Bran, also known as miller's bran, is the hard outer layers of

cereal grain A cereal is any grass cultivated for the edible components of its grain (botanically, a type of fruit called a caryopsis), composed of the endosperm, germ, and bran. Cereal grain crops are grown in greater quantities and provide more food ...

. It consists of the combined

aleurone Aleurone (from Greek ''aleuron'', flour) is a protein found in protein granules of maturing seeds and tubers. The term also describes one of the two major cell types of the endosperm, the aleurone layer. The aleurone layer is the outermost layer ...

and pericarp. Corn (maize) bran also includes the pedicel (tip cap). Along with germ, it is an integral part of whole grains, and is often produced as a byproduct of milling in the production of refined grains. Bran is present in cereal grain, including

rice Rice is the seed of the grass species '' Oryza sativa'' (Asian rice) or less commonly '' Oryza glaberrima'' (African rice). The name wild rice is usually used for species of the genera '' Zizania'' and ''Porteresia'', both wild and domestica ...

, corn (maize),

wheat Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeolog ...

, oats,

barley Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley ...

rye Rye (''Secale cereale'') is a grass grown extensively as a grain, a cover crop and a forage crop. It is a member of the wheat tribe (Triticeae) and is closely related to both wheat (''Triticum'') and barley (genus ''Hordeum''). Rye grain is u ...

and

millet Millets () are a highly varied group of small-seeded grasses, widely grown around the world as cereal crops or grains for fodder and human food. Most species generally referred to as millets belong to the tribe Paniceae, but some millets ...

. Bran is not the same as chaff, which is a coarser scaly material surrounding the grain but not forming part of the grain itself, and which is indigestible by humans. "chaff, which is indigestible for humans"

Composition

Bran is particularly rich in

dietary fiber Dietary fiber (in British English fibre) or roughage is the portion of plant-derived food that cannot be completely broken down by human digestive enzymes. Dietary fibers are diverse in chemical composition, and can be grouped generally by th ...

and essential fatty acids and contains significant quantities of

starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets ...

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respon ...

vitamin A vitamin is an organic molecule (or a set of molecules closely related chemically, i.e. vitamers) that is an essential micronutrient that an organism needs in small quantities for the proper functioning of its metabolism. Essential nut ...

s, and dietary minerals. It is also a source of phytic acid, an antinutrient that prevents nutrient absorption. The high oil content of bran makes it subject to rancidification, one of the reasons that it is often separated from the grain before storage or further processing. Bran is often heat-treated to increase its longevity.

Rice bran

Rice bran is a byproduct of the rice milling process (the conversion of brown rice to white rice), and it contains various antioxidants. A major rice bran fraction contains 12%–13% oil and highly unsaponifiable components (4.3%). This fraction contains tocotrienols (a form of vitamin E), gamma-oryzanol and beta-sitosterol; all these constituents may contribute to the lowering of the plasma levels of the various parameters of the lipid profile. Rice bran also contains a high level of dietary fibres ( beta-glucan,

pectin Pectin ( grc, πηκτικός ': "congealed" and "curdled") is a heteropolysaccharide, a structural acid contained in the primary lamella, in the middle lamella, and in the cell walls of terrestrial plants. The principal, chemical component o ...

and gum). It also contains ferulic acid, which is also a component of the structure of nonlignified cell walls. However, some research suggests there are levels of inorganic

arsenic Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, bu ...

present in rice bran. One study found the levels to be 20% higher than in contaminated drinking water.

Uses

Bran is often used to enrich breads (notably

muffin A muffin is an individually portioned baked product, however the term can refer to one of two distinct items: a part-raised flatbread (like a crumpet) that is baked and then cooked on a griddle (typically unsweetened), or an (often sweetened) ...

s) and

breakfast cereal Cereal, formally termed breakfast cereal (and further categorized as cold cereal or warm cereal), is a traditional breakfast food made from processed cereal grains. It is traditionally eaten as part of breakfast, or a snack food, primarily in ...

s, especially for the benefit of those wishing to increase their intake of dietary fiber. Bran may also be used for

pickling Pickling is the process of food preservation, preserving or extending the shelf life of food by either Anaerobic organism, anaerobic fermentation (food), fermentation in brine or immersion in vinegar. The pickling procedure typically affects th ...

('' nukazuke'') as in the '' tsukemono'' of Japan. Rice bran in particular finds many uses in Japan, where it is known as ''nuka'' (; ). Besides using it for pickling, Japanese people add it to the

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...

when boiling bamboo shoots, and use it for dish washing. In Kitakyushu City, it is called ''jinda'' and used for stewing fish, such as

sardine "Sardine" and "pilchard" are common names for various species of small, oily forage fish in the herring family Clupeidae. The term "sardine" was first used in English during the early 15th century, a folk etymology says it comes from the ...

. Rice bran is stuck to the surface of commercial ice blocks to prevent them from melting . Bran oil may be also extracted for use by itself for industrial purposes (such as in the paint industry), or as a

cooking oil Cooking oil is plant, animal, or synthetic liquid fat used in frying, baking, and other types of cooking. It is also used in food preparation and flavoring not involving heat, such as salad dressings and bread dips, and may be called edible oi ...

, such as rice bran oil. Wheat bran is useful as feed for poultry and other

livestock Livestock are the domesticated animals raised in an agricultural setting to provide labor and produce diversified products for consumption such as meat, eggs, milk, fur, leather, and wool. The term is sometimes used to refer solely to anima ...

, as part of a balanced ration with other inputs. Wheatings, a milling byproduct comprising mostly bran with some pieces of endosperm also left over, are included in this category. Bran was found to be the most successful slug deterrent by BBC's TV programme '' Gardeners' World''. It is a common substrate and food source used for feeder insects, such as

mealworms Mealworms are the larval form of the yellow mealworm beetle, ''Tenebrio molitor'', a species of darkling beetle. Like all holometabolic insects, they go through four life stages: egg, larva, pupa, and adult. Larvae typically measure about or ...

and

waxworms Waxworms are the caterpillar larvae of wax moths, which belong to the family Pyralidae (snout moths). Two closely related species are commercially bred – the lesser wax moth (''Achroia grisella'') and the greater wax moth (''Galle ...

. Wheat bran has also been used for tanning leather since at least the 16th century.

Brewing

George Washington had a recipe for small beer involving bran,

hops Hops are the flowers (also called seed cones or strobiles) of the hop plant '' Humulus lupulus'', a member of the Cannabaceae family of flowering plants. They are used primarily as a bittering, flavouring, and stability agent in beer, to wh ...

, and

molasses Molasses () is a viscous substance resulting from refining sugarcane or sugar beets into sugar. Molasses varies in the amount of sugar, method of extraction and age of the plant. Sugarcane molasses is primarily used to sweeten and flavour foods ...

Research

As with cereal fibre and whole grain consumption, bran is under preliminary research for the potential to improve nutrition and affect chronic diseases.

Stability

It is common practice to heat-treat bran with the intention of slowing undesirable rancidification. However, a very detailed 2003 study of heat-treatment of oat bran found a complex pattern whereby increasingly intense heat treatment reduced the development of hydrolytic rancidity and bitterness with time, but increased oxidative rancidity. The authors recommended that heat treatment should be sufficient to achieve selective lipase inactivation, but not so much as to render the polar lipids oxidisable upon prolonged storage. See figure 1 in particular

References

{{Authority control Cereals Food ingredients Oats