Editing Maple syrup (section)

===Since 1850===
[[File:Maple sugaring bucket (5571412972).jpg|thumb|right|A bucket used to collect sap, built {{circa|1820}}]]
Around the time of the [[American Civil War]] (1861–1865), 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.<ref name="production2"/> 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.<ref name="history"/> Around 1900, producers bent the tin that formed the bottom of a pan into a series of [[flue]]s, 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.<ref name="production2"/>

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 (the sugar bush) 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.<ref name="history"/> Heating methods also diversified: modern producers use wood, oil, natural gas, propane, or steam to evaporate sap.<ref name="production2"/> Modern filtration methods were perfected to prevent contamination of the syrup.<ref name="fgph">{{cite book |last1=Koelling |first1=Melvin R |editor1-first=Melvin R |editor1-last=Koelling |editor2-last=Heiligmann |editor2-first=Randall B |title=North American Maple Syrup Producers Manual |chapter-url=https://web.archive.org/web/20060701150215/http://ohioline.osu.edu/b856/index.html |year=1996 |publisher=Ohio State University |chapter=Chapter 8: Syrup Filtration, Grading, Packing, and Handling |display-authors=etal  }}</ref>

[[File:Sap plastic tubing.jpg|thumb|left|upright|Two taps in a maple tree, using plastic tubing for sap collection]]

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.{{sfn|Ciesla|2002|p=40}} [[Vacuum pump]]s 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.<ref name="history"/>

Improvements in tubing and vacuum pumps, new filtering techniques, "supercharged" preheaters, and better storage containers have since been developed. Research continues on pest control and improved woodlot management.<ref name="history"/> In 2009, researchers at the [[University of Vermont]] unveiled a new type of tap that prevents backflow of sap into the tree, reducing bacterial contamination and preventing the tree from attempting to heal the bore hole.<ref name="perkins">{{cite journal |last=Perkins |first=Timothy D |title=Development and testing of the check-valve spout adapter |journal=Maple Digest |date=October 2009 |volume=21A |pages=21–29 |url=http://www.uvm.edu/~pmrc/check-valve.pdf |accessdate=21 September 2010 |url-status=dead |archiveurl=https://web.archive.org/web/20101229072138/http://www.uvm.edu/~pmrc/check-valve.pdf |archivedate=29 December 2010 }}</ref> Experiments show that it may be possible to use saplings in a plantation instead of mature trees, dramatically boosting productivity per acre.<ref>{{cite news|last=Sorkin|first=Laura|title=Maple Syrup Revolution: A New Discovery Could Change the Business Forever|url=http://modernfarmer.com/2014/01/maple-syrup-revolution/|accessdate=20 January 2014|newspaper=[[Modern Farmer (magazine)|Modern Farmer]]|date=20 January 2014|url-status=live|archiveurl=https://web.archive.org/web/20140126065512/http://modernfarmer.com/2014/01/maple-syrup-revolution/|archivedate=26 January 2014}}</ref> As a result of the smaller tree diameter, milder diurnal temperature swings are needed for the tree to freeze and thaw, which enables sap production in milder climatic conditions outside of northeastern North America.<ref>{{Cite journal|last1=Reid|first1=Simon|last2=Driller|first2=Tenaya|last3=Watson|first3=Matthew|year=2020|title=A two-dimensional heat transfer model for predicting freeze-thaw events in sugar maple trees|journal=Agricultural and Forest Meteorology|volume=294|page=108139|doi=10.1016/j.agrformet.2020.108139|hdl=10092/101100|hdl-access=free}}</ref>