Blue Garlic

Today my daughter called to ask me a cooking question.  I have to tell you, this is one I've never been asked nor even heard before. 

She said she was making her famous meat balls, sauce and garlic bread.  She did her normal by running the garlic through a press and then putting it in a little olive oil to saute.  The garlic turned blue!  She then ran more through the press to go on her toast.  When the toast came out of the oven the garlic had turned blue.  Like I said, this was new to me so I did what I always do when I don't have the answer to a question, I Google.  This is what I found:

Garlic is known to contain sulfur compounds which can react with minute traces of copper to form copper sulfate, a blue or blue-green compound. The amount of copper needed for this reaction is very small and is frequently found in normal water supplies. Raw garlic contains an enzyme that if not inactivated by heating reacts with sulfur (in the garlic) and copper (from water or utensils) to form blue copper sulfate. The garlic is still safe to eat.

• If fresh garlic is picked before it is fully mature and hasn't been properly dried, it can turn and iridescent blue or green color when in the presence of an acid. It may be caused by an allinin derivative.
• A reaction between garlic's natural sulfur content and any copper in your water supply, or in the cooking utensils

  

  your are using (such as cast iron, tin, or aluminum) can sometimes change the color of garlic.
• The other sources of copper might be butter, lemon juice, or vinegar.
• Garlic will also turn green (develop chlorophyll) if exposed to an temperature change or is exposed to sunlight. Some people say it can be stored for 32 days at or above 70 - 80° F to prevent greening (but I'm not yet sure that is true).
• Are you using table salt instead of kosher or canning salt? That can cause the garlic to turn blue or green. Table salt contains iodine, which discolors whatever you're pickling. Use kosher or pickling salt.
   
• Different varieties or growing conditions can actually produce garlic with an excess natural bluish/green pigmentation (anthocyanins*) made more visible after pickling.
  * Any of various water-soluble pigments that impart to flowers and other plant parts colors ranging from violet and blue to most shades of red. This pigment is produced after chlorophyll is destroyed due to environmental changes. 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.

Don't worry, greenish-blue color changes aren't harmful and your garlic is still safe to eat. (unless you see other signs of spoilage).

So, if your garlic turns blue, now you know why.