Editing Maple syrup (section)

== Processing ==

[[File:Maple sap collecting at Bowdoin Park, New York.JPG|thumb|left|Traditional bucket tap and a plastic-bag tap]]
Open pan evaporation methods have been streamlined since colonial days, but remain basically 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 (depending on its concentration) over an open fire until 1 volume of syrup is obtained, usually at a temperature {{convert|4.1|°C-change|sigfig=2}} 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.<ref name="production2"/>{{sfn|Eagleson|Hasner|2006|p=55}} Syrup can be boiled entirely over one heat source or can be drawn off into smaller batches and boiled at a more controlled temperature.{{sfn|Eagleson|Hasner|2006|p=53}} [[Defoamer]]s are often added during boiling.<ref>{{cite journal|first1=Abby |last1=van den Berg|first2=Timothy |last2= Perkins|title=Identifying an Effective Defoamer for Certified Organic Maple Production|journal=Maple Syrup Digest|date= February 2020|page= 8}}</ref>

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#|Brix scale]] (a [[hydrometer|hydrometric]] scale used to measure sugar solutions).{{sfn|Elliot|2006|p=12}} The syrup is then filtered to remove precipitated "sugar sand", crystals made up largely of sugar and [[calcium malate]].<ref name=ball/> These crystals are not toxic, but create a "gritty" texture in the syrup if not filtered out.{{sfn|Eagleson|Hasner|2006|p=56}}

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.<ref name="ThomasSchumann1993">{{cite book|last1=Thomas|first1=Margaret G.|last2=Schumann|first2=David R.|title=Income Opportunities in Special Forest Products: Self-help Suggestions for Rural Entrepreneurs|url=https://books.google.com/books?id=4FsDVbhiskkC&pg=PA181|year=1993|publisher=USDA Forest Products Laboratory|isbn=978-0-7881-1236-2|page=181}}</ref> Smaller producers can also use batchwise recirculating [[reverse osmosis]], with the most energy-efficient operation taking the sugar concentration to 25% prior to boiling.<ref>{{Cite journal|date=2020-05-01|title=Minimizing the energy requirements for the production of maple syrup|journal=Journal of Food Engineering|volume=273|page=109823|doi=10.1016/j.jfoodeng.2019.109823|last1=Weaver|first1=Nicholas J.|last2=Wilkin|first2=Geoffrey S.|last3=Morison|first3=Ken R.|last4=Watson|first4=Matthew J.|doi-access=free}}</ref>

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.<ref name="Wagner2011">{{cite book|last=Wagner|first=John E.|title=Forestry Economics: A Managerial Approach|url=https://books.google.com/books?id=jdSoAgAAQBAJ&pg=PT74|year=2012|publisher=Routledge|isbn=9780415774406|page=74}}</ref> The sap's sugar content is highly variable and will fluctuate even within the same tree.<ref name="Taylor1956">{{cite journal|last1=Taylor|first1=Fred H.|title=Variation in Sugar Content of Maple Sap|journal=AGRICULTURAL EXPERIMENT STATION, University of Vermont and State Agricultural College|date=March 1956|volume=Bulletin 587|url=https://www.uvm.edu/~uvmaple/sapsugarcontentvariation.pdf|url-status=live|archiveurl=https://web.archive.org/web/20160417153652/http://www.uvm.edu/~uvmaple/sapsugarcontentvariation.pdf|archivedate=17 April 2016 }}</ref>

The filtered syrup is graded and packaged while still hot, usually at a temperature of {{convert|82|°C|°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.{{sfn|Eagleson|Hasner|2006|p=59}} The syrup can also be heated longer and further processed to create a variety of other maple products, including [[maple sugar]], [[maple butter|maple butter or cream]], and [[maple taffy|maple candy or taffy]].{{sfn|Eagleson|Hasner|2006|pp=65–67}}

[[File:MapleSyrupDrop.ogv|thumb|upright|Maple sap harvesting]]

=== Off-flavours ===

[[Off-flavours]] can sometimes develop during the production of maple syrup, resulting from contaminants in the boiling apparatus (such as [[disinfectant]]s), [[microorganisms]], [[fermentation (food)|fermentation]] products, [[metal]]lic can flavours, and "buddy sap", an off-flavour occurring late in the syrup season when tree [[budding]] has begun.<ref name="ume">{{cite web|url=https://extension.umaine.edu/publications/7038e/|title=Maple Syrup Quality Control Manual|publisher=Cooperative Extension Publications, University of Maine|author=Hopkins, Kathy|date=2016|accessdate=20 May 2017|url-status=dead|archiveurl=https://web.archive.org/web/20170829091048/https://extension.umaine.edu/publications/7038e/|archivedate=29 August 2017}}</ref><ref>{{cite journal|last1=Camara|first1= M|last2=Cournoyer|first2= M|last3=Sadiki|first3=M|last4= Martin|first4=N|year=2019|title= Characterization and Removal of Buddy Off‐Flavor in Maple Syrup|journal= Journal of Food Science|volume= 84|issue= 6|pages= 1538&ndash;1546|doi=10.1111/1750-3841.14618|pmid= 31120572}}</ref> In some circumstances, it is possible to remove off-flavours through processing.<ref name=ume/><ref name="berg">{{Cite journal |last=van den Berg |first=Abby K |author2=Perkins, Timothy D |author3=Isselhardt, Mark L |author4=Godshall, Mary An |author5= Lloyd, Steven W  |title=Metabolism Off-Flavor in Maple Syrup |journal=Maple Digest |date=October 2009 |volume=21A |pages=11–18}}</ref>