Fried Food Solutions

Oil suppliers have been working diligently to replace trans-laden frying fats for years. The dilemma has been that partially hydrogenated oilsand their trans fatty acidsare extraordinarily stable as well as inexpensive.

Fats 101 

Heat and air can destabilize fatty acids double bonds and cause detrimental reactions. Hydrogenation replaces unstable double bonds, which increases oxidative stability and changes the melting point, but also creates trans isomers, which produce desirable functional attributes, but arent so good for our hearts.

The more double bonds, the greater chance oxidation reactions will occur. Oleic acid has one double bond. It is referred to as C18:1, says Dave Dzisiak, global oils leader, Dow AgroSciences, Indianapolis. Linoleic is C18:2. It has two double bonds. Linolenic is C18:3. Linolenic is also known as an omega-3-type oil. C18:0, or stearic acid, has no double bonds, or is saturated. Canola and soybean naturally have about 10% 18:3 (linolenic). Soybean also has about 20% oleic (18:1). These are polyunsaturates.

Polyunsaturated fats are about 100 times less stable from a chemical point of view than saturated fats, when you heat them in air, says Gerald McNeill, Ph.D., R&D director, Loders Croklaan USA, Channahon, IL. All those double bonds break down into dozens of breakdown products. Some of these give off-flavors. Some of them give dark colors. Indeed, some of those breakdown products are unhealthy. Hydroxy-trans-2-nonenal is a known cytotoxin. It damages DNA and protein. It accelerates the aging process, he says.

In general, monounsaturates are 10 times more stable than polyunsaturates. Although specific oils are labeled as saturates and mono- and polyunsaturates, they are really mixtures of different fatty acids. For example, cottonseed oil generally consists of 70% unsaturated fatty acids, including 18% monounsaturated (oleic), 52% polyunsaturated (linoleic) and 26% saturated (primarily palmitic and stearic). Regular canola oil has about 7% saturated fatty acids, 61% monounsaturated fatty acids and 22% polyunsaturated fatty acids.

Processing parameters 

Replacing trans fats is a case by case endeavor. Not only do processing and flavor requirements vary, but shelf life is important: damaged oil can create an off flavor after a few weeks on the shelf. In replacing trans in fried foods, think about the system demands and the potential for reactions.

Pan frying is the least demanding. It is relatively quick, requires less oil, food soaks up the oil and fresh oil is used for each item. Polyunsaturated or monounsaturated oils perform well here.

The real issue comes when you start deep frying, says McNeill. Restaurant deep frying is extremely abusive. A fryer is filled with perhaps 35 lbs. of oil. Its kept hot all day long and then shut off for the night and reused the next day. Oil is added as needed. Unlike continuous frying, where the ratio of food to oil is quite high, and oil is replenished continuously, in batch frying, the oil is not replenished as frequently in proportion to food fried, and the oil remains in the fryer longer, says Neil Widlak, director of strategic technology development, ADM, Decatur, IL.

Industrial, continuous deep frying frequently occurs in an environment in which air is excluded. A reaction requires heat and air, McNeill explains. In some kinds of industrial continuous fryers, air is driven away from the surface of the oil. There, less-stable oils wont oxidize too much.

Doughnuts are particularly demanding; not only do they need a stable oil, but it has to be a solid fat, says McNeill. Doughnuts should be dry and not release oil, but coatings must adhere. They should leave little to no oil residue.

Finished, fried snack-food product attributes relative to flavor, mouthfeel, texture and product appearance are a function of the frying medium, says Roger Daniels, directornew business development, Bunge Oils, Bunge North America, Bradley, IL. The heated oil or shortening provides thermal energy sufficient to liberate moisture from the food component. In addition, this thermal energy input contributes to structure development through starch gelatinization and protein denaturation. As a general rule, liquid oils yield fried snack-food products that appear less dry in appearance and texture than shortenings.

Tom Tiffany, manager, food oils applications, ADM, says that food-to-oil ratios and flavor are also important. The source oil contributes to the flavor of the food being fried, he says. Certain oils provide more of the deep-fried flavor, compared to other oils used for deep frying.

Fried food solutions 

McNeill recommends palm oil for many applications, including snack foods and doughnuts. Palm oil has a 50:50 mixture of monounsaturates and saturates and a butter-like consistency. 

Liquid palm oil is suitable for most heavy-duty frying requirements. Widlak says palm oil is semisolid at room temperature, which allows the oil to congeal on fried products, reducing oil migration and imparting a less oily mouthfeel on doughnuts and other fried foods not immediately consumed.

Fractionation can create oils with specific functionalities, such as tailored melt points. In fractionation, solid palm oil is melted and slowly cooled, McNeill says. When it cools, you generate big, solid crystals. You can filter them off and isolate the liquid component (palm olein). Palm olein is predominately unsaturated, 60%, and 40% saturated.

To further reduce saturates, Mc- Neill suggests blending palm and soybean oils, with 60% palm and 40% soybean giving a good frying oil.

Some fry studies indicate foods fried in fats with some polyunsaturated fats impart a greater level of desired fried-food flavor, says Widlak. Generally, vegetable oils naturally low (less than 3%) in linolenic acid are suitable for snack foods, most convenience foods and fried baked goods (doughnuts, etc.). Domestically sourced oils, naturally low in linolenic acid and commonly used for frying, include corn, sunflower, cottonseed and peanut oils. Oilseed genetics have produced low-linolenic canola and soybean oils and mid- and high-oleic sunflower and canola oils.

Omega-9 (high-oleic) oils are developed by natural selective plant breeding. This next generation of canola and sunflower varieties have higher degrees of stability, they are low in saturates, and they offer a great taste. They have twice the stability of low-lin soybean oil, says Dzisiak. Their extended frying life helps offset their higher cost. They can give twice the frying time as many other zero trans fat alternatives, he continues.

Another advantage of omega-9 oils is their lower saturated fat content, roughly half that of soybean oil. Soybean would have about 15% saturated fat. In canola we have about 7% saturated fat, Dzisiak says. Looking at a serving of french fries cooked in an omega-9 oil, as compared to a partially hydrogenated soybean oil, we would take the saturated fat content from about 7 grams per serving to less than 2 grams per serving. On the trans fat side, we would reduce the trans fat content from about 5 grams per serving to 0.25 grams per serving.

Interesterification is a technique used to tailor-make an oil. The rearrangement of fatty acids on the glycerol backbone to create different triglycerides results in functionality differentiated shortening and oils, says Daniels.

According to Widlak, interesterified oils from low-linolenic oils and fully saturated fats provide equivalent stability of domestic oils, with similar semisolid characteristics as palm oil, making interesterified oils suitable for replacing plastic frying fats where minimal free oil on the fried-food surface is preferable.

The important thing to remember is not all trans-free frying oils are interchangeable for all fried-food applications, just as not all frying oils containing trans fats are suitable replacements for all frying applications, says Widlak.

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].