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March 26, 2008
Frying is hard on oils. Under abusively high temperatures, the oil must flawlessly cook item after item. Ingredients, such as seasonings on the food being fried, may fall off and, if the fryer is open, oxygen will react with the oil, all contributing to the fats degradation.
Add to that the challenge of maintaining consumer expectations of flavor, color and texture built on the performance of partially hydrogenated fats. "Thats the challenge of our oil formulation efforts, to maintain to the fullest possible extent all the finished product attributes that consumers expect, but with a different frying medium," says Bob Wainwright, technical director, oil and shortenings business, Cargill Dressings, Sauces and Oil, Charlotte, NC. "The fat frying medium is a substantial component of the finished food, as a result of absorption of the oils and fats."
Despite rumors to the contrary, no one-size-fits-all oil exists. After first determining whether an oil might be suited to a particular application, several other important factors must be considered: the perceived healthfulness of the oil; the impact of breakdown products on the finished product; smoke point; the frying equipment; desired attributes of the end product; and how the ingredient statement will meet finished product expectations.
If declaring the lowest amount of saturated fat is important, think about canola. Canola and high-oleic canola oils have 7% saturated fat. Safflower has 8%; flaxseed, 9%; sunflower, 12%; corn, 13%; olive oil, 15%; soybean, 15%; peanut oil, 19%; and cottonseed, 27%. Not surprisingly, solid fats have the highest levels: lard has 43%; palm, 51%; butter, 68%; and coconut, 91%.
Monounsaturated fat is also very high in canola, at 61%. High-oleic canola has 70%. Safflower oil exceeds this, with approximately 77% monounsaturated fat. Olive oil follows with 75%; peanut oil with 48%; lard, 47%; palm, 39%; corn, 29%; and butter, 28%.
Polyunsaturated fats include heart-healthy alpha-linolenic acid (ALA, an omega-3 fatty acid) and linoleic acid (LA, an omega-6 fatty acid). Sunflower oil leads with 71% linoleic, followed by corn oil, 57%; soybean oil, 54%; and cottonseed oil, 54%. Sunflower and corn oil have 1% alpha-linoleic. Soybean has 8%, and cottonseed has a trace. These numbers can vary with selective breeding.
Desired frying temperature and conditions will impact oil selection. Generally, most foods are fried at 350° to 375°F but its not uncommon for temperatures to rise well above the optimum temperature. As the amount of free fatty acids increases in an oil, the smoke point decreases and the less stable the oil becomes. Olive oil is not recommended for frying, because it has such a low smoke point428°F., Smoke points, as determined by the University of Lethbridge, Alberta, Canada, increase as follows: safflower, 446°F; cottonseed, 450°F; refined corn, 450°F; soybean, 453°F; sunflower, 464°F; high-oleic safflower, 468°F; canola, 468°F; peanut, 471°F; high-oleic canola, 475°F; and high-oleic sunflower, 478°F.
Stability impacts both flavor and health, says Gerald McNeill, Ph.D., director of R&D and marketing, Loders Croklaan, Channahon, IL. "This is particularly important in heavy-duty frying operations, such as in open fryers in restaurants or industrial fryers in manufacturing plants, because the oil is reused until it is spent," he says.
Polyunsaturated fats are considered to be healthier, but not necessarily under the extreme conditions of a fryer laid open to air. Research at the University of Minnesota, Minneapolis, concluded that, when heated at 365°F for 30 minutes, highly unsaturated vegetable oils, such as corn, soybean and sunflower oil, will form the aldehyde, hydroxyl-trans-2-nonenal (HNE), a toxic compound (Journal of theAmerican Oil Chemists Society, 2004; 81(12):1,137-1,141). The length of cooking time is proportional to the levels produced. HNE continues to develop with subsequent reheating of the oil.
According to McNeill, "polyunsaturated fats generate breakdown products more rapidly than other fats, but the polyunsaturated breakdown products are likely more harmful to people than the products from saturates or monosaturates. Also, due to their lack of stability, polyunsaturates are likely to generate off-flavors, rapidly leading to a higher cost in use."
Hand it to palm oil
For frying applications, McNeill recommends oils that contain significant amounts of monounsaturated and saturated fatty acids. "Palm oil naturally contains an equal balance of mono-unsaturated and saturated fat, and is ideally suited for heavy-duty frying," he says.
Palm oil is semisolid at room temperature. This gives it "the ability to convey stand-up properties," says Wainwright. "It has the ability to incorporate air, so it has the possibility to be utilized in applications that require creamability; or it has the ability to be blended with liquids and still convey some semblance of structure." Fractionation can provide "a higher-melting fraction that can be utilized as a structuring agent," he continues. "That higher-melting fraction is arrived at purely by fractionation. Therefore, for those circumstances where hydrogenation is something that people would rather not have appear on the label, yet they need something that has some structure associated with it, the hard fraction of palm might be an appropriate option."
McNeill explains that fractionation is a physical process "that presses the palm oil to squeeze out the liquid portion. Solid palm oil can be inconvenient to use. Fractions of palm are liquid and preferred in temperate or cool climates," he says. "The fractions are predominantly unsaturated, with a low level of polyunsaturates. About 40% is saturated. Both palm oil and palm fractions are widely available commodity oils and are priced comparably to commodity soybean oil." Combining these fractions can deliver a specific functionality.
Palm oil continues to be categorized as a saturated fat, "in spite of its well-balanced fatty acid composition," notes McNeill. "Although recent science shows that saturated fats are not as bad as once made out to be, the consumer continues to be urged to reduce saturated fat intake as much as possible." Therefore, to reduce saturates, suppliers are blending stable palm oil with other, low-saturate vegetable oils.
Loders Croklaan offers a palm and soybean oil blend that "provides an unlimited supply of stable, low-saturated-fat frying oil at reasonable cost," says McNeill. This oil blend requires no special frying equipment, as the oil is fully stable. It can be used in every kind of frying application, except donuts. It doesnt suffer from limited availability or the high costs associated with genetically modified vegetable oils.
Canola oil can
A popular choice for frying is canola oil, which "in general, is one of the healthiest oils in the marketplace," says Angela Dansby, communications manager, CanolaInfo, Canola Council of Canada, Winnipeg, Manitoba. "In addition, canola oil has a very light texture. It has a mild, neutral flavor, so the oil itself does not impart flavor to the items that youre frying, so foods tend to fry up very light and crispy as a result of the texture of the oil. Its an excellent frying oil from a sensory perspective, and also from a health perspective."
What is unique about canola is its FDA-allowed qualified health claim: "Limited and not conclusive evidence suggests that eating about 1½ tablespoons (19 grams) of canola oil daily may reduce the risk of coronary heart disease due to the unsaturated fat content in canola oil. To achieve this possible benefit, canola oil is to replace a similar amount of saturated fat and not increase the total number of calories you eat in a day. One serving of this product contains (x) grams of canola oil."
Canola is especially well-suited for frying applications, because it naturally has one of the highest smoke points available, and many commercial frying operations prefer high-oleic canola for its prolonged stability under high heat conditions. "It has an even higher smoke point than classic canola oil, and it has enhanced performance characteristics and longer fry life," says Dansby.
Typical canola oil contains 61% oleic acid. High-oleic canola is produced from canola plants that have been selectively bred to contain 70% oleic acid to displace some of the polyunsaturated fats. Although these polyunsaturated fats, including ALA and LA, are healthy, they decrease the oil stability. While this may be less of a consideration in the development of a salad dressing, it could be very important to a highly abusive frying operation.
Selective breeding offers the means to increase certain attributes. Dansby notes there are a lot of possibilities, but further development "depends on what makes sense from a commercial standpoint and what either the consumers or the commercial sectors is willing to pay for."
Wainwright sees further development of trait-enhanced oils. "Cargill has had trait-enhanced canola oils for frying applications for a number of years. More recently, we brought into the portfolio low-linolenic soybean oil. There are additional efforts underway within Cargill, as well as within the industry, to further alter the fatty acid composition of soybean oil and canola oil to make them even more appropriate for applications." He also notes industry interest in naturally occurring antioxidants, like tocopherols.
Using the ol soybean
New healthier and more-functional generations of soybean oil are on the horizon, according to Richard Galloway, staff consultant, Qualisoy, and board member and composition consultant to United Soybean Board, Charleston, SC.
Asoyia, Iowa City, IA, produces an ultra-low-linolenic oil with less than 1% linolenic. This was first introduced in 2004, with a second-generation oil now entering production. This new low-linolenic oil is also considered a mid-oleic, because it has a higher level of oleic acid.
"The next soy oils to be commercialized include high-oleic soy and mid-oleic soy," says Galloway. High-oleic soy has over 75% oleic fatty acid. Mid-oleic soy has over 55% oleic and less than 3% linolenic. He believes both will offer excellent frying performance.
"Low-linolenic soybean oil has a broader application to meet frying needs than first thought," Galloway says. "Yum brands reports excellent functionality from its use as a frying oil in their KFC chicken products." Generally, low linolenic is used for lighter-duty frying. "Surprisingly and unexpectedly, KFC reports no increased oil turnover from switching from shortening to low-lin soy," he says.
To replace vegetable shortenings in most frying applications, Galloway suggests using high oleic, mid-oleic or low-linolenic soybean oilseither alone or blended with commodity soy. "Certainly, the mid-oleic and high-oleic products will provide any degree of stability that the fryer wants or needs," he says.
The basic flavor of low-linolenic or increased-oleic soybean oils does not change vs. commodity soy. "KFC thoroughly tested the flavor of its famous-recipe chicken with low-lin soy, their former shortening product and other alternatives, including high-oleic canola," notes Galloway. "Low-lin soy provided them with a chicken product indistinguishable from their former shortening."
From a labeling perspective, soybean oil has lower saturates than cottonseed and palm. Plus, "low-linolenic soy is lower in price than any other vegetable oil alternative," Galloway says.
High-oleic soy is expected on the market in 2010, and mid-oleic should be ready about the same time. He cautions, however, that quantities the first year will be limited to test volumes, but will increase rapidly thereafter.
Sunflower and safflower growing
Sunflowers are most appreciated for their cheery disposition, but food technologists recognize their oils frying value. Linolenic sunflower oil is more suited as a salad oil. But high-oleic sunflower oil, with a minimum 80% oleic acid and a light, neutral flavor, is ideal for commercial frying. Compared to olive oil, high-oleic sunflower oil is higher in monounsaturates and lower in saturates. Mid-oleic sunflower oil has an average of 60% to 65% oleic acid.
Safflower oil proves all comparably labeled oils are not alike. California high-oleic safflower oil has a minimum of 75% oleic acid. High-oleic safflower oil from plants grown in Montana and western North Dakota has a minimum of 80% oleic and only 5% saturated fat. Montola, Missoula, MT, claims its high-oleic safflower oil has a smoke point of 530°F.
Picking cottonseed oil
According to Clay King, Ph.D., associate professor, oilseed researcher, Texas Womans University, Denton, TX, "cottonseed oil does not impart any strong flavors of its own, but it slightly magnifies the flavor of products to which it is added. When its flavor is detected, it does have a slightly mild, bland, nutty buttery flavor."
Because of its flavor, it is often used to fry potato chips. Traditionally, cottonseed oil has been used in Japan and Korea. In the United States, it is often used for frying Asian foods. Its saturated fat content adds stability. "For an oil that has not been hydrogenated, cottonseed oil is one of the longest-lasting," says King.
Cottonseed oil has a 2:1 ratio of polyunsaturated to saturated fatty acids. The latter are primarily palmitic and stearic acids.
Tocopherol levels in refined cottonseed oil average about 500 parts per million, or 15 mg. "These levels are comparable or higher to other oils, which is a positive attribute," since alpha tocopherols work as a natural antioxidant, notes King.
Cottonseed oil is usually 3 to 5 cents more expensive than other commodity oils, and it is frequently blended with other oils, such as canola, corn and sunflower.
But how do these trans alternatives stack up next to the original? An independent frying oil competition conducted by FryTest.com compared nine trans-fat-free oils to a partially hydrogenated oil containing 28.79% trans. Contestants included ACH, Bunge, Cargill, ConAgra and Loders Croklaan, whose oils were challenged to fry french fries 300 times over a 13-day period. The oils represented a wide range of blends, such as cottonseed/corn, corn/sunflower, palm/cottonseed, high-oleic canola/corn and many others. Several single oils competed, including low-lin soy, high-oleic canola, mid-oleic sunflower and more. All told, 42 oils were tested.
Testing was multifaceted. Total polar materials via column chromatography measured fry life. Trained panelists evaluated the oil for off-flavors, off-odors and changes in texture or appearance. The food-to-oil ratio determined how many pounds of fries were cooked per pound of oil. Panels of approximately 50 consumers blind-taste-tested the finished products.
According to FryTest.com, all of the trans-fat-free oils were functionally equivalent to or better than partially hydrogenated oil. At the end of testing, all of the oils had considerable fry life left.
With multiple oil options available, its simply a matter of choosing the best tool for the job, both in performance and in finished product attributes.
Donuts, for example, require special care. "The fat must be a solid," McNeill advises. "If liquid oils are used, the donut will be limp and oil will leak out. Oil will migrate to the coatings, causing them to soften and slide off." He recommends palm oil as "ideal for frying donuts, because it is naturally stable without the need for hydrogenation."
Liquid oils are often chosen for potato chips, "although there are certain potato chip manufacturers who prefer a different sort of finish and a different sort of mouthfeel," says Wainwright. "They are looking for a trans-free option that leaves the finished chip with a drier finish, rather than an oily finish, and also has a different mouthfeel; typically, a greasier type of mouthfeel."
Breaded products, such as chicken or fish, may be the most difficult to work with because of the likelihood of pieces of the coating falling off into the oil, says Wainwright. "Things that fall off into the frying fat become more of an issue than they were in the past, because we are stepping away from reasonably robust shortening systems," he warns.
Fry-management practices, such as frequent filtering and de-crumbing, are important. "The frying manufacturers are working as well to continue to improve their equipment to better manage the maintenance of the oil quality," says Wainwright.
For example, Belshaw Bros., Seattle, has developed a donut fryer designed to minimize sediment and extend oil life.
Studies have shown an electric fryer offered by Frymaster, Shreveport, LA, maintains the life of trans-fat-free oil for up to 18 days. Compared to its other models, this fryer has a significantly different rotating element with an enhanced design. The company suggests a four-part system to enhance oil life: selecting the right oil, choosing the right fryer, following the right cooking process, and establishing the right maintenance program.
FMC FoodTech, Chicago, manufactures a poultry fryer designed to optimize the life of trans-fat-free oil. Its filtration system filters out suspended flour particles as small as 5 microns. A second filtration system filters out particles at the infeed. Dual exhaust vents in the hood create a steam blanket over the top of the cooking oil, reducing oxidation.
Engineering does not stop there. Instrument manufacturers continue to work to develop types of devices "that can be fitted to fryers, so that we have the possibility to monitor on a real-time basis what might be going on in the fry kettle, say more from a frying-fat-chemistry perspective," says Wainwright.
In the end, creating the perfect system is likely a team effort. "It becomes extremely important to have a deep understanding of the application and the attributes that the end user is after," notes Wainwright. "Thats where the dialogue between the supplier and the end user becomes especially critical. So, rather than lobbing samples over the wall, what is most efficient and what is most effective is to get very close to the customers and really get a deep appreciation of what it is they wish to accomplish."
Cindy Hazen, a 20-year veteran of the food industry, is a freelance writer based in Memphis, TN. She can be reached at [email protected].
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