Lipids, Fats, and Oils

131 5 Lipids, Fats, and Oils Ioannis S. Arvanitoyannis, Theodoros H. Varzakas, Sotirios Kiokias, and Athanasios E. Labropoulos CONTENTS 5.1 Introduction .......................................................................................................................... 132 5.1.1 Fatty Acids ................................................................................................................ 133 5.1.2 Saturated Fatty Acids................................................................................................ 133 5.1.3 Unsaturated Fatty Acids ........................................................................................... 134 5.1.4 Acylglycerols ............................................................................................................ 134 5.2 Major Oils and Fats .............................................................................................................. 134 5.2.1 Oils and Fats of Vegetable Origin ............................................................................ 139 5.2.1.1 Olive Oil ..................................................................................................... 139 5.2.1.2 Corn Oil ..................................................................................................... 139 5.2.1.3 Soybean Oil ................................................................................................ 139 5.2.1.4 Sunfl ower Oil ............................................................................................. 142 5.2.1.5 Cottonseed Oil ........................................................................................... 142 5.2.1.6 Wheat Germ Oil ........................................................................................ 142 5.2.1.7 Rapeseed or Canola Oil ............................................................................. 143 5.2.1.8 Palm and Palm Kernel Oil ......................................................................... 143 5.2.1.9 Saffl ower Oil .............................................................................................. 144 5.2.1.10 Coconut Oil ................................................................................................ 144 5.2.1.11 Cocoa Butter .............................................................................................. 144 5.2.1.12 Sesame Oil ................................................................................................. 145 5.2.2 Oils and Fats of Animal Origin ................................................................................ 145 5.2.2.1 Butter .......................................................................................................... 145 5.2.2.2 Lard ............................................................................................................ 146 5.2.2.3 Tallow......................................................................................................... 146 5.2.2.4 Ghee ........................................................................................................... 146 5.2.2.5 Fish Oil ...................................................................................................... 147 5.3 Physical Parameters .............................................................................................................. 148 5.3.1 Crystallization, Melting Point, and Polymorphism .................................................. 148 5.3.1.1 Crystallization ............................................................................................ 148 5.3.1.2 Melting Point .............................................................................................. 149 5.3.1.3 Polymorphism ............................................................................................ 149 5.3.2 Density, Viscosity, and Refractive Index .................................................................. 149 5.3.2.1 Density ....................................................................................................... 149 5.3.2.2 Viscosity..................................................................................................... 150 5.3.2.3 Refractive Index ......................................................................................... 150 5.4 Chemical Parameters ............................................................................................................ 150 5.4.1 Oxidation .................................................................................................................. 150 132 Advances in Food Biochemistry 5.4.1.1 Autoxidation ............................................................................................... 150 5.4.1.2 AzoInitiated Oxidation ............................................................................. 151 5.4.1.3 Photosensitized Oxidation ......................................................................... 151 5.4.1.4 Metal Catalyzed Oxidation ........................................................................ 152 5.4.1.5 Enzyme Catalyzed Oxidation .................................................................... 152 5.4.1.6 Decomposition of Hydroperoxides ............................................................ 153 5.4.1.7 Physical Aspects—Lipid Oxidation in Food Emulsions ........................... 153 5.4.2 Antioxidant Activity of Carotenoids......................................................................... 154 5.4.2.1 Carotenoids as Radical Scavengers—Mechanism of Antioxidant Action ..................................................................................... 154 5.4.2.2 Reactivity of Carotenoids Toward Free Radicals—Effect of Structure on Scavenging Activity .............................................................. 155 5.4.2.3 Oxidative Degradation of Carotenoids by Free Radicals .......................... 156 5.4.2.4 Oxygen Quenching Activity of Carotenoids on OilPhotooxidation ......... 156 5.4.3 Natural Antioxidants Tested ..................................................................................... 157 5.4.3.1 Tocopherols and Tocotrienols .................................................................... 157 5.4.3.2 Ascorbic Acid and Ascorbyl Palmitate ...................................................... 159 5.4.3.3 OliveOil Phenolics .................................................................................... 160 5.5 Legislation for Oils and Fats ................................................................................................. 161 5.5.1 EU Legislation for Oils and Fats .............................................................................. 161 5.5.2 U.S. Legislation Related to Oil ................................................................................. 162 5.5.3 Canada Legislation Focused on Oil .......................................................................... 165 5.6 Authenticity of Oils and Fats ................................................................................................ 166 5.6.1 Authenticity of Vegetable Oils and Fats ................................................................... 166 5.6.1.1 Olive Oil Authenticity ................................................................................ 166 5.6.1.2 Maize Oil Authenticity .............................................................................. 181 5.6.1.3 Rapeseed Oil Authenticity ......................................................................... 181 5.6.1.4 Sesame Oil Authenticity ............................................................................ 181 5.6.1.5 Mustard Oil Authenticity ........................................................................... 182 5.6.1.6 Cocoa Butter Authenticity ......................................................................... 182 5.6.1.7 Palm, Palm Kernel, and Coconut Oils Authenticity .................................. 183 5.6.2 Authenticity of Animal Oils and Fats ....................................................................... 183 5.6.2.1 Butter Authenticity ..................................................................................... 184 5.6.2.2 Lard Authenticity ....................................................................................... 184 5.7 Functional and Health Properties of Fats and Oils in Foods ................................................ 185 5.7.1 Functional Issues ...................................................................................................... 185 5.7.2 Health Issues ............................................................................................................. 187 5.7.3 Process and Application Issues ................................................................................. 189 5.7.3.1 Shortenings “Puff Pastry” and Margarines ............................................... 189 5.7.3.2 Baker’s Margarines .................................................................................... 189 5.7.3.3 Pie’s Shortenings ........................................................................................ 189 References ...................................................................................................................................... 190 5.1 INTRODUCTION Lipids consist of a broad group of compounds that are generally soluble in organic solvents but only sparingly soluble in water. They are major components of adipose tissue, and together with proteins and carbohydrates, they constitute the principal structural components of all living cells. Glycerol esters of fatty acids, which make up to 99% of the lipids of plant and animal origin, have been traditionally called fats and oils.1 The difference between oils and fats is that fats are solids at room temperatures.2 Lipids, Fats, and Oils 133 The majority of lipids are derivatives of fatty acids. In these socalled acyl lipids, the fatty acids are present as esters, and in some minor lipid groups in amide forms (Table 5.1). The acyl residue infl uences strongly the hydrophobicity and the reactivity of the acyl lipids. Some lipids act as building blocks in the formation of biological membranes, which surround cells and subcellular particles. Primarily, triacylglycerols are deposited in some animal tissues and organs of some plants. Lipid content in such storage tissues can rise to 15%–20% or higher and so serve as a commercial source for isolation of triacylglycerols.3 5.1.1 FATTY ACIDS Fatty acid is a carboxylic acid often with a long, unbranched aliphatic chain, which is either saturated or unsaturated. Carboxylic acids as short as butyric acid (four carbon atoms) are considered to be fatty acids, whereas fatty acids derived from natural fats and oils may be assumed to have at least eight carbon atoms, e.g., caprylic acid (octanoic acid). Fatty acids are aliphatic monocarboxylic acids derived from or contained in an esterifi ed form in an animal or vegetable fat, oil, or wax. Natural fatty acids commonly have a chain of 4–28 carbons (usually unbranched and even numbered), which may be saturated or unsaturated. By extension, the term is sometimes used to embrace all acyclic aliphatic carboxylic acids.4 5.1.2 SATURATED FATTY ACIDS Saturated fatty acids do not contain any double bonds or other functional groups along the chain. The term “saturated” refers to hydrogen, in that all carbons (apart from the carboxylic acid –COOH group) contain as many hydrogens as possible. Saturated fatty acids form straight chains and, as a result, can be packed together very tightly, allowing living organisms to store chemical energy very densely. The fatty tissues of animals contain large amounts of longchain saturated fatty acids.5 Fatty acids have an “oic” suffi x to the name of the acid but the suffi x is usually “ic.” The shortest descriptions of fatty acids include only the number of carbon atoms and double bonds in them TABLE 5.1 Lipid Classifi cation Classifi cation Categories Characteristics Acyl residue Simple lipids (not saponifi able) Free fatty acids — Isoprenoid lipids Steroids, carotenoids, monoterpenes Tocopherols — Acyl lipids (saponifi able) Mono, di, triacylglycerols Fatty acids, glycerol Phospholipids (phosphatides) Fatty acids, glycerol or sphingosine, phosphoric acid, organic base Glycolipids Fatty acids, glycerol or sphingosine, mono, di, or oligosaccharide Diol lipids Fatty acids, ethane, propane, or butane diol Waxes Fatty acids, fatty alcohol Sterol esters Fatty acids, sterol Neutralpolar Glycerophospholipids Fatty acids (>C12) Glyceroglycolipids Mono, di, or triacylglycerols Sphingophospholipids Sterols, sterol esters Sphingoglycolipids Carotenoids, waxes, tocopherols 134 Advances in Food Biochemistry (e.g., C18:0 or 18:0). C18:0 means that the carbon chain of the fatty acid consists of 18 carbon atoms, and there are no (zero) double bonds in it, whereas C18:1 describes an 18carbon chain with one double bond in it. Each double bond can be in either a cis or trans conformation and in a different position with respect to the ends of the fatty acid; therefore, not all C18:1s, for example, are identical. If there are one or more double bonds in the fatty acid, it is no longer considered saturated, but rather mono or polyunsaturated.6 The characteristics of saturated fatty acids are given in Table 5.2. 5.1.3 UNSATURATED FATTY ACIDS Unsaturated fatty acids are of similar form, except that one or more allyl functional groups exist along the chain, with each alkene substituting a singlebonded “–CH2–CH2–” part of the chain with a doublebonded “–CH=CH–” portion. The two next carbon atoms in the chain that are bound to either side of the double bond can occur in a cis or trans confi guration.7 A cis confi guration means that adjacent carbon atoms are on the same side of the double bond. The rigidity of the double bond freezes its conformation and, in the case of the cis isomer, causes the chain to bend and restricts the conformational freedom of the fatty acid. The more double bonds the chain has in the cis confi guration, the less fl exibility it has. When a chain has many cis bonds, it becomes quite curved in its most accessible conformations.8 For example, oleic acid has one double bond, and linoleic acid with two double bonds has a more pronounced bend. αLinolenic acid, with three double bonds, favors a hooked shape. The effect of this is that in restricted environments, such as when fatty acids are part of a phospholipid in a lipid bilayer, or triglycerides in lipid droplets, cis bonds limit the ability of fatty acids to be closely packed, and therefore could affect the melting temperature of the membrane or of the fat.9 A trans confi guration, by contrast, means that the next two carbon atoms are bound to opposite sides of the double bond. As a result, they do not cause the chain to bend much, and their shape is similar to straight saturated fatty acids.10 In most naturally occurring unsaturated fatty acids, each double bond has 3n carbon atoms after it, for some n, and all are cis bonds. Most fatty acids in the trans confi guration (trans fats) are not found in nature and are the result of human processing. The differences in geometry between the various types of unsaturated fatty acids, as well as between saturated and unsaturated fatty acids, play an important role in biological processes, and in the construction of biological structures (such as cell membranes).11 The characteristics of unsaturated fatty acids are given in Table 5.3. 5.1.4 ACYLGLYCEROLS Neutral fats are mono, di, and triesters of glycerol with fatty acids, and are termed monoacylglycerols, diacylglycerols, and triacylglycerols, respectively. They are designated as neutral lipids. Edible oils or fats consist nearly completely of triacylglycerols.3 Although glycerol by itself is a completely symmetrical molecule, the central carbon atom acquires chirality (asymmetry) if one of the primary hydroxyl groups (on carbons 1–3) is esterifi ed, or if the two primary hydroxyls are esterifi ed to different acids.1 5.2 MAJOR OILS AND FATS All oils and fats, with their high carbon and hydrogen content, can be traced back to organic sources. Oils and fats are also produced by plants, animals, and other organisms through organic processes and these oils are remarkable in their diversity.12 Oils are fats that are liquids at room temperature. Solid fats are fats that are solids at room temperature, like butter and shortening. Solid fats come from many animal foods and can be made from vegetable oils through a process called hydrogenation.13 Lipids, Fats, and Oils 135 TABLE 5.2 Saturated Fatty Acids IUPAC Name Common Name Abbreviation Chemical Structure Structure Melting Point (°C) Butanoic acid Butyric acid 4:0 CH3(CH2)2COOH O OH −7.9 Pentanoic acid Valeric acid 5:0 CH3(CH2)3COOH OH O −34.5 Hexanoic acid Caproic acid 6:0 CH3(CH2)4COOH O OH −3.9 Heptanoic acid Enanthic acid 7:0 CH3(CH2)5COOH O OH −7.5 Octanoic acid Caprylic acid 8:0 CH3(CH2)6COOH O OH 16.3 Nonanoic acid Pelargonic acid 9:0 CH3(CH2)7COOH O OH 12.4 Decanoic acid Capric acid 10:0 CH3(CH2)8COOH O OH 31.3 Dodecanoic acid Lauric acid 12:0 CH3(CH2)10COOH O OH 44 Tetradecanoic acid Myristic acid 14:0 CH3(CH2)12COOH O OH 54.4 Hexadecanoic acid Palmitic acid 16:0 CH3(CH2)14COOH O OH 62.9 (continued) 136 Advances in Food Biochemistry TABLE 5.2 (continued) Saturated Fatty Acids IUPAC Name Common Name Abbreviation Chemical Structure Structure Melting Point (°C) Heptadecanoic acid Margaric acid 17:0 CH3(CH2)15COOH O OH 61.3 Octadecanoic acid Stearic acid 18:0 CH3(CH2)16COOH O OH 69.6 Eicosanoic acid Arachidic acid 20:0 CH3(CH2)18COOH O O H 75.4 Docosanoic acid Behenic acid 22:0 CH3(CH2)20COOH CH3 O HO 80.0 Tetracosanoic acid Lignoceric acid 24:0 CH3(CH2)22COOH COOH 84.2 Hexacosanoic acid Cerotic acid 26:0 CH3(CH2)24COOH O OH 87.7 Lipids, Fats, and Oils 137 TABLE 5.3 Unsaturated Fatty Acids Common Name Abbreviation Chemical Structure Structure Family (w) Family (D) Melting Point (°C) Myristoleic acid 14:1 CH3(CH2)3CH=CH(CH2)7COOH O OH ω5 cisΔ9 — Palmitoleic acid 16:1 CH3(CH2)5CH=CH(CH2)7COOH O OH ω7 cisΔ9 0.1 Oleic acid 18:1 CH3(CH2)7CH=CH(CH2)7COOH O OH ω9 cisΔ9 13.4 Linoleic acid 18:2 CH3(CH2)4CH=CHCH2CH=CH (CH2)7COOH O 1 9 12 6 1 HO ω ω6 cis, cisΔ9, Δ12 −5 αLinolenic acid 18:3 CH3CH2CH=CHCH2CH=CHCH2 CH=CH(CH2)7COOH O α ω HO1 9 9 6 3 1 12 15 18 ω3 cis, cis, cisΔ9, Δ12, Δ15 −11 γLinolenic acid 18:3 (CH=CHCH2)3CH2CH2CH2COOH O HO 1 6 9 12 6 1 ω ω6 cis, cis, cisΔ6, Δ9, Δ12 — Arachidonic acid 20:4 CH3(CH2)4CH=CHCH2CH=CHCH2 CH=CHCH2CH=CH(CH2)3COOH O HO1 5 8 11 14 6 1 ω ω6 cis, cis, cis, cis Δ5, Δ8, Δ11, Δ14 −49.5 Eicosapentaenoic acid (EPA) 20:5 CH3CH2CH=CHCH2CH=CH CH2CH=CHCH2CH=CHCH2 CH=CH(CH2)3COOH 1 5 8 11 14 17 20 6 3 1 O HO ω α ω3 cis, cis, cis, cis, cisΔ5, Δ8, Δ11, Δ14, Δ17 — (continued) 138 Advances in Food Biochemistry TABLE 5.3 (continued) Unsaturated Fatty Acids Common Name Abbreviation Chemical Structure Structure Family (w) Family (D) Melting Point (°C) Erucic acid 22:1 CH3(CH2)7CH=CH(CH2)11COOH O OH ω9 cisΔ13 34.7 Docosahexaenoic acid (DHA) 22:6 CH3CH2CH=CHCH2CH=CHCH2 CH=CHCH2CH=CHCH2CH=CH CH2CH=CH(CH2)2COOH 1 4 7 10 13 16 19 3 1 HO O ω ω3 cis, cis, cis, cis, cis, cisΔ5, Δ8, Δ11, Δ14, Δ17 — Nervonic acid 24:1 (CH2)12COOH O OH ω9 cisΔ15 42.5 Lipids, Fats, and Oils 139 5.2.1 OILS AND FATS OF VEGETABLE ORIGIN The vegetable oils may be subdivided into three categories: (1) byproducts, where the crop is grown for another purpose other than seed oil, e.g., cotton (fabric), (2) three crops, which are generally slow to mature but then produce crops regularly for many years (olive, palm, and coconut), (3) crops, which have to be replanted each year to produce an annual harvest and where decisions about cultivation are made each sowing season by a large number of individual farmers (rape, sunfl ower, sesame, etc.).14 Typical fatty acid compositions of vegetable oils and fats are summarized in Table 5.4. 5.2.1.1 Olive Oil Over 750 million olive trees are cultivated worldwide, about 95% of those in the Mediterranean region. Most of the global production comes from Southern Europe, North Africa, and the Middle East. Of the European production, 93% comes from Spain, Italy, Turkey, and Greece. Spain’s production alone accounts for 40%–45% of the world production, which was 2.6 million metric tons in 2002.15 In olive oil–producing countries, the local production is generally considered the fi nest. The olive oil extraction is carried out with technological industrial processes (continuous or discontinuous), even though the quality and the quantity of the obtained oil are still to be optimized.16 The most traditional way of making olive oil is by grinding olives. Green olives produce bitter oil and overly ripened olives produce rancid oil, so care is taken to make sure the olives are perfectly ripened. First, the olives are ground into an olive paste using large mills. The olive paste generally stays under the mills for 30–40 min. The oil collected during this part of the process is called virgin oil. After grinding, the olive paste is spread on fi ber disks, which are stacked on top of each other, and then placed into the press. Pressure is then applied onto the disk to further separate the oil from the paste. This second step produces a lower grade of oil.17 The production of olive oil is shown in Figure 5.1. The oil is characterized by a high level of oleic acid with Codex ranges of 8%–20% for palmitic acid, 55%–83% for oleic acid and 4%–21% for linoleic acid.18 Extra virgin olive oil has a perfect fl avor and odor with a maximum acidity of 1% (as oleic acid). Fine virgin oil also has a perfect fl avor and odor with a maximum acidity of 2%. Semifi ne or ordinary virgin oil has good fl avor and odor and a maximum acidity of 3.3% with a 10% margin of tolerance. Virgin olive oil with an offfl avor or offodor and acidity >3.3% is designated lampante. Refi ned olive oil, obtained from virgin olive oil by refi ning methods which do not affect fatty acid or glycerol ester composition, should have acidity 3.3% is designated lampante Refined olive oil, obtained from virgin olive oil by refining methods which not affect fatty acid or glycerol ester composition, should have acidity [...]... acid < oleuropein < hydroxytyrosol 5.5 LEGISLATION FOR OILS AND FATS 5.5.1 EU LEGISLATION FOR OILS AND FATS This Directive 76/621/EEC (entry into force 28/7/1976) shall apply: (a) to oils, fats, and mixtures thereof which are intended as such for human consumption, (b) to compound foodstuffs to which oils, fats, or mixtures thereof have been added and the overall fat content of which exceeds 5% Member... refined olive oils and virgin olive oils, and (d) olive-pomace oil Only extra virgin and virgin olive oil may bear a designation of origin on the labeling.192 Some representative points and comments (repeals, modifications, and amendments) of the directive/regulations for oils and fats are given in Table 5.7 5.5.2 U.S LEGISLATION RELATED TO OIL An international agreement on olive oil and table olives... manufacturers and wholesalers of any edible oil product and prescribing the form, terms, and conditions thereof and the fees to be paid therefore, and providing for the renewal, suspension, and cancellation thereof, (c) prescribing standards for the operation and maintenance of premises and facilities in which any edible oil product is manufactured, packed, or stored, (d) prescribing the standards of... usefulness of cocoa butter for this purpose is related to its fatty acid and triacylglycerol compositions The major triacylglycerols are symmetrical disaturated oleic glycerol esters of the type SOS and include POP (18%–23%), POSt (36%–41%), and StOSt (23%–31%).55,56 Cocoa butter Lipids, Fats, and Oils 145 commands a good price and cheaper alternatives have been developed The annual production of cocoa... include saturated (14:0, 16:0, and 18:0), monounsaturated (16:1, 18:1, 20:1, and 22:1) and n–3 polyene members (18:4, 20:5, 22:5, and 22:6) Fish oils are easily oxidized and are commonly used in fat spreads only after partial hydrogenation.79 However, they are the most readily available sources of n–3 polyene acids, especially, EPA and DHA, and with appropriate refining procedures and antioxidant addition... extraction, and table olive processing: (a) to encourage research and development to elaborate techniques that could: (i) modernize olive husbandry and the olive-products industry through technical and scientific planning, (ii) improve the quality of the products obtained Title Establishment of a common organization of the market in oils and fats The characteristics of olive oil and olive-residue oil and on... force 5/6/2003) Lipids, Fats, and Oils 163 Marketing standards for olive oil Marketing standards for olive oil Standards for spreadable fats Regulation (EC) No 2815/98 (entry into force 31/10/2001) Regulation (EC) No 1019/2002 (entry into force 1/11/2002) Title Regulation (EC) No 2991/94 (entry into force 1/1/1996) Directive/Regulation • Application to milk fats and fats composed of plant and/ or animal... Points and Comments) with Regard to Oils and Fats The Regulation (EC) No 1964/2002 (entry into force 1/7/2002) makes clear that the products which were legally produced, were labeled and got into circulation before 1/1/2003 will be marketed until the consumption of the stocks Comments 164 Advances in Food Biochemistry Lipids, Fats, and Oils 165 TABLE 5.8 International Agreement for Olive Oil and Table... advancement in understanding their technological and biological effects The mechanism by which they protect lipid systems from damage due to photooxidation appears to depend largely on physical Lipids, Fats, and Oils 157 quenching and to a much lesser extent on chemical reaction.155 According to Bradley and Min,156 the addition of various carotenoids to foods containing unsaturated oils improves their... to every edible oil product and class of edible oil product designated in the regulations This act was amended in 1994, 1999, and 2001 5.6 AUTHENTICITY OF OILS AND FATS A variety of physical and chemical tests have been developed to determine the authenticity of fats and oils Classical physical and chemical tests have been supplemented with, or supplanted by, newer chemical and instrumental techniques,