|MadSci Network: Chemistry|
Hi there! Smoke point is the temperature to which oil can be heated before it smokes and discolors — an indication of decomposition.
When combining a high smoke point oil with low smoke point oils (like those in butter), it doesn't affect both of their smoking points. The addition of butter reduces the cooking temperature therefore the oil will not reach its smoke point. On the other hand, the presence of oil will not burn the butter during cooking.
The oil or fat you use for deep-frying should have a high smoke point. While butter, whole or clarified, is the preferred fat for baking as it adds the most flavour, it's not ideal for frying since it will burn at a lower temperature than most oils.
Adding a knob of butter to oil will not burn the butter because when the oil reaches its smoking point, the overall cooking temperature will be reduced by the butter.
Try adding butter to oil for the flavor benefit of butter and the higher temperature range of oil.
I hope you find my answer enlightening.
(Admin note: The bottom line appears to be that the blending will not actually raise either smoke point. But when the lower temperature oil begins to decompose, it will not smoke because the higher temperature oil acts as a diluent and solvent. On the other hand, the presence of the lower temperature oil will mean that the higher temperature oil can cook more effectively, and therefore need not be taken to temperatures at or above its smoke point.)
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