De-stemming is carried usually carried out with a mechanical de-stemmer, where the bunches are passed along the inside of a perforated drum. The perforations are only large enough to let the berries through: the stems are ejected from the other end of the drum.
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Advantages of de-stemming |
Disdvantages of de-stemming |
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| White wines |
- Stems can release bitter & herbaceous flavours into wine.
- It allows more fruit to fit into the press (and presses are an expensive bottleneck in the white winemaking process).
- Other MOG can be removed at de-stemming.
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- A poor de-stemmer will often damage the stems so badly that more bitter & herbaceous flavours are released than if a de-stemmer had not been used.
- Pressing without the stems is slower as the stems provide drainage channels.
- De-stemming is not appropriate for vintages destined for sparkling wines.
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| Red wines |
- Stems can release bitter & herbaceous flavours into wine.
- Stems release water and potassium and absorb colour and alcohol.
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- The presence of stems will reduce compaction of the cap of pomace in the tank and make temperature control and phenolic extraction easier.
- In some varieties, the stems can release good quality tannins which improve mouthfeel, stabilise colour and reduce the damage done by oxidation.
- De-stemming is not appropriate for vintages destined to undergo carbonic maceration (e.g. Beaujolais Nouveau)
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Machine harvested fruit does not normally need de-stemming, except to remove MOG.
