Science - Introduction to Chemical Reactions

 The OH and I love garlic. I've cooked with it a lot over the past 12+ years, used it in all kinds of recipes. Today, however, was the first time I've had garlic turn a vivid blue-green colour during the cooking process.

This morning I put a whole chook in the slow cooker; threw in some sliced onion and garlic; sprinkled on some salt and pepper; and then squeezed a lime over it all. Nothing special, just an end of the week, throw-it-together kind of meal. An hour or so later I was cleaning up after the kids had breakfast and as I wiped down the bench I glanced at the slow cooker. I was quite alarmed to see that all the garlic had turned green! It was the same kind of green that copper turns when it oxidises. Not the kind of colour you expect to see in food unless the ingredients list includes a whole bunch of numbers!

I called Shmoo and Loo in and they were fascinated by the strange colour. We couldn't figure out what was going on with it. I was worried that it might be some weird garlic disease/mould that only became apparent during cooking so I quickly Googled it. Turns out there are lots of people out there that have been freaked out by turquoise coloured garlic and lots of theories about why it occurs. The best source of info seems to be here...

"The colors occur when enzymes and amino acids present in garlic react with the sulfur compounds responsible for garlic’s pungent smell. The reaction causes different multipyrrole molecules to form. Different types of multipyrrole molecules are responsible for the different pigments. The multipyrrole molecule most familiar to us is chlorophyll, produced by plants in the presence of light; however, chlorophyll is not produced by the cooking or pickling processes that turn garlic blue."

 Interesting! We kept an eye on the garlic as it continued to cook and it slowly turned more green than blue and after a while the green colour disappeared.

Colour starting to fade

Then, tonight, I was preparing to cook some silverbeet and cabbage to go with the chicken. Usually I just saute the onion and garlic, throw in the veg, and stir through a splash of soy sauce and a little lemon or lime juice. I had everything prepped and ready to go. I cooked the onion and added the garlic. Then I noticed the lime sitting there, ready to be used later. Instead, I squeezed a little of the juice straight onto the garlic. Voila! Reaction replicated. Shmoo and Loo marvelled over the turquoise garlic. What an awesome colour (although not one I usually like to see in my food!).

We'll have to explore some more kitchen science chemical reactions :)