Winemaking
Cold soak (pre-fermentation maceration)
Holding crushed red grapes cold before fermentation starts, to extract in water rather than in alcohol.
The short answer
Cold soaking chills crushed fruit below the temperature at which yeast will start, typically for several days, so that extraction happens in an aqueous rather than alcoholic medium. The intention is more colour and softer tannin; whether it achieves that is genuinely debated.
Overview
The technique is strongly associated with Pinot Noir and with Burgundy, and it spread widely from there in the 1980s and 1990s.
It is one of the clearer cases in winemaking of a widely adopted practice whose benefits are argued about by the people using it.
How it works
The mechanism, at the scope it has actually been established.
Anthocyanins are water-soluble and extract readily without alcohol. Tannins are more soluble in ethanol. Extracting before fermentation therefore favours colour over tannin, at least in principle.
The must must be protected while it sits: cold slows spoilage organisms, and sulfur dioxide or a blanket of dry ice or inert gas is commonly used alongside.
Reported results are mixed. Some trials find greater colour stability and softer tannin; others find the differences small or absent by the time the wine is bottled.
A separate and less contested effect is that non-Saccharomyces yeasts and enzymes are active during the soak, which may contribute aromatically.
The literature does not support a general claim that cold soaking improves wine. It supports the narrower claim that it changes the extraction profile, with effects that may or may not survive to the finished wine.
Widely practised, and its benefits are contested among the producers who practise it. WineHQ reports the mechanism and the disagreement rather than picking a side.
Sources
Sources consulted
- UC Davis Department of Viticulture and Enology — University of California, Davis
- The Australian Wine Research Institute — AWRI
- The Oxford Companion to Wine — Oxford University Press
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.