The smoking point is the temperature at which a fat or oil, when being heated, will start to give off smoke.
What happens inside the fat or oil is that it starts to break down.
This also changes the flavour, usually for the worst. Mustard oil is an exception: Indians always heat mustard oil to its smoking point before using it, because the flavour improves.
The oils also become less nutritious for you, because “free radicals” are released. The exception, again, is mustard oil — it actually becomes healthier for you at the smoke point.
Refined oils and saturated oils tend to have the highest smoke points (though they’re also said to be the worst for our bodies.)
It’s okay to strain, save and re-use oil for deep-frying, but its smoking point will decrease with use.
“It’s worth bearing in mind that if you use a deep-fat fryer or similar you should change the oil or fat regularly because as well as choosing the right fat, you should minimise the number of times you use that fat or oil. The reason for this is because reheating the same oil will increase the production of oxidative compounds – you may even see this for yourself as the colour of the oil starts to change. Each time you cook with an oil you actually lower its original smoke point, so you will see over time that the oil becomes less stable at the high temperatures being demanded of it.”  Cooking with Fat. In: Healthy Cooking Made Easy with BBC Good Food. BBC Good Food. Micro course. Step 4.6. Accessed August 2021 at https://www.futurelearn.com/courses/healthy-cooking-made-easy-with-bbc-good-food/2/steps/1224910
Some stir-fry experts say that despite everything you hear, stir-frying is best done once the oil you are using has reached its smoking point.
When choosing an oil for cooking, you will want to look at the cooking temperature required, and then consider the healthiest oil you can use that won’t smoke at that temperature. When it smokes, that oil is creating unhealthy compounds in it. You want to choose one that will remain stable at the higher cooking temperature your recipe requires.
“When we talk about an oil’s ‘smoke point’ we’re referring to the temperature at which the oil or fat starts to produce a visible smoke. This smoke is often blue-grey in colour and happens when the fat or oil reaches the temperature that causes the oil to burn – this is the point the oil breaks down and becomes damaged, or its ‘smoke point’… When your oil starts to smoke like this, it’s oxidative compounds that are being produced.”  Cooking with Fat. In: Healthy Cooking Made Easy with BBC Good Food. BBC Good Food. Micro course. Step 4.6. Accessed August 2021 at https://www.futurelearn.com/courses/healthy-cooking-made-easy-with-bbc-good-food/2/steps/1224910
|↑1||Cooking with Fat. In: Healthy Cooking Made Easy with BBC Good Food. BBC Good Food. Micro course. Step 4.6. Accessed August 2021 at https://www.futurelearn.com/courses/healthy-cooking-made-easy-with-bbc-good-food/2/steps/1224910|
|↑2||Cooking with Fat. In: Healthy Cooking Made Easy with BBC Good Food. BBC Good Food. Micro course. Step 4.6. Accessed August 2021 at https://www.futurelearn.com/courses/healthy-cooking-made-easy-with-bbc-good-food/2/steps/1224910|