oenocyanin, a tannin product extracted from the skins of black grapes, comprising a mixture of pigmented tannins, some anthocyanins, and other phenolics. Marketed as a food colourant, oenocyanin is a valuable source of natural pigments available from pomace. Even though it is a tannin derived from grapes, and therefore of a composition more similar to the natural tannins of wine than many oenological tannins, regulations in most countries forbid the use of oenocyanin in red winemaking because it is classed as a colouring agent.
