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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