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Chemistry question

Blackbagcate's picture

Hi I am new around here. I have been reading for a while and I thought I'd ask a question.


Why does chopped or minced fresh garlic sometimes turn bluish green in some dishes? Is it harmful? Can it be prevented? It looks terrible but it only happens sometimes, but I haven't really noticed a pattern as to the circumstances.

Li's picture

(post #26003, reply #1 of 16)

from FC #44

Technicolor garlic

When I cook with fresh garlic, it sometimes turns a bright

blue or blue-green color. What causes this, and how

can I prevent it from happening? The color is very unappealing, and I worry that it might be toxic.

—Penelope Clark, Thunder Bay, Ontario

David Stern replies: The discoloration of fresh garlic that you describe is a long-standing mystery for both cook and chemist. As you read this, scientists are working to unravel the secrets of this chemical curiosity.

Although not yet fully understood, we do know some things about this phenomenon: The blue-green discoloration is most commonly seen when garlic is exposed to highly acidic conditions, typically caused by the presence of vinegar. The cause is believed to be a reaction between the vinegar (or other acidic ingredient) and the proteins or sulfites in the garlic. It has nothing to do with photosynthesis or chlorophyll. The reaction seems to occur more often with hardneck (topset) garlic varieties than with softneck types. When the reaction occurs with one garlic clove, it won’t necessarily happen with all of the remaining cloves from the same bulb.

Our culture does indeed lack blue foods, but while it may be startling to behold, blue garlic is perfectly safe and delicious to eat. I don’t know of any sure-fire way of preventing discoloration, but you might try reducing the amount of vinegar in the recipe or experimenting with other lower-acid ingredients, such as lemon juice or wine.

David Stern is a certified organic vegetable farmer and the director of the Garlic Seed Foundation, an organization of growers and eaters dedicated to the improvement and production of garlic.


Cooks Talk
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Blackbagcate's picture

(post #26003, reply #2 of 16)

Wow thanks. I am a subscriber but I dodn't remember that question. Possibly because it had not happened yet  (to me) when I read it.


At least I know its not poison. And it would be better if it happened less randomly. Kids might like blue garlic.

NihonNoCook's picture

(post #26003, reply #3 of 16)

Oooh,  oooh!  (hand raised and waving rapidly)


1.  Eggs contain sulfur compounds (that's what produces the "rotten egg smell").  Egg yolks turn green on the outside when hard-boiled.  I don't know why, but it might have something to do with the sulfur.


2.  Onions contain sulfur compounds (that's why your eyes water - the sulfurous fumes turn into sulfuric acid in your eyes, and your eyes aren't thrilled about it).  Onions don't seem to suffer from the blue-green syndrome.


3.  I think garlic also contains sulfur compounds.  If so, maybe the sulfur compounds in the garlic are similar to the ones in the eggs, and in both cases it is the cause of the color change.


Ok, so the logic doesn't really follow, but it is an interesting thought.  Then again, I could probably get from patina'd copper back to garlic, if I tried hard enough, and I don't think the copper content in garlic is large enough to talk about.  Geez, I'll go sit in the corner now.  It's logic like this that makes "intelligent design" sound like real science.


Business Travel Goddess
StevenHB's picture

(post #26003, reply #4 of 16)

It's logic like this that makes "intelligent design" sound like real science.


And I had such a high opinion of you until you said this ;-)  ID is religion masquerading as science.



Without coffee, chocolate, and beer, in that order, life as we know it would not be possible

Without coffee, chocolate, and beer, in that order, life as we know it would not be possible
dixieleigh's picture

(post #26003, reply #5 of 16)

"1.  Eggs contain sulfur compounds (that's what produces the "rotten egg smell").  Egg yolks turn green on the outside when hard-boiled.  I don't know why, but it might have something to do with the sulfur."


Nihon. that is why I don't hard-boil eggs. Just barely bring them to a slight boil, turn off the heat immediately,  let them sit for about 12-15 minutes, then put into ice water. Voila, no green on the outside, white is tender, and the sulfur smell is not there.


 


 

 

 

Gretchen's picture

(post #26003, reply #6 of 16)

Nihon. that is why I don't hard-boil eggs. Just barely bring them to a slight boil, turn off the heat immediately,  let them sit for about 12-15 minutes, then put into ice water. Voila, no green on the outside, white is tender, and the sulfur smell is not there.



 Here is what I found on an egg site (yes, Virginia, of course there is one).


. Remove from heat and IMMEDIATELY place eggs under ice cold water or in a bowl of ICED water to chill promptly to help yolks stay bright yellow. Chill for a few minutes in the cold water until the egg is completely cooled. This is an extremely important step which prevents the greenish “ring” from forming on the surface of the yolk over time. If the egg is not chilled immediately after cooking an unsightly dark greenish ring will eventually appear on the outside of the yolk.

Dxie, they also point out that cooking at a lower temp can make them harder to peel.


Gretchen
Gretchen
CookiM0nster's picture

(post #26003, reply #7 of 16)

I hate to say it, but I've got to disagree with the egg site. I'm with Dixie on this one. I do my eggs exactly the same way she does. Never a green ring, and always the perfect texture.

Cook's Illustrated did a feature on boiling eggs a while back. They found the bring to a boil then turn off the heat method to work the best too.

Gretchen's picture

(post #26003, reply #8 of 16)

They didn't disagree with what Dixie said .  Said just to simmer barely--it was the cooling quickly as Dixie does that prevents the ring.  I have heard that boiling eggs in an aluminum pan will give the green ring.

Gretchen

Gretchen
CookiM0nster's picture

(post #26003, reply #9 of 16)

My mistake. from the bit you posted it sounded to me like they advocated simmering the eggs until done, not turning off the heat and letting them sit.

Basically, it's not submerging in cold water that prevents the green ring per se, it's overcooking that creates it. The cold water only helps because it stops any residual cooking. In theory, you could skip that step if you stopped the cooking sooner.

Edited 3/23/2002 2:49:04 PM ET by COOKIM0NSTER


Edited 3/23/2002 2:49:33 PM ET by COOKIM0NSTER

MEANCHEF's picture

(post #26003, reply #10 of 16)

Hardboiled eggs are not fit for human consumption.

 

shywoodlandcreature's picture

(post #26003, reply #11 of 16)

ah, but you can't have potato salad without 'em!


FWIW, I use the boil and turn off method too. No problem with greyish green rings.


 

MEANCHEF's picture

(post #26003, reply #12 of 16)

You MUST have potato salad without them.


Hope you are doing ok.  Miss you not being around much.


 


 


 

shywoodlandcreature's picture

(post #26003, reply #15 of 16)

Okay, just to keep peace in the family I won't serve potato salad when you and Mrs. MC come to visit.


It's nice to know I'm missed! Keeping well - just not a lot of time to hang around CT, though on vacation this week, so may catch up a bit. May even try to get comfortable navigating around this debacle of a board.

kai230's picture

(post #26003, reply #16 of 16)

Sandra, have you gone to Joe's page?


http://www.josephfusco.com


and I don't remember the rest of the addy because even that basic one isn't working for me, but he has a page that helps a great deal in explaining what is going on here.


Also, Mom always made potato salad w/hardboiled egg slices decorating the top, but never in the salad itself. I love them, the infrequent times I make them, but not in anything--just by themselves (well, w/mayo!)

Tuck's picture

(post #26003, reply #14 of 16)

Nice to see you Sandra.  I also use the bring to boil and turn off method, however I often have potato salad without egg and enjoy it just as much. 


~tuck The CT'er formerly known as cam14
If you can't be kind, at least have the decency to be vague

kai230's picture

(post #26003, reply #13 of 16)

 it's not submerging in cold water that prevents the green ring per se, it's overcooking that creates it. The cold water only helps because it stops any residual cooking. In theory, you could skip that step if you stopped the cooking sooner.


Interesting. Someone, somewhere suggested shaking the eggs in the pan to crack them in the cold water (after cooking) allowing the sulfer to escape or dissolve or something. Gosh I wish I could recall where I learned that.