Frozen cabbage

Jalima thanks, it was cooked I wasn't bothered about sogginess as I was only going to make bubble and squeak to go with a bacon and egg breakfast. I think you could be right about an enzyme reaction it certainly looked very odd with some green and some purple leaves. I took one look and thought no I'm not risking that.

I don't know, but just wondering - was it leftover cooked or uncooked cabbage?
I'm sure I've frozen both and I'm sure the uncooked was fine (only kept it for a couple of weeks) for a stir-fry, the cooked went into the food waste bin because it was too soggy!

You may need to have blanched it to stop the enzymes causing a reaction.