Making Sense of Maple Syrup

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Grades of Vermont maple syrup. Dvortygirl/WIKIMEDIA COMMONS

I LOVE maple syrup. Born and raised in New England, I was taught at a young age to appreciate (more like worship) the authentic sticky sweet substance, and loathe the fake Mrs. Butterworth's bottles commonly found in chain restaurants.

This love was further reinforced by my childhood best friend, whose family owned a farm where they boiled down their own product. We’d sneak sips directly from the taps of the giant vats where the sap bubbled and boiled.

I even remember a field trip to a maple sugar house, where we learned about the syrup making process, and ate hot maple syrup poured over snow with a side of pickles. (I promise this is a thing and not some childhood fantasy.)

Recently, while sitting down to a delightful breakfast of French toast (which I ceremoniously doused in maple syrup) my boyfriend wondered out loud, “So, if maple syrup is mainly sucrose, then where does the distinct flavor come from?”

I’d never really thought about the chemical makeup of maple syrup before, and his question inspired me to do some digging. Just how much sucrose are we talking, and what else is in there?  

Sap straight from the tree is made up of mostly water and about 1-5 percent sugar. Of that sugar, 95-99 percent is sucrose, according to this study. But, there are also “trace amounts of other substances, including organic acids, free amino acids, protein, minerals, and phenolic compounds.”

During the production process, sap is boiled down in an “evaporator,” which removes most of the water, increasing the sugar content to around 66 percent. In fact, regulations state that maple syrup must contain at least 66 percent sugar (66.9 percent in Vermont and New Hampshire).

But, what about the taste? When heated, sugar browns and caramelizes giving it a distinct flavor. The same thing happens to the sucrose in sap when subjected to high temperatures (up to 219 degrees F) during the boiling process.

It all begins with sugar degradation – when sucrose is broken down into its two components fructose and glucose. Sugar degradation in maple sap is mainly caused by microorganisms and heat.

Though sap is sterile inside the tree, once outside it becomes a host for microorganisms, according to an episode of NPR’s Science Friday called The Sticky Science Behind Maple Syrup,

“As microorganisms act upon the sap and feed on the sap they will convert a lot of that sucrose into its component sugars glucose and fructose, which are reducing sugars,” meaning they are much more reactive, says Abby van den Berg of the Proctor Maple Research Center at the University of Vermont.

Applying heat to the sap only furthers this process, breaking down the sucrose even more.

The remaining fructose and glucose are then subjected to whole bunch of chemical reactions including the Maillard reaction and caramelization. Caramelization is still a bit of a mystery to chemists, and they still do not fully understand how the whole process works.  

“Although the single greatest influence of the process of transforming sap into syrup is the removal of water, the effect on the chemistry and flavor is not simply due to concentration,” says a study co-authored by van den Berg in 2009. “Rather, a number of complex reactions are involved which result in the chemistry and flavor profile of maple syrup.” 

And, the final product differs slightly depending on where the maple sap is from.

According to the Cornell Sugar Research & Extension Program, “Around 300 different natural flavor compounds have been found in pure maple syrup, though not all in the same syrup.” This is why syrup from Vermont is not like syrup from Wisconsin or syrup from Canada. This is also why it is very difficult to recreate maple syrup in the lab.

Well, this just confirms my belief that maple syrup is a magical substance that must be prized by all.

Luckily, Quebec has an Internationl Strategic Reserve of maple syrup in case there’s ever a shortage. And, if you’ve got access to a bunch of maple trees, you can try making it yourself. Also, check out the New England Maple Museum next time you’re in Vermont. It’s on my bucket list.

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