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May 1, 1995
By: Lynn A. Kuntz
About 10 years ago many American food companies were working on remarkably similar projects. No, it wasn't the start of the "Cookie Wars." It was more like the "War Between the Fats." The enemy, according to a number of reports and several consumer interest groups, included cholesterol and animal fats, as well as the dreaded "tropical fats."
Although there was, and still is, no legal or technical definition for the term, the category included palm, coconut and palm kernel oil. Consequently, many food product designers faced the task of finding replacements for these oils.
Good fat, bad fat?
Why did these fats become blacklisted? At the time, studies indicated that consuming high levels of saturated fatty acids promoted coronary disease. Coconut oil and palm kernel oil were obvious targets-with saturate levels over 90% and 80%, respectively. Adding palm oil to the list of "bad fats," with its saturate level averaging 51%, was a slightly different proposition. Although for a vegetable oil this level is relatively high, most industry sources suggest that the recommendation not to use it was politically motivated as a method to increase the demand for domestically produced oils.
"With unhydrogenated palm frying oil, the saturates are about 50%," notes Al Rogers, technical services, C&T Quincy, Charlotte, NC. "But by the time you take soy and hydrogenate it to make a reasonably good frying fat, you're up around 25% saturates. You're also going to increase the bans fatty acids during the process."
That's one of the major reasons the food industry is taking a second look at the tropical oils. Unhydrogenated tropicals or fractions of tropicals can functionally replace the hydrogenated domestics in many food applications. The latest focus is on the effect of bans fatty acid isomers generated during hydrogenation. They are believed to raise a person's total cholesterol level and lower the HDL ("good") cholesterol.
While initially all saturated fatty acids from C12 through C18, inclusive, were believed to be hypercholesterolemic (causing increases in the cholesterol level), that belief has changed. It is widely held now that stearic acid has a neutral effect, and research indicates that lauric and especially palmitic may actually decrease the LDL ("bad") cholesterol. Also, palm oil contains significant levels of vitamin E-in the form of tocotrienols-and beta carotene, both of which are antioxidants associated with the reduction of arteriosclerosis and certain forms of cancer.
"The latest thinking is that myristic acid, the 14-carbon saturated fatty acid is the only one that is really hypercholesterolemic," claims Mary Enig, Ph.D., director, nutritional sciences division, Enig Associates, Silver Spring, MD. "But if you look at some of the studies, what it appears to raise is HDL. However, even if myristic did cause a problem, when you add up all of the sources of fat in the diet, you really don't consume large amounts (of myristic acid)."
Says Ed Finchum, group leader, confectionery and specialty fat R&D, ABITEC Corp., Columbus, OH: "Most saturated fat in the diet, about 70% to 75%, comes from foods like meat, eggs, fish, milk and cheese. "The total fat in the diet from coconut, palm kernel and palm oils combined has been reported to be less than 4% in this country."
Focus on the function
Ingredient selection, including fats and oils, depends on a number of factors. Consumer acceptance, cost and functionality all influence formulation. While it is obvious that health concerns affect the marketability of a product, a product designer has to weigh those issues with the end result. The compositions of the tropical fats provide unique properties that can be difficult to replace with other oil sources.
Tropical oils fall into two categories: lauric and non-lauric fats. Both coconut and palm kernel oils are lauric fats because they contain relatively high levels of lauric acid, the C12:0 fatty acid (see chart). Palm oil, a non-lauric fat, has a composition similar to domestic fats such as soybean and cottonseed, but without the high levels of polyunsaturates, especially linoleic (18:2) and linolenic (20:2). In fact, from a fatty acid standpoint, the composition of palm oil is similar to that of beef tallow, with high levels of palmitic acid (16:0) rather than stearic acid (18:0).
The composition of a fat determines its characteristics. In general, the longer the chain, the higher the melting point. The more double bonds, the lower the melting point. That is why the domestic oils have relatively low melt points and are liquid at room temperature. Hydrogenation raises the melt point of a fat. Double bonds are much more reactive than single ones, so the more unsaturation, the less stable a fat is to oxidative rancidity and other deleterious reactions.
"If you take soybean down to the iodine value-get rid of the double bonds which react with moisture and oxygen-to the level seen in coconut oil, it would be such a hard mass to work with that it would be absolutely terrible," says Carl Heckel, technical services manager, Aarhus, Inc., Port Newark, NJ. "If you took soybean oil down to a nine or a 10 IV, the melting point probably would be in the area of 135° to 140°F. It would be like wax, and you would taste that. But you can't practically do that with domestics to get that level of oxidative stability. As a result, you've got a much higher IV, a lot more double bonds for oxidation to be taking place."
Melt characteristics influence a fat's utility. The traditional way in the United States to measure this was by the Solid Fat Index (SFI). This method was not very accurate and repeatability was poor, so the American Society of Oil Chemists proposed changing to a method using NMR (nuclear magnetic resonance) to give the actual solid fat content (SFC) at the measured temperatures. This is usually done at 70°, 80°, 92°, and 100°F, depending on the fat application.
The composition also affects the melt profile, or the steepness of the melting curve. The type and level of fatty acids, as well as their position on the glycerin backbone, determine how quickly a fat will go from a solid to liquid phase.
"With the laurics, their quick melt-down is partly a function of the narrow melting range of their component fatty acids," says Finchum. "They're all fairly similar. That tends to give the product a steep meltdown."
For example, coconut oil contains mainly lauric, myristic and palmitic acids. These melt at 11°, 129° and 145°F, respectively. The difference between the highest and lowest temperature is only 34°F. The major fatty acids of domestic oils are generally linoleic, oleic, palmitic and stearic acids, which melt at 19°, 61°, 145° and 158°F, respectively. This gives a difference of 139°F between the lowest and highest melting of the group. Therefore, domestic oils such as soybean and cottonseed have more of a plastic nature and they don't go from solids into liquids very rapidly.
The positioning of the fatty acids on the glycerin backbone significantly affects crystallization and melting properties. Cocoa butter consists predominantly of palmitic, oleic and stearic acids, but most of the triglycerides in cocoa butter are symmetrical, with the unsaturate in the center position. So, these triglycerides pack together very well during crystallization and exhibit a rather narrow melting range.
In many applications, it is advantageous to have a fat with maximum solids at room temperature so that the finished product has a stable structure. But to obtain maximum eating quality and flavor, the fat must melt at body temperature.
"The unique thing about coconut and palm kernel oil is that the predominant fatty acid is lauric, a 12-carbon fatty acid," notes William Dyer, manager, applications and technical services, Van den Bergh Foods Co., Lisle, IL. "The fatty acids primarily dictate the performance of the fats. The longer chains have higher melting points. Since there are so many kinds of fatty acids and each triglyceride has any combination of these, you get a mixture of melting fractions."
With soybean oil the predominant fatty acids are 18 carbon. Palm kernel oil is rich in lauric fatty acids, and this gives it a very steep melting profile. If you were to plot the percent solids found at various temperatures in laurics, you would get a steep profile. At room temperature you would have maximum solids. As the temperature goes up, the amount of fat in a crystalline phase decreases and the amount of fat in the liquid phase increases. Ideally, you would want maximum solids at room temperature, maximum solids at 80°F, which is an indication of heat resistance and durability during distribution. You would want minimum solids as the temperature approaches human body temperature, where the flavor is released.
"Because of the types of fatty acids found in domestic oils, it's very difficult to get the steepness," Dyer continues. "You can overcome that to a greater extent by controlling the fractionation process. This helps to weed out fractions of fats without the required characteristics."
Fractionation works by holding hydrogenated oils at certain temperatures that produce a mixture of liquid and solid. Removing the liquid makes the product hard without further hydrogenation. The high melting portion also can be separated out to leave the mid-fraction. Making this mid-fraction is the fundamental goal of fractionation.
"By controlling the process we maximize the yield of the midfraction and get the steepness," says Dyer. "With soybean and cottonseed, we first have to selectively hydrogenate to convert 18:3 and 18:2 linolenic and linoleic acid. Then we go through the fractionation process to remove the high melting and low melting fractions and produce a much steeper profile."
Looking at laurics
The unique properties of lauric oils make them useful in several applications, primarily confectionery, vegetable-dairy products, and as coating fats for products such as nuts, crackers, ready-to-eat cereals and dried fruit. Because of lauric oils' melting profile, they remain solid at room temperature, eliminating sticking and maintaining structure for the other ingredients under normal handling. They melt at body temperature, giving good mouthfeel and flavor release. This also means they are liquid at moderate process temperatures, which can provide lubricity or application and handling advantages.
Coconut oil is used in nut roasting because of its oxidative stability. When melted, coconut oil has a low viscosity which permits better draining. Coconut oil is not a good choice for normal frying applications. It contains high levels of short-chain fatty acid triglycerides that are very volatile, and it has a relatively low smoke point.
Coconut oil makes a good spray oil for crackers. Spray oil on crackers provides a more desirable, glossy appearance and improves eating characteristics. Using coconut oil eliminates waxiness and reduces fat migration at ambient temperatures.
"Coconut oil can give you benefits just from a processing standpoint," relates Ed Wilson, from Aarhus' technical services. "At a recent Biscuit and Cracker Manufacturers Association seminar, some manufacturers were discussing the situation with the spray oils they began using after switching from coconut oil-how the new types were gumming up their machinery.
That kind of problem gets worse when you add different kinds of flavoring and spices and things of that nature. They are having major problems with the hydrogenated soybean/cottonseed blend. It is almost acting like a glue, and it's driving the people in the plant crazy."
Laurics are commonly used to replace butterfat in dairy products such as whipped toppings and nondairy creamers. These require a steep melting curve to mimic the action of the butterfat rather than the properties of the fat itself. Additionally, the fats must help maintain the structure of the product during storage and usage conditions.
In some dairy applications the fat level is relatively low, 5% to 10%- not like products such as compound coatings, which are roughly one third fat. In these cases fat does not often dominate the physical characteristics, so a chemical match for butterfat is not usually a priority. In high-fat applications, such as whipped toppings and margarine, the fat plays a critical role.
"Oftentimes when you use a vegetable oil in nondairy applications, the physical properties of that oil could be quite different from the milkfat in the standard product," says ABITEC's Finchum. "It sounds odd, but although the vegetable oil is quite different, it gives a similar product in the end. That's because of the differences in the way the fats crystallize, the speed of crystallization, the size of crystals, and the different ratios of solid to liquid. That's very important in a veg-dairy application because the liquid component can tend to de-aerate things. So sometimes you might want a little higher level of solid fat. You would actually want a harder product than the butterfat in many nondairy applications."
Fat stability is important in most of these applications. Because saturation increases the stability of an oil, the more saturation-whether from hydrogenation or naturally occurring-the better the resistance to rancidity. This results in longer shelf life for the finished product. Also, for processes that use the oil at an elevated temperature, it means fewer breakdown problems like the one described with the cracker spray oil. And, of course, the more pro-oxidants such as salt included in the other ingredients, the more pronounced the effect.
"When you walk into a movie theater where they are popping corn with canola oil, the aroma is quite different from the one you get with coconut oil," says Thomas Horsman, national sales manager for Aarhus. "Coconut oil doesn't have that reversion property where it wants to go back to its natural flavor."
On the other hand, because some of the fatty acids in coconut and palm kernel oil have short or medium chain lengths, hydrolysis tends to produce soapy off-flavors. These types of fatty acids can be more readily tasted at lower concentrations than the longer chain lengths which are found at higher levels in soybean and cottonseed oils.
If laurics have one area where they are indispensable, it is in the confectionery industry. While there are other uses, such as coconut oil in caramels, most applications involve using laurics as fats that mimic cocoa butter. Usually they serve as the fat in compound coatings, alternatives to chocolate, but they are also used extensively in creme centers and fillings for cookies as well as candy.
Although some alternatives to laurics have been found, most of them do not mimic the characteristics of cocoa butter as well. Also, because extensive processing (including hydrogenation and fractionation, and even interesterification) are needed, they tend to cost more than the laurics with comparable characteristics. The greater the number of double bonds, the lower the melting point-even with equivalent chain lengths. Hydrogenation converts three double bonds to two, and two to one.
"If you go from one double bond to a saturated fatty acid, you raise the melt point to about 158°F," explains Dyer. "You've created a stearine. So the object is to partially hydrogenate domestic oils. Without the hydrogenation step, it is difficult to obtain an intermediate product to fractionate."
Tropical oils can be fractionated without hydrogenation because enough solids occur naturally. Refined, bleached palm kernel oil can be dry-fractionated (commonly called "winterization" in the United States) by holding the oil without any additives at certain temperatures and pressing the liquid oil out.
"You get a very hard product at room temperature, harder than cocoa butter or domestic coating fats," says Dyer. "But as you raise the temperature to 92°F, it melts very quickly. That's the unique feature of the lauric fats."
Fractionated lauric fats exhibit similar physical properties to those of cocoa butter, but they also have several advantages, including cost and processing requirements. They can produce the firmness, snap and melting characteristics typically imparted by cocoa butter. They crystallize rapidly and do not require a tempering step. You can alter the melting point of the fat for summer and winter without changing the formula or the process, except for raising the temperature.
"With pure chocolate, you have to be very careful of the temperatures-how fast you cool, the temperature at which it cools and so on -to keep it from blooming, melting or turning grainy," warns Rogers. "Laurics are not as sensitive. From a processing standpoint, they are generally easier to use. They work well for frozen applications, especially on ice cream bars, where pure chocolate is extremely hard. Usually you want a 76° coconut oil."
Cocoa butter is very sensitive to other fats, creating what is called a eutectic effect. If two dissimilar fats are melted, blended together and recrystallized, the mixture will melt at a lower temperature than either of the two types of fat. Incompatibility can cause bloom and, in the early stages, a loss of surface gloss. At the extreme, the product will become tacky and soft. Because chocolate has a standard of identity, increasing the solids in the cocoa butter is not an option. With compound coating you can adjust the solid fraction using hydrogenation and fractionation techniques.
Since lauric fats are chemically different from cocoa butter, there may sometimes be compatibility problems when cocoa butter is present. For instance, compound coatings made with palm kernel oil must use low-fat cocoa powder to minimize the cocoa butter level in the finished product.
"Someone who is not familiar with fats may say they can't use a lauric coating on a baked product because the base cake is made from a non-lauric fat," states Wilson. "That's not true. Most oils are compatible, but compatibility depends on your applications. Certain oils give incompatibility effects when mixed, and that can work for you or against you."
For example, if you mix two incompatible fats to make a meltaway center or a truffle center, you might get the perfect eutectic effect that you need for the product. Combining two oils with higher melt points gives you the right melt point.
There are a couple reasons you might not want to use a single fat with a lower melt point. If you use coconut oil with a melt point of 76°F, for example, the solids profile below that temperature is almost nothing. There will always be a significant liquid portion making an unstable environment in that particular piece. By mixing two different oils or parts of the same oils together to get a product with an equivalent melting point, you will still have the right amount of solids to keep the product from being liquid at the lower temperature.
Laurics do not always cause compatibility problems when blended with cocoa butter; it depends on the product. Confectionery fats, for example, are broken down into three categories: CBEs (cocoa butter equivalents or extenders), CBSs (cocoa butter substitutes), and CBRs (cocoa butter replacers). Confectionery fats are called cocoa butter substitutes if they are lauric, and cocoa butter replacers if they are non-lauric. Neither of these categories requires tempering. Both can be formulated to give different levels of hardness at ambient and mouth temperatures. Altering the source fats with hydrogenation, interesterification and fractionation yields different kinds of melting profiles from the laurics and the non-laurics.
"CBEs are symmetrical triglycerides with C16 and C18 chain lengths that really are compatible with cocoa butter," explains Finchum. "These are some of the triglycerides that are actually in cocoa butter. They are derived from things such as fractions of palm oil, illipe butter and shea fat put together in different ratios. For practical purposes, chemically they are very similar to cocoa butter. You can use them to extend cocoa butter, and you also have to temper them just like cocoa butter."
Unlike the laurics, palm oil is generally used in applications that also commonly use domestic sources, such as frying or shortening and margarine applications. Palm oil contains high levels of palmitic acid. It produces unique and very stable crystals, resulting in more stability during shelf life. This crystal structure may improve eating quality.
In this country, most of these types of products have switched to hydrogenated versions of soybean, cottonseed or blends due to the negative publicity about tropical oils. But, as with the laurics, in some cases there might have been compromises in functionality, especially if the cost of hydrogenation was factored in.
"The softer fractions of fractionated palm oil are used as a frying fat," says Rogers. "This gives superior functionality-good stability, good fry life, and good flavor characteristics. Fractionated palm oil was starting to make some inroads on some of the domestic oils used in this country before the tropical scare."
Fractionation is commonly used to separate fractions with specific functionality. Because palm oil naturally contains a fairly high level of the higher melting saturates compared to most domestics, hydrogenation is not necessary to create a wide range of functional ingredients. This allows a spreadable margarine to be made without hydrogenation, something that is widely done in Europe and is also showing up in Canada.
In confectionery applications, palm oil offers many benefits. The saturate level is similar to cocoa butter. Fractionation can create a product similar to cocoa butter by duplicating the triglycerides found in cocoa butter. It is compatible with cocoa butter and requires tempering.
"You can make some unique products with palm oil," says Dyer. "Palmitic acid is one of the most useful fatty acids in vegetable oil. Next to cocoa butter, palm oil is very rich in palmitic acid. This gives unique and very stable crystals and offers more stability during shelf life. It also gives a better eating quality than cocoa butter."
Crystal formation greatly affects the texture and shelf life of a finished product. The goal in most cases is to produce smaller crystals that give a smooth mouthfeel and that do not revert to the larger, less stable forms. Palm and cottonseed oils tend to promote the formation of beta prime crystals, a small, stable form. That is one reason they are used in shortening and confectionery fats. While beta crystals are stable, they are also large enough to impart a grainy texture. When a fat or product is aerated, the smaller beta prime crystals form a more stable matrix to keep the air entrapped.
"All fats eventually go to the beta configuration," says Finchum. "Because of its unique triglyceride profile, cocoa butter is not very stable in any form except beta. Other fats such as palm kernel and soybean/ cottonseed mixtures can be essentially locked into the beta prime form. Their transition from beta prime to beta is so slow that for practical purposes they are beta prime stable."
"Since hydrogenation has become a sensitive issue, if someone wants a product free of bans fatty acids, they have to bypass the hydrogenation process," Dyer points out. "The only two ways are to use fractionated palm kernel or palm oil. You could combine them with lower melting fats to raise the melt point. It would even be feasible to make a coating fat using palm and soy, or palm and cotton, or palm and soy/ cottonseed. We've been telling the industry if they want to make a claim of nonhydrogenation, no bans fatty acids, then the best approach is to use palm oil."
With the implementation of the NLEA (Nutritional Labeling and Education Act) the term tropical fat became extinct on food products. Although the level of saturates is listed, hydrogenation can bring the level up in domestic fats-especially when compared with palm oil. This also, of course, creates bans fatty acids, which makes increased use of tropicals an increasingly attractive option.
"One thing we're seeing is that there are people who don't know or care about the stigma and are just trying to make the best product and get the best flavor and easier processing," observes Wilson. "We're getting more and more inquiries about these oils, although we haven't seen any change in the usage figures yet."
Tropical fats only seem to be an issue in the United States. Their use in rest of the world doesn't seem to generate the same negative reaction.
"I'm Danish and I came over here two years ago, working out of Denmark for the same company," notes Horsman. "I had never heard of a tropical oil issue anywhere else in the world, so it was a big surprise when I got here."
Adds Heckel: "It's going to take a concerted effort by all aspects of the food industry to get rid of some of these misconceptions that have been placed in the public eye. When that starts to take hold, there will be some much improved products out there. It's going to take individual consumers expressing displeasure with some of the compromise products out there to overcome the nutritional activists."
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