T he juice of most grape varieties is colorless. Grapes for white wine are also pressed immediately after picking, and the must starts to ferment. Maturation of white Burgundy and some California Chardonnays still takes place in oak casks, but vintners tend now to use large tanks of such modern materials as stainless steel. Minimum contact with the air retains the freshness of the grapes. T o make rose wines, the fermenting grape juice is left in contact with the skins just long enough for the alcohol to extract the required degree of color.
Vinification then proceeds as for white wine.
The resulting carbon dioxide is retained in the wine. Other methods, such as carbonation, are also practiced. With port and madeira, brandy added during fermentation kills off the yeasts, stopping fermentation, and leaves the desired degree of natural grape sugar in the wine. Sherry is made by adding spirit to the fully fermented wine. Its color, strength, and sweetness are then adjusted to the required style before bottling.