Why Does Maple Syrup Mold – [A Detailed Answer]

Maple syrup is one of the oldest sweeteners in North America and is a staple in many diets worldwide. Maple syrup is derived from sap collected from maple trees. Have you ever wondered why your maple syrup will begin to mold within a few weeks? I have researched to find the answer; let’s get into this.

Why does maple syrup mold?

Maple syrup gets moldy when the sugar content drops below 15 percent. When the sugar is below 15%, the moisture content in the sugar drops, leading to mold growth. There are 2 types of sugar in maple syrup – glucose and fructose. Sugars are known to produce carbonic acid, which can cause mold. 

These sugars are responsible for the sweet taste of maple syrup. Fructose is less sweet than glucose, making it less likely to cause mold. In addition, maple syrup contains several minerals like potassium, sodium, and calcium that help keep the syrup from fermenting.

The first step is to look at the moisture content; sugar crystals absorb moisture from the air. As the humidity increases, the crystal size decreases, and the amount of moisture in the sugar determines how fast the sugar crystals are consumed. When the crystals are tiny, the sugar is more likely to become moldy.

In this guide, we’ll explore why maple syrup mold is moldy maple syrup harmful and how to prevent mold.

Why Does Maple Syrup Mold

Mold on Maple Syrup

Before we start talking about the prevention of maple syrup mold, let’s first figure out why maple syrup mold exists in the first place. Maple syrup is susceptible to mold because there is a lot of sugar, and sugar attracts mold. Making maple syrup starts by boiling down maple sap or water with the minerals and sugars extracted from maple trees.

Moldy maple syrup isn’t something we’d want to serve our family. However, this mold is actually harmless to humans. A mold is a form of Penicillium that lives on dead wood, decaying vegetation, or other organic matter, according to the USDA. Most often, the fungus grows on hardwoods, especially maple trees. Maple trees typically produce only a tiny amount of syrup compared to other trees, and the resulting yield may be meager.

Maple syrup is a natural sweetener, but mold can sometimes occur in freshly opened containers. Since this mold is a natural part of the product, many people don’t realize it. However, when the mold starts to grow, it smells and looks less appealing. While it’s common to remove the mold, you can also prevent it from growing in the first place. 

Can Maple Syrup Grow Mold?

Maple syrup can grow mold when exposed to water and air (mold likes warm temperatures and high humidity). However, it’s worth noting that it takes a lot of maple syrup to grow mold, but a little can grow quite quickly.

A recent study in a scientific journal by researchers from the University of Toronto found that maple syrup, just like wine, cheese, and other foodstuffs, may grow mold if it sits around long enough. The research, published in the International Journal of Food Microbiology, found that if a sample of maple syrup was left for six months at room temperature, the sugar content and flavor tended to change as mold grew.

The maple syrup contains cyclopentenone, which is converted into the mold metabolite mycotoxin by molds. Researchers found the highest level of mold spores in maple syrup that was stored in the refrigerator for at least two weeks.

Also, check our guide on freezing maple syrup, for more information about the topic.

How Can You Tell If Maple Syrup Is Bad?

If the maple syrup tastes bitter or metallic, it is likely not safe to consume. Maple syrup can also become unsafe if stored over the summer at room temperature or if it contains debris that got into the container while being poured.

Maple syrup starts to go bad when the sugar separates from the water. This typically happens when it is heated high enough. A small drop onto a cold surface like a spoon or knife blade to check whether your maple syrup is still good. If the drop turns into a continuous line, your syrup has already started to spoil!

Sap from maple trees is used to make maple syrup, which is then boiled down to make maple syrup. The main reason for boiling the sap is to remove the water and crystallize the sucrose into sugar. But that doesn’t mean that maple syrup is bad. In fact, it has many health benefits.

Is Maple Syrup Mold Serious?

Yes. It’s serious but not invariably fatal. Maple syrup mold is something that affects maple syrup producers. The disease is caused by a fungus that grows in moist conditions and grows on the sap as it runs off the maple trees. It doesn’t affect the sugar content of the syrup. Symptoms include dark and sticky patches on the trees and black or red mold growing on the sap.

How to Prevent Maple Syrup Mold?

In order to prevent the growth of mold in maple syrup, it is essential to keep a sealed container and keep it in a refrigerator. If you don’t have a sealed container, ensure that the lid is closed tight when the syrup is not used. If your container has a hole in the top, you should use a piece of tape to seal it shut.

If you find mold on your maple syrup jars, try to prevent the mold from spreading. If you see a spot of mold on your jar, here are some steps you can take:

  • Fill the jar with white vinegar
  • Cap the jar and leave it for a day or two
  • Empty the vinegar and wash out the jar
maple syrup in bottle

Is Maple Syrup Mold Harmful?

The maple syrup mold is usually harmless, and there are no reported cases of maple syrup mold poisoning. However, this type of mold is often confused with blue mold, which is very dangerous to human health.

It is a common mold found in many areas, similar to sugar maple syrup. This type of mold also can grow in other areas like coffee or dairy products. This is a highly debated topic; some people believe that mold in maple syrup is simply an ingredient that gives it a unique flavor, while others think that mold could be harmful to the body and should not be consumed.

However, you should avoid consuming the moldy maple syrup; the most crucial part of this mold is the spores it produces. When these spores are inhaled or ingested, they can affect the human body due to their toxicity and growth capabilities.

What to Do If You Eat Moldy Maple Syrup?

If you eat moldy syrup, there are many things you should do as soon as possible.

  • Go to your nearest doctor to make sure they can detect any health problems that might arise from eating moldy maple syrup.
  • Try to avoid eating any more food or drink for at least six hours.
  • Lastly, before going back on a regular diet again, make sure you fully consume all the medications prescribed for you during your visit with the doctor because being exposed to mold can lead to different lung infections.


Maple syrup has been around for thousands of years, and people have been preserving it for food since before history began. The best way to prevent mold from growing on maple syrup is to keep it in a sealed container and keep it in the refrigerator.

Similar Posts