As long as it is sealed and kept at proper temperature, canned maple syrup can be preserved for several years. It can be kept at room temperature like any other canned good. Once opened, however, it is strongly recommended to transfer the maple syrup into a plastic or glass container and refrigerate it in order to slow down its evaporation process and ensure its conservation. Freezing is also an option if syrup is kept for an extended period.
Composition of maple syrup
All of this can be explained with the fact that maple syrup is defined by its sugar density, or 66 degrees Brix. At 66 degrees Brix, maple syrup is saturated in sugar, and if for one reason or another, its water evaporates, its sugar density increases. In fact, as soon as a can of maple syrup is opened, the evaporation process is triggered automatically, thus increasing the syrup’s sugar concentration and resulting in crystallization of the excess sugar.
Remember that light-coloured syrup, harvested in early season, is particularly susceptible to crystallization due to its high concentration of saccharose. Slightly darker syrup, on the other hand, contains more fructose and has a lesser tendency to crystallize due its lower dissolution rate. Saccharose is more sensitive to variations in degrees Brix.
Bottled maple syrup can be kept at room temperature. It can be preserved in the same conditions as canned syrup. It is not recommended, however, to expose the bottle to light, or to keep it in the freezer.
As long as the syrup is kept in an airtight container and at proper temperature, it is not necessary to freeze it. Once opened, in the fridge, the product can be kept for several months (between three to six months). In theory, maple syrup does not freeze, provided that it has the right Brix density (66%).
*A degree Brix is the weight in grams of dry matter contained in 100 grams of solution in distilled water.
Source: Quebec’s Federation of maple syrup producers www.siropderable.ca
Once a can is opened, pour the maple syrup in a glass container and refrigerate.
Mold at the surface of maple syrup can sometimes occur. These are nontoxic molds. Just drain through a filter, such as a cheese cloth, and boil the maple syrup for a few seconds. Pour in a glass bottle and refrigerate.