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Q & A: boiling sap temperature

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Most recent answer: 02/22/2015
Q:
I make maple syrup . the water I boil off has sugar in it because the sap from the maple tree contains sugar my question is at 212 degrees I boil and the water evaporates, will I boil off more water at a higher temp such as 220 degrees and would the difference be much greater. I am asking this question because I seem to make more sugar sand at the temp I am boiling at
- robert dorr (age 71)
groyon vt. us.
A:

Yes, the temperature is very important. At exactly 212°F (100°C), water with sugar in it won't boil. The sugar raises the boiling point above that. We've discussed how solutes raise the boiling point in other answers. 

The conventional wisdom for maple syrup, according to what I've just read, is that the temperature should be close to 104°C, or around 219-220°F. At that point water will boil away until the sap is so concentrated that its boiling point is raised to 104°C. They say that's about the right sugar concentration for syrup.

If you leave the syrup at that temperature, evaporation will still continue, because the gas above the syrup isn't pure water vapor. However, that process is slower than boiling, so it gives you some time to take the syrup off the heat before it gets too concentrated.

Mike W.


(published on 02/22/2015)

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