A slowly growing number of American winemakers are relying on the winemaking equivalent of a secret weapon. It doesn’t feature prominently in most winery tours as it doesn’t exactly fit in with the romance of oak barrels and sweeping vineyard vistas. In fact, it usually requires its own building with a natural gas line, plumbing and, occasionally, a separate insurance policy. But from dealing with smoke taint, to handling some adverse effects of climate volatility, to shaping the flavours and textures of high-scoring wines, a once-esoteric European winemaking technology called flash détente (as it was named by the French) increasingly has a role as an indispensable tool for some winemakers.
A combination of thermovinification and flash evaporation, flash détente involves the rapid heating of grape must or juice to between 175 and 190 °F (79–88 °C) and then moving it into a vacuum chamber. When the hot must enters a vacuum, the cellular structures of the grape skins and pulp burst open, in the same way they might if they were brought to the boil. But because this happens in a vacuum, the instantaneous evaporation of water cools everything down, allowing the extraction of colour and flavour compounds that you could ordinarily get only by cooking the fruit, which would result in much less desirable flavours.
The evaporation and capture of water from this process produces three critical outcomes that matter to winemakers: a concentration of the processed must or juice (usually the equivalent of around 2 brix in sugar accumulation), the removal of a wide array of unwanted volatile compounds (including pyrazines, various aerosols and some elements of smoke taint, all of which have conveniently low boiling points and end up in the captured steam), and the effective pasteurisation or denaturing of moulds, enzymes or other sources of grape spoilage.
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Image courtesy of Barry Gnekow.
