Blue garlic?

Madison.

In preparation for having a bunch of folks over for food tomorrow night, I started making some pickles. They've been a consistent hit around here, particularly the garlicky dill cucumbers, so I figured I'd try something like that again this time, only with the sort of vegetables that look good this time of year: onions, carrots and fennel. A quick taste test tells me they're a might heavy-handed on the fennel, since everything's taken on a distinctly anise-like quality, but it's not too bad. Good to make a mental note for next time, though.

What's weird, and why I bring this up, is that the garlic cloves have turned blue. I think this may have happened before, but I'm not sure. And, since I don't usually think of bright blue as a naturally-occuring food color, I felt obligated to check up on this. According to Harold McGee's oh-so-handy On Food And Cooking:

Red-Purple Anthocyanins and Pale Anthoxanins
The usually reddish anthocyanins and their pale yellow cousins, the anthoxanins, are chlorophyll's opposites. They're naturally water-soluble, so they always bleed into the cooking water. They too are sensitive to pH and to the presence of metal ions, but acidity is good for them, metals bad. And where chlorophyll just gets duller or brighter according to these conditions, the anthocyanins change color completely! This is why we occasionally see red cabbage turn blue when braised, blueberries turn green in pancakes and muffins, and garlic turn green or blue when pickled.

He goes on to explain a few other interesting tricks with color-changing anthocyanins:

• Adding alkaline substances to red wine will turn it into white wine.¹
  
• Quinces and other pale-colored, very tannic fruits can be cooked to produce anthocyanins. As the aggregate phenolic chemicals break down, they become anthocyanins, rendering the fruit both gentler on the tongue and bright red.
  
• Trace amounts of metals in the cooking liquid can turn different anthocyanins all sorts of different colors.

These same chemicals are the ones that turn some kinds of asparagus, snap beans and carrots purple. Since they're only present on the outside, they usually end up diluted in cooking water or interact with the other plant cell chemicals, losing their color.

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¹McGee points to Marcus Gavius Apicius, the author of the only known surviving Roman cookbook. Apicius suggested:

To make white wine out of red wine. Put bean-meal or three egg whites into the flask and stir for a very long time. The next day the wine will be white. The ashes of white grape vines have the same effect.

Neat party trick, especially for someone you really loathe. I can't imagine it tasting anything other than awful.