Starch

White flour consists of about 68 to 76% starch. Starches are complex carbohydrates whose molecules consist of long chains of simpler sugars bound together. The starches in flour are contained in granules. Most of these tiny granules remain intact until they come in contact with water during the mixing process, at which time they absorb water and swell in size. Starch can absorb from one-quarter to one-half its weight in water.

A very small amount of the starch is broken down into sugars during milling or storage. This sugar is available as food for yeast.