Phenolic ripeness describes the maturity of grape skins, seeds and tannin compounds at harvest. It is considered alongside sugar ripeness and acidity when deciding when to pick grapes, particularly for red-wine production. Phenolic maturity influences colour extraction, tannin texture, bitterness and the structure of the finished wine.
Growers and winemakers examine skin colour, thickness and ease of separation from the pulp, as well as seed colour, firmness and flavour. They may taste berries and seeds and assess tannin character, while also considering laboratory data and vineyard conditions. These sensory assessments are useful but are not a precise measurement of phenolic ripeness.
Sugar ripeness describes the accumulation of glucose and fructose in the berries and is used to estimate potential alcohol. Phenolic ripeness relates to the development of skins and seeds. Acid ripeness refers to changes in acidity and pH during maturation. These processes do not always occur at the same rate.
Example: a Cabernet Sauvignon crop may reach the desired sugar level while the seeds remain green and the tannins taste astringent, creating a harvest decision between alcohol, acidity and tannin maturity.
Weather, grape variety, canopy exposure, water status and vintage influence the relationship between sugar and phenolic development. Waiting for additional phenolic maturity can increase sugar and lower acidity, while picking earlier may preserve freshness but retain firmer tannins.
Chef’s note: phenolic ripeness is one factor in wine style, not a guarantee of quality. The finished wine also depends on extraction, fermentation, ageing and blending.
This term is one of hundreds covered in depth across OCS courses, learning paths, and 1-on-1 coaching with Chef Eric.
