Bran

Last updated

Wheat bran structure (E: outer layer; I: intermediate layer; A: aleurone layer) Wheat bran structure.gif
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 grain surrounding the endosperm. It consists of the combined aleurone and pericarp. Corn (maize) bran also includes the pedicel (tip cap). [1] Along with the germ, it is an integral part of whole grains, and is often produced as a byproduct of milling in the production of refined grains.

Contents

Bran is present in cereal grain, including rice, corn (maize), wheat, oats, 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. [2]

Composition

Bran is particularly rich in dietary fiber and essential fatty acids, and contains significant quantities of starch, protein, vitamins, 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 shelf life.

Nutrients (%) Wheat Rye Oat Rice Barley
Carbohydrates (excluding starch)45–5050–7016–3418–2370–80
Starch 13–1812–1518–4518–308–11
Proteins 15–188–913–2015–1811–15
Fats 4–54–56–1118–231–2

Rice bran

Rice bran is a byproduct of the rice-milling process (the conversion of brown rice to white rice), and it contains various antioxidants. A major rice bran fraction contains 12%–13% oil and highly unsaponifiable components (4.3%).[ citation needed ] 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 fiber (beta-glucan, pectin, and gum). It also contains ferulic acid, which is also a component of the structure of nonlignified 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. [3]

Uses

Rice bran Rice bran.jpg
Rice bran
Wheat bran WheatBran.jpg
Wheat bran
Oat bran Salvado de avena.jpg
Oat bran

Bran is often used to enrich breads (notably muffins) and breakfast cereals, 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 (; ぬか). Besides using it for pickling, Japanese people add it to the water when boiling bamboo shoots, and use it for dish washing. In 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.[ citation needed ] 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.

Wheat bran is useful as 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. [4]

Research

As with cereal fiber and whole grain consumption, bran is under preliminary research for the potential to improve nutrition and affect chronic diseases. [5] [6]

Stability

Commonly, bran is heat-treated with the intention of slowing undesirable rancidification, but a 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. [7]

See also

Related Research Articles

<span class="mw-page-title-main">Oat</span> Cool weather staple grain, animal feed

The oat, sometimes called the common oat, is a species of cereal grain grown for its seed, which is known by the same name. Oats are used for human consumption as oatmeal, including as steel cut oats or rolled oats. Oats are a nutrient-rich food associated with lower blood cholesterol and reduced risk of human heart disease when consumed regularly. One of the most common uses of oats is as livestock feed.

<span class="mw-page-title-main">Flour</span> Cereal grains ground into powder

Flour is a powder made by grinding raw grains, roots, beans, nuts, or seeds. Flours are used to make many different foods. Cereal flour, particularly wheat flour, is the main ingredient of bread, which is a staple food for many cultures. Corn flour has been important in Mesoamerican cuisine since ancient times and remains a staple in the Americas. Rye flour is a constituent of bread in both Central Europe and Northern Europe.

<span class="mw-page-title-main">Dietary fiber</span> Portion of plant-derived food that cannot be completely digested

Dietary fiber 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 their solubility, viscosity, and fermentability, which affect how fibers are processed in the body. Dietary fiber has two main components: soluble fiber and insoluble fiber, which are components of plant-based foods, such as legumes, whole grains and cereals, vegetables, fruits, and nuts or seeds. A diet high in regular fiber consumption is generally associated with supporting health and lowering the risk of several diseases. Dietary fiber consists of non-starch polysaccharides and other plant components such as cellulose, resistant starch, resistant dextrins, inulin, lignins, chitins, pectins, beta-glucans, and oligosaccharides.

<span class="mw-page-title-main">Breakfast cereal</span> Processed food made from grain

Breakfast cereal is a breakfast food made from processed cereal grains. It is traditionally eaten as part of breakfast, or a snack food, primarily in Western societies.

Rancidification is the process of complete or incomplete autoxidation or hydrolysis of fats and oils when exposed to air, light, moisture, or bacterial action, producing short-chain aldehydes, ketones and free fatty acids.

<span class="mw-page-title-main">Sprouting</span> Practice of germinating seeds to be eaten raw or cooked

Sprouting is the natural process by which seeds or spores germinate and put out shoots, and already established plants produce new leaves or buds, or other structures experience further growth.

Wheat flour is a powder made from the grinding of wheat used for human consumption. Wheat varieties are called "soft" or "weak" if gluten content is low, and are called "hard" or "strong" if they have high gluten content. Hard flour, or bread flour, is high in gluten, with 12% to 14% gluten content, and its dough has elastic toughness that holds its shape well once baked. Soft flour is comparatively low in gluten and thus results in a loaf with a finer, crumbly texture. Soft flour is usually divided into cake flour, which is the lowest in gluten, and pastry flour, which has slightly more gluten than cake flour.

Enriched flour is flour with specific nutrients added to it. These nutrients include iron and B vitamins. Calcium may also be supplemented. The purpose of enriching flour is to replenish the nutrients in the flour to match the nutritional status of the unrefined product. This differentiates enrichment from fortification, which is the process of introducing new nutrients to a food.

<span class="mw-page-title-main">Cereal germ</span> Reproductive part of a grass seed

The germ of a cereal grain is the part that develops into a plant; it is the seed embryo. Along with bran, germ is often a by-product of the milling that produces refined grain products. Cereal grains and their components, such as wheat germ oil, rice bran oil, and maize bran, may be used as a source from which vegetable oil is extracted, or used directly as a food ingredient. The germ is retained as an integral part of whole-grain foods. Non-whole grain methods of milling are intended to isolate the endosperm, which is ground into flour, with removal of both the husk (bran) and the germ. Removal of bran produces a flour with a white rather than a brown color and eliminates fiber. The germ is rich in polyunsaturated fats and so germ removal improves the storage qualities of flour.

<span class="mw-page-title-main">Phytic acid</span> Chemical compound

Phytic acid is a six-fold dihydrogenphosphate ester of inositol, also called inositol hexaphosphate, inositol hexakisphosphate (IP6) or inositol polyphosphate. At physiological pH, the phosphates are partially ionized, resulting in the phytate anion.

<span class="mw-page-title-main">Whole grain</span> Cereal containing endosperm, germ, and bran

A whole grain is a grain of any cereal and pseudocereal that contains the endosperm, germ, and bran, in contrast to refined grains, which retain only the endosperm.

<span class="mw-page-title-main">Alkylresorcinol</span> Class of chemical compounds

Alkylresorcinols (ARs), also known as resorcinolic lipids, are amphiphilic phenolic lipids characterised by a non-polar odd-numbered alkyl side chain with up to 27 carbon atoms attached to a polar resorcinol (1,3-dihydroxybenzene) ring.

<span class="mw-page-title-main">Rolled oats</span> Food made from oat groats

Rolled oats are a type of lightly processed whole-grain food. They are made from oat groats that have been dehusked and steamed, before being rolled into flat flakes under heavy rollers and then stabilized by being lightly toasted.

Aleurone 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 of the endosperm, followed by the inner starchy endosperm. This layer of cells is sometimes referred to as the peripheral endosperm. It lies between the pericarp and the hyaline layer of the endosperm. Unlike the cells of the starchy endosperm, aleurone cells remain alive at maturity. The ploidy of the aleurone is (3n) [as a result of double fertilization].

<span class="mw-page-title-main">Refined grains</span> Cereal containing endosperm, but not bran nor germ

Refined grains have been significantly modified from their natural composition, in contrast to whole grains. The modification process generally involves the mechanical removal of bran and germ, either through grinding or selective sifting.

Wheat middlings are the product of the wheat milling process that is not flour. A good source of protein, fiber, phosphorus, and other nutrients, they are a useful fodder for livestock and pets. They are also being researched for use as a biofuel.

Fibre supplements are considered to be a form of a subgroup of functional dietary fibre, and in the United States are defined by the Institute of Medicine (IOM). According to the IOM, functional fibre "consists of isolated, non-digestible carbohydrates that have beneficial physiological effects in humans".

A Unifine mill is a single one-pass impact milling system which produces ultrafine-milled whole-grain wheat flour that requires no grain pre-treatment and no screening of the flour. Like the grist or stone mills that had dominated the flour industry for centuries, the bran, germ, and endosperm elements of grain are processed into a nutritious whole wheat flour in one step. Consumers had accepted whole wheat products produced by grist or stone mills. The flour produced by these mills was quite coarse as they included the bran and the germ elements of the grain.

In agriculture, grain quality depends on the use of the grain. In ethanol production, the chemical composition of grain such as starch content is important, in food and feed manufacturing, properties such as protein, oil and sugar are significant, in the milling industry, soundness is the most important factor to consider when it comes to the quality of grain. For grain farmers, high germination percentage and seed dormancy are the main features to consider. For consumers, properties such as color and flavor are most important.

The Roller Mill was created by Hungarian bakers in the late 1860s and its popularity spread worldwide throughout the 1900s. Roller mills now produce almost all non-whole grain flour. Enriched flour is flour that meets an FDA standard in the United States. Roller milled white enriched flour makes up over 90% of the flour that comes out of the United States.

References

  1. Corn Chemistry and Technology Watson and Ramstad 1987 p. 69
  2. Catsberg, C. M. E. (1990). Food Handbook. Dordrecht: Springer Netherlands. doi:10.1007/978-94-009-0445-3_15. ISBN   978-94-009-0445-3. "chaff, which is indigestible for humans"
  3. "Inorganic Arsenic in Rice Bran and Its Products Are an Order of Magnitude Higher than in Bulk Grain". Environmental Science & Technology. Pubs.acs.org. 21 August 2008. Retrieved 9 February 2010.
  4. Rossetti, Gioanventura (1969). the plictho . Massachusetts: The Massachusetts Institute of Technology. pp.  159–160. ISBN   978-0262180306.
  5. Barrett EM, Batterham MJ, Ray S, Beck EJ. (2019). "Whole grain, bran and cereal fibre consumption and CVD: a systematic review". British Journal of Nutrition. 121 (8): 914–937. doi: 10.1017/S000711451900031X . PMID   30761962. S2CID   73449809.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  6. Jefferson, A., & Adolphus, K. (2020). "The Effects of Increasing Intake of Intact Wheat Fibre or Wheat Bran on Gut Microbiota Diversity: A Systematic Review". Proceedings of the Nutrition Society. 79 (OCE2): E531. doi: 10.1017/S0029665120004802 .{{cite journal}}: CS1 maint: multiple names: authors list (link)
  7. Lehtinen, Pekka; Kiiliäinen, Katja; Lehtomäki, Ilkka; Laakso, Simo (2003). "Effect of Heat Treatment on Lipid Stability in Processed Oats". Journal of Cereal Science. 37 (2): 215–221. doi:10.1006/jcrs.2002.0496. ISSN   0733-5210. See figure 1 in particular