More precisely where are you storing this year’s bumper crop? If you have not sold all of this year’s maple syrup and have some left in the sugarhouse or in a tool shed you need to watch the inside temperatures of those buildings. With all of the recent hot weather syrup stored in outside non- insulated structures can elevate in temperatures quickly and spoilage can occur. You may have thought that you covered the entire basis by packing the syrup hot in a sealed container. Maybe not!
Let’s look at how syrup is packed and stored. Most syrup is stored in stainless steel barrels that were packed in February and March. The syrup went in to barrels hot and was sealed. A thirty gallon drum is a hard vessel to pack there is always room for air. They very seldom are packed without a small amount of air space. The drums then cool to the temperature of the time of the year. Eventually over time the syrup inside the drums takes on the same temperature as the outside temperature. Steel transfers heat and cold well. The syrup on the inside of the barrel will remain cold for a long period of time due to its viscosity and mass. The steel in the outside drum will heat up quickly when outside ambient temperature gets above 80 and stays warm. The result is the buildup of condensation between the warm steel and the cool syrup on the inside. When this moisture gets into the air space molds can form. This is the same thing that happens to jugs when they are not heated to 185 degrees F. If the product is not above 66 brix the syrup can even ferment.
The best solution if you are not sitting on thousands of gallons is to build a cool room. You notice I did say cool, not cold. A walk in cooler would be the best case scenario but most producers cannot afford such a luxury. Take a small space big enough to hold several drums of syrup. This could be a closet or small room in a building. Insulate the room and stick a window air conditioning unit through the wall. When temperature gets above 80 deg. F for any length of time, fire up the air conditioner and brings the room to just below 70 deg. F. At that temperature the syrup will stays relatively cool in the barrels. It always seems to be colder than the outside temperature. You only have to get the syrup through the hot months, once the daytime temperatures cool off you are out of the woods.
Geauga County OSU Extension