Large Scale Must Fermentation

More and more, must is being fermented on a large scale. This is done in vast fermentation tanks, some of them twenty feet high, made of fiberglass, reinforced-polyester resins or stainless steel usually of eighty to one hundred butts capacity. Early examples of the former were unsatisfactory as very small quantities of chemicals were leached out, and even the minutest trace of a foreign substance will spoil the flavor of a wine.

These problems have now been overcome and the most modern vessels are chemically inert, though stainless steel is generally preferred where cost is no object. When used for fermenting they are only filled to about 80 percent of their capacity to allow room for frothing and expansion. An advantage of these big tanks is that they can be very carefully monitored, especially with regard to temperature.

If the temperature rises excessively from the ideal of about 25-30°C a spray of water can be turned on, either by hand or automatically by thermostat, pouring down the outside and cooling the tanks very effectively. This technique has been used in many of the leading vineyards of the world, even as far north as Champagne, where heat is not normally a problem.

In the southern vineyard areas, it has immensely improved the wines, as many were spoiled in the past by being fermented too hot, growing coarse and lacking fragrance. In the sherry country it is probably fair to say that the traditional method is capable of giving as good a wine. The casks are small so that temperature rarely gets out of hand; but there are always a few that do.

If the temperature rises excessively from the ideal of about 25-30