

recover the valuable minor component was also investigated by measuring the

concentration of β-carotene extracted. The tasks to be accomplished to achieve the

objectives of this study include:

• Experiments to determine palm oil solubility in sub-critical R134a at selected

range of conditions.

12

• Investigation of the effects of process parameter (temperature, pressure,

flowrate) and effects of sample pre-treatment on the yields and solubility of

palm oil and analysis of composition of fatty acids and concentration of β-

carotene using Gas Chromatography (GC) and UV-Vis Spectrophotometer

respectively.

• Correlation of the solubility behavior with a density-based model and T-P

model.

• Prediction of Response Surface Model for extraction yield including effects

of pressure and temperature.

1.9 Research Contributions

Three key contributions that have emerged from this work are:

• Equilibrium solubility data for palm oil in sub-critical R134a. To-date, there has

been no reported findings on the solubility of palm oil in R134a. Therefore, the

solubility data presented in this thesis is a pioneering work in the development of

solubility database in SFE field.

• An empirical model on the solubility behaviour of sub-critical R134a provides a

significant impetus for future SFE measurement and predictions studies.

• A detailed experimental procedure on the use of sub-critical R134a as an

alternative solvent to supercritical CO2. The experiments conducted in this work

will be a breakthrough step to chart the path towards the development of an

economical alternative new process for the crude palm oil production and for the

recovery of valuable minor components (such as carotenes and tocopherols) in

palm oil based on the principle of SFE principles.

13

1.10 Thesis Outline

This thesis is organised in 6 chapters. Chapter 1 begins with the introduction

of the research project i.e. preface on SFE technology related to vegetables oils and

fats application. The chapter also include the problem background which had

motivated this research, the research objectives and scope of work and the key

contributions of this work.

Chapter 2 describes the fundamental theory as well as the physical and

chemical properties of palm oil and its minor-components. This chapter also

presents an overview of the thermodynamic properties of R134a as well as the most

common SFE solvents. These properties are useful for solvent selection. The

fundamentals of SFE process and sub-critical conditions are also presented in the

chapter. This includes specifications on the parameters influence an extraction

process and solubility.

Chapter 3 provides a critical review of the previous works on solubility, SFE

applications to vegetables and seeds oils by means of CO2 with R134a as a solvent.

Theory and literature on Response Surface Design for statistical model and

mathematical modeling on the solubility behaviour are also included in this chapter

Chapter 4 presents the experimental work procedure for the extraction

process. The procedure begins with selection of operating conditions, sample pre-

treatment and extraction methodology. It also describes the procedure for analysis of

extracted oil sample for compounds such as fatty acids and carotene using Gas

Chromatography (GC) and UV-Vis Spectrophotometer, respectively.

The results discussed in Chapter 5 are divided into two parts. The

experimental study results are discussed in the first part. These include discussions

on the effects of various process parameters on the oil extraction yield as well as

solubility; and discussions on the effects of process parameters on the compositions

of fatty acids and carotene. In the second part, empirical modeling that describe the

14

oil yields and solubility characteristics as well as the mathematical models on

solubility behaviour based on solvent density are discussed and proposed.

Finally, Chapter 6 presents a summary of the study and the recommendations

for future work. Some suggestions are made to guide and improve future

experimental work in terms of the use of sub-critical R134a as a solvent.