Flour

For other uses, see Flour (disambiguation).

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Wheat 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.

Types of flour

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. 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 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.

Flour type numbers

In some markets, the different available flour varieties are labeled according to the ash mass ("mineral content") that remains after a sample was incinerated in a laboratory oven (typically at 550 °C or 900 °C, see international standards ISO 2171 and ICC 104/1). This is an easily verified indicator for the fraction of the whole grain that ended up in the flour, because the mineral content of the starchy endosperm is much lower than that of the outer parts of the grain. Flour made from all parts of the grain (extraction rate: 100%) leaves about 2 g ash or more per 100 g dry flour. Plain white flour (extraction rate: 50-60%) leaves only about 0.4 g.

• German flour type numbers (Mehltype) indicate the amount of ash (measured in milligrams) obtained from 100 g of the dry mass of this flour. Standard wheat flours (defined in DIN 10355) range from type 405 for normal white wheat flour for baking, to strong bread flour types 550, 650, 812, and the darker types 1050 and 1600 for wholegrain breads.
• French flour type numbers (type de farine) are a factor 10 smaller than those used in Germany, because they indicate the ash content (in milligrams) per 10 g flour. Type 55 is the standard, hard-wheat white flour for baking, including puff pastries ("pâte feuilletée"). Type 45 is often called pastry flour, but is generally from a softer wheat. Types 65, 80, and 110 are strong bread flours of increasing darkness, and type 150 is a wholemeal flour.

In the United States and the United Kingdom, no numbered standardized flour types are defined, and the ash mass is only rarely given on the label by flour manufacturers. However, the legally required standard nutrition label specifies the protein content of the flour, which is also a suitable way for comparing the extraction rates of different available flour types.

It is possible to find out ash content from some US manufacturers. However, US measurements are based on wheat with a 14% moisture content. Thus, a US flour with .48 ash would approximate a French Type 55.

In general, as the extraction rate of the flour increases, so do both the protein and the ash content. However, as the extraction rate approaches 100% (whole meal), the protein content drops slightly, while the ash content continues to rise.

The following table shows some typical examples of how protein and ash content relate to each other in wheat flour:

Ash	Protein	Wheat flour type
		US	German	French
~0.4%	~9%	pastry flour	405	45
~0.55%	~11%	all-purpose flour	550	55
~0.8%	~14%	high gluten flour	812	80
~1%	~15%	first clear flour	1050	110
>1.5%	~13%	white whole wheat	1600	150

This table is only a rough guideline for converting bread recipes. Since flour types are not standardized in many countries, the numbers may differ between manufacturers.

Flour production

Milling of flour is accomplished by grinding grain between stones or steel wheels. Today, "stone-ground" usually means that the grain has been ground in a mill in which a revolving stone wheel turns over a stationary stone wheel, vertically or horizontally with the grain in between. Many small appliance mills are available, both hand-cranked and electric. The mill stones frequently rub against each other resulting in small stone particles chipping off and getting into flour. Safety aspect of this has not been checked. Steel roller mills do not have this problem.

Flammability

Flour dust suspended in air is explosive, as is any mixture of a finely powdered flammable substance with air, see Flour Bomb. In medieval flour mills, candles, lamps, or other sources of fire were forbidden. Some devastating and fatal explosions have occurred at flour mills, including an explosion in 1878 at the Washburn "A" Mill in Minneapolis, the largest flour mill in the United States at the time.

Flour products

Bread, pasta, crackers, many cakes, and many other foods are made using flour. Wheat flour is also used to make a roux as a base for gravy and sauces. White wheat flour is the traditional base for wallpaper paste. It is also the base for papier-mâché. Cornstarch is a principal ingredient of many puddings or desserts.

External links

• Flour volume vs. weight calculators (US/Metric for all flour types)
• Weight of Baking Ingredients Flour and Water
• Grain and wheat flour
• Cooking For Engineers - Kitchen Notes: Wheat Flour
• h2g2 entry on Bread Flour
• British Nutrition Foundation - Flour Information
• Flour Turkey

References

• The Bread and Flour Regulations 1998, United Kingdom.
•  This article incorporates text from a publication now in the public domain: Ward, Artemas (1911). "The Grocer's Encyclopedia". The Grocer's Encyclopedia.