Soybean Oil Innovations

By Richard Galloway, Contributing Editor

The soybean is an ancient crop native to eastern Asia with a history dating back 3,000 years. Today, the majority of the worlds soybeans are cultivated in the Americas, with the United States accounting for nearly one-third of the global supply.

No other oilseed can grow on such an expanse of latitudes as those in the United States, Brazil and Argentina. In North America, soybean oil represents 85% of the potential vegetable oil supply, with canola oil being its closest competitor in volume at 12%. Thus, soybean oil is widely available and provides a consistent supply year after year, regardless of crop growing conditions.

This wide availability is attractive to the food industry. Furthermore, soybean oil is marketable to health-conscious consumers. Soybean oil contains just 14% saturated fat, is rich in polyunsaturated fat at 54%, contains zero grams of trans fat in liquid form, is the primary source of omega-3s (in the form of alpha linolenic acid) in the U.S. diet and contains no cholesterol.

Soybean oil has a wide range of uses, from ink and coatings to bottled vegetable oil to sophisticated specialty shortening systems.

Refining the oil

Production of edible products from crude soybean oil requires some combination of refining steps, but first the oil must be extracted from the soybean. At least 99% of soybean oil in the United States is extracted through the solvent-extraction process, in which dehulled soybean flakes are bathed in petroleum-derived hexane. This process yields a product that is safe for human consumption. Processors remove the hexane from the oil and the flakes, and the hexane is recovered and reused in the same manner. Over 19 billion pounds of crude soybean oil is produced by this process every year, while less than 200 million pounds are produced by other processes, primarily by physically pressing the oil out of the soy flakes.

Once extracted and separated from the hexane solvent, the oil must be refined to remove off flavors and impurities that cause smoke when heated. This is accomplished by either caustic refining or physical refining. In the former process, the crude oil is mixed with a caustic chemical, which bonds with the primary impurities and forms a solution heavier than oil. A centrifuge separates the heavier material from the lighter, more-pure oil, which is removed. The oil is then filtered in a process referred to as bleaching," and finally is deodorized to remove volatile compounds using super-heated steam under a vacuum. The oil from this process is referred to as refined, bleached and deodorized, or RBD. The vast majority of edible-grade soybean oil produced in the United States uses the RBD process. In physical refining, the crude oil is degummed to remove as much of the phosphorous compounds as possible, then heated with super-hot steam under vacuum.

The next step

Further processing can give the finished edible oil characteristics needed for specific food applications. The most widely used process has historically been hydrogenation. This process injects hydrogen atoms into the triglyceride molecule to make the oil more resistant  to oxidation in high-heat applications and to retard oxidation of food products during extended shelf life. This process can also make semisolid and solid fat products such as vegetable shortening and flakes. Most methods of partially hydrogenating vegetable oils produce varying degrees of trans fatty acids. While trans fatty acids exist in dairy products and the fat in meat, the primary source of trans fat in the American diet has been partially hydrogenated vegetable oil.

Scientific studies completed in the 1990s found a positive correlation between consumption of relatively large amounts of trans fat and coronary heart disease. Consequently, much research has been done on replacements for vegetable oil products that contain higher volumes of trans fat. Incidentally, full hydrogenation does not produce trans fatty acids, and the hydrogenation process can be modified to produce very small quantities of trans fat. Precious metal catalysts can be employed, and time and temperature of the reaction can be modified to greatly reduce trans formation. Therefore, not all vegetable-oil hydrogenation produces trans fat.

A process that produces soybean oil products with similar characteristics to partially hydrogenated oil is interesterification, which modifies the fatty-acid-chain distribution on the glycerol molecule without producing trans fats. Food products with similar melting points and melting curves can be produced using this process instead of simple hydrogenation. Interesterified oils are used mainly in coating fats, margarine, sweets, shortening, pastry and specialty fats. Interesterification is an alternative to hydrogenation as a method of producing modified crystal formation in soybean oil.

The fractional crystallization of edible fats is another process that gives oil products the flexibility necessary for use in todays wide range of fat-containing products. This process separates the softer" oil portion from the harder" portion. Either fraction can be used to produce the desired soft or hard oil product. Generally, the fractions are blended with other oils, such as RBD soy, to produce the desired specifications.

Hydrogenated, interesterified and fractionated oils can be super-cooled and then plasticized for the desired crystal structure through controlled agitation to develop a more-rigid structure. This process is often referred to as votating," a generic offtake of the primary manufacturer of this type of processing equipment. These plasticized soybean oil products are used in margarine, shortening, cake icing and similar applications.

Breeding innovation

The soybean industry has been especially proactive in addressing concerns about trans fat. Besides innovative processing techniques and proprietary blending methodologies by processors, soybean breeders have been hard at work developing soybean varieties that inherently produce soybean oil with improved characteristics. The first such breeding innovation was the low-linolenic soybean. This soybean produces an oil that naturally contains 60% less linolenic fatty acid than traditional soybeans. Linolenic fatty acid is the most unstable of the polyunsaturates, and contributes to instability to heat application and erodes a foods shelf life potential. Low-linolenic soybean oil has successfully replaced some 750 million pounds of hydrogenated vegetable-oil products used primarily in frying and baking.

The next exciting product introduction by the soybean industry will be soybean oil high in oleic fatty acid. In contrast to linolenic fatty acid, oleic acid is the most stable of the unsaturated fats in edible oil. This high-oleic/reduced saturate soybean oil (20% reduction in saturated fats compared to commodity soy oil) will provide a high degree of oxidative stability in high-heat applications and will contribute to extremely long shelf lives for products containing this oil. The soybean industry and food companies envision that this oil will see high-volume uses in frying, baking and other applications characterized by high-heat processing, and in those needing a long shelf life.

Soybean oils clean, natural taste and nearly imperceptible aroma support and enhance the natural flavors of prepared foods. Whether used as a shortening for old-fashioned pie crust or blended with flavored vinegar for a new dressing, soybean oils neutral flavor lets the real taste of the food product come through. Adaptable to nearly every fat or oil application in the food industry, soybean oil works well with other ingredients, including other fats and oils, making it suitable for use in salad dressings, sauces and baked goods. Liquid soybean oil is used in 100% formulations for cooking oil and to create mayonnaise, salad dressings and sauces. Soybean oil also is found in breads, crackers, barbecue sauce and non-dairy creamers. It is used in prepared foods such as whipped toppings, potato chips, and battered and breaded snacks and vegetables. Compared to other vegetable oils, soybean oil has good emulsifying ability. Chefs and food companies have long practiced oil blending to reap the benefits of flavored oils paired with cost-saving ingredients such as soybean oil.

The soybean industrys dialogue with the food industry to meet the evolving consumer demand for healthy foods has resulted in trans fat being largely removed from the food supply, and reduction of saturated fat, as well. U.S. soybean farmers take great pride in growing one of the healthiest food crops in the world.

Since 1998, Richard Galloway has served as president of Galloway and Associates, LLC, a business consulting firm to the oilseed processing industry, its suppliers and customers. He is also the United Soybean Boards composition project leader, and the project leader for the Select Yield and Quality program. Galloway is the co-editor of the American Oilseed Chemists Society (AOCS) monograph, Soybeans: Chemistry, Production, Processing and Utilization.