Why has some of my pickled (canned) garlic gone blue-green?

Fresh garlic was put in a clean jar, boiling malt-vinegar and sugar was poured over and the jar sealed.
Some garlic turned blue-green and floated, some did not and sank.
I don't understand this.
It did the same a second time.

L

Comments

[Burf]

Raw garlic contains an enzyme that if not inactivated by heating reacts with trace amounts of sulfur (in the garlic) and copper (from water or utensils) to form blue copper sulfate.

If the garlic was not fully mature or dry, pigments in the garlic may turn green when in the presence of acid.

in either case, the garlic is still safe to eat

[lemonie]

Statements 1&3 sound like something I found on the internet by searching for it.
There is no copper in the jar, garlic, sugar, vinegar or utensils that I know of.
Sulphate would require an oxidation, and I'm not convinced that enough copper is seeping into the cloves and oxidising to sulphate (in anaerobic conditions). Also, why not equally for all of it?

Your second suggestion is more like it, but neither of us know what those pigments are...
:(

L

[iceng]

Was the garlic purchased ?
Do you make any conclusions from the appearance of more of the green 
colored wedges near the top of the jar then the bottom ( density ? ).
I cannot see the condition of the jar top, is the cap concave ??

Looking at the top color fluid reminds me of post PCB etch solution using a
Ferric Chloride etchant.

A

[Burf]

I can only guess but I would suspect that the greenish cast is from chlorophyll still remaining in the immature garlic bulbs. That's the only thing I can think of excluding some sort of external contaminant.

[Ninzerbean]

I believe Burf has the right answer plus this that I found "Are you using table salt instead of kosher or canning salt? That can cause the garlic to turn blue or green. Table salt contains iodine, which discolors whatever you're pickling. Use kosher
or pickling salt."

BTW I love picked garlic so much, the older it gets the better, like 8 years is prime.

[lemonie]

Yes he does, but I held off putting any salt in.

L

[lemonie]

Having thought about it, I think that's it - some chlorophyll precursors with the metal-centre, yes.

L

[okleydo]

I feel we could all use another picture here...

Here's a picture of my garlic cloves 9 days after soaking in Japanese rice vinegar. The jar cap and the paper underneath are supposed to be true white.

[lemonie]

I'm still eating mine (nice)

L

[CatTrampoline]

Both home-grown and store-bought garlic will turn blue-green when sauted in olive oil and vinegar (hence the name "blue garlic chicken" for one of my favorite recipies). I don't know the mechanism, but your experience is not an isolated incident.

[silverwindro]

It happens to me only with garlic from china, i dont make pickles from it, but if i smash 2 3 pieces of garlic and add water and a bit of salt it will turn green blue, even if you use yogurt, so i returned back to my original and pure garlic, because these chinese kind of garlic is bigger but i hate that color of blue green.

[lemonie]

That's interesting, I may experiment a bit...

L

[Vyger]

Maybe its just those weird mushrooms you ate and now its made you color blind.

Why don't you use standard canning jars and lids? If you reuse jars from other products like those you buy in a store you often cannot get a complete seal. Most health authorities here caution very strongly against reusing anything except jars specifically made for canning. It's possible you got a contaminate from the lid. The lids may not have been coated to withstand the acid combination you are using and so might be leaching metals out of the lid. Again a good reason to use canning lids that are made to resist acids.

[lemonie]

No, it's all fine. However, I will be having a look for mushrooms, I think it's about the season...

L

[ARJOON]

maybe some bacteria or something like an insect was in the garlic

[lemonie]

No, it ain't rotten.

L

[seandogue]

Was the jar decontaminated first by soaking in boiling water?

Sounds like you may have a culture of stowaways, busily building a new world. I'd be careful about eating it.

[thematthatter]

http://www.csiro.au/resources/preservation-in-oil-vinegar.html

I had one concern about botulism but if you used a large amount of vinegar and the pH was below 4.6 then it prevents the growth of botulism.

The link above says it may be an amino acid responsible for it. You might have already seen the link on google.