All About Frying II

To understand how the ’76 Steelers can turn into the ’08 Lions, we need to back up a bit and talk about fat composition. Kitchen fats are what are known as trigycerides. Which is to say their molecules are made up of three long-chain fatty acids attached to a “backbone” of glycerol. Imagine a capital letter “E” and you get the idea.

The trouble with these nice orderly fat molecules is that they don’t stay orderly, especially when you expose them to air, water and heat (as in oh, say, a fryer). In such an environment, they steadily, inexorably break down.

The reactions that cause fat molecules to break down are of two basic types: oxidation and hydrolysis. Oxidation, which occurs as the oil is heated and exposed to air, causes the fatty acid chains to break into pieces, yielding all kinds of weird compounds including foul-smelling short-chain fatty acids and ketones (the things that make old oil smell like fish).

Hydrolysis results from the combined effects of heat and water (introduced to the equation by food). It causes the fatty acid chains to break off the glycerol backbone, resulting in free fatty acids and glycerol. If the environment happens to be alkaline (which it becomes as bits of food are cooked and/or burned) a further reaction takes place: saponification.

Now, as some of you may remember from an old post on potash, saponification is the process by which fatty acids, in the presence of an alkaline, are converted into fatty acid salts. In other words: soaps. So now we’ve got soap molecules mixed in with the frying fat. And what does soap allow oil and water to do? Anyone? Anyone? Yes, you in back with the KFC. Right, it allows them to mix. Now we have a fry environment in which fat and water molecules can slip right past each other. And that, my friends, is what turns the ’76 Steeler defensive line into the ’08 Lions. Not a pretty picture for a doughnut. Not pretty at all.