4 Reasons Why Garlic Turns Blue or Green (Is It Safe?)
Surprises can be fun until you check your garlic to find it’s become a weird blue or green. it can be frightening. But this might not be as scary as it looks! To be completely safe though, it’s best to identify the exact reason behind its discoloration before chomping down on blue or green garlic.
Garlic can turn blue or green due to 1) mold, 2) metal, 3) acid, 4) age, and 5) variety. Moldy garlic can cause food poisoning and must not be eaten. All other causes of garlic discoloration, however, are harmless and still safe to eat.
There are multiple reasons why your garlic might change color. Out of all those causes, there’s only one that truly poses a danger. But it’s better to be safe than sorry, so here is a list of all known causes behind blue and green garlic!
1. Mold
Mold can cause garlic to rot and develop blue or green pigments. Soft and moldy garlic isn’t safe to eat and must be discarded and replaced immediately.
This is the least satisfying answer, but it is unfortunately one of the most common causes.
If the green or blue garlic feels soft and mushy and has developed some fuzz, the discoloration is most likely due to mold growth.
Pre-minced and pre-peeled garlic are especially prone to developing molds.
I find that without its protective skins, garlic is much more susceptible to moisture and rot.
You might be tempted to cut away the mold and use the garlic anyway. But the mold has likely spread further into the garlic tissue, even if we can’t see it.
For your health, it’s best to toss all the moldy green and blue garlic heads in the trash.
Keep them out of your compost though, as this can contaminate all of that healthy organic matter!
Learn more in: Is Mold Bad for Your Compost?
2. Reaction to Metals
Garlic has sulfur which will react when exposed to copper and form a compound named copper sulfate. This natural chemical compound can cause garlic to turn blue or green.
Something that we must remember is that garlic contains high amounts of sulfur. This sulfur is responsible for the spicy flavor of garlic that so many people love, including me!
However, when the sulfur in garlic comes into contact with metals such as copper, a chemical reaction will naturally occur. As a result of this reaction, a new compound called copper sulfate is established.
With this new compound in play, the garlic will eventually turn blue or green.
But what if you didn’t use anything with copper? Tap water can also cause this reaction.
Depending on where it’s sourced, tap water could contain trace amounts of copper and other minerals. When garlic comes into contact with such hard water, it can turn green or blue.
Additionally, garlic can react to utensils or cooking tools made from aluminum and brass.
3. Reaction to Acid
When left in vinegar or cooked with lemon juice, garlic can turn green or blue due to alliin compounds. This discoloration occurs when alliin reacts to the acid.
Another compound in garlic is alliin. Once exposed to acids such as vinegar or lemon juice, the garlic will produce blue and yellow pigments.
These pigments can vary and cause the garlic to look either blue or green. This can happen regardless of whether the garlic is whole or chopped.
I know how startling it can be when you attempt to pickle your garlic in vinegar, only to find it blue so many days later. But don’t worry, this reaction is totally normal!
4. Age
Young garlic that has been freshly harvested is more prone to discoloration. At this age, garlic is rich in reactive compounds like sulfur which can cause it to turn blue or green.
One reason why your garlic might be turning blue or green could be due to its age.
Fresh garlic has the highest amounts of sulfur and alliin and is most likely to react to copper and acid.
But this doesn’t mean older garlic is safe from this sudden discoloration. That old garlic bulb you left in the pantry should still contain these same compounds and can still turn green.
Older garlic bulbs aren’t harmful to eat either. To find out more, simply continue reading to see if discolored garlic is safe to eat or not!
5. Variety
Garlic varieties grown in different areas will also have different chemicals and be more likely to react to acid and turn green or blue.
The garlic variety you use can also play a part in its proneness to discoloration.
If you only experienced this discoloration with a new garlic variety, it was likely grown in a different condition, which ultimately influenced the chemical makeup of the garlic bulbs.
For example, scientists have found that garlic varieties from northern regions of China would have more green discolorations than garlic from Eastern China.
This can be trickier to identify unless you test out each garlic variety you have to see which tends to turn blue or green. But it is another factor to consider, so if you suspect this only happens with one type of garlic, consider swapping it with another one!
4 Easy Ways to Prevent Blue or Green Garlic
Green or blue discoloration in garlic can be prevented by 1) blanching the garlic before use, 2) making garlic powder, 3) avoiding certain metals, and 4) using freeze-dried onion powder.
If you’re not into this change of color, I get that. Luckily though, there are ways to prevent it and all you need to do is implement a few small changes. Here are the easiest ways to prevent garlic from turning blue or green.
1. Blanch the Garlic Before Use
To prevent garlic from turning blue or green, it is best to blanch them beforehand. Dip the garlic in boiling water for 15 seconds before bathing it in ice water. This will reduce the sulfur and alliin compounds and help prevent discoloration.
I cook garlic almost every day and have never experienced it changing color after this. It doesn’t take long to toast some thinly sliced garlic in oil, and the garlic oil you end up with is addictive!
By cooking the garlic beforehand, it’s less likely to react to things like vinegar or mineral-rich tap water.
If you plan on using this garlic for something like pickles, however, you can also blanch whole garlic cloves before pickling.
To blanch garlic, simply place your garlic cloves into boiling water or boil them for about 15 seconds before taking them out and submerging them in ice water.
Doing this can also cause a loss of flavor, so use this carefully!
2. Make Garlic Powder
Discolored garlic can be prevented entirely by turning fresh garlic cloves into garlic powder or granules. Because they have a lower chemical property, they will not have any reactions and turn blue or green.
Garlic powder does not contain any alliin to react with acid and will not turn blue or green at all.
If using fresh garlic is too much of a hassle, consider using them to make garlic powder. It does not have any alliin compounds to trigger and will quickly dissolve in your dishes.
Garlic granules are another popular option. Keep in mind, however, that the flavor won’t be nearly as strong as using real garlic. This is better for those who don’t use garlic often or dislike its pungent taste.
You can also buy garlic powder if you can’t make it at home. However, making garlic powder from scratch creates a fresher spice. Coriander, for example, is often ground at home.
3. Avoid Using Certain Metals
Avoid using copper, brass, or aluminum when cooking garlic. Instead, use wood or stainless steel, as they will not trigger the garlic to become blue or green.
Here’s one easy change you can make to prevent garlic from changing color. Just avoid using metal utensils made from brass or aluminum.
When it comes to cooking garlic, use stainless steel instead. It has no copper and can be found almost everywhere, making it a garlic lover’s best friend.
Pro Tip: To remove garlic odors from your hands, rub a stainless steel spoon over your fingers. The sulfur will bind to the steel, and the odor will leave your fingers.
Check the lids of your pickling jars to make sure they’re made of stainless steel.
You can also avoid using tap water to prevent any copper and other minerals in it from reacting to the sulfur in the garlic.
Wooden spoons are also great for stirring or handling garlic and will not cause any reactions.
4. Use Freeze-Dried Onion Powder
Research reveals that coating garlic with freeze-dried onion powder can prevent them from becoming green. The enzymes in the onions cause a reaction that inhibits the garlic from forming any discoloration.
It might be surprising, but scientists in Korea discovered in 2012 that using freeze-dried onion powder to coat garlic helped prevent them from turning green entirely.
This extra ingredient allowed the garlic bulbs to last longer without changing colors. It seems that the tear-jerking enzymes in onions react to the garlic and stop them from developing pigments.
It’s unknown whether raw onions or regular onion powder will have the same effect. However, I have noticed when using garlic with onions and onion powder, it never seems to change color, even when exposed to vinegar.
The only issue is that it might be tricky to find freeze-dried onion powder in regular stores.
So to help solve this, here’s a pack of freeze-dried red onions on Amazon that you can grind into a powder and mix with your garlic to help prevent them from changing colors!
Are Blue and Green Garlic Safe to Eat?
Garlic that has turned blue or green due to chemical reactions is not harmful and can be eaten safely. If the garlic is discolored due to mold, however, it can cause food poisoning when ingested and must be discarded.
After finding all that blue and green garlic in your food, you might be tempted to chuck it in the garbage.
Unless the discoloration is due to mold though, the garlic is probably still completely safe to eat!
Remember, garlic typically changes color as a result of chemical reactions. This is a normal process and does not make the garlic toxic or dangerous.
Green garlic, also known as Laba garlic, is even popular in China and is purposefully soaked in vinegar to achieve its green and blue hues. Typically, this pickled green garlic is eaten with dumplings.
If you still want to eat pickled garlic but don’t enjoy its new appearance, you can blend it or mix it in small amounts to enjoy its taste without seeing the discoloration.
Furthermore, garlic sprouts are also just as delicious and can easily be grown at home.
Read our article on How to Grow Garlic at Home - We Did it For You!
Can You Use Garlic That Turned Green in the Fridge?
Refrigerated blue and green garlic can still be eaten so long as it does not show any signs of mold or rot. Discard any soft or moldy garlic.
But what if you didn’t cook or use that discolored garlic at all? Many times I found my garlic turning green in the fridge despite it not being exposed to anything.
The most likely cause behind this is simply because the enzymes broke down and formed these hues as the garlic aged. Otherwise, these garlic cloves and heads are still edible and can be cooked.
Even if you’ve recently purchased it, most garlic heads are already several months old once they arrive at your local supermarket.
If you detect any mold, it’s unsafe to eat. It would be much better to throw any moldy green and blue garlic in the trash rather than cook it for dinner.
FAQs
Why does garlic turn green in honey?
Despite popular belief, honey is mildly acidic and contains numerous amino acids. When the garlic is placed in the acidic honey environment, it will turn blue or green. This is not harmful and a good indicator of healthy and active lactic acid bacteria in the honey.
Is there any naturally blue garlic?
Currently, there are no species of garlic that are naturally blue. However, most garlic varieties available in the market do turn blue when they are exposed to substances containing acids or minerals.
Summary of Why Garlic Turns Blue and Green
A garlic that has turned blue or green due to chemical reactions to metal, acid, aging, and variety is safe to eat. However, if the garlic is rotting and moldy, the garlic must be thrown away as it can cause food poisoning when ingested.
To prevent garlic from becoming blue or green, blanch the garlic before using it, use it to create garlic powder, avoid using metals like copper, and mix freeze-dried onion powder with the garlic to help prevent it from changing color.
Sources
- “Garlic and Organosulfur Compounds” by Jane Higdon, Victoria J. Drake, and Barbara Delage in Oregon State University
- “Mechanism of the Greening Color Formation of “Laba” Garlic, a Traditional Homemade Chinese Food Product” by Bing Bai, Fang Chen, Zhengfu Wang, Xiaojun Liao, Guanghua Zhao, and Xiaosong Hu in China Agricultural University
- “Bioactive Compounds and Biological Functions of Garlic (Allium sativum L.)” by Ao Shang, Shi-Yu Cao, Xiao-Yu Xu, Ren-You Gan, Guo-Yi Tang, Harold Corke, Vuyo Mavumengwana, and Hua-Bin Li1 in National Center for Biotechnology Information
- “Role of precursors on greening in crushed garlic (Allium sativum) bulbs, and its control with freeze-dried onion powder” by Jungeun Cho, Eun Jin Lee, Kil Sun Yoo, and Seung Koo Lee in National Center for Biotechnology Information
- “Vegetable blanching directions and times for home freezer storage” by Carol Burtness in University of Minnesota
