After the sap has trickled out of the tree and into the bucket, the water in the sap must be evaporated out. To do this, the maple sugar and syrup producer pours the liquid into large metal containers which are set over a fire. Wood or oil is used to move the evaporation process along. Traditionally, the heating took place in a "sugar shack" or "maple house"; commercial processors have larger, more efficient operations, with patented evaporators.
Natural sap is clear, and the color and to an extent flavor of a sap is the result of the heating process, the sugar content, the pH, and the chemical makeup of the saps which varies over region.
After evaporation of the water is complete, the sap is filtered, to remove any solids and generate a clear syrup. Often small operations do most of the concentration in the maple groves and finish the last boil at home. Commercial operations use a pressure filter; smaller productions use wool or a synthetic fiber cone. Commercial manufacturers pack the final product into 30-50 gallon stainless steel drums which are shipped for packaging into retail containers.
It takes approximately 40 gallons of natural sap to produce one gallon of syrup. Today, annual syrup production is about 8-9 million gallons, about 85% of which is produced in Canada.
Sources
Perkins TD, and van den Berg AK. 2009. Chapter 4 Maple Syrup--Production, Composition, Chemistry, and Sensory Characteristics. In: Steve LT, editor. Advances In Food And Nutrition Research: Academic Press. p 101-143. (main source)
A bibliography of Maple Sugaring sources has been collected for this project.
