Talk:Tannin

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Assessment comments The following comments were left by the assessors: (edit · refresh) I came to this page in order to find information regarding interactions between tannins and polysaccharides and i find that, rather startlingly, it is considered to be an article about wine. This is a very narrow view and doesn't cover areas such as leather production, dyeing and the preparation of ink. I have a little knowledge in these areas, but not enough, and there is also very little chemistry in this article. To consider tannins primarily in terms of tea and wine is very limited. I am interested in making some changes, but i'm not a chemist, a textile technologist or a historian, so i'm not going to be able to add much useful information. I just wanted to comment on that in case anyone else knows more or has more expertise and reads this. It needs at least the following: Information on specific interactions between tannins and other compounds. A list of uses. Links to entries regarding leather, ink and dyes. Comments on their use in traditional medicine systems. Health risks and benefits of a diet high in tannins.
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Contents 1 Tea? 2 Tea revisited... 3 Sediment 4 Article name 5 Weight of tannins 6 Cranberry 7 Just a thought 8 Just another thought 9 Scope of subject 10 Is this true? 11 Need article about Shibuol

[edit] Tea?

A local tea manufacturer (Douwe Egberts) claims on their web sites that tea does NOT contain tannin (looizuur), but related chemicals, flavonoids (lit. from Dutch), which are polyfenols (again, lit. from Dutch). See http://www.pickwick.nl/faq/faq_rechts.asp?VraagID=16 (Dutch).

• Tannin is a polyphenol, if that helps.

Can anyone confirm or deny this? branko

"Tannin" is very broad term, as I understand it. It's used to refer to a whole stack of related organic chemicals, and rather poorly defined. Many of them appear in bark rather than in leaves. I looked this stuff up a while ago, and have forgotten the details, alas. I guess I have a pretty good reason to refresh my memory and update the entry accordingly. :) Tannin

I *thought* it should read tannins (plural) too, but wasn't completely sure so I decided not to rock the boat. You'll notice that under tea, I did use only the plural. Mkweise 07:39 Jan 28, 2003 (UTC)

It is possible that the Japanese cultivars of sencha green tea plants contain significantly more/less tannin than cultivars of green tea plants grown in China. But it's commonly known that even a cup of sencha tea can taste undesirably tart if it is steeped in water hotter than 160°F longer than 2 minutes. That is why mainland Japanse are very careful about their tea brewing. So isn't that proof that an oversteeped infusion of green tea leaves contains tannins? Well, that is only evidence; not positive proof. Remember that oversteeped tea contains excessive amounts of oxalic acid, which is another tart component. As of this writing no published literature has been found that reports a reasonably complete chemical assay of a standardized green tea infusion. However, here are a few publications that mention green tea's content of tannin. The articles imply a description of the beverage, not the leaf.

http://www.pdrhealth.com/drug_info/nmdrugprofiles/herbaldrugs/101320.shtml http://www.o-cha.com/green-tea-benefits.htm http://www.myfineequine.com/greenteamfe.htm Zymatik

With regards to tea's sedative effect, that is not attributed to tannins, but instead to an amino acid alkaloid named theanine.

http://www.itmonline.org/arts/theanine.htm http://www.green-tea-benefit.com/health_benefits.html#difference http://www.o-cha.com/green-tea-benefits.htm http://www.greenteacomplex.com/benefits.html http://www.raysahelian.com/theanine.html Zymatik

Reference showing that green tea contains tannic acid 'Start the Day Right' by Dr. Sarah Brewer, Nov 2004 http://www.healthspan.co.uk/articles/article.aspx?Id=128 Zymatik

Reference showing that tea contains phenolic acid groups including gallic acid (type of tannin) 'The Chemistry of Tea' by Chung S. Yang, Zhi-Yuan Wang http://www.teatalk.com/science/chemistry.htm Zymatik

This article states The term "tannins" has been used by many to describe certain tea constituents. In industrial and botanic literatures, tannins are characterized as plant materials that give a blue color with ferric salts and produce leather from hides. Thus, tannins are a group of chemicals usually with large molecular weights and diverse structures. Monomeric flavanols, the major components in green tea, are precursors of condensed tannins. It would be more appropriate to use the term "tea polyphenols" or "tea flavanols" because they are quite distinct from commercial tannins and tannic acid., so this article should be convincing evidence that the term "tannin" is considered incorrect. MatthewEHarbowy 22:43, 3 January 2007 (UTC) Also, gallic acid cannot be a tannin based upon the definition as a molecular weight between 500 and 20000, since it has a molecular weight of 170- see gallic acid MatthewEHarbowy 04:55, 4 January 2007 (UTC)

Green tea contains catechin-based flavonoids, including catechin and epicatechin, and their gallic acid esters. These and other flavonoids make up approximately 30% of the weight of dried tea leaves. Epigallocatechin gallate is the flavonoid in the highest proportion in green tea. Black tea contains more free gallic acid, which is a strong antioxidant; however, the gallic acid esters of catechins, which are found in greater quantity in green tea, are more potent free radical scavengers. Ho CT, Chen Q, Shi H, et al. Antioxidative effect of polyphenol extract prepared from various Chinese teas. Prev Med 1992;21:520-525. Zymatik

Reference showing that prodelphinidin is in green tea leaves Cheng HY, Lin CC, Lin TC. Antiviral properties of prodelphinidin B-2 3'-O-gallate from green tea leaf. Antivir Chem Chemother. 2002 Jul;13(4):223-9. Zymatik

if you look at the article, it says the method of isolation from tea is to extract the leaves with acetone. There are a few trace proanthocyanidins in tea, but they are not easily extracted into aqueous soulution and not in significant quantity, so the research cited is not relevant to tea as a food source, unless the person is using nail-polish remover to brew their tea. MatthewEHarbowy 07:49, 4 January 2007 (UTC)

Reference showing that prodelphinidin is present in green tea leaves and that prodelphinidin is a proanthocyanidin type of flavanol (which therefore fits the description of tannin) http://www.acu-cell.com/bio.html Zymatik

EGCG can bined protein and therefor is a tannin. Therefor tea has tannins. Jasoninkid 23:21, 31 May 2007 (UTC)

[edit] Tea revisited...

Wikipedian MatthewEHarbowy removed the entire tea reference with the edit summary of tea does not contain tannins- it contains polyphenols. I thought this was previously settled (see discussion above). In short, Tannins are plant polyphenols. The article states this, and numerous (almost all) references on the web support this. Further, the same references make no distinction between the polyphenols in tea and tannins; they all refer to the polyphenols in tea as tannins. I suggest we leave the tea reference in the article unless someone can provide an authorative explanation for why the polyphenols in tea are not really tannins. Gregmg 21:54, 15 December 2006 (UTC)

I have worked directly in this field (Balentine DA, Harbowy ME and Graham HN, Tea: the Plant and its Manufacture; Chemistry and Consumption of the Beverage in Caffeine (1998), ed. G Spiller and others) and while the term tannin is a term used to describe the taste of tea, there are only trace quantities of true "tannins" such as procyanidins and hydrolysable tannins such as esters of gallic acid. Tea does contain gallic acid, but it is not typically considered a tannin (and does not precipitate protein- see here) even though many tannins contain esterified gallic acid. I have re-edited to be more conservative in my statement this time, however, the statement "tea does not contain tannins" has been published many times, in both peer reviewed articles and books published like the one I cite above. MatthewEHarbowy 22:38, 3 January 2007 (UTC)

More info, from here: Tannins are phenolic compounds that precipitate proteins. They are composed of a very diverse group of oligomers and polymers. There is some confusion about the terminology used to identify or classify a substance as a tannin, In fact, not only tannins bind and precipitate proteins (other phenolics such as pyrogallol and resorcinol also have this property), not all polyphenols precipitate proteins or complex with polysaccharides.

One of the most satisfactory definition of tannins was given by Horvath: "Any phenolic compound of sufficiently high molecular weight containing sufficient hydroxyls and other suitable groups (i.e. carboxyls) to form effectively strong complexes with protein and other macromolecules under the particular environmental conditions being studied".

Simple phenolics, such as gallic acid, pyrogallol, catechin, and catechol, even though sometimes they are able to precipitate protein (depends on the concentration and the protein), are not polymers and are not commercially useful as tanning agents the way tannic acid is used.

Even the article on tannic acid as well as many websites (including one used to justify the argument that tea contains tannins, see this for example) state that tea does not contain tannic acid/does not tan leather. Articles such as this one say "tannic acid", not tannin, even though one could make the argument that tea does contain trace amounts of novel tannins (see Crit. Rev. Plant Sci 16 (5) 433-434 (1997)) and therefore "tannin" is margianlly an ok word to use. When an article uses the word "tannic acid" with tea it's usually a sign that the author doesn't understand the chemistry and is repeating some hearsay that they had heard, which would make it unsuitable for inclusion in Wikipedia. Tannin is a broad word which could mean any polyphenolic- if the two aren't different, then the definition is not useful and tannin should just redirect to polyphenol. If the two are slightly different, then a source better than the ones at my disposal needs to be cited.

Tannic redirects here, and tannic is meant to mean tasting like tannin or tannic acid, that is, astringent. It is a useful term in wine, because oak wood is used to ferment the wine and tannin from the wood can leach into the wine giving a tannic character, in addition to tannins coming from the skins or the seeds of the grapes. It's a term to describe organoleptic properties, not chemistry, and that distinction should be made. This is missing from this article, and as soon as I can figure out how to word that nicely, I'll add it. MatthewEHarbowy 03:09, 4 January 2007 (UTC)

By your deffinishion tannins do not need to be polymers, EGCG is quit capable of precipitating protein and is in abundance in tea. Additionally form the Hagerman lab's tannin hand book"For example, consumption of large quantities of tea or other tannin-rich foods..." Jasoninkid 23:56, 31 May 2007 (UTC)

[edit] Sediment

Is the sediment bit right? I thought the sediment was mostly salts of tartaric acid, as investigated by Louis Pasteur

Pretty sure about it. Having trouble finding a good cite of an overview of wine chemistry, but basically the anthocyanins (pigment molecules) and tannins polymerize very slowly and gradually get so big they fall out of solution, leaving a less red and less tannic wine. [1] talks about the process during fermentation, but doesn't really discuss aging. Tartaric acid is what makes sediment gritty, and is also a major contributor. Wnissen 19:30 6 Jun 2003 (UTC)

[edit] Article name

If no one objects, I would like to move this page to Tannin, since most of the incoming pages link to there. — Pekinensis 14:58, 12 May 2005 (UTC)

Done. — Pekinensis 14:40, 15 May 2005 (UTC)

[edit] Weight of tannins

I would direct your attention to the first paragraph where the molecular weight of tannins is provided. Doesn't there seem like there is something a little fishy about those numbers? :P Flying Hamster 17:17, 9 November 2006 (UTC)

I'm not a chemist nor do I play one on TV, however, the 500 to 20,000 molecular weight range comes from the Cornell link in the External links section. If this is in error, we should correct the article, add a correct link to replace the Cornell University link, and notify the University their page is in error. Gregmg 21:30, 9 November 2006 (UTC)

No this is right EGCG is ~490Da and other tannins can be quit large. Jasoninkid 23:25, 31 May 2007 (UTC)

[edit] Cranberry

The article mostly claims the "cranberry tannins" are responsible for reducing bacteriuria, pyuria, and cavities. Yet, here, it calls the material for dental health a 'non-dialyzable material (NDM)' and here it refers to phenolics and flavonoids, which are not necessarily tannins. Furthermore, the studies cited tested cranberry juice, which may contain other components that cause the effect. Scientific articles should identify the molecular agent responsible and give its chemical identity as a tannin, otherwise this is speculation. —The preceding unsigned comment was added by MatthewEHarbowy (talk • contribs) 04:51, 4 January 2007 (UTC).

[edit] Just a thought

The article seems to have a bias towards producers in certain areas, and seems to give its information about wine-pressing in a biased way.—Preceding unsigned comment added by 65.95.130.211 (talk) 13:07, 27th February 2007 (UTC)

This article completely failsto mention the biological relevence of tannins - namely that of plant defence against herbivores. A new section should be created with links to other plant defences such as protease inhibitors.—Preceding unsigned comment added by 129.234.4.76 (talk) 17:51, 5th May 2007 (UTC)

[edit] Just another thought

Hey you above me, if your so smart why don' tyou post it lol..that is the way of the Wiki :) —Preceding unsigned comment added by 71.181.32.97 (talk) 14:56, 26 December 2007 (UTC)

[edit] Scope of subject

I came to this page in order to find information regarding interactions between tannins and polysaccharides and i find that, rather startlingly, it is considered to be an article about wine. This is a very narrow view and doesn't cover areas such as leather production, dyeing and the preparation of ink. I have a little knowledge in these areas, but not enough, and there is also very little chemistry in this article. To consider tannins primarily in terms of tea and wine is very limited. I am interested in making some changes, but i'm not a chemist, a textile technologist or a historian, so i'm not going to be able to add much useful information. I just wanted to comment on that in case anyone else knows more or has more expertise and reads this. —Preceding unsigned comment added by Nineteenthly (talk • contribs) 10:42, 7 March 2008 (UTC)

[edit] Is this true?

Are cranberries legumes? The article says nothing about that.

Lunakeet 13:18, 18 May 2008 (UTC)

Cranberries are not legumes. DuncanHill (talk) 14:31, 18 May 2008 (UTC)

The statement implying that cranberries are legumes was introduce in this edit [2], the only edit ever made by the account which made it. I am going to remove the offending sentence. DuncanHill (talk) 14:44, 18 May 2008 (UTC)

[edit] Need article about Shibuol

Need article about the tannin Shibuol. Badagnani (talk) 08:20, 24 May 2008 (UTC)