Tannins are organic compounds contained in grape skins, seeds and stems, grain husks, the bracts and strigs of hop cones, apple skins and seeds, and oak. Commonly referred to as astringency or polyphenols, tannins are perceived as the mouth puckering dryness associated with biting into a grape seed, banana peel, or tea leaf. By itself, tannin is not a pleasant substance to taste, but in wines, meads, and ciders it balances the sweetness from sugars and glycerine in the honey and fruit. They are present in all beers, wine, mead and cider. Tannins have the unique ability to combine with and precipitate out proteins.
Tannin in Wine
Red wines contain an average of about .2% tannin whereas the corresponding figure for white wines is normally less than .05%. Only a few fruits, notably elderberries, pears, and apples are as rich in this commodity as the grape. Tannin is an extremely important minor constituent of every wine. It assists clarification by combining with and precipitating proteins and other nitrogenous substances which tend to promote and/or stabilize hazes. This is why red wines which are rich in tannin tend to fall bright and clear more rapidly than white wines. Despite that fact that little is present in any wine, tannin has such a bitter flavor that even these little amounts are quite sufficient to impart a degree of astringency. Indeed, a balanced tannin content is a prerequisite of a good quality wine. Too little will result in an insipid wine which lacks depth and character while too much will cause a rough harsh flavor.
The high tannin content of red wines improves their keeping qualities, but at the same time increases the period of maturation needed before the wine reaches its best. Tannins in young wines are harsher to the taste because they are small molecules that the tongue can easily discern. As the wine ages, these tannins bind with other molecules in the wine and become larger in size. Some become so large that they will fall out of suspension like an old port. Many, however, remain in suspension. They are smoother tasting because they have bonded with other molecules and the tongue is no longer able to discern them separately. Wine writer terms 'round', 'supple', 'complex', 'fat', and 'smooth' come into play here. The tongue knows it has something, -but can't say exactly what. That's why wine taster terms seem to describe more of a sensation than a taste.
Tannin in Mead
The role of tannin in mead is as important as in wine to produce a balanced beverage and encourage clarification. Meadmakers can obtain a desirable level of tannin by using high tannin fruit varieties or by adding grape tannin which has been dissolved in hot water to the primary fermentation or fermented mead prior to bottling.
Tannin in Beer
Beer writers typically refer to tannins as polyphenols. Surprisingly, only about 2/3 of the tannins in beer are derived from the malt which means that 1/3 of them come from the hops. Reducing the amount of tannins extracted for the malt can be done be being mindful of the steeping water (or in the case of all-grain brewing, the mash). Don't steep grains longer than necessary (45 minutes is generally plenty) and don't exceed 170 degrees F. Unless your water is very high in carbonates, one gallon or less of steeping water per pound of grain should put the pH after the grain has been added in an appropriate range. You want the pH of the water after adding the grains to be between 5-5.5 pH. If it is much higher, try adding less water.
Hop tannins have the ability to help in the precipitation of haze-forming protein material during the boil (hot break) and cooling (cold break) of the wort. The addition of Irish Moss the last 20 minutes of the boil will aid in hot break formation.
Beers with light to moderate hopping are less likely to develop chill haze than highly hopped beers. So when designing recipes for highly hopped beers the probability of haze formation can be reduced by: 1) using smaller amounts of high-alpha hops which will add less polyphenols than large amounts of low-alpha hops; 2) pay particular attention to minimizing large proteins; and 3) plan on using fining agents.
There is evidence that only oxidized polyphenols will combine with proteins to form chill haze. Thus, avoiding splashing during transfer where hot wort may pick up oxygen is important not only regarding off-flavors but also haze formation.
PVPP (polyvinylpyrrolidone - trade named Polyclar) is the best choice for removing polyphenolic browning and tannins. Polyclar works by electrostatically attracting tannins as it sinks to the bottom of the fermenter. It reduces bitterness slightly and lightens the beer, wine, mead or cider a shade. The recommended amount for a 5 gallon batch would be 4-6 teaspoons. Mix the Polyclar with a cup of water, add to the secondary leaving enough head space to allow for some foaming and give the Polyclar about five days to settle to the bottom of the fermenter.