Does syrup go bad? (+3 Ways to tell)

In this article, we will answer the question “Does syrup go bad?”, and how to tell If Maple syrup is bad?

Does syrup go bad?

Yes, maple syrup can go bad. It may be caused by physical contaminants like minerals, wood chips, dust, or ash or due to microbes like yeast and fungi. Maple syrup doesn’t expire. If stored correctly, all maple syrup can be stored in the pantry for about a year.. 

Maple syrup is produced by concentrating the xylem sap of the Acer saccharum, or sugar maple tree. Sap is considered a sterile liquid when inside the tree xylem, however, upon environmental exposure, it becomes highly susceptible to microbial inhibition. 

This contamination is amplified because of environmental changes (as sap flow is very weather dependent), improper sap storage conditions, or unsanitary processing practices are used.

 Often, these conditions can lead to several forms of defective sap, which subsequently result in a lower quality syrup. (1)

Fungi can contaminate syrup at any °Brix  (Degrees Brix is a measure of the dissolved solids in a liquid, and is commonly used to measure dissolved sugar content of an aqueous solution).

However, it is generally believed by maple syrup producers that syrup contamination occurs only if it is packed at a  density lower than 66.0 °Brix, thus in lower °Brix there is more water available for microbial development .

Bacterial or fungal contamination resulting from non-sterilization of the container may affect the syrup chemistry, interfering with the syrup color and/or flavor and causing possible toxicity due to mycotoxins. (2)

How to store maple syrup?

After purchase an unopened bottle of maple syrup can be stored in a dry, dark, and cool area away from heat sources like sunlight and stovetop but refrigerating the syrup even if unopened is recommended

After opening the bottle, you need to make sure It is tightly sealed and refrigerated at all times, i because natural maple syrup does not have added preservatives.(2)

Can the syrup change during storage and still be safe to consume?

Yes, syrup can change during storage and still be safe to consume. When stored in plastic, the syrup will darken over time due to oxygen permeating through the plastic causing oxidation.

Bacterial or fungal contamination resulting from non-sterilization of the container may affect the chemical composition of the syrup, causing  the syrup color and/or flavor change before spoilage.(1, 2)

Reheating syrup to a temperature of 93°C will achieve the desired degree of sterility, assuming that syrup will cool during dispensing into containers.(2)

What is the shelf-life of syrup?

Before opening, all maple syrup can be stored in the pantry for about a year. After opening, genuine maple syrup should be stored in the refrigerator and will last about a year. Opened jugs of imitation maple syrup can be stored in the pantry for about a year.(3)

How to tell If maple syrup is bad?

The signs indicating that maple syrup is bad are mold growth, bad odor and bad taste. 

Mold growth 

In addition to deviations in syrup grade due to microbial sap spoilage, a visible fungal mat on the surface of the syrup is an obvious product defect. 

Despite the notable thermal tolerance of mold spores, it is assumed that the extensive evaporation process used in producing finished syrup is adequate in eradicating fungal contaminants. 

Therefore, presence of any mold in maple syrup is likely the result of improper sanitation, low bottle filling temperature, or absence of good manufacturing practices (1)


You can quickly judge the syrup for freshness by giving it a sniff. If there is something off about it, get rid of the maple syrup. It might give off a sour or yeasty smell.


If the syrup does not taste as It should, you can discard It for quality reasons.

What are the risks of consuming spoiled maple syrup?

Consuming moldy maple syrup can cause food poisoning and other health issues.Indications of food poisoning may include a headache, vomit, stomachache, and/or diarrhea. 

In addition, one may experience a loss of appetite and nausea. Typically, these symptoms should subside within a day or two. If they persist beyond this timeframe, seeking medical attention is advised. 

Any signs of spoilage such as a strange smell or discoloration should be a sign that the syrup has gone bad and should not be used. If the syrup is moldy, it should be discarded immediately. (4, 5)

Other FAQs about Syrup which you may be interested in.

Can syrup go bad?

Does corn syrup go bad?


In this article, we answered the question “Does syrup go bad?”, and how to tell If Maple syrup is bad?


  1. Perry Jennifer J. A Comprehensive Review of Maple Sap Microbiota and Its Effect on Maple Syrup Quality. Food Reviews International 38, 2022.
  2. Mary Lynn Whalen and Maria Franca Morselli. Fungi Associated with Pure Maple Syrup Packed at the Minimum Recommended Reheating Temperature. Journal of Food Protection,47, 688-689, 1984.
  3. U.S. Department of Agriculture. Website. Washington, DC. How long can you keep maple syrup?.
  4. BM Lund, SJ O’Brien, Public Health Measures: Food Safety in Hospitals and Other Healthcare Settings, Encyclopedia of Food Safety, Academic Press, 2014, 140-148.
  5. Food Safety

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