Why do my onions go green?

Lifeisbutadream

When I make a feta cheese and red onion tart (which is very tasty might I add ) the onions always go green they are not green when I put them in, only when they have come out of the oven - I just dont understand it.

It doesnt affect the taste and it is fine when it if for us, but I would like to be able to make one and it look nice!

Can anyone help?

PollyFlinders_3

I don't know the answer but the other day I roasted some whole garlic cloves straight from the garden (without the paper skins) alongside some beetroot, and the outer layer of the garlic went an interesting shade of blue, but like your onions they tasted OK. Must be something to do with the colouring in the red onions/beetroot I guess.

Dazi

Sorry I don't know either, but the other day I grated some garlic onto salmon, wrapped it in foil and baked in the oven.The garlic came out green, as you said it all tastes ok, but if you were doing it for guests not so good. I put mine down to the foil, will try again without it next time.

absolutebounder

Onions contain sulphites and these react with calcium in the cheese to create complex comopounds like Ca.H3so3 which has a green tinge to it

Lifeisbutadream

absolutebounder wrote: »

Onions contain sulphites and these react with calcium in the cheese to create complex comopounds like Ca.H3so3 which has a green tinge to it

I am impressed with that answer!

Any solutions?

lesley1960

I made up a batch of the curry base ( Curry Queens recipe ) the other day , and at the boiling up onions stage it turned out green !! ...........

absolutebounder

lesley1960 wrote: »

I made up a batch of the curry base ( Curry Queens recipe ) the other day , and at the boiling up onions stage it turned out green !! ...........

I expect you live in a hard water area. Onions also contain copper which means you could get a little copper carbonate to give a green colour or also there is calcium in hard water