Why Does Garlic Turn Blue?


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When cooking or pickling garlic, it can turn from its usual white color to blue or green. Blue is not only a weird food color but also notoriously unsettling and unappetizing. The last thing you’d expect is a plant-based ingredient to turn blue when cooking. That said, most people are shocked whenever garlic turns blue. Though rare, you are likely to encounter blue or green garlic in the kitchen. So, why does garlic turn blue? Is blue garlic safe to eat? In this article, we will answer these questions in great detail.

The Chemistry Behind Garlic

Garlic is rich in various naturally occurring sulfur compounds. These are the likes of allicin, ajoene, vinyldithiins, and so on. Its other constituents include saponin and enzymes. When you cut, crush or chop garlic, you initiate a series of chemical reactions.

These reactions release the pungent smell of fresh garlic. The more you break down garlic, the more the smell becomes stronger. But when you leave the garlic bulb intact, these series of reactions do not occur. The same chemical processes also contribute to garlic turning blue or green in some circumstances.

So, Why Does Garlic Turn Blue?

Garlic turns blue when some of its amino acids and natural enzymes react with its sulfur compounds. These reactions produce various multi-pyrrole molecules that could be likened to chlorophyll. This explains the change in pigmentation that forms a blue or green color.

Fresh garlic hardly changes its white color because the sulfur compounds and enzymes are intact. However, as for the mature garlic, these sulfur compounds and enzymes are broken down by the aging process. As such, older garlic is likely to turn blue or green easily.

What Should Garlic Look Like?

If you see a few cloves of blue or green garlic, then the garlic has undoubtedly lost its natural color. The color of fresh garlic should fall between white and a distant yellow.

Variables That May Prompt Garlic to Turn Blue

Growing Conditions

The region and conditions of cultivation can aid garlic color change. For example, garlic that is grown in high temperate climates turns blue easily because it produces a large number of enzymes responsible for color change. This is evident in some parts of China, where garlic turns blue a few months after harvesting.

Garlic Form

When preparing garlic either for preservation or cooking, people use different preparation methods. For example, while you may prefer to grate garlic, another person may prefer to chop it. Minced or grated garlic tends to turn blue easily. This happens because the garlic has been cut and its enzymes exposed. In such a form, the enzymes break down effortlessly due to air exposure.

Presence of an Acid

When garlic interacts with other acidic ingredients such as vinegar or lemon juice, its color may change. The change of color results from the amino acids in garlic reacting with allicin, a naturally occurring enzyme present in garlic. The chemical reaction leads to the production of carbon-nitrogen rings that are also known as pyrroles. Pyrroles link together to form polypyrroles. When three pyrroles come together, they form a blue color, while four pyrroles combined together form green.


Temperature change may also prompt garlic to turn blue. In warmer temperatures, garlic color is more likely to turn. For instance, semi-cooked or blanched garlic loses its color and turns blue because of exposure to low heat.

The Natural Color of the Garlic Bulbs

There are two varieties of garlic; white garlic and purple garlic. If you spot garlic with purple-like skins among white garlic, that’s the purple garlic. The difference between purple garlic and white garlic is the color. White garlic is the most common variety of garlic. When you go to your local grocery stores, this is the garlic you are likely to find.

The two varieties have different skins in terms of color, but their cloves are alike. Both of them have white cloves. However, purple garlic turns blue faster than white garlic.

When Does Garlic Turn Blue?

Garlic turns blue during preparation. This could be when you are preparing to cook it or pickling it for preservation purposes. Pickled garlic turns blue when you mix it with acidic ingredients. Ingredients with mild acid can initiate a series of chemical processes responsible for blue garlic.

When cooking, chances are that you will wash your garlic at some point. Also, you will chop it, mix it with other ingredients such as onions. During all these processes, the garlic may come into contact with compounds that will trigger a color change. When this happens, the garlic may or not turn blue.

When cooking garlic, it may turn green accidentally. This happens if its sulfur compounds interact with copper agents, which are present in utensils, water, or other copper-rich ingredients. In such cases, copper sulfates prompt the color change in garlic. This has nothing to do with multi-pyrrole pigments. Utensils such as pans are made of metals, including aluminum, tin, and iron. The enzymes in garlic can react with these minerals and turn blue.

How Long Does It Take for Garlic to Turn Blue?

When exposed to certain conditions, garlic turns blue in a matter of minutes. So you can get distracted for a few minutes in the kitchen while preparing it, only to find out that it has turned blue.

Is Blue Garlic Safe to Eat?

Blue garlic looks strange for many people. Some think something is horribly wrong with it, and it could be poisonous. However, blue garlic is completely safe to eat. In some countries like China, people prize colorful garlic.

After harvesting garlic, they don’t consume it immediately. Instead, they use vinegar to induce garlic’s color change. Their desired garlic color is blue-green, and they can age it for months to achieve the color transformation. These people believe that blue garlic tastes better than white garlic. In China, colorful garlic is tremendously popular during the Laba harvest celebrations.

Does Garlic Lose Flavor if It Turns Color?

Garlic’s flavor is not lost when it turns blue. The chemical reactions that lead to the garlic’s color transformation do not affect its taste. According to Dr. Luke LaBorde, a food scientist at Penn State University, blue garlic is not toxic. The chemical reactions leading to the blue and green pigments on the garlic are natural.

There are ways of telling whether your garlic is fresh. Aged garlic that has been in storage for a long time develops green sprouts. Although they are small in size, their green demeanor makes them easy to point out. These shoots do not mean that the garlic is unhealthy for consumption, but they are indicators of its lack of freshness.

Can You Differentiate the Taste of Blue Garlic and Normal Garlic?

When garlic turns blue, its taste does not change. Blue garlic retains the warm spicy taste of normal garlic. If the taste of your blue garlic is awfully strange, the chances are that it has gone bad. And you should not eat it.

Blue Garlic Facts

  • If there are no visual signs such as mold or a foul unusual smell coming from your blue garlic, then it is safe to eat.
  • It is not possible to always turn your garlic blue in the kitchen because there could be many variables causing the color change. Besides that, you can’t tell which variable will turn your garlic blue. This is because garlic’s color change occurs accidentally, and replicating it is highly unlikely.
  • When garlic turns blue, you can’t change its color back to white. Heating further may turn turquoise garlic a little bit pinkish but not white.

How to Prevent Garlic From Turning Blue

Blue is not a color that anyone is accustomed to seeing in their food. Some people may find it tremendously unsettling. If blue or green garlic is unappetizing to you, you can do something about it.

First off, always use fresh garlic to avoid color transformation. Prepare your garlic fast because as soon as you cut it, you initiate several chemical reactions. These are the same chemical processes responsible for the surprising garlic color transformation. The slower you are, the higher the chances of your garlic turning blue.

Keep your garlic in a cold place and only remove it when you are ready to add it to the pan. This is because high temperatures speed up the chemical reactions responsible for garlic’s color transformation. Chop your garlic separately from other ingredients because they may contain agents that induce blue and green pigments.

When cooking, start with the onions first and add the garlic later. If you are cooking plain garlic, cook it fast under high heat. Cooking your garlic and onions separately will reduce the chances of your garlic turning blue significantly.

Onions belong to the same family as garlic. As such, they also bear various sulfur compounds. When you cook garlic and onions together, you are providing the garlic with more building blocks that may interfere with its pigmentation.

Remember, the naturally occurring sulfur in garlic may react with copper sulfate on your utensils. And this will prompt a color change. Wash your garlic with pure distilled water to avoid such reactions, and keep your garlic white.

Tap water contains trace minerals that can lead to your garlic color transformation. These are the likes of copper sulfates, and they readily react with the natural enzymes in garlic.

Avoid mixing raw garlic with any acidic ingredients, such as lemon juice or vinegar. However, if your recipe dictates that you should use these acidic ingredients, you can work around it. Acid increases the speed of pigmentation in garlic. Therefore, you should let the garlic cook first before adding the acidic ingredients. The ultimate objective is to deactivate the enzymes responsible for chemical reactions that turn garlic blue.

As you add salt to your garlic, ensure it is iodine-free. Sea salt and kosher salt are ideal for cooking garlic. These don’t have minerals that can react with the sulfur compounds in garlic.

If possible, use enameled cooking pots or stainless steel pans. The goal here is to avoid utensils with ca iron, tin, and aluminum.

Be aware of chlorophyll formation in your garlic, as this can lead to coloring. Store pickled or fresh garlic away from direct sunshine.

Is There a Difference Between White and Blue Garlic?

Besides the color change, there is no big difference between white garlic and colorful garlic. Some people claim that blue garlic tastes better, but there is no documented evidence to back these claims. When you cook garlic, regardless of whether it turns blue or not, it tastes the same.

What is Laba Garlic?

At first glance, colored garlic shocks a lot of people. However, some cultures prize colored garlic. They go to an extent of intentionally making it change its color.

Laba garlic is a popular type of colored garlic in China. This garlic is preserved in vinegar, and it is a well-known snack in some parts of China. However, unlike blue garlic, laba garlic is made through a well-thought-out process. Therefore, it may take several months to make it ready.

Laba garlic is not much different from blue garlic. The only difference is that it’s jade green, and it tastes sour and spicy. The principle behind the change of color is similar to blue garlic. Nonetheless, the Chinese people make it intentionally for the Laba festivals.

Why Do Some Garlic Turn Blue and Others Not?

It all narrows down to the garlic’s age. Aged garlic has more chemical precursors than fresh garlic. So, where you buy your garlic may determine its color change. Also, how your prepare, preserve, and use garlic matters.

For example, garlic from the same market, harvested at the same time from the same farm, may end up in different households. However, in one household, the garlic can still change its color, while it will keep its natural color in the other house. So, the change of color in garlic can narrow down to the way you handle it.

Regardless of whether garlic is blue or white, it is good for you. It is not only healthy but also super delicious. Garlic reduces blood pressure, boosts your immunity, lowers cholesterol, and much more. Not unless your garlic has gone bad or grown mold, the color should not deter you from eating it. Moreover, it is not possible to predict the blueing of garlic, and it’s difficult to control it. Most of the time, you will not even notice the color change. As such, you should continue enjoying garlic recipes without any qualms.

People Also Ask

Is It Safe to Eat Garlic That Turns Green?

You can eat garlic that has turned green without any safety concerns. The green color is caused by a chemical reaction from high heat or acidic ingredients and does not indicate spoilage. The garlic is safe to eat as long as it doesn’t have mold or a bad smell.

Why Does Garlic Turn Blue When Soaked in Vinegar?

The reason why garlic turns blue when it comes into contact with acidic ingredients like vinegar is that the sulfur compounds in garlic react with the acids. This chemical reaction leads to the formation of a pigment called anthocyanin, which causes the blue color.

Does Garlic Turn Blue with Heat?

It is true that heating garlic can cause it to turn blue. This happens when the sulfur compounds in the garlic react with iron, tin, or aluminum in the cookware at high temperatures, resulting in the formation of anthocyanin. To prevent this from happening, opt for enamel-coated or stainless steel cookware when cooking with garlic.






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