Open pan evaporation methods have been streamlined since colonial days, but remain basically unchanged. Sap must first be collected and boiled down to obtain pure syrup without chemical agents or preservatives. Maple syrup is made by boiling between 20 and 50 volumes of sap (depending on its concentration) over an open fire until 1 volume of syrup is obtained, usually at a temperature 4.1 °C (7.4 °F) over the boiling point of water. As the boiling point of water varies with changes in air pressure the correct value for pure water is determined at the place where the syrup is being produced, each time evaporation is begun and periodically throughout the day. Syrup can be boiled entirely over one heat source or can be drawn off into smaller batches and boiled at a more controlled temperature.
Boiling the syrup is a tightly controlled process, which ensures appropriate sugar content. Syrup boiled too long will eventually crystallize, whereas under-boiled syrup will be watery, and will quickly spoil. The finished syrup has a density of 66° on the Brix scale (a hydrometricscale used to measure sugar solutions). The syrup is then filtered to remove sugar sand, crystals made up largely of sugar and calcium malate. crystals are not toxic, but create a “gritty” texture in the syrup if not filtered out.
In addition to open pan evaporation methods, many large producers use the more fuel efficient reverse osmosis procedure to separate the water from the sap. The higher the sugar content of the sap, the fewer the gallons of sap are needed to obtain one gallon of syrup. 57 gallons of sap with 1.5% sugar content will yield 1 gallon of syrup, but only 25 gallons of sap with a 3.5% sugar content are needed to obtain one gallon of syrup. The sap’s sugar content is highly variable and will fluctuate even within the same tree.
The filtered syrup is graded and packaged while still hot, usually at a temperature of 82 °C (180 °F) or greater. The containers are turned over after being sealed to sterilize the cap with the hot syrup. Packages can be made of metal, glass, or coated plastic, depending on volume and target market. The syrup can also be heated longer and further processed to create a variety of other maple products, including maple sugar, maple butter or cream, and maple candy or taffy.
This article uses material from the Wikipedia article Maple Syrup, which is released under the Creative Commons Attribution-ShareAlike 3.0 Unported License