Bread Ingredients: Flour

Flour is a powder made of cereal grains. It is the main ingredient of bread, which is a staple food for many civilizations, making the availability of adequate supplies of flour a major economic and political issue at various times throughout history. Wheat flour is one of the most important foods in European and North American culture, and is the defining ingredient in most European styles of breads and pastries. Maize flour has been important in Mesoamerican cuisine since ancient times, and remains a staple in much of Latin American cuisine.

Flour contains a high proportion of starches, which are complex carbohydrates also known as polysaccharides. Leavening agents are used with some flours, especially those with significant gluten content, to produce lighter and softer baked products by embedding small air bubbles.

The production of flour has also historically driven technological development, as attempts to make gristmills more productive and less labor-intensive led to the watermill and windmill, terms now applied more broadly to uses of water and wind power for purposes other than milling.

Wheat flour

Much more wheat flour is produced than any other flour. Wheat varieties are called "clean," "white," or "brown" if they have high gluten content, and they are called "soft" or "weak" flour if gluten content is low. Hard flour, or bread flour, is high in gluten, with a certain toughness that holds its shape well once baked. Soft flour is comparatively low in gluten and so results in a finer texture. Soft flour is usually divided into cake flour, which is the lowest in gluten, and pastry flour, which has slightly more gluten than cake flour.

In terms of the parts of the grain (the grass fruit) used in flour—the endosperm or starchy part, the germ or protein part, and the bran or fibre part—there are three general types of flour. White flour is made from the endosperm only. Whole grain or wholemeal flour is made from the entire grain, including bran, endosperm, and germ. A germ flour is made from the endosperm and germ, excluding the bran.

All-purpose or plain flour is a blended wheat flour with an intermediate gluten level, which is marketed as an acceptable compromise for most household baking needs.

Bleached flour is treated with flour bleaching agents to whiten it (freshly milled flour is yellowish) and to give it more gluten-producing potential. Oxidizing agents are usually employed, most commonly organic peroxides like acetone peroxide or benzoyl peroxide, nitrogen dioxide, or chlorine. A similar effect can be achieved by letting the flour slowly oxidize with oxygen in the air ("natural aging") for approximately 10 days; however, this process is more expensive due to the time required.

Bromated flour is a flour with a maturing agent added. The agent's role is to help with developing gluten, a role similar to the flour bleaching agents. Bromate is usually used. Other choices are phosphates, ascorbic acid, and malted barley. Bromated flour has been banned in much of the world, as bromate is a suspected carcinogen, but remains available in the United States.

Cake flour is a finely milled flour made from soft wheat. It has very low gluten content, making it suitable for soft-textured cakes and cookies. The higher gluten content of other flours would make the cakes tough. Related to cake flour are masa harina (from maize), maida flour (from wheat or tapioca), and pure starches.

Pastry flour or cookie flour or cracker flour has slightly higher gluten content than cake flour but lower than all-purpose flour. It is suitable for fine, light-textured pastries.

Graham flour is a special type of whole-wheat flour. The endosperm is finely ground, as in white flour, while the bran and germ are coarsely ground. Graham flour is uncommon outside of the USA and Europe.^{[citation needed]} It is the basis of true graham crackers. Many graham crackers on the market are actually imitation grahams because they do not contain graham flour or even whole-wheat flour.

Self-rising or self-raising flour is flour ("white" wheat flour or wholemeal) that is sold premixed with chemical leavening agents. It was invented by Henry Jones. Typical ratios are the following:

1 cup flour
1 teaspoon baking powder
a pinch to ½ teaspoon salt

Metric:

100 g flour
3 g baking powder
1 g or less salt

Sprouted Flour is a new flour that is produced from whole grains that have been sprouted back into an alive plant and then dried prior to milling. Currently, sprouted whole grain hard and soft wheat and sprouted whole grain spelt flours are available in the United States. Sprouted flours may be substituted one for one for most all-purpose flours in recipes. Because the whole grains have been sprouted the flours may be easier to digest.^{[citation needed]}