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Author Topic: Blue & green garlic puree  (read 14,339 times)

AI Summary
The discussion centers around the phenomenon of garlic turning blue-green when pureed, particularly when left overnight or frozen. Several users explain that this color change is due to chemical reactions involving anthocyanins and sulphur compounds in garlic, which can be influenced by factors like acidity, water quality, and the presence of copper. The consensus is that while the color change may be visually unappealing, it is safe to consume the garlic puree despite its altered appearance.

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Offline pete

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Blue & green garlic puree
« on: May 29, 2005, 09:34 AM »
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?
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Offline DARTHPHALL

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Re: Blue & green garlic puree
« Reply #1 on: May 29, 2005, 09:40 AM »
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 !!! ;)
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Offline Blondie

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Re: Blue & green garlic puree
« Reply #2 on: May 29, 2005, 09:53 AM »
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
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Offline DARTHPHALL

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Re: Blue & green garlic puree
« Reply #3 on: May 29, 2005, 09:56 AM »
You only need to worry when you hear voices emanating from your base mix  :P :P
what was that ?? don't feed the chicken a vodka Sandwitch !!!
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Offline pete

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Re: Blue & green garlic puree
« Reply #4 on: May 29, 2005, 10:03 AM »
Quote from: Blondie on May 29, 2005, 09:53 AM
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!!
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Offline Yellow Fingers

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Re: Blue & green garlic puree
« Reply #5 on: May 29, 2005, 11:07 AM »
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.
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Offline Curry King

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Re: Blue & green garlic puree
« Reply #6 on: May 29, 2005, 11:30 AM »
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!
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Offline pete

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Re: Blue & green garlic puree
« Reply #7 on: May 30, 2005, 10:44 AM »
Quote from: Yellow Fingers on May 29, 2005, 11:07 AM
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
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Offline Dylan

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Re: Blue & green garlic puree
« Reply #8 on: May 31, 2005, 12:22 PM »
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.
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Offline pete

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Re: Blue & green garlic puree
« Reply #9 on: June 01, 2005, 09:09 PM »
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
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