Why Does Syrup Crystallize?
Storing maple syrup in the open is a probable cause of crystallization. When syrup is exposed to air, it evaporates and crystallizes, creating lumps of sugar that are too hard to cook with.
What to Do
To melt the lumps of sugar and return them to a liquid state, place your container of maple syrup in a pot of simmering water. Add 1 to 2 tsp (5 to 10 ml) of water to the syrup container per 1 cup (250 ml) of syrup and heat gently. You can also do this step in the microwave.
How to Store Maple Syrup
If left unopened, a can of maple syrup will keep for several years. Once the can is open, transfer the syrup into an airtight container. Syrup can be kept in the fridge for 3 to 6 months and can also be frozen.