Winemaking
Thermovinification and flash détente
Heating grapes to extract colour quickly — a technology behind a great deal of inexpensive red wine, and a tool for damaged fruit.
The short answer
Thermovinification heats crushed red grapes to extract colour and flavour before fermentation, which is then completed without skins. Flash détente heats the fruit and then drops it into a vacuum, rupturing the skin cells. Both extract fast and both change what is extracted.
Overview
These are industrial-scale techniques and they are not usually discussed in consumer wine writing, which is a reason to cover them rather than not.
They also have a specific quality application: dealing with fruit affected by rot or by smoke.
How it works
The mechanism, at the scope it has actually been established.
Heating to around 70–80°C releases anthocyanins from skin cells rapidly. The juice is then cooled, pressed off, and fermented as a white wine would be.
The result is deeply coloured and relatively low in tannin, because tannins extract more slowly and much of the extraction period has been eliminated.
Heat also denatures laccase, the oxidative enzyme carried by grey rot, which is why the technique is used to rescue rot-affected fruit.
Flash détente adds a vacuum stage after heating: the sudden pressure drop vaporises water inside the cells and bursts them. It extracts more thoroughly and is used for smoke-taint remediation because it allows tainted skins to be removed early.
The wines are generally made for early drinking. The extraction profile does not favour long ageing.
Widely used and rarely mentioned on labels. WineHQ records it because a reader is entitled to know how a category of wine is made, not because it implies anything about a particular bottle.
Sources
More in winemaking
Winemaking
Fermentation
Yeast converting sugar into alcohol and carbon dioxide — the step that makes wine wine.
Winemaking
How red wine is made
Fermenting grape juice in contact with the skins, which is where colour and tannin come from.
Winemaking
How white wine is made
Pressing the juice off the skins before fermentation, then fermenting the clear juice.