Maple syrup is made from the circulating fluid, or sap, of sugar maple trees. There are several different grades of maple syrup characterised by colour, although classification can vary between countries, it is useful to know the darker syrups are made from sap extracted later in the harvest season, often have a stronger maple flavour and are usually used for baking, wile the lighter hued ones are used to drizzle directly atop foods like pancakes.

I speak from experience when I say that even the biggest maple syrup lover will hardly ever be able to use a whole container all at once. When unopened, pure maple syrup has a long shelf life. But once it’s opened, the exposure to oxygen means that your syrup will start to deteriorate.

So what do you do with the rest of an open container? well there are two simple rules for keeping maple syrup fresh and mould-free once it’s open. First, avoid prolonged open-air exposure. Second, keep it in an airtight container in the refrigerator.

The three main enemies of maple syrup are air, time, and temperature. Even if the container hasn’t been opened, it is best to place your maple syrup in the refrigerator immediately after purchase. Maple syrup that comes in a tin or glass container can be stored for up to one year in the refrigerator in its original container. But because plastics tend to breathe, it is best to repack an unopened or opened plastic syrup bottle into a glass jar if you plan to store it for more than three months.

If excess water is present, or if the container is not sterile when filled, bacteria, yeast, or mould may grow during storage. Do not remove the mould and restore the product as some microorganisms produce toxins as they grow, and these toxins could make you sick, so if there is mould in your maple syrup, err on the side of caution and discard it.

When buying maple syrup, make sure you read the label carefully. This way, you’ll get real maple syrup and not just maple-flavoured syrup, which is often just refined sugar or high-fructose corn syrup with maple flavouring.