UNIVERSITI PUTRA MALAYSIA EFFECTS OF FRYING AND STORAGE CONDITIONS ON PHYSICOCHEMICAL PROPERTIES OF PALM OLEIN AND OLIVE OIL BLENDS MAHSA NAGHSHINEH

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1 UNIVERSITI PUTRA MALAYSIA EFFECTS OF FRYING AND STORAGE CONDITIONS ON PHYSICOCHEMICAL PROPERTIES OF PALM OLEIN AND OLIVE OIL BLENDS MAHSA NAGHSHINEH FSTM

2 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

3 Especially dedicated to my beloved father, mother, brother and my dear husband. ii

4 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 Faculty : Associate Professor Azis Ariffin, PhD : 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

5 (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 O 2 /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 O 2 /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

6 (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 O 2 /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 O 2 /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

7 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 Fakulti : Professor Madya Azis Ariffin, PhD : 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

8 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 berturutturut. 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 O 2 /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 O 2 /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

9 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 O 2 /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 O 2 /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

10 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

11 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

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13 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

14 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

15 TABLE OF CONTENTS Page DEDICATION ABSTRACT ABSTRAK ACKNOWLEDGEMENTS APPROVAL DECLARATION LIST OF TABLES LIST OF FIGURES LST OF ABBREVIATION ii iii vi x xi xiii xvii xvii 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 10 Triglyceride Composition Unsaponifiable 11 Compounds Volatile Flavour 11 Composition Nutritional Effects 12 Factors Affecting 15 the Quality of Olive Oil Hard Oil 16 Palm oil 17 Fatty Acid and 20 Triglyceride Composition Unsaponifiable 21 Compounds Nutritional Effects 22 Application 24 Frying Process 25 Effect of Frying Process on 28 xiv

16 Physicochemical Properties of Oil and Fried Products Oxidative Deterioration/Rancidity of Frying 30 Media Effect of Frying on Human Health 32 Factors Affecting Frying Process 33 Frying Media 35 Palm Olein as 36 Frying Oil Olive Oil as 38 Cooking Oil Blended Oil 41 3 DETERMINATION OF PHYSICOCHEMICAL 43 PROPERTIES OF PALM OLEIN AND OILIVE OIL BLEND BEFORE FRYING PROCESS Introduction 43 Materials and Methods 45 Materials 45 Methods 46 Preparation of Samples 46 Physicochemical Tests 47 Fatty Acids 47 Composition (FAC) 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 51 (FFA) Statistical Analysis 51 Results and Discussion 52 Physicochemical Properties of Palm Olein 52 and Olive Oil Blends Fatty Acid Composition of POo -OO 52 Blends 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

17 Free Fatty Acids (FFA) 61 Conclusions 61 4 EFFECTS OF FRYING CONDITION ON 63 PHYSICOCHEMICAL PROPERTIES OF PALM OIL AND OLIVE OIL BLENDS Introduction 63 Materials and Methods 66 Materials 66 Preparation of Samples 66 Methods 66 Frying Process 66 Physicochemical Tests 67 Fatty Acids 67 Component (FAC) Melting Behavior 67 Apparent Viscosity 68 Color 68 Total Polar Content 70 (TPC) Iodine, Peroxide, 71 Anisidine, Totox Value and Free Fatty Acid (FFA) 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 91 STORAGE CONDITION ON PHYSICOCHEMICAL PROPERTIES OF PALM OLEIN AND OLIVE OIL BLENDS Introduction 91 Materials and Methods 96 Materials 96 Methods 96 Preparation of Samples 96 xvi

18 Physicochemical Tests 96 Melting Behavior 96 Apparent Viscosity 97 Color 97 Iodine, Peroxide, 97 Anisidine, Totox Value and Free Fatty Acid (FFA) 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 CONCLUSIONS AND RECOMMENDATIONS 114 REFERENCES 119 BIODATA OF STUDENT 161 xvii

19 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 6 The significance of each independent variable effect indicated by using F-ratio and p-value 7 Quality changes in RBD palm olein and olive oil blends during frying 8 The changes in chemical properties of RBD palm olein and olive oil blends during storage 9 The changes in physical properties of RBD palm olein and olive oil blends during storage 10 The significance of each independent variable effect shown by F-ratio and p-value xviii

20 LIST OF FIGURES Figure 1 Gas chromatogram showing the fatty acid composition of palm olein oil 2 Gas chromatogram showing the fatty acid composition of olive oil Page 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 5 Effect of POo: OO ratio on the iodine value and cloud point of POo -OO oil blends 6 Effect of POo: OO ratio on peroxide value and anisidine value of POo -OO oil blends Flow-chart for frying procedure 68 8 DSC thermogram showing thermal behavior of control oil (100% Palm Olein) 9 DSC thermogram showing thermal behavior of oil blend 1 (POo: OO, 75:25) 10 DSC thermogram showing thermal behavior of oil blend 1 (POo: OO, 50:50) xix

21 LIST OF ABBREVIATION AOCS AV CD DSC EVOO FAC FFA IV MPOB Max Min MUFA OO PO POo PORIM PV PUFA RBO RDB RSM SBO American Oil Chemists Society Ansidine value Cloud point Differential scanning calorimetry Extra virgin olive oil Fatty acid composition Free fatty acids Iodine value Malaysian Palm Oil Board Maximum Minimum Mono unsaturated fatty acid Olive oil Palm oil Palm olein oil Palm Oil Research Institute Malaysia Peroxide value Poly unsaturated fatty acid Rice bran oil Refined bleached and deodorized Response surface methodology Soy been oil xx

22 SDD SMP TAG TPC TV VOO Standard deviation of difference Slip melting point Triacylglycerol Total polar component Totox value Virgin olive oil xxi

23 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

24 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

25 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). Goodquality 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