Naturally occurring sulfur in the garlic interacts with those enzymes, occasionally turning it slightly green or blue. ... Shifts in temperature, pH, and the age of the garlic can also come into play, so heating it or mixing it with acid might have some affect.

Why is my garlic blue?

Blue garlic may look off-putting, but it's perfectly safe to consume and tastes just fine. ... The color change is caused by a reaction between enzymes and sulfur-containing amino acids in the garlic (the same enzymes are responsible for garlic's flavor).

Why did my garlic turn blue when pickling?

When garlic is combined with an acid (such as vinegar), the allicin reacts with amino acids in the garlic to produce rings of carbon-nitrogen called. Pyrroles linked together form polypyrroles, which throw colors.