Tannin

Tannin is found in grapes and apples, and it is similar to acid as it makes you pucker, but it is not an acid and does not affect the pH if more tannin is added. Tannins are sometimes described as the bitter tang and astringency to cider.

Tannin is particularly found in red wines because the tannin is present in the skins, which are not removed until the wine is done fermenting, unlike white wines were the skins are removed when pressed. Some regional ciders are low in tannins, while some mass produced ciders just use whatever apples they can get their hands on have very little tannins. The question of if tannins are a good thing or a bad thing really depend on the taster.

Brew supply stores sell grape tannin as a powder. I use it for fruit wines that probably don’t have much tannin, though others may use raisins to both sweeten their wine and add tannin. Other plant that have tannin include tea, elderberry, cranberries, strawberries, blueberries, pomegranates, persimmons, nuts that can be consumed raw, acorns, some beers, cloves, tarragon, cumin, thyme, vanilla, cinnamon, and most legumes.

Unfortunately, there is no simple way to test for tannins like there is for pH, as it a complicated lab procedure which you can read on Andrew Lea's website.

Since it is so difficult to test for, Andrew Lea suggests learning how to taste for tannin in apples. He wrote in a Cider Workshop email, “Think of tannin as the taste of cold tea without milk - astringent, slightly bitter, mouth puckering. Then see if you can identify that by taste in the apple. Be very sure to distinguish it from acid, which is the sharp taste.”