UNIVERSITI PUTRA MALAYSIA

MICROWAVE EXTRACTION OF ESSENTIAL OILS FROM JASMINUM SAMBAC FLOWERS

NURSHAHIDAH BINTI OSMAN Thesis

FS 2006 60

MICROWAVE EXTRACTION OF ESSENTIAL OILS FROM JASMINUM SAMBAC FLOWERS

By

NURSHAHIDAH BINTI OSMAN

Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in Fulfilment of the Requirements for the Degree of Master of Science

November 2006

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Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment of the requirement for the degree of Master of Science.

MICROWAVE EXTRACTION OF ESSENTIAL OILS FROM JASMINUM SAMBAC FLOWERS

By

NURSHAHIDAH BINTI OSMAN

November 2006

Chairman: Professor Kaida bin Khalid, PhD

Faculty: Science

The Microwave Extraction System (MES) is a high-speed method used to extract target

compounds from various raw materials. It was originally developed for the extraction of

flavors and fragrances from plant materials, which is generally carried out by

conventional techniques that require a lot of energy or a long time or a combination of

both. In this study, a microwave extraction system (MES) is developed for the extraction

of essential oils from Jasminum sambac flowers. The important MES process

parameters, i.e, time, temperature and microwave power are controlled to obtain rapidly

the highest quantity and quality of oil. The performance of MES is compared with the

Conventional Extraction Method (CEM) using various methods such as dry distillation

(DD), wet distillation (WD), hydro distillation (HD) and steam distillation (SD) in terms

of rapidity, quality and percentage of yield, chemical composition of oil and its

efficiency. The MES is performed by DD and WD at irradiation power of about 450 W

and temperature about 100 oC for 1 hour whereas CEM is performed by HD and SD at

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extraction power of 450 W and temperature 100 oC for 8 hours. The absorption power of

microwave irradiation by Jasminum sambac flowers are predicted for DD and WD. The

project has successfully proved that MES is more efficient than CEM in terms of

rapidity, quality and quantity of yield, energy use, easiness in operation and cost

effectiveness. The MES provides a rapid extraction, with about 8 times faster than CEM.

After 1 hour of microwave extraction, it is possible to collect sufficient essential oil

which provides comparable yields to those obtained with 8 hours by CEM. Using MES,

DD requires only 5 minutes to obtain its first oil droplet and WD requires 8 minutes

whereas using CEM, both HD and SD allows 15 and 42 minutes respectively to obtain

the first oil droplet. DD requires less time to obtain its first oil droplet compared to other

methods because the absorption power for dry sample is higher than for wet sample. The

DD technically gives higher percentage yield with 0.10 % which is about 5 times higher

compared to SD and HD where both only contribute 0.02 %, respectively whereas WD

contributes 0.06 %. Although more compounds are detected in the essential oil extracted

by CEM, substantial higher amounts of highly odoriferous compounds are present in the

MES extract. The relative amount of oxygenated fraction in essential oil is less than 30

% for CEM and more than 30 % for MES. In terms of the energy consumed, the energy

consumption in MES is 8 times lower than in CEM. HD requires heating of 0.4 liter of

water and 200 g of flowers to the extraction temperature, and evaporating the water and

essential oil for 8 hours whereas DD only requires heating 200 g of fresh flowers and

evaporating the in situ water and essential oil of the plant material for 1 hour.

Furthermore, MES requires maximum power irradiation only to heat up the sample and

water to its boiling point and thus obtain its first oil droplet whereas CEM requires

maximum power irradiation throughout the process. Essentially, the MES provides an

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easily controlled system, rapid extraction process; high yield and purity extracts, more

valuable essential oils, extracts with chemical compositions comparable to conventional

method and allows a substantial saving of energy. These advantages not only reduce

operating costs, but also result in a more environmentally friendly process.

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Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk ijazah Master Sains

PENGEKSTRAKAN GELOMBANG MIKRO BAGI MINYAK PATI DARIPADA

BUNGA JASMINUM SAMBAC

Oleh

NURSHAHIDAH BINTI OSMAN

November 2006

Pengerusi: Profesor Kaida bin Khalid, PhD

Fakulti: Sains

Sistem Pengekstrakan Gelombang Mikro ataupun dikenali dengan Microwave

Extraction System (MES) merupakan suatu kaedah berkelajuan tinggi yang digunakan

untuk mengekstrak komposisi-komposisi sasaran daripada pelbagai bahan mentah.

Sistem ini pada asalnya dimajukan untuk pengekstrakan bahan-bahan perisa dan

pewangi daripada tumbuh-tumbuhan yang kebiasaannya dijalankan oleh kaedah-kaedah

konvensional yang memerlukan penggunaan tenaga yang banyak atau masa

pengekstrakan yang terlampau lama atau kedua-duanya sekali. Dalam kajian ini, sebuah

sistem pengekstrakan gelombang mikro (MES) dibina untuk pengekstrakan minyak

pati dari sampel bunga Jasminum sambac. Parameter-paramater proses MES yang

penting seperti masa, suhu dan kuasa gelombang mikro dikawal untuk mencapai ekstrak

minyak pati yang paling maksimum dan berkualiti tinggi dalam masa yang singkat.

Prestasi MES dibandingkan dengan Teknik Pengekstrakan Biasa ataupun dikenali

sebagai Conventional Extraction Method (CEM) menggunakan pelbagai kaedah seperti

penyulingan kering (DD), penyulingan basah (WD), penyulingan hidro (HD) dan

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penyulingan wap (SD) dari segi kepantasan, kualiti dan peratusan minyak, komposisi

kimia minyak dan kecekapannya. MES dilakukan secara DD dan WD yang dijalankan

pada kuasa sinaran 450 W dan suhu di sekitar 100 oC selama 1 jam manakala CEM

dilakukan secara HD dan SD yang dijalankan pada kuasa pengekstrakan 450 W dan

suhu 100 oC selama 8 jam. Kuasa serapan sinaran gelombang mikro oleh bunga

Jasminum sambac diramal bagi DD dan WD. Projek ini telah membuktikan dengan

jayanya bahawa MES lebih efisien berbanding CEM dari segi kepantasan, kualiti dan

kuantiti minyak yang terhasil, penggunaan tenaga, kemudahan pengoperasian dan

penjimatan kos. MES memberikan pengekstrakan yang cepat, lebih kurang 8 kali lebih

pantas dari CEM. Selepas 1 jam pengekstrakan menggunakan gelombang mikro, adalah

mungkin untuk mengumpul amaun minyak pati yang mencukupi bagi tujuan

penyelidikan dan memberikan hasil ekstrak yang setara dengan 8 jam pengekstrakan

menggunakan CEM. Didapati titisan minyak pertama yang jatuh dikesan antara minit

kelima bagi DD dan minit kelapan bagi WD sementara HD dan SD masing-masing

memerlukan 15 dan 42 minit untuk mencapai titisan minyak pati pertama. DD

mengambil masa yang lebih singkat untuk mendapatkan titisan minyak pertama

berbanding kaedah-kaedah lain kerana kuasa serapan bagi sampel kering lebih tinggi

daripada kuasa serapan bagi sampel basah. Secara teknikal, DD menyumbangkan

peratusan ekstrak minyak yang lebih tinggi iaitu sebanyak 0.1 % iaitu 5 kali ganda

berbanding kaedah-kaedah CEM yang lain iaitu HD dan SD yang hanya

menyumbangkan minyak sebanyak 0.02 % masing-masing manakala WD memberikan

hasil sebanyak 0.06 %. Walaupun jumlah sebatian dikesan lebih banyak dalam ekstrak

CEM, namun didapati lebih banyak sebatian pewangi yang wujud dalam ekstrak MES.

Secara relatifnya, peratusan sebatian wangi di dalam minyak CEM adalah kurang dari 30

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% sementara peratusan sebatian wangi di dalam minyak CEM adalah lebih dari 30 %.

Dari segi penggunaan tenaga, MES menggunakan tenaga sebanyak 8 kali lebih rendah

berbanding CEM. HD memerlukan pemanasan 0.4 liter air dan 200 g sampel bunga

untuk mencapai suhu pengekstrakan 100 oC dan mengewap minyak pati di dalam sampel

serta tambahan air yang dibuat selama 8 jam manakala DD hanya memerlukan

pemanasan 200 g sampel bunga dan mengewap kandungan minyak pati dan air di dalam

sampel selama 1 jam. Tambahan pula, MES memerlukan penggunaan sinaran kuasa

maksimum hanya untuk memanaskan sampel dan air ke takat didihnya dan seterusnya

mencapai titisan minyak pertama manakala CEM memerlukan sinaran kuasa maksimum

sepanjang proses berjalan. Paling utama, MES merupakan suatu sistem kawalan yang

amat mudah, proses pengekstrakan yang pantas, menghasilkan minyak yang lebih

banyak, tulen serta berkualiti tinggi, memberikan komposisi minyak pati yang setara

dengan CEM serta membenarkan penjimatan tenaga yang banyak. Kelebihan-kelebihan

ini bukan sahaja menjimatkan kos malah menyumbangkan kepada suatu proses yang

mesra alam.

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ACKNOWLEDGEMENTS

Many people contributed to the creation of this book but first and foremost, I thank

Allah S.W.T for the health, ability and resources that have sustained me in this life.

I would like to express my deep appreciation to my supervisor who is also the chair of

the supervisory committee, Professor Dr. Haji Kaida bin Khalid for his invaluable

thoughts, attentive suggestions and unlimited support throughout my master program.

His breadth of knowledge guided my research on several occasions. Also, I would like

to express a great appreciation and special thanks to my co-supervisors, Associate

Professor Dr. Haji Aspollah Haji Md. Sukari and Dr. Jumiah Hassan for their support,

guidance and knowledge throughout the study.

Among others I would particularly like to thank are Encik Roslim, Encik Zul, Encik

Zainal, Encik Ishar, Encik Radzi and my colleagues for their various encouragement or

practical help in other ways. I also owe gratitude in particular to my labmate, Encik

Rudy bin Nurdin for his invaluable help and co-operation in sharing ideas and

information concerning my dissertation and others who had helped me throughout this

project. Last but not least, I would like to thank my family especially my parents, Osman

bin Bakar and Badariah binti Ahmad for their love and support to me, their sacrifices

and understanding from the very beginning of my work until my master studies were

completed. May Allah reward them all the best of rewards in the Hereafter.

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I certify that an Examination Committee has met on 17th November 2006 to conduct the final examination of Nurshahidah binti Osman on her Master of Science thesis entitled “Microwave Extraction of Essential Oils from Jasminum sambac Flowers” in accordance with Universiti Pertanian Malaysia (Higher Degree) Act 1980 and Universiti Pertanian Malaysia (Higher Degree) Regulations 1981. The Committee recommends that the candidate be awarded the relevant degree. Members of the examination Committee are as follows: Wan Mohamad Daud Wan Yusoff PhD Associate Professor Faculty of Science Universiti Putra Malaysia (Chairman) Azmi Zakaria, PhD Associate Professor Faculty of Science Universiti Putra Malaysia (Internal Examiner) Zulkifly Abas, PhD Associate Professor Faculty of Science Universiti Putra Malaysia (Internal Examiner) Ibrahim Abu Talib, PhD Professor Faculty of Science and Technology Universiti Kebangsaan Malaysia (External Examiner) _______________________________ HASANAH MOHD GHAZALI, PhD Professor/Deputy Dean School of Graduate Studies Universiti Putra Malaysia Date: 15 FEBRUARY 2007

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This thesis submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfilment of the requirement for the degree of Master of Science. The members of the Supervisory Committee are as follows:

Kaida bin Khalid, PhD Professor Faculty of Science Universiti Putra Malaysia (Chairman)

Haji Aspollah Haji Md. Sukari, PhD Associate Professor Faculty of Science Universiti Putra Malaysia (Member)

Jumiah Hassan, PhD Lecturer Faculty of Science Universiti Putra Malaysia (Member) __________________

AINI IDERIS, PhD Professor / Dean

School of Graduate Studies Universiti Putra Malaysia

Date: 8 MARCH 2007

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DECLARATION

I hereby declare that the thesis is based on my original work except for quotations and citations which have been duly acknowledged. I also declare that it has not been previously or concurrently submitted for any other degree at UPM or other institutions. _______________________________ NURSHAHIDAH BINTI OSMAN Date:

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TABLE OF CONTENTS Page ABTSRACT ii ABSTRAK v ACKNOWLEDGEMENTS viii APPROVAL ix DECLARATION xi LIST OF TABLES xiv LIST OF FIGURES xv LIST OF SYMBOLS AND ABBREVIATIONS xviii CHAPTER 1 INTRODUCTION AND LITERATURE REVIEW 1 1.1 Introduction 1 1.2 Sample – Jasminum Sambac 4 1.3 Jasmine Oil 6 1.4 Conventional Methods of Extraction 7 1.5 Newly Introduced Technique: Microwave Extraction System (MES) 11 1.6 Scope of Thesis 14 2 THEORY 15 2.1 Introduction 15 2.2 Microwave Oven 17 2.3 Drying process in the microwave oven 19 2.3.1 Initial heating up period 20 2.3.2 Constant drying rate period 20 2.3.3 Falling drying rate period 21 2.4 Microwave Heating Mechanisms 21 2.4.1 Dipole Interaction 23 2.4.2 Polarization 26 2.4.3 Ionic conduction 28 2.4.4 Complex Permittivity 29 2.4.5 Dielectric Properties of Water 31 2.4.6 Dielectric Properties of Sample 33 2.4.7 Absorption power of Sample 37 2.5 Moisture Content and Its Measurement 39

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3 MATERIALS AND METHODOLOGY 41 3.1 Introduction 41 3.2 Density and Specific Gravity Measurements 42 3.3 Moisture Content Measurements 44 3.4 Dielectric Measurements 46 3.5 Essential Oil Extraction 50 3.5.1 Microwave Extraction System (MES 50 3.5.2 Conventional Extraction Method (CEM) 53 3.6 Water Heating Measurements 46 3.7 Chemical Analysis 61 4 RESULTS AND DISCUSSION 63 4.1 Introduction 63 4.2 Results of Density and Specific Gravity 64 4.3 Results of Moisture Content 67 4.4 Results of Dielectric Properties and Power Absorption 67 4.5 Results of Extraction and Chemical Analysis 93 5 CONCLUSION 110 5.1 Conclusion 110 5.2 Further Research 113 REFERENCES 115 APPENDICES 121 BIODATA OF THE AUTHOR 135

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LIST OF TABLES

Table Page

4.1 Evaporated moisture of Jasminum sambac flowers at various temperatures. 65 4.2 Results of dielectric properties of Jasmine (experimental), dielectric properties

of mixture for fresh jasmine (Mixture model Equation 2.2) and dielectric properties of water for various temperatures at frequency (2.42±0.01) GHz. 72

4.3 Dielectric properties of mixture for dry and wet Jasmine for various

temperatures at frequency (2.42 ± 0.01) GHz. 73 4.4 Electric field strength and absorption power of 0.2 liter of water at 90oC and frequency of (2.42 ± 0.01) GHz. 74

4.5 Electric field and absorption power of dry and wet Jasmine for various

temperatures at frequency (2.42 ± 0.01) GHz. 74

4.6 Results of time of first oil droplet, percentage of yield, oxygenated fraction and major compound for Jasminum sambac essential oil extraction using

MES and CEM. 98 4.7 Results of the extraction and composition of Jasminum sambac oils obtained

by MES and CEM. 106

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LIST OF FIGURES

Figure Page

1.1 Jasminum Sambac (L.) Aiton 5 2.1 Electromagnetic Frequency Spectrum 16 2.2 Drying Characteristic of a Liquid 19 2.3 Dipole Interaction 24 2.4 Interaction of electromagnetic wave with water or moist substances 25 2.5 Various types of Polarisation (Von Hippel, 1954) 27 2.6 Ionic conduction 29 3.1 ‘Open-ended coaxial line’ sensor coupled with a computer-controlled Automated Network Analyzer (ANA) 48

3.2 An open-ended Coaxial Line. A Reflection Method where the Sensor is Immersed Inside the Sample During Measurement. The Fields at the Probe End “Fringe” into the Material, Causing a Reflection that can be Related to the Complex Permittivity (Blackham et al, 1990) 49

3.3 Microwave Extraction Method (MES) 52 3.4 Experimental Setup of Microwave Extraction System (MES) 52 3.5 Experimental Setup of Hydro Distillation Method (CEM) 54 3.6 Experimental Setup of Steam Distillation Method (CEM) 54

3.7 Experimental Flowchart 55

3.8 Flowchart of Microwave Absorption Power Measurement 60

4.1 Evaporated moisture of Jasminum sambac flowers at various temperatures. 66 4.2 Dielectric constant of water, ε’w as a function of frequency (experimental). 75

4.3 Dielectric constant of Jasmine, ε’J as a function of frequency (experimental). 76

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4.4 Dielectric constant of mixture for fresh Jasmine, ε’mixJF as a function of frequency (mixture model). 77

4.5 Dielectric loss factor of water, ε”w as a function of frequency (experimental). 78 4.6 Dielectric loss factor of Jasmine, ε”J as a function of frequency (experimental).79

4.7 Dielectric loss factor of mixture for fresh Jasmine, ε”mixJF as a function of frequency (mixture model). 80

4.8 Dielectric properties of Jasmine flowers and water as a function of temperature

at frequency 2.42 GHz (experimental & mixture model). 81

4.9 Dielectric constant of mixture for dry Jasmine, ε 'mixJD as a function of frequency. 82

4.10 Dielectric loss factor of mixture for dry Jasmine, ε "mixJD as a function of

frequency. 83

4.11 Dielectric constant of mixture for wet Jasmine, ε 'mixJW as a function of frequency. 84

4.12 Dielectric loss factor of mixture for wet Jasmine,ε "mixJW as a function of frequency. 85

4.13 Dielectric properties of mixture for dry and wet Jasmine as a function of temperature at frequency 2.42 GHz. 86

4.14 Electric field inside dry Jasmine, EinJD as a function of frequency. 87

4.15 Electric field inside wet Jasmine, EinJW as a function of frequency. 88

4.16 Electric field inside dry Jasmine, EinJD and wet Jasmine, EinJW as a function

of temperature at frequency 2.42 GHz. 89

4.17 Absorption power by dry Jasmine, PAJD as a function of frequency. 90

4.18 Absorption power by wet Jasmine, PAJW as a function of frequency. 91

4.19 Absorption power by dry Jasmine, PAJD and wet Jasmine, PAJW as a function of temperature at frequency 2.42 GHz. 92

4.20 Temperature and Power Profile for fresh Jasmine extracted by Dry Distillation (MES). 99 4.21 Temperature and Power Profile for soaked Jasmine extracted by Wet Distillation (MES). 100

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4.22 Temperature and Power Profile for soaked Jasmine extracted by Hydro Distillation (CEM). 101

4.23 Temperature and Power Profile for fresh Jasmine extracted by Steam Distillation (CEM). 102

4.24 Temperature and Power Profile for Fresh and Soaked Jasmine extracted by MES and CEM. 103

4.25 Temperature Profile for Fresh and Soaked Jasmine extracted by MES and CEM. 104

4.26 Power Profile for Fresh and Soaked Jasmine extracted by MES and CEM. 105

4.27 Proportion of the oxygenated fraction in Jasminum sambac essential oil (%). 109

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LIST OF SYMBOLS AND ABBREVIATIONS

£ pound eV electron volts T temperature TW temperature of water TR room temperature Tf final temperature

Ti initial temperature ∆ Tw temperature rise of water t time ∆tw heating time of water τ relaxation time ω angular frequency c speed of light co velocity of propagating wave in free space (co = 3.0 x 108 m/s) π pi (π = 3.142) f frequency λ wavelength λ0 free space wavelength E electric field strength (unit: V/m) H magnetic field strength or magnetic intensity (unit: A/m) ∇ x H curl of H ∇ del operator

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j √-1 J current density σ conductivity ε permittivity ε’ dielectric constant ε” loss factor tan δ loss tangent or the ratio of ε” to ε” εo permittivity of free space (εo = 8.85 x 10-12 F/m) ε’w dielectric constant of water ε”w loss factor of water ε’mixs relative dielectric permittivity of mixture for solid materials ε’s dielectric constant of solid materials ε”s loss factor of sample ε* complex permittivity or dielectric properties of material ε*r relative permittivity ε’r relative dielectric constant ε”r relative loss factor ε”d dipolar polarizations ε”e electronic polarizations ε”a atomic polarizations ε”i interfacial (Maxwell-Wagner) polarizations ε”c conductive losses ε’s static permittivity ε’∞ permittivity for infinite frequency

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ε'J dielectric constant of Jasmine (experimental) ε"J loss factor of Jasmine (experimental) ε*w dielectric permittivity of water added to jasmine ε*a dielectric permittivity of air in jasmine ε*mixJF dielectric properties of mixture for fresh jasmine ε*mixJD dielectric properties of mixture for dry jasmine ε*mfixJW dielectric properties of mixture for wet jasmine ε'mixJF dielectric constant of mixture for fresh jasmine (mixture model) ε"mixJF loss factor of mixture for fresh jasmine (mixture model) ε'mixJD dielectric constant of mixture for dry jasmine (mixture model) ε"mixJD loss factor of mixture for dry jasmine (mixture model) ε'mixJW dielectric constant of mixture for wet jasmine (mixture model) ε"mixJW loss factor of mixture for wet jasmine (mixture model) PA absorption power or the energy developed per unit volume (W/m3) PAw absorption power per unit volume by water (W/m3) PAs absorption power per unit volume by sample (W/m3) PAJD absorption power per unit volume by dry Jasmine (W/m3) PAJW absorption power per unit volume by wet Jasmine (W/m3) Eins electric field strength inside sample (V/m) Eos electric field strength outside sample (V/m) EinJD electric field strength inside dry jasmine (V/m) EinJW electric field strength inside wet jasmine (V/m) Einw electric field strength inside water (V/m)

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Eow electric field strength outside water (V/m) dp penetration depth or power penetration Zo wave impedance of free space (approximately 377 Ω) P polarization h specific heat of the material

hw specific heat of water

L Latent heat of water

MCJ moisture content of fresh jasmine flowers MCd moisture content defined on a dry basis MCw moisture content defined on a wet basis SG specific gravity Ρobj density of object ρJF density of fresh jasmine

ρJD density of dried jasmine

ρw density of water (ρw = 1.000 g/cm3) mw mass of water mw(added) Mass of water to submerge fresh jasmine

ms mass of sample mm mass of moist material md mass of dry material ma Mass of air mJFa Mass of fresh jasmine to determine volume fraction of air mJF Mass of fresh jasmine to extract

Mw wet weight of the sample

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Vs volume fraction of sample VJ volume fraction of water in fresh jasmine (VJ =(MCJ/(MCJ+((1-MCJ)(ρw /ρJD))))) Volw Volume of water to submerge fresh jasmine (Volw = mw(added) /ρw) Vw Volume fraction of Water (Vw = Volw / Volw + VolJF) Vola Volume of air (Vola = ma / ρw) Va Volume fraction of air (Va = Vola / Vola + VolJFa) VolJFa Volume of fresh jasmine to determine volume fraction of air (VolJFa = mJFa /ρJF) VolJF Volume of fresh jasmine to extract (VolJF = mJF / ρJF) SFME Solvent Free Microwave Extraction MAE Microwave-Assisted Extraction MES Microwave Extraction System CEM Conventional Extraction Method DD Dry Distillation WD Wet Distillation HD Hydro Distillation SD Steam Distillation GC Gas Chromatography MS Mass Spectrometer GC-MS Gas Chromatography coupled to Mass Spectrometry CAS Chemical Abstract Number m/z mass to charge ratio OC oxygenated compound TC terpene compound

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ppm parts per million H2O chemical description for water CO2 carbon dioxide NaCl natrium chloride EM Electromagnetic VHF Very High Frequency ANA Automated Network Analyser

CHAPTER 1

INTRODUCTION & LITERATURE REVIEW

1.1 Introduction

The initial surge in microwave technology development was driven by the military needs

of the Second World War. The tremendous effort that went into development of radar

during Second World War generated a great body of knowledge on the properties of

microwaves and related technologies [1]. After the Second World War, a rapid growth of

microwaves system has taken place in the area of telecommunication and navigation in

both civilian and military. However, industrial, scientific, medical and domestic

applications have developed at a slower pace. Most microwave applications fall in the

range 300 MHz to 300 GHz [2].

By far, the most popular application of microwave power is in microwave oven for

domestic and commercial cooking, heating and drying. Household and institutional

microwave ovens operate at the frequency of 2450 MHz and the lower microwave

frequency 915 MHz is currently only used for industrial applications. On the other hand,

a greater variety of industrial applications of high microwave power has been

demonstrated including applications in various industries such as rubber, food, textiles,

plastics, foundry, building materials, paper, pharmaceuticals, cosmetics, and coal. The

main advantages of microwave power in processing of materials are increased rate of