iii
IMPACT OF PANDAN LEAF EXTRACT ADDITION ON THE QUALITY AND
STABILITY OF SUNFLOWER OIL DURING MICROWAVE HEATING
RAFIQQAH BINTI MOHAMAD SABRI
A report submitted in partial fulfillment of the requirements for the award of the
degree of Bachelor of Engineering (Chemical-Bioprocess)
Faculty of Chemical Engineering
Universiti Teknologi Malaysia
MAY 2013
v
ABSTRACT
The present study was conducted to investigate the effect of addition of
pandan leaf extract on the quality and stability of sunflower oil during microwave
heating. Extracts of pandan was prepared in different polarity solvents (80%
methanol in water, methanol and ethanol). Preliminary antioxidant activity
assessment among the extracts was conducted with 1,1’-diphenyl-2-picrylhydrazyl
(DPPH) radical scavenging activity and by measuring per cent inhibition of linoleic
acid peroxidation and total phenolic content. Since 80% methanolic extract showed
highest antioxidant activity among the extracts, it was then further evaluated using
sunflower oil during microwave heating. The vegetable oil was stabilized with
extract at a dosage of 0.1, 0.2 and 0.4% and subjected to microwave heating (0-24
min) and analysed periodically. Butylated hydroxyanisole (BHA) at 0.02% served as
standard beside the negative control. The amount of free fatty acids was found to be
higher in fresh samples. Peroxide values during microwave heating of all the samples
were increased until a maximum is reached and then decreased until the end of
heating. Apart from that, quality parameters such as p-anisidine value, viscosity,
specific extinction and polar compound values increased significantly in most of the
samples as heating time progressed. Meanwhile, there is progressive decrease in
iodine value during heating. In Gas Liquid Chromatography analysis, C18:2/C16:0
ratios were found to be decreased as heating time increased. Most of the degradation
indicators suggested that the degradation was rapid in fresh oil samples compared to
stabilized oils. In a nutshell, by adding this extracts, alteration of these parameters
were reduced and results from different parameters were in agreement with each
other, suggesting the highest efficiency of SFB, followed by SFP4, SFP2, SFP1, and
SFO. Results revealed pandan leaf to be a good natural alternative to existing
synthetic antioxidants in the food industry.
vi
ABSTRAK
Kajian ini telah dijalankan untuk mengkaji kesan penambahan ekstrak daun
pandan terhadap kualiti dan kestabilan minyak bunga matahari semasa pemanasan
gelombang mikro. Ekstrak pandan telah disediakan dalam pelarut kutub yang
berbeza (80% methanol dalam air, metanol dan etanol). Penilaian awal aktiviti
antioksidan dalam kalangan ekstrak telah dijalankan dengan 1,1 '-Diphenyl-2-
picrylhydrazyl (DPPH) aktiviti radikal memerangkap dan dengan mengukur peratus
perencatan pengoksidaan linoleik asid dan jumlah kandungan fenolik.
Memandangkan 80% ekstrak metanol menunjukkan aktiviti antioksidan yang
tertinggi dalam kalangan ekstrak, ia kemudian terus dinilai menggunakan minyak
bunga matahari semasa pemanasan gelombang mikro. Minyak sayur-sayuran telah
distabilkan dengan ekstrak pada dos sebanyak 0.1, 0.2 dan 0.4% dan tertakluk
kepada mikro pemanasan (0-24 min) dan dianalisis secara berkala. Hydroxyanisole
Butylated (BHA) pada 0.02% berkhidmat sebagai standard kawalan di sebelah
negatif. Jumlah asid lemak bebas telah didapati lebih tinggi dalam sampel segar.
Nilai peroksida semasa pemanasan gelombang mikro semua sampel telah meningkat
sehingga maksimum dicapai dan kemudian menurun sehingga akhir pemanasan.
Selain daripada itu, parameter kualiti seperti nilai-p anisidine, kelikatan, kepupusan
tertentu dan nilai-nilai kompaun kutub meningkat dengan ketara dalam kebanyakan
sampel sebagai masa pemanasan maju. Sementara itu, terdapat penurunan progresif
dalam nilai iodin semasa pemanasan. Dalam analisis Gas Kromatografi cecair,
C18:2/C16:0 nisbah telah didapati menurun masa pemanasan meningkat Kebanyakan
petunjuk kemerosotan mencadangkan bahawa kemerosotan itu pesat dalam sampel
minyak segar berbanding dengan minyak stabil. Secara ringkas, dengan menambah
ekstrak ini, perubahan parameter ini telah dikurangkan dan hasil daripada parameter
yang berbeza dalam perjanjian antara satu sama lain, menunjukkan kecekapan
tertinggi SFB, diikuti oleh SFP4, SFP2, SFP1, dan SFO. Keputusan mendedahkan
vii
pandan sebagai alternatif semula jadi yang baik untuk antioksida sintetik yang sedia
ada dalam industri makanan.
viii
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION
DEDICATION
ACKNOWLEDGEMENTS
ABSTRACT
ABSTRAK
ii
iii
iv
v
vi
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
LIST OF ABBREVIATIONS
LIST OF SYMBOLS
viii
xii
xiii
xiv
xv
1 INTRODUCTION
2 PROBLEM STATEMENT, OBJECTIVE AND
SCOPE OF STUDY
2.1 Problem Statement
2.2 Objective
2.3 Scope of Study
1
3
3
4
4
ix
3 LITERATURE REVIEW
5
3.1 A brief description of Sunflower Oil 5
3.1.1 Health Benefits of Sunflower Oil 8
3.1.1.1 Sunflower Oil and Skin protection
3.1.1.2 Sunflower Oil and Cardiovascular
benefits
3.1.1.3 Sunflower Oil and Anti-
inflammatory
3.2 Antioxidant
3.2.1 Natural Antioxidant
3.2.2 Synthetic Antioxidant
8
9
bbbb10
10
3.3 Microwave Heating 13
3.3.1 Introduction
3.3.2 Mechanism of Microwave Heating
13
14
3.4 Chemical Reactions during Heating 15
3.4.1 Hydrolysis of Oils
3.4.2 Oxidation of Oils
3.4.3 Polymerization of Oils
3.4.4 Colour Formation
15
16
17
19
3.5 Previous Studies Related to this Work 20
4 METHODOLOGY 22
4.1 Plant Materials and Chemicals 22
4.2 Experimental Methods
4.2.1 Preparation of Pandan Leaf Extracts
4.2.2 Evaluation of Antioxidant Activity
22
22
23
11
12
x
4.2.2.1 DPPH Scavenging Assay
4.2.2.2 Linoleic Acid System
4.2.2.3 Total Phenolic Content
4.2.3 Microwave Heating
4.2.4 Analysis of Oil Quality
4.2.4.1 Free Fatty Acid
4.2.4.2 Peroxide Value
4.2.4.3 p-Anisidine Value
4.2.4.4 Iodine Value
4.2.4.5 Specific Extinction
4.2.4.6 Viscosity
4.2.4.7 Total Polar Compound by Mini
Column Method
4.2.4.8 Fatty Acid Composition by GLC
4.2.4.9 Statistical Analysis
23
24
24
25
26
26
27
28
30
32
33
35
37
38
5 RESULTS AND DISCUSSION 39
5.1 Introduction
5.2 Yield of extracts with antioxidative properties
5.3 Evaluation of Antioxidant Activity
5.3.1 DPPH Radical Scavenging Assay
5.3.2 Linoleic Acid Peroxidation System
5.3.3 Total Phenolic Content
39
39
40
40
41
42
5.4 Analysis of Oil Quality
5.4.1 Changes in Free Fatty Acid
5.4.2 Changes in Peroxide Value
43
44
44
xi
5.4.3 Changes in p-Anisidine Value
5.4.4 Changes in Total Oxidation (TOTOX)
5.4.5 Changes in Iodine Value
5.4.6 Changes in Specific Extinction
5.4.7 Changes in Viscosity
5.4.8 Changes in Total Polar Compound
5.4.9 Changes in Fatty Acid Composition
46
48
48
49
51
51
53
6 CONCLUSION AND RECOMMENDATIONS
54
REFERENCE 55
Appendices A-B 66-67
55
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