Since Ugni Blanc is a late budding and late ripening variety, the harvest is generally a full two weeks after that of Bordeaux. The grapes are typically harvested with a potential alcohol of 8–10% abv (alcohol by volume). Producers in cognac machine harvest and the berries are sorted on the tractor and removed immediately from any juice that may be expressed. The addition of sulfur is forbidden because of the likelihood of off aromas after distillation. Even in years when the growers are permitted to sulfur, Hennessy does not use sulfured wine.
Grapes are gently pressed in a pneumatic press (vertical presses are not allowed) over the course of four hours, and the temperature of the must (the pulp of crushed grapes) is stabilized through the use of a heat exchanger. Very few additions are made to the must, and acidification is not allowed.
The first cuvée
is inoculated with yeast cultured from the area and fermentation in subsequent cuvées is assured by use of a 'pied de cuve
’, a small starter culture. The wine ferments for 8–10 days in epoxy-lined cement and stainless tanks at a temperature a little below 27°C but fairly warm.
The wines are racked off the gross lees (that is the sediment is removed from the wine), although in many cases the wine is distilled with the fine lees and left unfiltered. In some cases, extra lees can even be added into the wine to give it a richer, more buttery texture. This is a risky procedure since the lees can burn in the boiler, ruining the batch. In general, malolactic fermentation is not encouraged, though it can't be blocked, either, because of the restrictions on the use of sulfur.
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