HOME

TheInfoList




Starch or amylum is a
polymeric A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical ...
carbohydrate is a disaccharide A disaccharide (also called a double sugar or ''biose'') is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosaccharides, disaccharides are simple sugars soluble in water. Three common ex ...
consisting of numerous
glucose Glucose is a simple with the . Glucose is the most abundant , a subcategory of s. Glucose is mainly made by and most during from water and carbon dioxide, using energy from sunlight, where it is used to make in s, the most abundant carbohydr ...

glucose
units joined by
glycosidic bond A glycosidic bond or glycosidic linkage is a type of covalent bond A covalent bond is a chemical bond A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. The bond may ...
s. This
polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant found in . They are long chain carbohydrates composed of units bound together by . This carbohydrate can react with water () using as catalyst, which produces constituent sugars ...
is produced by most green
plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel ...

plant
s for energy storage. Worldwide, it is the most common carbohydrate in human diets, and is contained in large amounts in
staple food A staple food, food staple, or simply a staple, is a food Food is any substance consumed to provide Nutrient, nutritional support for an organism. Food is usually of plant, animal or Fungus, fungal origin, and contains essential nutrients, ...

staple food
s like
wheat Wheat is a grass widely cultivated for its seed, a cereal grain which is a worldwide staple food. The many species of wheat together make up the genus ''Triticum''; the most widely grown is common wheat Common wheat (''Triticum aestivum'' ...

wheat
,
potato The potato is a starch#Food, starchy tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial plant, perennial in the nightshade family Solanaceae. Wild potato species can be found thro ...

potato
es,
maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It can also be ...

maize
(corn),
rice Rice is the seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was relea ...

rice
, and
cassava ''Manihot esculenta'', commonly called cassava (), manioc, or yuca (among numerous regional names) is a woody shrub A shrub (or bush, but this is more of a gardening term) is a small- to medium-sized perennial woody plant. Unlike herb ...

cassava
(manioc). 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 Helical may refer to: *Helix, the mathematical concept for the shape * Helical spring, a coilspring *Helical plc, a British property company, once a maker of steel bar stock * Helicoil, a mechanical thread repairing insert * H-el-ical//, stage name ...

helical
amylose Amylose is a polysaccharide , a beta-glucan polysaccharide Image:amylose 3Dprojection.svg">350px, Amylose is a linear polymer of glucose mainly linked with α(1→4) bonds. It can be made of several thousands of glucose units. It is one of the two ...

amylose
and the branched
amylopectin Amylopectin is a water-soluble Subscription required for online access. polysaccharide and highly branched polymer of α-glucose units found in plants. It is one of the two components of starch, the other being amylose. Glucose units are linke ...
. Depending on the plant, starch generally contains 20 to 25% amylose and 75 to 80% amylopectin by weight.
Glycogen Glycogen is a multibranched of that serves as a form of energy storage in s, , and bacteria. The polysaccharide structure represents the main storage form of glucose in the body. Glycogen functions as one of two forms of energy reserves, g ...

Glycogen
, the glucose store of animals, is a more highly branched version of amylopectin. In industry, starch is converted into sugars, for example by
malt Malt is germinated cereal grain that has been dried in a process known as "malting Malting is a process of steeping Steeping is the soaking of an organic solid, such as leaves, in a liquid (usually water) to extract flavours or to soft ...
ing, and
fermented Fermentation is a metabolic Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a characteristic that distinguishes physical entities that have biological processes, such as signaling ...

fermented
to produce
ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ (anatomy), ...

ethanol
in the manufacture of
beer Beer is one of the oldest and most widely consumed alcoholic drinks in the world, and the third most popular drink overall after water and tea. Beer is brewing, brewed from cereal, cereal grains—most commonly from malted barley, though wh ...

beer
,
whisky Whisky or whiskey is a type of made from . Various grains (which may be ) are used for different varieties, including , , , and . Whisky is typically in wooden s, which are often old casks or may also be made of charred . Whisky is a str ...

whisky
and
biofuel Biofuel is fuel that is produced through contemporary processes from biomass, rather than by the very slow geological processes involved in the formation of fossil fuels, such as oil. Since biomass technically can be used as a fuel directly (e. ...

biofuel
. It is processed to produce many of the sugars used in processed foods. Mixing most starches in warm water produces a paste, such as
wheatpaste Wheat paste (also known as flour and water paste, flour paste, or simply paste) is a gel or liquid adhesive made from wheat flour or starch and water. It has been used since antiquity for various arts and crafts such as book binding, découpage, co ...

wheatpaste
, which can be used as a thickening, stiffening or gluing agent. The greatest industrial non-food use of starch is as an adhesive in the
papermaking Papermaking is the manufacture of paper and cardboard, which are used widely for printing, writing, and packaging, among many other purposes. Today almost all paper is Pulp and paper industry, made using industrial machinery, while handmade pape ...
process.
Starch solution
Starch solution
may be applied to certain textile goods before ironing, to stiffen them.


Etymology

The word "starch" is from its
Germanic Germanic may refer to: * Germanic peoples, an ethno-linguistic group identified by their use of the Germanic languages ** List of ancient Germanic peoples and tribes * Germanic languages :* Proto-Germanic language, a reconstructed proto-language of ...

Germanic
root with the meanings "strong, stiff, strengthen, stiffen". Modern German ''Stärke'' (strength) is related and referring for centuries main application, the use in textile:
sizing Sizing or size is a substance that is applied to, or incorporated into, other materials—especially papers and textiles—to act as a protective filler or glaze. Sizing is used in papermaking Papermaking is the manufacture of paper and card ...
yarn Yarn is a long continuous length of interlocked fibres, suitable for use in the production of textiles, sewing, crocheting, knitting, weaving, embroidery, or ropemaking. Thread (yarn), Thread is a type of yarn intended for sewing by hand or sewin ...
for
weaving Weaving is a method of textile A textile is a flexible material made by creating an interlocking bundle of yarn Yarn is a long continuous length of interlocked fibres, suitable for use in the production of textiles, sewing, crocheti ...

weaving
and starching
linen Linen () is a textile made from the fibers of the flax plant. Linen is very strong, absorbent, and dries faster than cotton. Because of these properties, linen is comfortable to wear in hot weather and is valued for use in garments. It also h ...

linen
. The
Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as of ...
term for starch, "amylon" (ἄμυλον), which means "not milled", is also related. It provides the root
amyl Amyl may refer to: * Amylum or starch, a carbohydrate ** Amylopectin, a polymer of glucose found in plants; one of two components of starch ** Amylose, a helical polymer made of α-D-glucose units; one of two components of starch * Pentyl, a five ...
, which is used as a prefix for several
5-carbon
5-carbon
compounds related to or derived from starch (e.g.
amyl alcohol An amyl alcohol is any of 8 alcohols with the formula C5H12O. A mixture of pentyl, amyl alcohols (also called amyl alcohol) can be obtained from fusel alcohol. Amyl alcohol is used as a solvent and in esterification, by which is produced amyl acetat ...
).


History

Starch grains from the
rhizome In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the A ...

rhizome
s of ''
Typha ''Typha'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. ...

Typha
'' (cattails, bullrushes) as
flour Flour is a powder A powder is a dry, bulk solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and contain the least amount ...

flour
have been identified from
grinding stone Millstones or mill stones are stones used in gristmill A gristmill (also: grist mill, corn mill, flour mill, feed mill or feedmill) grinds cereal grain into flour and middlings. The term can refer to either the grinding mechanism or the b ...

grinding stone
s in Europe dating back to 30,000 years ago. Starch grains from
sorghum ''Sorghum'' is a genus of about 25 species of flowering plants in the grass family ( Poaceae). Some of these species are grown as cereals for human consumption and some in pastures for animals. One species, '' Sorghum bicolor'', was originally ...

sorghum
were found on grind stones in caves in
Ngalue Ngalue Cave is an archaeological site located in the Niassa province of Mozambique Mozambique (), officially the Republic of Mozambique ( pt, Moçambique or , ; ny, Mozambiki; sw, Msumbiji; ts, Muzambhiki), is a country located in South ...
,
Mozambique Mozambique (), officially the Republic of Mozambique ( pt, Moçambique or , ; ny, Mozambiki; sw, Msumbiji; ts, Muzambhiki), is a country located in Southeastern Africa bordered by the Indian Ocean The Indian Ocean is the third-lar ...

Mozambique
dating up to 100,000 years ago. Pure extracted wheat starch paste was used in
Ancient Egypt Ancient Egypt was a civilization  A civilization (or civilisation) is a that is characterized by , , a form of government, and systems of communication (such as ). Civilizations are intimately associated with additional char ...

Ancient Egypt
possibly to glue
papyrus Papyrus ( ) is a material similar to thick paper that was used in ancient times as a writing surface. It was made from the pith of the papyrus plant, ''Cyperus papyrus'', a wetland sedge. ''Papyrus'' (plural: ''papyri'') can also refer to a do ...

papyrus
. The extraction of starch is first described in the ''
Natural History Natural history is a domain of inquiry involving organisms, including animals, fungus, fungi, and plants, in their natural environment, leaning more towards observational than experimental methods of study. A person who studies natural history ...
'' of
Pliny the Elder #REDIRECT Pliny the Elder#REDIRECT Pliny the Elder Gaius Plinius Secundus (AD 23/2479), called Pliny the Elder (), was a Roman author, a naturalist Natural history is a domain of inquiry involving organisms, including animals, fungus, fungi, ...

Pliny the Elder
around AD 77–79. Romans used it also in
cosmetic Cosmetic may refer to: *Cosmetics, or make-up, substances to enhance the beauty of the human body, apart from simple cleaning *Cosmetic, an adjective describing beauty, aesthetics, or appearance, especially concerning the human body *Cosmetic, a top ...
creams, to powder the hair and to thicken sauces. Persians and Indians used it to make dishes similar to gothumai wheat
halva Halva (also halvah, halwa, حلاوة and other spellings) refers to various local confection Confectionery is the art Art is a diverse range of (products of) human activities involving creative imagination to express technical p ...

halva
. Rice starch as surface treatment of paper has been used in paper production in China since 700 CE.


Starch industry

In addition to starchy plants consumed directly, by 2008 66 million tonnes of starch were being produced per year worldwide. In 2011, production was increased to 73 million ton. In the
EU
EU
the starch industry produced about 8.5 million tonnes in 2008, with around 40% being used for industrial applications and 60% for food uses, most of the latter as
glucose syrup Glucose is a simple sugar Sugar is the generic name for sweet-tasting, soluble carbohydrate is a disaccharide found in animal milk. It consists of a molecule of D-galactose and a molecule of D-glucose bonded by beta-1-4 glycosidic li ...
s. In 2017 EU production was 11 million ton of which 9,4 million ton was consumed in the EU and of which 54% were starch sweeteners. The produced about 27.5 million tons of starch in 2017, of which about 8.2 million tons was
high fructose syrup High-fructose corn syrup (HFCS), also known as glucose-fructose, isoglucose and glucose-fructose syrup, is a sweetener made from corn starch. As in the production of conventional corn syrup, the starch is broken down into glucose by enzymes. T ...
, 6.2 million tons was glucose syrups, and 2.5 million tons were starch products. The rest of the starch was used for producing
ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ (anatomy), ...

ethanol
(1.6 billion gallons).


Energy store of plants

Most green plants store energy as starch, which is packed into semicrystalline granules. The extra glucose is changed into starch which is more complex than the glucose produced by plants. Young plants live on this stored energy in their roots, seeds, and fruits until it can find suitable soil in which to grow. An exception is the family
Asteraceae The family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain the well-being of its members and of society. Ideally, fam ...

Asteraceae
(asters, daisies and sunflowers), where starch is replaced by the
fructan A fructan is a polymer A polymer (; Greek ''poly- Poly, from the Greek :wikt:πολύς, πολύς meaning "many" or "much", may refer to: Businesses * China Poly Group Corporation, a Chinese business group, and its subsidiaries: ** Poly P ...
inulin Inulins are a group of naturally occurring polysaccharides produced by many types of plants, industrially most often extracted from chicory. The inulins belong to a class of dietary fibers known as fructans. Inulin is used by some plants as a mean ...

inulin
. Inulin-like fructans are also present in grasses such as
wheat Wheat is a grass widely cultivated for its seed, a cereal grain which is a worldwide staple food. The many species of wheat together make up the genus ''Triticum''; the most widely grown is common wheat Common wheat (''Triticum aestivum'' ...

wheat
, in
onion The onion (''Allium cepa'' L., from Latin ''cepa'' "onion"), also known as the bulb onion or common onion, is a vegetable Vegetables are parts of plants that are consumed by humans or other animals as food. The original meaning is still com ...

onion
s and
garlic Garlic (''Allium sativum'') is a species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest ...

garlic
,
bananas A banana is an elongated, edible fruit In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who special ...

bananas
, and
asparagus Asparagus, or garden asparagus, folk name sparrow grass, scientific name ''Asparagus officinalis'', is a perennial A perennial plant or simply perennial is a plant Plants are predominantly photosynthetic eukaryotes of the Kingdom ...

asparagus
. In
photosynthesis Photosynthesis is a process used by plants and other organisms to into that, through , can later be released to fuel the organism's activities. Some of this chemical energy is stored in molecules, such as s and es, which are synthesized fro ...

photosynthesis
, plants use light energy to produce
glucose Glucose is a simple with the . Glucose is the most abundant , a subcategory of s. Glucose is mainly made by and most during from water and carbon dioxide, using energy from sunlight, where it is used to make in s, the most abundant carbohydr ...

glucose
from
carbon dioxide Carbon dioxide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as pare ...

carbon dioxide
. The glucose is used to generate the chemical energy required for general
metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a characteristic that distinguishes physical entities that have biological processes, such as Cell signaling, signaling and self-sustaining ...

metabolism
, to make organic compounds such as
nucleic acids Nucleic acids are biopolymer Biopolymers are natural polymers produced by the cells of Organism, living organisms. Biopolymers consist of monomeric units that are Covalent_bond, covalently bonded to form larger molecules. There are three main cla ...
,
lipids In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...

lipids
,
proteins Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

proteins
and structural polysaccharides such as
cellulose Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important stru ...

cellulose
, or is stored in the form of starch granules, in
amyloplastImage:Potato - Amyloplasts.jpg, Amyloplasts in a potato cellAmyloplasts are a type of plastid, double-enveloped organelles in plant cells that are involved in various biological pathways. Amyloplasts are specifically a type of leucoplast, a subcatego ...
s. Toward the end of the growing season, starch accumulates in twigs of trees near the buds.
Fruit In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the ...

Fruit
,
seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was released to generally positi ...

seed
s,
rhizome In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the A ...

rhizome
s, and
tuber Tubers are enlarged structures used as storage organs for nutrients in some plants. They are used for the plant's perennation (survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growing season, and ...
s store starch to prepare for the next growing season. Glucose is soluble in water,
hydrophilic A hydrophile is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral group of two or more atoms ...
, binds with water and then takes up much space and is active; glucose in the form of starch, on the other hand, is not soluble, therefore osmotically inactive and can be stored much more compactly. The semicrystalline granules generally consist of concentric layers of amylose and amylopectin which can be made bioavailable upon cellular demand in the plant. Glucose molecules are bound in starch by the easily
hydrolyzed Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile In chemistry, a nucleop ...

hydrolyzed
alpha bonds. The same type of bond is found in the animal reserve polysaccharide
glycogen Glycogen is a multibranched of that serves as a form of energy storage in s, , and bacteria. The polysaccharide structure represents the main storage form of glucose in the body. Glycogen functions as one of two forms of energy reserves, g ...

glycogen
. This is in contrast to many structural polysaccharides such as
chitin units that repeat to form long chains in β-(1→4)-linkage. of the chitin molecule. Chitin ( carbon, C8H13O5N)n ( ) is a long-chain polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part") is a Chemical su ...

chitin
, cellulose and
peptidoglycan Peptidoglycan or murein is a polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part") is a Chemical substance, substance or material consisting of very large molecules, or macromolecules, composed of many Repea ...

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


Biosynthesis

Plants produce starch by first converting
glucose 1-phosphate Glucose 1-phosphate (also called cori ester) is a glucose molecule with a phosphate group on the 1'-carbon. It can exist in either the α- or β-anomeric form. Reactions of α-glucose 1-phosphate Catabolic In glycogenolysis, it is the direct prod ...

glucose 1-phosphate
to -glucose using the enzyme glucose-1-phosphate adenylyltransferase. This step requires energy in the form of
ATP ATP may refer to: Companies and organizations * Association of Tennis Professionals * American Technical Publishers * ', a Danish pension * Armenia Tree Project * Association for Transpersonal Psychology * ATP architects engineers office * ATP ...

ATP
. The enzyme starch synthase then adds the ADP-glucose via a 1,4-alpha
glycosidic bond A glycosidic bond or glycosidic linkage is a type of covalent bond A covalent bond is a chemical bond A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. The bond may ...
to a growing chain of glucose residues, liberating and creating amylose. The ADP-glucose is almost certainly added to the non-reducing end of the amylose polymer, as the UDP-glucose is added to the non-reducing end of glycogen during glycogen synthesis.
Starch branching enzyme 1,4-alpha-glucan-branching enzyme, also known as brancher enzyme or glycogen-branching enzyme is an enzyme that in humans is encoded by the ''GBE1'' gene. Glycogen branching enzyme is an enzyme that adds branches to the growing glycogen molecule ...
introduces 1,6-alpha glycosidic bonds between the amylose chains, creating the branched amylopectin. The starch debranching enzyme isoamylase removes some of these branches. Several
isoform A protein isoform, or "protein variant", is a member of a set of highly similar proteins Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallo ...
s of these enzymes exist, leading to a highly complex synthesis process. Glycogen and amylopectin have similar 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. Amylopectin is synthesized from ADP-glucose while mammals and fungi synthesize glycogen from
UDP-glucose Uridine diphosphate glucose (uracil-diphosphate glucose, Uridine diphosphate, UDP-glucose) is a nucleotide sugar. It is involved in glycosyltransferase reactions in metabolism. Functions UDP-glucose is used in nucleotide sugars metabolism, nucleot ...

UDP-glucose
; for most cases, bacteria synthesize glycogen fro
ADP-glucose
(analogous to starch). In addition to starch synthesis in plants, starch can be synthesized from non-food starch mediated by an enzyme cocktail. In this cell-free biosystem, beta-1,4-glycosidic bond-linked cellulose is partially hydrolyzed to
cellobiose Cellobiose is a disaccharide with the formula (C6H7(OH)4O)2O. It is classified as a reducing sugar. In terms of its chemical structure, it is derived from the condensation of a pair β-glucose molecules forging a β(1→4) bond. It can be hydro ...

cellobiose
. Cellobiose phosphorylase cleaves to glucose 1-phosphate and glucose; the other enzyme—potato alpha-glucan phosphorylase can add a glucose unit from glucose 1-phosphorylase to the non-reducing ends of starch. In it, phosphate is internally recycled. The other product, glucose, can be assimilated by a yeast. This cell-free bioprocessing does not need any costly chemical and energy input, can be conducted in aqueous solution, and does not have sugar losses.


Degradation

Starch is synthesized in plant leaves during the day and stored as granules; it serves as an energy source at night. The insoluble, highly branched starch chains have to be
phosphorylated In chemistry, phosphorylation of a molecule is the attachment of a phosphoryl group. This process and its inverse, dephosphorylation, are critical for many cellular processes in biology. Protein phosphorylation is especially important for their fu ...
in order to be accessible for degrading enzymes. The enzyme glucan, water dikinase (GWD) phosphorylates at the C-6 position of a glucose molecule, close to the chains 1,6-alpha branching bonds. A second enzyme, phosphoglucan, water dikinase (PWD) phosphorylates the glucose molecule at the C-3 position. A loss of these enzymes, for example a loss of the GWD, leads to a starch excess (sex) phenotype, and because starch cannot be phosphorylated, it accumulates in the plastids. After the phosphorylation, the first degrading enzyme, beta-amylase (BAM) can attack the glucose chain at its non-reducing end.
Maltose} Maltose ( or ), also known as maltobiose or malt sugar, is a disaccharide A disaccharide (also called a double sugar or ''biose'') is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosaccharides, disacchari ...

Maltose
is released as the main product of starch degradation. If the glucose chain consists of three or fewer molecules, BAM cannot release maltose. A second enzyme,
disproportionating enzyme-1 In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they underg ...
(DPE1), combines two maltotriose molecules. From this chain, a glucose molecule is released. Now, BAM can release another maltose molecule from the remaining chain. This cycle repeats until starch is degraded completely. If BAM comes close to the phosphorylated branching point of the glucose chain, it can no longer release maltose. In order for the phosphorylated chain to be degraded, the enzyme isoamylase (ISA) is required. The products of starch degradation are predominantly maltose and smaller amounts of glucose. These molecules are exported from the plastid to the cytosol, maltose via the maltose transporter, which if mutated (MEX1-mutant) results in maltose accumulation in the plastid. Glucose is exported via the plastidic glucose translocator (pGlcT). These two sugars act as a precursor for sucrose synthesis.
Sucrose Sucrose is a type of sugar Sugar is the generic name for , soluble s, many of which are used in food. Simple sugars, also called s, include , , and . Compound sugars, also called s or double sugars, are molecules made of two monosacchari ...

Sucrose
can then be used in the oxidative pentose phosphate pathway in the mitochondria, to generate ATP at night.


Properties


Structure

While amylose was thought to be completely unbranched, it is now known that some of its molecules contain a few branch points. Amylose is a much smaller molecule than amylopectin. About one quarter of the mass of starch granules in plants consist of amylose, although there are about 150 times more amylose than amylopectin molecules. 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 2 μm) while
potato starch The potato is a starch Starch or amylum is a consisting of numerous units joined by s. This is produced by most green s for energy storage. Worldwide, it is the most common carbohydrate in human diets, and is contained in large amount ...

potato starch
es have larger granules (up to 100 μm). Some cultivated plant varieties have pure amylopectin starch without amylose, known as ''waxy starches''. The most used is waxy maize, others are
glutinous rice Glutinous rice (''Oryza sativa var. glutinosa''; also called sticky rice, sweet rice or waxy rice) is a type of rice grown mainly in Southeast Asia, Southeast and East Asia, Northeastern India and Bhutan which has opaque grains, very low amylos ...

glutinous rice
and
waxy potato starch Waxy potato starch is a variety of commercially available starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose Glucose is a simple sugar with the Chemical formula#Molecular formula, molecular formula . Glucose is ...
. Waxy starches have less retrogradation, resulting in a more stable paste. High amylose starch, amylomaize, is cultivated for the use of its gel strength and for use as a
resistant starch Resistant starch (RS) is starch, including its degradation products, that escapes from digestion in the small intestine of healthy individuals. Resistant starch occurs naturally in foods but is also added to foods by the addition of dried raw foo ...
(a starch that resists digestion) in food products. Synthetic amylose made from cellulose has a well-controlled degree of polymerization. Therefore, it can be used as a potential drug deliver carrier.


Dissolution and gelatinization

When being heated in abundant water, the granules of native starch 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 The viscosity of a fluid In physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department of knowledge which relates to the order of nature, or, ...

viscosity
. This process is called
starch gelatinization Starch gelatinization is a process of breaking down the Intermolecular bond, intermolecular bonds of starch molecules in the presence of water and heat, allowing the hydrogen bonding sites (the Hydroxy group, hydroxyl hydrogen and oxygen) to engag ...
. The gelatinization temperature of starch varies depending on starch cultivar, amylose/amylopectin content, and water content. Starch with water could experience complex multiphase transitions during temperature scanning. For starch with excess water, a single gelatinisation endotherm can be usually observed in the low temperature range (54–73 °C). By reducing the water content (<64%) in starch, more endothermic transitions representing different structural changes can be seen because they become separated and they will move to higher temperatures. With limited water content, the swelling forces will be much less significant, and the process of gelatinization in a low moisture content environment could more accurately be defined as the “melting” of starch. Besides, the number of endotherms and enthalpies depended on amylose/amylopectin ratio, and the gelatinisation enthalpy of the amylopectin-rich starch was higher than that of the amylose-rich starch. Specifically, waxy and normal maize starches show a large gelatinization endotherm at about 70 °C; for normal maize starches, there was also a second endotherm at about 90 °C, considered as the phase transition within an amylose–lipid complex; In contrast, for high-amylose content starches (e.g. Gelose 50 and Gelose 80), there is a very broad endotherm in the temperature range between 65 and 115 °C, which is composed of the main gelatinization endotherm and the phase transition within an amylose–lipid complex. During
cooking Cooking, cookery, or culinary arts is the art, science, and craft of using heat In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy ...

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
retrogradation Retrogradation is the landward change in position of the front of a river delta with time. This occurs when the mass balance of sediment into the delta is such that the volume of incoming sediment is less than the volume of the delta that is lost ...
of the amylose. This process is responsible for the hardening of bread or
staling Staling, or "going stale", is a chemical and physical process in bread Bread is a staple food prepared from a dough of flour and water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteles ...
, and for the water layer on top of a starch gel ( syneresis). Certain starches, when mixed with water, will produce a
non-Newtonian fluid A non-Newtonian fluid is a fluid In physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department of knowledge which relates to the order of nature, ...
sometimes nicknamed "oobleck". Starch can also be dissolved or undergo gelation in
ionic liquids An ionic liquid (IL) is a salt Salt is a mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure ...
or metal chloride salt solutions. The thermal transition of starch is largely influenced by the ratio of ionic liquid/water. Aqueous ionic liquid with a certain ionic liquid/water ratio leads to the most effective structural disorganisation of some starches at significantly reduced temperature (even at room temperature). This phenomenon is very different from the dissolution of cellulose, as the latter occurs most efficiently in pure ionic liquids and any water contained in the ionic liquids will hinder the dissolution significantly. It is proposed that for starches with granule surface pores (e.g. millet, waxy maize, normal maize and wheat starches), the corrosion by the aqueous IL follows an inside-out pattern and the destruction to the granules is fast and even, whereas for starches with a relatively smooth surface (e.g. high-amylose maize, potato, purple yam and pea starches), the corrosion can only start from the surface and thus the change caused the aqueous IL is slow. Besides, starch, even high-amylose starch, can be fully dissolved by aqueous metal chloride salts (e.g. ZnCl2, CaCl2, and MgCl2) at moderate temperature (≤50 °C), and starch nanoparticles can form during this dissolution process.


Hydrolysis

The
enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates in ...

enzyme
s that break down or
hydrolyze Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile In chemistry, a nucleop ...

hydrolyze
starch into the constituent sugars are known as
amylase An amylase () is an enzyme Enzymes () are protein Proteins are large s and s that comprise one or more long chains of . Proteins perform a vast array of functions within organisms, including , , , providing and , and from one lo ...
s. Alpha-amylases are found in plants and in animals. Human
saliva Saliva (commonly referred to as spit) is an extracellular fluid In cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that studies life and living organisms, including t ...
is rich in amylase, and the
pancreas The pancreas is an Organ (anatomy), organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdominal cavity, abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine ...

pancreas
also secretes the enzyme. Individuals from populations with a high-starch diet tend to have more amylase genes than those with low-starch diets; Beta-amylase cuts starch into
maltose} Maltose ( or ), also known as maltobiose or malt sugar, is a disaccharide A disaccharide (also called a double sugar or ''biose'') is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosaccharides, disacchari ...

maltose
units. This process is important in the digestion of starch and is also used in
brewing Brewing is the production of beer Beer is one of the oldest and most widely consumed alcoholic drink An alcoholic drink is a drink A drink (or beverage) is a liquid A liquid is a nearly incompressible fluid In ph ...
, where amylase from the skin of seed grains is responsible for converting starch to maltose (
Malting Malting is a process of steeping Steeping is the soaking of an organic solid, such as leaves, in a liquid (usually water) to extract flavours or to soften it. The specific process of teas being prepared for drinking by leaving the leaves in ...
,
Mashing In brewing and distilling, mashing is the process of combining a mix of grains – typically malted barley with Adjuncts, supplementary grains such as Maize, corn, sorghum, rye, or wheat – known as the "grain bill" with water and then heating t ...

Mashing
). Given a heat of combustion of glucose of whereas that of starch is per mole of glucose monomer, hydrolysis releases about per mole, or per gram of glucose product.


Dextrinization

If starch is subjected to dry heat, it breaks down to form
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-(1→4) or α-(1→6) glycosidic bonds. Dextrins can be produced from st ...
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

A triiodide (I3) solution formed by mixing
iodine Iodine is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical ele ...

iodine
and
iodide An iodide ion An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that c ...

iodide
(usually from
potassium iodide Potassium iodide is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together ...
) is used to test for starch; a dark blue color indicates the presence of starch. The details of this reaction are not fully known, but recent scientific work using single crystal x-ray crystallography and comparative Raman spectroscopy suggests that the final starch-iodine structure is similar to an infinite polyiodide chain like one found in a pyrroloperylene-iodine complex. 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. Benedict's test and Fehling's test is also done to indicate the presence of starch.
Starch indicator Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets, ...
solution consisting of water, starch and iodide is often used in
redox Redox (reduction–oxidation, pronunciation: or ) is a type of chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substance A chemical substance is a form of matter ...

redox
titrations: in the presence of an
oxidizing agent An oxidizing agent, also known as an oxidant or oxidizer, is a substance that has the ability to oxidize other substances — in other words to electron acceptor, accept their electrons. Common oxidizing agents are oxygen, hydrogen peroxi ...

oxidizing agent
the solution turns blue, in the presence of
reducing agent A reducing agent (also called a reductant, reducer, or electron donor) is an element or compound that loses or "donates" an electron The electron is a subatomic particle (denoted by the symbol or ) whose electric charge is negative one ele ...
the blue color disappears because
triiodide In chemistry, triiodide usually refers to the triiodide ion, . This anion, one of the polyhalogen ions, is composed of three iodine Iodine is a chemical element with the Symbol (chemistry), symbol I and atomic number 53. The heaviest of t ...

triiodide
(I3) ions break up into three iodide ions, disassembling the starch-iodine complex. Starch solution was used as indicator for visualizing the periodic formation and consumption of triiodide intermediate in the Briggs-Rauscher oscillating reaction. The starch, however, changes the kinetics of the reaction steps involving triiodide ion. A 0.3% w/w 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). Each species of plant has a unique type of starch granules in granular size, shape and crystallization pattern. Under the
microscope A microscope (from grc, μικρός ''mikrós'' 'small' and ''skopeîn'' 'to look (at); examine, inspect') is a laboratory instrument used to examine objects that are too small to be seen by the naked eye Naked eye, also called bare ...

microscope
, starch grains stained with iodine illuminated from behind with
polarized light Polarization (also Also or ALSO may refer to: *Advanced Life Support in Obstetrics Advanced Life Support in Obstetrics (ALSO) is a program that was developed by the American Academy of Family Physicians (AAFP). This course helps physicians, ce ...
show a distinctive
Maltese cross The Maltese cross is a cross symbol, consisting of four " V" or arrowhead An arrowhead or point is the usually sharpened and hardened tip of an arrow, which contributes majority of the projectile mass and is responsible for impacting and penetr ...

Maltese cross
effect (also known as and
birefringence Birefringence is the property of a material having a that depends on the and propagation direction of . These optically materials are said to be birefringent (or birefractive). The birefringence is often quantified as the maximum difference b ...

birefringence
).


Food

Starch is the most common
carbohydrate is a disaccharide A disaccharide (also called a double sugar or ''biose'') is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosaccharides, disaccharides are simple sugars soluble in water. Three common ex ...
in the human diet and is contained in many
staple food A staple food, food staple, or simply a staple, is a food Food is any substance consumed to provide Nutrient, nutritional support for an organism. Food is usually of plant, animal or Fungus, fungal origin, and contains essential nutrients, ...

staple food
s. The major sources of starch intake worldwide are the
cereal A cereal is any Poaceae, grass cultivated (grown) for the edible components of its grain (botanically, a type of fruit called a caryopsis), composed of the endosperm, cereal germ, germ, and bran. The term may also refer to the resulting grain ...

cereal
s (
rice Rice is the seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was relea ...

rice
,
wheat Wheat is a grass widely cultivated for its seed, a cereal grain which is a worldwide staple food. The many species of wheat together make up the genus ''Triticum''; the most widely grown is common wheat Common wheat (''Triticum aestivum'' ...

wheat
, and
maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It can also be ...

maize
) and the
root vegetable Root vegetables are underground plant parts eaten by humans as food Food is any substance consumed to provide Nutrient, nutritional support for an organism. Food is usually of plant, animal or Fungus, fungal origin, and contains essential n ...
s (
potato The potato is a starch#Food, starchy tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial plant, perennial in the nightshade family Solanaceae. Wild potato species can be found thro ...

potato
es and
cassava ''Manihot esculenta'', commonly called cassava (), manioc, or yuca (among numerous regional names) is a woody shrub A shrub (or bush, but this is more of a gardening term) is a small- to medium-sized perennial woody plant. Unlike herb ...

cassava
). Many other starchy foods are grown, some only in specific climates, including
acorn The acorn, or oaknut, is the nut Nut often refers to: * Nut (fruit), a fruit composed of a hard shell and a seed * Nut (food), collective noun for dry and edible fruits or seeds * Nut (hardware), a fastener used with a bolt Nut or Nuts may al ...

acorn
s,
arrowroot Arrowroot is a starch Starch or amylum is a polymeric A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attrib ...
, ,
banana A banana is an elongated, edible fruit In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specia ...

banana
s,
barley Barley (''Hordeum vulgare''), a member of the grass family Poaceae () or Gramineae () is a large and nearly ubiquitous family In human society, family (from la, familia) is a group of people related either by consanguinity (by recogn ...

barley
,
breadfruit Breadfruit (''Artocarpus altilis'') is a species of flowering tree in the mulberry ''Morus'', a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank used in the biological classification of extant taxon, living ...

breadfruit
,
buckwheat Buckwheat (''Fagopyrum esculentum''), or common buckwheat, is a plant cultivated for its grain-like seeds and as a cover crop In agriculture Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture ...

buckwheat
, canna,
colocasia ''Colocasia'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circ ...
, katakuri, kudzu, Xanthosoma sagittifolium, malanga, millet, oats, oxalis tuberosa, oca, polynesian arrowroot, sago,
sorghum ''Sorghum'' is a genus of about 25 species of flowering plants in the grass family ( Poaceae). Some of these species are grown as cereals for human consumption and some in pastures for animals. One species, '' Sorghum bicolor'', was originally ...

sorghum
, sweet potatoes, rye, taro, chestnuts, Water caltrop, water chestnuts and yam (vegetable), yams, and many kinds of beans, such as vicia faba, favas, lentils, mung beans, peas, and chickpeas. Widely used prepared foods containing starch are bread, pancakes,
cereal A cereal is any Poaceae, grass cultivated (grown) for the edible components of its grain (botanically, a type of fruit called a caryopsis), composed of the endosperm, cereal germ, germ, and bran. The term may also refer to the resulting grain ...

cereal
s, noodles, pasta, porridge and tortilla. digestion, Digestive enzymes have problems digesting crystalline structures. Raw starch is digested poorly in the duodenum and small intestine, while bacterial degradation takes place mainly in the colon (anatomy), colon. When starch is cooked, the digestibility is increased. Starch gelatinization during cake baking can be impaired by sugar competing for water, preventing gelatinization and improving texture. Before the advent of processed foods, people consumed large amounts of uncooked and unprocessed starch-containing plants, which contained high amounts of
resistant starch Resistant starch (RS) is starch, including its degradation products, that escapes from digestion in the small intestine of healthy individuals. Resistant starch occurs naturally in foods but is also added to foods by the addition of dried raw foo ...
. Microbes within the large intestine fermented the starch, produced short-chain fatty acids, which are used as energy, and support the maintenance and growth of the microbes. More highly processed foods are more easily digested and release more glucose in the small intestine—less starch reaches the large intestine and more energy is absorbed by the body. It is thought that this shift in energy delivery (as a result of eating more processed foods) may be one of the contributing factors to the development of metabolic disorders of modern life, including obesity and diabetes. The amylose/amylopectin ratio, molecular weight and molecular fine structure influences the physicochemical properties as well as energy release of different types of starches. In addition, cooking and food processing significantly impacts starch digestibility and energy release. Starch can be classified as rapidly digestible, slowly digestible and resistant starch. Raw starch granules resist digestion by human enzymes and do not break down into glucose in the small intestine - they reach the large intestine instead and function as Prebiotic (nutrition), prebiotic dietary fiber. When starch granules are fully gelatinized and cooked, the starch becomes easily digestible and releases glucose quickly within the small intestine. When starchy foods are cooked and cooled, some of the glucose chains re-crystallize and become resistant to digestion again. Slowly digestible starch can be found in raw cereals, where digestion is slow but relatively complete within the small intestine.


Starch production

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, tapioca, arrowroot, and wheat, rice, and
potato starch The potato is a starch Starch or amylum is a consisting of numerous units joined by s. This is produced by most green s for energy storage. Worldwide, it is the most common carbohydrate in human diets, and is contained in large amount ...

potato starch
es. To a lesser extent, sources of refined starch are sweet potato, sago and mung bean. To this day, starch is 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 Starch gelatinization, pregelatinized starch.


Starch sugars

Starch can be hydrolyzed into simpler carbohydrates by acids, various
enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates in ...

enzyme
s, or a combination of the two. The resulting fragments are known as
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-(1→4) or α-(1→6) glycosidic bonds. Dextrins can be produced from st ...
s. The extent of conversion is typically quantified by ''dextrose equivalent'' (DE), which is roughly the fraction of the
glycosidic bond A glycosidic bond or glycosidic linkage is a type of covalent bond A covalent bond is a chemical bond A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. The bond may ...
s in starch that have been broken. These starch sugars are by far the most common starch based food ingredient and are used as sweeteners in many drinks and foods. They include: * Maltodextrin, a lightly hydrolyzed (DE 10–20) starch product used as a bland-tasting filler and thickener. * Various
glucose syrup Glucose is a simple sugar Sugar is the generic name for sweet-tasting, soluble carbohydrate is a disaccharide found in animal milk. It consists of a molecule of D-galactose and a molecule of D-glucose bonded by beta-1-4 glycosidic li ...
s (DE 30–70), also called corn syrups 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, until a substantial fraction of the glucose has been converted to fructose. In the U.S. high-fructose corn syrup is significantly cheaper than sugar, and is the principal sweetener used in processed foods and beverages. Fructose also has better microbiological stability. One kind of high fructose corn syrup, HFCS-55, is sweeter than sucrose because it is made with more fructose, while the sweetness of HFCS-42 is on par with sucrose. * Sugar alcohols, such as maltitol, erythritol, sorbitol, mannitol and hydrogenated starch hydrolysate, are sweeteners made by reducing sugars.


Modified starches

A modified starch 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 food starches are E number, E coded according to European Food Safety Authority and International Numbering System for Food Additives, INS coded Food Additives according to the Codex Alimentarius: * 1400 Dextrin * 1401 Acid-treated starch * 1402 Alkaline-treated starch * 1403 Bleached starch * 1404 Oxidized starch * 1405 Starches, enzyme-treated * 1410 Monostarch phosphate * 1412 Distarch phosphate * 1413 Phosphated distarch phosphate * 1414 Acetylation, Acetylated distarch phosphate * 1420 Starch acetate * 1422 Acetylated distarch adipate * 1440 Hydroxypropyl starch * 1442 Hydroxypropyl distarch phosphate * 1443 Hydroxypropyl distarch glycerol * 1450 Starch sodium octenyl succinate * 1451 Acetylation, Acetylated oxidized starch INS 1400, 1401, 1402, 1403 and 1405 are in the EU food ingredients without an E-number. Typical modified starches for technical applications are Paper chemicals#Cationic starch, cationic starches, hydroxyethyl starch and carboxymethylated starches.


Use as food additive

As an additive for food processing, 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. They function as thickeners, extenders, emulsion stabilizers and are exceptional binders in processed meats. 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 1,000 or so jelly beans. The jelly mix is then poured into the impressions and put onto a stove to set. This method greatly reduces the number of molds that must be manufactured.


Use in pharmaceutical industry

In the pharmaceutical industry, starch is also used as an excipient, as Tablet (pharmacy), tablet disintegrant, and as binder.


Resistant starch

Resistant starch is starch that escapes digestion in the small intestine of healthy individuals. High-amylose starch from corn has a higher gelatinization temperature than other types of starch, and retains its resistant starch content through baking, mild Food extrusion, extrusion and other food processing techniques. It is used as an insoluble dietary fiber in processed foods such as bread, pasta, cookies, crackers, pretzels and other low moisture foods. It is also utilized as a dietary supplement for its health benefits. Published studies have shown that resistant starch helps to improve insulin sensitivity, increases satiety, reduces pro-inflammatory biomarkers interleukin 6 and tumor necrosis factor alpha and improves markers of colonic function. It has been suggested that resistant starch contributes to the health benefits of intact whole grains.


Synthetic starch

In 2021, researchers reported the world's first Biobased economy#Agriculture, artificial synthesis of starch in the laboratory. A cell-free Biocatalysis, chemoenzymatic process was used to synthesize starch from CO2 and hydrogen. If the process is viable and can be scaled, it could substantially reduce land-, pesticide- and water-use as well as greenhouse gas emissions while increasing food security. The chemical pathway of 11 core reactions was drafted by Computational chemistry, computational pathway design and converts CO2 to starch at a rate that is ~8.5-fold higher than starch synthesis Corn starch, in maize.


Non-food applications


Papermaking

Papermaking is the largest non-food application for starches globally, consuming many millions of metric tons annually.NNFCC Renewable Chemicals Factsheet: Starch
/ref> 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 is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important stru ...

cellulose
and inorganic fillers. Cationic starches together with other retention and internal sizing agents help to give the necessary strength properties to the paper web formed in the papermaking process (wet strength), 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 sizing, surface sizing. 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 presses). Together with surface sizing agents 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 coatings as one of the binders for the coating formulations which include a mixture of pigments, binders and thickeners. Coated paper 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 glues are mostly based on unmodified native starches, plus some additive such as borax 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 prepared by mixing a vegetable starch in water (earlier preparations also had to be boiled), and is used in the laundry, laundering of clothes. Starch was widely used in Europe in the 16th and 17th centuries to stiffen the wide collars and Ruff (clothing), ruffs of fine linen which surrounded the necks of the well-to-do. During the 19th and early 20th century it was stylish to stiffen the collars and sleeves of men's shirts and the ruffles of women's petticoats by starching them before the clean clothes were ironing, ironed. Starch gave clothing smooth, crisp edges, and had an additional practical purpose: dirt and sweat from a person's neck and wrists would stick to the starch rather than to the fibers of the clothing. The dirt would wash away along with the starch; after laundering, the starch would be reapplied. Starch is available in Aerosol spray, spray cans, in addition to the usual granules to mix with water.


Bioplastic

Starch is an important natural polymer to make bioplastics. With water and plasticisers such as glycerol, starch can be processed into so-called "thermoplastic starch" using conventional polymer processing techniques such as extrusion, injection molding and compression molding. Since materials based on only native starch have poor processibility, mechanical properties and stability, more commonly modified starches (e.g. hydroxypropyl starch) are used and starch is combined with other polymers (preferably biodegradable polymers such as polycaprolactone), as some commercial products (e.g. PLANTIC™ HP and Mater-Bi®) available on the market.


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. 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 bag#Multiwall paper sacks, paper sack production, tube winding, Gum tape, 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 to create a very good adhesive. Sodium silicate can be added to reinforce these formula. *Textile chemicals from starch: warp (weaving), warp Textile warp sizing, sizing agents are used to reduce breaking of
yarn Yarn is a long continuous length of interlocked fibres, suitable for use in the production of textiles, sewing, crocheting, knitting, weaving, embroidery, or ropemaking. Thread (yarn), Thread is a type of yarn intended for sewing by hand or sewin ...
s during
weaving Weaving is a method of textile A textile is a flexible material made by creating an interlocking bundle of yarn Yarn is a long continuous length of interlocked fibres, suitable for use in the production of textiles, sewing, crocheti ...

weaving
. Starch is mainly used to size cotton based yarns. Modified starch is also used as textile printing thickener. *In oil exploration, starch is used to adjust the viscosity of drilling fluid, which is used to lubricate the drill head and suspend the grinding residue in petroleum extraction. *Starch is also used to make some packing peanuts, and some dropped ceiling, drop ceiling tiles. *In the printing industry, food grade starch is used in the manufacture of anti-set-off spray powder used to separate printed sheets of paper to avoid wet ink being set-off (printing), set off. *For body powder, powdered corn starch is used as a substitute for talcum powder, and similarly in other health and beauty products. *Starch is used to produce various bioplastics, synthetic polymers that are biodegradable. An example is polylactic acid based on glucose from starch. *Glucose from starch can be further fermented to
biofuel Biofuel is fuel that is produced through contemporary processes from biomass, rather than by the very slow geological processes involved in the formation of fossil fuels, such as oil. Since biomass technically can be used as a fuel directly (e. ...

biofuel
corn ethanol 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#Enzymatic hydrogen generation, Hydrogen production could use glucose from starch as the raw material, using enzymes.


Occupational safety and health

In the US the Occupational Safety and Health Administration (OSHA) has set the legal limit (Permissible exposure limit) for starch exposure in the workplace as 15 mg/m3 total exposure and 5 mg/m3 respiratory exposure over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a Recommended exposure limit (REL) of 10 mg/m3 total exposure and 5 mg/m3 respiratory exposure over an 8-hour workday.


See also

* Acrylamide, which is present in fried and baked foods * Destarch * Starch analysis


References


External links


CDC - NIOSH Pocket Guide to Chemical Hazards
information for workers {{Authority control Starch, Nutrition Carbohydrates Edible thickening agents Excipients Printing