The percentage of stems to be kept will depend on the desired wine type. This percentage generally varies from 20 to 100% depending on the grape variety and the stems' characteristics (ripeness, quality). Empirically speaking, no significant difference has been observed below this value during tasting.
At Domaine d'Eugénie and Clos de Tart, some vats are vinified with the stems. When this is the case, the percentages vary from 30 to 80% depending on the profile of the plot and the maturity.
For instance, the reasoning behind the percentage of whole bunches at Domaine d'Eugénie is as follows:
The vintage's ripeness is the number one criterion. In a less mature vintage like 2013, this was not the selected option. It is an option used most commonly in warmer and classic vintages. The percentage is variable and is redefined annually according to grapes' profile. In the first trials, 30% of whole bunches were incorporated, then 50 and 70% for certain wines. The Clos Vougeot, for example, which is vinified in two vats, is vinified with one tank at 50% whole bunches and the other at 85%. Stems bring smoothness and improve the wine's structure.
At Clos de Tart, a study is being carried out to further our knowledge of the compounds responsible for the organoleptic properties of the wines and to refine the percentage of whole bunches used.
White grapes: destemming is not very common for white grape harvests, because it has some possible disadvantages. However, keeping white grape stems during pressing improves juice drainage into the juice trough and requires little or practically no breaking up of the press cake. Their presence can also reduce the content of thermo-stable proteins in the must and thus reduce the risk of protein breakage in white wines. Destemming of white grapes should thus be avoided when possible, except in the case of skin maceration or mechanical harvesting (Detailed explanation of white wine vinification).
Filling a vat at Domaine d'Eugénie