If you’ve happened to leave oil or butter in a hot pan long enough, one would start to notice the fumes that emanate from them if it has been exposed to heat over a prolonged duration. This occurrence, known as smoke point, is when fat supersedes its optimum temperature (at which it begins to bubble or shimmer) and might over-caramelise your ingredients most likely in an unfavourable manner if not handled well. For cold-pressed oils which come from crushing nuts or seeds in order to retain their colour, composition and flavour, oils with a low smoke point are best used in their raw form – for purposes such as drizzling, dressing or finishing dishes.
Unrefined or ‘virgin’ oils are loaded with minerals and enzymes which also boost the nutritional value of food, making them susceptible to rancidity. On the contrary, to produce oils with a high smoke point, industrial-level refinement processes are put into play where nutritional compounds are extracted and eliminated – giving them a neutral flavour and long shelf life. A great example of this can be found in ghee or clarified butter – where milk solids are exposed to consistently high heat to extract fat and raise its smoke point, resulting in a nuttier, richer fat base.
With regards to cooking, the desirability of a smoke point is highly relative; in that, certain recipes resort to needing a skillet coated with oil to be extremely hot – in areas like browning or caramelising ingredients. Once heated past smoke point, fat begins to break down further and release free radicals as well as a substance known as acrolein – which gives food its burnt flavour or aroma. In simplistic terms, the higher the smoke point of a fat is, the varied its applications in cooking. While oils like safflower, rice bran, peanut, light olive and sunflower boast of a higher smoke point and neutral flavour, fats such as butter, coconut oil, chicken or duck fat are better suited for basting or low-heat cooking methods.
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Using high smoke point oils for searing, deep-frying, sauteing and sitr-frying means that food cooks evenly, with favourable browning and also retains the flavours and textures that are sought after. Applying high temperatures to high smoke point oils is also a great way for trained cooks to obtain desirable outcomes without altering the integrity of a recipe or ingredient more than necessary. Typically, it is advisable to use and reuse fat only until the time it reaches its smoke point or to discard completely, if its compounds have changed, as a way to avoid spoilage. The aroma of fat when heat is applied to it, can be a telling sign of when it is suitable for use, thus engaging an all-round sensory focus on extracting maximum flavour.