On Food and Cooking

— by means of conduction. Because the
cellular structure of foods impedes the
movement of heat energy, foods behave more
like insulators than like metals, and heat up
relatively slowly. One of the keys to good
cooking is knowing how to heat a food to the
desired doneness at its center without
overheating its outer regions. This is not a
simple task, because different kinds of foods
heat through at different rates. One of the
most important variables is the thickness of
the food. Though common sense might
suggest that a piece of meat one inch thick
would take twice as long to cook through as a
half-inch piece, it turns out that it takes
somewhere between twice and four times
longer, depending on the overall shape: less
for a compact chop or chunk, more for a broad
steak or fillet. There’s no absolutely reliable
way to predict how long it will take heat to
move from the food surface to its center, so
the best rule is to check the doneness