Does Maple Syrup Go Bad? Here’s What to Know

Chances are you may have never considered how long maple syrup lasts—or whether it can spoil. After all, it’s a staple item we rely on and reach for, time and again. But, as it turns out, this versatile ingredient, which makes everything from breakfast pancakes and cheesecake to root vegetablestaste phenomenal, can occasionally go south if not stored correctly. We tapped a food scientist and maple syrup expert to learn more about the best ways to store syrup and sidestep any mishaps.

The Right Way to Store Maple Syrup

There’s nothing complicated about proper maple syrup storage, but the preferred methods differ for opened and unopened bottles.

Unopened Containers

“An unopened bottle of pure maple syrup is generally shelf-stable, primarily due to its high sugar concentration and low water activity,” says Bryan Quoc Le, Ph.D, food scientist, founder, and principal food consultant of Mendocino Food Consulting. Unopened syrup should be kept in a dry, cool, dark pantry or cabinet, away from direct sunlight, for long-term storage, he suggests.

“If you have the space, the freezer is the perfect place to store unopened containers of maple syrup,” Allison Hope, executive director, Vermont Maple Sugar Makers’ Association (VMSMA), adds. An unopened container can last indefinitely if stored correctly, but its best quality is between one and two years, Le says.

The container may also play a role. Maple syrup packaged in plastic darkens in color and tastes more muted over longer periods of time, Hope says, while glass containers protect the product from oxygen, rendering its flavor and taste intact. “Either way, maple is a great storage crop,” she says.

Opened Containers

Whether it takes one month or six to get to the last drop of syrup in the container, it’s essential to store it in the refrigerator or freezer once it has been opened. Screw the cap on tightly, too, to prevent crystallization.

“It is important to note that the stability of an unopened bottle of maple syrup stored in a simple cupboard is very different from that of an opened bottle left at room temperature, which is much more prone to spoilage,” Le says. (Don’t let it linger on the kitchen table.)

Storing in the Fridge or Freezer

Refrigeration slows down the chance of microbial or mold growth, Le says, while freezing extends its shelf life without ruining the syrup’s flavor and texture. Opened containers, if refrigerated, will typically maintain a good quality for 6-12 months; frozen, they can last for several years, he says. 

For daily use, the fridge is more convenient, Hope notes. “In the fridge, you’ll most likely use it up before you notice any concerns with color or flavor,” she says.

If you buy a large container (the most economical choice in terms of price point per ounce), you can toggle between the two. “In that case, choose the larger container and then repack it into clean containers (mason jars work well here) and put those in the fridge or freezer,” she says.

What Type of Maple Syrup Lasts Longest?

Whether golden or amber, the syrup’s color doesn’t impact the product’s longevity—though Le says that darker colors may cover minor changes in flavor for a longer period. “All grades of pure maple syrup are extremely shelf-stable, and our advice on storage applies to each of them equally,” Hope says. “Each grade sold in retail containers is considered ‘Grade A’ and has to be processed and packaged in the same manner.”

How to Know If Maple Syrup Has Spoiled

Maple syrup brings richness to countless dishes, but there may be instances when this standby becomes tainted. Here’s what to look for:

Mold

One of the most common indicators of spoilage is mold, characterized by a green or whitish film or slime that develops on top of the syrup, says Le. 

“Although maple syrup contains a lot of sugars that help naturally inhibit bacterial growth, it is also the main culprit for mold spoilage if stored incorrectly,” Le says. Once a container is opened, he adds, its exposure to air (possibly containing mold spores), moisture, and temperature fluctuations could cause some strains of mold or yeast to grow.

Aroma

There are other clues, too. An off smell, meaning a sour, musty, or even chocolatey smell, can also signal spoilage, Le says.

Flavor

Flavor is also central to the situation. “If it tastes noticeably different from your usual maple syrup and has become unusually thick or slimy in texture, then it has most likely gone bad. Once you’ve noticed any of these signs, it should be immediately discarded,” he says.

Producer Issues

Improper storage is likely behind the blight, but there may be other circumstances at work. “Storing syrup incorrectly can lead to mold or off flavors; those issues can also occur if a maple producer hasn’t followed best practices or has had an undetected production issue,” Hope says. 

Maple producers make high-quality, food-safe products, but if your syrup isn’t up to snuff, contact the producer directly to resolve, she suggests.