Phenolic Ripeness
The state of ripeness in grape seeds and skins where tannins have fully polymerised and seeds have lignified (turned brown and woody), producing ripe, smooth tannins rather than harsh, green ones.
In depth
There are two types of grape ripeness that winemakers track separately: sugar/acid ripeness (the traditional measure — brix/sugar level vs acid level) and phenolic ripeness (the state of the skins, seeds, and stems).
Grapes can reach sugar ripeness while their seeds and skins are still phenologically unripe — particularly in cool vintages or with some varieties. Unripe seeds produce harsh, bitter, astringent tannins. Unripe stems are green and herbaceous. Only fully ripe (phenologically ripe) seeds and skins produce soft, ripe, integrated tannins.
Indicators of phenolic ripeness include: seeds turning from green to brown (lignified); tannins that taste ripe and smooth rather than green and harsh; stems that are brown, woody, and snap clean rather than green and bendy.
Phenolic ripeness is the key reason why producers in warm climates (like Barossa or Napa) generally find it easier to produce ripe-tannin wines, while cool-climate producers (like Burgundy or Champagne) must choose their harvest date carefully to balance phenolic ripeness with preserved acidity.
Whole-bunch fermentation depends entirely on phenolic ripeness — unripe stems add green tannin; ripe stems add desirable spice and structure.
Related exam topics
Frequently asked questions
- What is the difference between sugar ripeness and phenolic ripeness?
- Sugar ripeness measures the accumulation of glucose and fructose in the grape berry — it predicts potential alcohol level. Phenolic ripeness measures whether the seeds, skins, and stems have reached full maturity, producing soft, ripe tannins. A grape can be sugar-ripe but phenologically unripe, which leads to high alcohol but harsh, green tannins. Warm climates make it easier to achieve both; cool climates often require trade-offs.
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Practise questions on this topic
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