When I made it, the green chard turned to a dull, rather unattractive brownish green within about 10 - 15 minutes. I used a good quality Jerez vinegar. Thanks so much. ;o)
We dressed the greens just before serving when we made it, which may have prevented any visible browning in the photo. But we also didn't notice it turn brownish later on; it could have been because we cooked it down enough that it was no longer a vibrant green. Hopefully someone else will have more insight on this!
That's interesting, AntoniaJames, because I almost always add vinegar of some kind to my greens and they don't get discolored.
Sounds like you must be using industrial strength vinegar!
Just a simple Jerez from the Spanish Table. Not at all sharp, in fact. . . . . The same thing happened when I squeezed lemon juice over the Food52 Genius Pot Stuck Brussels Sprouts last week. Must be something about the acid, reacting to the green leaves. ;o)