One litre of maple syrup starts as 20 to 50 litres of sap
A maple tree gives only about seven percent of its sap in a season, and that sap is mostly water, around two to five percent sugar. Producers boil away the rest until the liquid runs just over four degrees hotter than boiling water. Quebec alone makes 72 percent of the world's supply.
Maples in cold climates store starch in their trunks and roots over winter. As spring approaches, that starch turns to sugar and rises with the sap, flowing on days when the temperature climbs above freezing. Sugar, black and red maples are the main sources because their sap is especially sweet, though red maples bud early, which shortens their season and changes the flavour. Once the weather warms further, the sap turns unpalatable, possibly from rising amino acids, and the harvest is over, typically after four to eight weeks.
Indigenous peoples of northeastern North America made syrup long before Europeans arrived, celebrating the first full moon of spring, the Sugar Moon, with a Maple Dance. Algonquians cut V-shaped notches in trunks, let sap freeze overnight and skimmed off the ice to concentrate it, then boiled it in clay pots. The popular idea that they dropped hot stones into wooden bowls is mostly a myth in the northeast. Settlers learned the craft, drilled holes with augers instead, and until the 19th century valued maple mainly as sugar, since cane sugar had to come from the West Indies.
Equipment kept improving. Flat sheet-metal pans replaced iron kettles around the Civil War era, the first evaporator was patented in 1858, and folded pan bottoms around 1900 sped boiling further. The 1970s brought plastic tubing that carries sap straight to the sugarhouse, vacuum pumps, heat-recycling preheaters and reverse-osmosis machines that strip out water before boiling. In 2009 University of Vermont researchers introduced a tap that stops sap flowing back into the tree.
Trees are usually first tapped at 30 to 40 years old and can keep yielding past 100, producing 35 to 50 litres a season. Canada requires syrup to be pure maple and at least 66 percent sugar. Warming winters are now shifting the season earlier and reducing sugar content.
Source: Maple syrup
