I have a recipe for
cooking with herbs and wine.
It requires that one prepare
a wine/herb mixture in
advance. I mixed garlic and
herbs with wine in a bottle
and allowed it to sit for a
long time, as instructed. It
appears that the garlic has
turned blue inside the
bottle. I am concerned about
poisoning my guests. Do you
have any insight? Thank you
for your consideration.
Ron & Vanessa
Linda, I have almost the
same problem with my garlic
changing color, only mine
turned sort of green when I
placed it in white vinegar.
Used to put it in oil but
that got messy sometimes and
I thought I would give
vinegar a shot. Did I goof
up or is it like the wine
deal? - Bob W.
I just made my first
herbed vinegar, using
chives, garlic chives,
pineapple sage, rosemary and
garlic. It looked great last
night, I got up this morning
and the garlic has turned a
shade of blue/green or
green/blue. Did it mold? The
vinegar is in old wine
bottles (cleaned and heated
in boiling water on the
stove eye like canning jars)
with cork stoppers and wax
helping to hold the stoppers
down. I did heat the vinegar
in a metal pan. Is that the
reason? The only thing
heated was the vinegar and
then poured over the herbs
in the wine jars. OK now,
can you tell me what I did
wrong, or if I can use this
when it is ready? I was
going to give it to friends,
but I don't want to make
them sick! That was a lot of
work and now I just feel
sick. Thanks, I will await
My daughter made me a
bottle of flavored
vinegar a couple of days
ago for Christmas, and
was so disappointed that
the garlic had
discolored. It looks
like only the cloves
touching the glass
turned blue, but we
haven’t opened the
bottle to confirm. Can
you tell us what may
have caused this? Other
than the blue garlic(!),
the vinegar smells
wonderful. Thank you so
much any ideas you can
provide! Have a
Wonderful New Year!
Check out my article on
Garlic Turning Blue or Green
International Journal of Food Science & Technology,
Identification of Two Novel Pigment Precursors and a
Reddish-Purple Pigment Involved in the Blue-Green Discoloration of
Onion and Garlic, written by Shinsuke Imai,* Kaori Akita, Muneaki Tomotake,
and Hiroshi Sawada, Received for review August 12, 2005. Revised
manuscript received December 5, 2005. Accepted December 10, 2005.
By using a model reaction system representing blue-green
discoloration that occurs when purees of onion (Allium cepa
L.) and garlic (Allium sativum L.) are mixed, we isolated two
pigment precursors (PPs) and a reddish-purple pigment (PUR-1) and
determined their chemical structures. PPs were isolated from a
heat-treated solution containing color developer (CD) and either
L-valine or L-alanine, and their structures were determined as
2-(3,4-dimethylpyrrolyl)-3-methylbutanoic acid (PP-Val), and
2-(3,4-dimethyl-1H-pyrrolyl) propanoic acid (PP-Ala), respectively.
Next, PUR-1 was isolated from a heat-treated solution containing
PP-Val and allicin, and its structure was determined as (1E)-1-(1-((1S)-1-carboxy-2-methylpropyl)-3,4-dimethyl-1H-pyrrol-2-yl)-prop-1-enylene-3-(1-((1S)-1-carboxy-2-methylpropyl)-3,4-dimethyl-1H-pyrrol-2-ylidenium).
The structure of PUR-1 suggested that PP molecules containing a
3,4-dimethyl pyrrole ring had been cross-linked by an allyl group of
allicin to form conjugated pigments. While PUR-1 is a dipyrrole
compound exhibiting a reddish-purple color, a color shift toward
blue to green can be expected as the cross-linking reaction
continues to form, for example, tri- or tetrapyrrole compounds.
What the above means:
The discoloration is due to pigments
that form between sulfur compounds in garlic and amino acids. When
the garlic tissue is disrupted, as happens in processing, an enzyme
is liberated and reacts with it to form thiosulfinates compounds
that then react with the natural amino acids in the garlic to form
blue pigments. The age of garlic determines how much isoalliin there
is in the first place, and the nature of the processing determines
how much enzyme is liberated.
Original thoughts and ideas:
Garlic is known to contain sulfur compounds which can react with
minute traces of copper to form copper sulfate, a blue or blue-green compound. The amount of
copper needed for this reaction is very small and is frequently
found in normal water supplies. Raw garlic contains an enzyme that
if not inactivated by heating reacts with sulfur (in the garlic) and
copper (from water or utensils) to form blue copper sulfate. The
garlic is still safe to eat.
If fresh garlic is picked before it is fully mature and hasn't been
properly dried, it can turn and iridescent blue or green color when
in the presence of an acid. It may be caused by an allinin derivative.
between garlic's natural sulfur content and any copper in your water
supply, or in the cooking utensils your are using (such as cast iron, tin, or aluminum) can sometimes change the color of garlic.
sources of copper might be butter, lemon juice, or vinegar.
Garlic will also turn green (develop chlorophyll) if exposed to
an temperature change or is exposed to sunlight. Some people say it
can be stored for 32 days at or above 70 - 80° F to prevent greening
(but I'm not yet sure that is true).
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
Different varieties or growing conditions can actually
produce garlic with an excess natural bluish/green pigmentation
(anthocyanins*) made more visible after pickling.
* Any of various water-soluble pigments
that impart to flowers and other plant parts colors ranging from
violet and blue to most shades of red. This pigment is produced
after chlorophyll is destroyed due to environmental changes.
This is a variable phenomenon that is more pronounced for
immature garlic but can differ among cloves within a single head
of garlic. If you grow your own garlic, be sure to mature it at
room temperature for a couple of weeks before using it.
Don't worry, greenish-blue color changes aren't harmful and your
garlic is still safe to eat. (unless you see other signs of