The benefits of omega-3 fatty acids have been known for many years; however, their incorporation into foods, such as those with much surface area, has been challenging, due to oxidation issues.
Omega-9 and omega-3 fats have received significant consumer and industry interest, because they are perceived as being more healthful than trans fats, saturated fats and omega-6 unsaturated fats. Relative to the red meat-based Western diet, which is comparatively high in saturated fats and omega-6 unsaturated fats, the Mediterranean diet is considered to be “heart-healthy,” in that it may reduce LDL cholesterol.
Olive oil is often used in preparation of foods associated with the Mediterranean diet. Olive oil and other oils high in omega-9s, such as canola and high-oleic sunflower, are low in saturated fats and rich in oleic acid (>60% of the total fatty acids), the major omega-9 lipid in the diet. Canola oil also can contain up to 10% linolenic acid (LNA), the major plant-based omega-3 lipid. Canola, soybean and flaxseed oils all contain LNA, with flaxseed oil comprised of some 50% LNA. Additionally, many consumers are aware that diets containing fish, such as salmon and tuna, provide a good source of long-chain omega-3 fatty acids, such as EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). These lipids are positively associated with many health benefits, such as improved cardiovascular health, immune function, maternal/natal nutrition and neurological function.
Calling Out FDA-approved Health Claims
Qualified health claims can be made for certain food products that use omega-9 and omega-3 oils. For example, the FDA has issued the following qualified claim for olive oil:
“Limited and not conclusive scientific evidence suggests that eating about 2tbsp (23g) of olive oil daily may reduce the risk of coronary heart disease due to the monounsaturated fat in olive oil. To achieve this possible benefit, olive 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 [name of food] contains [x]g of olive oil.” For canola oil, the message is this: “Limited and not conclusive scientific evidence suggests that eating about 1½-tbsps (19g) 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]g of canola oil.” To be able to make this claim, a food product must meet the FDA requirements of “low fat,” “low saturated fat” and “low cholesterol,” as defined in 21 CFR 101.62(d)(2) of theFederal Register.
A similar qualified health claim has been issued specifically for the omega-3 fatty acids, EPA and DHA: “Supportive but not conclusive research shows that consumption of EPA and DHA omega-3 fatty acids may reduce the risk of coronary heart disease. One serving of [name of food] provides [x]g of EPA and DHA omega-3 fatty acids. [See nutrition information for total fat, saturated fat and cholesterol content.]”
There has been much discussion around being able to make “good source” and “excellent source” claims for the omega-3 lipids. Unlike vitamins and minerals, the FDA has not yet established a recommended daily intake for these lipids. However, the FDA is allowing labeling that has been used in the past to continue to be used, until a ruling on the Recommended Dietary Intake (RDI) is set. Companies can place certain claims on their packaging, such as “An Excellent Source of Omega-3 EPA and DHA,” “High in Omega-3 EPA and DHA” or “Rich in Omega-3 EPA and DHA.” Products must contain a combined total of at least 32mg of EPA and DHA (per serving) to qualify for this claim. Some 32mg of EPA and DHA represents 20% of the daily value levels for EPA and DHA of the 160mg per day recommended by the Institute of Medicine. The claim needs to include the statement that the product “contains [x]mg of EPA and DHA per serving, which is [x]% of the 160mg daily value for a combination of EPA and DHA.”
Advances in Use of Omega-9s and Omega-3s
Because of the health implications, food scientists have been interested in incorporating these lipids into many food products. However, both omega-9- and omega-3-based lipids have inherent issues that make their adoption into mainstream food products challenging.
Oils containing high levels of omega-9 lipids, such as canola and olive oils, work well as general use food oils because of their high degree of stability to oxidative rancidity. Furthermore, specific genetic variants of sunflower and canola oils have been developed that have much higher concentrations of oleic acid (>80%) than the native varieties. These high-oleic varieties of canola and sunflower oils have enhanced stability. (See chart “Fatty Acid Composition of Traditional and High-oleic Seed Oils.”) Also, manufacturers of value-added fats and oils have expended much effort in developing high-omega-9 fats (primarily canola) that work well as functional shortenings for the baking industry; they are an alternative to partially hydrogenated trans fat-containing shortenings or to highly saturated shortenings (such as palm).
The primary issue to making these fats work in functional shortening systems is the lack of crystalline fat at room temperature. The solution has been to blend fully hydrogenated fractions with the fractions rich in oleic acid to provide appropriate crystalline function; this provides good eating qualities in baked products, such as breads, crackers and pastries. The saturated fraction may come from a variety of sources, such as fully hydrogenated soy oil, palm stearine or non-GMO, high-stearate soybeans.
In contrast to the stability of the omega-9-containing oils, oils rich in omega-3 fatty acids are inherently susceptible to oxidative rancidity. Relative to oleic acid, the oxidation rate of LNA is about 100 times greater, while the long-chain PUFAs (LC-PUFA), EPA and DHA, are some 200 times greater (Gunstone, FD.Structured & Modified Lipids. 2001). While the benefits of omega-3 fatty acids have been known for many years, their incorporation into foods has been slow, because of the traditionally very limited shelflife of the products that contain them. Therefore, much of the attention for the use of these lipids has focused on identifying methods to stabilize them in application.
Vendors of high-quality EPA and DHA understand that clean-up of the feedstock oil for removal of pro-oxidants and hydroperoxides, along with incorporating antioxidants (such as TBHQ, tocopherols, ascorbyl palmitate and citric acid), are critical to providing shelflife to these highly unsaturated oils. These stabilized LC-PUFA oils then can be used in a variety of products.
One commercially available omega-3 oil, which contains about 35% DHA, is currently being used in a host of food products. Many are refrigerated, such as yogurt, milk and cheese. However, the oil also is being incorporated into salad and general purpose cooking oils, such as Pompeian OlivExtra Omega-3 DHA and Crisco Puritan Canola Oil with Omega-3 DHA. These oils are leveraging the generally healthful connotation of omega-9 rich olive and canola oils as the basis for delivering the specific health benefits of the LC-PUFA, DHA. Both oils use tocopherols as antioxidants; Crisco also uses ascorbyl palmitate and states a two-year shelflife.
Still, there are many food products, such as dry beverages, where dispersibility of these oils is an issue. Also, the use of LC-PUFAs in high surface area products, like cereals and granola bars, has proven challenging to long shelflife, due to oxidation issues. Oil encapsulation has been one strategy to address these shelflife challenges. One supplier of fish oils has patented a gelatin-based coacervation encapsulation technology (USPTO 6,974,592) that turns the oil into a free-flowing powder and stabilizes the oil in a matrix that excludes oxygen. Another vendor has developed a protein encapsulation technology for the same purpose. Also, General Mills Inc. has patented a protein encapsulation process (USPTO 7,431,986). The key to the success of any of these encapsulation technologies in stabilizing the finished product is to remove oxygen from the system and form a complete shell around the oil droplet. Furthermore, residual surface oil on the capsule must be scrupulously removed to avoid surface oxidation.
LC-PUFA by Way of Transgenic Crops
While the positive health implications of consuming the long-chain polyunsaturated fatty acids EPA and DHA (LC-PUFA) have become well-established, supplying these fatty acids to the population has proven challenging. There are several ingredient companies offering purified fish oils that contain up to 40% EPA and DHA. Several other ingredient suppliers produce very clean oils from algal sources that contain over 35% DHA. However, the dwindling supply of fish rich in LC-PUFA and the costly fermentation process needed for algal oil production ultimately may put these sources out of reach for LC-PUFA consumption by the general population. The most straightforward method is to produce the fatty acids in a farmed oilseed crop, such as soybeans or flax. However, since linolenic acid is very sparingly converted to the long-chain polyunsaturated fatty acids (LC-PUFA), plant researchers have been working to develop oilseeds that can supply LC-PUFAde novo. Agronomists from plant science companies have been working on development of sustainable crops that can fill the need for these fatty acids. Professor Ian Graham (Department of Biology, University of York, U.K.) reported at the 2008 meeting of the International Society for the Study of Fatty Acids and Lipids (ISSFAL) that one company has developed a transgenic soybean, currently in plant breeding trials, that can produce as much as 40% EPA. Another international firm has shown proof of concept for production of EPA and DHA in flax. These oilseeds are at least two years away from production, however.
On a slightly different approach, one biotechnology company, in collaboration with an ingredient vendor, has developed a transgenic soybean that is rich in stearidonic acid (SDA) and is currently ready for production. SDA has one additional double bond, compared to LNA. This “desaturation” of LNA to SDA in the plant addresses the rate-limiting step. [Editor’s note: The rate-limiting step refers to the slowest step in the metabolic process, by which the shorter chain omega-3 (18:3n3 or linolenic acid) obtained from plants is eventually converted to very long-chain omega-3s required by the body.] Thus, SDA provides a substrate that can be converted in the body to EPA. (See chart “Omega-3 Desaturation and Elongation Pathway.”)
Thus, while the consumption of SDA is less effective at increasing circulating EPA stores in the body than consumption of EPA directly, SDA is several times more effective at increasing circulating EPA levels compared to linolenic acid (James, et al. 2003.Amer. J. Clin. Nutr. 77:1140-1145). The biotechnology company has stated it has chosen this route over oilseeds rich in EPA, because the company has determined that oil containing SDA is more stable to oxidation and has better flavor than oil rich in EPA. Richard Wilkes, director of food applications with the biotechnology company, states that SDA soybeans can be grown and processed like regular soybeans for oil production. Oil from these soybeans contains about 20% SDA and, while the primary market for these beans would be for human food applications, he also sees opportunities for use in aquaculture, animal feed and pet food, and specific industrial uses. The company has conducted extensive crop testing; SDA soybeans are a northern crop, which has shown a similar yield over five years’ production to control soybeans. Consumers detected no difference in flavor during the shelflife of food products made with SDA soybean flour or oil, compared to control soy-containing products. While SDA soybean oil is more stable against oxidation than fish and algal oils, it still requires stabilization with antioxidants, such as tocopherols or TBHQ.
More Functionality, More Possibilities
There is a bright future for these healthful oil options. The industry has done a good job of improving the functionality of oleic acid-rich oils, such as canola, sunflower and olive oil, for uses beyond general food use, such as in structured shortenings for the baking industry. The shelflife has greatly improved for the omega-3 LC-PUFA oils through more thorough clean-up, antioxidants and encapsulation. The transgenic plant options for LC-PUFA production may greatly increase the availability and reduce the cost of these lipids. Advances in these functional lipids will prove very useful for the development of more healthful new food products. pf
Mark Black is a principal scientist at Merlin Development, which provides high-quality, cost-effective research and development services. Merlin specializes in all technical aspects of food product development, from concept through commercialization, including prototype development, formulation, scale-up, quality system design and production start-up. Black can be contacted at 763-475-0224 or MarkBlack@merlindev.com, www.merlindevelopment.com.
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