To get technical about it, tannins are bitter-tasting plant polyphenols that bind and precipitate proteins. Tannins are primarily found in red wines, and they can come from various sources. Tannins are located in the skins and seeds of grapes, with seed tannins being particularly harsh. Since the skin and seeds are fermented with the juice, tannins are more noticeable in red wines.
Winemakers strive to minimize the undesirable tannins from the seeds by crushing the grapes gently. Pressing the grapes results in “press wine,” which is more tannic. This press wine may be blended with the “first wine” to adjust the flavor and tannin levels. If wines are aged in oak or wood casks with high tannin content, they may absorb some of those tannins. Tannins also play an important role in preventing oxidation as the wine ages and contribute significantly to the sediment in the wine.
The Role of Tannins in Wine’s Texture and Aging
Tannins give the wine its character and contribute to the “dry” feeling in the mouth. They modify the saliva in your mouth by removing its lubricating properties. This interaction is actually quite unique and interesting. Tannins combine with the protein molecules in saliva, which reduces its lubricating ability.
As wine ages, the degree of polymerization in tannins increases during the first few years of the aging process. During this stage, wines are more tannic. Once the tannin molecules reach a high degree of polymerization, they begin to lose their ability to bind with proteins. As a result, the astringency often associated with tannins decreases, but the favorable characteristics may remain. As the wine breathes, the tannins soften, and the wine reaches its “maturity plateau”—the ideal point for drinking.
We experience tannins in many foods we eat. Tannins are what cause that pucker-inducing sensation when eating unripe fruit, such as pomegranates, persimmons, or green bananas. Renowned wine critic opinions vary on tannins, as they can provide a wide range of qualities to red wine. However, tannins can also have negative effects. Some red wines have an overabundance of “bad” tannins, which are described as “green” or “aggressive.”
Vintners routinely test the tannin levels in their grapes. The unwanted tannins are found in the seeds, but the seed also provides a good indicator of grape ripeness. An unripe grape will have a green seed, while a ripe grape will have a brown seed. Winemakers aim to control the amount, quality, and types of tannins that end up in their wine. To avoid “bad” tannins, they adjust their methods of pressing grapes to minimize seed tannin extraction. Good tannins can significantly increase the value of a bottle of wine, even if the grapes are grown only a short distance apart. Tannin levels can also depend on uncontrollable factors like the dryness of the soil or the amount of sunlight in certain vineyard areas. Scientists work with vineyards to determine what conditions make one vine’s location more desirable for tannins, and then attempt to replicate those conditions across the vineyard.
New techniques are continually being developed to create more desirable tannins in wine. For example, California was once known for producing aggressive Cabernet Sauvignons. While winemakers were trying to develop wines that would last longer, these wines were harsh if not aged. In today’s market, however, there is a strong demand for wines that are ready to drink immediately. As a result, winemakers have had to adapt by altering the levels of desirable tannins, so that their wines can be released to the public sooner. They are adjusting their growing, harvesting, and production processes to achieve the perfect tannin structure.
Most vineyards have discovered that consumers don’t want to wait for their wine to age after purchasing it. They want it to be drinkable right away. Winemakers have found that good tannins create a sense of volume in the wine when it’s in your mouth. Ideally, tannins shouldn’t make you pucker or leave your mouth feeling dry. They’ve also found that allowing the vines more sunlight tends to produce softer tannins, which is highly desirable.
