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What Is Flour? |
Flour is a finely ground powder prepared from grain or other starchy plant foods and used in baking. Although flour can be made from a wide variety of plants, the vast majority is made from wheat. Dough made from wheat flour is particularly well suited to baking bread because it contains a large amount of gluten, a substance composed of strong, elastic proteins. The gluten forms a network throughout the dough, trapping the gases which are formed by yeast, baking powder, or other leavening agents. This causes the dough to rise, resulting in light, soft bread.
Flour has been made since prehistoric times. The earliest methods used for producing flour all involved grinding grain between stones. These methods included the mortar and pestle (a stone club striking grain held in a stone bowl), the saddlestone (a cylindrical stone rolling against grain held in a stone bowl), and the quern (a horizontal, disk-shaped stone spinning on top of grain held on another horizontal stone). These devices were all operated by hand.
The millstone, a later development, consisted of one vertical, disk-shaped stone rolling on grain sitting on a horizontal, disk-shaped stone. Millstones were first operated by human or animal power. The ancient Romans used waterwheels to power millstones. Windmills were also used to power millstones in Europe by the twelfth century.
The first mill in the North American colonies appeared in Boston in 1632 and was powered by wind. Most later mills in the region used water. The availability of water power and water transportation made Philadelphia, Pennsylvania, the center of milling in the newly independent United States. The first fully automatic mill was built near Philadelphia by Oliver Evans in 1784. During the next century, the center of milling moved as railroads developed, eventually settling in Minneapolis, Minnesota. During the nineteenth century numerous improvements were made in mill technology. In 1865, Edmund La Croix introduced the first middlings purifier in Hastings, Minnesota. This device consisted of a vibrating screen through which air was blown to remove bran from ground wheat. The resulting product, known as middlings or farina, could be further ground into high-quality flour. In 1878, the first important roller mill was used in Minneapolis, Minnesota. This new type of mill used metal rollers, rather than millstones, to grind wheat. Roller mills were less expensive, more efficient, more uniform, and cleaner than millstones. Modern versions of middlings purifiers and roller mills are still used to make flour today.
The Components of Flour:
In addition to the type of grain used, flour also varies depending on what part of the grain is retained during the milling process. This may include the endosperm, bran or germ.
¶ Endosperm: This is the starchy center of the grain, which contains carbohydrates, protein and a small amount of oil. Most simple white flours contain only this portion of the grain.
Bran: The outer husk of the grain, known as bran, adds texture, color, and fiber to flour. Bran gives whole grain flours their characteristic brown color and rough texture.
Germ: The germ is the reproductive epicenter of the grain and is a concentrated source of nutrients. Flour that retains the germ during the milling process will contain more vitamins, minerals, and fiber.
Gluten: Gluten is a protein found naturally in the endosperm of wheat. It gives strength, elasticity and a characteristic chewy texture to yeast breads, pasta and pizza dough.
Common Flour Varieties
All-Purpose: All-purpose flour is made from the endosperm of wheat. This flour is often bleached to give it a clean, white appearance and enriched to include nutrients that are lost due to the removal of the germ and bran. All-purpose flour has a medium balance of starch and protein so that it can be used in a wide variety of products without being too heavy or too delicate.
Unbleached: Unbleached flour is similar in composition to all-purpose flour but has not been chemically bleached. Unbleached flour can be used successfully in as many recipes as all-purpose flour. Unbleached flour is a good choice for those who are concerned with flavor purity or exposure to chemicals.
Bread Flour: Bread flour contains a higher ratio of protein to carbohydrates than all-purpose, which produces stronger dough. The strong gluten matrix provides structure to rising dough and gives the end product a nice, chewy texture.
Cake Flour: Cake flour contains less protein than all-purpose and is milled to a finer texture. These two factors combined create a softer and more delicate crumb. Cake flour is often bleached to improve its appearance.
Pastry Flour: Pastry flour has a medium protein content and is between all-purpose and cake flour in texture. The fine texture produces flakey pastry crust while the slightly lower protein content prevents pastries from being too dense or chewy. In addition to pastries, this flour is also great for making cookies, biscuits, and quick breads.
Self-Rising: Self-rising flour is mainly used to make biscuits and other quick breads. It is comprised of all-purpose flour, salt and a chemical leavening agent such as baking powder.
Self-rising flour should never be used to make yeast breads.
Whole Wheat: Whole wheat flour is made by grinding the entire grain (endosperm, bran, and germ). This flour contains more nutrients and fiber than all-purpose making it popular among health conscious individuals. Because bran can interfere with the formation of a gluten matrix in dough, whole wheat flour often produces a heavier, denser bread than all-purpose or bread flours.
Stone Ground: Stone ground flour is the same as whole wheat flour but is milled to a coarser texture. Stone ground flour is valued for its characteristic rough texture and rustic look.
Semolina: Semolina is flour made from a specific variety of wheat known as Durum. Durum wheat has an exceptionally high protein content, giving it a very dense, chewy texture. For this reason, semolina is most often used to make pasta.
Rice Flour: This flour is made from milling grains of rice and can be found in both white (endosperm only) and brown (whole grain) varieties. Rice flour is lighter in texture than wheat flours and is a popular choice among those who are intolerant to gluten.
Masa Harina: Masa Harina is flour made from milling corn that has been treated with an alkaline solution, usually containing lime. The lime helps loosen the cornís husk prior to milling and improves the nutritional content of the flour. Masa harina is used to make tortillas, tamales and other dishes popular in Central America.
Although most flour is made from wheat, it can also be made from other starchy plant foods. These include barley, buckwheat, corn, lima beans, oats, peanuts, potatoes, soybeans, rice, and rye. Many varieties of wheat exist for use in making flour. In general, wheat is either hard (containing 11-18% protein) or soft (containing 8-11% protein). Flour intended to be used to bake bread is made from hard wheat. The high percentage of protein in hard wheat means the dough will have more gluten, allowing it to rise more than soft wheat flour. Flour intended to be used to bake cakes and pastry is made from soft wheat. All-purpose flour is made from a blend of soft and hard wheat. Durum wheat is a special variety of hard wheat, which is used to make a kind of flour called semolina. Semolina is most often used to make pasta.
Flour usually contains a small amount of additives. Bleaching agents such as benzoyl peroxide are added to make the flour more white. Oxidizing agents (also known as improvers) such as potassium bromate, chlorine dioxide, and azodicarbonamide are added to enhance the baking quality of the flour. These agents are added in a few parts per million. Self-rising flour contains salt and a leavening agent such as calcium phosphate. It is used to make baked goods without the need to add yeast or baking powder. Most states require flour to contain added vitamins and minerals to replace those lost during milling. The most important of these are iron and the B vitamins, especially thiamin, riboflavin, and niacin.
The Manufacturing Process
Preparing the wheat for grinding
Grinding the wheat
Processing the flour
A kernel of wheat consists of three parts, two of which can be considered byproducts of the milling process. The bran is the outer covering of the kernel and is high in fiber. The germ is the innermost portion of the kernel and is high in fat. The endosperm makes up the bulk of the kernel and is high in proteins and carbohydrates. Whole wheat flour uses all parts of the kernel, but white flour uses only the endosperm.
Bran removed during milling is often added to breakfast cereals and baked goods as a source of fiber. It is also widely used in animal feeds. Wheat germ removed during milling is often used as a food supplement or as a source of edible vegetable oil. Like bran, it is also used in animal feeds.