When is a protein used?
An animal protein is used to finish a wine. "To finish a wine" is to stabilize the wines, soften a harsh or astringent character, or improve clarity. The traditional fining agents that can make a wine unsuitable for vegans. "Egg whites or casein (a protein found in milk) can be used to remove tiny particles of sediment in a wine that cannot be removed by filtration," according to Decanter Magazine.
What makes a wine vegan?
Wines made without animal products are vegan wine. There two ways a vegan wine is made (1) the winemaker permits the particles to sink naturally to the bottom of the wine, or (2) non-animal fining products are used. A form of clay or pea protein is used instead.
Wine producers are not required to include finishing elements on the label. However, some producers publish a V on the wine label to indicate a Vegan wine.