What it is
E334 is L(+)-tartaric acid, recovered from the lees and crystalline deposits ("cream of tartar") of wine production.
Why it matters
Acidity regulator and antioxidant in wines, soft drinks, baking powder (cream of tartar), and confectionery.
What to do
Always vegan. The wine the tartaric acid comes from may itself use animal-derived fining agents (isinglass etc.) — but those don't carry through to the recovered tartaric acid.