Today’s consumer seeks to understand where their food is grown or raised and how it’s processed. While this heightened interest in our food supply is exciting to those of us working in food and nutrition, it requires that we communicate on core science principles and varying views of a topic in addition to addressing the nutrition.
One such case in point is oil processing. Expeller-pressing, essentially squeezing the seeds and beans for canola, olive and soybean oils, is the first step in processing. The oil extraction process can stop here, and consumers can purchase expeller-pressed oils from local grocers. Expeller-pressed oils are sometimes considered more “natural” in light of how they are processed, but when viewed through a sustainability lens, the picture is a bit different. This type of processing leaves behind 6-14% of the available oil in the seeds and beans.
Oil extraction can also be accomplished through the use of solvents like hexane, a step which occurs after mechanical pressing. Chemical extraction leaves behind less than 1% of the oil, making it a more sustainable process in the sense that it extracts the highest amount of edible oil from the plants. Consider canola as an example. If mechanical or expeller-pressed instead of chemical extraction were used more than 242 million pounds of oil would be left behind (based on USDA production data, 2014). An additional 300,000 acres of canola would need to be planted to make up for this lost amount. More efficient processes such as chemical extraction also lead to lower food costs, an important topic to consumers.
Communication on core science principles comes into play when you hear that the Environmental Protection Agency (EPA) includes hexane on a list of environment pollutants and that the Center for Disease Control and Prevention (CDC) indicates hexane is a neurotoxin. If you look into the details of the EPA and CDC information on hexane, however, you will realize these health impacts are related to environmental overexposure to hexane, with repeated exposures to large amounts over long periods of time. Inhalation is the concern, primarily by those who work in the various industries where hexane is used. Estimates suggest hexane intake from food sources is only 1.95% of the estimated daily intake from inhalation and other environmental exposures. The National Institute of Occupational Safety and Health has recommended exposure limits for those who work with hexane. The EPA has had controls in place for hexane since 2001.
It’s also worth noting that hexane is recovered and reused in the oil-extraction process because of its high cost. During oil processing, crushed seeds are mixed with hexane and the oil dissolves into it. The solution is then separated from the seeds and oil and heated to evaporate virtually all the hexane residue. In fact, the EPA notes that only very small quantities (no more than 0.2 percent by volume of oil) of solvent are present after it is recovered by evaporators. Additionally, this process is so effective, 98 to 99 percent is recycled for future use.
From the nutrition vantage point, canola and other oils provide the mono– and poly-unsaturated fats the Dietary Guidelines for Americans recommend consumer use to replace saturated fats. Consumers can choose expeller- or solvent-extracted oils knowing both are safe for consumption and provide nutritional benefits.
As we communicate the details of food production, it’s essential to teach consumers to look beyond the surface information as well as to consider multiple points about the topic as this example of oil processing shows.
- Hexane Extraction in Soyfood Processing, Barry Swanson.
- Canola oil: Supply and disappearance, U.S., 1991/92-2014/15. USDA, Economic Research Service estimates and U.S. Census Bureau, Fats and Oils: Production, Consumption and Stocks and USDA, Foreign Agricultural Service, Global Agricultural Trade System and Milling & Baking News.
- Compilation Of Air Pollutant Emission Factors, Volume 1: Stationary Point And Area Sources, 5th Edition. US Environmental Protection Agency. Vegetable
- A Review of Environmental Assessments of Biodiesel Displacing Fossil Diesel. The Canola Council of Canada & Auto21 Network of Centres of Excellence.