February 14, 2012
By Kimberly J. Decker, Contributing Editor
Several years into our post-trans era, its worth asking: Hows that working out for us? Some, it turns out, are doing better than others, as the challenge of scrubbing trans fats from formulations has proven particularly difficult for certain sectors of the industry.
Consider what those in the bakery have had to contend with. Fat plays crucial and complex roles in everything from crackers to crullers, and the unique properties of partially hydrogenated oils and shorteningslargely responsible for the trans fats were trying to removerevolutionized baking when they came onto the scene in the last century. Thus, we shouldnt be surprised to face a minor counterrevolution now that were making do without them.
But the continued presence of cookies and snack cakes on the shelves speaks volumes to the effort and ingenuity of fat and oil processors, whove done yeomans work not only in identifying the hurdles to successful trans-free baking, but in developing alternatives that can clear them.
What fat does
No attempt at replacing trans fats could proceed without first taking stock of all the appreciated functions fat of any kind performs in baked goods. As David Hughes, project manager, bakery applications, Ventura Foods, Brea, CA, says, If flour is the backbone of baked goods, then shortening is their lifeblood."
Just the word shortening" is telling. The classic definition is that a fata shorteningshortens the dough, thus imparting the tenderizing effect" that makes baked products so appealing," says Tom Tiffany, senior technical manager, ADM, Decatur, IL.
Fat also lends lubricity, letting a cake, cracker or cookie clear the mouth more easily. And, in cakes, fat is the nucleus of the emulsion between the water, air and respective emulsifiers," explains Hughes. "The lubricity we enjoy is at work in allowing the starch granules to slip and meet the intended cake volume, driven by leavening agents and steam."
From a flavor standpoint, anyone whos compared a doughnut fried in soybean oil to one fried in palm oil can attest to fats significant contribution. But fats also aid the release of other flavors and influence the generation of flavors that wouldnt arise but for the fats presence. Again, consider the doughnut: Deep-fried products like doughnuts develop some of their flavors from the fat," says John Neddersen, senior application scientist, fats & oils, emulsifiers, DuPont Nutrition & Health, New Century, KS. "This is mainly from reaction products that form when the triglycerides and fatty acids react with sugars and proteins."
As for fats structural contributions, Susan Knowlton, senior research manager, Pioneer Hi-Bred International, a DuPont business, Johnston, IA, offers laminated pastry by way of example. The shortening is making layers of the solid-fat product with the flour in the crust or dough," she says.
By contrast, shortenings solids in icings and frostings trap and stabilize air in a creamy foam. The solid fat component also gives the icing flexibility to prevent cracking," Nedderson says.
Solid and stable
No matter fats role, theres one particular property it has to lock in to ensure bakery success. You need something thats solid at room temperature," says Lynn Morehart, technical services manager, Cargill Oils & Shortenings, Minneapolis. "Thats the key to give you the right structure, the right creaming capabilities, the right mouthfeel."
How solid is solid? Its not always a clear-cut distinction. Even solid fats are not entirely solid," Neddersen says. They consist of two phases: a solid portion, which we refer to as solid fat, and a liquid portion that we refer to as liquid or oil. The liquid oil is trapped in the crystal matrix of the solid fat. The amount of solid fat is measured by the solid fat content, or SFC."
Whats important for the baker is that his chosen fat achieve a balance between the solid and liquid components. Too much solid content or too high a melting point and the product will not have the proper melting characteristics and will have an undesirable mouthfeelit will taste waxy," Neddersen says. On the flip side, too much liquid and the product can oil out or taste oily. In an icing, the product wont aerate properly."
Tiffany suggests keeping an eye on the solids levels at typical eating conditions. If the solid fat content is on the high end of the SFC scale at 92°F and 104°F, the perception of a waxy mouthfeel is notable," he says. If the solid fat profile is low at 92°F and 104°F, the shortening is perceived to have a quick melt."
For his part, Neddersen sets the benchmark at 10% to 25% solid-fat contentideal for lending good plasticity at a given temperature.
And plasticity is crucial, Tiffany says, as it directly influences dough rheology. If a shortening is too hard or brittle, the dough can tear or break, causing production issues. If a shortening is too soft, the dough can become soft and sticky, which also causes production and finished-product issues. Processors influence shortening plasticity through maintaining balanced solids levels and votating and tempering the product under proper conditions. In so doing, they target the formation of stable beta-prime crystals in the finished product. These small, needle-like crystals break and reform easily under stress, Neddersen explainsunlike plain" beta crystals (no prime), which he says are large and plate-like and give a hard, grainy texture."
Finally, experts advocate choosing a baking fat with oxidative stability. We primarily think of stability in terms of frying applicationswhere the oil is under temperature and oxygen stressand for good reason. Again, doughnuts illustrate why this matters for the baker, as the oil must be stable enough to resist breaking down in the fryer," notes Bob Johnson, director of research and development, Bunge Oils, Bradley, IL. If the oil breaks down, it may contribute undesirable flavors or require discarding to prevent the formation of off flavors."
Further, Knowlton points out that products like crackers and cookies that sit longer on the shelf require more oxidative stability so the fat doesnt go rancid over time." Crackers, in particular, undergo surface spray-oil treatment to increase lubricity and help the product clear your mouth when you eat it," she says. Applications like these, which directly expose the oil to oxygen, redouble the importance of oil stability.
Hydrogenates are handy
Partial, rather than full, hydrogenation wound up being the most-effective means of producing shortenings with broad bakery application. The process yields unsaturated fatty acids in which the double bonds take on the isomeric form known as trans, and its these trans fatty acids, Hughes says, that are functionally similar to saturated fatty acids, having both a linear configuration and a high melt point. This results in functional solids in the shortening, and the benefit of lower levels of oxidatively sensitive polyunsaturates."
The most common trans fatty acid is the monounsaturated trans-isomer elaidic acid, or C18:t. This isomer has a significantly higher melt point than its cis-isomer sibling oleic acid," Hughes says. When combined with the other fatty acids in a typical partially hydrogenated soybean product, you end up with a wide temperature range of plasticity." Processors discovered by manipulating variables like duration, temperature and catalyst, they could direct hydrogenation to produce fats with a seemingly infinite variety of SFC curves to meet the very specific needs of bakery applications," he says.
In icings and fillings, for example, the trans fats in partially hydrogenated shortenings aerate easily and stably over the products shelf life. In laminated products," says Neddersen, they have good plasticity when the products are being produced and good eating qualities at the time of consumption. Generally, trans fats crystallize quickly into their optimal form."
Thus, all-purpose shortenings made from partially hydrogenated soybean and cottonseed blends came to dominate baking. They earned their keep, Morehart says, because they were very forgiving from a functional perspective, from an operational perspective and from a perspective of shelf life and interaction with other ingredients." Their clean taste profile also worked in their favor, as did their vast and easily tapped domestic supply, their amenability to room-temperature storage and their relative low cost and low-saturates levels compared to butter and animal fats.
Seismic sans-trans shifts
Alas, if only the story ended there, for the very trans fatty acids that make partially hydrogenated shortenings so handy was found to increase the risk of coronary heart disease, raising levels of bad" low-density lipoprotein (LDL) cholesterol and lowering levels of the good" high-density lipoprotein (HDL) kind. Trans fatty acid levels in some shortenings can range from 28% to 40%, says Michelle Peitz, technical sales representative, ADM.
So, with health authorities here and abroad raising alarms about lowering trans, FDA set 2006 as the year when food producers would have to list trans fats levels on product packaging. And thus began the seismic sans-trans shift were still grappling with today.
The move has proven something of a jobs program for lipid scientists, whove been in high demand as manufacturers search for sans-trans solutions. And the search continues. The ingredient industry is developing a wide variety of low-trans options to meet the needs of the food industry," Tiffany says.
Interest in interesterification
And thats where the innovation lies. With the movement away from partially hydrogenated fats," Johnson says, bakers have taken a number of different paths for producing functional bakery shortenings." He says that palm and palm blends have worked well in some applications, as have lower-saturate options that use liquid oils with fully hydrogenated soybean or cottonseed oils."
Neddersen notes the use of emulsifiers designed to encourage crystallization, aeration and plasticity following the removal of trans fats. And there is new hydrogenation technology that encourages more hydrogenation to the cis isomer rather than the trans isomer," he says.
But currently, focus has settled on interesterification of soybean-oil products as a way of providing a domestic solution for trans that performs well in bakery applications," Johnson says. While interesterification itself is not new, recent developments have applied enzymes, rather than chemical catalysts, to the process. Enzymatic interesterification, or EIE, utilizes immobilized enzymes to move fatty acids from one triglyceride backbone to another in the same fashion that our bodies do when we ingest fat," he says.
Principally, EIE replaces the trans elaidic acid with saturates that contribute appropriate solids and functionality in the finished product. Processors might achieve a similar effect by replacing trans fats with palm oil, which is also high in saturates. But whereas palm contributes primarily palmitic acid," Johnson says, the EIE soy contributes stearic. There is much debate about the impact of saturates."
According to the American Heart Association, Dallas, "Even though stearic acid is a saturated fat, studies have suggested that it has little effect on blood cholesterol."
In replacing trans fats, some manufacturers choose to work with naturally stable oils instead, like mid-oleic sunflower oil and canola. Then, there are oils from trait-enhanced crops, such as soybean," Neddersen says, which yield oil high in oleic acid and lower in linolenic acid." This improves the oils oxidative stability.
Knowltons company uses trait enhancement, manipulating the genetics of soybean oil, to create its zero-trans product. Typically, soybean oil has just a little over 20% oleic acid," she explains. As a monounsaturate, oleic acid is more stable than polyunsaturated fatty acids. But soybean oil typically has high polyunsaturated fatty acidsclose to 60%. What we did is switch that around: We reduced the polyunsaturated fatty acids and increased the oleic acids." That means that a soybean oil that once was 22% oleic is now 75%. And that reduction in polyunsaturated fatty acids makes the oil less susceptible to rancidity," she says. Therefore, it can be used for long-shelf-life applications where soybean oil typically cant be used."
Albeit more stable than most liquid oils, the products still liquid. But if you bring in solids through, for example, a hard stock like a fully hydrogenated oil with no trans fats," Knowlton continues, you can make a zero-trans shortening by combining those two either through blending, in some cases, or interesterification."
Drop in any time?
Could baking sans-trans be this simple? As Tiffany says, The low-trans alternatives available today are, in some cases, being used as drop-in replacements for high-trans products."
For example, blends of palm oil and hard stockseither from palm fractions or fully hydrogenated vegetable oilshave been shown to produce functional zero grams trans per serving pastry margarine or shortening," says Peitz. Similarly, blends and products made from enzymatically interesterified soybean and palm kernel oils have found use as zero-grams trans per serving" icing shortenings. These blends offer the bright-white color and melting characteristics customers desire."
In cakes and cookies, palm and liquid domestic oil blends tend to work very well," Peitz continues. We have also found that enzymatically interesterified soybean oil-based shortenings function well in cookie and cake applications." And when looking for a low- to-no-trans frying oil for doughnuts, manufacturers can turn to palm/liquid vegetable oil blends with fully hydrogenated hard stocks to make doughnuts that she says have a well-rounded flavor profile and the optimum level of solids to control oil migration and glaze/sugar adhesion."
But not all sans-trans solutions substitute so easily. You cant just remove trans fat and expect a different fat to function in the same way," Morehart says. It normally would result in some kind of manufacturing changewhether it be controlling dough temperature in different ways, or adding the fat in a different way, or modifying the mixing times or temperatures."
Palm oil, for instance, is typically firmer and more brittle than partially hydrogenated oilsto say nothing of its somewhat less familiar tropical" flavor. On the other hand, some substitutes are actually softerso much so that a trans-free sandwich cookie filling may take longer to set before its safe" to place the crowning cookie half atop it. And, Neddersen adds, Icings or fillings may not need to be mixed as long, either, as over-mixing may cause them to break down."
Among the greatest challenges that bakery manufacturers face involve changes to oil handling, says Johnson. The systems in many bakeries were designed for very stable, very forgiving partially hydrogenated shortenings," he notes. With the movement to less stable, lower-saturates products, the care in handling and protecting the shortenings becomes much more critical. Auditing of bulk handling systems and upgrading to include nitrogen blanketing are the most common improvements being made."
Hughes also notes the importance of controlling exposure to oxygen when incorporating non-hydrogenated shortenings into a bakerys operational system. Even a small amount of liquid oil can produce off flavors in a blended margarine or shortening," he says. Hes seen broader industry use of the antioxidant TBHQ as a preventative measure, as well as a move to reduced shelf life codes and improved oxygen-barrier packaging.
Finally, Johnson says, The other most common challenges have been in temperature control. Partially hydrogenated shortenings had a wider plastic range and could be used over a broader temperature range. Many of the post-trans shortenings will become too firm or too soft with fluctuations in temperature."
Even if our new sans-trans solutions raise health or sustainability issues of their own somedayremember, trans fats themselves were once hailed as miraculousNeddersen doesnt foresee going completely back to the drawing board again. I think we have done a good job replacing trans fat in baking," he says. One still finds limited use of trans fat in some of the more challenging applications," he says. But those areas have made good advances the last few years."
Kimberly J. Decker, a California-based technical writer, has a B.S. in consumer food science with a minor in English from the University of California, Davis. She lives in the San Francisco Bay Area, where she enjoys eating and writing about food. You can reach her at [email protected].
In fats, stability reflects saturation. Thus, it should come as no surprise that, traditionally, butter, butter and more butter" was the standard in most bakeries, says David Hughes, project manager, bakery applications, Ventura Foods, Brea, CA. Old World bakers turned to highly saturated lard and tallow as close secondsand not only for their stability but for their functional benefits, as well.
As John Neddersen, senior application scientist, fats & oils, emulsifiers, DuPont Nutrition & Health, New Century, KS, says, Lard, butter and tallow have a lot of the properties discussed earlier. They have solid components that have a desirable melt profile, they are oxidatively stable and they have desirable processing characteristics." Even today, youll find artisan bakers who swear by lard in their pie crusts, or pure creamery butter in their cookies and cakes.
But not all bakers want toor canadhere to tradition. Even in the first half of the 20th century, advances in fat and oil technology accompanied the increasing industrialization of the food supply, which let suppliers transform virtually any oil into a shortening with the functional properties its users needed. The health crusade in the 1980s against saturated fats, whether animal-derived or "tropical" in origin, sealed the deal.
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