The Food Lab: Better Home Cooking Through Science

pressure of water vapor bubbles escaping the food will
prevent oil from rushing into the food, and therefore your
food will remain grease free. At first glance, it makes sense,
right? I mean, we’ve all eaten bad fried food that’s come out
of a too-cool fryer, and indeed it does taste heavy and
greasy. But is it actually because it contains more grease? A
study reported in the Journal of Food Process Engineering
says differently.
Turns out that the truth is quite the opposite: the hotter
you fry your food, the more oil it will absorb. See, most
foods that you throw in the fryer—whether batter-coated
food, potatoes, or a hunk of chicken—are filled with water.
They are literally saturated with the stuff. Imagine that
French fry, for example, as a hotel with no vacancies—
every single room is filled up with a water molecule. In
order for any oil at all to penetrate the potato and take up
residence, some of that water must first check out. If you
think about this, you already know it: drop a piece of cold
potato into a cold pot of oil. Does it absorb any of that oil?
Nope. Wash the potato off, and it’s as if the oil was never
there. Now, here’s the thing: water is pretty happy with its
cellular accommodations. The only way to get it to leave is
through forceful eviction, namely by adding some energy to
it in the form of heat. When you drop a piece of potato into
hot oil, energy from the oil is transferred to the water inside
it, which will eventually absorb so much energy that it leaps
from within the potato’s cells and escapes in a bubble of
vapor—thus freeing up a room for the oil to check into.
The water in a piece of food being fried exists in two
forms: Free water will easily escape, jumping out of the food