The finely ground product of a cereal seed, especially wheat, primarily used to make bread. A wheat seed consists of an outer coat (husk), with the germ (embryo) at one end and a starchy centre (endosperm). When the seed is ground, it forms a wholemeal flour suitable for baking; if the flour is refined to increase the proportion of endosperm, white flour is produced. Wholemeal flour is richer in fibre, and an important constituent of high-fibre diets, which may reduce the risk of some gastro-intestinal diseases.
Flour is the key ingredient of bread, which is the staple food in many countries, and therefore the availability of adequate supplies of flour has often been a major economic and political issue.Flour is always based on the presence of starches, which are complex carbohydrates.
Usually, the word "flour" used alone refers to wheat flour, which is one of the most important foods in European and American culture. The corresponding Spanish word "harina" normally refers to Maize flour - wheat flour is "harina de trigo". Wheat flour is the main ingredient in most types of breads and pastries. Wheat is so widely used because of an important property: when wheat flour is mixed with water, a complex protein called gluten develops.
Types of flour
Wheat flour
The vast majority of today's flour consumption is wheat flour.
Wheat varieties are typically known as, variously, "white" or "brown" if they have high gluten content, and "soft" or "weak flour" if gluten content is low. 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.
All-purpose flour is a blended wheat flour with an intermediate gluten level which is marketed as an acceptable compromise for most household baking needs.
In terms of the parts of the grain (the grass seed) used in flour—the endosperm or starchy part, the germ or protein part, and the bran or fiber part—there are three general types of flour.
Whole-wheat flour is whole-grain wheat flour.
Bleached flour is flour that was subjected to flour bleaching agents in order to whiten it (freshly milled flour is yellowish) and give it more gluten-producing potential.
Bromated flour is flour with a maturing agent added.
Cake flour is a finely milled flour made from soft wheat.
Graham flour is a special type of whole-wheat flour. Many graham crackers on the market are actually imitation grahams because they do not contain graham flour or even whole-wheat flour.
Pastry flour (also called cookie flour or cracker flour) has slightly higher gluten content than cake flour, but lower than all-purpose flour.
Self-rising or self-raising flour is "white" wheat flour that is sold premixed with chemical leavening agents. Typical ratios are:
U.S. customary: one cup flour 1 to 1½ teaspoon baking powder a pinch to ½ teaspoon salt Metric: 100 g flour 3 g baking powder 1 g or less saltDurum flour is made of durum wheat.
Wheat flour is also highly explosive when airborne, which is why in medieval flour mills candles, lamps, or any other burning substances were strictly forbidden.
Other flours
Corn flour is popular in the Southern and Southwestern US and in Mexico. Most rye breads use a mix of rye and wheat flours because rye has a low gluten content. Most rice flour is made from white rice, thus is essentially a pure starch, but whole-grain brown rice flour is commercially available. Notably, it is the chief ingredient in the bread injera, an important component of Ethiopian cusine Atta flour is also an important flour in Indian cuisine, being used for a range of breads such as roti and chapati. 'Tang flour(not to be confused with the powdered beverage Tang) or wheat starch is a type of wheat flour used primarily in Chinese cooking for making the outer layer of dumplings and buns.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). Flour made from all parts of the grain (extraction rate: 100%) leaves about 2 g ash or more per 100 g dry flour.
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.
In general, as the extraction rate of the flour increases, so do both the protein and the ash content.
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 | ||
| ~0.4% | ~9% | all-purpose flour | 405 |
| ~0.55% | ~11% | pastry flour | 550 |
| ~0.8% | ~14% | high gluten flour | 812 |
| ~1% | ~15% | first clear flour | 1050 |
| >1.5% | ~13% | white whole wheat | 1600 |
This table is only a rough guideline for converting bread recipes.
Flour production
Milling of flour is accomplished by grinding grain between stones or steel wheels.
Flour dust suspended in air is explosive, as is any mixture of a finely powdered flammable substance with air, see Lycopodium. Some devastating and fatal explosions have occurred at flour mills, including an explosion in 1878 at a mill in Minneapolis, the largest flour mill in the United States at the time.
One of the most ancient methods of grinding to produce flour was by using a pair of quern-stones.
Flour products
Bread, pasta, crackers, many cakes, and many other foods are made using flour.
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