co-fermentation, the simultaneous fermentation of two or more varieties in the same vessel, is said to lift a wine’s floral aromas, enhance its texture, and improve the brilliance and intensity of the colour.
The technique has its origins in the Old World, most notably in the côte rôtie appellation in the northern Rhône. Here, the red variety syrah is co-fermented with the white variety viognier. Up to 20% Viognier is permitted, but 5–10% is more usual. This practice found increased favour in Australia and other parts of the New World from the 2000s. Co-fermentation does not have to be a combination of red and white grapes—in the United States, for example, co-fermentation may originally have been a natural consequence of field blends such as zinfandel and petite sirah. Another notable historical example is found in the chianti region of Italy, where the primary red grape, Sangiovese, was traditionally fermented with small amounts of the red variety Canaiolo Nero and the white varieties Trebbiano and Malvasia, although this practice has become uncommon.
