Tanniine leidub peamiselt punases veinis, andes veinile iseloomuliku mõrkja ja kuiva maitse.Punases veinis leiduvad tanniinid pärinevad nii viinamarjadest, millest vein valmistati, kui ka puidust vaatidest, milles seda laagerdati. Nende hulk veinis võib varieeruda sõltuvalt viinamarjasortidest ja valmistamismeetoditest.
Tannins are therefore defined functionally. They are polyphenolic compounds that bind to and precipitate proteins. It’s a slightly complicated picture: not all polyphenols can act as tannins, and not all phenolics that bind proteins are tannins, but it’s still a useful definition.