Phenolic ripeness

Phenolic ripeness gauges the maturation state of the tannins, anthocyanins and phenolic compounds held in the grape's skin and seeds, distinct from sugar ripeness. Fruit picked at full phenolic ripeness yields supple tannins and stable colour, whereas an early harvest leaves green, astringent tannins. Growers assess it by tasting the berries and observing the colour of the pips, which turn from green to brown as ripening advances.