Polyphenols are a complex group of compounds obtained from the bark, roots, leaves and fruit of many plants. Tannins are an important type of polyphenol which are soluble in water, colouring the water brown and giving both astringent and bitter tastes. For example tannins are found in tea (as tannic acid) and in the brown colouring of many creeks in the Tasmanian bush.
In wine production, tannins and other polyphenols are present in the skin, seeds and stems of grapes and in the wood of oak (which is often used to flavour the wines). In beer production, polyphenols are mainly provided by malt (about 80%) and to a lesser extent by hops. Polyphenols are also important in chocolate adding to the chocolate colours and flavours.