Let us look at the best oils for cooking
There are several things to consider when choosing the best oils for cooking but firstly it is important to understand what fat is and the difference between saturated and unsaturated fats.
Fats and oils consist of glycerol which is a sugar alcohol and 3 fatty acids. We are going to discuss both glycerol and fatty acids and their impact on the choice of the best oils for cooking.
Fatty acids can be saturated or unsaturated. For example, 87% of the fatty acids in coconut oil are saturated whereas only 21% of the fatty acids in avocado oil are saturated.
Why is this important?
Because the chemical structure of saturated fats is different from unsaturated fats. There are no double bonds within a saturated fat and it is the double bonds that make the structures unstable when exposed to oxygen and hence prone to oxidation.
You may have heard of monounsaturated fats and polyunsaturated fats. Monounsaturated fats have just one double bond and polyunsaturated fats can have multiple double bonds. The more double bonds, the more unstable the structure.
When the double bonds in an unsaturated fat break down, chemically unstable free radicals known as oxidants are produced. These oxidants cause cellular damage, inflammation and the development of chronic disease. Something we want to avoid!
Antioxidants are able to overcome oxidants hence protecting cells from damage. The body produces its own antioxidants and they are also an important part of our diets in the form of nutrients such as vitamin C, vitamin E, zinc and selenium.
We are exposed to oxidants via normal metabolism as well as things like environmental factors and stress. Therefore it is advisable to avoid oxidant formation that is under our control, such as through the use of cooking oils.
Heat speeds up oxidation and that is why we are concerned about the unsaturated content of our cooking oils. Remember that it is the unsaturated fats that are oxidised due to their double bonds. Therefore, the higher the saturated fat content the more stable the structure and the less prone to oxidation a fat or oil is.
This is what makes coconut oil a good choice of oil due to its 87% saturated fat content. Compare this for example to walnut oil that has 63% polyunsaturated fat content. These unsaturated fats in walnut oil are highly susceptible to oxidation and this speeds up with exposure to heat. Walnut oil is, therefore, best used cold on salads and for dressings rather than for cooking.
If your cooking requires liquid oil rather than solid fat, then olive oil is a good choice. This is because it contains 14% saturated fats, 73% monounsaturated fats, with the remainder 13% being polyunsaturated. So although the saturated fat content is lower than coconut oil the unsaturated fats are primarily monounsaturated containing just one double bond.
Therefore olive oil is less prone to oxidation than for example sunflower oil that contains over 30% polyunsaturated fats. In addition, olive oil contains polyphenols that are antioxidants aiding in overcoming any oxidative damage.
There is often confusion around the relevance of smoke points of oils. At the smoke point, the glycerol molecule we talked about earlier becomes detached from the fatty acid molecules leaving ‘free glycerol’ and ‘free fatty acids. In other words, they are no longer bound together.
This leaves the glycerol exposed and able to be broken down into acrolein that causes health risks from inhalation and ruins the taste of the food. Therefore if you ever forget about your oil and it begins to smoke, throw it away and start again! The smoke points of oils are determined by the amount of free fatty acids they contain.
The processing of oils is important. Free fatty acids are also created as the source of oils begin to decompose. For example, when coconuts, olives, avocados, nuts, seeds etc are harvested, decomposition begins releasing fatty acids from glycerol.
If the fruits and nuts etc are left to decompose before being pressed they will have a lower smoke point due to the higher content of free glycerol and fatty acids.
Some oils are refined to remove this free fatty acid and free glycerol content that occurs after harvesting. This is why the smoke point of virgin coconut oil is 177°C whilst refined coconut oil has a smoke point of 230°C. Therefore choose oils that are suitable for the temperature of your cooking.
Another consideration in choosing oils is their omega 6 and omega 3 fatty acid content. Omega 6 fatty acids can result in inflammation whereas omega 3 fatty acids are anti-inflammatory. Our diets contain a high level of inflammatory omega 6 fatty acids through intake of oils and processed foods containing these omega 6 dense oils.
Inflammation is a driver of chronic illness. It is therefore advisable to reduce the level of omega 6 fatty acids in the diet whilst ensuring there is a good intake of omega 3.
When looking at oils it is useful to look at their ratio of omega 6 to omega 3 compositions. Sunflower oil has a ratio of omega 6 to omega 3 of 30:1, palm oil 46:1, corn oil 50:1 and peanut 32:1. Compare this to the preferential profiles of olive oil with a ratio of 12:1, coconut oil of 18:1 and butter of 14:1.
Questions are often asked about avocado oil because it has a ratio of 13:1, a high smoke point and is 70% monounsaturated. Remembering that the smoke point is relevant to the glycerol decomposition and not the oxidation of the fatty acids, coconut oil would still be the oil of choice at high temperatures with its 87% saturated fat content.
Avocado could however be a reasonable choice for medium temperature cooking.
Canola oil or rapeseed oil is another oil often discussed. Although it has a good omega 6:3 profile at 4:1 it contains 30% polyunsaturated acids and is therefore highly prone to oxidation as well as being highly processed itself.
Butter is 52% saturated and has an omega 6:3 ratio of 14:1. Its smoke point however is 150°C so at very high temperatures the taste of food would be ruined as acrolein is produced. Ghee which is a butter with milk solids removed has a smoke point of 252°C so can be used for high-temperature cooking.
Coming back to olive oil, high-quality extra virgin olive oil actually has a relatively high smoke point of around 190°C to 220°C. This together with its antioxidant content of polyphenols and vitamin E that helps prevent oxidation, its omega 6:3 ratio of 12:1 and monounsaturated fat rather than polyunsaturated fat content makes it a good all-round oil for cooking.
So in summary, at high-temperature, the best oils for cooking are non-virgin coconut oil or ghee and for medium temperatures olive oil or avocado oil. Extra-virgin olive oil is the better choice of olive oil. Always purchase the highest quality oils that you can afford from reliable suppliers.
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