Strange Science: Red Onions Turning Green!

Lentil stewWe at Mad Scientist Journal have recently been undertaking some culinary experiments. Jeremy is learning to bake gluten-free breads, pies, and cookies, while Dawn is learning to make Ethiopian food.

One of our recent experiments was an Ethiopian lentil stew, which involved some red onions. The pot of stew made more than enough for leftovers. But when it came time to eat the leftovers, the onions had turned bright green, more the color of green peppers than any onion we’d ever seen!

Our first hypothesis was that perhaps the turmeric in the stew had dyed the onions–after all, a plastic lid that soaked in the water-filled pot in the sink had been dyed yellow. But we did a little research, and discovered that the cause was something entirely different.

Onions serve as a form of a litmus test, showing whether a substance is acidic or basic/alkaline. In the case of our lentil stew, it was apparently quite alkaline, and so the onions turned green. It’s also possible that they could have turned blue due to the alkalinity, which would have contrasted quite nicely with the yellow of the stew.

If you’ve got leftovers in your fridge that contain onions, you may see a similar reaction. Don’t worry, it’s still entirely edible. It’s just a little weird!

You can read more about the science behind this in the following articles:


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