thermovinification, process sometimes used in red winemaking, particularly in cool climates such as those of upper new york state or after particularly cool growing seasons, whereby heat, about 70 °C/158 °F, is applied to grape clusters or must before fermentation to liberate anthocyanins, or colour, from the skins (see temperature). The heat treatment is immediately followed by cooling then pressing to liberate coloured juice, which is then fermented much as in traditional white winemaking. Thermovinification is particularly valuable in making everyday wines from grape varieties low in anthocyanins, or from better-coloured grape varieties that are not fully ripe or are affected by moulds such as botrytis rot, which destroys colour in dark-skinned grapes. In the latter case, the heat inactivates the colour-destroying enzymes secreted by the mould. The heat also destroys pectoclytic enzymes, making clarification more difficult, and oxidases such as laccase, reducing the risk of oxidation, especially useful for botrytis-affected grapes. Heat treatment also volatilizes isobutyl-methoxypyrazine, thereby reducing green aromas. Thermovinification is rarely used in making fine wines, however, which almost invariably rely on extended maceration to extract colour and flavour from the grape skins. However, at Ch de Beaucastel in the Rhône, the Perrins have for many years heated the grapes very briefly to 80 °C/176 °F immediately after destemming. The grapes are then cooled to cellar temperature prior to fermentation. This is said to increase the extraction of colour and flavour and avoid the addition of sulfur to the must. See also flash détente.
