So let’s knock this on it’s head once and for all. Yes you can cook and indeed should cook with extra virgin olive oil. Here’s why.
A quick chemistry lesson
OK this is the science bit – you can skip it if you like and head straight to the conclusion, but to really bust this myth I need to convince you fully.
Oils are made up predominantly of fats called triglycerides. These are made up of three (hence the ‘tri’) fatty acids attached to a compound called glycerol.
Oils also contain a very small number of free fatty acids – in other words fatty acids that are not attached to glycerol and are ‘floating’ on their own. The level of free fatty acids varies between oils and varies with the quality of the oil. This is important, as we’ll discover.
The fatty acids present in the oil, either as part of a triglyceride or free, can be saturated, monounsaturated or polyunsaturated. These names come from the chemical structure of the fats and the number of what are called ‘double bonds’. Saturated fats have no double bonds, monounsaturated fats have one, and polyunsaturated fats, as the name suggests, have many.
You don’t need to know what these are – school chemistry may be a distant memory – but suffice to say that they are important because a double bond is the part of the fat that is prone to damage.
Damage (technically called oxidative damage) to double bonds is what creates trans fats – the most damaging to our health – and what makes a fat turn rancid. A rancid fat will not taste good, but it also contains potentially harmful compounds.
This damage to oils can happen with exposure to light, to air and to heat, especially very high heat and prolonged heat. This is why you are best to store any oil in a dark, cool pantry and to use it up before the best before date to ensure freshness. It is also why we need to take care with our choice of oils when cooking.
"This damage to oils can happen with exposure to light, to air and to heat, especially very high heat and prolonged heat."
The smoke point is a term used to describe the temperature at which you’ll see a bluish smoke rising continuously from the oil. (Note that extra virgin olive oil is a natural product and so contains a little water. This means that when you heat it in the pan you’ll often see steam rising well before the oil reaches its smoke point – don’t confuse this and think you are damaging the oil.) Heating the oil above its smoke point increases the likelihood of oxidative damage and the creation of potentially harmful compounds.
Since polyunsaturated fats have lots of double bonds these fats are the most fragile and prone to damage. In contrast, saturated fats with no double bonds are extremely stable, while monounsaturated fats with only double bond are also highly resistant to oxidative damage.
"Polyunsaturated fats have lots of double bonds these fats are the most fragile and prone to damage."
Free fatty acids are also more prone to oxidative damage and so oils with higher levels of free fatty acids are also more fragile, especially during cooking.
The smoke point is usually given as the definitive guide as to whether a type of oil can be used for cooking. However, it’s not the only important factor and it varies, even amongst one type of oil. This is where much of the confusion has come from.
Extra virgin olive oil
Looking just at olive oils you’ll find different smoke points given, depending on the source of the information. That’s because it depends on the quality of the oil, how fresh it is, how it has been stored, the levels of free fatty acids and the levels of protective antioxidants.
So here is the crux of the matter. Extra virgin olive oil has three key qualities that make it an excellent cooking oil: it contains predominantly stable monounsaturated fatty acids, it has a low level of free fatty acids and it has a high level of protective antioxidants.
If we look at the smoke points of extra virgin olive oils, these range from about 190-220°C. The best quality oils, including Cobram Estate extra virgin olive oils, come in at the higher end of the range.
How does this relate to cooking? Well sautéing on the stove equates to a temperature of around 120°C, deep-frying is usually in the range 160-180°C and roasting in the oven 180°C. It is not often you would cook at any temperature higher than this.
Importantly there is no further advantage to using an oil or fat with an even higher smoke point. In other words, if you are roasting your veggies in the oven at 180°C, your extra virgin olive oil is perfect as it has a smoke point above this. Choosing an oil with a smoke point higher than 220°C is not any safer.
"Extra virgin olive oil has three key qualities that make it an excellent cooking oil: it contains predominantly stable monounsaturated fatty acids, it has a low level of free fatty acids and it has a high level of protective antioxidants"
Why we should cook with extra virgin olive oil
Several good studies have confirmed the stability of extra virgin olive oil during cooking. Importantly these studies have really pushed the boat out to test the point at which various oils will break down. They repeatedly heat the oils, heat them for long periods of time and take them up to extremely high temperatures.
"Several good studies have confirmed the stability of extra virgin olive oil during cooking."
These conditions would almost never happen in home cooking so the fact that extra virgin olive oil stands up consistently well in these tests really does confirm the safety of using the oil at home. The same is not true of oils high in polyunsaturated fats such as sunflower or generic ‘vegetable’ oil.
Plus we have studies showing that when we cook veggies in extra virgin olive oil, the overall level of antioxidants and other beneficial compounds rises significantly. So we get a double whammy benefit of the good fats present and a greater availability of protective compounds.
Extra virgin olive oil has an unequaled body of research supporting its role as a protective, beneficial food in a healthy diet. It is extremely versatile and can be used cold in dressings and for drizzling, as well as in almost all cooking applications. In this regard it is not only safe but also beneficial to our health, not to mention delivering exceptional flavour! So do as the Mediterranean countries have traditionally done for hundreds of years and enjoy cooking with your extra virgin olive oil.
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