Something new under the sun(flower)

Something remarkable has happened to sunflowers. They have sped through hundreds of years of evolution in just a few generations. They have developed traits that make their oil less likely to go rancid, better for frying, and healthier to consume than the alternatives. The is the story of high oleic sunflower oil.

Bottle of high oleic sunflower oil and sunflower flowers with seeds on a wooden table
High oleic sunflower oil

Fat is like a three legged octopus

To appreciate the transformation in sunflower oil we need some background. Triglyceride molecules, the molecules in edible oils and fats, are a bit like three armed octopuses  (tri-puses?). The three arms are chains of carbon atoms and are rarely identical. They can vary in length from just a couple of carbons to more than 20. The legs can be straight, or kinked, or really kinked!

The behavior of the fat – whether it is solid or liquid at room temperature, whether it stays fresh or goes quickly rancid, how it feels in your mouth or provides texture to your cookies – this all depends on the shape and length of the fatty-acid arms. 

The triglycerides in a solid fat like lard or palm oil have fairly long fatty acid arms that can easily straighten and stack. These are the saturated fats (saturated with what?)

Tessellating octopuses provide a model for crystallization of triglycerides in oils and fats. Copyright:
Cartoon showing stacking octopuses with their arms extended and able to tessellate.

The triglycerides in liquid vegetable oil like olive oil or canola have fatty acids arms that are very varied and kinked. It’s difficult to stack and organize the many different shapes. They can be monounsaturated (one kink) or polyunsaturated (more than one). If you imagine a crowd of octopuses swimming together twisting their arms around each other you have a pretty good model of liquid oil.

Fatty acids. Arachidic, stearic and palmitic are saturated. Erucic and oleic are monounsaturated – one kink. Arachidonic, linoleic and linolenic are polyunsaturated – several kinks.

It is healthy to be kinked

Doctors and dieticians advise us to limit our dietary intake of the easily straightened and easily stacked saturated fats.

Switching from saturated to monounsaturated fatty acids may reduce heart disease. The monounsaturated fats in olive oil may help make the Mediterranean diet healthy.

Polyunsaturated fats are not just healthier, some are essential! There is a burgeoning industry in polyunsaturated fatty acid supplements.

Unfortunately, after a relatively short but chaotic life, oils rich in polyunsaturated fatty acids in foods succumb to chemical degradation and are broken down. They are particularly unstable if they are heated (used for frying, for example). It’s not good to consume rancid oils – there are reasons why you have evolved to find that smell unpleasant!

Nutrition facts label for almonds - including the amounts of saturated, monounsaturated and polyunsaturated fat
A US nutrition label.  The amounts of saturated fat, trans fat and cholesterol must be reported. Providing information about the amount of unsaturated fats is voluntary.

Oily challenge

The challenge that chefs and food manufacturers face is that consumers love fried food. Shelf life is important too. Foods need to stay fresh in the store and as they wait in our homes to be eaten. Fully saturated fats and oils are unhealthy, and polyunsaturated ones are unstable.

The ideal solution for frying and a long shelf life is oil with almost all monounsaturated fatty acids (arms). But unfortunately plants had not evolved to produce that kind of oil.

Comparison of dietary fats showing the relative amounts of oleic (monosaturated) fat in each
Safflower oil has the highest percentage of monounsaturated oleic acid, but also has significant amounts of the more unstable polyunsaturated fat

The first approach to meet this challenge was, frankly, a disaster. It seemed like a good idea to partially hydrogenate vegetable oil to increase the saturation, chemically changing some of the polyunsaturated fat to monounsaturated fat to make it more stable. In practice the chemical treatment created trans-fats.

It turned out to be much better to work with nature – directing the process of evolution to create oil that is better for packaged baked goods and for all types of frying.

So what is new with sunflowers? High oleic oil!

Now available on supermarket shelves: high oleic sunflower oil – a healthy replacement for partially hydrogenated oils (which have now been banned). It is slow to degrade when heated to high temperatures, which makes it ideal to use for baking or frying. You will also find it in all kinds of baked goods – particularly those with a long shelf life.

High oleic refers the amount of a specific monounsaturated fatty acid 18 carbons long with one kink at carbon number 9. To be classified as high oleic, an oil must have over 70% oleic acid.

In 2018 the FDA authorized a qualified health claim relating consumption high oleic oils to a reduced risk of heart disease:

“Supportive but not conclusive scientific evidence suggests that daily consumption of about 1½ tablespoons (20 grams) of oils containing high levels of oleic acid, may reduce the risk of coronary heart disease. To achieve this possible benefit, oleic acid-containing oils should replace fats and oils higher in saturated fat and not increase the total number of calories you eat in a day.”

The global market for high oleic oil is expected to grow 4% annually from 2021-2026 and reach 290 billion USD by 2026.

So how did plant breeders create sunflowers that yield high oleic oil?

Speeding breeding

We all learnt about Mendel in high school. He discovered the processes of evolution as he studied yellow and green pea variants and watched these traits passing down the generations.  

New traits arise in nature as random changes occur in DNA. In the overwhelming majority of cases these changes lead to no change, or to changes that are unfavorable. But occasionally the change is an improvement. The plant with that new trait is better, stronger, more able to propagate.

This process is slow. As habitats have changed over time plants have slowly evolved to meet new threats or capitalize on new food sources. But mankind is changing really fast. In just a few generations we have completely reinvented the way we eat. We needed the plants to catch up.

One solution to this is mutagenesis. Plant breeders accelerated the rate of new trait development in sunflowers – encouraging more random changes in the DNA – using chemical treatment or irradiation (note, this is completely different to transgenesis – these are not GMO plants). Following in Mendel’s footsteps breeders selectively breed the sunflowers with more monosaturated fatty acids in their oil.

Chemical mutagenesis of seeds in 1970s Russia eventually led to the first sunflowers that produced high-oleic oils. In 2016, a new sunflower originating from X-ray mutagenesis emerged which has up to 92% monosaturated oleic acid. These new oils are indeed healthier. Something new under the sun!

They are also excellent feedstocks for the chemical industry. Potential replacement for fossil fuels as the world moves towards more sustainable plant-based materials. But that is a story for another day.

More information

  • Saturated with what? Saturated with hydrogens!  Every carbon had the maximum possible number of hydrogens. Here is more about the chemistry of lipids (fat) (Lumen Introduction to Chemistry website)
  • To learn much more about the biochemistry of high oleic sunflowers, and the history of their development read chapter 5 in “High Oleic Oils, Development, Properties, and Uses”, written by Nurhan Turgut Dunford, EnriqueMartínez-Force and Joaquín J.Salas and published by AOCS press in 2022. Purchase this chapter.
  • Remember Mendel’s peas? Here is a cute Ted-ed video. (YouTube)

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