Fat facts for cookies and crackersFat facts for cookies and crackers
The pendulum continues to swing surrounding dietary fats. The good, the bad and the ugly. More and more consumers desire fat-free products, but nothing beats a buttery shortbread cookie filled with natural wholesome fats.
August 1, 1996
Fat is good. Fat is bad. Fat is in. Fat is out. The swings of the pendulum particularly irk those who need to design products that ideally require a certain measure of fat. Most cookies and crackers fall into that category. Sure, there are some pretty good fat-free products out there, but nothing beats a buttery shortbread cookie in my book.
Regardless of the marketing pressure or personal preference, fats and oils make a significant impact on the quality of the finished product. So whether you are targeting full fat, reduced fat, cholesterol free, low fat, or no fat, it is necessary to know the functions and options available.
Fats and oils are technically lipids or triglycerides consisting of three fatty acids linked to a glycerol molecule. Commonly, the baking industry uses "fat" or "shortening" to refer to an ingredient that is solid at room temperature, and "oil" refers to a liquid. However, the term fat also generically encompasses all lipids. When fats are melted for a particular process, they are often called oils. Even more confusing, the U.S. Food and Drug Administration (FDA) considers some lipids, such as mono- and diglycerides and tocopherols, "fats" for purposes of labeling and caloric content.
"In a nutritional assay-required lipid extraction, emulsifiers will extract as fat," says Steve Mallory, project leader, bakery applications, Danisco Ingredients, New Century, KS.
Most food fats start out as RBD (refined/bleached/deodorized) oil. And this commodity was sufficient for bakery applications for years. Today, however, those who design cookies and crackers are not just interested in attributes such as stability, melt point, smoke point and flavor of fats and oils. To achieve improved functionality, they also need to focus on other factors, such as solid fat index, melting curves, and crystal structure. Altering a fat's functionality to meet these needs requires further processing. Fractionation, hydrogenation and/or interesterification are the processes most often used, but some specialty fats may require other modifications.
To increase stability and raise the melting point to accommodate most cookie and cracker applications, many RBD fats must undergo hydrogenation. Hydrogen atoms are added to the unsaturated bonds under high temperatures in the presence of a catalyst. Saturated, or single bonds, resist chemical reactions, including oxidation. As the chain length and the number of single bonds increase, so does the melt point. Hydrogenation may shift the location of the double bond, which slightly affects the melting point. It also promotes trans isomers, a form where the hydrogen atoms are positioned on opposite sides of the carbon-carbon bond. These configurations affect the melting point, too.
The melting profile of fats in cookies and crackers influences how well they incorporate air, as well as their rheology, mouthfeel, shelf life and other quality issues. Although most fats are described in terms of their melt "point," they actually have a melt "range" called the solid fat index (SFI). Within this range, as the temperature drops they have an increasing level of solid to liquid fat. Some fats have a broad range, while others have a fairly narrow range. The size of the range depends on a number of factors, including the degree of hydrogenation and the type of fat.
As the fat solidifies, it takes on one of three main crystal forms: alpha, beta prime, and beta. Each affects hardness, texture, mouthfeel and stability. The beta form is the most stable, but beta prime is generally preferred due to its smoothness and superior creaming properties. The factors that affect the formation of beta prime crystals include the amount of palmitic acid, the distribution and position of palmitic and stearic acids, the degree of hydrogenation, and the randomization of the fatty acids. Hydrogenation can increase beta formation, while randomization of the fatty acids promotes beta prime.
"You want something that will encourage the fat to go beta prime rather than beta, so that often drives the selection of source oils for an all-purpose type of shortening used for a creaming application," says Bob Wainwright, director of R&D, AC HUMKO, Columbus, OH. "You would incorporate some threshold amount of a substantially hydrogenated beta prime-tending fat like cottonseed or palm."
Many baking applications require a fat in semi-solid or plastic form. Fats are typically plasticized using a scraped-surface heat exchanger, or Votator, which promotes consistent crystallization.
When combining fats, especially in a filling or coating application, it's important to consider two issues: fat mobility and fat compatibility. When fat is in a liquid state, it travels seeking equilibrium as long as there is physical contact. So liquid fat can go from the filling to the cookie (or vice versa). If a filling has too high a liquid fat content, the surface of the cookie may become greasy.
Combining incompatible fats may result in softening, changes in the crystal structure, and/or fat bloom. A phenomenon known as the eutectic effect occurs.
"For an ingredient like a roll-in margarine, you can combine two very different fats - one lightly hydrogenated, one heavily hydrogenated - and it would give you a lower melting point than you would expect," says Wainwright. "At different temperatures, you would get different kinds of intersolubility interactions. As you introduce different source oils or different kinds of hydrogenation in the base stocks, the interactions that occur can be different. It's something you need to find out through experience. It's not something with a straightforward relationship so you can predict how it is going to behave."
Fat: Where's it at?
Fats and oils play a number of widely different roles in cookies and crackers. The main spheres of fat and oil use include dough fats for both cookies and crackers, filling fats, spray oils, and coating or confectionery fats.
Fat is added to cookie dough for its effect on both the finished product and the process. Fat acts as a lubricant. It keeps the dough from sticking to the feeding and forming equipment. It facilitates mixing by lubricating the other ingredients. And it helps the cookies release from the baking surface without sticking. Depending on the product, the fat content of a full-fat product ranges from 20% to 70%.
Fat helps control the texture of the finished product, its spread, and its appearance. In most cookies containing fat, a plastic (solid or semi-solid) shortening is first combined with the sugar in a creaming stage. This helps to entrap air, and contributes to the structure or grain of the finished product. It also influences the density of the dough. During creaming, the shortening coats the individual sugar particles.
"There are different criteria for someone with a bulk system versus plasticized cube shortening," says Dennis Strayer, technical service manager, Central Soya, Fort Wayne, IN. "For bulk, you would need to plasticize the shortening. You could use a range of different melting point oils, but it would depend on the plasticizing conditions and the temperature of the bakery. The critical point is to be able to coat the sugar without any clumping of the shortening or the sugar. If you don't do that, then the melted sugar will recrystallize into little chunks. You might not affect the texture with a liquid oil in something like a graham cracker because the levels are lower.
"Normally an all-purpose shortening for cookies has a 112° melt point," continues Strayer. "But you can use a range from about 95° to 115° depending on the practical limitations. For example, if there were a high shortening level, you might want to use a 102° shortening to reduce the waxy mouthfeel. Machinability, unique properties of the product - those are the things that can influence the correct melt point."
As a general rule, the more shortening, the more tender the mouthfeel of the finished product. A higher fat cookie will still be crispy without being hard. However, excess fat, particularly liquid, can result in a greasy, soggy cookie. The more fat in a cookie, the more it will spread.
Fat is particularly important in the texture of a low-moisture cookie. Most of these are baked down to 2% to 3% moisture, and without the shortening effect the result is rather hard. Certain production techniques or the addition of emulsifiers such as mono- and diglycerides can improve the texture.
"You can do a variety of different things with emulsifiers, ranging from adding shelf life to dispersing the fat in a system so that you get greater effectiveness," says Mallory. "They can modify the texture. In a full-fat cookie, we have also seen added emulsifiers eliminate fat bloom."
Emulsifiers affect the dough and the finished product differently depending on the system and the type of emulsifier used. The choice of emulsifier depends primarily on the effect required, in addition to the product characteristics such as moisture level.
"In a full-fat system, a distilled monoglyceride increases the tenderness of a cracker or cookie while keeping it crisp," says Mallory. "In a low-fat application you get the same general effect, but the emulsifier plays a much more important role. Emulsifiers, principally DATEM (diacetyl tartaric acid esters of mono- and diglycerides), will give you a fat-sparing effect. They break the fat up into very fine particles."
As with cookies, the purpose of fat in a cracker dough is lubrication and texture modification. Traditionally the level used has been lower than in cookies (less than 10%). Because of the level and the lack of aeration, fairly good results can occur with the use of liquid shortenings as well as solid ones.
Approximately two-thirds of a creme filling consists of fats. The other third is mainly sugar in a typical sweet filling. Savory versions also can be formulated using ingredients such as peanut butter and cheese powders. The key is to have sufficient fat to coat the dry material completely. The fat used must enhance eating quality, serve as an "adhesive" for the two halves of the sandwich, and function properly in the sandwiching operation. All of these depend on the solid fat index.
Either liquid or plastic fat can be used for the creme depending on the result required. The creme must remain plastic during the sandwiching operation. If the percent of solid fat is too high, the creme becomes brittle and dry and it will not stick to the base cake. If the percent of solid fat is too low, the creme will be too soft, causing a number of problems - for example, the creme will smear, and it will not hold the base cakes together.
"At cool temperatures, you want a fat that will be fairly brittle so it holds the two halves together," says Strayer. "But you don't want it so brittle that they won't pull apart. You need to look at both mouthfeel and performance."
From an eating quality perspective, nearly all of the fat must be liquid over 92°F or the filling will taste waxy rather than creamy. A fairly steep SFI also enhances mouthfeel by giving a cleaner, cooler melt. For both mouthfeel and processing, the standard SFI for filling fats is similar to that exhibited for 92° coconut oil.
"You have a good, clean-eating filling fat if the melt point is in the 90s," says Frank Kincs, associate director of research and development, Bunge Foods, Bradley, IL. "I doubt that you would be able to detect a difference between one that melts at 98°F versus 92°F. A 102° fat will work, if the solids drop off quickly. But much above that and it starts to come across as waxy."
Says Richard Thesing, director of product development and technical support, AC HUMKO, Memphis, TN: "There are fractionation technologies for domestic fats that will mimic the mouthfeel and melt profile of coconut. Certain ones are primarily used in Europe. In the United States, some manufacturers use non-solvent fractionation technologies."
Some cremes are aerated. The fat must have a fairly high level of solid fat during the mixing and processing step to incorporate air and maintain it during processing. Liquid fat does not retain air. Fats for cremes also require a melt point and profile that give a rapid meltaway in the mouth. The most effective way to aerate filling cremes is by running them through a continuous scraped-surface heat exchanger prior to sandwiching. Aeration creates a softer creme, and that may affect the process. Because an aerated cream has increased exposure to air, the fat must have a high degree of oxidative stability.
A coating of oil after baking improves the appearance of crackers. It also reduces the pasty mouthfeel generated by a product that consists mainly of flour. The level of spray oil depends on the equipment capabilities and the geometry of the cracker, as well as the desired organoleptic target. Products with a higher surface-to-volume ratio tend to require a higher level of spray oil.
SFI plays a role in the fat selection, but with less importance than for a filling fat. The oil must be liquid during the spray operation, which isn't too difficult since this takes place at elevated temperatures.
"If the melt point is too high, it could plug up your lines," says Strayer. "The fat might also solidify too quickly on the surface, and the cracker would have a greasy outer coating or stick to the belt."
Stability is important in spray oils. Because the oils are held and used at elevated temperatures, any reactions - including oxidative rancidity - occur more quickly. Spraying increases the exposure to air. The cracker will have a fairly high level of oil on the surface of the finished product, and this also increases the exposure to air.
Traditionally coconut oil was used as the preferred spray oil, but health concerns have changed this.
"The domestics, soybean and cottonseed, took the place of the coconut oil," says Lynn Lawrence, product development scientist, AC HUMKO, Memphis, TN. "In some cases there were some tradeoffs, but in others it didn't make any difference whether it was a domestic or tropical oil. Coconut has a unique melting characteristic and it quickly goes from a solid to a liquid, giving it very good eating qualities. It's very stable, but the downside is that it's mostly saturated fat. You need to look at a domestic fat with similar melting properties."
Says Kincs: "If you shift away from coconut, you can lose a couple of things if you're not careful. Coconut is very bland. It has higher solids, so it offers a little dryness on the cracker. It has excellent stability because of the level of saturates. Some of the high-stability products, particularly soy oil, have been used. You would want to use something with a high IV (Iodine Value ) that still has a low melt point."
Coating fats for cookies closely resemble those for confectionery, especially those used for chocolate or chocolate-like products. The model for coating fats in terms of the SFI is generally cocoa butter - that is, a steep curve with a melt temperature below 98°F. Cocoa butter is used in some high-end products and for "real" chocolate chips, but in many cases coatings and chips contain fats other than cocoa butter.
"When you are looking for replacements for the tropical oils, this is an area that fractionated soybean and cottonseed oils have done quite well," says Lawrence. "The fat must set up quickly and it must melt quickly in the mouth. In addition, you probably need to consider hot- and cold-weather formulas. But still, if you are shipping the product without temperature-controlled trucks, nothing will help."
Traditionally these were known as "hard butters," but the fats and oils industry now uses a number of different terms to classify the types of fats used in coating and confectionery applications:
Cocoa butter alternatives (CBA) are fats designed to replace some or all of the cocoa butter.
Cocoa butter equivalent and extender (CBE) describes two different categories. The equivalents are completely compatible with cocoa butter and do not change the melting, processing and rheological properties of the cocoa butter. The extenders can only be combined with cocoa butter to a limited extent or they will change the properties.
Cocoa butter replacer (CBR) has been engineered to replace or extend cocoa butter, and these are often labeled as "partial" or "complete" replacer depending on the level of compatibility. Often this term refers to only non-lauric fats, or those triglycerides that are low in lauric acid.
Cocoa butter substitute (CBS) refers to a fat engineered to replace or extend cocoa butter. Some divide CBS into lauric and non-lauric classifications and subdivide the categories into hydrogenated, fractionated and/or interesterified fats. Others use the term CBS only for lauric fats.
Again, because of fat incompatibility issues, it is extremely important to know what kinds of fat are being combined in the cookie and coating or chip.
Healthy, wealthy and natural
Technically, the characteristics of a particular fat drive the choice in a cookie or cracker. Practically, other issues often restrict the type used: cost and market-driven issues including natural ingredients and the relationship of fats and oils to health.
Most major ingredients in crackers and cookies - flour, sugar and minimally processed fats - are relatively inexpensive. The least expensive form of fat is RBD. Most cookie and cracker applications require processed fats, increasing the cost. The more processing required, the more the cost rises, particularly in some of the more sophisticated processes that are required to create some of the specialty fats.
Marketing considerations also limit the options. Three recurring themes appear to drive sales: healthy, natural, and fewer calories.
A designer can reduce calories by cutting the fat level. Alone, this significantly affects the product quality, but some have found that adding emulsifiers can help bring the product closer to the full-fat original.
The second option is to replace the fat with an ingredient or mixture of ingredients that provides fewer than 9 Cal./gram. With low-moisture cookies and crackers, that has proved difficult because most fat-reduction systems use water. However, the development of reduced-calorie lipids holds some promise for the future.
Natural is in the eye of the beholder. Most would agree that an expressed RBD oil qualifies as natural. However, the fat itself is usually not the issue unless the product is targeted toward the natural foods market. The general populace is more concerned with "chemical preservatives." These include BHA (butylated hydroxyanisole), BHT (butylated hydroxytoluene), and TBHQ (tertiary butylhydroquinone). The market offers some natural alternatives. Lecithin acts as a water scavenger to prevent lipolytic rancidity. Chelating agents such as citric acid inhibit metal-catalyzed oxidation. Tocopherols act as antioxidants.
"People who want natural labels will use the tocopherols," says Lawrence. "But it's pretty clear that they are not as effective as BHT, BHA and TBHQ in a spray oil."
While cost and natural ingredients may be important selection criteria, the one that gets the most press (and drives most product designers crazy) is the relationship of fats to health.
At the rate at which new studies are publicized and their validity is accepted, all of this information may very well be out of date by the time it is published. Still, it's safe to assume that once a food ingredient receives a certain notoriety, the consuming public will think twice about eating it.
The excess consumption of fat has been implicated in a number of ills, including cancer and arteriosclerosis. Those links are probably more complex than fat intake alone, and they very well may include factors such as total calorie consumption, exercise, and other dietary factors. Cholesterol also turns off most health-conscious consumers, although recent evidence indicates that its consumption may not be as lethal to the general populace as it was once thought. Still, most animal fats were removed from cookies and crackers in the 1980s, and there has not been any big rush to put them back into these products.
The next health issue that cropped up concerning fats involved saturated fats. Consumption of high levels of saturated fatty acids was implicated in increased cholesterol levels, particularly the "bad" low-density lipoprotein (LDL) cholesterol. Most experts now believe that this is not a function of all saturates and that only certain fatty acids are hypercholesterolemic. However, that type of information is difficult to disseminate to the general public, and people still look negatively on the terms "saturated fats" and "tropical oils." Tropical oils, particularly palm kernel and coconut oil, naturally contain a high percentage of saturated fatty acids.
Because the degree of saturation influences a number of technical issues, this creates a dilemma. Unsaturated fats have decreased stability and low melting points, so they would not work well in most cookie and cracker applications. Part of the answer has been to hydrogenate in order to increase the saturation, but not to the level seen in coconut and palm kernel oils. That process gave us trans isomers. Some studies indicate that trans isomers elevate LDL cholesterol and decrease HDL (high-density lipoproteins) cholesterol, the "good" cholesterol.
Going to the source
Food fats and oils come from a number of different sources, either animal or vegetable. They can come from one source or consist of a blend that creates a functional or cost benefit. Most of them find application in cookies and crackers.
Fats from animals include tallow or oleo (beef fat), lard (pork fat), menhaden (fish oil), and butter. Prior to the cholesterol controversy, crackers frequently contained lard and some cookies contained tallow. They both contribute a characteristic flavor, especially in lightly flavored products. Lard also gives a cracker a flaky texture. Most commercial lard has been processed - hydrolyzed and/or interesterified - to broaden the SFI, firm up the texture at typical processing temperatures, and create a smaller crystal size. Oleo is tallow that has had the higher melting point fractions removed to yield a softer product.
Butter has traditionally been used for its flavor contribution, but it usually is not the only source of fat in a product due to the expense. Butterfat contains a significant level of short-chain fatty acids which help form the typical flavor associated with butter. Butter is actually a water-in-oil emulsion that contains 80% butterfat, 14% water soluble milk solids, and often salt. These components and their effects on the finished product must be considered during formulation.
The biggest problem with animals fats over the last decade has been the cholesterol content. For those who want the taste and textural benefits provided by the animal fats, Bunge Foods Group is now marketing a product called Appetize(r). The line is made from a blend of cholesterol-removed, non-hydrogenated animal fats and vegetable oil. The product was developed jointly by researchers at Brandeis University, Waltham, MA, and Source Technology, Minneapolis. A patented steam-stripping process removes the cholesterol.
Vegetable oils used in baking come from a number of sources: canola, cocoa butter (in chocolate), coconut, corn, cottonseed, palm, palm kernel, peanut, safflower, soybean and sunflower. In many cases the primary considerations are price and availability, so soybean or a blend based on soybean typically has an edge. When functionality and labeling become an issue, the oil used becomes much less of a commodity.
Despite their notoriety, palm oil and the other tropical oils provide a number of positive functional attributes. They can be used as a source for solids to avoid hydrogenation of liquid oils. Palm oil promotes beta prime crystallization. The high palmitic content increases the aeration of fat and sugar mixes. The absence of linolenic acid prevents flavor reversion, or the development of characteristic, often undesirable flavor notes that develop in most oils with time.
Plant genetics can yield non-hydrogenated, non trans oils with enhanced stability and performance. First canola was altered through hybridization to reduce substantially the erucic acid content. In the search for alternatives to hydrogenation, companies began working with other oilseeds to increase the oleic acid content. A high monounsaturate content is linked to good health and imparts a relatively high amount of stability compared to polyunsaturates, offering a fairly good compromise between health and stability. High-oleic sunflower oils currently have 80% monounsaturates as opposed to 20% in ordinary sunflower oil. Soybeans have been bred to yield a low-linolenic oil, which increases the oleic content by 7%. High oleic canola is also available. The oleic content reaches levels over 80% in a lightly hydrogenated product and 70% in a non-hydrogenated version. Research and development in this area continues, so new and improved products are expected.
"These products have increased stability when compared to the standard domestic fats, but are not as stable as coconut oil," says Lawrence. "Most of the new spray oils tend to come from the genetically engineered oils."
Says Thesing: "Cost can be a factor with these, but it depends on the tradeoffs you are willing to make. They can give you increased shelf life without the hydrogenation and reduce some of the operational headaches. As a class of compounds, they have high AOMs, or as the industry is converting to, OSI, the oxidative stability measurement. They can last much longer than oils that are not genetically engineered. Plus, as they become more widely used, the cost will come down."
Interesterification can not only create compounds of specific functionality which are not found under normal conditions, it also can cut calories. The results are commonly referred to as structured lipids. These include salatrim (initially discovered by Nabisco Food Group, then developed and marketed by Cultor Food Science) and Procter & Gamble's Caprenin. Because certain fatty acids have intrinsically fewer than 9 Cal./gram and their location on the triglyceride can lead to lower absorption by the human body, a fat molecule can be designed to deliver fewer than 9 Cal./gram.
In addition to caprylic and capric acid, the Caprenin molecule contains behenic acid (22:0), a fatty acid that is only partially absorbed by the body. Salatrim, a line of structured lipids, consists of primarily stearic acid (18:0), with either acetic (2:0), propionic (3:0), or butyric (4:0) fatty acid. Both of these lipids contribute 5 Cal./gram.
For practical purposes the industry is considering salatrim GRAS. Although the petition has been accepted for filing, the FDA has not officially affirmed it. There are no legal restrictions on its use, except for self-imposed restrictions on infant formula.
"Benefat™ is a family of salatrim-based products, so there will be products with various attributes targeted for a specific market," says Susan Coleman, Cultor's Benefat technical services manager. "Benefat #1 targeted cocoa butter and confectionery fats, so it has a melt point and melting profile similar to that of cocoa butter. It can be used in chips, chunks, fillings or coatings. As far as a baking shortening, that's one area we plan to explore, although we currently aren't in the position to offer a commercial product."
There are hundreds of different fats - some old, some new, and some yet to come. In the selection process, taking into consideration all of these issues - form, functionality, cost, stability and health - narrows the choices. Nevertheless, the selection process still offers much to keep the product designer busy.
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