Additional Math Pages & Resources

Tuesday, September 14, 2010

Soft, Hard or In-Between; Light, Dark or Just Right

Today we're talking eggs and toast - or specifically, about cooking. Why do cooking times vary so much? Why does the toast burn? Why are eggs runny? Why is the broccoli hard? Why do the chops seem like rubber? Can math help?


Cooking is a very complex thing. I believe it's as difficult as navigating through Paris with a jet-lagged spouse, a rental car, an old map, and no French.


Even if we bypass the challenges of finding a recipe, gathering the ingredients and combining them, cooking is hard. So today, why not start at the point where we apply heat?

1. We have a mass of food (lump of meat, ball of dough, skillet full of bits, etc.)
2. We put it on a burner, into an oven, or onto a grille.
3. It gets hot, right? But how quickly hot, how humidly hot, how completely hot hot? When is it done?

Those are the key questions. We don't really know the mass of the food that we start with. A pot full. We don't know how much heat we are adding. Turn knob to hi. We aren't positive about the internal temperature. Use a probe thermometer; insert toothpick, etc. We don't know how quickly it's cooking. Do not open oven, or remove lid.

Let's take an example:

I make bread every 3-4 days, with 16 ounces of water at room temperature, 1/2 teaspoon of yeast, 20 ounces of bread flour, and one tablespoon of kosher salt. That's my normal recipe. Elementary math tells me I have about 37 ounces of dough by weight, and (16 ÷ 37 = ) 43% is water.


I let the dough ferment for 8-16 hours on top of my refrigerator. Let's say at 68° F. I don't think there's significant evaporation because it's in a covered container.


I dump the dough out onto the counter and form it into a ball, using another ounce or so of flour. The resulting ball rises again for 90 minutes.


In the meantime, I heat my steam oven to 450° F. I slide in the bread. My dough absorbs the heat for 10 minutes, rising rapidly, then I turn the oven down to 400° F and allow it to bake for about an hour.


Why the uncertainty? Why not an exact time, if I am controlling time, ingredients and temperature?

Because even doing this in the same room, using the same equipment, and the same basic recipe, there are variations. Flours vary from brand to brand. The humidity changes, the room temperature changes, and the chemistry changes. If I add even a teaspoon of oil, a tablespoon of sugar or a splash of milk, the bread will brown much faster. But that doesn't mean it's "done," it just means the top gets black unless I cover it with foil or turn the heat down. (Look up Maillard Reaction to understand this part.)

If the dough is covered, less moisture escapes, so the loaf can be too moist. If I turn the heat down, it takes longer to bake. If I bake the dough in a pan, the timing is different from making a round loaf.

Note: Food scientists have worked out all these things and "factory" bread is consistent from loaf to loaf. But it's not the same substance as bread made by yourself or in an artisan bakery.

Like many things in life, you have to pay attention. You don't use math to decide when the bread is done. Math helps us understand what's going on but doesn't take away the WORK of cooking.

Math allows us to have consistent dough to start with. But we don't have a scale in the oven that reports me when enough water is evaporated out of the loaf (about 8 ounces). Or a sensor that monitors the darkness of the crust and says "Take me out now!" Compare a bread-machine loaf with an oven loaf and you will see what I mean.

Great food comes from trial and error plus science and math when appropriate. But it's still hard work.


Although we do have a sensor that tells us when the bread has been in too long. It's the smoke alarm...