Soybean Breeding Research for Healthier Oils at Iowa State University
1% Linolenic Soybean Oil
Research on altered linolenic acid content of soybean oil began at Iowa State University in 1968. Earl Hammond of the Department of Food Science and Human Nutrition visited Unilever in the Netherlands and learned that they were interested in obtaining soybean oil with reduced linolenic acid to avoid the use of hydrogenated oil in their food products. Unilever agreed to fund research at Iowa State University to initiate a breeding program for reduced linolenic acid. Hammond and Walter Fehr, a soybean breeder in the Department of Agronomy, began a collaboration that led to the development of 1% linolenic acid soybean oil.
The research team developed by conventional breeding methods three genes that individually reduce linolenic acid. The genes are designated fan1(A5), fan2, and fan3. By combining the three independent genes, the linolenic acid of the oil was reduced to 1%.
To develop commercial varieties, lines with 1% linolenic were crossed to the best conventional varieties available. Hundreds of offspring from the crosses were self-pollinated for several generations to obtain lines that would be true-breeding for 1% linolenic acid and for important agronomic traits, including seed yield and standability. The lines were evaluated for several years in field tests throughout the Midwest for important agronomic and seed traits, and two superior ones were identified, IA2064 and IA3017. Commercial acreage of the two varieties was first grown in 2004.
Although there was some concern before 1970 about the possible negative health consequences of trans-fatty acids in the human diet, it was not until July 9, 2003, that the U.S. Food and Drug Administration (FDA) announced that it would require the labeling of all food products for their trans-fat content beginning January 1, 2006. As a result of the new federal regulation, the food industry in the United States has been actively pursuing alternatives to hydrogenated oils so that their products can be labeled as containing 0 grams (g) of trans-fat. Soybean oil with reduced linolenic acid has been adopted as one of the alternatives to hydrogenated oil.
Production of 1% linolenic soybean oil is expected to grow in the future as the food industry decreases its use of hydrogenated oils. Most public and private soybean breeders in the U.S. are in the process of developing cultivars with reduced linolenic acid.
To help meet the need for soybean oils that do not require hydrogenation, the 1% linolenic acid research team at Iowa State University is continuing its work to bring improved varieties to the public. For the 2009 crop year, the available non-GMO varieties are included in the Varieties Performance section of this Web site. In addition, two new Roundup Ready varieties will be available.
Low-Saturated-Fat Soybean Oil
In the United States, all food products must be labeled for their total content of saturated fatty acids because of their impact on cardiovascular health. The American Heart Association recommends that the intake of saturated fat be limited to 7 to 10% or less of the total calories consumed each day (www.americanheart.org). A food product cannot be advertised as “low in saturated fat” unless it contains 1 gram (g) or less of saturated fat per serving. For a liquid soybean oil, 1g in a 14g (one tablespoon) serving is equivalent to 7.1%. When rounding is considered, a product can be labeled as containing 1g per serving if its content of saturated fatty acids is 1.25g or less (8.9%).
The saturated fatty acids in conventional soybean oil consist of about 12% palmitic, about 4.0% stearic, and about 1.0% of other saturated fatty acids. Low-saturate soybean oil is possible due to major genes that have been developed to reduce the palmitate content. The first major gene reported for reduced palmitate was fap1 developed by the USDA-ARS and Purdue University in 1988. A second gene, fap3, was developed by Iowa State University. By combining fap1 and fap3, the palmitic acid content was reduced to about 4%. This reduced level of palmitate made it possible to initiate a cultivar development program to produce a soybean oil that could be labeled as low in saturated fatty acids.
The first low-saturate cultivar that was grown commercially in 1996 was developed jointly by Iowa State University and Pioneer Hi-Bred International, Inc. (a DuPont company). The low-saturate oil from the crop was sold for the first time in the fall of 1997. It was sold in grocery stores in the midwestern U.S. and was distributed to schools nationally through the U.S. Department of Agriculture’s National School Lunch Program and School Breakfast Program as a means of lowering the saturated fat content of the meals. With only 1g of saturated fat per tablespoon (14g), the oil matches the saturated fat content of canola oil and reduces by half the saturated fat found in traditional soybeans.
The new non-GMO ISU varieties available for the 2009 crop are included in the Varieties Performance section of this Web site.
Mid-Oleic / 1% Linolenic Soybean Oil
Conventional soybean oil contains about 25% oleic fatty acid, the same monounsaturated fatty acid found in olive oil. Oleic acid has greater oxidative stability and a longer shelf life than linolenic acid. To take advantage of the oxidative stability of oleic acid, research has been conducted to increase its content in soybean oil for some food applications.
A goal of Iowa State University’s soybean breeding program has been to develop a cultivar that would consistently produce an oil with greater than 50% oleic acid, called mid-oleic. The Iowa State research team wanted to transfer by conventional breeding the genes controlling the elevated oleic acid trait into their varieties with 1% linolenic acid that are grown commercially in the Midwest.
In 2002, Walter Fehr and his research team obtained from scientists at Saga University in Japan a soybean line with about 50% oleic acid, compared with about 28% in conventional soybeans. The Japanese soybean line M23 was developed by conventional breeding, but it could not be grown in Iowa because it did not mature before frost. Multiple breeding cycles were conducted to develop varieties that matured in Iowa and had the combination of mid-oleic and 1% linolenic acid.
In the summer of 2005, the Iowa State researchers planted in Ames, Iowa, seed with >50% oleic acid and 1% linolenic acid from the third breeding cycle. All of the lines matured before frost. One line was increased in Argentina during the winter of 2005-2006 to obtain additional seed for processing. The seed grown in Ames and the same quantity from Argentina were blended and processed into refined oil by the POS Pilot Plant Corporation in Saskatoon, Saskatchewan, during June 2006. The fatty acid composition of the refined oil was 9.3% palmitate, 5.4% stearate, 53.3% oleate, 31.1% linoleate, and 1.0% linolenate.
During the summer of 2006, the mid-oleic/1% linolenic oil was sent to more than 30 food companies to evaluate its characteristics in comparison with a normal oleic/1% linolenic oil. The oxidative stability for the mid-oleic/1% linolenic oil was more than twice as long as the normal oleic/1% linolenic oil. Based on the interest in the new oil by food companies, there has been production of the oil in 2007 and 2008 with ISU varieties. For the 2009 crop year, the available non-GMO varieties are included in the Varieties Performance section of this Web site.
Soybean breeding research at Iowa State University is supported by the Hatch Act, State of Iowa, Iowa Soybean Association, Raymond F. Baker Center for Plant Breeding, and the United Soybean Board.