UNIVERSITI PUTRA MALAYSIA EFFECTS OF FRYING AND STORAGE CONDITIONS ON PHYSICOCHEMICAL PROPERTIES OF PALM OLEIN AND OLIVE OIL BLENDS MAHSA NAGHSHINEH FSTM 2009 4
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UNIVERSITI PUTRA MALAYSIA
EFFECTS OF FRYING AND STORAGE CONDITIONS ON
PHYSICOCHEMICAL PROPERTIES OF PALM OLEIN AND OLIVE OIL BLENDS
MAHSA NAGHSHINEH
FSTM 2009 4
EFFECTS OF FRYING AND STORAGE CONDITIONS ON PHYSICOCHEMICAL PROPERTIES OF PALM OLEIN
AND OLIVE OIL BLENDS
By
MAHSA NAGHSHINEH
Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in Fulfilment of the Requirements for the Degree of Master of Science
May 2009
Especially dedicated to my beloved father, mother, brother and my dear husband.
ii
Abstract of thesis presented to the senate of Universiti Putra Malaysia in fulfilment of the requirements for the Degree of Master of Science
EFFECTS OF FRYING AND STORAGE CONDITIONS ON PHYSICOCHEMICAL PROPERTIES OF PALM OLEIN
AND OLIVE OIL BLENDS
By
MAHSA NAGHSHINEH
May 2009
Chairman : Associate Professor Azis Ariffin, PhD Faculty : Food Science and Technology
The main objective of this study was to investigate the effect of type and concentrations
of frying oil namely palm olein (POo) (0, 10, 25, 50, 75, 90 and 100% w/w) and olive
oil (OO) (0, 10, 25, 50, 75, 90 and 100% w/w) contents on physicochemical properties
of the oil blends. The main physicochemical properties of frying media namely iodine
value (IV), peroxide value (PV), anisidine value (AV), totox value (TV), total polar
component (TPC), free fatty acid (FFA), cloud point, color and viscosity were assessed
as response variables in the present study. The results indicated that the type and
concentration of frying media had no significant (p > 0.05) effect on FFA of oil blends;
whereas the magnitudes of IV, PV, AV, TV, cloud point, color and viscosity were
significantly (p < 0.05) influenced by the type and concentration of frying media. The
highest TV (6.10) was shown in the oil blend containing 10% (w/w) POo and 90%
(w/w) OO; while the least TV (2.41) was observed in the oil blend containing 90%
iii
(w/w) POo and 10% (w/w) OO. This observation could be explained by the high
proportion of polyunsaturated fatty acids to monounsaturated fatty acids in former oil
blend (POo:OO, 10:90) compared to latter oil blend (POo:OO, 90:10), thus indicating
that the increase in the proportion of polyunsaturated/monounsaturated fatty acids led to
decrease the chemical stability of the oil blend to the oxidative rancidity.
Subsequently, the influence of partial replacement of olive oil (25 and 50% w/w) on
frying performance was investigated during 5 consecutive days of frying process. In
general, the physiochemical properties of oil blends were significantly (p < 0.05)
influenced by the partial replacement of olive oil. The increase in the proportion of
polyunsaturated/monounsaturated fatty acid significantly (p < 0.05) decreased the
chemical stability of the oil blend during the frying process. The highest changes in AV
(79.22), PV (13.55 meq O2/kg) and TV (103.18) were shown by the control (POo, 100%
w/w); while the oil blend 2 (POo: OO, 50:50) containing higher concentration of olive
oil exhibited the least changes in AV (53.17), PV (2 meq O2/kg) and TV (52.29) during
5 days frying process. Thus, the present study offers that the chemical stability of oil to
the oxidative rancidity depends on not only the saturated fatty acid content but also on
the proportion of monounsaturated to polyunsaturated fatty acids. The frying time also
showed the significant (p < 0.05) effect on TPC of frying media. TPC increased by
prolonging the frying time depending on type of frying oil. During 5 days of frying
process, the highest increase in TPC (16.51%) was shown by control sample (i.e. POo,
100%); while the frying process using oil blend 2 containing 50% POo and 50% OO
resulted in the least increase in TPC (14.63%). Thus, the results showed that the oil
blend containing higher olive oil content (i.e. higher oleic acid) provided lower TPC
iv
(19.24%) than the TPC (20.92%) of frying media containing higher POo content.
The last part of this study was conducted to evaluate the influence of storage time and
type of frying media (POo: OO, 100:0, 75:25 and 50:50) as independent variables on the
physicochemical properties of oil blends during 60 consecutive days under accelerated
condition (60 ºC). The physiochemical properties of oil blends were significantly (p <
0.05) influenced by the independent variables studied. The increase in the proportion of
polyunsaturated/monounsaturated fatty acid significantly (p < 0.05) decreased the
chemical stability of the oil blend during storage time. The highest changes in AV (38),
PV (39.98 meq O2/kg) and TV (117.26) were shown by the control (POO, 100% w/w);
while the oil blend 2 (POo: OO, 50:50) containing higher concentration of olive oil (i.e.
higher oleic acid content) exhibited the least changes in AV (29.31), PV (26.93 meq
O2/kg) and TV (83.38) during 60 days storage. In fact, the oil blend 2 (POo: OO, 50:50)
containing higher concentration ratio of oleic acid to linoleic acid (C18:2) was found to
be stable during 60 days storage. Thus, the present study suggested that blending palm
olein with high monounsaturated fatty acid-contained oil e.g. olive oil can provide the
oil blend which is physically more stable than regular POo and remained liquid at
ambient temperature.
v
Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi sebahagian keperluan untuk Sarjana Sains
KESAN PENGGORENGAN DAN KEADAAN PENYIMPANAN KE ATAS SIFAT-SIFAT FIZIKOKIMIA ADUNAN MINYAK SAWIT OLEIN
DAN MINYAK ZAITUN
Oleh
MAHSA NAGHSHINEH
Mei 2009
Pengerusi : Professor Madya Azis Ariffin, PhD Fakulti : Sains dan Teknologi Makanan
Objektif utama kajian ini adalah untuk menyiasat kesan jenis dan kepekatan minyak
menggoreng menggunakan minyak sawit olein (POo, 0, 25, 50, 75 dan 100% w/w) dan
minyak zaitun (OO, 0, 25, 50, 75 dan 100% w/w) ke atas ciri-ciri fizikokimia adunan
kedua-dua minyak tersebut. Dalam kajian ini, ciri-ciri fizikokimia utama media
menggoreng seperti nilai iodin (IV), nilai peroksida (PV), nilai anisidina (AV), nilai
totox (TV), asid lemak bebas (FFA), takat keruh, warna, jumlah komponen polar (TPC)
dan kelikatan dikaji sebagai gerak balas pemboleh ubah. Keputusan menunjukkan jenis
dan kepekatan media menggoreng tidak mempunyai kesan yang bererti (p > 0.05) ke
atas asid lemak bebas adunan minyak goreng; tetapi jenis dan kepekatan media
menggoreng mempunyai kesan yang signifikan (p < 0.05) ke atas IV, PV, AV, TV, takat
keruh, warna dan kelikatan. Nilai TV yang paling tinggi (6.10) dapat dikesan apabila
menggunakan adunan minyak yang mengandungi 10% (w/w) POo dan 90% (w/w) OO;
vi
manakala nilai TV yang paling rendah (2.41) dikesan apabila adunan 90% (w/w) POo
dan 10% (w/w) OO digunakan. Keputusan ini dapat dihuraikan dengan kehadiran nisbah
asid lemak politaktepu terhadap asid lemak monotaktepu yang tinggi dalam adunan awal
(POo:OO, 10:90) berbanding adunan yang kedua (POo:OO, 90:10). Peningkatan dalam
nisbah asid lemak politaktepu/monotaktepu boleh meningkatkan kestabilan kimia
adunan minyak terhadap ketengikan oksidatif.
Dalam kajian seterusnya, kesan penggantian separa minyak zaitun (25% dan 50% w/w)
ke atas prestasi menggoreng dikaji melalui proses menggoreng selama 5 hari berturut-
turut. Secara amnya, penggantian separa minyak zaitun memberi kesan yang signifikan
(p < 0.05) ke atas sifat-sifat fizikokimia adunan minyak tersebut. Peningkatan nisbah
asid lemak politaktepu/monotaktepu menurunkan kestabilan kimia adunan minyak
secara signifikan (p < 0.05) semasa proses menggoreng. Seperti yang ditunjukkan dalam
keputusan, perubahan yang paling tinggi dalam nilai AV (79.22), PV (13.55 meq O2/kg)
dan TV (103.18) ditunjukkan oleh kawalan (POo 100% w/w); manakala adunan minyak
2 (POo:OO, 50:50) yang mengandungi kepekatan minyak zaitun yang lebih tinggi
menunjukkan perubahan paling minima dalam nilai AV (53.17), PV (2 meq O2/kg) dan
TV (52.29) semasa proses menggoreng selama 5 hari berturut-turut. Kajian ini
menunjukkan bahawa kestabilan kimia minyak terhadap ketengikan oksidatif
bergantung bukan sahaja kepada kandungan asid lemak tepu tetapi juga nisbah asid
lemak monotaktepu/politaktepu. Keputusan juga menunjukkan bilangan hari
menggoreng mempunyai kesan yang signifikan (P < 0.05) ke atas TPC (16.51%) media
menggoreng. Seperti yang ditunjukkan, TPC (14.63%) meningkat dengan
memanjangkan masa menggoreng. Semasa proses menggoreng selama 5 hari, sampel
vii
kawalan (POo 100%) menunjukkan peningkatan TPC yang paling tinggi; manakala
adunan minyak 2 yang mengandungi 50% POo dan 50% OO menunjukkan peningkatan
TPC yang terendah. Oleh yang demikian, keputusan menunjukkan bahawa adunan
minyak yang mengandungi kandungan minyak zaitun yang lebih tinggi (i.e. kandungan
asid oleik yang lebih tinggi) memberikan nilai TPC (19.24%) yang lebih rendah
berbanding TPC (20.92%) aduanan media menggoreng yang mengandungi POo yang
lebih tinggi.
Dalam bahagian yang terakhir kajian ini, pengaruh masa penyimpanan dan jenis adunan
media menggoreng (POo:OO, 100:0, 75:25 dan 50:50) sebagai pemboleh ubah tidak
bersandar ke atas sifat-sifat fizikokimia adunan minyak selama 60 hari dalam keadaan
terpecut (60 ºC) telah dikaji. Seperti yang ditunjukkan dalam keputusan, ciri-ciri
fizikokimia adunan minyak dipengaruhi oleh pemboleh ubah tidak bersandar secara
signifikan (p < 0.05). Keputusan juga menunjukkan peningkatan nisbah asid lemak
politaktepu/monotaktepu menurunkan kestabilan kimia adunan minyak secara signifikan
(p < 0.05) semasa proses penyimpanan. Sampel kawalan (POo, 100% w/w)
menunjukkan perubahan nilai AV (38), PV (39.98 meq O2/kg) dan TV (117.26) yang
paling besar, manakala adunan minyak 2 (POo:OO, 50:50) yang mengandungi
kepekatan minyak zaitun yang lebih tinggi (i.e. kandungan asid oleik yang lebih tinggi)
menunjukkan perubahan nilai AV (29.31), PV (26.93 meq O2/kg) dan TV (83.38) yang
paling minima semasa proses penyimpanan selama 60 hari. Adunan minyak 2 (POo:
OO, 50:50) yang mengandungi nisbah kepekatan asid oleik/asid linoleik (C18:2) yang
lebih tinggi didapati lebih stabil semasa proses penyimpanan selama 60 hari. Dengan
demikian, kajian ini menunjukkan pengadunan minyak sawit olein dengan minyak yang
viii
mengandungi asid lemak monotaktepu yang tinggi, misalnya minyak zaitun boleh
menghasilkan adunan minyak yang lebih stabil secara fizikal di suhu ambien berbanding
POo biasa.
ix
ACKNOWLEDGMENTS
I would like to my sincere gratitude to Associate Professor Dr. Azis Ariffin, the
chairman of my Supervisory Committee for his kind assistant, advice and support
during the preparation of this thesis. I would like to acknowledge Professor Dr. Hasanah
Mohd. Ghazali for her support on research equipment and her kind assistant during this
research. I am so grateful to other members of the Supervisory Committee, Dr.
Abdulkarim S. Mohammed and Dr. Ainie Kuntom of the Malaysian Palm Oil Board
(MPOB).
I would like to honestly appreciate Dr. Hamed Mirhosseini for his kind assistant,
guidance and encouragement during this research. I would also like to thank the staff in
Oil and Fat Technology Centre of the MPOB.
Last but not least, I would like to express my heartiest appreciation to my beloved
father, mother and husband for their moral support, encouragement, patience and
understanding throughout my studies.
x
xi
This thesis was 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 were as follows: Azis Ariffin, PhD Lecturer Faculty of Food Science and Technology Universiti Putra Malaysia (Chairman) Hasanah Mohd Ghazali, PhD Professor Faculty of Food Science and Technology Universiti Putra Malaysia (Member) AbdulKarim Sabo Mohammed, PhD Lecturer Faculty of Science and Technology Universiti Putra Malaysia (Member) Ainie Kuntom, PhD Lecturer Malaysian Palm Oil Board (Member)
HASANAH MOHD GHAZALI, PhD Professor and Dean
School of Graduate Studies Universiti Putra Malaysia
Date: 9 July 2009
xii
DECLARATION I hereby declare that the thesis is based on my original work except for quotation and
citations which have been duly acknowledged. I also declare that it has not been
previously or currently submitted for any other degree at UPM or other institutions.
MAHSA NAGHSHINEH Date: 10 June 2009
xiii
TABLE OF CONTENTS
Page DEDICATION ii ABSTRACT iii ABSTRAK vi ACKNOWLEDGEMENTS x APPROVAL xi DECLARATION xiiiLIST OF TABLES xviiLIST OF FIGURES xviiLST OF ABBREVIATION xix
CHAPTER
1 GENERAL INTRODUCTION 1 2 LITERATURE REVIEW 6 Lipids: Fats and Oils 6 Classification of Oils 7 Soft Oil 8 Olive Oil 9 Fatty Acid and
Triglyceride Composition
10
Unsaponifiable Compounds
11
Volatile Flavour Composition
11
Nutritional Effects 12 Factors Affecting
the Quality of Olive Oil
15
Hard Oil 16 Palm oil 17 Fatty Acid and
Triglyceride Composition
20
Unsaponifiable Compounds
21
Nutritional Effects 22 Application 24 Frying Process 25 Effect of Frying Process on 28
xiv
Physicochemical Properties of Oil and Fried Products
Oxidative Deterioration/Rancidity of Frying Media
30
Effect of Frying on Human Health 32 Factors Affecting Frying Process 33 Frying Media 35 Palm Olein as
Frying Oil 36
Olive Oil as Cooking Oil
38
Blended Oil 41 3 DETERMINATION OF PHYSICOCHEMICAL
PROPERTIES OF PALM OLEIN AND OILIVE OIL BLEND BEFORE FRYING PROCESS
43
Introduction 43 Materials and Methods 45 Materials 45 Methods 46 Preparation of Samples 46 Physicochemical Tests 47 Fatty Acids
Composition (FAC) 47
Melting Behavior 48 Cloud Point (CP) 48 Color 48 Apparent Viscosity 49 Iodine Value (IV) 49 Peroxide Value (PV) 50 Anisidine Value (AV) 50 Totox Value (TV) 51 Free Fatty Acids
(FFA) 51
Statistical Analysis 51 Results and Discussion 52 Physicochemical Properties of Palm Olein
and Olive Oil Blends 52
Fatty Acid Composition of POo -OO Blends
52
Melting Behavior 55 Viscosity 56 Cloud Point and Color 56 Iodine Value (IV) 58 Peroxide Value (PV) 58 Anisidine Value (AV) 59 Totox Value (TV) 60
xv
Free Fatty Acids (FFA) 61 Conclusions 61 4 EFFECTS OF FRYING CONDITION ON
PHYSICOCHEMICAL PROPERTIES OF PALM OIL AND OLIVE OIL BLENDS
63
Introduction 63 Materials and Methods 66 Materials 66 Preparation of Samples 66 Methods 66 Frying Process 66 Physicochemical Tests 67 Fatty Acids
Component (FAC) 67
Melting Behavior 67 Apparent Viscosity 68 Color 68 Total Polar Content
(TPC) 70
Iodine, Peroxide, Anisidine, Totox Value and Free Fatty Acid (FFA)
71
Statistical Analysis 71 Results and Discussion 72 Fatty Acids Composition (FAC) 72 Peroxide Value (PV) 76 Anisidine Value (AV) 78 Totox Value (TV) 79 Iodine Value (IV) 80 Free Fatty Acids (FFA) 81 Total Polar Content (TPC) 82 Melting Behavior 83 Viscosity 87 Color 88 Conclusions 89 5 EFFECTS OF TYPE OF FRYING OIL AND
STORAGE CONDITION ON PHYSICOCHEMICAL PROPERTIES OF PALM OLEIN AND OLIVE OIL BLENDS
91
Introduction 91 Materials and Methods 96 Materials 96 Methods 96 Preparation of Samples 96
xvi
Physicochemical Tests 96 Melting Behavior 96 Apparent Viscosity 97 Color 97 Iodine, Peroxide,
Anisidine, Totox Value and Free Fatty Acid (FFA)
97
Statistical Analysis 98 Results and Discussion 98 Peroxide Value (PV) 103 Anisidine Value (AV) 104 Totox Value (TV) 106 Iodine Value (IV) 107 Free Fatty Acids (FFA) 108 Melting Behavior 109 Viscosity 110 Color 111 Conclusions 112 6 CONCLUSIONS AND RECOMMENDATIONS 114 REFERENCES 119BIODATA OF STUDENT
161
xvii
LIST OF TABLES
Table Page
1 Ratio of blends 46
2 Some physicochemical properties of oil blends as function of POo:OO ratio
52
3 Fatty acid composition of palm olein- olive oil blends 53
4 Fatty acid composition of oils used for the frying process 73
5 Quality changes in RBD palm olein and olive oil blends during frying
74
6 The significance of each independent variable effect indicated by using F-ratio and p-value
75
7 Quality changes in RBD palm olein and olive oil blends during frying
85
8 The changes in chemical properties of RBD palm olein and olive oil blends during storage
99
9 The changes in physical properties of RBD palm olein and olive oil blends during storage
101
10 The significance of each independent variable effect shown by F-ratio and p-value
103
xviii
LIST OF FIGURES
Figure Page
1 Gas chromatogram showing the fatty acid composition of palm olein oil
54
2 Gas chromatogram showing the fatty acid composition of olive oil
54
3 DSC thermogram indicating the thermal behavior of oil blends
55
4 Effect of POo:OO ratio on the apparent viscosity of POo -OO oil blends
56
5 Effect of POo: OO ratio on the iodine value and cloud point of POo -OO oil blends
57
6 Effect of POo: OO ratio on peroxide value and anisidine value of POo -OO oil blends
59
7 Flow-chart for frying procedure
68
8 DSC thermogram showing thermal behavior of control oil (100% Palm Olein)
86
9 DSC thermogram showing thermal behavior of oil blend 1 (POo: OO, 75:25)
86
10 DSC thermogram showing thermal behavior of oil blend 1 (POo: OO, 50:50)
87
xix
LIST OF ABBREVIATION
AOCS American Oil Chemists’ Society
AV Ansidine value CD
Cloud point
DSC Differential scanning calorimetry
EVOO
Extra virgin olive oil
FAC Fatty acid composition
FFA Free fatty acids
IV Iodine value
MPOB Malaysian Palm Oil Board
Max Maximum
Min Minimum
MUFA Mono unsaturated fatty acid
OO Olive oil
PO Palm oil
POo Palm olein oil
PORIM Palm Oil Research Institute Malaysia
PV Peroxide value
PUFA Poly unsaturated fatty acid
RBO
Rice bran oil
RDB Refined bleached and deodorized
RSM Response surface methodology
SBO Soy been oil
xx
xxi
SDD Standard deviation of difference
SMP Slip melting point
TAG Triacylglycerol
TPC Total polar component
TV Totox value
VOO
Virgin olive oil
CHAPTER 1
GENERAL INTRODUCTION
Oil is a triacylglycerol (TAG) consisting of a glycerol esterified to three saturated and/or
unsaturated fatty acids. Oil may be classified as hard or soft oil depending on the
proportion of saturated to unsaturated fatty acids (Erickson, 1996). The term ‘soft oils’
is used to describe a group of oil containing TAG with two or three unsaturated fatty
acids that tend to be liquid at any temperature from 0º C. Soft oils such as corn oil, olive
oil, soybean oil and grape seed oil contain the high percentage of unsaturated fatty acids
(> 80%) (Che Man et al., 2005). The soft oils containing high concentration level of
unsaturated fatty acids have low melting point, thus remaining physically stable oils.
Due to high content of unsaturated fatty acids, soft oils are easily oxidized, thus showing
the chemically unstable oils. Perhaps the degree of oxidation decreases with increasing
the content of saturated fatty acids in the soft oils.
The term ‘hard oils’ is used to describe a group of oil rich in saturated fatty acid that
may be in solid or semi-solid state at room temperature. Hard oils such as palm oil, palm
kernel oil, coconut oil usually contain the TAGs with two or three saturated fatty acids,
thus exhibiting low iodine value (IV) remaining solid at ambient temperature. The semi
solid status of palm and coconut oils implicates a mixture of solid and liquid oils. Hard
oils are shown to be solid at low temperatures; while they will be liquid at high
temperatures. Hard oils are not physically stable due to their high melting points.
1
Increasing the content of unsaturated fatty acids in the hard oils may allow them to be
liquid and remain in liquid form even at low temperature.
The deep fat frying method is the process in which food is cooked by immersion in hot
oil. It is considered to be the oldest and most common unit operation used in food
preparation, especially in the Mediterranean area. Deep fat frying is classified as a
multifunctional operation that consists in immersing a wet product in a high boiling
point liquid such as oil. This process leads to a double mass transfer: (i) water escape by
internal vaporization and (ii) oil adhesion and drainage during cooling as a result of both
water condensation and capillary pressure.
In addition, heat and mass transfer generates simultaneous food transformations: (i)
texturing due to the modification of the viscoelastic characteristics and the internal
mechanical properties and (ii) activation of non enzymatic browning known as Maillard
reactions. In fact, the aim of deep fat frying is to seal the food by immersing it in hot oil
so that all the flavours and juices are retained within the crispy crust. The quality of the
fried products depends not only on the frying conditions, such as temperature of the
heated oil, frying time, food weight and frying oil volume, but also on the types of oil
and the kind of food used. During the frying process, there are many physicochemical
changes in food as well as in oil (Valdés and García, 2006).
During the frying process, the physical, chemical, and sensory characteristics of foods
will be modified. Texture, color and oil content are the main quality parameters of fried
2
potatoes. Texture is a sensory attribute of uppermost importance for potato preference
and it is a critical parameter for fried potato quality (Ross and Scanlon, 2004). Good-
quality French fries must have a crispy crust of about 1-2 mm where most of the oil is
located, and a wet, soft center, like a cooked potato. For potato chips, a very crispy
texture is expected all way through since crispness is an indicator of freshness and high
quality. The texture of potato is found to be directly related to specific gravity, total
solids, starch content, cell size, and surface area and pectin (Troncoso and Pedreschi,
2007). Textural changes during frying are the result of many physical, chemical, and
structural changes produced in this complex process unit operation.
Atmospheric deep-fat frying necessarily occurs at high temperatures under atmospheric
pressure. Surface darkening and many adverse reactions take place at the elevated
temperature before the food is fully cooked or dried. As a result of the oil deterioration
during the long frying process, the oil sustains some physical changes: the color
darkens, the viscosity increases, and smoke appears. This is mainly due to three
different factors: the moisture of food which may cause hydrolysis with free fatty acid
formation; the atmospheric oxygen that enters the oil from the surface of the container
and the high temperature at which the operation takes place. For instance, color
development only begins when sufficient amount of drying has occurred in potato slices
and depends also on the drying rate and heat transfer coefficient during the different
stages of frying. Color is visually considered as one of the most important parameters to
determine the quality of fried potatoes. The color changes in fried potatoes is the result
3
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