Making maple syrup is a time-honored tradition in many parts of Wisconsin, and it is as much of an art as a science. Even though sap does run in other trees such as birch and elm in early spring, maples produce more and sweeter sap than any other tree.

Collection. Once trees are tapped, a collecting container is placed at the site to catch the sap as it flows.  A major goal in maple production is to gather and process the sap as quickly as possible. To minimize microbial growth, particularly during warm periods, sap should normally spend no more than a few hours in the collecting container. Sap is collected in special metal buckets or, increasingly, via a plastic tubing system.

Evaporation. Once the sap is collected, it is boiled to remove water and concentrate the syrup.  During the evaporation process, sap is concentrated to the desired density and flavor, and color develops as a result of chemical reactions that occur during heating. The extent and character of the color and flavor are determined, in part, by the length of time the sap is boiled. The longer the sap is boiled, the darker it becomes and the stronger the flavor. Making light-colored syrup requires a short evaporation time. Anything that slows the evaporation process (uneven fire, weak fire, excessive sap depth in evaporator, etc.) will produce darker, usually stronger-flavored syrup. It may take 43 or more gallons of sap to produce one gallon of syrup!  There is a new International Grading System for Pure Maple Syrup; check it out as your guide to buying maple syrup anywhere in the world.

Bottling. Once maple sap has been processed into maple syrup and the correct density is obtained, the syrup is ready for filtering and packing. Syrup is best filtered while it is still hot (185° to 190°F) for rapid removal of sediment. To prevent contamination of finished syrup by yeast or mold growth, finished syrup should be hot packed. Syrup can be hot-packed into large drums or cans, or into retail/ home-sized containers. Regardless of the type of container, syrup should be packed into cleaned and sanitized containers. Small containers can be sanitized by boiling for 10 minutes in water. Because filling into any kind of container, sterilized or not, may cause contamination, containers hot-filled with syrup should be inverted immediately for 1-2 minutes after being hot-filled and sealed. Turn filled containers right-side-up to cool.

Storage. Pure maple syrup should be kept in a cool, dark place; for a quality product, be sure to use within 2 years. Refrigerate after opening. If excess water is present or if containers are not clean when filled, there may be the growth of bacteria, yeast or mold during storage. If spoilage develops, discard the product. For maximum flavor, bring maple syrup to room temperature or warm it before serving.

The North American Maple Syrup Producers Manual is available for purchase from Ohio State University. Other resources:

• How to Tap Maple Trees and Make Maple Syrup (University of Maine)
• Maple Syrup Best Management Practices (University of Massachusetts)
• Focus on Food Safety When Making Maple Syrup (University of Wisconsin)
• International Grade Standards for Maple Syrup (handout)

Enjoy! And stay food-safe. Barb