In the culinary sense, flour is a powder made of cereal grains, other seeds, or roots. 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, 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.
Flour contains 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 gas 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.//
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.
A central 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 6 to 9 months. In the late 19th century this period was too short for an industrial production and distribution cycle. As vitamins, micronutrients and amino acids were completely or relatively unknown in the late 19th century, taking out the germ was a brilliant solution. Without the germ, flour cannot become rancid. Degerminated flour became standard. Degermination 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 submerged into flour again.
Flour can also be made from soy beans, peanuts, arrowroot, taro, cattails, acorns, quinoa and other non-cereal foodstuffs. In Australia, a variety of other seeds are also used to make flour for bread, these include: Acacia aneura (mulga), Acacia cowleana, Acacia estrophiolata (ironweed), Acacia ligulata (umbrella bush), Acacia murrayana (tjuntjula), Acacia tetragonophylla (wakalpulka), Acacia kempeana (Witchetty bush), Acacia coriacea (Wiry wattle), Panicum spp. (eg Panicum australiense, Panicum decompositum, Panicum effusum), Astrelba pectinata (Mitchell grass), Portulaca oleracea, Portulaca intraterranea, Oryza sativa, Marsilea drummondii (Nardoo), Atriplex nummularia (Old man saltbush), Acacia notabilis, Acacia pyrifolia, Acacia tetragonophylla, Acacia victoriae, Acacia sophorae, Acacia stenophylla, Acacia tumida, Aleurites moluccana, Amaranthus mitchellii, Amaranthus grandiflorus, Brachiaria piligera, Brachiaria milliformis, Brachychiton diversifolium, Brachychiton gregorii, Brachychiton paradoxum, Brachychiton populneum, Bruguiera rheedii, Calandrinia balonensis, Canarium australianum, Canavalia maritima, Entada phaseolides, Eragrostris eriopoda (Wangunu), Eucalyptus leptopoda, Eucalyptus microtheca, Nymphae gigantea, Rhyncharrhena linearis, Themeda australis
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 Â°C or 900 Â°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: 50â€“60%) leaves only about 0.4 g.German flour type numbers (Mehltyp) 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 (``pÃ¢te feuilletÃ©e``). 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 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.
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 40 ~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.
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. The safety aspect of this has not been checked but research into the dentition of medieval skeletons indicates that this form of milling leads to excessive wear on teeth. Steel roller mills do not have this problem.
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.
The Great Fire of London in 1666, which destroyed most of central London, started in a bakery in Pudding Lane, which was likely caused by a flour explosion.
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-mÃ¢chÃ©.
Cornstarch is a principal ingredient of many puddings or desserts.