June 19, 2010
[caption id="attachment_708" align="alignleft" width="300" caption="A thermometer showing oil temperature of 379°. Note that we are past the smoke point of olive oil (375°), which I normally use, but mercifully short of the smoke point of canola oil (at least 464°), which I was using when this picture was taken."][/caption]
Up until recently, the same sequence of events would occur every time I fried in my cast iron pan.
I’d get the pan nice and hot.
I’d add some oil.
The oil burned, filling the kitchen with acrid smoke.
I’d throw the oil out, scrub out the pan, wait for it to cool a bit, and try again at Step 1.
But last time I fried, I realized that this was senseless. Every type of oil has a known “smoke point”, though this can vary a little bit, and reusing oil will also decrease its smoke point by ten degrees or so for each reuse.
At the smoke point, several things consistently happen. According to Wikipedia, the oil breaks down into glycerol (also known as glycerine, which shows up all over the place in food) and free fatty acids. The glycerol breaks down into acrolein. Acrolein is responsible for the distinctive smell of burnt oil (and indeed its name is from Latin acer, meaning “sharp” or “acrid”, plus olere, “to smell”, compare English olfactory).
So how could I avoid exceeding the smoke point?
Start using a thermometer, duh.
Use the right oil. Not knowing about the smoke point, I figured I may as well use olive oil as canola oil, which most recipes call for. But not only does olive oil impart a particular taste to the food, which may or may not be desirable, it also has a smoke point that is almost a hundred degrees lower (375° vs 464°).
Once I made these changes, things started to go a lot more smoothly. Ah, measurement. Is there anything you can’t do?