Tannins
Tannins are responsible for the astringency we experience because they bind to the proteins located on our tongue. They are also responsible for the mouthfeel associated with high-quality red wines therefore, the understanding of what a tannin is, is important if making quality red wines is the goal.
Tannins are part of a class of molecules that contain a phenolic group, so they may also be referred to as a polyphenolic or also as a flavonoid, specifically a member of the flavan-3-ol class of molecules, due to their chemical composition. The flavan-3-ol molecules found in grapes include (+)-catechin, (-)-epicatechin,
(-)-epigallocatechin and (-)-epicatechin gallate. From a winemaker’s point of view, there are two types of tannin relevant to winemaking:
- Condensed
- Hydrolysable
Hydrolysable tannins are wood-derived and historically found only in barrel-aged wines. Hydrolyzed tannins will be less likely to stabilize color but may promote fuller mid-palate and a softer mouthfeel due to lower, slower protein interaction.
Condensed Tannins | Hydrolyzable Tannins |
Derived from mainly from grape skin and some from grape seeds | Derived from wood and histroically found only in barrel-aged wines |
Subunits include (+)-catechin, (-)-epi-catechin, (-)-epigallocatechin and (-)-epicatechin gallate |
Major subunits include gallic and elagic acids |
Binds with protein at a ratio of 20:1 | Binds with protein at a ratio of 40:1 |
Aids in color stabilization by binding with anthocyanins | Less likely to stabilize color |
Higher proportion of skin-derived tannins has been found to enhance perception of red wine quality | May promote fuller mid-palate and a softer mouthfeel due to lower, slower protein interaction |
References:
1. Anna Katherine Mansfield, A Few Truths About Phenolics, Wines & Vines, January 2015.
2. Douglas Adams, VI257, Lesson 8, pg. 50.
3. Jackson, Ronald S., Wine Science: Principles and Applications, Third Edition, Elsevier, Academic Press, 2008.
4. Matthew R. Revelette, Ralph S. Yacco and James A. Kennedy, STICKINESS New concept in grape and wine tannin analysis, Practical Winery & Vineyard, January 2015, pg. 32-37.
All structures were drawn by the freely available drawing program from ACD Labs called ACD/ChemSketch Freeware.
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