Trans Fats Replacement Solutions

Epidemiological studies have continued to increase awareness of how trans fats impact human nutrition and health. Because of the adverse effects, trans fats labeling regulations were introduced in 2006. Since then, the fats and oils industry and food product manufacturers have researched and implemented a number of novel, practical, and cost-effective solutions for replacing trans fats with alternate products. This book provides a comprehensive understanding of the trans fats chemistry, labeling regulations, and trans fat replacement technologies. It also deals with world-wide trends and scenarios in terms of regulations and trans fat replacement solutions.

• Includes details on how trans fats became a part of our food chain, why they remain a health issue, and what replacement solutions exist
• Offers in-depth analysis of the structure, properties, and functionality of fats and oils
• Describes trans fats regulations and scenarios in different geographies around the world

• Language: English
• Publisher: Elsevier Science
• Release date: Apr 22, 2014
• ISBN: 9781630670337

Book preview

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Trans Fats: Health, Chemistry, Functionality, and Potential Replacement Solutions

Dharma R. Kodali,     Department of Bioproducts and Biosystems Engineering, University of Minnesota, St. Paul, Minnesota, United States

Introduction

Natural oils and fats are liquids or semisolids consisting primarily of triacylglycerols (TAGs). In the literature, triacylglycerols are often referred to as triglycerides, even though this latter term is less accurate in representing the molecular structure of this class of compounds. The distinction between fats and oils is a nuance seen in their physical state at ambient temperature. The major sources of oils and fats are from animals and plants. Greater than 90% of commercial oils and fats used for human consumption are plant-derived vegetable oils. Unrefined natural oils and fats, after extraction from the source, comprise mostly TAGs containing less than 5% of minor components such as sterols, phospholipids, tocopherols, fatty acids, and partial glycerol esters. The minor components and their concentration in the crude oil depend on the origin and method of oil extraction. The crude oils are subjected to various processing steps such as degumming and alkali refining (to remove phospholipids and fatty acids), bleaching (to remove colored pigments and polar matter), and steam stripping or deodorization (to remove volatile components) to make them suitable for human consumption. Oils subjected to these steps are usually referred to as RBD (refined, bleached, and deodorized) oils and contain about 99% TAGs.

The major vegetable oils of commerce are soybean, cottonseed, canola, sunflower, corn, peanut, palm, palm kernel, and coconut. Other vegetable oils like olive, rice bran, safflower, sesame, and other specialty oils are not used extensively due to availability and cost. A typical chemical structure of TAG is shown in Figure 1.1. The TAG contains a glycerol backbone with three hydroxyls esterified to three long linear carboxylic acids called fatty acids. The glycerol portion of TAG is constant in all oils and fats. The type of fatty acid structure and the position of esterification on glycerol differ from one TAG to another. Glycerol is a prochiral molecule capable of forming two different TAG stereoisomers, when esterified with different fatty acid chains at the 1 and 3 positions. These stereoisomers, when differentiated from one another, are identified as stereospecifically numbered, sn-glycerol derivatives (Kodali et al., 1984, 1989a). Even though biological systems can recognize the isomeric sn-glycerol derivatives, the physical and chemical properties of these isomers are very similar. For all functional and practical purposes they are treated as one and the same.

Figure 1.1 A molecular structure of a TAG (fat/oil) showing the glycerol backbone region esterified with three different fatty acids: stearic (C18:0), oleic (C18:1), and linolenic (C18:3) acids.

Vegetable oils contain a mixture of specific TAG molecules of given concentrations. Fatty acid structures differ from each other in carbon chain length and the number of double bonds. Most of the naturally occurring fatty acids are even numbered, 4 to 24 carbon atoms long, because they are synthesized from two-carbon unit acetyl coenzyme A. More prevalent saturated fatty acids with no double bonds that occur in oils and fats are lauric (C12:0), myristic (C14:0), palmitic (C16:0), and stearic (C18:0) acids. The number in parentheses shows the number of carbon atoms corresponding to the fatty acid chain length. A zero after the number indicates that there are no double bonds. The predominant unsaturated fatty acids are oleic (C18:1), linoleic (C18:2), and linolenic (C18:3) acids. The numbers in parentheses show the carbon chain length followed by the number of double bonds. The position of double bonds in the chain and the double-bond configuration are also very important. In oleic acid, the position of unsaturation is at carbon-9, in linoleic it is at C9 and 12, and in linolenic it is at C9, 12, and 15. Most of the unsaturated fatty acids that occur in natural fats and oils, with few exceptions, have the double bonds in cis configuration. The fatty acids that contain a single double bond are referred to as monounsaturated and others with more than one double bond are polyunsaturated fatty acids. Even though there are hundreds of different fatty acids that occur in oils and fats, the fatty acids referred to previously are most common and abundant in natural oils and fats.

The predominant vegetable oils in commerce can be divided into three types based on carbon chain length: lauric, palmitic, and oleic. The lauric oils, mostly coconut and palm kernel oils, contain high levels of 12-carbon lauric acid. The common palmitic oil, palm oil, contains 16-carbon palmitic acid in high concentration. The lauric and palmitic oils are high in saturated fatty acids and are semisolids at ambient temperature. Because coconut, palm, and palm kernel oils are grown in hotter climates closer to the equator, they are referred to as tropical oils. Oleic oils predominantly contain 18-carbon fatty acids such as stearic, oleic, linoleic, and linolenic acids. The soybean, sunflower, canola, corn, and cottonseed oils belong in this category. The major types of edible oils that are consumed in North America are soybean, corn, and canola. Palm oil is not extensively used in the United States, but its use has been rising because it provides cost-effective trans-free solutions. Palm oil is more extensively used in Asian countries and, to a certain extent, in Europe. Soybean and palm are the two most abundantly available vegetable oils in the world, together accounting for 60% of the total worldwide vegetable oil production of close to 157 million tons per year. The use of various vegetable oils in a given geography mainly depends on what is grown in that area and the cost and availability. Their yields, production volumes, and major production geographies for the four major vegetable oils are given in Table 1.A. Oil palm is a perennial crop with the majority of oil coming from the fruit pericarp and minor quantities from the kernel. Because of the high oil yields and production volumes, palm oil tends to be more cost competitive compared to other oils. However, production of the other vegetable oils yields protein as a byproduct along with the oil, which has nutritional and economic value. Beyond the cost and availability, nutritional and functional characteristics of fats and oils play an important role in their selection and use.

Table 1.A

Major Vegetable Oils, Production Volumes, Yields, and Geography (Estimates 2012–13)

Defining vegetable oil composition by individual TAG molecular structure and concentration, rather than overall fatty acid composition of the oil, is more accurate but very cumbersome. Vegetable oils are identified by gross fatty acid composition (by weight). The fatty acid compositions of most edible oils used in commerce are shown in Table 1.B. The fatty acid compositions of various vegetable oils are determined by plant variety and genetics. In a given variety, the fatty acid composition changes a little due to geography and environmental factors. Because of this variation, the fatty acid composition is often expressed as a range rather than as a single number. The fatty acid compositions in Table 1.B are given in average weight percent.

Table 1.B

Fatty Acid Composition (wt.%) of Conventional and High-Oleic Oils

aShort chain C6:0 hexanoic (caproic), C8:0 octanoic (caprylic), C10:0 decanoic (capric) fatty acids.

bLong chain C20:0 eicosanoic (arachidic), C22:0 docosanoic (behenic), C22:1 cis C13 docosenoic (erucic), C24:0 tetracosanoic (lignoceric) fatty acids.

cVery high oleic.

Recent developments in biotechnology and plant breeding make it possible to develop new genetic varieties that yield oils with different fatty acid compositions than traditional oils. For example, the oil from regular canola is composed of 62% oleic acid, whereas the high-oleic and very high-oleic canola varieties are composed of about 75% and 84% oleic acid, respectively.

There are numerous review articles that deal with composition, processing, physical and chemical properties, and commercial aspects of oils and fats (Hasenhuettl, 1994; Technical Committee of the ISEO, 2006; Thomas, 2012). More comprehensive and detailed information is provided in Bailey’s (Hui, 1996). Another source of chemical and physical property information on various specific fatty acids, TAGs, and partial glycerol esters is The Lipid Handbook (Gunstone et al., 2007).

The primary purpose of this chapter is to provide comprehensive discussion of most of the aspects of trans fats: their health effects, chemistry, sources, properties, and functionality. First, a general overview of fats and oils and their functionality in foods is covered. This is followed by the discussion of the relationship between structure, properties, and functionality of TAG and its constituent fatty acids, leading to the creation of ideal designer fats that can meet the desired functional and nutritional needs. This chapter also provides various strategies to create trans fat replacement solutions, including the ideal designer fats with low saturates as a trans replacement solution.

Health Effects of Trans Fats

Coronary heart disease (CHD)—the narrowing of the inner walls of arteries caused by plaque buildup, thereby reducing the blood flow to the heart—has become the leading cause of death. Around the middle of the 20th century, there were numerous research studies that showed that saturated fat and cholesterol in the blood are major factors in cardiovascular disease. By 1985, the National Institute of Health (NIH) established that lowering the blood levels of low density lipoprotein (LDL), considered bad cholesterol, would reduce the risk of CHD (NIH, 1985). Based on an inordinate amount of scientific data, it is fairly well established that the reduction of LDL and increase in good cholesterol (high density lipoprotein, HDL) reduces the risk of CHD. It has become a common practice in the research investigations to compare the LDL to HDL ratio to assess the CHD risk.

In 1990, the Nutrition Labeling and Education Act (NLEA) provided the Food and Drug Administration (FDA) with the authority to require nutritional labeling. The initial NLEA regulations requiring food products to be labeled with nutrient and health claims became fully effective by 1994. By this time the overall fat consumption—specifically, saturated fats and animal fat–containing foods, and their association with CHD—came under public scrutiny. As a result, food companies replaced the animal fats that contain cholesterol with partially hydrogenated vegetable oils (PHVOs) that provide the necessary solid fat functionality and shelf life. Similarly, tropical oils high in saturated fatty acid, such as palm and palm fractions, have been replaced by PHVO as well. The timeline of the initial NLEA regulations and the consequent changes that influenced the use of PHVO-containing trans fats to replace the saturated fat and animal fat in food products and also the subsequent trans fat regulations and their replacement solutions are shown in Figure 1.2.

Figure 1.2 Chronology of nutrition and health regulations of saturated fats and trans fats and the consequent replacement solutions.

The hydrogenation process to produce PHVO has been in extensive use around the world from the middle of the 20th century. It has been used to functionalize vegetable oils to replace animal fats, which were the most versatile fats used in Western countries at that time. The PHVO technology also provided greater functional versatility for the food manufacturers and increased the shelf life of the food products. The replacement of animal fats and tropical oils containing saturated fats with PHVO was hastened by the NLEA regulations in 1990s because they were perceived to provide the necessary functionality without increasing the saturated fat.

Almost all the unsaturated fats from nature, except ruminant fats, contain a cis double bond, which is different from trans configuration found in PHVO. PHVO provided better functionality and shelf life, in addition to reduced saturated fat content on the label of food products, which gained greater public acceptance. This hastened the replacement of tropical oils, which contain higher concentrations of saturated fats and animal fats that contain cholesterol, with PHVO, thereby increasing trans fat consumption in the population. Before 1990, a few studies showed that trans fats behave differently than cis fats in elevating the cholesterol levels in blood (Vergroesen, 1975). However, in 1990, Mensink and Katan proved that trans fats raise LDL cholesterol and lower HDL cholesterol levels. Thereafter, a number of studies corroborated with these findings (Katan et al., 1995; Mensink et al., 1992). In 1999, Ascherio et al. summarized the nine randomized trials available at that time that directly compared the effects of trans fats with those of isocaloric amounts of cis fats. The meta-analysis of these trials clearly showed that the trans fats increase LDL cholesterol to levels similar to those produced by saturated fats and also decrease the HDL cholesterol levels. The net effect of trans fats on the LDL:HDL ratio is approximately double that of saturated fats. The effects of trans fats compared to saturated fats on LDL:HDL cholesterol as a percentage of energy intake of these fats are shown in Figure 1.3.

Figure 1.3 The effect of saturated fat and trans fat on the LDL:HDL cholesterol ratio compared to isocaloric amounts of cis fat. Based on Ascherio et al. (1999).

These findings of adverse health effects of trans fats on blood cholesterol levels compared to saturated fats were further confirmed by Mozaffarian et al. (2006); replacing saturated fats with trans fats up to 5% of energy intake linearly increased LDL cholesterol by 2 mg/dl while decreasing the HDL cholesterol by a similar amount. Later, the adverse effects of trans fats, as shown by the increase of the total cholesterol:HDL ratio, were clearly demonstrated by systematically replacing the saturated, monounsaturated, and polyunsaturated fats with trans fats (Mozaffarian and Clarke, 2009). Micha and Mozaffarian (2009) have shown the relative risk of trans fats and saturated fats on CHD with the consumption of these two fats as a percentage of energy compared to carbohydrates as the reference; this is shown in Figure 1.4. Both trans and saturated fats show a positive CHD risk increasing linearly with the consumption, whereas the intake of monounsaturated and polyunsaturated fats have a negative CHD risk. According to this study, the CHD risk of trans fat is 7 to 8 times greater than that of saturated fat, as shown in Figure 1.4.

Figure 1.4 Relative risk of CHD as a percentage of energy consumption of saturated fats and trans fats, compared to carbohydrate. Based on Micha and Mozaffarian (2009).

Recently, Brouwer et al. (2013) concluded that the detrimental effects of industrial trans fatty acids (i.e., PHVO) on heart health are beyond dispute. Considering the overwhelming evidence that trans fat consumption increases CHD risk, the FDA initiated trans fat labeling regulations. In July 2003, the FDA issued a final rule requiring a mandatory declaration on the nutritional label of the amount of trans fat present in foods, including dietary supplements. The declaration of trans fat is to be expressed as grams per serving to the nearest 0.5 gram increment below 5 grams and to the nearest gram increment above 5 grams (Moss, 2005). The trans fat regulations became effective on January 1, 2006. This development greatly influenced food product manufacturers in various geographical regions to either eliminate or reduce the trans fats in their products by adopting various trans fats alternatives, as elaborately described in this book. Considering the ill health effects of trans fats, Denmark took a more proactive measure and banned any food containing industrially produced trans fat at levels greater than 2% of total fat (Stender et al., 2006). This virtually eliminated the consumption of industrially produced trans fats in the Danish population very quickly. Beyond the adverse health effects, trans fats have virtually no nutritional benefits. Therefore, their removal from the food chain is imperative. On November 8, 2013, based on new scientific evidence and the findings of expert scientific panels, the FDA tentatively determined that partially hydrogenated oils (PHOs), which are the primary dietary source of industrially produced trans fats, are not generally recognized as safe (GRAS) for any uses in food (FDA, 2013). Here the PHOs include fats and oils derived from plants and animals. If the tentative determination is finalized, oil manufacturers would no longer be permitted to sell PHOs, either directly or as ingredients in other food products.

Extensive coverage of trans fats regulations appears in Chapter 3. The nutritional aspects of trans fats are discussed in depth in Chapter 4.

Structure, Properties, and Functionality of TAGs

The fats and oils properties and functionality ensue from the TAG structure and the overall TAG composition. Because TAG contains glycerol esterified to different fatty acids, understanding of the fatty acid structure and properties will lead to the influence of various structural features on the properties. The purpose of understanding the relationship between chemical structure and the ensuing properties and functionality is that desired functionality can be created through modification of TAG structure and/or composition. The general relationship between these three features is shown schematically in Figure 1.5.

Figure 1.5 Understanding the molecular origins of properties and functionality of TAG will help to manipulate the structure and composition to derive the desired functional fat for a given application.

As shown in Figure 1.5, the properties of a given fat or oil depend on the fatty acid composition and structure. In turn, the properties are responsible for the functionality required for a given application. The molecular origins of functionality can therefore be understood by relating the chemical structure to the molecular packing and physical properties.

Two structural features of fatty acids present in edible fats and oils, chain length and unsaturation, are important. The cis unsaturation present in oils plays a big role in the physical properties. The partial hydrogenation converts some of the cis unsaturation to trans, thereby modifying the properties and functionality.

Cis, Trans Isomers

The double bond (unsaturation) present in the fatty acid inhibits the rotation of carbons on either side and thereby fixes the configuration of atoms present on double-bond carbons. The rest of the chain is free to rotate on C-C single bonds. Because of this fixed geometry, the hydrogen atoms present on double-bond carbons can be on the same side (cis, in Latin) or on the opposite side (trans, in Latin). The cis and trans are written in italics to identify their Latin origin and to represent the chemical configuration as shown in Figure 1.6. Cis and trans isomers are geometric isomers; they differ from one another only in the way that the atoms are oriented in space. The double bond is rigid and creates a kink in the chain. The kink created by the cis configuration is a lot more pronounced, whereas the kink created by the trans isomer is relatively symmetrical and closer to a straight chain. Trans compounds have higher melting points than the corresponding cis isomers, reflecting the greater ease of crystal packing of the somewhat more symmetrical molecules. The interconversion of cis and trans takes place by the breaking and reformation of the double bond, which requires about 65 kcal/mole of energy. Because of this high energy barrier, the cis and trans isomerization does not occur easily unless assisted by a catalyst or high temperatures.

Figure 1.6 Cis, trans isomerism of a double bond under thermal conditions.

The cis isomer is more asymmetric than the corresponding trans isomer and cannot pack well into a crystal lattice. Because of this, the trans isomers have a higher density, lower solubility, and a higher melting point. Trans isomers are less sterically hindered and more thermodynamically stable than cis isomers. Therefore, the cis isomer can be transformed into a trans isomer by subjecting it to a high temperature. Very high temperatures provide enough energy to cause rotation about the double bond to convert a cis configuration into a thermodynamically more stable trans isomer, which is an irreversible process. During vegetable oil refining, the oil is subjected to steam deodorization to remove the volatile compounds. The high temperature conditions of deodorization cause trans isomerization. Because of this, most of the refined oils, even though not subjected to hydrogenation, contain as much as 1–2% of trans fats.

The unsaturated fatty acids present in the natural oils and fats are in the cis configuration. The cis isomers are relatively asymmetric and pack poorly in the crystal lattice due to a kink in the middle of the hydrocarbon chain. This kink in the middle of the chain reduces the interchain interactions in the solid state, thereby lowering the melting temperature and enthalpy. The position of the double bond in the middle of the chain most effectively decreases the melting temperature compared to either end of the fatty acid chain. Compared to cis double bonds, trans double bonds are relatively symmetric and pack better in the crystal lattice, so their melting temperature falls between the melting temperatures of saturated and cis-unsaturated fatty acids. A comparison of the molecular structures and melting temperatures of three fatty acids of 18-carbon chain length—oleic acid (cis-9 double bond), elaidic acid (trans-9 double bond), and stearic acid—illustrate this point. The influence of unsaturation and the type of unsaturation, cis versus trans, are shown in the space-filling models of stearic acid, oleic acid, and elaidic acid in Figure 1.7A. How the same molecular features influence the corresponding TAG, tristearoylglycerol (SSS), trioleoylglycerol (OOO), and trielaidoylglycerol (EEE) with space-filling models and their melting temperatures are shown in Figure 1.7B. The melting temperatures of fatty acids mimic the melting temperatures of the corresponding TAGs. Even though the molecular packing and crystal structures of fatty acids and their corresponding TAGs are different, the molecular forces responsible for the melting temperatures are similar.

Figure 1.7 The space-filling models of (A) fatty acids, stearic acid (C18:0), elaidic acid (C18:1 trans C9), and oleic acid (C18:1 cis C9), and (B) the corresponding mono-acid triacylglycerols: tristearoylglycerol (SSS), trielaedoylglycerol (EEE), and trioleoylglycerol (OOO).

Nature utilized the cis configuration to make the high molecular weight TAG molecules as large as 900 Daltons and still keep them in the liquid state at ambient temperature, even though the unsaturated oils contain lower energy content than their corresponding saturated fat. Biological processes occur more efficiently when the TAG molecules are more accessible to the enzymes while in a liquid state. Because of this, the fatty acid compositions of various vegetable oils reflect the climatic and geographic conditions. Tropical oils contain saturated fatty acids in higher concentration, whereas the oleic oils that are grown in temperate climates contain polyunsaturated fatty acids in greater concentration so that the oil can be in liquid state in the corresponding plant’s growing conditions.

There are a number of structural features that influence the properties of fats and oils. Some of these structural features and their influence on melting temperature are listed in Figure 1.8. The directionality of the melting temperature with the structural feature is indicated by arrows or greater-than signs.

Figure 1.8 Structural features of TAGs that influence the melting temperature.

Based on this information, the fatty acid structural features influence the TAG physical properties and functionality. Even though it is not a one-to-one relationship, the melting temperature of an oil or fat is greatly influenced by the fatty acid structural features and its fatty acid composition. The glycerol-associated factors, such as its configuration and position of fatty acid attachment, which will be discussed later, had smaller influence. The structural features of various fatty acids and their melting temperatures are provided in Table 1.C.

Table 1.C

The Fatty Acids That Occur Commonly in the Food Fats and Oils, with Their Structural Features and Their Melting Temperatures

aThe fatty acid chain length is given with carbon number. The position, type, and number of double bonds are indicated for unsaturated fatty acids.

Functional Need for Solid Fat in Food Products

Many fat and oil applications do not require solid fat content. Most of these applications include deep frying, for which thermal and oxidative stabilities are more important. There are some exceptions to this, such as doughnut frying, for which the solid fat content is necessary to provide glaze and crispiness. For frying applications, good oxidative stability is a major requirement that can be met by using high- monounsaturated oils and/or low-linolenic oils. In other applications, such as baked goods, a certain amount of solid fat content (SFC) is crucial. The solid fats provide the pliability to dough and also give layer, spread, or discrete distribution of fat depending upon the product requirement. Some of the unique properties provided by solid fats in baked goods are flakiness, hardness, volume increase, layer separation, air entrapment while baking, dimensional structure, and freshness (Baldwin et al., 1963).

The oils/fats, proteins, and carbohydrates are the three major classes of building blocks required for living organisms. They are the most concentrated forms of energy (9 cal/g) and, because of this, most living organisms use them as energy storage media for critical functions such as survival during famine and seed germination. In various food applications, oils and fats provide a number of functional benefits. Besides imparting excellent organoleptic properties, they provide lubricity and decrease the interfacial tension of food particles, thereby making the food more palatable and easier to swallow. They supply essential fatty acids and oil-soluble vitamins that are essential for various biological functions.

The chemical composition of a mixture of TAG molecules present in a given vegetable oil is responsible for its physical state at ambient temperature. The oils containing saturated fatty acids in high concentration, like coconut and palm, can provide unique functionality and are more oxidatively stable. In general, the physical state of liquid (oil) or solid (fat) can possess some general and specific characteristics, as is shown in Table 1.D.

Table 1.D

General Functional Properties of Oils and Fats

There are two primary reasons to use fats instead of oils: oxidative stability and solid fat functionality. The solid fat functionality includes the melting curves, texture, crystal structure, and morphology. These properties are very important depending on the food application. In some frying applications, such as snacks, the oxidative stability is very important but the solid fat content is not. In baking applications, both of these properties are important. Lack of sufficient oxidative stability affects the shelf life of the food product. Oxidation is the cause of off-flavors and