What is Reverse Osmosis for Maple Syrup?
Last week, our son, Lew, took a field trip with his pre-K class to Parker Family Maple, not too far from our own farm.
It was pretty cute witnessing a bunch of four and five year olds gasp in awe as they visited the different parts of the maple farm, but one of the funniest things to witness was when they had the opportunity to sample maple sap as it came out of the tree.
Lew has had a taste of maple sap directly from the tree before, so he couldn’t be conned into taking a sip. But the other kids were shocked because they expected what flowed from the tree to be sweet, thick, and syrupy. Instead, it tasted much like water, albeit lightly sweetened water.
As we’ve discussed before in some of our Factual Fridays, it takes quite a lot of work to make syrup from sap. On average, it takes about 40 or more gallons of sap to make just a gallon of syrup. Raw sap by itself isn’t super sweet and syrupy; the sap needs to be concentrated and water needs to be removed.
Traditionally, this has always been done by boiling, hence why the image of steam billowing out of sugarhouses is almost an overwrought stereotype of spring in the North Country. But there’s another process that modern sugarmakers rely on as well, and that process is something known as reverse osmosis.
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How Does Reverse Osmosis Work in Making Maple Syrup?
The purpose of reverse osmosis (RO, as it’s often abbreviated) is to remove more of the water from the sap before it’s boiled, thereby reducing the boiling time.
The dictionary definition of reverse osmosis is: “a process by which a solvent passes through a porous membrane in the direction opposite to that for natural osmosis when subjected to a hydrostatic pressure greater than the osmotic pressure.”
Anybody following that? No? Ok. Let’s break it down.
For those of us who don’t have our PhDs in chemistry or molecular biology, reverse osmosis basically relies on pumps that force the sap through porous membranes. Think of it as a super fine filter, so fine that the water is removed, but the sugars are too big to fit. What’s left behind is concentrate, which is then boiled to make maple syrup.
The vast majority of all maple syrup that is produced and sold is made via this process. It presents a lot of benefits to sugarmakers; namely, the fact that it increases the sugar level of the sap and cuts the boiling time in half.
Instead of removing the extra water with heat, you’re removing it with osmotic pressure. To make maple syrup, it has to be boiled. Full stop. There’s no way around it.
Does Reverse Osmosis Change the Taste of Maple Syrup?
There’s some controversy about whether RO systems should be used, because they do rely on more electricity. However, since the boiling time is reduced, it may be a trade-off, especially for operations that burn fuel oil. Vermont actually offers incentives for maple farms to add RO systems as a result.
On average, using reverse osmosis reduces processing time and energy requirements by 75% or more, based on studies done by Cornell.
As for flavor, it’s the same, though there are some maple purists who will argue differently. Yet in blind taste tests, most people can’t tell the difference between syrup that was produced with RO and that which was not.
The biggest hurdle, then, is truly the capital investment involved in installing an RO, which is why so many farms still do things the old-fashioned way.
The Takeaway
Using reverse osmosis isn’t better or worse than the traditional alternative; it truly comes down to preference and weighing costs and benefits. It’s like choosing to write something out by hand or use a keyboard to type it.
One saves time and energy but requires an upfront investment, and of course, there will always be the arguments for doing things “the old fashioned way” to preserve a culture and way of life.
But boiling sap raw without RO-ing it, for many producers, involves very late nights spent in the sugarhouse. By removing water prior to boiling with an RO, it can make the difference between being able to spend time with our families for dinner (and tending to newborn lambs, for some of us!) and not.
As farmers are strapped to do more in a limited amount of time with limited resources, technologies like RO really do make a difference in helping us get delicious maple syrup from our trees to your table faster.
