Buying and Cooking with Flour

How to buy and cook with flour

Buying Flour
Look for: Tightly sealed bags or boxes. Flours in torn packages or in open bins are exposed to air and to insect contamination.


Avoid: Stained packages—the liquid that stained the package may have seeped through into the flour.

Storing Flour
Store all flours in air- and moisture-proof canisters. Whole wheat flours, which contain the germ and bran of the wheat and are higher in fat than white flours, may become rancid if exposed to air; they should be used within a week after you open the package. If you plan to hold the flour for longer than that, store it in the freezer, tightly wrapped to protect it against air and moisture. You do not have to thaw the flour when you are ready to use it; just measure it out and add it directly to the other ingredients.


Put a bay leaf in the flour canister to help protect against insect infections. Bay leaves are natural insect repellents.

 

What Happens When You Cook with Flour
Protein reactions. The wheat kernel contains several proteins, including gliadin and glutenin. When you mix flour with water, gliadin and glutenin clump together in a sticky mass. Kneading the dough relaxes the long gliadin and glutenin molecules, breaking internal bonds between individual atoms in each gliadin and glutenin molecule and allowing the molecules to unfold and form new bonds between atoms in different molecules. The result is a network structure made of a new gliadin-glutenin compound called gluten.


Gluten is very elastic. The gluten network can stretch to accommodate the gas (carbon dioxide) formed when you add yeast to bread dough or heat a cake batter made with baking powder or baking soda (sodium bicarbonate), trapping the gas and making the bread dough or cake batter rise. When you bake the dough or batter, the gluten network hardens and the bread or cake assumes its finished shape.
 

Starch reactions. Starch consists of molecules of the complex carbohydrates amylose and amylopectin packed into a starch granule. When you heat flour in liquid, the starch granules absorb water molecules, swell, and soften. When the temperature of the liquid reaches approximately 140°F the amylose and amylopectin molecules inside the granules relax and unfold, breaking some of their internal bonds (bonds between atoms on the same molecule) and forming new bonds between atoms on different molecules. The result is a network that traps and holds water molecules. The starch granules then swell, thickening the liquid. If you continue to heat the liquid (or stir it too vigorously), the network will begin to break down, the liquid will leak out of the starch granules, and the sauce will separate.
 

Combination reaction. Coating food with flour takes advantage of the starch reaction (absorbing liquids) and the protein reaction (baking a hard, crisp protein crust).

 

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