Flour
From Wikipedia, the free encyclopedia
An ingredient used in many foods, flour is a fine powder made from cereals or other starchy food sources. It is most commonly made from wheat, but also maize (also known as corn), rye, barley, and rice, amongst many other grasses and non-grain plants (including many Australian species of acacia). 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 can also be made from legumes and nuts, such as soy, peanuts, almonds, and other tree nuts.
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. The gluten development is what gives wheat dough an elastic structure that allows it to be worked in a variety of ways, and which allows the retention of gas bubbles in an intact structure, resulting in a sponge-like texture to the final product. This is highly desired for breads, cakes and other baked products. However, certain individuals suffer from an intolerance to wheat gluten known as coeliac or celiac disease. Increased awareness of this disorder, as well as a rising belief in the benefits of a gluten-free diet for persons suffering certain other conditions, has led to an increased demand for bread and other products made with flours which do not contain gluten.
A coarser, somewhat granular preparation, rather than a fine dust, is often called meal.
Contents |
[edit] Types of flour
[edit] Wheat flour
| Protein | |
|---|---|
| 8-10% | Cake Flour |
| 9-10% | Pastry Flour |
| 10-11.5% | All-Purpose Flour |
| 11-13% | Bread Flour |
| 14% and up | High-Gluten 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. Hard flour, or "bread" flour, is high in gluten and so forms 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.
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. White flour is made from the endosperm only. Whole grain 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.
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. Similar effect can be achieved by letting the flour slowly oxidize with oxygen in the air ("natural aging"); however this process is too slow to be commercially viable. Oxidizing agents are therefore employed, most commonly organic peroxides like acetone peroxide or benzoyl peroxide, nitrogen dioxide, or chlorine.
Bromated flour is 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 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.
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. 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.
Pastry flour (also called 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.
Self-rising or self-raising flour is "white" wheat flour that is sold premixed with chemical leavening agents. It was invented by Henry Jones. 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 salt
Durum flour is made of durum wheat. It has the highest protein content, and it is an important component of nearly all noodles and pastas. It is also commonly used to make Indian flatbreads.
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.
[edit] Other flours
- Corn flour is popular in the Southern and Southwestern US and in Mexico. Coarse whole-grain corn flour is usually called corn meal. Corn meal that has been bleached with lye is called masa harina (see masa) and is used to make tortillas and tamales in Mexican cooking. Corn flour should never be confused with cornstarch, which is known as "cornflour" in British English.
- Rye flour is used to bake the traditional sourdough breads of Germany and Scandinavia. Most rye breads use a mix of rye and wheat flours because rye has a low gluten content. Pumpernickel bread is usually made exclusively of rye, and contains a mixture of rye flour and rye meal.
- Rice flour is of great importance in Southeast Asian cuisine. Also edible rice paper can be made from it. Most rice flour is made from white rice, thus is essentially a pure starch, but whole-grain brown rice flour is commercially available.
- Chestnut flour is popular in Corsica, the Périgord and Lunigiana. In Corsica, it is used to cook the local variety of polenta. In Italy, it is mainly used for desserts.
- Chickpea flour (also known as gram flour or besan) is of great importance in Indian cuisine, and in Italy, where it is used for the Ligurian farinata.
- Teff flour is made from the grain teff, and is of considerable importance in eastern Africa (particularly around the horn of Africa). 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.
- Glutinous rice flour or sticky rice flour, used in east and southeast Asian cusines for making tangyuan etc.
- Plain flour is another term for All Purpose flour, used in the UK.
Flour can also be made from buckwheat, soy beans, arrowroot, potatoes, taro, cattails, acorns and other non-grain foodstuffs.
[edit] 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 easy to verify 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. For US bakers of French pastry, one source is King Arthur Flours of Norwich, CT. They supply commercial bakers and also many high-end chain food stores. Their All-purpose flour is a close equivalent to 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 | ||
| ~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. Since the American flour types are not standardized, the numbers may differ between manufacturers.
[edit] 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 water-operated mill, in which a revolving stone wheel turns over a stationary stone wheel, with the grain in between. Many small appliance mills are now available, both hand-cranked and electric.
Flour dust suspended in air is explosive, as is any mixture of a finely powdered flammable substance with air,[1] 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. [2]
[edit] History
In history, both large and hand mills were operated. Until modern times, much flour contained minute amounts of grit, either the result of poor sifting of the grain or of grinding stones together. This grit strongly abraded teeth.
One of the most ancient methods of grinding to produce flour was by using a pair of quern-stones. These were made out of rock, and were ground together by hand. They were generally replaced by millstones once mechanised forms of milling appeared, particularly the water mill and the windmill, although animals were also used to operate the millstones.
[edit] 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.
[edit] External links
- Grain and wheat flour
- Cooking For Engineers - Kitchen Notes: Wheat Flour
- h2g2 entry on Bread Flour
- British Nutrition Foundation - Flour Information
[edit] References
- ^ Williamson, George (06-02-2002). Introduction to Dust Explosions. Retrieved on 2006-10-29.
- ^ Washburn ‘A’ Mill Explosion. Minnesota Historical Society Library History Topics. Retrieved on 2006-10-29.
- The Bread and Flour Regulations 1998, United Kingdom
