I love adding garlic to my dishes when I cook. It has so many health benefits, from reducing blood pressure to being naturally high in antioxidants and antibiotics.
It is such a versatile vegetable and adds that pop of flavor you need (or well, so I believe).
Imagine my surprise when I discovered that the garlic I bought from a local Mexican market was purple. What turned it purple? Was it still safe to eat? Or was it ready to be added to my compost heap?
What Turned My Garlic Purple?
Garlic turns purple when it interacts with something that’s acidic, like vinegar, lemon juice, or utensils, or cookware made from copper, tin, aluminum, or iron. More specifically, garlic contains an odorless sulfur compound, called alliin, and an enzyme called alliinase. When these two mix, like when you crush or chop garlic, allicin is produced, which is also why garlic’s odor gets more pungent. When a metal object or acidic solution is introduced, the allicin mixes with the amino acids in the garlic to produce pyrroles. Depending on how many pyrroles cluster together, the color of the garlic changes. On another note, you can buy natural purple garlic, which is simply another variety of garlic.
What Is Purple Garlic?
While many people believe that purple garlic is garlic that has gone bad, this isn’t true. Instead, purple garlic is simply another garlic variety. In fact, there are three types of purple garlic:
- Purple stripe garlic
- Marbled stripe garlic
- Glazed purple garlic
White garlic is most commonly found in stores. If you see purple garlic in the U.S., it was most likely imported from Mexico. However, Russia, China, Tasmania, Australia, Spain, and Italy also cultivate purple garlic.
Purple Garlic vs White Garlic
White garlic has a soft, flexible, short stem that grows from the center of the vegetable. The stalk doesn’t grow through the bulb, so the cloves can grow close together.
On the other hand, purple garlic has a hard stem (also called hardneck) and the stalk grows from each garlic head. As such, these cloves don’t grow as closely together as those of white garlic.
The outer layer or skin of a white garlic is white, while purple garlic’s skin has a purple streaked hue.
The cloves of purple garlic are either purple or white. Purple garlic doesn’t have as long of a shelf life as white garlic.
There are more cloves in white garlic, which is bigger, compared to that of purple garlic. White garlic is generally pungent and has a strong taste; purple garlic is milder and juicier.
Purple garlic has a higher content of alliin and alliinase. Anthocyanin, which is a vacuolar pigment, is found in all garlic; however, it is more concentrated in purple garlic than white garlic.
This anthocyanin is what gives purple garlic its purple color, and depending on the pH, anthocyanin can also be black, blue, or red.
Can Garlic Turn Purple?
If the garlic you bought isn’t the natural purple garlic variety, then yes, it can turn purple.
The garlic I bought was purple – the cloves are a much richer purple than the outer skin. I just grabbed the garlic and never noticed mine was originally purple.
So I was quite shocked to see the purple garlic as I was about to chop it up. I’ve since then been educated about garlic varieties and why garlic can turn purple, blue, or green (weird, I know).
Garlic can turn purple when it is exposed to acidic conditions. The acid reacts with the alliin (an odorless sulfur compound) and alliinase (an enzyme) in the garlic. These compounds give garlic its distinctive flavor and pungent odor.
When the sulfur and enzyme mix, it forms allicin, an organosulfur compound.
So when you chop and crush garlic, alliin forms, and this is why the garlic smell gets stronger (much like when you chop onions).
When chopped or crushed garlic (in which allicin has formed) is combined with an acidic compound, it causes the garlic to turn purple, green, or blue.
This is because the allicin mixes with the garlic’s amino acids, and pyrroles, or rings of carbon-nitrogen, are formed. Many pyrroles create polypyrroles, which cause a color change.
Not much research has been dedicated to this phenomenon, but it’s believed that this effect is more pronounced when the garlic hasn’t yet matured versus mature garlic.
So what acidic conditions can cause garlic to turn purple? These are:
- Placing garlic in water that’s laced with iron, aluminum, or tin
- Placing metal utensils or bowls next to garlic
- Adding crushed or chopped garlic to pans made from tin, aluminum, iron, or copper
- Adding lemon juice or vinegar to garlic
Is Garlic Turning Purple Safe to Eat?
Yes, garlic that has turned purple, blue, or green is indeed safe to eat, provided your garlic hasn’t gone bad.
Your garlic changing color doesn’t affect how it tastes; it might just be an eye-sore in your dish, especially if it turned blue or green.
How to Prevent Garlic Turning Purple?
To prevent garlic from turning purple, blue, or green:
- Avoid metal cookware, so use enameled or stainless steel cookware and utensils
- Use distilled water when pickling garlic (distilled water is metal-free)
- Use iodine-free salt (like sea salt or kosher salt)
- Store garlic away from direct sunlight
- Blanch garlic for 10 seconds; this may prevent coloring, but it can affect the taste
How Do You Know Your Garlic Turned Bad?
Don’t use garlic if it:
- Is soft (fresh garlic should be firm)
- Is fuzzy or moldy
- Smells foul
- Loses its pungent, sharp smell
- Has brown spots
- Has started to yellow – a lot
- Has green sprouts inside – and while safe to eat, the sprouts add a bitter taste to your meal, so remove these
Frequently Asked Questions About What Turned My Garlic Purple
Is it ok to eat purple garlic?
Real purple garlic is perfectly safe to eat as it is simply a variety of garlic. Garlic that has turned purple because it reacted to something acidic, is also perfectly safe to eat.
How can you tell when garlic has gone bad?
Garlic that has gone bad has brown spots that form on the cloves. For white garlic, when it is off, it turns more yellow or brown, and green roots will start to sprout from the center of the garlic.
Should garlic be refrigerated?
It is best to store your garlic in a cool area in your kitchen. This area should be dry too. So store your garlic in a shady corner, the pantry, or a kitchen cabinet. Moisture from refrigerating garlic causes mold to form on the surface of the flowering plant.
The Last Purple
So I learned quite a lot – it felt like I had a chemistry lesson again with the acid, enzymes, alliin, and pyrroles.
While I now prefer buying purple garlic – because it’s pretty and has a milder flavor profile – if my “normal” white garlic turns purple, I know it is still edible, provided it isn’t soft, smells off, becomes moldy, or has brown spots.