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Starch

Starch

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Starch or amylum is a carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...

 consisting of a large number of glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

 units joined together by glycosidic bond
Glycosidic bond
In chemistry, a glycosidic bond is a type of covalent bond that joins a carbohydrate molecule to another group, which may or may not be another carbohydrate....

s. This polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...

 is produced by all green plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s as an energy store. It is the most common carbohydrate in the human diet and is contained in large amounts in such staple food
Staple food
A staple food is one that is eaten regularly and in such quantities that it constitutes a dominant portion of a diet, and that supplies a high proportion of energy and nutrient needs. Most people live on a diet based on one or more staples...

s as potato
Potato
The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...

es, wheat
Wheat
Wheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...

, maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...

 (corn), rice
Rice
Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...

, and cassava
Cassava
Cassava , also called yuca or manioc, a woody shrub of the Euphorbiaceae native to South America, is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates...

.

Pure starch is a white, tasteless and odorless powder that is insoluble in cold water or alcohol.
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Starch or amylum is a carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...

 consisting of a large number of glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

 units joined together by glycosidic bond
Glycosidic bond
In chemistry, a glycosidic bond is a type of covalent bond that joins a carbohydrate molecule to another group, which may or may not be another carbohydrate....

s. This polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...

 is produced by all green plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s as an energy store. It is the most common carbohydrate in the human diet and is contained in large amounts in such staple food
Staple food
A staple food is one that is eaten regularly and in such quantities that it constitutes a dominant portion of a diet, and that supplies a high proportion of energy and nutrient needs. Most people live on a diet based on one or more staples...

s as potato
Potato
The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...

es, wheat
Wheat
Wheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...

, maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...

 (corn), rice
Rice
Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...

, and cassava
Cassava
Cassava , also called yuca or manioc, a woody shrub of the Euphorbiaceae native to South America, is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates...

.

Pure starch is a white, tasteless and odorless powder that is insoluble in cold water or alcohol. It consists of two types of molecules: the linear and helical
Helix
A helix is a type of smooth space curve, i.e. a curve in three-dimensional space. It has the property that the tangent line at any point makes a constant angle with a fixed line called the axis. Examples of helixes are coil springs and the handrails of spiral staircases. A "filled-in" helix – for...

 amylose
Amylose
Amylose is a linear polymer made up of D-glucose units.This polysaccharide is one of the two components of starch, making up approximately 2-30% of the structure...

 and the branched amylopectin
Amylopectin
Amylopectin is a soluble polysaccharide and highly branched polymer of glucose found in plants. It is one of the two components of starch, the other being amylose.Glucose units are linked in a linear way with α glycosidic bonds...

.
Depending on the plant, starch generally contains 20 to 25% amylose and 75 to 80% amylopectin. Glycogen
Glycogen
Glycogen is a molecule that serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue...

, the glucose store of animals, is a more branched version of amylopectin.

Starch is processed to produce many of the sugars in processed foods. Dissolving starch in warm water gives wheatpaste
Wheatpaste
Wheatpaste is a liquid adhesive made from vegetable starch and water. It has been used since ancient times for various arts and crafts such as book binding, decoupage, collage, and papier-mâché...

 that can be used as a thickening, stiffening or gluing agent. The biggest industrial non-food use of starch is as adhesive in the papermaking
Papermaking
Papermaking is the process of making paper, a substance which is used universally today for writing and packaging.In papermaking a dilute suspension of fibres in water is drained through a screen, so that a mat of randomly interwoven fibres is laid down. Water is removed from this mat of fibres by...

 process.

Name


The word "starch" is derived
Etymology
Etymology is the study of the history of words, their origins, and how their form and meaning have changed over time.For languages with a long written history, etymologists make use of texts in these languages and texts about the languages to gather knowledge about how words were used during...

 from Middle English
Middle English
Middle English is the stage in the history of the English language during the High and Late Middle Ages, or roughly during the four centuries between the late 11th and the late 15th century....

 sterchen, meaning to stiffen. "amylum" is Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 for starch, from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 αμυλον, "amylon" which means "not ground at a mill". The root amyl
Amyl
The word or root amyl has two meanings, in organic chemistry and biochemistry.-Biochemistry:In biochemistry, "amyl" means "pertaining to starch", "amylum" being another word for starch...

 is used in biochemistry for several compounds related to starch.

History


Starch grains from the rhizome
Rhizome
In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...

s of Typha
Typha
Typha is a genus of about eleven species of monocotyledonous flowering plants in the family Typhaceae. The genus has a largely Northern Hemisphere distribution, but is essentially cosmopolitan, being found in a variety of wetland habitats...

(cattails, bullrushes) as flour
Flour
Flour is a powder which is made by grinding cereal grains, other seeds or roots . It is the main ingredient of bread, which is a staple food for many cultures, making the availability of adequate supplies of flour a major economic and political issue at various times throughout history...

 have been identified from grinding stone
Grinding Stone
Grinding Stone is a 1973 debut album by Gary Moore, released under the "The Gary Moore Band" moniker.-Track listing:All songs by Gary Moore.# "Grinding Stone" – 9:38# "Time to Heal" - 6:19# "Sail Across the Mountain" - 6:58...

s in Europe dating back to 30,000 years ago.

Pure extracted wheat starch paste was used in Ancient Egypt
Ancient Egypt
Ancient Egypt was an ancient civilization of Northeastern Africa, concentrated along the lower reaches of the Nile River in what is now the modern country of Egypt. Egyptian civilization coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh...

 possibly to glue papyrus
Papyrus
Papyrus is a thick paper-like material produced from the pith of the papyrus plant, Cyperus papyrus, a wetland sedge that was once abundant in the Nile Delta of Egypt....

. The extraction of starch is first described in the Natural History of Pliny the Elder
Pliny the Elder
Gaius Plinius Secundus , better known as Pliny the Elder, was a Roman author, naturalist, and natural philosopher, as well as naval and army commander of the early Roman Empire, and personal friend of the emperor Vespasian...

 around AD 77-79. Romans used it also in cosmetic creams, to powder the hair and to thicken sauces. Persians and Indians used it to make dishes similar to gothumai wheat halva
Halva
Halva refers to many types of dense, sweet confections, served across the Middle East, South Asia, Central Asia, West Asia, North Africa, the Horn of Africa, the Balkans, Eastern Europe, Malta and the Jewish world.The term halva ,...

. Rice starch as surface treatment of paper has been used in paper production in China, from 700 AD onwards.

In addition to starchy plants consumed directly, 66 million tonnes of starch were being produced per year world-wide by 2008. In the EU this was around 8.5 million tonnes, with around
40% being used for industrial applications and 60% for food uses, most of which as glucose syrup
Glucose syrup
Glucose syrup is a food syrup, made from the hydrolysis of starch. Maize is commonly used as the source of the starch in the USA, in which case the syrup is called "corn syrup", but glucose syrup is also made from other starch crops, including potatoes, wheat, barley, rice and cassavap.21...

s.

Energy store of plants


In photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

, plants use light energy to produce glucose from carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

. The glucose is stored mainly in the form of starch granules, in plastid
Plastid
Plastids are major organelles found in the cells of plants and algae. Plastids are the site of manufacture and storage of important chemical compounds used by the cell...

s such as chloroplast
Chloroplast
Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.Chloroplasts are green...

s and especially amyloplast
Amyloplast
Amyloplasts are non-pigmented organelles found in some plant cells. They are responsible for the synthesis and storage of starch granules, through the polymerization of glucose. Amyloplasts also convert this starch back into sugar when the plant needs energy...

s. Toward the end of the growing season, starch accumulates in twigs of trees near the buds. Fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

, seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...

s, rhizome
Rhizome
In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...

s, and tuber
Tuber
Tubers are various types of modified plant structures that are enlarged to store nutrients. They are used by plants to survive the winter or dry months and provide energy and nutrients for regrowth during the next growing season and they are a means of asexual reproduction...

s store starch to prepare for the next growing season.

Glucose is soluble in water, hydrophilic, binds much water and then takes up much space; glucose in the form of starch, on the other hand, is not soluble and can be stored much more compactly.

Glucose molecules are bound in starch by the easily hydrolyzed alpha bonds. The same type of bond can also be seen in the animal reserve polysaccharide glycogen. This is in contrast to many structural polysaccharides such as chitin
Chitin
Chitin n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world...

, cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

 and peptidoglycan
Peptidoglycan
Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of bacteria , forming the cell wall. The sugar component consists of alternating residues of β- linked N-acetylglucosamine and N-acetylmuramic acid...

, which are bound by beta-bonds and are much more resistant to hydrolysis.

Biosynthesis


Plants produce starch by first converting glucose 1-phosphate to ADP
Adenosine diphosphate
Adenosine diphosphate, abbreviated ADP, is a nucleoside diphosphate. It is an ester of pyrophosphoric acid with the nucleoside adenosine. ADP consists of the pyrophosphate group, the pentose sugar ribose, and the nucleobase adenine....

-glucose using the enzyme glucose-1-phosphate adenylyltransferase
Glucose-1-phosphate adenylyltransferase
In enzymology, a glucose-1-phosphate adenylyltransferase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are ATP and alpha-D-glucose 1-phosphate, whereas its two products are diphosphate and ADP-glucose....

. This step requires energy in the form of ATP
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...

. The enzyme starch synthase
Starch synthase
In enzymology, a starch synthase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are ADP-glucose and a chain of D-glucose residues joined by 1,4-alpha-glycosidic bonds, whereas its two products are ADP and an elongated chain of glucose residues...

 then adds the ADP-glucose via a 1,4-alpha glycosidic bond
Glycosidic bond
In chemistry, a glycosidic bond is a type of covalent bond that joins a carbohydrate molecule to another group, which may or may not be another carbohydrate....

 to a growing chain of glucose residues, liberating ADP
Adenosine diphosphate
Adenosine diphosphate, abbreviated ADP, is a nucleoside diphosphate. It is an ester of pyrophosphoric acid with the nucleoside adenosine. ADP consists of the pyrophosphate group, the pentose sugar ribose, and the nucleobase adenine....

 and creating amylose. Starch branching enzyme introduces 1,6-alpha glycosidic bonds between these chains, creating the branched amylopectin. The starch debranching enzyme isoamylase removes some of these branches. Several isoforms of these enzymes exist, leading to a highly complex synthesis process.

While amylose was traditionally thought to be completely unbranched, it is now known that some of its molecules contain a few branch points.

Glycogen and amylopectin have the same structure, but the former has about one branch point per ten 1,4-alpha bonds, compared to about one branch point per thirty 1,4-alpha bonds in amylopectin. Another difference is that glycogen is synthesised from UDP-glucose
Uridine diphosphate glucose
Uridine diphosphate glucose is a nucleotide sugar. It is involved in glycosyltransferase reactions in metabolism.-Functions:...

 while starch is synthesised from ADP-glucose.

Structure


Starch molecules arrange themselves in the plant in semi-crystalline granules. Each plant species has a unique starch granular size: rice starch is relatively small (about 2μm) while potato starch
Potato starch
Potato starch is starch extracted from potatoes. The cells of the root tubers of the potato plant contain starch grains . To extract the starch, the potatoes are crushed; the starch grains are released from the destroyed cells...

es have larger granules (up to 100μm). Although in absolute mass only about one quarter of the starch granules in plants consist of amylose, there are about 150 times more amylose molecules than amylopectin molecules. Amylose is a much smaller molecule than amylopectin.

Starch becomes soluble in water when heated. The granules swell and burst, the semi-crystalline structure is lost and the smaller amylose molecules start leaching out of the granule, forming a network that holds water and increasing the mixture's viscosity
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...

. This process is called starch gelatinization
Starch gelatinization
Starch gelatinization is a process that breaks down the intermolecular bonds of starch molecules in the presence of water and heat, allowing the hydrogen bonding sites to engage more water. This irreversibly dissolves the starch granule...

. During cooking the starch becomes a paste and increases further in viscosity. During cooling or prolonged storage of the paste, the semi-crystalline structure partially recovers and the starch paste thickens, expelling water. This is mainly caused by the retrogradation
Retrogradation (starch)
Retrogradation is a reaction that takes place in gelatinized starch when the amylose and amylopectin chains realign themselves, causing the liquid to gel....

 of the amylose. This process is responsible for the hardening of bread or staling
Staling
Staling, or "going stale", is a chemical and physical process in bread and other foods that reduces their palatability. Stale bread is dry and leathery.-Mechanism and effects:...

, and for the water layer on top of a starch gel (syneresis
Syneresis (chemistry)
Syneresis , in chemistry, is the extraction or expulsion of a liquid from a gel, as when lymph drains from a contracting clot of blood. Another example of syneresis is the collection of whey on the surface of yogurt...

).

Some cultivated plant varieties have pure amylopectin starch without amylose, known as waxy starches. The most used is waxy maize
Waxy corn
Waxy corn was found in China in 1909. As this plant showed many peculiar traits, the American breeders long used it as a genetic marker to tag the existence of hidden genes in other maize breeding programs...

, others are glutinous rice
Glutinous rice
Glutinous rice is a type of short-grained Asian rice that is especially sticky when cooked. It is called glutinous Glutinous rice (Oryza sativa var. glutinosa or Oryza glutinosa; also called sticky rice, sweet rice, waxy rice, botan rice, biroin chal, mochi rice, and pearl rice, and pulut) is a...

 and waxy potato starch
Waxy potato starch
Waxy potato starch is a new species of starch only containing amylopectin molecules, extracted from new potato varieties. Standard starch extracted from traditional potato varieties contains both amylose and amylopectin....

. Waxy starches have less retrogradation, resulting in a more stable paste. High amylose starch, amylomaize
Amylomaize
Amylomaize was a term coined by Robert P. Bear of Bear Hybrids Corn Company in Decatur, Illinois to describe his discovery and commercial breeding of a unique cornstarch with high amylose content, also called high amylose starch...

, is cultivated for the use of its gel strength.

Hydrolysis


The enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s that break down or hydrolyze
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...

 starch into the constituent sugars are known as amylase
Amylase
Amylase is an enzyme that catalyses the breakdown of starch into sugars. Amylase is present in human saliva, where it begins the chemical process of digestion. Food that contains much starch but little sugar, such as rice and potato, taste slightly sweet as they are chewed because amylase turns...

s.

Alpha-amylases are found in plants and in animals. Human saliva
Saliva
Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...

 is rich in amylase, and the pancreas
Pancreas
The pancreas is a gland organ in the digestive and endocrine system of vertebrates. It is both an endocrine gland producing several important hormones, including insulin, glucagon, and somatostatin, as well as a digestive organ, secreting pancreatic juice containing digestive enzymes that assist...

 also secretes the enzyme. Individuals from populations with a high-starch diet tend to have more amylase genes than those with low-starch diets; chimpanzee
Chimpanzee
Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...

s have very few amylase genes. It is possible that turning to a high-starch diet was a significant event in human evolution.

Beta-amylase cuts starch into maltose
Maltose
Maltose , or malt sugar, is a disaccharide formed from two units of glucose joined with an αbond, formed from a condensation reaction. The isomer "isomaltose" has two glucose molecules linked through an α bond. Maltose is the second member of an important biochemical series of glucose chains....

 units. This process is important in the digestion of starch and is also used in brewing
Brewing
Brewing is the production of beer through steeping a starch source in water and then fermenting with yeast. Brewing has taken place since around the 6th millennium BCE, and archeological evidence suggests that this technique was used in ancient Egypt...

, where the amylase from the skin of the seed grains is responsible for converting starch to maltose (Malting, Mashing
Mashing
In brewing and distilling, mashing is the process of combining a mix of milled grain , known as the "grain bill", and water, known as "liquor", and heating this mixture...

).

Dextrinization


If starch is subjected to dry heat, it breaks down to form dextrin
Dextrin
Dextrins are a group of low-molecular-weight carbohydrates produced by the hydrolysis of starch or glycogen. Dextrins are mixtures of polymers of D-glucose units linked by α- or α- glycosidic bonds....

s, also called "pyrodextrins" in this context. This break down process is known as dextrinization. (Pyro)dextrins are mainly yellow to brown in color and dextrinization is partially responsible for the browning of toasted bread.

Chemical tests



Iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

 solution is used to test for starch; a dark blue color indicates the presence of starch. The details of this reaction are not yet fully known, but it is thought that the iodine (I3 and I5 ions) fit inside the coils of amylose
Amylose
Amylose is a linear polymer made up of D-glucose units.This polysaccharide is one of the two components of starch, making up approximately 2-30% of the structure...

, the charge transfers between the iodine and the starch, and the energy level spacings in the resulting complex correspond to the absorption spectrum in the visible light region. The strength of the resulting blue color depends on the amount of amylose present. Waxy starches with little or no amylose present will color red.

Starch indicator
Starch indicator
Starch is often used in chemistry as an indicator for redox titrations where triiodide is present. Starch forms a very dark blue-black complex with triiodide which can be made by mixing iodine with iodide . However, the complex is not formed if only iodine or only iodide is present...

 solution consisting of water, starch and iodine is often used in redox
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

 titrations: in the presence of an oxidizing agent
Oxidizing agent
An oxidizing agent can be defined as a substance that removes electrons from another reactant in a redox chemical reaction...

 the solution turns blue, in the presence of reducing agent
Reducing agent
A reducing agent is the element or compound in a reduction-oxidation reaction that donates an electron to another species; however, since the reducer loses an electron we say it is "oxidized"...

 the blue color disappears because triiodide
Triiodide
In chemistry, triiodide can have several meanings. Triiodide primarily refers to the triiodide ion, I3−, a polyatomic anion composed of three iodine atoms. For some chemical compounds, triiodide indicates a salt of the named cation with the triiodide anion. Examples include sodium triiodide, ...

 (I3) ions break up into three iodide ions, disassembling the starch-iodine complex.
A 0.3% w/w
Percentage solution
"Percentage solution" is an ambiguous term which is used to describe a solution with the unit "%". It may refer to:* Mass fraction if mass/mass is meant...

 solution is the standard concentration for a starch indicator. It is made by adding 3 grams of soluble starch to 1 liter of heated water; the solution is cooled before use (starch-iodine complex becomes unstable at temperatures above 35 °C).

Microscopy of starch granules - Each species of plant has a unique shape of starch granules in granular size, shape and crystallization pattern. Under the microscope
Microscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...

, starch grains stained with iodine illuminated from behind with polarized light show a distinctive Maltese cross
Maltese cross
The Maltese cross, also known as the Amalfi cross, is identified as the symbol of an order of Christian warriors known as the Knights Hospitaller or Knights of Malta and through them came to be identified with the Mediterranean island of Malta and is one of the National symbols of Malta...

 effect (also known as extinction cross
Extinction cross
The extinction cross is an optical phenomenon that is seen when trying to extinguish a laser beam or non-planar white light using crossed polarizers. Ideally, crossed polarizers block all light, since light which is polarized along the polarization axis of the first polarizer is perpendicular to...

 and birefringence
Birefringence
Birefringence, or double refraction, is the decomposition of a ray of light into two rays when it passes through certain anisotropic materials, such as crystals of calcite or boron nitride. The effect was first described by the Danish scientist Rasmus Bartholin in 1669, who saw it in calcite...

).

Food


Starch is the most common carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...

 in the human diet and is contained in many staple food
Staple food
A staple food is one that is eaten regularly and in such quantities that it constitutes a dominant portion of a diet, and that supplies a high proportion of energy and nutrient needs. Most people live on a diet based on one or more staples...

s. The major sources of starch intake worldwide are the cereals rice
Rice
Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...

, wheat
Wheat
Wheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...

, and maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...

, and the root vegetable
Root vegetable
Root vegetables are plant roots used as vegetables. Here "root" means any underground part of a plant.Root vegetables are generally storage organs, enlarged to store energy in the form of carbohydrates. They differ in the concentration and the balance between sugars, starches, and other types of...

s potato
Potato
The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...

es and cassava
Cassava
Cassava , also called yuca or manioc, a woody shrub of the Euphorbiaceae native to South America, is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates...

. Many other starchy foods are grown, some only in specific climates, including acorn
Acorn
The acorn, or oak nut, is the nut of the oaks and their close relatives . It usually contains a single seed , enclosed in a tough, leathery shell, and borne in a cup-shaped cupule. Acorns vary from 1–6 cm long and 0.8–4 cm broad...

s, arrowroot
Arrowroot
Arrowroot, or obedience plant , Bermuda arrowroot, araru, ararao, is a large perennial herb found in rainforest habitats...

, arracacha
Arracacha
The arracacha is a garden root vegetable originally from the Andes, somewhat intermediate between the carrot and celery...

, banana
Banana
Banana is the common name for herbaceous plants of the genus Musa and for the fruit they produce. Bananas come in a variety of sizes and colors when ripe, including yellow, purple, and red....

s, barley
Barley
Barley is a major cereal grain, a member of the grass family. It serves as a major animal fodder, as a base malt for beer and certain distilled beverages, and as a component of various health foods...

, breadfruit
Breadfruit
Breadfruit is a species of flowering tree in the mulberry family, Moraceae, growing throughout Southeast Asia and most Pacific Ocean islands...

, buckwheat
Buckwheat
Buckwheat refers to a variety of plants in the dicot family Polygonaceae: the Eurasian genus Fagopyrum, the North American genus Eriogonum, and the Northern Hemisphere genus Fallopia. Either of the latter two may be referred to as "wild buckwheat"...

, canna
Canna (plant)
Canna is a genus of nineteen species of flowering plants. The closest living relations to cannas are the other plant families of the order Zingiberales, that is the gingers, bananas, marantas, heliconias, strelitzias, etc.Canna is the only genus in the family Cannaceae...

, colacasia, katakuri, kudzu
Kudzu
Kudzu is a plant in the genus Pueraria in the pea family Fabaceae, subfamily Faboideae. It is a climbing, coiling, and trailing vine native to southern Japan and southeast China. Its name comes from the Japanese name for the plant, . It is a weed that climbs over trees or shrubs and grows so...

, malanga
Malanga
- Plants :* Xanthosoma, also known as Malanga, a tropical and sub-tropical edible or ornamental plant* Eddoe, also known as Malanga, a tropical vegetable- People :* Gerard Malanga , poet and photographer* Steven Malanga, author...

, millet
Millet
The millets are a group of small-seeded species of cereal crops or grains, widely grown around the world for food and fodder. They do not form a taxonomic group, but rather a functional or agronomic one. Their essential similarities are that they are small-seeded grasses grown in difficult...

, oat
Oat
The common oat is a species of cereal grain grown for its seed, which is known by the same name . While oats are suitable for human consumption as oatmeal and rolled oats, one of the most common uses is as livestock feed...

s, oca
Oca
Oxalis tuberosa is an herbaceous perennial plant that overwinters as underground stem tubers. These tubers are known as oca, oka, or New Zealand Yam. The plant was brought into cultivation in the central and southern Andes for its tubers, which are used as a root vegetable...

, polynesian arrowroot, sago
Sago
Sago is a starch extracted in the spongy center or pith, of various tropical palm stems, Metroxylon sagu. It is a major staple food for the lowland peoples of New Guinea and the Moluccas, where it is called saksak and sagu. A type of flour, called sago flour, is made from sago. The largest supply...

, sorghum
Sorghum
Sorghum is a genus of numerous species of grasses, one of which is raised for grain and many of which are used as fodder plants either cultivated or as part of pasture. The plants are cultivated in warmer climates worldwide. Species are native to tropical and subtropical regions of all continents...

, sweet potato
Sweet potato
The sweet potato is a dicotyledonous plant that belongs to the family Convolvulaceae. Its large, starchy, sweet-tasting, tuberous roots are an important root vegetable. The young leaves and shoots are sometimes eaten as greens. Of the approximately 50 genera and more than 1,000 species of...

es, rye
Rye
Rye is a grass grown extensively as a grain and as a forage crop. It is a member of the wheat tribe and is closely related to barley and wheat. Rye grain is used for flour, rye bread, rye beer, some whiskeys, some vodkas, and animal fodder...

, taro
Taro
Taro is a common name for the corms and tubers of several plants in the family Araceae . Of these, Colocasia esculenta is the most widely cultivated, and is the subject of this article. More specifically, this article describes the 'dasheen' form of taro; another variety is called eddoe.Taro is...

, chestnut
Chestnut
Chestnut , some species called chinkapin or chinquapin, is a genus of eight or nine species of deciduous trees and shrubs in the beech family Fagaceae, native to temperate regions of the Northern Hemisphere. The name also refers to the edible nuts they produce.-Species:The chestnut belongs to the...

s, water chestnut
Water chestnut
Water chestnut may refer to either of two plants :* The Chinese water chestnut , eaten for its crisp corm* The Water caltrop , eaten for its starchy seed...

s and yams
Yam (vegetable)
Yam is the common name for some species in the genus Dioscorea . These are perennial herbaceous vines cultivated for the consumption of their starchy tubers in Africa, Asia, Latin America and Oceania...

, and many kinds of bean
Bean
Bean is a common name for large plant seeds of several genera of the family Fabaceae used for human food or animal feed....

s, such as favas
Vicia faba
This article refers to the Broad Bean plant. For Broadbean the company, see Broadbean, Inc.Vicia faba, the Broad Bean, Fava Bean, Field Bean, Bell Bean or Tic Bean, is a species of bean native to north Africa and southwest Asia, and extensively cultivated elsewhere. A variety is provisionally...

, lentils, mung bean
Mung bean
The mung bean is the seed of Vigna radiata. It is native to the Indian subcontinent.-Description:They are small, ovoid in shape, and green in color...

s, peas
PEAS
P.E.A.S. is an acronym in artificial intelligence that stands for Performance, Environment, Actuators, Sensors.-Performance:Performance is a function that measures the quality of the actions the agent did....

, and chickpea
Chickpea
The chickpea is a legume of the family Fabaceae, subfamily Faboideae...

s.

Widely used prepared foods containing starch are bread
Bread
Bread is a staple food prepared by cooking a dough of flour and water and often additional ingredients. Doughs are usually baked, but in some cuisines breads are steamed , fried , or baked on an unoiled frying pan . It may be leavened or unleavened...

, pancake
Pancake
A pancake is a thin, flat, round cake prepared from a batter, and cooked on a hot griddle or frying pan. Most pancakes are quick breads; some use a yeast-raised or fermented batter. Most pancakes are cooked one side on a griddle and flipped partway through to cook the other side...

s, cereals, noodles, pasta
Pasta
Pasta is a staple food of traditional Italian cuisine, now of worldwide renown. It takes the form of unleavened dough, made in Italy, mostly of durum wheat , water and sometimes eggs. Pasta comes in a variety of different shapes that serve for both decoration and to act as a carrier for the...

, porridge
Porridge
Porridge is a dish made by boiling oats or other cereal meals in water, milk, or both. It is usually served hot in a bowl or dish...

 and tortilla
Tortilla
In Mexico and Central America, a tortilla is a type of thin, unleavened flat bread, made from finely ground maize...

.

Digestive
Digestion
Digestion is the mechanical and chemical breakdown of food into smaller components that are more easily absorbed into a blood stream, for instance. Digestion is a form of catabolism: a breakdown of large food molecules to smaller ones....

 enzymes have problems digesting crystalline structures. Raw starch will digest poorly in the duodenum
Duodenum
The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms anterior intestine or proximal intestine may be used instead of duodenum...

 and small intestine
Small intestine
The small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...

, while bacterial degradation will take place mainly in the colon
Colon (anatomy)
The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...

. Resistant starch
Resistant starch
Resistant starch is starch and starch degradation products that escape digestion in the small intestine of healthy individuals. Resistant starch is considered the third type of dietary fiber, as it can deliver some of the benefits of insoluble fiber and some of the benefits of soluble fiber.Some...

 is starch that escapes digestion in the small intestine of healthy individuals. In order to increase the digestibility, starch is cooked. Hence, before humans started using fire, eating grains was not a very useful way to get energy.

Starch gelatinization during cake baking can be impaired by sugar competing for water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

, preventing gelatinization and improving texture.

Starch industry


The starch industry extracts and refines starches from seeds, roots and tubers, by wet grinding, washing, sieving and drying. Today, the main commercial refined starches are cornstarch
Cornstarch
Corn starch, cornstarch, cornflour or maize starch is the starch of the corn grain obtained from the endosperm of the corn kernel.-History:...

, tapioca
Tapioca
Tapioca is a starch extracted Manihot esculenta. This species, native to the Amazon, Brazil, Colombia, Venezuela, Cuba, Puerto Rico, Haiti, the Dominican Republic, Honduras, and most of the West Indies, is now cultivated worldwide and has many names, including cassava, manioc, aipim,...

, wheat and potato starch
Potato starch
Potato starch is starch extracted from potatoes. The cells of the root tubers of the potato plant contain starch grains . To extract the starch, the potatoes are crushed; the starch grains are released from the destroyed cells...

. To a lesser extent, sources include rice, sweet potato, sago and mung bean. Historically, Florida arrowroot
Florida arrowroot
Florida arrowroot was the commercial name of an edible starch extracted from Zamia integrifolia , a small cycad native to North America.-Use:...

 was also commercialized. Starch is still extracted from more than 50 types of plants.

Untreated starch requires heat to thicken or gelatinize. When a starch is pre-cooked, it can then be used to thicken instantly in cold water. This is referred to as a pregelatinized starch
Starch gelatinization
Starch gelatinization is a process that breaks down the intermolecular bonds of starch molecules in the presence of water and heat, allowing the hydrogen bonding sites to engage more water. This irreversibly dissolves the starch granule...

.

Starch sugars


Starch can be hydrolyzed into simpler carbohydrates by acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

s, various enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s, or a combination of the two. The resulting fragments are known as dextrin
Dextrin
Dextrins are a group of low-molecular-weight carbohydrates produced by the hydrolysis of starch or glycogen. Dextrins are mixtures of polymers of D-glucose units linked by α- or α- glycosidic bonds....

s. The extent of conversion is typically quantified by dextrose equivalent
Dextrose equivalent
Dextrose equivalent is a measure of the amount of reducing sugars present in a sugar product, relative to glucose, expressed as a percentage on a dry basis. For example, a maltodextrin with a DE of 10 would have 10% of the reducing power of dextrose , while sucrose, with a DE of 120, would have...

(DE), which is roughly the fraction of the glycosidic bond
Glycosidic bond
In chemistry, a glycosidic bond is a type of covalent bond that joins a carbohydrate molecule to another group, which may or may not be another carbohydrate....

s in starch that have been broken.

These starch sugars are by far the most common starch based food ingredient and are used as sweetener in many drinks and foods. They include:
  • Maltodextrin
    Maltodextrin
    Maltodextrin is a polysaccharide that is used as a food additive. It is produced from starch by partial hydrolysis and is usually found as a creamy-white hygroscopic spraydried powder. Maltodextrin is easily digestible, being absorbed as rapidly as glucose, and might be either moderately sweet or...

    , a lightly hydrolyzed (DE 10–20) starch product used as a bland-tasting filler and thickener.
  • Various glucose syrup
    Glucose syrup
    Glucose syrup is a food syrup, made from the hydrolysis of starch. Maize is commonly used as the source of the starch in the USA, in which case the syrup is called "corn syrup", but glucose syrup is also made from other starch crops, including potatoes, wheat, barley, rice and cassavap.21...

    s (DE 30–70), also called corn syrup
    Corn syrup
    Corn syrup is a food syrup, which is made from the starch of maize and contains varying amounts of maltose and higher oligosaccharides, depending on the grade. Corn syrup is used in foods to soften texture, add volume, prevent crystallization of sugar, and enhance flavor...

    s in the US, viscous solutions used as sweeteners and thickeners in many kinds of processed foods.
  • Dextrose (DE 100), commercial glucose, prepared by the complete hydrolysis of starch.
  • High fructose syrup, made by treating dextrose solutions with the enzyme glucose isomerase
    Glucose isomerase
    -Other functions:There is evidence that phosphoglucose isomerase acts as a molecular messenger. It is produced and secreted by white blood cells, and acts to regulate the growth of several different cell types.-Pathology:...

    , until a substantial fraction of the glucose has been converted to fructose. In the United States, high fructose corn syrup
    High fructose corn syrup
    High-fructose corn syrup  — also called glucose-fructose syrup in the UK, glucose/fructose in Canada, and high-fructose maize syrup in other countries — comprises any of a group of corn syrups that has undergone enzymatic processing to convert some of its glucose into fructose to produce...

     is the principal sweetener used in sweetened beverages because fructose has better handling characteristics, such as microbiological stability, and more consistent sweetness/flavor. One kind of high fructose corn syrup, HFCS-55, is typically sweeter than regular sucrose
    Sucrose
    Sucrose is the organic compound commonly known as table sugar and sometimes called saccharose. A white, odorless, crystalline powder with a sweet taste, it is best known for its role in human nutrition. The molecule is a disaccharide composed of glucose and fructose with the molecular formula...

     because it is made with more fructose, while the sweetness of HFCS-42 is on par with sucrose.
  • Sugar alcohol
    Sugar alcohol
    A sugar alcohol is a hydrogenated form of carbohydrate, whose carbonyl group has been reduced to a primary or secondary hydroxyl group . Sugar alcohols have the general formula Hn+1H, whereas sugars have HnHCO...

    s, such as maltitol
    Maltitol
    Maltitol is a sugar alcohol used as a sugar substitute. It has 75-90% of the sweetness of sucrose and nearly identical properties, except for browning. It is used to replace table sugar because it has fewer calories, does not promote tooth decay, and has a somewhat lesser effect on blood glucose...

    , erythritol
    Erythritol
    Erythritol is a sugar alcohol that has been approved for use as a food additive in the United States and throughout much of the world. It was discovered in 1848 by British chemist John Stenhouse. It occurs naturally in some fruits and fermented foods...

    , sorbitol
    Sorbitol
    Sorbitol, also known as glucitol, Sorbogem® and Sorbo®, is a sugar alcohol that the human body metabolizes slowly. It can be obtained by reduction of glucose, changing the aldehyde group to a hydroxyl group. Sorbitol is found in apples, pears, peaches, and prunes...

    , mannitol
    Mannitol
    Mannitol is a white, crystalline organic compound with the formula . This polyol is used as an osmotic diuretic agent and a weak renal vasodilator...

     and hydrogenated starch hydrolysate, are sweeteners made by reducing sugars.

Modified starches


A modified food starch
Modified starch
Modified starch, also called starch derivatives, are prepared by physically, enzymatically, or chemically treating native starch, thereby changing the properties of the starch. Modified starches are used in practically all starch applications, such as in food products as a thickening agent,...

 is a starch that has been chemically modified to allow the starch to function properly under conditions frequently encountered during processing or storage, such as high heat, high shear, low pH, freeze/thaw and cooling.

The modified starches are E coded
E number
E numbers are number codes for food additives that have been assessed for use within the European Union . They are commonly found on food labels throughout the European Union. Safety assessment and approval are the responsibility of the European Food Safety Authority...

 according to the International Numbering System
Codex Alimentarius
The Codex Alimentarius is a collection of internationally recognized standards, codes of practice, guidelines and other recommendations relating to foods, food production and food safety. Its name derives from the Codex Alimentarius Austriacus...

 for Food Additives (INS):
  • 1400 Dextrin
    Dextrin
    Dextrins are a group of low-molecular-weight carbohydrates produced by the hydrolysis of starch or glycogen. Dextrins are mixtures of polymers of D-glucose units linked by α- or α- glycosidic bonds....

  • 1401 Acid-treated starch
  • 1402 Alkaline-treated starch
  • 1403 Bleached starch
  • 1404 Oxidized starch
  • 1405 Starches, enzyme-treated
  • 1410 Monostarch phosphate
    Phosphate
    A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...

  • 1412 Distarch phosphate
  • 1413 Phosphated distarch phosphate
  • 1414 Acetylated distarch phosphate
  • 1420 Starch acetate
  • 1422 Acetylated distarch adipate
    Acetylated distarch adipate
    Acetylated distarch adipate , is a starch that is treated with acetic anhydride and adipic acid anhydride to resist high temperatures. It is used in foods as a bulking agent, stabilizer and a thickener....

  • 1440 Hydroxypropyl starch
  • 1442 Hydroxypropyl distarch phosphate
    Hydroxypropyl distarch phosphate
    Hydroxypropyl distarch phosphate is a modified resistant starch. It is currently used as a food additive . It is approved for use in the European Union , the United States, Australia, and New Zealand.- External links :...

  • 1443 Hydroxypropyl distarch glycerol
  • 1450 Starch sodium octenyl succinate
  • 1451 Acetylated oxidized starch


INS 1401, 1402, 1403 and 1405 are in the EU food ingredients without an E-number. Typical modified starches for technical applications are cationic starches, hydroxyethyl starch and carboxymethylated starches.

Use as food additive


As an additive for food processing
Food processing
Food processing is the set of methods and techniques used to transform raw ingredients into food or to transform food into other forms for consumption by humans or animals either in the home or by the food processing industry...

, food starches are typically used as thickeners and stabilizers in foods such as puddings, custards, soups, sauces, gravies, pie fillings, and salad dressings, and to make noodles and pastas.

Gummed sweets such as jelly beans and wine gums are not manufactured using a mold in the conventional sense. A tray is filled with native starch and leveled. A positive mold is then pressed into the starch leaving an impression of 1000 or so jelly beans. The jelly mix is then poured into the impressions and put into a stove to set. This method greatly reduces the number of molds that must be manufactured.

In the pharmaceutical industry, starch is also used as an excipient
Excipient
An excipient is generally a pharmacologically inactive substance used as a carrier for the active ingredients of a medication. In many cases, an "active" substance may not be easily administered and absorbed by the human body; in such cases the substance in question may be dissolved into or...

, as tablet
Tablet
A tablet is a pharmaceutical dosage form. It comprises a mixture of active substances and excipients, usually in powder form, pressed or compacted from a powder into a solid dose...

 disintegrant or as binder.

Papermaking


Papermaking
Papermaking
Papermaking is the process of making paper, a substance which is used universally today for writing and packaging.In papermaking a dilute suspension of fibres in water is drained through a screen, so that a mat of randomly interwoven fibres is laid down. Water is removed from this mat of fibres by...

 is the largest non-food application for starches globally, consuming millions of metric tons annually. In a typical sheet of copy paper for instance, the starch content may be as high as 8%. Both chemically modified and unmodified starches are used in papermaking. In the wet part of the papermaking process, generally called the “wet-end”, the starches used are cationic and have a positive charge bound to the starch polymer. These starch derivatives associate with the anionic or negatively charged paper fibers / cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

 and inorganic fillers. Cationic starches together with other retention and internal sizing
Sizing
Sizing or size is any one of numerous specific substances that is applied to or incorporated in other material, especially papers and textiles, to act as a protecting filler or glaze....

 agent help to give the necessary strength properties to the paper web to be formed in the papermaking process (wet strength
Wet strength
Wet strength of paper is a measure of how well the fibreweb is holding together upon a force of rupture. Wet strength is routinely expressed as the ratio of wet to dry tensile force at break.-Mechanism:...

), and to provide strength to the final paper sheet (dry strength).

In the dry end of the papermaking process, the paper web is rewetted with a starch based solution. The process is called surface sizing
Sizing
Sizing or size is any one of numerous specific substances that is applied to or incorporated in other material, especially papers and textiles, to act as a protecting filler or glaze....

. Starches used have been chemically, or enzymatically depolymerized at the paper mill or by the starch industry (oxidized starch). The size - starch solutions are applied to the paper web by means of various mechanical presses (size press). Together with surface sizing agent the surface starches impart additional strength to the paper web and additionally provide water hold out or "size" for superior printing properties. Starch is also used in paper coating as one of the binders for the coating formulation a mixture of pigments, binders and thickeners. Coated paper
Coated paper
Coated paper is paper which has been coated by a compound to impart certain qualities to the paper, including weight, surface gloss, smoothness or reduced ink absorbency. Kaolinite or calcium carbonate are used to coat paper for high quality printing used in packaging industry and in magazines...

 has improved smoothness, hardness, whiteness and gloss and thus improves printing characteristics.

Corrugated board adhesives


Corrugated board adhesives are the next largest application of non-food starches globally. Starch glue
Glue
This is a list of various types of glue. Historically, the term "glue" only referred to protein colloids prepared from animal flesh. The meaning has been extended to refer to any fluid adhesive....

s are mostly based on unmodified native starches, plus some additive such as borax
Borax
Borax, also known as sodium borate, sodium tetraborate, or disodium tetraborate, is an important boron compound, a mineral, and a salt of boric acid. It is usually a white powder consisting of soft colorless crystals that dissolve easily in water.Borax has a wide variety of uses...

 and caustic soda. Part of the starch is gelatinized to carry the slurry of uncooked starches and prevent sedimentation. This opaque glue is called a SteinHall adhesive. The glue is applied on tips of the fluting. The fluted paper is pressed to paper called liner. This is then dried under high heat, which causes the rest of the uncooked starch in glue to swell/gelatinize. This gelatinizing makes the glue a fast and strong adhesive for corrugated board production.

Clothing starch


Clothing or laundry starch is a liquid that is prepared by mixing a vegetable starch in water (earlier preparations also had to be boiled), and is used in the laundering
Laundry
Laundry is a noun that refers to the act of washing clothing and linens, the place where that washing is done, and/or that which needs to be, is being, or has been laundered...

 of clothes
Clothing
Clothing refers to any covering for the human body that is worn. The wearing of clothing is exclusively a human characteristic and is a feature of nearly all human societies...

. Starch was widely used in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 in the 16th and 17th centuries to stiffen the wide collars and ruffs
Ruff (clothing)
A ruff is an item of clothing worn in Western Europe from the mid-sixteenth century to the mid-seventeenth century.The ruff, which was worn by men, women and children, evolved from the small fabric ruffle at the drawstring neck of the shirt or chemise...

 of fine linen which surrounded the necks of the well-to-do. During the 19th century and early 20th century, it was stylish to stiffen the collars and sleeves of men's shirt
Shirt
A shirt is a cloth garment for the upper body. Originally an undergarment worn exclusively by men, it has become, in American English, a catch-all term for almost any garment other than outerwear such as sweaters, coats, jackets, or undergarments such as bras, vests or base layers...

s and the ruffles of girls' petticoat
Petticoat
A petticoat or underskirt is an article of clothing for women; specifically an undergarment to be worn under a skirt or a dress. The petticoat is a separate garment hanging from the waist ....

s by applying starch to them as the clean clothes were being ironed
Ironing
Ironing is the use of a heated tool to remove wrinkles from fabric. The heating is commonly done to a temperature of 180-220 °Celsius, depending on the fabric. Ironing works by loosening the bonds between the long-chain polymer molecules in the fibers of the material...

. Aside from the smooth, crisp edges it gave to clothing, it served practical purposes as well. Dirt
Dust
Dust consists of particles in the atmosphere that arise from various sources such as soil dust lifted up by wind , volcanic eruptions, and pollution...

 and sweat
SWEAT
SWEAT is an OLN/TSN show hosted by Julie Zwillich that aired in 2003-2004.Each of the 13 half-hour episodes of SWEAT features a different outdoor sport: kayaking, mountain biking, ice hockey, beach volleyball, soccer, windsurfing, rowing, Ultimate, triathlon, wakeboarding, snowboarding, telemark...

 from a person's neck and wrists would stick to the starch rather than to the fibers of the clothing, and would easily wash away along with the starch. After each laundering, the starch would be reapplied. Today, the product is sold in aerosol cans
Aerosol spray
Aerosol spray is a type of dispensing system which creates an aerosol mist of liquid particles. This is used with a can or bottle that contains a liquid under pressure. When the container's valve is opened, the liquid is forced out of a small hole and emerges as an aerosol or mist...

 for home use.

Other


Another large non-food starch application is in the construction industry, where starch is used in the gypsum wall board manufacturing process. Chemically modified or unmodified starches are added to the stucco containing primarily gypsum
Gypsum
Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is found in alabaster, a decorative stone used in Ancient Egypt. It is the second softest mineral on the Mohs Hardness Scale...

. Top and bottom heavyweight sheets of paper are applied to the formulation, and the process is allowed to heat and cure to form the eventual rigid wall board. The starches act as a glue for the cured gypsum rock with the paper covering, and also provide rigidity to the board.

Starch is used in the manufacture of various adhesives or glues for book-binding, wallpaper adhesives, paper sack production, tube winding, gummed paper, envelope adhesives, school glues and bottle labeling. Starch derivatives, such as yellow dextrins, can be modified by addition of some chemicals to form a hard glue for paper work; some of those forms use borax or soda ash, which are mixed with the starch solution at 50-70 °C to create a very good adhesive. Sodium silicate can be added to reinforce these formulae.
  • Starch is also used to make some packing peanuts, and some drop ceiling
    Dropped ceiling
    A dropped ceiling is a secondary ceiling, hung below the main ceiling. They may also be referred to as a drop ceiling, false ceiling, or suspended ceiling, and are a staple of modern construction and architecture. The area above the dropped ceiling is called the plenum space, as it is sometimes...

     tiles.
  • Textile chemicals from starch are used to reduce breaking of yarn
    Yarn
    Yarn is a long continuous length of interlocked fibres, suitable for use in the production of textiles, sewing, crocheting, knitting, weaving, embroidery and ropemaking. Thread is a type of yarn intended for sewing by hand or machine. Modern manufactured sewing threads may be finished with wax or...

    s during weaving; the warp yarns are sized. Starch is mainly used to size cotton
    Cotton
    Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....

     based yarns. Modified starch is also used as textile printing
    Textile printing
    Textile printing is the process of applying colour to fabric in definite patterns or designs. In properly printed fabrics the colour is bonded with the fiber, so as to resist washing and friction...

     thickener.
  • In the printing
    Printing
    Printing is a process for reproducing text and image, typically with ink on paper using a printing press. It is often carried out as a large-scale industrial process, and is an essential part of publishing and transaction printing....

     industry, food grade starch is used in the manufacture of anti-set-off spray powder
    Anti-set-off spray powder
    In printing, anti-set-off spray powder is used to make an air gap between printed sheets of paper. This enables the ink to dry naturally and therefore avoid the unwanted transfer of ink from one printed sheet to another. The problem can occur with most types of printing.Anti-set-off spray powder is...

     used to separate printed sheets of paper to avoid wet ink being set off
    Set-off (printing)
    In printing, set-off is the American term given to the unwanted transfer of ink from one printed sheet to another. The problem can occur with most types of printing, and is avoided by the use of anti-set-off spray powder....

    .
  • Starch is used to produce various bioplastic
    Bioplastic
    Bioplastics are a form of plastics derived from renewable biomass sources, such as vegetable fats and oils, corn starch, pea starch, or microbiota, rather than fossil-fuel plastics which are derived from petroleum...

    s, synthetic polymers that are biodegradable. An example is polylactic acid
    Polylactic acid
    Poly or polylactide is a thermoplastic aliphatic polyester derived from renewable resources, such as corn starch , tapioca products or sugarcanes...

    .
  • For body powder, powdered corn starch is used as a substitute for talcum powder, and similarly in other health and beauty products.
  • In oil exploration, starch is used to adjust the viscosity of drilling fluid
    Drilling fluid
    In geotechnical engineering, drilling fluid is a fluid used to aid the drilling of boreholes into the earth. Often used while drilling oil and natural gas wells and on exploration drilling rigs, drilling fluids are also used for much simpler boreholes, such as water wells. Liquid drilling fluid...

    , which is used to lubricate the drill head and suspend the grinding residue in petroleum extraction.
  • Glucose from starch can be further fermented to biofuel
    Biofuel
    Biofuel is a type of fuel whose energy is derived from biological carbon fixation. Biofuels include fuels derived from biomass conversion, as well as solid biomass, liquid fuels and various biogases...

     corn ethanol
    Corn ethanol
    Corn ethanol is ethanol produced from corn as a biomass through industrial fermentation, chemical processing and distillation. Corn is the main feedstock used for producing ethanol fuel in the United States and it is mainly used as an oxygenate to gasoline in the form of low-level blends, and to a...

     using the so called wet milling process. Today most bioethanol production plants use the dry milling process to ferment corn or other feedstock directly to ethanol.
  • Hydrogen production
    Hydrogen production
    Hydrogen production is the family of industrial methods for generating hydrogen. Currently the dominant technology for direct production is steam reforming from hydrocarbons. Many other methods are known including electrolysis and thermolysis...

     can use starch as the raw material, using enzymes.

See also

  • Acrylamide
    Acrylamide
    Acrylamide is a chemical compound with the chemical formula C3H5NO. Its IUPAC name is prop-2-enamide. It is a white odourless crystalline solid, soluble in water, ethanol, ether, and chloroform. Acrylamide is incompatible with acids, bases, oxidizing agents, iron, and iron salts...

    , present in fried potatoes
  • Baking
    Baking
    Baking is the technique of prolonged cooking of food by dry heat acting by convection, and not by radiation, normally in an oven, but also in hot ashes, or on hot stones. It is primarily used for the preparation of bread, cakes, pastries and pies, tarts, quiches, cookies and crackers. Such items...

    , making starches digestible
  • Cooking
    Cooking
    Cooking is the process of preparing food by use of heat. Cooking techniques and ingredients vary widely across the world, reflecting unique environmental, economic, and cultural traditions. Cooks themselves also vary widely in skill and training...

  • Distilled beverage
    Distilled beverage
    A distilled beverage, liquor, or spirit is an alcoholic beverage containing ethanol that is produced by distilling ethanol produced by means of fermenting grain, fruit, or vegetables...

    , brewing from starch alcohol
  • Flour
    Flour
    Flour is a powder which is made by grinding cereal grains, other seeds or roots . It is the main ingredient of bread, which is a staple food for many cultures, making the availability of adequate supplies of flour a major economic and political issue at various times throughout history...

  • Modified starch
    Modified starch
    Modified starch, also called starch derivatives, are prepared by physically, enzymatically, or chemically treating native starch, thereby changing the properties of the starch. Modified starches are used in practically all starch applications, such as in food products as a thickening agent,...

  • Non-Newtonian fluid
    Non-Newtonian fluid
    A non-Newtonian fluid is a fluid whose flow properties differ in any way from those of Newtonian fluids. Most commonly the viscosity of non-Newtonian fluids is not independent of shear rate or shear rate history...

  • Starch indicator
    Starch indicator
    Starch is often used in chemistry as an indicator for redox titrations where triiodide is present. Starch forms a very dark blue-black complex with triiodide which can be made by mixing iodine with iodide . However, the complex is not formed if only iodine or only iodide is present...

  • Yeast extract
    Yeast extract
    Yeast extract is the common name for various forms of processed yeast products made by extracting the cell contents ; they are used as food additives or flavourings, or as nutrients for bacterial culture media. They are often used to create savory flavors and umami taste sensations. Monosodium...


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