Maple Syrup Production Process

From Sap to Sugar

Fresh sap flowing out of the maple tree contains anywhere from 1% to 6% sugar. After the process of evaporation, maple syrup is 66–67% sugar. This transformation involves the removal of water, but also the caramelization of sugars. The process of evaporation is carried out by boiling the sap until its sugar reaches the correct concentration. Too little and the syrup can referment; too much and it may crystallize. It can take as many as 40 litres of sap to produce 1 litre of syrup.  

Evaporation

Sap is generally concentrated in one of two ways. Traditionally, sap was boiled for many hours until it achieved the right concentration. Large pans called arches were once exclusively fired with wood; newer arches are fired with oil, electricity, or pelletized wood, though wood-fired arches still exist. The arches are designed to allow sap (or concentrated sap) to flow slowly into the pan while thicker, partially evaporated sap flows towards the front. From here the concentrated sap flows into a finishing pan fired at a lower temperature for the delicate and sometimes precarious final stages of syrup production.  

Modern technologies have also been applied to the production of syrup. One technology that offers enormous cost and energy savings is the reverse osmosis system. Using pressure, this system forces sap through a membrane that is only permeable to water, thereby increasing the sugar content of the remaining sap and concentrating its other components. The resulting concentrate must still be processed in a heated evaporator to obtain the characteristic maple flavour by caramelizing the sugars. Reverse osmosis will concentrate sap originally at 2% sugar to between 8% and 16% sugar, and remove half of the initial water. A recent development in osmosis technology can now concentrate sugars to 35%.

Caramelization

The sugar in maple sap is almost entirely polysacharide sucrose. When heat is applied in the evaporation process, this sucrose is broken down into the monosacharides glucose and fructose, which caramelize at a lower temperature. The caramelization of these sugars, as well as the contribution of flavour development during the Maillard reaction, changes the flavours of the syrup as it concentrates. These are all non-enzymatic changes.

Filtration

Once maple syrup is produced, it must be filtered. Failure to undertake this final step will yield a poor-quality, bitter, and sandy syrup. The industry standard for filtration has become the filterpress; diatomaceous earth is added to the hot syrup prior to filtration, and then the syrup is pressed through a series of cast plates with filter paper. As the syrup passes through the paper, the diatomaceous earth builds up to create a filtration matrix that removes the insoluble solids from the syrup. These insoluble solids, commonly referred to as sugar sand, are mostly the concentrated minerals naturally found in sap. Consisting largely of calcium, potassium, magnesium, manganese, and zinc, the sugar sand is inedible but harmless – and very good for your garden in calculated doses!