Maple syrup
Maple syrup is a sweet syrup made from the sap of maple trees. In cold climates these trees store starch in their trunks and roots before winter; the starch is then converted to sugar that rises in the sap in late winter and early spring. Maple trees are tapped by drilling holes into their trunks and collecting the sap, which is heated to evaporate much of the water, leaving the concentrated syrup.
Maple syrup was first made by the Indigenous people of Northeastern North America. The practice was adopted by European settlers, who gradually changed production methods. Technological improvements in the 1970s further refined syrup processing. Almost all of the world's maple syrup is produced in Canada and the United States.
Maple syrup is graded based on its colour and taste. Sucrose is the most prevalent sugar in maple syrup. In Canada syrups must be made exclusively from maple sap to qualify as maple syrup and must also be at least 66 per cent sugar. Maple syrup is often used as a condiment for pancakes, waffles, French toast, oatmeal or porridge. It is also used as an ingredient in baking and as a sweetener or flavouring agent.
History
Indigenous peoples
living in northeastern North America were the first groups known to have produced maple syrup and maple sugar. According to Indigenous oral traditions, as well as archaeological evidence, maple tree sap was being processed into syrup long before Europeans arrived in the region. There are no authenticated accounts of how maple syrup production and consumption began, but various legends exist; one of the most popular involves maple sap being used in place of water to cook venison served to a chief. Indigenous tribes developed rituals around syrup-making, celebrating the Sugar Moon with a Maple Dance. Many aboriginal dishes replaced the salt traditional in European cuisine with maple syrup.The Algonquians recognized maple sap as a source of energy and nutrition. At the beginning of the spring thaw, they made V-shaped incisions in tree trunks; they then inserted reeds or concave pieces of bark to run the sap into clay buckets or tightly woven birch-bark baskets. The maple sap was concentrated first by leaving it exposed to the low temperatures overnight and disposing of the layer of ice that formed on top. Following that, the sap was transported by sled to large fires where it was boiled in clay pots to produce maple syrup. Often, multiple pots were used in conjunction, with the liquid being transferred between them as it grew more concentrated. Contrary to popular belief, syrup was not typically produced by dropping heated stones into wooden bowls, especially in northeast North America where Indigenous cultures had been using clay pots for thousands of years. However, modern and historic sources contain evidence that hot stones may have occasionally been used in the upper Midwest and Canada, where hollowed out logs and birchbark containers typically replaced clay pots.
Colonists
In the early stages of European colonization in northeastern North America, local Indigenous peoples showed the arriving colonists how to tap the trunks of certain types of maples during the spring thaw to harvest the sap. André Thevet, the "Royal Cosmographer of France", wrote about Jacques Cartier drinking maple sap during his Canadian voyages. By 1680, European settlers and fur traders were involved in harvesting maple products. However, rather than making incisions in the bark, the Europeans used the method of drilling tapholes in the trunks with augers. Prior to the 19th century, processed maple sap was used primarily as a source of concentrated sugar, in both liquid and crystallized-solid form, as cane sugar had to be imported from the West Indies.Maple sugaring parties typically began to operate at the start of the spring thaw in regions of woodland with sufficiently large numbers of maples. Syrup makers first bored holes in the trunks, usually more than one hole per large tree; they then inserted wooden spouts into the holes and hung a wooden bucket from the protruding end of each spout to collect the sap. The buckets were commonly made by cutting cylindrical segments from a large tree trunk and then hollowing out each segment's core from one end of the cylinder, creating a seamless, watertight container. Sap filled the buckets, and was then either transferred to larger holding vessels, often mounted on sledges or wagons pulled by draft animals, or carried in buckets or other convenient containers. The sap-collection buckets were returned to the spouts mounted on the trees, and the process was repeated for as long as the flow of sap remained "sweet". The specific weather conditions of the thaw period were, and still are, critical in determining the length of the sugaring season. As the weather continues to warm, a maple tree's normal early spring biological process eventually alters the taste of the sap, making it unpalatable, perhaps due to an increase in amino acids.
The boiling process was very time-consuming. The harvested sap was transported back to the party's base camp, where it was then poured into large vessels and boiled down to achieve the desired concentration. The sap was usually transported using large barrels pulled by horses or oxen to a central collection point, where it was processed either over a fire built out in the open or inside a shelter built for that purpose.
Since 1850
Around the time of the American Civil War, syrup makers started using large, flat sheet metal pans as they were more efficient for boiling than heavy, rounded iron kettles, because of a greater surface area for evaporation. Around this time, cane sugar replaced maple sugar as the dominant sweetener in the US; as a result, producers focused marketing efforts on maple syrup. The first evaporator, used to heat and concentrate sap, was patented in 1858. In 1872 an evaporator was developed that featured two pans and a metal arch or firebox, which greatly decreased boiling time. Around 1900, producers bent the tin that formed the bottom of a pan into a series of flues, which increased the heated surface area of the pan and again decreased boiling time. Some producers also added a finishing pan, a separate batch evaporator, as a final stage in the evaporation process.Buckets began to be replaced with plastic bags, which allowed people to see at a distance how much sap had been collected. Syrup producers also began using tractors to haul vats of sap from the trees being tapped to the evaporator. Some producers adopted motor-powered tappers and metal tubing systems to convey sap from the tree to a central collection container, but these techniques were not widely used. Heating methods also diversified: modern producers use wood, oil, natural gas, propane, or steam to evaporate sap. Modern filtration methods were perfected to prevent contamination of the syrup.
A large number of technological changes took place during the 1970s. Plastic tubing systems that had been experimental since the early part of the century were perfected, allowing sap to flow directly from the tree to the evaporator house. Vacuum pumps were added to the tubing systems, and preheaters were developed to recycle heat lost in the steam. Producers developed reverse-osmosis machines to take a portion of water out of the sap before it was boiled, increasing processing efficiency.
Advancements have since been made in tubing and vacuum pumps, filtering techniques, high-efficiency preheaters, and storage containers. Ongoing research focuses on pest control and enhanced woodlot management. In 2009 researchers at the University of Vermont unveiled a new type of tap that prevents sap backflow into the tree, thereby reducing bacterial contamination and discouraging the tree from sealing the borehole. Experiments suggest that saplings could be used in plantations in place of mature trees, potentially boosting productivity per acre dramatically. Because saplings have smaller diameters, they require less extreme diurnal temperature changes to trigger freeze–thaw cycles. This enables sap production in warmer climates beyond northeastern North America.
Processing
Open pan evaporation methods have been streamlined since colonial days, but remain largely unchanged. Sap must first be collected and boiled down to obtain syrup. Maple syrup is made by boiling between 20 and 50 volumes of sap over an open fire until 1 volume of syrup is obtained, usually at a temperature 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. Defoamers are often added during boiling.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. The syrup is then filtered to remove precipitated "sugar sand", crystals made up largely of sugar and calcium malate. These 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. Smaller producers can also use batchwise recirculating reverse osmosis, with the most energy-efficient operation taking the sugar concentration to 25% prior to boiling.
The higher the sugar content of the sap, the smaller the volume of sap is needed to obtain the same amount of syrup. To yield 1 unit of syrup, sap at 1.5 per cent sugar content will require 57 units, while sap at 3.5 per cent sugar content only needs 25 units of sap. 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 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.