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All About Maple

Special thanks to the Cornell Sugar Maple Research & Extension Program for the information provided in our Maple Facts section

How much sap does a single tree produce in one year, on average?
The volume of sap produced during one season varies from 10-20 gallons

per tap, depending on the tree, weather conditions, length of the sap season, and method of collecting sap. Producers using gravity lines or buckets generally get 10-14 gallons of sap per forest-grown tree. Using buckets on roadside trees or using vacuum tubing yields 15-20 gallons per tap. A single tree can have one, two, or three taps, depending on size and health.

How many taps should you have on a maple tree?

A healthy tree 10-17 inches in diameter (31-53 inch circumference) should have no more than one tap. A tree 18-24 inches in diameter (57-75 inch circumference) should have no more than two taps. A tree larger than 25 inches in diameter (79-inch circumference) should have no more than three taps. 


Is the sap of different maples (for example, sugar, red, Norway) different?
The sugar content of sugar maple sap is higher than the sap of other maples. Sugar maple also produces syrup with the most pleasing flavor. Once buds develop on the trees in the spring, syrup develops an unpleasant "buddy" flavor. Sugar maple has the longest period of sap flow before buds develop. 


Where does the sugar come from?
Sugar is produced in the leaves during photosynthesis. It is transported into the wood and stored during the winter, mostly in the form of carbohydrates. It is then converted to sucrose and dissolved in the


What makes the sap rise?
During warm periods when temperatures rise above freezing, pressure develops in the tree. This pressure causes the sap to flow out of the tree through a wound or tap hole. During cooler periods when temperatures fall below freezing, suction develops, drawing water into the tree. This replenishes the sap in the tree, allowing it to flow again during the next warm period.

Sap flows through a portion of the outer tree trunk called sapwood. Sapwood consists of actively growing cells that conduct water and nutrients (sap) from the roots to the branches of the tree. During the day, activity in the cells of sapwood produces carbon dioxide. This carbon dioxide is released to the intercellular spaces in the sapwood. In addition, carbon dioxide that was dissolved in the cool sap is released into the spaces between the cells. Both of these sources of carbon dioxide cause pressure to build up in the cells. A third source of pressure is called osmotic pressure, which is caused by the presence of sugar and other substances dissolved in the sap. When the tree is wounded, as when it is tapped by a maple producer, the pressure forces the sap out of the tree. At night or during other times when temperatures go below freezing, the carbon dioxide cools and therefore contracts. Some of the carbon dioxide also becomes dissolved in the cooled sap. Finally, some of the sap freezes. All three of these factors create suction in the tree. This causes water from the soil to be drawn up into the roots and travel up through the sapwood. When temperatures rise above freezing the next day, sap flow begins again.  Once temperatures no longer fluctuate between freezing at night and thawing during the day, sap stops flowing. 


How many gallons of sap does it take to make one gallon of syrup?

This will vary depending on sugar content of the sap. The "Rule of 86" is used to calculate the gallons of sap needed to produce one gallon of syrup. It states that the number of gallons of sap you need to produce one gallon of syrup is equal to 86 divided by the percent sugar.


Rule of 86 Gallons of sap to produce one gallon of syrup = 86 / % sugar content in sap.

For example, you would need 43 gallons of sap with 2% sugar content to produce one gallon of syrup.


Why is maple syrup different colors?
The color in maple syrup results from a browning reaction that occurs during the latter stages of evaporation. Sap that is boiled longer makes a darker colored syrup. Therefore, anything that slows the evaporation process, such as uneven or weak fire, an inefficient evaporator, or too much sap in the evaporator, will cause dark syrup. Because color develops during the latter stages of boiling sap, it is particularly important to reduce processing time as the sap approaches syrup. Microorganisms in sap can also cause darkening. Sap flowing into the sap house can be treated with UV light to kill the microorganisms. Sap should be processed as soon as possible after collection to reduce the potential for microorganisms and thus reduce the quality of syrup produced.

Syrup may also darken during storage. To prevent darkening, hot syrup that has just been put into containers should be allowed to cool before the containers are packed close together. Gas exchange during storage can also cause syrup to darken.

During the maple production season, the trees themselves undergo metabolic and chemical changes as they go from winter dormancy to springtime activity. These changes cause differences in maple syrup flavor as the season progresses.  As a general rule the syrup produced early in the season will be light amber and progressively get darker.  However, sometimes even the earliest runs will produce medium or dark amber syrup.


What process causes sap to become syrup?

During evaporation, sap is concentrated to the desired sugar content and the distinctive maple color and flavor also develop. Chemical changes that occur during heating cause the color and flavor to develop.

Boiling time and microorganisms in the sap cause syrup to darken. Reducing boiling time and killing microorganisms through UV treatment can help to produce lighter colored syrup.

The development of flavors is not well understood, but it is thought that amino acids in the sap play an important role.The higher the sugar concentration of the sap, the less water that needs to be removed to make syrup. Each time you double the sap sugar concentration, you cut in half the amount of water that needs to be removed and the boiling time. For example, sap with 4% sugar requires half the boiling time of sap with 2% sugar to produce syrup.

What is the difference in syrup grades?

Maple syrup must meet exacting standards for purity. High quality pure maple syrup can be made only by the evaporation of pure maple sap, and by weight may contain no less than 66 percent sugar (Brix). In Vermont and New Hampshire the minimum sugar content is 66.9%. Maple syrup is classified according to its color, which is a rough guide to flavor intensity. The darker the syrup, the stronger the flavors. 

  • New York Grade A Light Amber or Vermont Fancy — the lightest of the three classifications has a mild, delicate flavor

  • Medium Amber — a bit darker with a fuller flavor

  • Dark Amber — the darkest of the three grades has a stronger maple, caramel, and other flavors

  • Grade B — has the strongest flavors


Does syrup quality vary from one region or state to another?  

Syrup flavor is affected by soil type, tree genetics, weather conditions during the maple season, time during the season when the sap is collected, and processing technique. Producers in every region consistently are able to produce good tasting, high quality products, but no region is always better than another. Pure maple is a natural product with considerable variation in flavors. Like wines, this variation should be sampled and enjoyed.


What is the shelf life for maple products?                         

The shelf-life for maple syrup in a properly filled and sealed container is over one year. The shelf-life for maple syrup after initial opening is about six months in the refrigerator. The shelf-life for un-coated maple candy is about two weeks on the shelf or in the refrigerator, and for coated maple candy about six months at room temperature. (Coated maple candy should not be kept in the refrigerator.) The shelf-life for maple cream is about two months in the refrigerator, but it can be stored frozen for a long period of time.

  • Maple syrup can be substituted for all or part of the sugar required in a recipe? If using syrup reduce the amount of liquid by 3 tablespoons for each cup of syrup used.

  • There is no permanent damage done to trees that are tapped.

  • Only about 10% of a trees sap is gathered each year.

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