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{{short description|Hard outer layers of cereal grain}}
[[File:Wheat bran structure.gif|thumb|300x300px|Wheat bran structure (E: outer layer; I: intermediate layer; A: aleurone layer).]]
'''Bran''', also known as '''miller's bran''', is the hard layers of [[Cereal|cereal grain]] surrounding the [[endosperm]]. It consists of the combined [[aleurone]] and [[Fruit anatomy#Pericarp layers|pericarp]]. Corn (maize) bran also includes the pedicel (tip cap). Along with the [[cereal germ|germ]], it is an integral part of [[whole grain]]s, and is often produced as a [[byproduct]] of milling in the production of [[refined grains]].

Bran is present in cereal grain, including [[rice]], [[maize|corn (maize)]], [[wheat]], [[oat]]s, [[barley]], [[rye]], and [[millet]]. Bran is not the same as [[chaff]], which is a coarser, scaly material surrounding the grain, but does not form part of the grain itself, and which is indigestible by humans.

==Composition==

Bran is particularly rich in [[dietary fiber]] and [[essential fatty acids]], and contains significant quantities of [[starch]], [[protein]], [[vitamin]]s, and [[dietary mineral]]s. 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 shelf life.

{| class="wikitable"
|-
! align="center" | Nutrients (%)
! [[Wheat]]
! [[Rye]]
! [[Oat]]
! [[Rice]]
! [[Barley]]
|-
| |[[Carbohydrate|Carbohydrates]] (excluding starch)
|  align="center" |45–50
|  align="center" |50–70
|  align="center" |16–34
|  align="center" |18–23
|  align="center" |70–80
|-
|| [[Starch]]
|  align="center" |13–18
|  align="center" |12–15
|  align="center" |18–45
|  align="center" |18–30
|  align="center" |8–11
|-
| | [[Protein]]s
|  align="center" |15–18
|  align="center" |8–9
|  align="center" |13–20
|  align="center" |15–18
|  align="center" | 11–15
|-
| | [[Fat]]s
|  align="center" |4–5
|  align="center" |4–5
|  align="center" |6–11
|  align="center" |18–23
|  align="center" |1–2
|}

== Rice bran ==
Rice bran is a byproduct of the rice-milling process (the conversion of [[brown rice]] to [[white rice]]), and it contains various [[antioxidant]]s. A major rice bran fraction contains 12%–13% oil and highly [[unsaponifiable]] components (4.3%).{{Citation needed|date=May 2009}} This fraction contains [[tocotrienol]]s (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 fiber ([[beta-glucan]], [[pectin]], and gum). It also contains [[ferulic acid]], which is also a component of the structure of nonlignified [[Plant cell|cell]] walls. Some research suggests, though, inorganic [[arsenic]] is present at some level in rice bran. One study found the levels to be 20% higher than in contaminated drinking water.

==Uses==
[[File:Rice bran.jpg|thumb|Rice bran]]
[[File:WheatBran.jpg|thumb|Wheat bran]]
[[File:Salvado de avena.jpg|thumb|Oat bran]]
Bran is often used to enrich [[bread]]s (notably [[muffin]]s) and [[breakfast cereal]]s, especially for the benefit of those wishing to increase their intake of [[dietary fiber]]. Bran may also be used for [[pickling]] (''[[nukazuke]]'') as in the ''[[tsukemono]]'' of [[Japan]].   Rice bran in particular finds many uses in Japan, where it is known as ''nuka'' ({{lang|ja|糠}}; {{lang|ja|ぬか}}). Besides using it for pickling, Japanese people add it to the [[water]] when [[boiling]] [[bamboo shoot]]s, and use it for [[dish washing]]. In [[Kitakyushu, Fukuoka|Kitakyushu]] City, it is called ''jinda'' and used for stewing fish, such as [[sardines]].

Rice bran is stuck to the surface of commercial ice blocks to prevent them from melting.{{fact|date=March 2020}} Bran oil may be also extracted for use by itself for industrial purposes (such as in the paint industry), or as a [[cooking oil]], such as [[rice bran oil]].

{{Anchor|Wheatings}} Wheat bran is useful as [[animal feed|feed]] for [[poultry]] and other [[livestock]], 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]] and [[waxworms]]. Wheat bran has also been used for tanning leather since at least the 16th century.

==Research==

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

==Stability==
Commonly, bran is heat-treated with the intention of slowing undesirable rancidification, but 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 oxidizable upon prolonged storage.

==See also==
* [[Alkylresorcinols]]
* [[Cereal germ]]
* [[Phytic acid]] (IP6)
* [[Rice bran solubles]]
* [[Raisin bran]]

==References==
{{reflist}}
{{commonscat}}
{{Barley}}
{{Wheat}}
{{Authority control}}

[[Category:Cereals]]
[[Category:Food ingredients]]
[[Category:Oats]]
[[Category:By-products]]