Editing Tannin

{{short description|Class of astringent, bitter plant polyphenolic chemical compounds}}
{{For|the mythical creature|Tannin (monster)}}
{{distinguish|Tanin (disambiguation)}}
{{Use dmy dates|date=January 2020}}
[[File:Tannic acid.svg|thumb|Representative chemical structure of a [[tannic acid]], a type of tannin]]
[[File:Tannin heap.jpeg|thumb|Tannin powder (mixture of compounds)]]
[[File:Bottle of tannic acid.jpg|thumb|A bottle of [[tannic acid]] [[Solution (chemistry)|solution]] in [[water]] ]]

'''Tannins''' (or '''tannoids''') are a class of [[astringent]], [[polyphenol]]ic [[biomolecule]]s that bind to and [[Precipitation (chemistry)|precipitate]] [[protein]]s and various other organic compounds including [[amino acid]]s and [[alkaloid]]s. The term ''tannin'' is widely applied to any large [[polyphenol]]ic compound containing sufficient [[hydroxyl]]s and other suitable groups (such as [[carboxyl]]s) to form strong complexes with various [[macromolecule]]s.

The term ''tannin'' (from scientific French ''tannin'', from French ''tan'' "crushed oak bark", ''tanner'' "to tan", cognate with [[English language|English]] ''tanning'', [[Medieval Latin]] ''tannare'', from Proto-Celtic ''*tannos'' "oak") refers to the abundance of these compounds in [[oak]] [[Bark (botany)|bark]], which was used in [[Tanning (leather)|tanning]] animal [[Hide (skin)|hides]] into [[leather]].

The tannin compounds are widely distributed in many species of plants, where they play a role in protection from [[predation]] (acting as [[pesticides]]) and might help in regulating plant growth.<ref>{{cite book |first1=Katie E. |last1=Ferrell |last2=Thorington |first2=Richard W. |title=Squirrels: the animal answer guide |url=https://archive.org/details/squirrelsanimala00wric |url-access=limited |publisher=Johns Hopkins University Press |location=Baltimore |year=2006 |page=[https://archive.org/details/squirrelsanimala00wric/page/n109 91] |isbn=978-0-8018-8402-3 }}</ref> The [[astringency]] from the tannins is what causes the dry and puckery feeling in the mouth following the consumption of unripened fruit, red wine or tea.<ref>{{cite book |last=McGee |first=Harold |title=On food and cooking: the science and lore of the kitchen |publisher=Scribner |location=New York |year=2004 |page=714 |isbn=978-0-684-80001-1 }}</ref> Likewise, the destruction or modification of tannins with time plays an important role when determining harvesting times.

Tannins have [[molecular weight]]s ranging from 500 to over 3,000<ref name="Bate-Smith">{{cite book |author=Bate-Smith and Swain |chapter=Flavonoid compounds |editor1=Florkin M. |editor2=Mason H. S |title=Comparative biochemistry |publisher=Academic Press |location=New York |year=1962 |pages=75–809 |volume=III }}</ref> ([[gallic acid]] [[ester]]s) and up to 20,000 [[Dalton (unit)|dalton]]s ([[proanthocyanidin]]s).

== Structure and classes of tannins ==
There are three major classes of tannins: Shown below are the base unit or monomer of the tannin. Particularly in the flavone-derived tannins, the base shown must be (additionally) heavily hydroxylated and polymerized in order to give the high molecular weight [[polyphenol]] motif that characterizes tannins. Typically, tannin molecules require at least 12 hydroxyl groups and at least five phenyl groups to function as protein binders.<ref name="ref 1">{{Cite web|url=http://pharmaxchange.info/notes/cognosy/tannins.html|archive-url=https://web.archive.org/web/20150104040231/http://pharmaxchange.info/notes/cognosy/tannins.html|url-status=dead|title=Notes on Tannins from PharmaXChange.info|archive-date=4 January 2015}}</ref>

{| class="wikitable"
|- style="text-align:center;"
!scope=row|Base unit / scaffold
|[[File:Gallic acid.svg|x100px]]<br />[[Gallic acid]]
|[[File:Phloroglucin.svg|x100px]]<br />[[Phloroglucinol]]
| colspan="2" |[[File:Flavan-3-ol.svg|x100px]]<br />[[Flavan-3-ol]]
|-
!scope=row|Polymer class
|[[Hydrolyzable tannin]]s
|[[Phlorotannin]]s
|[[Condensed tannin]]s<ref name=":0">{{cite book |title=Chemistry and Significance of Condensed Tannins |author=Richard W. Hemingway |author2=Joseph J. Karchesy |page=113 |isbn=978-1-4684-7511-1}}</ref>
|[[Phlobatannin]]s (C-ring isomerized condensed tannins)<ref name=":0" />
|-
!Sources
|Plants
|[[Brown algae]]
|Plants
|Tree heartwood 
|}
[[Oligostilbenoid]]s (oligo- or polystilbenes) are oligomeric forms of [[stilbenoid]]s and constitute a minor class of tannins.<ref>{{cite journal | last1 = Boralle | first1 = N. | last2 = Gottlieb | first2 = H. E. | last3 = Gottlieb | first3 = O. R. | last4 = Kubitzki | first4 = K. | last5 = Lopes | first5 = L. M. X. | last6 = Yoshida | first6 = M. | last7 = Young | first7 = M. C. M. | year = 1993 | title = Oligostilbenoids from ''Gnetum venosum'' | journal = Phytochemistry | volume = 34 | issue = 5| pages = 1403–1407 | doi=10.1016/0031-9422(91)80038-3 | bibcode = 1993PChem..34.1403B }}</ref>

=== Pseudo-tannins<span class="anchor" id="Pseudo tannins"></span> ===
Pseudo-tannins are low molecular weight compounds associated with other compounds. They do not change color during the [[Goldbeater's skin]] [[#Tests for tannins|test]], unlike hydrolysable and condensed tannins, and cannot be used as tanning compounds.<ref name="ref 1" /> Some examples of pseudo tannins and their sources are:<ref>{{cite book|author=Ashutosh Kar|title=Pharmacognosy And Pharmacobiotechnology|url=https://books.google.com/books?id=PlMi4XvHCYoC&pg=PA44|access-date=31 January 2011|year=2003|publisher=New Age International|isbn=978-81-224-1501-8|pages=44–|url-status=live|archive-url=https://web.archive.org/web/20130602035552/http://books.google.com/books?id=PlMi4XvHCYoC&pg=PA44|archive-date=2 June 2013|df=dmy-all}}</ref>

{| class="wikitable"
|-
! Pseudo tannin !! Source(s)
|-
| [[Gallic acid]] || [[Rhubarb]]
|-
| [[Flavan-3-ol]]s (''Catechins'') || [[Camellia sinensis|Tea]], [[acacia]], [[catechu]], [[Theobroma cacao|cocoa]], [[guarana]]
|-
| [[Chlorogenic acid]] || [[Nux vomica (herbalism)|Nux-vomica]], [[coffee]], [[Mate (beverage)|mate]]
|-
| Ipecacuanhic acid || ''[[Carapichea ipecacuanha]]''
|}

== History ==
[[Ellagic acid]], [[gallic acid]], and [[pyrogallic acid]] were first discovered by chemist [[Henri Braconnot]] in 1831.<ref name="Grasser">{{Cite book|url=https://archive.org/details/synthetictannins032496mbp|title=Synthetic Tannins|isbn=978-1-4067-7301-9|last1=Grasser|first1=Georg|year=1922|others=F. G. A. Enna. (trans.)|publisher=Read Books }}</ref>{{rp|20}} [[Julius Löwe]] was the first person to synthesize ellagic acid by heating [[gallic acid]] with [[arsenic acid]] or silver oxide.<ref name="Grasser" />{{rp|20}}<ref>{{cite journal |last=Löwe |title= |journal=Zeitschrift für Chemie |year=1868 |volume=4 |page=603}}</ref>

[[Maximilian Nierenstein]] studied natural phenols and tannins<ref>{{Cite journal
| last1 = Drabble | first1 = E.
| last2 = Nierenstein | first2 = M.
| title = On the Rôle of Phenols, Tannic Acids, and Oxybenzoic Acids in Cork Formation
| journal = Biochemical Journal
| volume = 2
| issue = 3
| pages = 96–102.1
| year = 1907
| pmid = 16742048
| pmc = 1276196
| doi = 10.1042/bj0020096
}}</ref> found in different plant species. Working with [[Arthur George Perkin]], he prepared [[ellagic acid]] from [[algarobilla]] and certain other [[fruit]]s in 1905.<ref>{{Cite journal | last1 = Perkin | first1 = A. G. | last2 = Nierenstein | first2 = M. | doi = 10.1039/CT9058701412 | title = CXLI – Some oxidation products of the hydroxybenzoic acids and the constitution of ellagic acid. Part I | journal = Journal of the Chemical Society, Transactions | volume = 87 | pages = 1412–1430 | year = 1905 | url = https://zenodo.org/record/1657036 }}</ref> He suggested its formation from [[galloyl]]-[[glycine]] by ''[[Penicillium]]'' in 1915.<ref>{{Cite journal
| last1 = Nierenstein | first1 = M.
| title = The Formation of Ellagic Acid from Galloyl-Glycine by ''Penicillium''
| journal = The Biochemical Journal
| volume = 9
| issue = 2
| pages = 240–244
| year = 1915
| pmid = 16742368
| pmc = 1258574
 | doi=10.1042/bj0090240
}}</ref> [[Tannase]] is an enzyme that Nierenstein used to produce m-[[digallic acid]] from [[gallotannin]]s.<ref>{{Cite journal
| last1 = Nierenstein | first1 = M.
| title = A biological synthesis of m-digallic acid
| journal = The Biochemical Journal
| volume = 26
| issue = 4
| pages = 1093–1094
| year = 1932
| pmid = 16744910
| pmc = 1261008
 | doi=10.1042/bj0261093
}}</ref> He proved the presence of [[catechin]] in [[cocoa bean]]s in 1931.<ref>{{Cite journal | last1 = Adam | first1 = W. B. | last2 = Hardy | first2 = F. | last3 = Nierenstein | first3 = M. | title = The Catechin of the Cacao Bean| journal = Journal of the American Chemical Society | volume = 53 | issue = 2 | pages = 727–728 | year = 1931 | doi = 10.1021/ja01353a041 | bibcode = 1931JAChS..53..727A }}</ref> He showed in 1945 that [[luteic acid]], a molecule present in the myrobalanitannin, a tannin found in the fruit of ''[[Terminalia chebula]]'', is an intermediary compound in the synthesis of [[ellagic acid]].<ref>{{Cite journal
| last1 = Nierenstein | first1 = M.
| last2 = Potter | first2 = J.
| title = The distribution of myrobalanitannin
| journal = The Biochemical Journal
| volume = 39
| issue = 5
| pages = 390–392
| year = 1945
| pmid = 16747927
| pmc  = 1258254
 | doi=10.1042/bj0390390
}}</ref>

At these times, molecule formulas were determined through [[combustion analysis]]. The discovery in 1943 by Martin and Synge of [[paper chromatography]] provided for the first time the means of surveying the phenolic constituents of plants and for their separation and identification. There was an explosion of activity in this field after 1945, including prominent work by [[Edgar Charles Bate-Smith]] and [[Tony Swain (chemist)|Tony Swain]] at [[Cambridge University]].<ref name="Haslam">{{cite journal|last=Haslam|first=Edwin|title=Vegetable tannins – Lessons of a phytochemical lifetime|journal=Phytochemistry|year=2007|issue=22–24|pages=2713–2721|doi=10.1016/j.phytochem.2007.09.009|pmid=18037145|volume=68|bibcode=2007PChem..68.2713H }}</ref>

In 1966, [[Edwin Haslam]] proposed a first comprehensive definition of plant polyphenols based on the earlier proposals of Bate-Smith, Swain and Theodore White, which includes specific structural characteristics common to all phenolics having a tanning property. It is referred to as the White–Bate-Smith–Swain–Haslam (WBSSH) definition.<ref>{{cite web|last=Quideau|first=Stéphane|url=http://www.groupepolyphenols.com/index.php?option=com_content&view=article&id=53&Itemid=59&b528026c36a38313c3bc0e90a25fbe0c=7012a845601d61b99d4b8fbc24b709de|title=Why bother with Polyphenols|publisher=Groupe Polyphenols|date=22 September 2009|access-date=21 August 2012|url-status=live|archive-url=https://web.archive.org/web/20120310221945/http://www.groupepolyphenols.com/index.php?option=com_content&view=article&id=53&Itemid=59&b528026c36a38313c3bc0e90a25fbe0c=7012a845601d61b99d4b8fbc24b709de|archive-date=10 March 2012|df=dmy-all}}{{self-published source|date=May 2011}}</ref>{{Self-published inline|date=May 2011}}

== Occurrence ==
Tannins are distributed in species throughout the [[plant kingdom]]. They are commonly found in both [[gymnosperm]]s and [[angiosperm]]s. Mole (1993) studied the distribution of tannin in 180 families of [[dicotyledon]]s and 44 families of [[monocotyledon]]s (Cronquist). Most families of dicot contain tannin-free species (tested by their ability to precipitate proteins). The best known families of which all species tested contain tannin are: [[Aceraceae]], [[Actinidiaceae]], [[Anacardiaceae]], [[Bixaceae]], [[Burseraceae]], [[Combretaceae]], [[Dipterocarpaceae]], [[Ericaceae]], [[Grossulariaceae]], [[Myricaceae]] for dicot and [[Najadaceae]] and [[Typhaceae]] in Monocot. To the family of the oak, [[Fagaceae]], 73% of the species tested contain tannin. For those of acacias, [[Mimosaceae]], only 39% of the species tested contain tannin, among [[Solanaceae]] rate drops to 6% and 4% for the [[Asteraceae]]. Some families like the [[Boraginaceae]], [[Cucurbitaceae]], [[Papaveraceae]] contain no tannin-rich species.<ref>{{cite journal |author=Simon Mole |title=The Systematic Distribution of Tannins in the Leaves of Angiosperms: A Tool for Ecological Studies |journal=Biochemical Systematics and Ecology |volume=21 |issue=8 |pages=833–846 |year=1993|doi=10.1016/0305-1978(93)90096-A|bibcode=1993BioSE..21..833M }}</ref>

The most abundant polyphenols are the [[condensed tannin]]s, found in virtually all families of plants, and comprising up to 50% of the dry weight of leaves.<ref>{{cite journal |title=Les tannins dans les bois tropicaux |language=fr |last=Doat |first=J. |journal=Bois et Forêts des Tropiques |year=1978 |volume=182 |pages=34–37 |doi=10.19182/bft1978.182.a19337 |doi-access=free |url=http://agritrop.cirad.fr/444167/1/document_444167.pdf }}</ref><ref>{{cite book |last1=Kadam |first1=S. S. |last2=Salunkhe|first2=D. K. |last3=Chavan|first3=J. K. |title=Dietary tannins: consequences and remedies |publisher=CRC Press |location=Boca Raton |year=1990 |page=177 |isbn=978-0-8493-6811-0 }}</ref>

===Cellular localization===
{{more references |section |date=September 2021}}
In all vascular plants studied, tannins are manufactured by a [[chloroplast]]-derived [[organelle]], the [[tannosome]].<ref>{{cite journal |doi=10.1093/aob/mct168 |volume=112 |title=The tannosome is an organelle forming condensed tannins in the chlorophyllous organs of Tracheophyta |year=2013 |journal=Annals of Botany |pages=1003–1014 |last1=Brillouet |first1=J.-M. |issue=6 |pmid=24026439 |pmc=3783233}}</ref> Tannins are mainly physically located in the [[vacuole]]s or surface wax of plants. These storage sites keep tannins active against plant predators, but also keep some tannins from affecting plant metabolism while the plant tissue is alive.

Tannins are classified as [[ergastic substance]]s, i.e., non-protoplasm materials found in cells. Tannins, by definition, precipitate proteins. In this condition, they must be stored in organelles able to withstand the protein precipitation process. [[Idioblast]]s are isolated plant cells which differ from neighboring tissues and contain non-living substances. They have various functions such as storage of reserves, excretory materials, pigments, and minerals. They could contain oil, latex, gum, resin or pigments etc. They also can contain tannins. In Japanese persimmon (''[[Diospyros kaki]]'') fruits, tannin is accumulated in the vacuole of tannin cells, which are idioblasts of parenchyma cells in the flesh.<ref>{{cite journal |last1=Kanzaki |first1=Shinya |last2=Yonemori |first2=Keizo |last3=Sugiura |first3=Akira |last4=Sato |first4=Akihiko |last5=Yamada |first5=Masahiko |year=2001  |title=Identification of Molecular Markers Linked to the Trait of Natural Astringency Loss of Japanese Persimmon (''Diospyros kaki'') Fruit |journal=Journal of the American Society for Horticultural Science |volume=126 |issue=1 |pages=51–55 |doi=10.21273/JASHS.126.1.51 |url=http://journal.ashspublications.org/content/126/1/51.full.pdf+html |archive-url=https://web.archive.org/web/20150904065618/http://journal.ashspublications.org/content/126/1/51.full.pdf+html |archive-date=4 September 2015|doi-access=free }})</ref>

=== Presence in soils ===
{{see also|Soil pH}}
The [[convergent evolution]] of tannin-rich plant communities has occurred on nutrient-poor acidic soils throughout the world. Tannins were once believed to function as anti-herbivore defenses, but more and more ecologists now recognize them as important controllers of decomposition and nitrogen cycling processes. As concern grows about global warming, there is great interest to better understand the role of polyphenols as regulators of carbon cycling, in particular in northern boreal forests.<ref>{{cite journal|pmid=10802549|year=2000|last1=Hättenschwiler|first1=S.|title=The role of polyphenols in terrestrial ecosystem nutrient cycling|journal=Trends in Ecology & Evolution|volume=15|issue=6|pages=238–243|last2=Vitousek|first2=PM|doi=10.1016/S0169-5347(00)01861-9|doi-access=free}}</ref>

[[Leaf litter]] and other decaying parts of kauri (''[[Agathis australis]]''), a tree species found in New Zealand, decompose much more slowly than those of most other species. Besides its acidity, the plant also bears substances such as waxes and phenols, most notably tannins, that are harmful to [[microorganism]]s.<ref>{{cite journal | last1 = Verkaik | first1 = Eric | last2 = Jongkindet | first2 = Anne G. | last3 = Berendse | first3 = Frank | year = 2006 | title = Short-term and long-term effects of tannins on nitrogen mineralisation and litter decomposition in kauri (''Agathis australis'' (D. Don) Lindl.) forests | journal = Plant and Soil | volume = 287 | issue = 1–2| pages = 337–345 | doi = 10.1007/s11104-006-9081-8 | bibcode = 2006PlSoi.287..337V | s2cid = 23420808 }}</ref>

=== Presence in water and wood ===
The [[Leaching (chemistry)|leaching]] of highly [[water]] [[Solubility|soluble]] tannins from decaying vegetation and leaves along a stream may produce what is known as a [[blackwater river]]. Water flowing out of [[bog]]s has a characteristic brown color from dissolved [[peat]] tannins. The presence of tannins (or [[humic acid]]) in [[Water well|well water]] can make it smell bad or taste bitter, but this does not make it unsafe to drink.<ref>{{Cite web|url=http://www.gov.ns.ca/nse/water/docs/droponwaterFAQ_HumicSubstances.pdf|archive-url=https://web.archive.org/web/20130517071315/http://www.gov.ns.ca/nse/water/docs/droponwaterFAQ_HumicSubstances.pdf|url-status=dead|title=Tannins, lignins and humic acids in well water on www.gov.ns.ca|archive-date=17 May 2013}}</ref>

Tannins leaching from an unprepared driftwood decoration in an aquarium can cause pH lowering and coloring of the water to a tea-like tinge. A way to avoid this is to boil the [[wood]] in water several times, discarding the water each time. Using peat as an [[Substrate (aquarium)|aquarium substrate]] can have the same effect. Many hours of boiling the driftwood may need to be followed by many weeks or months of constant soaking and many water changes before the water will stay clear. Raising the water's [[pH level]], e.g. by adding [[Sodium bicarbonate|baking soda]], will accelerate the process of leaching.<ref>[http://www.aqualifesupport.com/getArticle.php?ArtID=413 Preparing Driftwood for Your Freshwater Aquarium] {{webarchive|url=https://web.archive.org/web/20110707154303/http://www.aqualifesupport.com/getArticle.php?ArtID=413 |date=7 July 2011 }}</ref>

Tannins in water can lead to feather staining on wild and domestic [[Anseriformes|waterfowl]] which frequent the water; [[mute swan]]s, which are typically white in colour, can often be observed with reddish-brown staining as a result of coming into contact with dissolved tannins, though dissolved [[iron]] compounds also play a role.<ref>{{Cite web |date=2017-08-23 |title=Mute Swan {{!}} Bird Identification Guide {{!}} Bird Spot |url=https://www.birdspot.co.uk/bird-identification/mute-swan |access-date=2024-12-29 |language=en-GB}}</ref>

[[Softwood]]s, while in general much lower in tannins than hardwoods,<ref>{{cite journal|title=Polyflavonoid tannins ? a main cause of soft-rot failure in CCA-treated timber|first1=A.|last1=Pizzi|first2=W. E.|last2=Conradie|first3=A.|last3=Jansen|date=28 October 1986|journal=Wood Science and Technology|volume=20|issue=1|pages=71–81|doi=10.1007/BF00350695|s2cid=21250123}}</ref> are usually not recommended for use in an aquarium<ref>{{Cite web|url=https://www.petfish.net/kb/entry/194|archive-url=https://web.archive.org/web/20110724003958/http://www.petfish.net/kb/entry/194/|url-status=dead|title=Driftwood Do's & Don'ts – Pet Fish|archive-date=24 July 2011}}</ref> so using a [[hardwood]] with a very light color, indicating a low tannin [[Concentration|content]], can be an easy way to avoid tannins. Tannic [[acid]] is brown in color, so in general white woods have a low tannin content. Woods with a lot of yellow, red, or brown coloration to them (like cedar, redwood, red oak, etc.) tend to contain a lot of tannin.<ref>{{Cite web|url=http://www.houserepairtalk.com/f45/carpet-hardwood-floor-8686/|archive-url=https://web.archive.org/web/20110417042435/http://www.houserepairtalk.com/f45/carpet-hardwood-floor-8686/|url-status=dead|title=Tannin and hardwood flooring|archive-date=17 April 2011}}</ref>

{{Gallery
|align=center
|File:Tannin rich fresh water draining into Cox Bight from Freney Lagoon.jpg|Tannin-rich fresh water draining into Cox Bight from Freney Lagoon, Southwest Conservation Area, Tasmania, Australia
|File:Bogwood Betta.jpg|[[Bog-wood]] (similar to, but not, [[driftwood]]) in an [[aquarium]], turning the [[water]] a tea-like brown
|File:Tête de cygne sur les étangs de Brimeux en vallée de Canche Marais de Marenla 3 aout 2017a 02.jpg|A [[mute swan]] with reddish-brown staining on the top of its head, caused by exposure to dissolved tannins and [[iron]] compounds in water
|File:Upper Tahquamenon falls Panoramic view.jpg|Upper Tahquamenon falls Panoramic view
|File:TWC Ōpārara • Nimmo • MRD 13.jpg|The tannin-rich [[Oparara River]] in the West Coast region of New Zealand|title=}}

== Extraction ==
There is no single protocol for [[Extraction (chemistry)|extracting]] tannins from all plant material. The procedures used for tannins are widely variable.<ref name="Hagerman1998">''The Tannin Handbook'', Ann E. Hagerman, 1998 ([http://www.users.muohio.edu/hagermae/ book] {{webarchive|url=https://web.archive.org/web/20140128054221/http://www.users.muohio.edu/hagermae/ |date=28 January 2014 }})</ref> It may be that [[acetone]] in the extraction solvent increases the total yield by inhibiting interactions between tannins and [[protein]]s during extraction<ref name="Hagerman1998" /> or even by breaking hydrogen bonds between tannin-protein complexes.<ref>"Condensed tannins". Porter L. J., 1989, in ''Natural Products of Woody Plants I'', Rowe J. W. (ed), Springer-Verlag: Berlin, Germany, pages 651–690</ref>

== Tests for tannins ==
There are three groups of methods for the analysis of tannins: precipitation of proteins or alkaloids, reaction with phenolic rings, and depolymerization.<ref>{{cite book | doi = 10.1007/978-1-4615-3476-1_15 | title=Plant Polyphenols | year=1992 | pages=259–280 | last1 = Scalbert | first1 = Augustin| chapter=Quantitative Methods for the Estimation of Tannins in Plant Tissues | isbn=978-1-4613-6540-2 }}</ref>

=== Alkaloid precipitation ===
Alkaloids such as [[caffeine]], [[cinchonine]], [[quinine]] or [[strychnine]], precipitates polyphenols and tannins. This property can be used in a quantitation method.<ref>Plant Polyphenols: Synthesis, Properties, Significance. Richard W. Hemingway, Peter E. Laks, Susan J. Branham (page 263)</ref>

=== Goldbeater's skin test ===
When [[goldbeater's skin]] or ox skin is dipped in [[Hydrochloric acid|HCl]], rinsed in water, soaked in the tannin solution for 5 minutes, washed in water, and then treated with 1% [[Iron(II) sulfate|FeSO<sub>4</sub>]] solution, it gives a blue black color if tannin was present.<ref>{{Cite book |last=Prakashan |first=Nirali |url=https://books.google.com/books?id=KwYIsLRyDp4C&dq=tannin+Goldbeater%27s+skin+test&pg=SL1-PA5 |title=Pharmacognosy |date=2009 |publisher=Nirali Prakashan |isbn=978-81-963961-5-2 |language=en}}</ref>

=== Ferric chloride test ===
The following describes the use of [[Ferric chloride test|ferric chloride (FeCl3) test]]s for [[natural phenol|phenolics]] in general: Powdered plant leaves of the test plant (1.0&nbsp;g) are weighed into a beaker and 10&nbsp;ml of distilled water are added. The mixture is boiled for five minutes. Two drops of 5% FeCl<sub>3</sub> are then added. Production of a greenish precipitate is an indication of the presence of tannins.{{cn|date=April 2025}} Alternatively, a portion of the water extract is diluted with distilled water in a ratio of 1:4 and few drops of 10% ferric chloride solution is added. A blue or green color indicates the presence of tannins (Evans, 1989).<ref>{{cite journal |last1=Yisa |first1=J. |title=Phytochemical analysis and antimicrobial activity of ''Scoparia dulcis'' and ''Nymphaea lotus'' |journal=Australian Journal of Basic and Applied Sciences |date=2009 |volume=3 |issue=4 |pages=3975–3979 |url=http://www.insipub.com/ajbas/2009/3975-3979.pdf}}</ref>

=== Other methods ===
The hide-powder method is used in tannin analysis for [[leather]] tannin and the Stiasny method for [[wood adhesive]]s.<ref>"Tannin analysis of Acacia mearnsii bark – a comparison of the hide-powder and Stiasny methods". Zheng G.C., Lin Y.L. and Yazaki Y., ''ACIAR Proceedings Series'', 1991, No. 35, pp. 128–131 ([http://www.cabdirect.org/abstracts/19920657723.html;jsessionid=F49F74287B59E2847142A9BFED7349DC abstract] {{webarchive|url=https://web.archive.org/web/20140709035011/http://www.cabdirect.org/abstracts/19920657723.html;jsessionid=F49F74287B59E2847142A9BFED7349DC |date=9 July 2014 }})</ref><ref>Study on Fast Determination Content of Condensed Tannin Using Stiasny Method. Chen Xiangming, Chen Heru and Li Weibin, Guangdong Chemical Industry, 2006–07 ([http://en.cnki.com.cn/Article_en/CJFDTOTAL-GDHG200607012.htm abstract] {{webarchive|url=https://web.archive.org/web/20150402162931/http://en.cnki.com.cn/Article_en/CJFDTOTAL-GDHG200607012.htm |date=2 April 2015 }})</ref> Statistical analysis reveals that there is no significant relationship between the results from the hide-powder and the Stiasny methods.<ref>{{cite journal | last1 = Guangcheng | first1 = Zheng | last2 = Yunlu | first2 = Lin | last3 = Yazaki | first3 = Y. | year = 1991 | title = Bark tannin contents of Acacia mearnsii provenances and the relationship between the hide-powder and the Stiasny methods of estimation | journal = Australian Forestry | volume = 54 | issue = 4| pages = 209–211 | doi = 10.1080/00049158.1991.10674579 | bibcode = 1991AuFor..54..209G }}</ref><ref>''Leather Chemists' Pocket-Book: A Short Compendium of Analytical Methods''. [[Henry Richardson Procter]], Edmund Stiasny and Harold Brumwel, E. & F.N. Spon, Limited, 1912–223 pages ([https://archive.org/details/leatherchemists00brumgoog book at Internet Archive] {{webarchive|url=https://web.archive.org/web/20161216075444/https://books.google.com/books?id=BrtJAAAAIAAJ&oe=UTF-8 |date=16 December 2016 }})</ref>

;Hide-powder method
400&nbsp;mg of sample tannins are dissolved in 100&nbsp;ml of distilled water. 3&nbsp;g of slightly chromated hide-powder previously dried in vacuum for 24h over CaCl<sub>2</sub> are added and the mixture stirred for 1 h at ambient temperature. The suspension is filtered without vacuum through a sintered glass filter. The weight gain of the hide-powder expressed as a percentage of the weight of the starting material is equated to the percentage of tannin in the sample.

;Stiasny's method
100&nbsp;mg of sample tannins are dissolved in 10&nbsp;ml distilled water. 1&nbsp;ml of 10M HCl and 2&nbsp;ml of 37% [[formaldehyde]] are added and the mixture heated under reflux for 30 min. The reaction mixture is filtered while hot through a sintered glass filter. The precipitate is washed with hot water (5× 10&nbsp;ml) and dried over CaCl<sub>2</sub>. The yield of tannin is expressed as a percentage of the weight of the starting material.

=== Reaction with phenolic rings ===
The bark tannins of ''[[Commiphora angolensis]]'' have been revealed by the usual color and precipitation reactions and by quantitative determination by the methods of Löwenthal-Procter and of Deijs<ref name="Cardoso">Chemical study of bark from Commiphora angolensis Engl. Cardoso Do Vale, J., Bol Escola Farm Univ Coimbra Edicao Cient, 1962, volume 3, page 128 ([http://eurekamag.com/research/024/318/chemical-study-bark-commiphora-angolensis-engl.php abstract] {{webarchive|url=https://web.archive.org/web/20140607001810/http://eurekamag.com/research/024/318/chemical-study-bark-commiphora-angolensis-engl.php |date=7 June 2014 }})</ref> ([[formalin]]-[[hydrochloric acid]] method).<ref>{{cite journal |last1=Deijs |first1=W. B. |title=Catechins isolated from tea leaves |journal=Recueil des Travaux Chimiques des Pays-Bas |date=1939|volume=58 |issue=9 |pages=805–830 |doi=10.1002/recl.19390580907}}</ref>

Colorimetric methods have existed such as the Neubauer-Löwenthal method which uses [[potassium permanganate]] as an oxidizing agent and [[Indigo dye|indigo]] [[sulfate]] as an indicator, originally proposed by Löwenthal in 1877.<ref>{{cite journal |last1=Löwenthal |first1=J. |title=Ueber die Bestimmung des Gerbstoffs |journal=Zeitschrift für Analytische Chemie |date=December 1877 |volume=16 |issue=1 |pages=33–48 |doi=10.1007/BF01355993|s2cid=95511307 |language=de|url=https://zenodo.org/record/2179227 }}</ref> The difficulty is that the establishing of a titer for tannin is not always convenient since it is extremely difficult to obtain the pure tannin. Neubauer proposed to remove this difficulty by establishing the titer not with regard to the tannin but with regard to crystallised [[oxalic acid]], whereby he found that 83&nbsp;g oxalic acid correspond to 41.20&nbsp;g tannin. Löwenthal's method has been criticized. For instance, the amount of indigo used is not sufficient to retard noticeably the oxidation of the non-tannins substances. The results obtained by this method are therefore only comparative.<ref>{{cite journal |last1=Spiers |first1=C. W. |title=The Estimation of Tannin in Cider |journal=The Journal of Agricultural Science |date=January 1914 |volume=6 |issue=1 |pages=77–83 |doi=10.1017/S0021859600002173|s2cid=85362459 |url=https://zenodo.org/record/2366998 }}</ref><ref>{{cite journal |last1=Snyder |first1=Harry |title=Notes on Löwenthal's method for the determination of tanin |journal=Journal of the American Chemical Society |date=October 1893 |volume=15 |issue=10 |pages=560–563 |doi=10.1021/ja02120a004|bibcode=1893JAChS..15..560S |url=https://zenodo.org/record/1428956 }}</ref> A modified method, proposed in 1903 for the quantification of tannins in wine, Feldmann's method, is making use of [[calcium hypochlorite]], instead of potassium permanganate, and indigo sulfate.<ref>{{cite journal |title=Nouvelle methode de dosage du tannin |journal=Schweizerische Wochenschrift für Chemie und Pharmacie |url=http://digisrv-1.biblio.etc.tu-bs.de/dfg-files/00041057/DWL/00000346.pdf |language=fr|archive-url=https://web.archive.org/web/20140808065055/http://digisrv-1.biblio.etc.tu-bs.de/dfg-files/00041057/DWL/00000346.pdf|archive-date=8 August 2014 }}</ref>

== Food items with tannins ==
=== Pomegranates ===
{{Main|Pomegranate ellagitannin}}

=== Accessory fruits ===
[[Strawberries]] contain both hydrolyzable and condensed tannins.<ref>{{cite journal|pmid=11309059|year=2001|last1=Puupponen-Pimiä|first1=R.|title=Antimicrobial properties of phenolic compounds from berries|journal=Journal of Applied Microbiology|volume=90|issue=4|pages=494–507|last2=Nohynek|first2=L|last3=Meier|first3=C|last4=Kähkönen|first4=M|last5=Heinonen|first5=M|last6=Hopia|first6=A|last7=Oksman-Caldentey|first7=KM|doi=10.1046/j.1365-2672.2001.01271.x |s2cid=6548208}}</ref>

=== Berries ===
[[File:Strawberries in white bowl.jpg|thumb|Strawberries in a bowl]]
Most berries, such as [[cranberry|cranberries]],<ref>{{cite journal |author1=Vattem D. A. |author2=Ghaedian R. |author3=Shetty K. |title=Enhancing health benefits of berries through phenolic antioxidant enrichment: focus on cranberry |journal=Asia Pac J Clin Nutr |volume=14 |issue=2 |pages=120–130 |year=2005 |pmid=15927928 |url=http://www.nupro.net/science/enhnce%20berry%20phenoli.pdf |url-status=dead |archive-url=https://web.archive.org/web/20101228115815/http://www.nupro.net/science/enhnce%20berry%20phenoli.pdf |archive-date=28 December 2010 |df=dmy-all }}</ref> and [[Blueberry|blueberries]],<ref>{{cite journal |author1=Puupponen-Pimiä R. |author2=Nohynek L. |author3=Meier C. |title=Antimicrobial properties of phenolic compounds from berries |journal=J. Appl. Microbiol. |volume=90 |issue=4 |pages=494–507 |date=April 2001 |pmid=11309059 |doi=10.1046/j.1365-2672.2001.01271.x |s2cid=6548208 |display-authors=etal}}</ref> contain both hydrolyzable and condensed tannins.

=== Nuts ===
[[Nut (fruit)|Nuts]] vary in the amount of tannins they contain. Some species of acorns of [[oak]] contain large amounts. For example, acorns of ''[[Quercus robur]]'' and ''[[Quercus petraea]]'' in [[Poland]] were found to contain 2.4–5.2% and 2.6–4.8% tannins as a proportion of dry matter,<ref>{{cite journal |last1=Łuczaj |first1=Łukasz |last2=Adamczak |first2=Artur |last3=Duda |first3=Magdalena |title=Tannin content in acorns (Quercus spp.) from Poland |journal=Dendrobiology |date=2014 |volume=72 |pages=103–111 |doi=10.12657/denbio.072.009 |url=http://www.idpan.poznan.pl/index.php/content/vol-72/1457-72-103-111 |access-date=15 September 2020|doi-access=free }}</ref> but the tannins can be removed by leaching in water so that the acorns become edible.<ref>{{cite book |last1=Howes |first1=F. N. |title=Nuts: Their production and everyday uses |date=1948 |publisher=Faber}}</ref> Other nuts – such as [[hazelnuts]], [[walnuts]], [[pecans]], and [[almonds]] – contain lower amounts. Tannin concentration in the crude extract of these nuts did not directly translate to the same relationships for the condensed fraction.<ref>{{cite conference|title=Assessment of the antioxidant and pro-oxidant activities of tree nut extracts with a pork model system|first1=R.|last1=Amarowicz|first2=R.B.|last2=Pegg|url=http://icomst-proceedings.helsinki.fi/papers/2008_02_31.pdf|date=2008|conference=International Congress of Meat Science and Technology|access-date=9 September 2019|archive-date=27 April 2021|archive-url=https://web.archive.org/web/20210427180157/http://icomst-proceedings.helsinki.fi/papers/2008_02_31.pdf|url-status=dead}}</ref>

=== Herbs and spices ===
[[Clove]]s, [[tarragon]], [[cumin]], [[thyme]], [[vanilla]], and [[cinnamon]] all contain tannins.{{citation needed|date=October 2015}}

=== Legumes ===
Most [[legume]]s contain tannins. Red-colored beans contain the most tannins, and white-colored beans have the least. [[Peanut]]s without shells have a very low tannin content. [[Chickpea]]s (garbanzo beans) have a smaller amount of tannins.<ref>{{cite journal|last=Reed|first= Jess D. |title=Nutritional toxicology of tannins and related polyphenols in forage legumes |journal=Journal of Animal Science |volume=73 |issue=5 |pages=1516–1528 |date=1 May 1995 |pmid=7665384 |doi=10.2527/1995.7351516x}}</ref>

=== Chocolate ===
[[Chocolate liquor]] contains about 6% tannins.<ref>{{cite book |author1=Robert L. Wolke |author2=Marlene Parrish |title=What Einstein told his cook 2: the sequel: further adventures in kitchen science |url=https://books.google.com/books?id=jGYMiTMhp9UC&pg=PA433 |date=29 March 2005 |publisher=W. W. Norton & Company |isbn=978-0-393-05869-7 |page=433 |url-status=live |archive-url=https://web.archive.org/web/20161216010635/https://books.google.com/books?id=jGYMiTMhp9UC&pg=PA433 |archive-date=16 December 2016 |df=dmy-all }}</ref>

=== Drinks with tannins ===
{{Main|Tannins in tea|Tannins in wine}}

Principal human dietary sources of tannins are tea and coffee.<ref>{{cite journal|journal=Planta Med|year=2004|volume=70|issue=12|pages=1103–1114|pmid=15643541|title=Diet-derived phenols in plasma and tissues and their implications for health|author=Clifford MN|doi=10.1055/s-2004-835835|doi-access=free|bibcode=2004PlMed..70.1103C }}</ref> Most wines aged in [[charred]] [[oak barrel]]s possess tannins absorbed from the wood.<ref>{{cite journal|journal=Crit Rev Food Sci Nutr|year=2014|volume=54|issue=6|pages=817–835|doi=10.1080/10408398.2011.609949|title=Advances in wine aging technologies for enhancing wine quality and accelerating wine aging process|vauthors=Tao Y, García JF, Sun DW|pmid=24345051|s2cid=42400092}}</ref> Soils high in clay also contribute to tannins in wine grapes.<ref name="Clarke pg 155-162">Oz Clarke ''Encyclopedia of Grapes'' pp. 155–162 Harcourt Books 2001 {{ISBN|978-0-15-100714-1}}</ref> This concentration gives wine its signature [[astringent|astringency]].<ref>{{cite journal|journal=Molecules|year=2011|volume=16|issue=3|pages=2348–2364|doi=10.3390/molecules16032348|pmid=21399572|pmc=6259628|title=Wine and grape tannin interactions with salivary proteins and their impact on astringency: a review of current research|vauthors=McRae JM, Kennedy JA|doi-access=free}}</ref>

Coffee pulp has been found to contain low to trace amounts of tannins.<ref>{{cite journal |author1=Clifford M. N. |author2=Ramirez-Martinez J. R. |title=Tannins in wet-processed coffee beans and coffee pulp |journal=Food Chemistry |volume=40 |issue=2 |pages=191–200 |year=1991 |doi=10.1016/0308-8146(91)90102-T }}</ref>

==== Fruit juices ====
Apple, grape and berry juices all contain high amounts of tannins. Sometimes tannins are even added to juices and ciders to create a more astringent feel to the taste.<ref>{{Cite web|url=http://www.cider.org.uk/tannin.htm|title=tannin2|website=www.cider.org.uk|access-date=2019-03-21}}</ref>

==== Beer ====
In addition to the [[alpha acid]]s extracted from [[hops]] to provide bitterness in [[beer]], condensed tannins are also present. These originate both from malt and hops. Trained brewmasters, particularly those in Germany, consider the presence of tannins to be a flaw{{citation needed|reason=Are there some sources to show that German brewmasters will remove tannins?  Popular brands in contrast to the statement that follows?|date=July 2020}}. However, in some styles, the presence of this astringency is acceptable or even desired, as, for example, in a [[Flanders red ale]].<ref>{{Cite journal|last1=Deshpande|first1=Sudhir S.|last2=Cheryan|first2=Munir|last3=Salunkhe|first3=D. K.|last4=Luh|first4=Bor S.|date=1986-01-01|title=Tannin analysis of food products|url=https://doi.org/10.1080/10408398609527441|journal=C R C Critical Reviews in Food Science and Nutrition|volume=24|issue=4|pages=401–449|doi=10.1080/10408398609527441|issn=0099-0248|pmid=3536314}}</ref>

In lager type beers, the tannins can form a precipitate with specific haze-forming proteins in the beer resulting in [[turbidity]] at low temperature. This chill haze can be prevented by removing part of the tannins or part of the haze-forming proteins. Tannins are removed using [[Polyvinylpolypyrrolidone|PVPP]], haze-forming proteins by using [[silica]] or tannic acid.<ref>{{cite web |url=http://www.natural-specialities.com/natural-specialities/PDF/Applications/BR02%20overview%20fact%20sheet%20version%202.1.pdf |title=Brewtan range – Natural solutions for beer stabilisation – Application fact-sheet |website=natural-specialities.com |publisher=Ajinomoto OmniChem|access-date=10 March 2010 |url-status=dead |archive-url=https://web.archive.org/web/20110714155948/http://www.natural-specialities.com/natural-specialities/PDF/Applications/BR02%20overview%20fact%20sheet%20version%202.1.pdf |archive-date=14 July 2011 |df=dmy-all }}</ref>

== Properties for animal nutrition ==
Tannins have traditionally been considered [[Antinutrient|antinutritional]], depending upon their chemical structure and dosage.<ref>{{cite journal |author1=Muller-Harvey I. |author2=McAllan A. B. |title=Tannins: Their biochemistry and nutritional properties |journal=Advances in Plant Cell Biochemistry and Biotechnology |volume=1 |pages=151–217 |year=1992}}</ref>

Many studies suggest that chestnut tannins have positive effects on [[silage]] quality in the [[Baler#Silage or haylage bales|round bale silages]], in particular reducing [[Non-protein nitrogen|NPN]]s (non-protein nitrogen) in the lowest wilting level.<ref>{{cite journal |author1=Tabacco E. |author2=Borreani G. |author3=Crovetto G. M. |author4=Galassi G. |author5=Colombo D. |author6=Cavallarin L. |title=Effect of chestnut tannin on fermentation quality, proteolysis, and protein rumen degradability of alfalfa silage |journal=Journal of Dairy Science |volume=89 |issue=12 |pages=4736–4746 |date=1 December 2006 |pmid=17106105 |doi=10.3168/jds.S0022-0302(06)72523-1 |doi-access=free |df=dmy-all }}</ref>

Improved fermentability of [[Soybean|soya meal]] nitrogen in the [[rumen]] may occur.<ref>{{cite journal |doi=10.1051/animres:19930210 |author1=Mathieu F. |author2=Jouany J. P. |title=Effect of chestnut tannin on the fermentability of soyabean meal nitrogen in the rumen |journal=Ann Zootech |volume=42 |page=127 |year=1993 |issue=2 |doi-access=free }}</ref> Condensed tannins inhibit herbivore digestion by binding to consumed plant proteins and making them more difficult for animals to digest, and by interfering with protein absorption and digestive enzymes (for more on that topic, see [[plant defense against herbivory]]). [[Histatin]]s, another type of [[salivary protein]]s, also precipitate tannins from solution, thus preventing alimentary adsorption.<ref>{{cite journal | last=Shimada | first=Takuya | title=Salivary Proteins as a Defense Against Dietary Tannins | journal=[[Journal of Chemical Ecology]] | volume=32 | issue=6 | date=23 May 2006 | pmid=16770710 | doi=10.1007/s10886-006-9077-0 | pages=1149–1163| bibcode=2006JCEco..32.1149S | s2cid=21617545 }}</ref>

[[Legume]] fodders containing condensed tannins are a possible option for integrated sustainable control of gastrointestinal [[nematode]]s in ruminants, which may help address the worldwide development of resistance to synthetic [[anthelmintics]]. These include nuts, temperate and tropical barks, carob, coffee and cocoa.<ref name="Hoste2022">{{cite journal | last1=Hoste | first1=Hervé | last2=Meza-OCampos | first2=Griselda | last3=Marchand | first3=Sarah | last4=Sotiraki | first4=Smaragda | last5=Sarasti | first5=Katerina | last6=Blomstrand | first6=Berit M. | last7=Williams | first7=Andrew R. | last8=Thamsborg | first8=Stig M. | last9=Athanasiadou | first9=Spiridoula | last10=Enemark | first10=Heidi L. | last11=Torres Acosta | first11=Juan Felipe | last12=Mancilla-Montelongo | first12=Gabriella | last13=Castro | first13=Carlos Sandoval | last14=Costa-Junior | first14=Livio M. | last15=Louvandini | first15=Helder | last16=Sousa | first16=Dauana Mesquita | last17=Salminen | first17=Juha-Pekka | last18=Karonen | first18=Maarit | last19=Engstrom | first19=Marika | last20=Charlier | first20=Johannes | last21=Niderkorn | first21=Vincent | last22=Morgan | first22=Eric R. | title=Use of agro-industrial by-products containing tannins for the integrated control of gastrointestinal nematodes in ruminants | journal=Parasite | volume=29 | year=2022 | doi=10.1051/parasite/2022010 | page=10| pmid=35225785 | pmc=8884022 }} {{open access}}</ref>

== Tannin uses and market ==
[[File:Tannin in Plastic container.jpeg|thumb|Tannin in a plastic container]]
Tannins have been used since antiquity in the processes of tanning hides for leather, and in helping preserve iron artifacts (as with Japanese iron teapots).

Industrial tannin production began at the beginning of the 19th century with the industrial revolution, to produce tanning material for the need for more leather. Before that time, processes used plant material and were long (up to six months).<ref>{{cite web |title=1854 – 1906: The foundation |url=https://www.silvateam.com/en/who-we-are/history/1854-1906-foundation.html |website=Silvateam |access-date=9 August 2022 |language=en |date=15 May 2015}}</ref>

There was a collapse in the vegetable tannin market in the 1950s–1960s, due to the appearance of [[synthetic tannin]]s, which were invented in response to a scarcity of vegetable tannins during World War II. At that time, many small tannin industry sites closed.<ref>{{Cite web|url=https://www.iufro.org/download/file/2480/95/10700-mangrove-ecosystems.doc|title="The Status of Mangrove Ecosystems: Trends in the Utilisation and Management of Mangrove Resources". D. Macintosh and S. Zisman}}</ref> Vegetable tannins are estimated to be used for the production of 10–20% of the global leather production.{{citation needed|date=October 2017}}

The cost of the final product depends on the method used to extract the tannins, in particular the use of solvents, alkali and other chemicals used (for instance [[Glycerite|glycerin]]). For large quantities, the most cost-effective method is hot water extraction.

[[Tannic acid]] is used worldwide as clarifying agent in alcoholic drinks and as aroma ingredient in both alcoholic and soft drinks or juices. Tannins from different botanical origins also find extensive uses in the wine industry.{{citation needed|date=October 2017}}

=== Uses ===
Tannins are an important ingredient in the process of tanning leather. [[Tanbark]] from [[oak]], [[mimosa]], chestnut and [[quebracho tree]] has traditionally been the primary source of [[Tanning (leather)|tannery]] tannin, though inorganic [[Leather tanning|tanning agents]] are also in use today and account for 90% of the world's leather production.<ref>{{cite book |author1=Marion Kite |author2=Roy Thomson |title=Conservation of leather and related materials |url=https://books.google.com/books?id=62zZy2B4ehQC |year=2006 |publisher=Butterworth-Heinemann |isbn=978-0-7506-4881-3 |page=23 |url-status=live |archive-url=https://web.archive.org/web/20161216170048/https://books.google.com/books?id=62zZy2B4ehQC |archive-date=16 December 2016 |df=dmy-all }}</ref>

Tannins produce different colors with [[ferric chloride]] (either blue, blue black, or green to greenish-black) according to the type of tannin. [[Iron gall ink]] is produced by treating a solution of tannins with [[iron(II) sulfate]].<ref>{{cite web|last1=Lemay|first1=Marie-France|title=Iron Gall Ink|url=https://travelingscriptorium.library.yale.edu/2013/03/21/iron-gall-ink/|website=Traveling Scriptorium: A Teaching Kit|publisher=Yale University|access-date=18 January 2017|url-status=live|archive-url=https://web.archive.org/web/20170215082127/https://travelingscriptorium.library.yale.edu/2013/03/21/iron-gall-ink/|archive-date=15 February 2017|df=dmy-all|date=21 March 2013}}</ref>

Tannins can also be used as a [[mordant]], and is especially useful in [[natural dye]]ing of [[cellulose fiber]]s such as cotton.<ref>{{Cite journal|last1=Prabhu|first1=K. H.|last2=Teli|first2=M. D.|date=2014-12-01|title=Eco-dyeing using Tamarindus indica L. seed coat tannin as a natural mordant for textiles with antibacterial activity|journal=Journal of Saudi Chemical Society|language=en|volume=18|issue=6|pages=864–872|doi=10.1016/j.jscs.2011.10.014|issn=1319-6103|doi-access=free}}</ref> The type of tannin used may or may not have an impact on the final color of the fiber.

Tannin is a component in a type of industrial [[particleboard]] [[adhesive]] developed jointly by the Tanzania Industrial Research and Development Organization and Forintek Labs Canada.<ref>{{cite journal |doi=10.1016/S0958-9465(02)00072-0 |author1=Bisanda E. T. N. |author2=Ogola W. O. |author3=Tesha J. V. |title=Characterisation of tannin resin blends for particle board applications |journal=Cement and Concrete Composites |volume=25 |issue=6 |pages=593–598 |date=August 2003 }}</ref> ''[[Pinus radiata]]'' tannins has been investigated for the production of [[Wood glue|wood adhesives]].<ref>{{cite journal |last1=Li |first1=Jingge |last2=Maplesden|first2=Frances |title=Commercial production of tannins from radiata pine bark for wood adhesives |journal=IPENZ Transactions |volume=25 |issue=1/EMCh |year=1998 |url=http://www.ipenz.org.nz/ipenz/publications/transactions/Transactions98/emch/7li.PDF |archive-url=https://web.archive.org/web/20030122050049/http://www.ipenz.org.nz/ipenz/publications/transactions/Transactions98/emch/7li.PDF |url-status=dead |archive-date=22 January 2003 |df=dmy-all }}</ref>

[[Condensed tannin]]s, e.g., quebracho tannin, and [[Hydrolyzable tannin]]s, e.g., chestnut tannin, appear to be able to substitute a high proportion of synthetic phenol in phenol-formaldehyde resins for wood [[particleboard]].{{citation needed|date=October 2017}}

Tannins can be used for production of anti-[[corrosion|corrosive]] primers for treating rusted steel surfaces prior to painting, converting rust to iron tannate and consolidating and sealing the surface.

The use of [[resin]]s made of tannins has been investigated to remove [[Mercury (element)|mercury]] and [[methylmercury]] from solution.<ref>{{cite journal |author1=Torres J. |author2=Olivares S. |author3=De La Rosa D. |author4=Lima L. |author5=Martínez F. |author6=Munita C. S. |author7=Favaro D. I. T. |title=Removal of mercury(II) and methylmercury from solution by tannin adsorbents |journal=Journal of Radioanalytical and Nuclear Chemistry |volume=240 |issue=1 |pages=361–365 |year=1999 |doi=10.1007/BF02349180 |bibcode=1999JRNC..240..361T |s2cid=24811963 }}</ref> Immobilized tannins have been tested to recover [[uranium]] from seawater.<ref>{{cite journal |author1=Takashi Sakaguchia |author2=Akira Nakajimaa |title=Recovery of Uranium from Seawater by Immobilized Tannin |journal=Separation Science and Technology |volume=22 |issue=6 |pages=1609–1623 |date=June 1987 |doi=10.1080/01496398708058421 }}</ref>

== References ==
{{Reflist|30em}}

== External links ==
{{NSRW Poster}}
{{commons cat}}
* [http://www.ansci.cornell.edu/plants/toxicagents/tannin.html Tannins: fascinating but sometimes dangerous molecules]
* {{cite web|url= http://www.users.muohio.edu/hagermae/tannin.pdf |title=Tannin Chemistry }}&nbsp;{{small|(1.41&nbsp;MB)}}
* {{cite book |last=Haslam |first=Edwin |title=Plant polyphenols: vegetable tannins revisited |url=https://books.google.com/books?id=Zyc9AAAAIAAJ |year=1989 |publisher=CUP Archive |isbn=978-0-521-32189-1}}

{{Tannin}}
{{Wood products}}

{{Authority control}}

[[Category:Tannins| ]]
[[Category:Nutrition]]
[[Category:Oenology]]
[[Category:Organic polymers]]
[[Category:Wine terminology]]
[[Category:Astringent flavors]]
[[Category:Phenol antioxidants]]
[[Category:Wood products]]
[[Category:Food stabilizers]]
[[Category:Phytochemicals]]
[[Category:Wood extracts]]