My soufflé turned grey

I have been trying to make a raspberry soufflé, because, well, I found a recipe, and it sounded tasty. It utterly failed, but because I'm stubborn, I wanted to keep trying until I got it right. However, every single time, it has turned grey. I've been beating the egg whites in a plastic bowl, and I've read now that you shouldn't do that for some reason or another, but never anything of them turning grey. Besides, the mixture doesn't turn grey until I add the raspberry mixture (which consists of raspberry, sugar, a bit of water, and maizena). My best guess is that the maizena somehow reacts with the whites, because I honestly have noe idea how raspberry would make eggs turn grey.

Help, anyone? The eggs were all fresh, and they looked completely fine up until I added the raspberry mixture, every single time. I just don't understand what's making them turn grey.

Best Answer

The pigments in raspberries can turn grey in an alkaline environment, and egg whites are one of the very few foods which are alkaline, although I am surprised the effect would be strong enough to notice.

You might wish to whip your egg whites with a bit of cream of tartar or lemon juice to help them be less basic, and therefore not react with the raspberry pigments.