Starch: Difference between revisions

{{Short description|Glucose polymer used as energy store in plants}}

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{{For-multi|the Urhobo cuisine dish known as starch|Usi (food)|the video game|Starch (video game)}}

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| ImageName = Cornstarch being mixed with water

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|Section1={{Chembox Identifiers

| CASNo = 9005-25-8

| CASNo_Ref = {{cascite|correct|CAS}}

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = 24SC3U704I

| EC_number = 232-679-6

| RTECS = GM5090000

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|Section2={{Chembox Properties

| Formula = ({{chem|C|6|H|10|O|5|)|''n''}}

| MolarMass = Variable

| Appearance = White powder

| Density = Variable<ref>{{cite book|title=Starch: Chemistry and Technology|first1=Roy L.|last1=Whistler|first2=James N.|last2=BeMiller|first3=Eugene F.|last3=Paschall|url=https://books.google.com/books?id=pvAzqk2pAIsC&dq=Starch%20has%20a%20variable%20density&pg=PP219|publisher=[[Elsevier Science]]|isbn=9780323139502|oclc=819646427|date=2 December 2012|page=219|quote=Starch has variable density depending on botanical origin, prior treatment, and method of measurement|access-date=13 May 2022|archive-date=14 May 2022|archive-url=https://web.archive.org/web/20220514073433/https://www.google.co.in/books/edition/Starch_Chemistry_and_Technology/pvAzqk2pAIsC?hl=en&gbpv=1&dq=Starch+has+a+variable+density&pg=PP219|url-status=live}}</ref>

| Solubility = insoluble (see [[starch gelatinization]])

| MeltingPt = decomposes

| Section4 = {{Chembox Thermochemistry

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| DeltaHc ={{convert|4.1788|kcal/g|kJ/g}}<ref name=CRC>''[[CRC Handbook of Chemistry and Physics]]'', 49th edition, 1968-1969, p. D-188.</ref> ([[Higher heating value]])

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|Section7={{Chembox Hazards

| ExternalSDS = [http://www.inchem.org/documents/icsc/icsc/eics1553.htm ICSC 1553]

| AutoignitionPtC = 410

| PEL = TWA 15 mg/m³ (total) TWA 5 mg/m³ (resp)<ref>{{PGCH|0567}}</ref>

[[File:Amylose2.svg|thumb|Structure of the [[amylose]] molecule]]

[[File:Amylopektin Sessel.svg|thumb|Structure of the [[amylopectin]] molecule]]

'''Starch''' or '''amylum''' is a [[polymeric]] [[carbohydrate]] consisting of numerous [[glucose]] units joined by [[glycosidic bond]]s. This [[polysaccharide]] is produced by most green [[plant]]s for energy storage. Worldwide, it is the most common carbohydrate in human diets, and is contained in large amounts in [[staple food]]s such as [[wheat]], [[potato]]es, [[maize]] (corn), [[rice]], and [[cassava]] (manioc).

Pure starch is a white, tasteless and odorless powder that is insoluble in cold water or [[Alcohol (chemistry)|alcohol]]. It consists of two types of molecules: the linear and [[helix|helical]] [[amylose]] and the branched [[amylopectin]]. Depending on the plant, starch generally contains 20 to 25% amylose and 75 to 80% amylopectin by weight.<ref>{{Cite book |last1=Brown |first1=W. H. |last2=Poon |first2=T. |date=2005 |title=Introduction to organic chemistry |edition=3rd |publisher=Wiley |isbn=978-0-471-44451-0 |page=604}}</ref> [[Glycogen]], the energy reserve of animals, is a more highly branched version of amylopectin.

In industry, starch is often converted into sugars, for example by [[malt]]ing. These sugars may be [[fermentation|fermented]] to produce [[ethanol]] in the manufacture of [[beer]], [[whisky]] and [[biofuel]]. In addition, sugars produced from processed starch are used in many processed foods.

Mixing most starches in warm water produces a paste, such as [[wheatpaste]], which can be used as a thickening, stiffening or gluing agent. The principal non-food, industrial use of starch is as an adhesive in the [[papermaking]] process. A similar paste, clothing or [[laundry starch]], can be applied to certain textile goods before ironing to stiffen them.

==Etymology==

The word "starch" is from a [[Germanic languages|Germanic]] root with the meanings "strong, stiff, strengthen, stiffen".<ref>New Shorter Oxford Dictionary, Oxford, 1993</ref>

Modern German ''Stärke'' (strength, starch) is related and refers to the main historical applications, its uses in textiles: [[Textile warp sizing|sizing]] [[yarn]] for [[weaving]], and starching [[linen]].

The [[Greek language|Greek]] term for starch, "amylon" (ἄμυλον), which means "not milled", is also related. It provides the root [[wikt:amyl|amyl]], which is used as a prefix for several carbon compounds related to or derived from starch (e.g. [[amyl alcohol]], [[amylose]], [[amylopectin]]).

==History==

Starch grains from the [[rhizome]]s of ''[[Typha]]'' (cattails, bullrushes) as [[flour]] have been identified from [[grinding stone]]s in Europe dating back to 30,000 years ago.<ref name="Revedin">{{cite journal |doi=10.1073/pnas.1006993107 |title=Thirty thousand-year-old evidence of plant food processing |date=2010 |last1=Revedin |first1=A. |last2=Aranguren |first2=B. |last3=Becattini |first3=R. |last4=Longo |first4=L. |last5=Marconi |first5=E. |last6=Lippi |first6=M. M. |last7=Skakun |first7=N. |last8=Sinitsyn |first8=A. |last9=Spiridonova |first9=E. |last10=Svoboda |first10=J. |journal=Proceedings of the National Academy of Sciences |volume=107 |issue=44 |pmid=20956317 |pages=18815–9 |pmc=2973873|display-authors=8 |bibcode=2010PNAS..10718815R |doi-access=free }}</ref> Starch grains from [[sorghum]] were found on grind stones in caves in [[Ngalue]], [[Mozambique]] dating up to 100,000 years ago.<ref>{{cite news|newspaper=The Telegraph|title=Porridge was eaten 100,000 years ago|date=18 Dec 2009|url=https://www.telegraph.co.uk/news/uknews/6834609/Porridge-was-eaten-100000-years-ago.html |archive-url=https://ghostarchive.org/archive/20220111/https://www.telegraph.co.uk/news/uknews/6834609/Porridge-was-eaten-100000-years-ago.html |archive-date=2022-01-11 |url-access=subscription |url-status=live}}{{cbignore}}</ref>

Pure extracted wheat starch paste was used in [[Ancient Egypt]], possibly to glue [[papyrus]].<ref>[[Pliny the Elder]], The ''[[Natural History (Pliny)]]'', Book XIII, Chapter 26, [https://www.perseus.tufts.edu/cgi-bin/ptext?doc=Perseus%3Atext%3A1999.02.0137&query=head%3D%23817 The paste used in preparation of paper] {{Webarchive|url=https://web.archive.org/web/20220514073439/http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.02.0137&redirect=true |date=2022-05-14 }}</ref> The extraction of starch is first described in the ''[[Natural History (Pliny)|Natural History]]'' of [[Pliny the Elder]] around 77–79 [[Common Era|CE]].<ref>[[Pliny the Elder]], The [[Natural History (Pliny)]], Book XIII, Chapter 17, [https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.02.0137%3Abook%3D18%3Achapter%3D17] {{Webarchive|url=https://web.archive.org/web/20210206042052/http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.02.0137%3Abook%3D18%3Achapter%3D17|date=2021-02-06}}</ref> Romans used it also in [[Cosmetics|cosmetic]] creams, to powder the hair and to [[Thickening agent|thicken]] sauces. Persians and Indians used it to make dishes similar to gothumai wheat [[halva]]. Rice starch as surface treatment of paper has been used in paper production in China since 700 CE.<ref>{{cite book |first=Dard |last=Hunter |date=1947 |title=Papermaking |publisher=DoverPublications |isbn=978-0-486-23619-3 |page=194}}</ref> In the mid eighth century production of paper that was [[wikt:sized|sized]] with wheat starch started in the Arabic world.<ref>{{cite magazine|url=https://cool.culturalheritage.org/coolaic/sg/bpg/annual/v05/bp05-11.html|title=A Brief Review of the History of Sizing and Resizing Practices|first=Karen|last=Garlick|magazine=The Book and Paper Group Annual|volume=5|year=1986|publisher=Book and Paper Group of the American Institute for Conservation of Historic and Artistic Works}}</ref> Laundry starch was first described in England in the beginning of the 15th century and was essential to make 16th century [[Ruff (clothing)|ruffed collars]].<ref>{{cite web|url=http://www.oldandinteresting.com/laundry-starch-history.aspx|title=History of starching fabric, Laundry starch: from medieval luxury to Victorian mass market|website=Old & Interesting|date=21 July 2010|access-date=30 March 2024}}</ref>

[[File:Starch granules of potato02.jpg|thumb|Potato starch granules in [[Cell (biology)|cells]] of the potato]]

[[File:Starch Granules in Endosperm of Zea Mays Embryo by Phase Contrast (40725881153).jpg|thumb|Starch in endosperm in embryonic phase of maize seed]]

Plants produce [[glucose]] from [[carbon dioxide]] and water by [[photosynthesis]]. The glucose is used to generate the chemical energy required for general [[metabolism]] as well as a precursor to myriad organic building blocks such as [[nucleic acids]], [[lipids]], [[proteins]], and structural polysaccharides such as [[cellulose]]. Most green plants store any extra glucose in the form of starch, which is packed into semicrystalline granules called starch or [[amyloplast]]s.<ref name="Zobel starch review">{{cite journal |last1=Zobel |first1=H.F. |title=Molecules to granules: a comprehensive starch review |journal=Starch/Starke |date=1988 |volume=40 |issue=2 |pages=44–50 |doi=10.1002/star.19880400203 }}</ref> Toward the end of the growing season, starch accumulates in twigs of trees near the buds. [[Fruit]], [[seed]]s, [[rhizome]]s, and [[tuber]]s store starch to prepare for the next growing season. Young plants live on this stored energy in their roots, seeds, and fruits until they can find suitable soil in which to grow.<ref>{{cite journal |last1=Bailey |first1=E.H.S. |last2=Long |first2=W.S. |title=On the occurrence of starch in green fruits |journal=Transactions of the Kansas Academy of Science |date=Jan 14, 1916 – Jan 13, 1917 |volume=28 |pages=153–155 |doi=10.2307/3624346 |jstor=3624346 }}</ref> The starch is also consumed at night when photosynthesis is not occurring.<!-- An exception is the family [[Asteraceae]] (asters, daisies and sunflowers), where starch is replaced by the [[fructan]] [[inulin]]. Inulin-like fructans are also present in grasses such as [[wheat]], in [[onion]]s and [[garlic]], [[bananas]], and [[asparagus]].<ref name="Vijn">{{cite journal |title=Fructan: more than a reserve carbohydrate? |first1=Irma |last1=Vijn | first2=Sjef |last2=Smeekens |journal=Plant Physiology |date=1999 |volume=120 |issue=2 |pages=351–360 |doi=10.1104/pp.120.2.351 |pmid=10364386 |doi-access=free|pmc=1539216 }}</ref>-->

Green algae and land-plants store their starch in the [[plastid]]s, whereas [[red algae]], [[glaucophyte]]s, [[cryptomonad]]s, [[dinoflagellate]]s and the parasitic [[apicomplexa]] store a similar type of polysaccharide called [[floridean starch]] in their [[cytosol]] or [[periplast]].<ref>{{cite journal | pmid=19940244 | year=2009 | last1=Dauvillée | first1=D. | last2=Deschamps | first2=P. | last3=Ral | first3=J. P. | last4=Plancke | first4=C. | last5=Putaux | first5=J. L. | last6=Devassine | first6=J. | last7=Durand-Terrasson | first7=A. | last8=Devin | first8=A. | last9=Ball | first9=S. G. | title=Genetic dissection of floridean starch synthesis in the cytosol of the model dinoflagellate Crypthecodinium cohnii | journal=Proceedings of the National Academy of Sciences of the United States of America | volume=106 | issue=50 | pages=21126–21130 | doi=10.1073/pnas.0907424106 | pmc=2795531 | bibcode=2009PNAS..10621126D | doi-access=free }}</ref>

Especially when hydrated, glucose takes up much space and is [[osmosis|osmotically]] active. Starch, on the other hand, being insoluble and therefore osmotically inactive, 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.<ref name="Blennow review">{{cite journal |last1=Blennow |first1=Andreas |last2=Engelsen |first2=Soren B |title=Helix-breaking news: fighting crystalline starch energy deposits in the cell |journal=Trends in Plant Science |date=10 Feb 2010 |volume=15 |issue=4 |pages=236–40 |doi=10.1016/j.tplants.2010.01.009 |pmid=20149714 |bibcode=2010TPS....15..236B }}</ref>

Amylose consists of long chains derived from glucose molecules connected by α-1,4-[[glycosidic bond|glycosidic linkage]]. Amylopectin is highly branched but also derived from glucose interconnected by α-1,6-[[glycosidic bond|glycosidic linkages.]] The same type of linkage is found in the animal reserve polysaccharide [[glycogen]]. By contrast, many structural polysaccharides such as [[chitin]], cellulose, and [[peptidoglycan]] are linked by [[glycosidic bond|β-glycosidic bonds]], which are more resistant to hydrolysis.<ref>{{cite journal|last1=Zeeman|first1=Samuel C.|last2=Kossmann|first2=Jens|last3=Smith|first3=Alison M.|title=Starch: Its Metabolism, Evolution, and Biotechnological Modification in Plants|journal=Annual Review of Plant Biology|date=June 2, 2010|volume=61|issue=1|pages=209–234|doi=10.1146/annurev-arplant-042809-112301|pmid=20192737}}</ref>

===Structure of starch particles===

Within plants, starch is stored in semi-crystalline granules. Each plant species has a distinctive starch granular size: rice starch is relatively small (about 2&nbsp;μm), [[potato starch]]es have larger granules (up to 100&nbsp;μm) while wheat and tapioca fall in-between.<ref name="Rosicka-Kaczmarek wheat chapter">{{cite book |last1=Rosicka-Kaczmarek |first1=Justyna |last2=Kwasniewska-Karolak |first2=Izabella |last3=Nebesny |first3=Ewa |last4=Komisarczyk |first4=Aleksandra |chapter=The Functionality of Wheat Starch |title=Starch in Food |date=2018 |publisher=Woodhead Publishing |location=Duxford, United Kingdom |isbn=978-0-08-100868-3 |page=331 |url=https://www.elsevier.com/books/starch-in-food/sjoo/978-0-08-100868-3 |access-date=2022-02-27 |archive-date=2022-02-27 |archive-url=https://web.archive.org/web/20220227211012/https://www.elsevier.com/books/starch-in-food/sjoo/978-0-08-100868-3 |url-status=live }}</ref> Unlike other botanical sources of starch, wheat starch has a bimodal size distribution, with both smaller and larger granules ranging from 2 to 55&nbsp;μm.<ref name="Rosicka-Kaczmarek wheat chapter" />

Some cultivated plant varieties have pure amylopectin starch without amylose, known as ''waxy starches''. The most used is [[waxy corn|waxy maize]], others are [[glutinous rice]] and [[waxy potato starch]]. Waxy starches undergo less [[Retrogradation (starch)|retrogradation]], resulting in a more stable paste. A maize cultivar with a relatively high proportion of amylose starch, [[amylomaize]], is cultivated for the use of its gel strength and for use as a [[resistant starch]] (a starch that resists digestion) in food products.

Plants synthesize starch in two types of tissues. The first type is storage tissues, for example, cereal endosperm, and storage roots and stems such as cassava and potato. The second type is green tissue, for example, leaves, where many plant species synthesize transitory starch on a daily basis. In both tissue types, starch is synthesized in a plastids (amyloplasts and chloroplasts).

The biochemical pathway involves conversion of [[glucose 1-phosphate]] to [[Adenosine diphosphate|ADP]]-glucose using the enzyme [[glucose-1-phosphate adenylyltransferase]]. This step requires energy in the form of [[Adenosine triphosphate|ATP]]. A number of [[starch synthase|starch synthases]] available in plastids then adds the ADP-glucose via α-1,4-[[glycosidic bond]] to a growing chain of glucose residues, liberating [[Adenosine diphosphate|ADP]]. 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 [[Glycogenesis|glycogen synthesis]].<ref>Nelson, D. (2013) Lehninger Principles of Biochemistry, 6th ed., W.H. Freeman and Company (p. 819)</ref> The small glucan chain, further agglomerate to form initials of starch granules.

The biosynthesis and expansion of granules represent a complex molecular event that can be subdivided into four major steps, namely, granule initiation, coalescence of small granules,<ref>{{Cite journal |last1=Bürgy |first1=Léo |last2=Eicke |first2=Simona |last3=Kopp |first3=Christophe |last4=Jenny |first4=Camilla |last5=Lu |first5=Kuan Jen |last6=Escrig |first6=Stephane |last7=Meibom |first7=Anders |last8=Zeeman |first8=Samuel C. |date=2021-11-26 |title=Coalescence and directed anisotropic growth of starch granule initials in subdomains of Arabidopsis thaliana chloroplasts |journal=Nature Communications |language=en |volume=12 |issue=1 |page=6944 |doi=10.1038/s41467-021-27151-5 |issn=2041-1723 |pmc=8626487 |pmid=34836943|bibcode=2021NatCo..12.6944B }}</ref> phase transition, and expansion. Several proteins have been characterized for their involvement in each of these processes. For instance, a chloroplast membrane-associated protein, MFP1, determines the sites of granule initiation.<ref>{{Cite journal |last1=Sharma |first1=Mayank |last2=Abt |first2=Melanie R. |last3=Eicke |first3=Simona |last4=Ilse |first4=Theresa E. |last5=Liu |first5=Chun |last6=Lucas |first6=Miriam S. |last7=Pfister |first7=Barbara |last8=Zeeman |first8=Samuel C. |date=2024-01-16 |title=MFP1 defines the subchloroplast location of starch granule initiation |journal=Proceedings of the National Academy of Sciences |language=en |volume=121 |issue=3 |pages=e2309666121 |doi=10.1073/pnas.2309666121 |issn=0027-8424|doi-access=free |pmid=38190535 |pmc=10801857 |bibcode=2024PNAS..12109666S }}</ref> Another protein named PTST2 binds to small glucan chains and agglomerates to recruit starch synthase 4 (SS4).<ref>{{Cite journal |last1=Seung |first1=David |last2=Boudet |first2=Julien |last3=Monroe |first3=Jonathan |last4=Schreier |first4=Tina B. |last5=David |first5=Laure C. |last6=Abt |first6=Melanie |last7=Lu |first7=Kuan-Jen |last8=Zanella |first8=Martina |last9=Zeeman |first9=Samuel C. |date=July 2017 |title=Homologs of PROTEIN TARGETING TO STARCH Control Starch Granule Initiation in Arabidopsis Leaves |journal=The Plant Cell |language=en |volume=29 |issue=7 |pages=1657–1677 |doi=10.1105/tpc.17.00222 |issn=1040-4651 |pmc=5559754 |pmid=28684429}}</ref> Three other proteins, namely, PTST3, SS5, and MRC, are also known to be involved in the process of starch granule initiation.<ref>{{Cite journal |last1=Seung |first1=David |last2=Schreier |first2=Tina B. |last3=Bürgy |first3=Léo |last4=Eicke |first4=Simona |last5=Zeeman |first5=Samuel C. |date=July 2018 |title=Two Plastidial Coiled-Coil Proteins Are Essential for Normal Starch Granule Initiation in Arabidopsis |journal=The Plant Cell |language=en |volume=30 |issue=7 |pages=1523–1542 |doi=10.1105/tpc.18.00219 |issn=1040-4651 |pmc=6096604 |pmid=29866647}}</ref><ref>{{Cite journal |last1=Vandromme |first1=Camille |last2=Spriet |first2=Corentin |last3=Dauvillée |first3=David |last4=Courseaux |first4=Adeline |last5=Putaux |first5=Jean-Luc |last6=Wychowski |first6=Adeline |last7=Krzewinski |first7=Frédéric |last8=Facon |first8=Maud |last9=D'Hulst |first9=Christophe |last10=Wattebled |first10=Fabrice |date=January 2019 |title=PII1: a protein involved in starch initiation that determines granule number and size in Arabidopsis chloroplast |url=https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.15356 |journal=New Phytologist |language=en |volume=221 |issue=1 |pages=356–370 |doi=10.1111/nph.15356 |pmid=30055112 |bibcode=2019NewPh.221..356V |issn=0028-646X}}</ref><ref>{{Cite journal |last1=Abt |first1=Melanie R. |last2=Pfister |first2=Barbara |last3=Sharma |first3=Mayank |last4=Eicke |first4=Simona |last5=Bürgy |first5=Léo |last6=Neale |first6=Isabel |last7=Seung |first7=David |last8=Zeeman |first8=Samuel C. |date=August 2020 |title=STARCH SYNTHASE5, a Noncanonical Starch Synthase-Like Protein, Promotes Starch Granule Initiation in Arabidopsis |journal=The Plant Cell |language=en |volume=32 |issue=8 |pages=2543–2565 |doi=10.1105/tpc.19.00946 |issn=1040-4651 |pmc=7401018 |pmid=32471861}}</ref> Furthermore, two proteins named ESV and LESV play a role in the aqueous-to-crystalline phase transition of glucan chains.<ref>{{Cite journal |last1=Liu |first1=Chun |last2=Pfister |first2=Barbara |last3=Osman |first3=Rayan |last4=Ritter |first4=Maximilian |last5=Heutinck |first5=Arvid |last6=Sharma |first6=Mayank |last7=Eicke |first7=Simona |last8=Fischer-Stettler |first8=Michaela |last9=Seung |first9=David |last10=Bompard |first10=Coralie |last11=Abt |first11=Melanie R. |last12=Zeeman |first12=Samuel C. |date=2023-05-26 |title=LIKE EARLY STARVATION 1 and EARLY STARVATION 1 promote and stabilize amylopectin phase transition in starch biosynthesis |journal=Science Advances |language=en |volume=9 |issue=21 |pages=eadg7448 |doi=10.1126/sciadv.adg7448 |issn=2375-2548 |pmc=10219597 |pmid=37235646|bibcode=2023SciA....9G7448L }}</ref> Several catalytically active starch synthases, such as SS1, SS2, SS3, and GBSS, are critical for starch granule biosynthesis and play a catalytic role at each step of granule biogenesis and expansion.<ref>{{Cite journal |last1=Pfister |first1=Barbara |last2=Zeeman |first2=Samuel C. |date=July 2016 |title=Formation of starch in plant cells |journal=Cellular and Molecular Life Sciences |language=en |volume=73 |issue=14 |pages=2781–2807 |doi=10.1007/s00018-016-2250-x |issn=1420-682X |pmc=4919380 |pmid=27166931}}</ref>

In addition to above proteins, [[Starch branching enzyme|starch branching enzymes (BEs)]] introduces α-1,6-glycosidic bonds between the glucose chains, creating the branched amylopectin. The starch debranching enzyme (DBE) [[isoamylase]] removes some of these branches. Several [[isoform]]s of these enzymes exist, leading to a highly complex synthesis process.<ref>{{cite journal |doi=10.1021/bm000133c |title=The Biosynthesis of Starch Granules |date=2001 |last1=Smith |first1=Alison M. |journal=Biomacromolecules |volume=2 |issue=2 |pages=335–41 |pmid=11749190}}</ref>

===Degradation===

The starch that is synthesized in plant leaves during the day is transitory: it serves as an energy source at night. Enzymes catalyze release of glucose from the granules. The insoluble, highly branched starch chains require [[phosphorylation]] in order to be accessible for degrading enzymes. The enzyme [[glucan, water dikinase]] (GWD) installs a phosphate at the C-6 position of glucose, close to the chain's 1,6-alpha branching bonds. A second enzyme, [[phosphoglucan, water dikinase]] (PWD) phosphorylates the glucose molecule at the C-3 position. After the second phosphorylation, the first degrading enzyme, [[beta-amylase]] (BAM) attacks the glucose chain at its non-reducing end. [[Maltose]] is the main product released. If the glucose chain consists of three or fewer molecules, BAM cannot release maltose. A second enzyme, [[disproportionating enzyme-1]] (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 fully degraded. 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.<ref name=Smith>{{cite journal| doi = 10.1146/annurev.arplant.56.032604.144257| pmid = 15862090| url = http://www.ccrc.uga.edu/~dmohnen/bcmb8020/Smith2005.pdf| journal = Annual Review of Plant Biology| volume = 56| pages = 73–98|date= 2005| last1 = Smith| first1 = Alison M.| title = Starch Degradation| last2 = Zeeman| first2 = Samuel C.| last3 = Smith| first3 = Steven M.| access-date = 2014-02-13| archive-url = https://web.archive.org/web/20150412040521/http://www.ccrc.uga.edu/~dmohnen/bcmb8020/Smith2005.pdf| archive-date = 2015-04-12| url-status = dead}}</ref>

The products of starch degradation are predominantly maltose<ref>{{cite journal |pmid=14566561 | doi=10.1007/s00425-003-1128-y | volume=218 | issue=3 | title=Maltose is the major form of carbon exported from the chloroplast at night |date=2004 | journal=Planta | pages=474–82 | last1 = Weise | first1 = SE | last2 = Weber | first2 = AP | last3 = Sharkey | first3 = TD| bibcode=2004Plant.218..474W | s2cid=21921851 }}</ref> and smaller amounts of glucose. These molecules are exported from the plastid to the cytosol, maltose via the maltose transporter and glucose by the [[plastidic glucose translocator]] (pGlcT).<ref>{{cite journal | pmc = 139927 | pmid=10810150 | volume=12 | issue=5 | title=Identification, purification, and molecular cloning of a putative plastidic glucose translocator | date=May 2000 | journal=Plant Cell | pages=787–802 | doi=10.1105/tpc.12.5.787 | last1 = Weber | first1 = A | last2 = Servaites | first2 = JC | last3 = Geiger | first3 = DR | display-authors = etal }}</ref> These two sugars are used for sucrose synthesis. [[Sucrose]] can then be used in the oxidative pentose phosphate pathway in the mitochondria, to generate ATP at night.<ref name=Smith/>

==Starch industry==

[[File:Corn syrup.jpg|thumb|[[Glucose syrup]]]]

[[File:Ballydugan Mill - geograph.org.uk - 199484.jpg|thumb|Starch mill at [[Ballydugan]] ([[Northern Ireland]]), built in 1792]]

[[File:West Philadela. starch works LCCN2016649106.tif|thumb|West Philadelphia Starch works at [[Philadelphia (Pennsylvania)]], 1850]]

[[File:Faultless Starch Company (5765985011).jpg|thumb|Faultless Starch Company at [[Kansas City]]]]

In addition to starchy plants consumed directly, 66 million tonnes of starch were processed industrially in 2008. By 2011, production had increased to 73 million tons.<ref>{{cite web| url = https://www.starch.eu/blog/2013/05/15/aaf-position-on-trade-and-competitiveness/| title = Starch Europe, AAF position on competitiveness, visited march 3 2019| access-date = 2019-03-03| archive-date = 2019-03-06| archive-url = https://web.archive.org/web/20190306043832/https://www.starch.eu/blog/2013/05/15/aaf-position-on-trade-and-competitiveness/| url-status = live}}</ref>

In the [[European Union|EU]] the [[Starch production|starch industry]] produced about 11 million tonnes in 2011, with around 40% being used for industrial applications and 60% for food uses,<ref name=nnfcc/> most of the latter as [[glucose syrup]]s.<ref>International Starch Institute Denmark, [http://www.starch.dk/isi/market/index.asp Starch production volume] {{Webarchive|url=https://web.archive.org/web/20210313181205/http://www.starch.dk/isi/market/index.asp |date=2021-03-13 }}</ref> 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.<ref>{{cite web| url = https://www.starch.eu/the-european-starch-industry/| title = Starch Europe, Industry, visited march 3 2019| access-date = 2019-03-03| archive-date = 2019-03-06| archive-url = https://web.archive.org/web/20190306044012/https://www.starch.eu/the-european-starch-industry/| url-status = live}}</ref>

The [[United States of America|US]] produced about 27.5 million tons of starch in 2017, of which about 8.2 million tons was [[high fructose syrup]], 6.2 million tons was glucose syrups, and 2.5 million tons were starch products.{{clarify|reason=high fructose syrup and glucose syrup are not starch|date=March 2021}} The rest of the starch was used for producing [[ethanol]] (1.6 billion gallons).<ref>{{cite web| url = https://corn.org/wp-content/uploads/2018/04/CRA-Industry-Overview-2017.pdf| title = CRA, Industry overview 2017, visited on march 3 2019| access-date = 2019-03-03| archive-date = 2019-03-06| archive-url = https://web.archive.org/web/20190306043731/https://corn.org/wp-content/uploads/2018/04/CRA-Industry-Overview-2017.pdf| url-status = live}}</ref><ref>{{cite web| url = https://www.starch.eu/blog/2015/02/27/position-on-the-eu-us-ttip/#return-note-11608-4| title = Starch Europe, Updated position on the EU-US Transatlantic Trade and Investment Partnership, visited on march 3 2019| access-date = 2019-03-03| archive-date = 2019-03-06| archive-url = https://web.archive.org/web/20190306043701/https://www.starch.eu/blog/2015/02/27/position-on-the-eu-us-ttip/#return-note-11608-4| url-status = live}}</ref>

===Industrial processing===

The starch industry extracts and refines starches from crops by wet grinding, washing, sieving and drying. Today, the main commercial refined starches are [[cornstarch]], [[tapioca]], arrowroot,<ref>{{cite web |url=https://www.bbc.co.uk/food/arrowroot |title=Arrowroot recipes |website=BBC Food |author=Hemsley + Hemsley |access-date=13 August 2017 |archive-date=3 August 2017 |archive-url=https://web.archive.org/web/20170803191901/http://www.bbc.co.uk/food/arrowroot |url-status=live }}</ref> and wheat, rice, and [[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.

Crude starch is processed on an industrial scale to [[maltodextrin]] and glucose syrups and fructose syrups. These massive conversions are mediated by a variety of enzymes, which break down the starch to varying extents. Here breakdown involves hydrolysis, i.e. cleavage of bonds between sugar subunits by the addition of water. Some sugars are isomerized. The processes have been described as occurring in two phases: liquefaction and saccharification. The liquefaction converts starch into [[dextrin]]s. Amylase is a key enzyme for producing dextrin. The saccharification converts dextrin into maltoses and glucose. Diverse enzymes are used in this second phase, including [[pullanase]] and other amylases.<ref>{{cite journal |doi=10.1016/S0168-1656(01)00407-2 |title=Properties and applications of starch-converting enzymes of the α-amylase family |date=2002 |last1=Van Der Maarel |first1=Marc J.E.C |last2=Van Der Veen |first2=Bart |last3=Uitdehaag |first3=Joost C.M |last4=Leemhuis |first4=Hans |last5=Dijkhuizen |first5=L. |journal=Journal of Biotechnology |volume=94 |issue=2 |pages=137–155 |pmid=11796168 |s2cid=32090939 |url=https://pure.rug.nl/ws/files/14695142/2002JBiotechnolvdMaarel.pdf }}</ref>

[[File:Stärkemehl 800 fach Polfilter.jpg|thumb|Corn starch, 800x magnified, under polarized light, showing characteristic [[extinction cross]]]]

[[File:Rice starch - microscopy.jpg|thumb|[[Rice]] starch under transmitted light microscopy. A characteristic of rice starch is that granules have an angular outline and tend to clump.]]

===Dextrinization===

If starch is subjected to dry heat, it breaks down to form [[dextrin]]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.<ref>{{Cite book|url=https://books.google.com/books?id=hZwfAgAAQBAJ&pg=PA138|page=138|title=Introduction to Polymer Chemistry: A Biobased Approach|last=Ph.D|first=Judit E. Puskas|date=2013-11-18|publisher=DEStech Publications, Inc|isbn=9781605950303|language=en|access-date=2022-01-03|archive-date=2022-05-14|archive-url=https://web.archive.org/web/20220514073439/https://books.google.com/books?id=hZwfAgAAQBAJ&pg=PA138|url-status=live}}</ref>

[[File:A Papuan woman extracts starch sago from the spongy center of the palm stems. (17821831174).jpg|thumb|[[Sago]] starch extraction from palm stems]]

<!-- {{noredirect|Starchy food}} links here-->

Starch is the most common [[carbohydrate]] in the human diet and is contained in many [[staple food]]s. The major sources of starch intake worldwide are the [[cereal]]s ([[rice]], [[wheat]], and [[maize]]) and the [[root vegetable]]s ([[potato]]es and [[cassava]]).<ref>Anne-Charlotte Eliasson (2004). ''Starch in food: Structure, function and applications''. Woodhead Publishing. {{ISBN|978-0-8493-2555-7}}.</ref> Many other starchy foods are grown, some only in specific climates, including [[acorn]]s, [[arrowroot]], [[arracacha]], [[banana]]s, [[barley]], [[breadfruit]], [[buckwheat]], [[canna (plant)|canna]], [[colocasia]], [[cuckoo-pint]], [[katakuri]], [[kudzu]], [[Xanthosoma sagittifolium|malanga]], [[millet]], [[oat]]s, [[oxalis tuberosa|oca]], [[polynesian arrowroot]], [[sago]], [[sorghum]], [[sweet potato]]es, [[rye]], [[taro]], [[chestnut]]s, [[Water caltrop|water chestnuts]], and [[yam (vegetable)|yams]], and many kinds of [[bean]]s, such as [[vicia faba|favas]], [[lentil]]s, [[mung bean]]s, [[pea]]s, and [[chickpea]]s.

Before processed foods, people consumed large amounts of uncooked and unprocessed starch-containing plants, which contained high amounts of [[resistant starch]]. Microbes within the large intestine ferment or consume the starch, producing [[short-chain fatty acids]], which are used as energy, and support the maintenance and growth of the microbes. Upon cooking, starch is transformed from an insoluble, difficult-to-digest granule into readily accessible glucose chains with very different nutritional and functional properties.<ref>{{cite journal |last1=Liu |first1=Jia |last2=Huang |first2=Shiqing |last3=Chao |first3=Chen |last4=Yu |first4=Jinglin |last5=Copeland |first5=Les |last6=Wang |first6=Shujun |title=Changes of starch during thermal processing of foods: current status and future directions |journal=Trends in Food Science & Technology |date=2022 |volume=119 |pages=320–337 |doi=10.1016/j.tifs.2021.12.011 |s2cid=245211899 |url=https://doi.org/10.1016/j.tifs.2021.12.011 |access-date=2022-02-27 |archive-date=2022-05-14 |archive-url=https://web.archive.org/web/20220514073444/https://www.sciencedirect.com/science/article/pii/S0924224421006683?via%3Dihub |url-status=live }}</ref>

In current diets, 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.<ref>{{cite journal |last1=Walter |first1=Jens |last2=Ley |first2=Ruth |title=The Human Gut Microbiome: Ecology and Recent Evolutionary Changes |journal=Annual Review of Microbiology |date=October 2011 |volume=65 |issue=1 |pages=422–429 |doi=10.1146/annurev-micro-090110-102830 |pmid=21682646 |url=https://digitalcommons.unl.edu/foodsciefacpub/369 |access-date=2020-10-13 |archive-date=2020-10-21 |archive-url=https://web.archive.org/web/20201021194320/https://digitalcommons.unl.edu/foodsciefacpub/369/ |url-status=live }}</ref>

The amylose/amylopectin ratio, molecular weight and molecular fine structure influences the physicochemical properties as well as energy release of different types of starches.<ref>{{cite journal |last1=Lindeboom |first1=Nienke |last2=Chang |first2=Peter R. |last3=Tyler |first3=Robert T. |title=Analytical, biochemical and physicochemical aspoects of starch granule size, with emphasis on small granule starches: a review |journal=Starch-Stärke |date=1 Apr 2004 |volume=56 |issue=3–4 |pages=89–99 |doi=10.1002/star.200300218 }}</ref> In addition, cooking and food processing significantly impacts starch digestibility and energy release. Starch has been classified as rapidly digestible starch, slowly digestible starch and resistant starch, depending upon its digestion profile.<ref>{{cite journal |last1=Englyst |first1=Hans N. |last2=Kingman |first2=S.M. |last3=Cummings |first3=John H. |title=Classification and measurement of nutritionally important starch fractions |journal=European Journal of Clinical Nutrition |date=October 1992 |volume=46 |issue=Suppl 2 |pages=S33-50 |pmid=1330528}}</ref> 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]].<ref name="Lockyer review">{{cite journal |last1=Lockyer |first1=S. |last2=Nugent |first2=A.P. |title=Health effects of resistant starch |journal=Nutrition Bulletin |date=5 Jan 2017 |volume=42 |issue=1 |pages=10–41 |doi=10.1111/nbu.12244 |doi-access=free }}</ref> 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.<ref name="Englyst definition">{{cite journal |last1=Englyst |first1=H.N. |last2=Kingman |first2=S.M. |last3=Cummings |first3=J.H. |title=Classification and measurement of nutritionally important starch fractions |journal=European Journal of Clinical Nutrition |date=Oct 1992 |volume=46 |issue=Suppl. 2 |pages=S33-50 |pmid=1330528 }}</ref> Widely used prepared foods containing starch are [[bread]], [[pancake]]s, [[cereal]]s, [[noodle]]s, [[pasta]], [[porridge]] and [[tortilla]].

During cooking with high heat, sugars released from starch can react with amino acids via the [[Maillard reaction]], forming [[advanced glycation end-product]]s (AGEs), contributing aromas, flavors and texture to foods.<ref>{{cite journal |last1=Ames |first1=Jennifer M. |title=Applications of the Maillard reaction in the food industry |journal=Food Chemistry |date=August 1998 |volume=62 |issue=4 |pages=431–439 |doi=10.1016/S0308-8146(98)00078-8 |url=https://www.sciencedirect.com/science/article/abs/pii/S0308814698000788 |access-date=2022-02-27 |archive-date=2022-02-27 |archive-url=https://web.archive.org/web/20220227175703/https://www.sciencedirect.com/science/article/abs/pii/S0308814698000788 |url-status=live }}</ref> One example of a dietary AGE is [[acrylamide]]. Recent evidence suggests that the intestinal fermentation of dietary AGEs may be associated with [[insulin resistance]], [[atherosclerosis]], [[diabetes]] and other inflammatory diseases.<ref>{{cite journal |last1=Kellow |first1=Nicole J. |last2=Coughlan |first2=Melinda T. |title=Effect of diet-derived advanced glycation end products on inflammation |journal=Nutrition Reviews |date=November 2015 |volume=73 |issue=11 |pages=737–759 |doi=10.1093/nutrit/nuv030 |pmid=26377870 |url=https://academic.oup.com/nutritionreviews/article/73/11/737/1922904?login=false |access-date=2022-02-27 |archive-date=2022-02-27 |archive-url=https://web.archive.org/web/20220227182322/https://academic.oup.com/nutritionreviews/article/73/11/737/1922904?login=false |url-status=live |doi-access=free }}</ref><ref>{{cite journal |last1=Snelson |first1=Matthew |last2=Coughlan |first2=Melinda T. |title=Dietary advanced glycation end products: digestion, metabolism and modulation of gut microbial ecology |journal=Nutrients |date=Jan 22, 2019 |volume=11 |issue=2 |page=215 |doi=10.3390/nu11020215 |pmid=30678161 |pmc=6413015 |doi-access=free }}</ref> This may be due to the impact of AGEs on intestinal permeability.<ref>{{cite journal |last1=Snelson |first1=Matthew |last2=Lucut |first2=Elisa |last3=Coughlan |first3=Melinda T. |title=The role of AGE-RAGE signaling as a modulator of gut permeability in diabetes |journal=International Journal of Molecular Sciences |date=2022 |volume=23 |issue=3 |page=1766 |doi=10.3390/ijms23031766 |pmid=35163688 |pmc=8836043 |doi-access=free }}</ref>

Starch gelatinization during cake [[baking]] can be impaired by sugar competing for [[water]], preventing gelatinization and improving texture.

===Starch sugars===

[[File:Karoadvert-1917.jpg|thumb|upright|Karo corn syrup advert 1917]]

[[File:Niagara Corn Starch (3093767094).jpg|thumb|upright|Niagara corn starch advert [[1880s]]]]

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]]s (DE 30–70), also called [[corn syrup]]s in the US, viscous solutions used as sweeteners and thickeners in many kinds of processed foods.

* 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.<ref>{{cite web| url = http://www.beveragedaily.com/Markets/Sugar-is-much-much-bigger-Rocketing-HFCS-prices-don-t-spook-Coke-CEO| title = Beverage daily: 'Sugar is much, much bigger': Rocketing HFCS prices don't spook Coke CEO| date = 30 July 2012| access-date = 2013-03-23| archive-date = 2013-03-30| archive-url = https://web.archive.org/web/20130330081748/http://www.beveragedaily.com/Markets/Sugar-is-much-much-bigger-Rocketing-HFCS-prices-don-t-spook-Coke-CEO| url-status = live}}</ref> 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.<ref>{{cite web|url = http://www.elmhurst.edu/~chm/vchembook/549sweet.html|title = Sweetners – Introduction|publisher = Elmhurst College|author = Ophardt, Charles|access-date = 2010-10-23|archive-date = 2010-09-23|archive-url = https://web.archive.org/web/20100923050238/http://elmhurst.edu/~chm/vchembook/549sweet.html|url-status = live}}</ref><ref>{{cite web|url = http://www.foodproductdesign.com/articles/2008/12/hfcs-how-sweet-it-is.aspx|title = HFCS: How Sweet It Is|date = December 2, 2008|first = John S.|last = White|access-date = October 23, 2010|archive-date = July 11, 2011|archive-url = https://web.archive.org/web/20110711015207/http://www.foodproductdesign.com/articles/2008/12/hfcs-how-sweet-it-is.aspx|url-status = live}}</ref>

===Modified starches===

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]]:<ref>[http://www.fao.org/ag/agn/jecfa-additives/specs/Monograph1/Additive-287.pdf Modified Starches] {{Webarchive|url=https://web.archive.org/web/20180329080648/http://www.fao.org/ag/agn/jecfa-additives/specs/Monograph1/Additive-287.pdf |date=2018-03-29 }}. CODEX ALIMENTARIUS published in FNP 52 Add 9 (2001)</ref>

* 1400 [[Dextrin]]

* 1401 [[Acid]]-treated starch

* 1402 [[Alkaline]]-treated starch

* 1404 [[Redox|Oxidized]] starch

* 1412 [[Distarch phosphate]]

* 1413 [[Phosphated distarch phosphate]]

* 1414 [[Acetylation|Acetylated]] distarch phosphate

* 1420 [[Acetylated starch]]

* 1440 [[Hydroxypropyl starch]]

* 1450 [[Starch sodium octenyl succinate]]

INS 1400, 1401, 1402, 1403 and 1405 are in the EU food ingredients without an E-number.<ref>{{cite web| url = https://webgate.ec.europa.eu/foods_system/main/?event=substances.search&substances.pagination=14| title = Database on Food Additives EU, visited December 6 2020| access-date = 2020-12-06| archive-date = 2021-08-17| archive-url = https://web.archive.org/web/20210817205109/https://webgate.ec.europa.eu/foods_system/main/?event=substances.search&substances.pagination=14| url-status = live}}</ref> Typical modified starches for technical applications are [[Paper chemicals#Cationic starch|cationic starch]]es, [[hydroxyethyl starch]], [[Chloroacetic acid|carboxymethylated]] starches and thiolated starches.<ref name="Jelkmann 2018">{{cite journal | vauthors = Jelkmann M, Bonengel S, Menzel C, Markovic S, Bernkop-Schnürch A |title= New perspectives of starch: Synthesis and in vitro assessment of novel thiolated mucoadhesive derivatives| journal = Int J Pharm |date=2018 |volume=546 |issue= 1–2|pages=70–77 |doi=10.1016/j.ijpharm.2018.05.028|pmid=29758345 |s2cid= 44071363}}</ref>

===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 bean]]s and [[wine gum]]s 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.

===Resistant starch===

{{Main|Resistant starch}}

[[Resistant starch]] is starch that escapes digestion in the small intestine of healthy individuals. High-amylose starch from wheat or 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,<ref>{{cite journal |last1=Rashed |first1=Aswir Abd |last2=Saparuddin |first2=Fatin |last3=Rathi |first3=Devi-Nair Gunasegavan |last4=Nasir |first4=Nur Najihah Mond |last5=Lokman |first5=Ezarul Faradianna |title=Effects of resistant starch interventions on metabolic biomarkers in pre-diabetes and diabetes adults |journal=Frontiers in Nutrition |date=2022 |volume=8 |page=793414 |doi=10.3389/fnut.2021.793414 |pmid=35096939 |pmc=8790517 |doi-access=free }}</ref><ref>{{cite web |last1=Balentine |first1=Douglas |title=Letter announcing decision for a health claim for high-amylose maize starch (containing type-2 resistant starch) and reduced risk of type 2 diabetes mellitus (Docket Number FDA-2015-Q-2352 |url=https://www.regulations.gov/docket?D=FDA-2015-Q-2352 |website=U.S. Food & Drug Administration |publisher=United States Government |access-date=19 December 2016 |archive-date=20 December 2016 |archive-url=https://web.archive.org/web/20161220200555/https://www.regulations.gov/docket?D=FDA-2015-Q-2352 |url-status=live }}</ref> reduces pro-inflammatory biomarkers [[interleukin 6]] and [[tumor necrosis factor alpha]]<ref>{{cite journal |last1=Vahdat |first1=Mahsa |last2=Hosseini |first2=Seyed Ahmad |last3=Khalatbari Mohseni |first3=Golsa |last4=Heshmati |first4=Javad |last5=Rahimlou |first5=Mehran |title=Effects of resistant starch interventions on circulating inflammatory biomarkers: a systematic review and meta-analysis of randomized controlled trials |journal=Nutrition Journal |date=15 Apr 2020 |volume=19 |issue=1 |page=Article 33 |doi=10.1186/s12937-020-00548-6 |pmid=32293469 |doi-access=free |pmc=7158011 }}</ref><ref>{{cite journal |last1=Lu |first1=J. |last2=Ma |first2=B. |last3=Qiu |first3=X. |last4=Sun |first4=Z. |last5=Xiong |first5=K. |title=Effects of resistant starch supplementation on oxidative stress and inflammation biomarkers: a systematic review and meta-analysis of randomized controlled trials |journal=Asia Pac J Clin Nutr |date=30 Dec 2021 |volume=30 |issue=4 |pages=614–623 |doi=10.6133/apjcn.202112_30(4).0008 |pmid=34967190 |url=https://pubmed.ncbi.nlm.nih.gov/34967190/ |access-date=27 February 2022 |archive-date=27 February 2022 |archive-url=https://web.archive.org/web/20220227181626/https://pubmed.ncbi.nlm.nih.gov/34967190/ |url-status=live }}</ref> and improves markers of colonic function.<ref>{{cite journal |doi=10.1111/j.1467-3010.2005.00481.x |title=Health properties of resistant starch |date=2005 |last1=Nugent |first1=A. P. |journal=Nutrition Bulletin |volume=30 |pages=27–54|doi-access=free }}</ref>

It has been suggested that resistant starch contributes to the health benefits of intact whole grains.<ref>{{cite journal |doi=10.1155/2012/829238 |title=Whole Grains, Legumes, and the Subsequent Meal Effect: Implications for Blood Glucose Control and the Role of Fermentation |date=2012 |last=Higgins |first=Janine A. |journal=Journal of Nutrition and Metabolism |volume=2012 |page=829238 |pmid=22132324 |pmc=3205742|doi-access=free }}</ref>

=== Synthetic starch ===

A cell-free [[Biocatalysis|chemoenzymatic]] process has been demonstrated to synthesize starch from CO₂ and hydrogen.y. 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]].<ref>{{cite news |title=World-first artificial synthesis of starch from CO2 outperforms nature |url=https://newatlas.com/science/artificial-synthesis-starch-from-co2/ |access-date=18 October 2021 |work=New Atlas |date=28 September 2021 |archive-date=18 October 2021 |archive-url=https://web.archive.org/web/20211018122807/https://newatlas.com/science/artificial-synthesis-starch-from-co2/ |url-status=live }}</ref><!--https://phys.org/news/2021-09-chinese-scientists-starch-synthesis-carbon.html--><ref>{{cite journal |last1=Cai |first1=Tao |last2=Sun |first2=Hongbing |last3=Qiao |first3=Jing |last4=Zhu |first4=Leilei |last5=Zhang |first5=Fan |last6=Zhang |first6=Jie |last7=Tang |first7=Zijing |last8=Wei |first8=Xinlei |last9=Yang |first9=Jiangang |last10=Yuan |first10=Qianqian |last11=Wang |first11=Wangyin |last12=Yang |first12=Xue |last13=Chu |first13=Huanyu |last14=Wang |first14=Qian |last15=You |first15=Chun |last16=Ma |first16=Hongwu |last17=Sun |first17=Yuanxia |last18=Li |first18=Yin |last19=Li |first19=Can |last20=Jiang |first20=Huifeng |last21=Wang |first21=Qinhong |last22=Ma |first22=Yanhe |title=Cell-free chemoenzymatic starch synthesis from carbon dioxide |journal=Science |date=24 September 2021 |volume=373 |issue=6562 |pages=1523–1527 |doi=10.1126/science.abh4049 |pmid=34554807 |bibcode=2021Sci...373.1523C |s2cid=237615280 |language=EN|doi-access=free }}</ref>

==Non-food applications==

[[File:AdhesivesForHouseUse006.jpg|thumb|Starch adhesive]]

[[Papermaking]] is the largest non-food application for starches globally, consuming many millions of metric tons annually.<ref name=nnfcc>{{cite web |url=http://www.nnfcc.co.uk/publications/nnfcc-renewable-chemicals-factsheet-starch |title=NNFCC Renewable Chemicals Factsheet: Starch |access-date=2011-05-25 |archive-date=2021-03-13 |archive-url=https://web.archive.org/web/20210313181212/https://www.nnfcc.co.uk/publications/nnfcc-renewable-chemicals-factsheet-starch |url-status= live }}</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]] 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.

===Adhesives===

Starch is used in the manufacture of various '''adhesives''' or glues<ref>{{cite web |url=http://www.ars.usda.gov/is/ar/archive/apr00/wood0400.htm |title=Stuck on Starch: A new wood adhesive |publisher=US Department of Agriculture |date=2000 |access-date=2011-01-14 |archive-date=2010-04-13 |archive-url=https://web.archive.org/web/20100413134900/http://ars.usda.gov/is/AR/archive/apr00/wood0400.htm |url-status=live }}</ref> for book-binding, [[wallpaper adhesive]]s, [[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 {{convert|50|–|70|C}} to create a very good adhesive. Sodium silicate can be added to reinforce these formula.

A related 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.

* Clothing or [[laundry starch]] is used in the [[Laundry|laundering]] of clothes. It was widely used in Europe in the 16th and 17th centuries.

* Textile chemicals from starch: [[Warp (weaving)|warp]] [[Textile warp sizing|sizing agents]] are used to reduce breaking of [[yarn]]s during [[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 peanut]]s, and some [[dropped ceiling|drop ceiling]] tiles.

* In the [[printing]] industry, food grade starch<ref>{{cite web | url = http://www.russell-webb.com/anti_set_off_powder/soluble_anti-set-off-powder.html

| title = Spray Powder | publisher = Russell-Webb | access-date = 2007-07-05

| archive-url = https://web.archive.org/web/20070809214841/http://www.russell-webb.com/anti_set_off_powder/soluble_anti-set-off-powder.html <!-- Bot retrieved archive --> |archive-date = 2007-08-09}}</ref> 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 [[bioplastic]]s, synthetic polymers that are biodegradable. An example is [[polylactic acid]] based on glucose from starch.

* Glucose from starch can be further fermented to [[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.<ref>{{cite web| url = http://www.ethanol.org/index.php?id=37&parentid=8| title = American coalition for ethanol, Ethanol facilities| access-date = 2011-06-02| archive-date = 2011-06-25| archive-url = https://web.archive.org/web/20110625100931/http://ethanol.org/index.php?id=37&parentid=8| url-status = live}}</ref>

*In the pharmaceutical industry, starch is also used as an [[excipient]], as [[Tablet (pharmacy)|tablet]] disintegrant, and as binder. Synthetic amylose made from cellulose has a well-controlled degree of polymerization. Therefore, it can be used as a potential drug deliver carrier.<ref name="pnas.org">{{cite journal |last1=You |first1=C. |last2=Chen |first2=H. |last3=Myung |first3=S. |last4=Sathitsuksanoh |first4=N. |last5=Ma |first5=H. |last6=Zhang |first6=X.-Z. |last7=Li |first7=J. |last8=Zhang |first8=Y.- H. P. |date=April 15, 2013 |title=Enzymatic transformation of nonfood biomass to starch |journal=Proceedings of the National Academy of Sciences |volume=110 |issue=18 |pages=7182–7187 |bibcode=2013PNAS..110.7182Y |doi=10.1073/pnas.1302420110 |pmc=3645547 |pmid=23589840 |doi-access=free}}</ref>

==Chemical tests==

{{Main|Iodine test}}

[[File:Wheat starch granules.JPG|thumb|Granules of wheat starch, stained with iodine, photographed through a light microscope]]

A solution of [[Polyiodide|triiodide]] (I₃⁻) (formed by mixing [[iodine]] and [[potassium iodide]]) can be used to test for starch. The colorless solution turns dark blue in the presence of starch.<ref>{{cite journal |last1=Madhu |first1=Sheri |last2=Evans |first2=Hayden A. |last3=Doan-Nguyen |first3=Vicky V. T. |last4=Labram |first4=John G. |last5=Wu |first5=Guang |last6=Chabinyc |first6=Michael L. |last7=Seshadri |first7=Ram |last8=Wudl |first8=Fred |title=Infinite Polyiodide Chains in the Pyrroloperylene-Iodine Complex: Insights into the Starch-Iodine and Perylene-Iodine Complexes |journal=Angewandte Chemie International Edition |date=4 July 2016 |volume=55 |issue=28 |pages=8032–8035 |doi=10.1002/anie.201601585|pmid=27239781 |doi-access=free }}</ref> 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.

== Safety==

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&nbsp;mg/m³ total exposure and 5&nbsp;mg/m³ respiratory exposure over an eight-hour workday. The [[National Institute for Occupational Safety and Health]] (NIOSH) has set a [[Recommended exposure limit]] (REL) of 10&nbsp;mg/m³ total exposure and 5&nbsp;mg/m³ respiratory exposure over an eight-hour workday.<ref>{{Cite web |title=CDC – NIOSH Pocket Guide to Chemical Hazards – Starch |url=https://www.cdc.gov/niosh/npg/npgd0567.html |website=CDC.gov |access-date=2015-11-21 |archive-date=2015-09-24 |archive-url=https://web.archive.org/web/20150924140643/http://www.cdc.gov/niosh/npg/npgd0567.html |url-status=live }}</ref>

* [[Destarch]]

* [[Resistant starch]]

* [[Starch analysis]]

{{Clear}}

==References==

{{Wiktionary|starch}}

{{Commons category|Starch}}

* [https://www.cdc.gov/niosh/npg/npgd0567.html CDC - NIOSH Pocket Guide to Chemical Hazards], information for workers

* [https://www.red-letter.com.ua/en/interesting/interesting-facts-about-starch/ Facts about starch], information for workers

{{Carbohydrates}}

{{Botany}}

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[[Category:Starch| ]]

[[Category:Carbohydrates]]

[[Category:Nutrition]]