Topic: Blue & green garlic puree

[pete]

I puree garlic with a little water and salt.
If I leave it overnight, it goes a blue green colour.
Adding oil stops this.
I have seen it turning this colour in a restaurant kitchen too.
Does anyone else get this?
Does anyone know why it does this?

[DARTHPHALL]

I think its something to do with the chemical reaction with the atmosphere/oxygen, rather like the coloring of wool in medieval times ( a plant name i have forgoten was used & as you took it from the bowl of this mixture it turned blue green as a direct reaction to oxygen etc ..etc..),
If i make KD basic mix its almost a transparent green before the tin of tomatoes goes in !!!

[Blondie]

Hi all,

I usually puree my garlic in large quntities and freeze it in Tbs measures.

When it thaws it goes blue / green very quickly and I have always been very reluctant to use it like that.  Have I been worrying without cause, IS IT SAFE TO USE IT WHEN IT HAS CHANGED COLOUR?

cheers all,

Blondie

[DARTHPHALL]

You only need to worry when you hear voices emanating from your base mix 
what was that ?? don't feed the chicken a vodka Sandwitch !!!

[pete]

When it thaws it goes blue / green very quickly and I have always been very reluctant to use it like that.? Have I been worrying without cause, IS IT SAFE TO USE IT WHEN IT HAS CHANGED COLOUR?

I've chucked loads away because of this colour problem, but I'm going to use the green puree tonight.
I will post tomorrow how I am feeling!
It's only 10 am and we're talking curry!!

[Yellow Fingers]

You might be talking it Pete, but I've been eating it. Breakfast at 8 this morning was 2 poppadoms with chutney, cold tandoori chicken and some chicken dhansak!

And the blue/green question. Well garlic contains compounds called anthocyanins which are plant pigments. They act as pH indicators, i.e. they change colour depending on the degree of alkalinity or acidity of the surrounding medium. This is why some people get bright green base sauce and some do not, it depends on the type and amount of onions and salt and even the nature of your local water amongst other things.

Also garlic is high in sulphur compounds which react with copper from the pan or the water to form copper sulphate which is blue.

As far as I know these compounds are totally safe in the quantities in which they occur in curry cooking.

[Curry King]

I puree garlic with a little oil and water and keep it in the fridge and it usualy lasts a few weeks and ive never seen it go like that!

[pete]

Also garlic is high in sulphur compounds which react with copper from the pan or the water to form copper sulphate which is blue.

Well, I won't argue with that!
It does look exactly a copper sulphate colour.
I guess the copper comes from the water in the copper pipes.
Maybe if you used bottled water you wouldn't get it.
Anyhow I used the blue garlic last night and survived.
Definitely NOT poisonous

[Dylan]

Pete,
Apparently, if garlic cloves are soaked in lemon juice or vinegar for a couple of hours prior to pureeing (to remove the risk of botulism bacteria) the resultant puree often goes bluish green. It seems that sulphur compounds in the garlic react with the acidity. I would guess they're reacting with a slightly acidic water supply.

[pete]

It's funny how we all knew about this but, when I wrote to the blender manufacturer, they had never heard of the problem!!
Thanks for all the advice