Flour is a powder which is made by grinding cereal grains, other seeds or roots (like Cassava). It is the main ingredient of bread, which is a staple food for many cultures, 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, North American, Middle Eastern and North African cultures, and is the defining ingredient in most of their 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. Rye flour is an important constituent of bread in much of central/northern Europe.
Contents |
The word "flour" is originally a variant of the word "flower". Both derive from the Old French fleur or flour, which had the literal meaning "blossom," and a figurative meaning "the finest." The phrase "fleur de farine" meant "the finest part of the meal," since flour resulted from the elimination of coarse and unwanted matter from the grain during milling.[1]
It was discovered around 9000 BC that wheat seeds could be crushed between simple millstones to make flour.[2] The Romans were the first to grind seeds on cone mills. In 1879, at the beginning of the Industrial Era, the first steam mill was erected in London.[3] In the 1930s, some flour began to be enriched with iron, niacin, thiamine and riboflavin. In the 1940s, mills started to enrich flour and folic acid was added to the list in the 1990s.
An important problem of the industrial revolution was the preservation of flour. Transportation distances and a relatively slow distribution system collided with natural shelf life. The reason for the limited shelf life is the fatty acids of the germ, which react from the moment they are exposed to oxygen. This occurs when grain is milled; the fatty acids oxidize and flour starts to become rancid. Depending on climate and grain quality, this process takes six to nine months. In the late 19th century, this process was too short for an industrial production and distribution cycle. As vitamins, micro nutrients and amino acids were completely or relatively unknown in the late 19th century, removing the germ was a brilliant solution. Without the germ, flour cannot become rancid. Degermed flour became standard. Degermation started in densely populated areas and took approximately one generation to reach the countryside. Heat-processed flour is flour where the germ is first separated from the endosperm and bran, then processed with steam, dry heat or microwave and blended into flour again.[4]
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, but it is removed before getting sold.
Rollermills soon replaced stone grist mills as the production of flour has historically driven technological development, as attempts to make gristmills more productive and less labor-intensive led to the watermill[5] and windmill. These terms are now applied more broadly to uses of water and wind power for purposes other than milling.[6] More recently, the Unifine mill, an impact-type mill, was developed in the mid-20th century.
Flour contains a high proportion of starches, which are a subset of complex carbohydrates also known as polysaccharides. The kinds of flour used in cooking include all-purpose flour, self-raising flour, and cake flour including bleached flour. The higher the protein content the harder and stronger the flour and will produce crusty or chewy breads. The lower the protein the softer the flour for better cakes, cookies, and pie crusts.[7]
Unbleached flour is simply flour that has not undergone bleaching and therefore does not have the color of "white" flour. An example of this would be the Graham flour. Sylvester Graham was against using bleaching agents, as being unhealthy.
"Bleached flour" is any flour with a whitening agent added and is referred to as refined flour. Cake flour is high in starch and low in protein and when chlorinated (bleached) allows cakes and other baked goods to set faster, rise better, the fat to be distributed more evenly, and there is less vulnerability to collapse. There are several kinds of bleaching agents added to flour. These agents oxidize the surfaces of the flour grains and aid with developing (maturing) of gluten. Bleaching makes flour slightly acidic and the taste can be noticed. The chlorination does assist in causing the small bubbles that allow baked goods to be fluffy. Different chemicals are used for Flour treatment agents to improve color and use in baking;
Flour that does not have a leavening agent is called plain or all-purpose flour. It is appropriate for most bread and pizza bases. Some cookies are also prepared using this type of flour. Bread flour is high in gluten protein, with 12.5-14% protein compared to 10-12% protein in all-purpose flour. The increased protein binds to the flour to entrap carbon dioxide released by the yeast fermentation process, resulting in a stronger rise.
Leavening agents are used with some flours,[8] especially those with significant gluten content, to produce lighter and softer baked products by embedding small gas bubbles. Self-rising (or self-raising) flour is sold premixed with chemical leavening agents. The added ingredients are evenly distributed throughout the flour which aids a consistent rise in baked goods. This flour is generally used for preparing scones, biscuits, muffins, etc. It was invented by Henry Jones and patented in 1845. Plain flour can be used to make a type of self-rising flour although the flour will be coarser. Self-rising flour is typically composed of the following ratio:
During the process of making flour nutrients are lost. Some of these nutrients are replaced during refining and the result is "enriched flour".
More wheat flour is produced than any other flour. Wheat varieties are called "clean," "white," or "brown" or "strong" or "hard" if they have high gluten content, and they are called "soft" or "weak" flour if gluten content is low.
Flour can also be made from soy beans, peanuts, arrowroot, taro, cattails, acorns, quinoa and other non-cereal foodstuffs.
In some markets, the different available flour varieties are labeled according to the ash mass ("mineral content") that remains after a sample is 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 remains 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.
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 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. 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 | Italian | ||
| ~0.4% | ~9% | pastry flour | 405 | 40 | 00 |
| ~0.55% | ~11% | all-purpose flour | 550 | 55 | 0 |
| ~0.8% | ~14% | high gluten flour | 812 | 80 | 1 |
| ~1% | ~15% | first clear flour | 1050 | 110 | 2 |
| >1.5% | ~13% | white whole wheat | 1600 | 150 | Farina integrale di grano tenero |
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. Note that there is no Type 40 French flour. The closest is Type 45.
It is possible to determine ash content from some US manufacturers. However, US measurements are based on wheat with a 14% moisture content. Thus, a US flour with 0.48% ash would approximate a French Type 55. For US bakers of French pastry seeking an equivalent, for example, they could look at tables published by King Arthur Flour, showing their all-purpose flour is a close equivalent to French Type 55.
Other measurable properties of flour as used in baking can be determined using a variety of specialized instruments, such as the Farinograph.
Flour dust suspended in air is explosive -- as is any mixture of a finely powdered flammable substance with air[15] (see flour bomb). 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.[16]
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. It is also the base for papier-mâché.
Cornstarch is a principal ingredient of many puddings or desserts.
|
|||||||||||||||||||||||||||||||||||
|
|||||||||||||||||||||||