Those of us familiar with various brewing techniques already know about this, but it’s relevant for most of you.
One of the biggest problems with the old red-with-meat, white-with-fish wine pairing advice is that it entirely misses the boat on vegetables, and of course wines work beautifully with even vegetarian meals. But before we talk about pairing Syrah with seitan or Albariño with avocados, there’s something you may want to know: not all wines are — in the strictest sense of the words — vegan or even vegetarian.
The fact is that while an increasing number of wines are technically vegan, a substantial number of wines still use animal-based products in the “fining” process: clarifying the wine by removing proteins, yeasts and solid materials that would otherwise make the wine cloudy and visually unappealing, or would even create off-flavors or aromas. Fining agents act as magnets for unwanted materials, and carry the glop to the bottom of the barrel or tank. Then the wine is “racked” — poured off into another holding container, where the wine is separated from the solids. Racking is just like decanting, except on a humongous scale. LINK