Buzz
Aside from some exceptions like blueberries, blue raspberry candy, and specific cocktails, blue is not a color you'd typically expect in your food—especially when it's unintentional. Blue (or turquoise, or green) garlic is particularly surprising. Normally, garlic should be beige, golden brown, or even a rich, sticky black, but much like the bright patterns found on a poison frog, blue garlic raises a few concerns.
What causes this phenomenon?
I first came across garlic with a bluish tint during a sous-vide experiment, although it's more commonly observed during the pickling process. The blue color results from a chemical reaction between a sulfur-rich amino acid (alliin) and an enzyme (alliinase). These compounds are separate in whole garlic, but when garlic is chopped, minced, or crushed, they interact, producing the characteristic pungent flavor and smell. According to The Spruce Eats, introducing an acid (like pickling vinegar) can trigger the color change, though metals may also initiate a similar reaction.
When garlic comes into contact with an acid (like vinegar), allicin reacts with the garlic’s amino acids, forming carbon-nitrogen rings called
pyrroles.
Pyrroles that are linked together form polypyrroles, which produce various colors. Four pyrroles combined make green (the reason chlorophyll is green), and three pyrroles connected create blue.
A similar color-changing reaction can occur when garlic interacts with minerals from specific metals, such as copper, aluminum, iron, and tin. These minerals may come from cookware made of those metals or from trace minerals in the water itself.
The acid isn’t consumed in the reaction but helps initiate the change by further breaking down the garlic’s cellular structure. It's possible to pickle a large batch of garlic without noticing the color transformation, depending on the garlic’s freshness. According to food science expert Harold McGee, aging garlic to promote the color change is a common technique in northern China, where the allium is soaked in vinegar to make Laba garlic—an attractive pickle that’s known for its vibrant color and tart, slightly spicy taste:
As stated by chemists at the China Agricultural University in Beijing, aging garlic allows it to accumulate higher concentrations of the chemicals responsible for the color change, while fresh garlic tends to have little to no green color. A strong green hue in Laba garlic appears only with acetic acid, the primary acid in vinegar (and also found in sourdough), because it effectively penetrates internal membranes and facilitates the chemical reactions that produce the green pigment. This pigment is chemically related to chlorophyll, the compound that gives all green plants their color.
Is it safe to eat?
As you might expect, blue, turquoise, and green garlic are completely safe to eat and taste almost the same as beige garlic. You can even prepare your own Laba garlic and enjoy it as a pickle alongside dumplings (or any greasy dish that could use a tangy, spicy kick).
How to stop your garlic from turning blue
Although blue garlic isn’t harmful to your health, there are times when the blue color might seem unappealing, especially if it's minced into small pieces and spread on garlic bread or stuffed inside a chicken breast.
Using fresh garlic or cooking it before it interacts with any acid can help. If you're pickling, a quick blanch can deactivate some of the enzymes that cause the color change. Steer clear of copper, aluminum, and cast-iron cookware to reduce the chances of garlic turning blue. However, the simplest way to handle blue garlic is to just eat it. At the very least, it’ll give you a chance to impress your friends at a dinner party—an accomplishment I always aim for when dining with friends and acquaintances.
