What is an Oil Smoke Point & Why Does it Matter?
So long as you can deep fry with it, the type of oil you’re using doesn’t really matter, right? Well, you’ve got it all wrong. For many years, most of us only knew about sunflower, canola, vegetable and vis olie. But there are a number of different oils and they each have what’s called a ‘smoke point’. Apart from avoiding burning your kitchen down, the smoke point of an oil is important for various reasons. Most people usually buy one type of oil for general purpose useage, but it’s worth learning about the respective properties of oils.
Some things to consider when buying oil is whether it will be used for baking, cooking, frying or dressing. Another factor is the flavour of the oil. While there are odourless oils, certain types of oils lend a unique flavour to dishes. Sesame and peanut oil, typically used in Asian dishes, have a distinct flavour and are used to impart that note into dishes. Olive oil is another example, as there are different styles based on the olive cultivar used that could impact the overall flavour profile of dishes.
But what does this have to do with the smoke point of oils?
Oils can be categorised as refined, unrefined and cold-pressed. Certain oils that undergo refinement are stripped of impurities, this also neutralises the natural odour and flavour of oil. When oil is refined, this changes its chemical composition and impacts the smoke point.
Refined and Unrefined Oil
More refined oils generally tend to have a higher smoke point, which is important to consider if your dish requires a longer cook time. Using an oil with a lower smoke point for frying could result in burning and impart an unpleasant taste to your food, which would be a discredit to your efforts in preparing the dish.
Why are oils refined?
There are twenty-two different types of oil commercially available. Oil is extracted from plants and seeds, like avocado, sunflower, canola (rapeseed), soybean or peanut oil – these are commonly known as ‘vegetable oil’. After the oil is expressed from the plant or seed, manufacturers then decide whether it will be bottled, refined or processed further.
Oil is refined and bleached in order to remove impurities and nutrients, which produces a more stable chemical composition. Basically, the smoke released as a result of oils being heated at high temperatures is the breaking down of fatty acids. Refined oils contain fewer fatty acids, meaning they have higher smoke points and are able to withstand higher temperatures. These oils are generally suited for deep-frying, grilling at high temperatures, slow ‘n low cooking or tempering spices when making curry. For example, refined oil may be better for frying than cold-pressed oil.
Oils that are bottled straight away are referred to as unrefined, raw, cold-pressed or virgin oils. Common household oils that are unrefined include extra virgin olive oil and coconut oil. These are normally thought of as ‘healthier’ oils because they undergo minimal intervention and processing and the flavour, nutrients and minerals are retained.
Supermarkets usually stock both refined and unrefined versions, this is normally dependent on the marketed purpose of the oil (baking, cooking, deep frying). Unrefined oils are ‘fresher’ and thus have a shorter shelf-life, as they haven’t been bleached or filtered. As a result, they tend to contain more fatty acids, meaning they have a lower smoke point.
Saturated: products like butter, ghee and lard contain saturated fats.
Unsaturated fats: oils which are liquid at room temperature and sourced from seeds and nuts are generally healthier choices.
Monounsaturated fats: oils with a single double bond, such as omega 9 and oleic acid.
Polyunsaturated oils: omega-3 & 6 fatty acids oils contain more bonds, meaning they have lower smoke points.
Different Smoke Points of Oils
Most people wouldn’t have a thermometer to check the exact smoke point of oil, and sticking your finger in the oil is not advised, for obvious reasons. When preparing oil for either shallow or deep frying, we can normally tell when the oil is properly heated as it begins to shimmer or ripple. If the oil exceeds the point of shimmering and is heated for too long, it reaches a temperature where smoke is released, also known as the ‘smoke point’.
The smoke point is the temperature at which the chemical composition of the oil alters and free fatty acids break down due to heat and exposure to oxygen, resulting in the build-up of carcinogens.
High Smoke Point
These oils usually contain monounsaturated fats with fewer bonds to break down, meaning they have higher smoke points. Any reading from 204 °C and above is considered a high smoke point. These oils are good for deep frying, tempering curry spices and grilling. Refined avocado oil has one of the highest smoke points, followed by safflower and rice bran oil.
Saturated fats (think butter) generally have a lower smoke point and tend to burn easily, whereas saturated fats such as coconut and palm oil have higher smoke points. Ghee or clarified butter is an exception, as water and milk solids are removed through heating. Vegetable oil is unpredictable, as it ranges anywhere between 204 to 232 °C. Canola and peanut oil have medium smoke points and are more stable oils.
Low Smoke Point
Oils with low smoke points are not normally recommended for preparing foods that require longer cook times. These types of oil usually have a smoke point below 203 °C. Unrefined or virgin oils that are thought to be less neutral in flavour typically have a lower smoke point. Examples include duck fat, grapeseed oil and unrefined sesame oil.
Smoke Point Chart
When purchasing oil, bear in mind that in the same way nutritional values differ across brands, the smoke point may differ depending on the treatment of the oil.
Learn all about The Difference Between Extra Virgin & Other Olive Oil Varieties.
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