Must-is the juice of freshly pressed grapes, that contains various quantities of pulp, skins, stems, and seeds, called pomace or grape solids, which typically comprise between 7–23 percent of the total weight of the must. These components, and the time they are allowed to be in contact with the juice, are critical to the final character of the wine.
When the winemaker judges the time to be right, the juice is drained off the pomace which is then pressed to extract the juice retained by the matrix. Yeast is added to the juice to begin the fermentation, while the pomace is often returned to the vineyard to be used as fertilizer. A portion of selected unfermented must may be kept as Süssreserve, in order to be added prior to bottling as a sweeting component.
Some winemakers create a second batch of wine from the used pomace by adding a quantity of water equivalent to the juice removed, letting the mixture sit for 24 hours, and draining off the liquid. This wine may be used as a drink for the employees of the winemaker or as a basis for grappa.