Why Does My Garlic Turn Blue!
Posted: October 17, 2012
Answer: The blue or green color that you see is caused by an enzymatic reaction and is perfectly harmless. Natural sulfur containing compounds in onion and garlic breakdown quickly when exposed to oxygen to give us the typical pungent flavors we associate with these foods. These react in an acid environment with natural amino acids to form the harmless colored pigments you see.
The age of the garlic may have something to do with the reaction. Some have found that storing the bulbs for 2-4 weeks at 70°F will decrease the likelihood for this color to form. Some have also suggested blanching the individual cloves in boiling water for a minute to inactivate the enzyme. This may have an affect on the flavor though.
Garlic and onions can also turn green if stored in the light for too long. This time the color is the result of chlorophyll formation. Chlorophyll is harmless, but bitter flavors may accompany the color change. So store all your onions and garlic away from the light.