One of the first eye-openers I had at culinary school was a very simple explanation of how different elements of food behave when they get exposed to heat.  It sounds rudimentary, and I guess it is, in a way, but until somebody explains it to you bluntly, it’s not really something you think about (I didn’t, anyway).  Once you know this stuff, though, you’ll know what to expect whenever you put something on the stove or in the oven.  That’s a big, big step.

When they get hot:

  1. Proteins coagulate.  You lose moisture, and the texture gets firm.  That’s how a cooked steak differs from a raw one, and how a cooked egg differs from a raw one.  Whenever you cook a protein, that’s what you can expect to happen–it’ll tighten up and start to dry out.  The longer you cook it, the tougher and drier it’ll get.  Coagulation generally starts to happen around 160° F.
  2. Starches gelatinize.  Gelatinization–aside from being an awkward mouthful–is a pretty funky phenomenon.  Grains of starch soak up water, and get clear and soft (a process called “autolysis”).  The grains swell up, which means that they occupy more space, and your liquid is suddenly thicker.  Gelatinization generally starts around 150º F, and continues up to around the boiling point (212º F).  It happens pretty slowly, but it happens every time.
  3. Sugars caramelize.  Almost everything has some kind and level of sugar in it, and when you cook it, it turns brown.  Sucrose–ordinary table sugar–starts to caramelize at about 338º F; different sugars–maltose, lactose, fructose–also caramelize, but at slightly different temperatures. Water can’t get any hotter than 212º F, so nothing in water will get hot enough to caramelize; you need dry heat to achieve it.  As far as I can tell, everything tastes better caramelized.  Those grill marks on your steak?  That’s caramelization.  Imagine, for contrast, eating a boiled steak.  Ick.
  4. Water evaporates.  Every single food on earth has at least some water in it.  Some things, like eggs, milk, fruits, and leafy vegetables, are mostly water.  Believe it or not, raw meat can be as much as 75% water.  When the internal temperature of the food goes up, the water turns into steam, and off it goes into the atmosphere.  If you do it on purpose to make a sauce thicker, it’s called “reduction.”
  5. Fats melt.  They soften and then they liquefy, but they don’t evaporate (an oil is just a fat that stays liquid at room temperature).  Most fats tolerate relatively high heat without burning–again, they’re not water-based, so they don’t evaporate–and they make a nice medium for browning foods.  They have the added benefit of being lip-smacking delicious, unlike water.