To get technical about it, tannins are bitter tasting plant polyphenols that bind and precipitate proteins. Tannins are found in red wines in particular and may come from a variety of sources. Tannins may be located in the skins and seeds, with seed tannins being very harsh. Because the skin and seeds are fermented with the juice, the tannins are very noticeable in red wines.
Winemakers do their best to minimize the undesirable tannins from the seeds by crushing the grapes gently. Pressing the grapes results in “press wine” which is more tannic and may be used to blend with the “first wine” to adjust the flavor and levels of tannins. If wines are aged in oak or wood casks that have a high tannin content, the wine may take on some of those tannins. Tannins also play an important part in keeping the wine from oxidizing as it ages and appear to make up a large portion of the sediment in the wine.
Tannins are what give the wine its character and can also be what causes the “dry” feeling of the mouth. The tannins actually modifies the saliva in the mouth by removing saliva’s lubrication. This is actually very unique and interesting. The tannin actually combines with the protein molecules in the saliva, which destroys the lubricating ability in the saliva.
As wine ages, the degree of polymerization in tannins increase for the first years of the aging process. Wines are more tannic at this stage of the process. Once the tannin molecules reach a high degree of polymerization they begin to lose their capability to combine with proteins. So the astringency that is often associated with the tannins are decreased. The favorable characteristic of the tannin may be maintained. As the wine is allowed to breathe, the tannins will begin to soften in the wine. The “maturity plateau” is the level at which the wines is ideal to drink.
We actually experience tannins in a variety of things that we eat. Tannins are what make us pucker after eating fruit that is not ripe. That astringent feeling that you get when you eat a pomegranate, persimmon or a green banana. According to the renowned wine critic, tannins can give a variety of qualities to a red wine. But, not only can tannins make a red wine good, but they can also make a red wine bad. There have been several red wines that have an overabundance of the “wrong” tannins. These wines have been called “green” or “aggressive.”
Vintners routinely test the tannin levels in their grapes. The unwanted tannins are located in the seed, but the seed is an excellent way to tell if the grape is ripe. An unripe grape will have a green seed while a ripened grape will have a brown seed. They are looking to control the amount, quality and types of tannins that end up in their wine. To avoid these “bad” tannins, they are changing the way that the grapes are pressed so that the seed tannins are not extracted. There are good tannins that can make a bottle of wine worth twice as much as another bottle, even if the grapes were grown only a short distance from the other. The tannin levels may depend on climate elements that the vineyard cannot control, such as drier soil in one area and more sun in another. Vineyards can work with scientists to research each vine area to determine what is making one vine’s area more desirable for tannins than another and then trying to work to replicate those same conditions across the vineyard.
New techniques are constantly being developed to make the tannins more desirable in wine. At one point in time, California was producing Cabernet Sauvignons that were very aggressive. The winemakers were working to develop lines that would last longer, but at the same time the wine was harsh if not aged. This can be difficult in our society because we want good wine and we want it now. This means that winemakers are having to learn how to alter the levels of desirable tannins so that their wines can be released to the public earlier. The winemakers are changing how they grow, harvest and produce their wines so that they have the ultimate tannin structure.
Most vineyards have found that people don’t want to have to wait for their wines to age after they have bought them. They want the wines to be drinkable when they bring them home. Winemakers have found that good tannins create volume in a wine when it is in your mouth. They should not make you pucker or give you a dry mouth. They have also found that if their vines are allowed to have more sunlight, they are more likely to have softer tannins.