Just because wine is made from grapes doesn’t necessarily make it vegan friendly.
Its true that grapes are almost the only ‘ingredient’ but there are other things that happen to them on their way into your glass. The fermentation process involves yeast, and that’s OK but once the wine has fermented it can be rather like a cloudy soup and even after it is filtered, it still isn’t as clear as you’d expect or want it to be when you pour it.
It is what is used to clarify the wine that can make it vegan friendly or not:
Filtered wine still has very small particles of sediment floating around in it from the fermentation process. Many winemakers want to remove these as they can make the wine unsightly and can also affect the aroma and taste.
So to remove these very fine particles, a fining agent is added to the wine. The fining agent acts like a coagulant, attracting the fine particles, binding them all together so that they become large enough to fall to the bottom and then be filtered out or the wine taken off the top.
There are a number of commonly used fining agents, some of which are derived from animal products such as egg whites or gelatine. Although the amount of the fining agent that remains in the wine, if any at all, will be minuscule, it is the use of animal based agents that results in a non-vegan friendly wine.
There are many other fining agents that are not animal based and there is no doubt that these are increasing in popularity. Different fining agents, however, can remove or enhance different flavours in the wine so winemakers will continue to use those that provide the best result for their own wines.
So if you are looking for a vegan friendly wine, its best to check the label or if still unsure, many wine makers produce technical guides that will specify what agent they used.