Can syrup go bad? (+3 types of syrups)

In this article, we will answer the question “Can syrup go bad?”, and how long does syrup last?

Can syrup go bad?

No, technically syrup can not go bad. You can keep the unopened bottle of syrup for a long time after the expiration date. Its quality can degrade with time and the taste may also change, but if stored right it will not go bad.

The low moisture and high sugar content of syrup do not favor the growth of any microbe. Maple syrup might develop mold If It is left open. However, this mold is not pathogenic or spoilage. 

This mold can be easily skimmed off from the top to consume the rest of the syrup. But first, boil the syrup to heat kill the remaining spores of the fungus. Cool the boiled syrup and you are good to go. 

Similarly, pancake syrup that is flavored corn syrup, does not go bad either. It has an indefinite shelf-life at room temperature. 

How long doe syrup last?

(Opened/Unopened)In the pantry In the fridge 
Pure maple syrup Indefinite
Pancake syrup Indefinite 
Corn syrup Indefinite

Food safety in the syrup making process 

Watery maple sap is devoid of any microbe while It is in the tree. This sterile sap is pumped through plastic piping into the holding tanks. The piping and the collection tanks for maple syrup are sanitized after each sugaring session. 

The industry heats this syrup to boiling temperatures until It thickens and is safe for consumption. Typically, the syrup is heated to about 219°F. Then the syrup is filtered, bottled, and undergoes another heating process. 

The second heating session sanitized the syrup bottles. The temperature during this session goes up to 180°F

What type of maple syrup can go bad?

Pure maple syrup that has not been exposed to the processing temperatures and conditions, can go bad. 

The shelf-life of pure maple syrup is only 1 year in the pantry. It can last a year in the fridge If It is opened but indefinitely in the freezer.

How to store maple syrup?

Maple syrup must be refrigerated after opening. If you notice any mold growth, you can scoop it out and boil the rest of the syrup to ensure safety. After billing, the syrup must be kept in the fridge. 

An unopened bottle of maple syrup should sit in a cool, dark, and dry place away from heat sources like direct sunlight and the stovetop.

How to tell If your maple syrup has spoiled?

Though the best-by date is a loose indicator of safety, you must keep track of it to get a rough estimation of the shelf-life of the syrup. Mold belonging to the class wallemiomycetes is common in syrup. 

If you see mold floating over your refrigerated or frozen maple syrup, you can just skim it off and boil the syrup. If the syrup developed mold after being exposed to extreme temperatures, you better throw it out and get a new bottle.

Off flavors, haze, and crystals 

The off-flavors in your maple syrup might smell like peanut butter, popcorn, even cardboard flavors. 

The sediment at the bottom of the syrup bottle or the haziness in its appearance tells us that the syrup was no filtered and processed. The particles in the sediment are minerals of the sap. 

If the maple syrup starts to develop crystals, It is because water is evaporating from it at a faster pace. The moisture is evaporating from the syrup every time your microwave it. 

This makes the sugar more concentrated. These sugar crystals are not harmful. They can be dissolved back in by adding a splash of water to the syrup and heating it in a hot water bath.

Sugar as a preservative 

Microbes need water to grow more than they do sugar. When sugar binds to water molecules in syrup, it renders this water unavailable for microbial growth. 

Besides, syrup undergoes boiling during which the moisture content of the syrup is significantly reduced. All these factors make it impossible for microbes to multiply in a syrup. 

However, when the syrup is left open, it starts to attract moisture from the environment. This moisture or free water collects at the surface of the syrup and promotes the growth of fungus. That is why the syrup must be tightly sealed after each use.

Other FAQs about Syrup which you may be interested in.

Can you substitute syrup for honey?

Types of syrup 


Molasses is the liquid that remains after sugar crystallizes from the sugar cane juice. The light-colored and flavored molasses is used in baking, candy-making, and rum production. Blackstrap molasses is used in cattle feed.


Honey is collected from beehives. The flavor varies with the flower source. It is used in beverage making and baking.

Corn syrup 

It is the most widely used sweetener in processed products like soft drinks, ketchup, ice cream. This syrup is sweeter and economical than sucrose.


In this article, we answered the question “Can syrup go bad?”, and how long does syrup last?