What turned my garlic purple?

Question

I commonly use a technique when caramelizing onions, in which I add the sliced onions to a pan with salt, oil, and water. The water softens the onions and helps cook them evenly such that by the time it all boils away, they caramelize quickly and evenly.

I decided to use this technique on garlic the other day, when making a garlic and oil sauce for pasta, and was surprised to find that the garlic turned a fairly vivid shade of purple!

What happened? Was it some reaction the garlic had to the boiling? Or could it have been a reaction with the cast iron pan I was using?

Answer 1

From UC Davis:

Question: Why did my garlic turn blue? Answer: Garlic contains anthocyanins, water-soluble pigments that can turn blue or purple under acidic conditions. This is a variable phenomenon that is more pronounced for immature garlic but can differ among cloves within a single head of garlic. If you grow your own garlic, be sure to mature it at room temperature for a couple of weeks before using it.