EXTRACTION OF PALM OIL FROM PALM MESOCARP USING...
Transcript of EXTRACTION OF PALM OIL FROM PALM MESOCARP USING...
EXTRACTION OF PALM OIL FROM PALM MESOCARP USING
SUB-CRITICAL R134a
ANA NAJWA MUSTAPA
UNIVERSITI TEKNOLOGI MALAYSIA
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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.
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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.
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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.
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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∆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
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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.
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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).
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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).
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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
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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.
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• 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.
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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.