Altering the palette Food color

Carotenoids — the natural red and yellow pigments that make carrots and sweet potatoes orange and tomatoes red — are practically impervious to heat and the acidity or alkalinity of cooking liquids. No matter how you cook them or how long, carotenoids stay bright and sunny.

You can't say the same for the other pigments in food: The other pigments that make food naturally red, green, or white react — usually for the worse — to heat, acids (such as wine, vinegar, or tomato juice), and basic (alkaline) chemicals (such as mineral water or baking soda and water). Here's a brief rundown on the color changes that you can expect when you cook food:

I Red beets and cabbage get their colors from pigments called antho-cyanins. Acids make these pigments redder. Alkaline solutions fade anthocyanins from red to bluish purple.

I Potatoes, cauliflower, rice, and white onions are white because they contain pigments called anthoxanthins. When anthoxanthins are exposed to alkaline chemicals (mineralized water or baking soda), they turn yellow or brownish. Acids prevent this reaction. Boil cauliflower florets in tomato juice, rinse off the juice, and you'll see — white cauliflower!

I Green veggies are colored by chlorophyll, a pigment that reacts with acids in cooking water (or in the vegetable itself) to form pheophytin, a brown pigment. The only way to short-circuit this reaction is to protect the vegetables from acids. Old-time cooks added alkaline baking soda, but that increases the loss of certain vitamins (see "Protecting the Nutrients in Cooked Foods" later in this chapter) and softens the vegetables. Fast cooking at high heat or cooking in lots of water (which dilutes acids) lessens these color changes.

I The natural red color of fresh meat comes from myoglobin in the muscle tissue and hemoglobin in blood. When meat is heated, the pigment molecules are denatured, or broken into fragments. They lose oxygen and turn brown or — after long cooking — turn the really unappetizing gray characteristic of steam-table meats. This inevitable change is more noticeable in beef than in pork or veal because beef starts out naturally redder.

Red to blue and back again

The following experiment lets you see colors change right before your very eyes. Gather i 1 small can sliced beets i 1 saucepan i 3 small glass bowls i 1 cup water i 1 teaspoon baking soda i 3 tablespoons white vinegar

Line up the glass bowls on your kitchen counter. Open the can. Remove six slices of beets. Put two slices in the first glass bowl and four slices in the saucepan. Put the rest in a small container and refrigerate for dinner. No sense wasting good beets!

Mix the baking soda into the water and add this alkaline solution to the saucepan. Heat for 4 minutes; don't heat too high — the solution foams. Turn off the heat. Remove the beets from the pan. Put two slices each in the second and third glass bowls.

Ignore the second bowl. Add the vinegar (an acid) to the third bowl. Wait two minutes. Now look: The beets in the first bowl (straight from the can) should still be bright red. Alkaline compounds darken colors, so the beets in the second bowl, straight from the baking soda bath, should be almost navy blue. Acids reverse the reaction, so beets in the third bowl, with added vinegar, should be heading back to bright red. Not yet? Add another tablespoon of vinegar.

Ain't chemistry grand?

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