Transforming Fat Nutrition

In the early 1980s, research showed animal fats and tropical oils typically used in frying, baked goods and confections increased blood cholesterol levels. Public concerns over the fats contribution to the risk of heart disease forced food manufacturers to look for alternatives.

In place of saturated fats, many companies turned to partially hydrogenated vegetable oils. During hydrogenation, some of the cis fatty acids convert to the trans form, producing trans fatty acids. Low in saturated fats and free of dietary cholesterol, these were considered ideal alternatives for frying, baking and providing the desired texture in foods, without the undesirable health effects associated with saturated fats.

Trans fats and health

Fast forward to the 21st century, where research shows that, like saturated fats, trans fats also negatively impact health. Recent evidence examining the relationship between dietary trans fatty acids and blood lipids shows that trans fatty acids not only raise low-density lipoprotein (LDL) cholesterol, but also slightly lower high-density lipoprotein (HDL) cholesterol, with a greater adverse effect on the ratio of total to HDL cholesterol.

The majority of epidemiologic studies have linked trans-fat intake with increased morbidity and mortality from coronary heart disease (CHD). In addition, trans fats may also promote inflammation, cause endothelial cell dysfunction, and may influence other cardiovascular-disease risk factors, such as reducing the activity of serum paraoxonase and affecting insulin sensitivity.

While consumer media has been relentless in reporting on trans fats effect on health, some perspective is warranted. The average American eats a small amount of trans fats and a much larger quantity of saturated fats. Trans-fat intake accounts for about 2% to 4% of total calories, while saturated fat intake is 11% or 12%.

An Institute of Medicine (IOM) report, Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids (2002), states that saturated fats, trans fats and dietary cholesterol have no known beneficial role in preventing chronic disease and are not required at any level in the diet. FDA believes eliminating trans fatty acids completely from the diet would require such extraordinary perhaps impossibledietary changes (especially the elimination of dairy products and meats that naturally contain trans-fatty acids) that eliminating trans could cause an inadequate intake of some nutrients and create health risks.

Oil options

In general, consumers know which fats are good and bad. As a result, food manufacturers have seen a demand for foods free of trans, low in saturates and rich in beneficial fatty acids, such as omega-3s.

Accelerated by increasing health concerns and fueled by FDAs decision to include trans-fatty-acid content on the Nutrition Facts label as of Jan. 2006, the fats and oils industry has worked diligently to develop new ingredients and improved technologies to meet food companies needs for fats that preserve the structural and taste of foods without negative health effects.

Interesterification using mixed fats. Interesterification uses highly saturated hard fats and liquid vegetable oils and rearranges the fatty acids in triglyceride molecules to produce fats with the best characteristics of both fats. Interesterification chemically or enzymatically hydrolyzes the ester bond between the fatty acid and glycerol, which results in a mix of triacylglycerols with fatty-acid distributions similar to the original starting fats. This allows the production of customized fats with a range of melting points, increased stability and added creaminess, for applications including margarine, baked goods and confections. Interesterified end products contain no trans fats, but still have the desirable physical properties, taste and stability of hydrogenated fats. Saturate content may be higher compared to conventional products, but the majority is comprised of stearic acid, widely accepted as cholesterol-neutral.

This is generally regarded as a healthy option, although a recent study questions one interesterified fat with stearic acid, finding it adversely affected human metabolism of lipoproteins and glucose compared to an unmodified, natural saturated fat. (Stearic acid-rich interesterified fat and trans-rich fat raise the LDL/ HDL ratio and plasma glucose relative to palm olein in humans, Kalyana Sundram, Tilakavati Karupaiah, KC Hayes, Nutrition & Metabolism, Jan. 15, 2007). The Malaysian Palm Oil Board provided funding for the study, and Sundram is employed by the Board.

Hydrogenation modification. A range of proprietary techniques can highly hydrogenate oils, producing minimal trans typically less than 10%. Several of these use nickel and/ or other mixed metal catalysts, along with such methods as lower temperatures or electrochemical procedures to selectively prevent trans-isomer formation and encourage cis-isomer formation. This keeps the overall transfatty- acid content very low. However, it is important not to introduce trans fats during the last step, deodorizing, by modifying equipment and lowering deodorizing temperatures.

Switching to saturates. Oils with higher melting points and a saturatedfat content of about 50% might also replace partially hydrogenated fats, particularly in the baking and confectionary industries. These are available in fractionated forms, which can be used in various applications. For example, soft-fat fractions may be used as cooking oils, while hard-fat fractions from the same oil source work in margarine, shortening and frying oils.

This range of fractionated products offers a number of options for saturated fat, melting point and plasticity. However, the trans-fat-free benefit must be weighed against saturated fats negative effect on blood cholesterol levels.

New strains. Traditional seed-breeding practices can be used to modify oils nutritional or technical properties. Researchers have used these techniques to select seed mutants with higher oil yields or a modified fatty-acid composition. For example, a soybean oil with 3% or less linolenic acid vs. a conventional 7%, and more than 50% oleic acid vs. up to 30%, is more stable, less easily oxidized, has a longer shelf life and performs better during deep-frying. The oil does not require hydrogenation, so trans fats are eliminated.

Genetically engineered seeds produce oils with a targeted fatty-acid composition, such as soybean oils with increased omega-3 fatty-acid. Many oils from plants grown using seed-breeding and genetic-engineering techniques are now commercially available. The canola- and sunflower-oil industries have used these methods with success to develop new products, such as those with high- or mid-oleic acid contents. Low-linolenic soybean oils are also becoming widely available (see sidebar: Soybean Success).

On the horizon

In the research pipeline are low-saturate soybean oils, with less than 7% saturates compared to a traditional 15%. Soybean oil already has low saturates relative to many oils, but significant investigation is underway to develop varieties with even further reduced saturates, especially palmitic fatty acids. Palmitic acid, one of the most-common dietary fatty acids, along with myristic and lauric acid, has been shown to raise blood cholesterol levels.

Additionally, soybean oils with increased omega-3 fatty acids are in development. Omega-3 fatty acids have been shown to reduce risk of cardiovascular disease by preventing cardiac arrhythmia, lowering serum triglyceride levels, decreasing thrombotic tendency and improving endothelial function. Soybean oil is a good source of the omega-3 fatty acid alpha-linolenic acid, which the body converts into eicosapentaenoic acid (EPA) and docasahexaenoic acid (DHA), although not very efficiently. Researchers are working on genetically modified oils that are high in stearidonic acid, which more readily converts to omega-3s and is more effective in increasing tissue DHA and EPA concentrations. The goal is to create an affordable, land-based, renewable omega-3 source that can create great-tasting foods.

Finally, researchers are exploring options for soybean varieties with high stearic-acid content. Since stearic acid is cholesterol-neutral compared to other saturates, a high-stearic oil would provide a healthier option for applications requiring solid fats.

Health effects of modified oils

The cardiovascular-health effect of five different soybean oilsregular, low saturated, high oleic, low alphalinolenic and partially hydrogenated were tested by researchers at Tufts University, Medford, MA. Among the 30 subjects evaluated after consuming these different oils, all varieties resulted in a more-favorable lipoprotein profile than the partially hydrogenated form, prompting the researchers to note that these oils are viable alternatives to trans fats. The soybean oils with enhanced fatty-acid profiles resulted in plasma lipid, lipoprotein, apoprotein, lipoprotein (a) and C-reactive protein concentrations similar to that of regular soybean oil. Some modifications, like reducing the saturated fat, showed a slight trend toward lowering LDL concentrations, compared to other nonhydrogenated soybean oils. But, the magnitude of difference was small among the oils tested.

As these newer types of transfree and trans-reduced oils become food-industry mainstays, there is potential for a significant shift in public health.

Kerry Neville, R.D., owner, KLMN Communications, Inc., Kirkland, WA, a company specializing in food, health and nutrition communications, provided this article on behalf of the United Soybean Board, Chesterfield, MO. She can be reached at [email protected]. 

Soybean Success

QUALISOY, a soy-industry collaborative initiative designed to help identify and commercialize soybean traits to optimize products for the food industry, has developed numerous soybean oils that do not require hydrogenation, but still have the same functionality and flavor characteristics the food industry requires.

Several brands of soybean oils with enhanced traits, including low-linolenic soybean oils, are already used by manufacturers. Adjusting the content of linolenic acid in the soybean to 3% or less gives oils with comparable functionality and low saturatesjust as partially hydrogenated oils do, but without the trans fats. Low-linolenic oils are particularly good options for snacks and foodservice frying since they provide improved flavor and oxidative stability, and shelf life exceeds that of nonhydrogenated oils.

The recent announcement by KFC Corporation, Louisville, KY, that the company plans to fry exclusively with low-linolenic soybean oil after April 2007 spurred Business Week, in its Jan. 3, 2007 issue, to suggest that supplies of the new low-linolenic oilseeds might be tight. However, in 2007, it is estimated that farmers will plant over 1.8 million acres of low-linolenic soybeans, a multifold increase from previous years.

Currently available low-linolenic soybeans include: Vistive from Monsanto, St. Louis; Pioneer® brand low-linolenic soybeans; and Ultra Low-Linolenic Soybeans from Iowa State University, Ames. The resulting oils include Advantage low-linolenic soybean oil (processed by Cargill, Inc., Minneapolis);

Vistive low-linolenic soybean oils (processed by ADM, Decatur, IL; Ag Processing Inc., Omaha, NE; CHS Inc., Inver Grove Heights, MN; and Zeeland Farm Services, Inc., Zeeland, MI); Treus low-linolenic soybean oil (developed in partnership by Bunge, St. Louis, and DuPont, Wilmington, DE); and Asoyia Ultra Low-Linolenic soybean oil.

Increased-oleic soybean oils designed for trans-free products in the baking industry are also in progress, and a limited quantity will be available in 2007 for testing.

Increased-oleic oils have 50% or greater levels of oleic acid while keeping linolenic acid at or below 3%. These new oils will offer superior flavor stability and resist oxidative breakdown, even under high heat. Fried products and other foods that undergo high heat can benefit from increasedoleic oils, because of superior resistance to flavor breakdown during processing and improved shelf life. Varieties with the highest levels of oleic acid offer heavy-duty extended-usage frying oils for foodservice and packaged-goods manufacturers. Increased-oleic varieties also have reduced linolenic-acid content.