Grappa
Grappa is an alcoholic beverage, a fragrant, grape-based pomace brandy of Italian origin that contains 35 to 60 percent alcohol by volume (70 to 120 US proof).
Overview
The flavour of grappa, like that of wine, depends on the type and quality of the grapes used, as well as the specifics of the distillation process. Grappa is made by distilling the skins, pulp, seeds, and stems (i.e., the pomace) left over from winemaking after pressing the grapes. It was originally made to prevent waste by using these leftovers. A similar drink, known as acquavite d'uva, is made by distilling whole must.
Grappa is now a protected name in the European Union. To be called grappa, the following criteria must be met:
Produced in Italy, or in the Italian part of Switzerland, or in San Marino
Produced from pomace
Fermentation and distillation must occur on the pomace—no added water
Criterion 2 rules out the direct fermentation of pure grape juice, which is the method used to produce brandy.
Criterion 3 has two important implications. First, the distillation must occur on solids. Thus, it is carried out not with a direct flame but with a bain-marie or steam distillation; otherwise, the pomace may burn. Second, the woody parts of the grapes (the stems and seeds) are co-fermented with the sugar-rich juice; this produces a very small amount of methanol, which is much more toxic than ethanol. Unlike in the similar process of making red wine, in grappa the methanol must be carefully removed during distillation. That is why there is an Italian law requiring winemakers to sell their pomace to grappa makers; this is a measure that was taken against moonshine operations, which are now very rare in Italy.