Phenolics
A broad group of chemical compounds in wine — including tannins, anthocyanins, and various acids — that contribute to colour, structure, bitterness, and astringency.
In depth
Phenolics are extracted from grape skins, seeds, and stalks during maceration, and can also come from oak barrels. The two main categories relevant to wine quality are tannins (which contribute astringency and bitterness) and anthocyanins (which provide red/purple colour in young red wines).
Tannin phenolics polymerise (join together in chains) during ageing. Young wines with high tannin may feel harsh and drying on the palate; with time, polymerised tannins feel softer and more integrated. This is the chemical basis of why red wines benefit from bottle ageing.
Anthocyanins are unstable and fade with age; in older red wines, colour shifts from deep purple through ruby to garnet and brick. Anthocyanins can also bind with tannins to form stable pigmented polymers, contributing to the colour of aged red wines.
For the exam, phenolic maturity (phenolic ripeness) is the state at which seeds and skins are fully ripe and will yield ripe, soft tannins rather than harsh green ones — a key concept in harvest timing decisions.
Related exam topics
Frequently asked questions
- What is the difference between tannins and anthocyanins?
- Both are phenolic compounds. Tannins contribute astringency, bitterness, and structure, and are found in skins, seeds, and stalks. Anthocyanins are colour pigments found in red grape skins that give young red wine its purple and ruby hues. Both are extracted during maceration.
- Why do red wines change colour as they age?
- The red/purple colour in young wines comes from anthocyanins, which are chemically unstable and gradually fade. With age, colour shifts from purple-ruby through garnet to brick and tawny at the rim. Some anthocyanins bind with tannins to form stable pigmented polymers that contribute to the deeper core colour of well-aged reds.
Practise questions on this topic
Use Vinlecta to practise exam-style questions that test your knowledge of phenolics and related topics.