Flavor is an under-explored topic in sugaring. Sugarmakers, equipment manufacturers, and the few academics focused on maple syrup have focused their energy to figure out how to get more sap and to concentrate of sap into syrup with less time and less fuel.
My grandfather typed up a family history of sugaring going back to 1840.
It was a lot of work to split the wood for the fire, collect the sap, and haul it to where is was boiled down to syrup. It takes 42 liters of sap to make each liter of maple syrup. It takes many hours of boiling and feeding the fire. It is no wonder that the vast majority of innovation in sugaring over the last 150 years has been to increase efficiency. Less time and less fuel meant that sugarmakers could make more syrup and bring more income to their farms or have time for other farm chores.
Today most sugarmakers collect sap using networks of tubes from the maple trees to stainless steel tanks at the sugarhouse. We remove 75% or more of the water from the sap with reverse osmosis before boiling it over increasingly efficient stainless steel evaporators. Compared to how my grandfather started, my sugarhouse is the space age.
A few years ago, after installing a new larger evaporator and running it to get the highest evaporation rate, I made a batch of maple syrup that I did not like. The flavor of the syrup was acrid. That stopped me in my tracks.
What did I do wrong? Was it the equipment? Was it something I did? Was there something off with the sap?
The answer was not easy to find. A research paper in the 1970s noted that
Hydroxymethylfurfural is responsible for caramel and buttery flavors in maple syrup. It is created during boiling. If overheated or heated too long, it can transform and make an acrid-caramel flavor.
That was the flavor I did not like - acrid caramel. I had overheated the sap while boiling, even though it was within the specifications of the equipment. In the search for efficiency, I lost sight of flavor. There is a downside to the relentless pursuit of efficiency.
Equipment manufacturers sell by promoting efficiency. They do not sell by promoting flavor. Most of the academic research is on collecting more sap, increasing efficiency, avoiding off flavors, and health benefits. There is no equipment sold because of its role in making excellent maple syrup. There is very little academic research on making maple syrup with delightful flavors and aromas. This is largely new space.
Some old timer sugarmakers and academics have noted that modern maple syrup does not taste as good as it used to. They are starting to explore why. The two big suspects are tubing systems and reverse osmosis.
As a producer, I can't wait for the research.
We have to look at clues and piece together an answer. First clue - even with the same trees, process, and equipment your syrup will taste different throughout the season. It can even taste different day to day and within the same day.
If everything is the same, what is causing the flavor differences? We all know that as temperature goes up during the season, syrup gets darker and the flavor changes. We measure that by light transmission and invert sugar.
Aside from a hand wave at temperature, what actually changes the sap and its flavor? Including the Maillard reaction and caramelization that happen in the evaporator, natural fermentation of sap is the biggest driver of changes in flavor and color in maple syrup. Naturally occurring yeasts and microbes ferment the sap, splitting sucrose into glucose and fructose (invert sugar). That's only a piece of what those microbes do.
For example, lignin is biomass that comes out of the tree and degrades into vanillin in the presence of dissolved oxygen. As microbes work their magic converting sugars and lignin (among other things) they consume oxygen that is dissolved.
Where does dissolve oxygen come from? Old school buckets, when sap dripped in, each splash oxygenated the sap. Sap splashing into a sap tank oxygenates it. Sap splashing into a tank from an RO or in a releaser does too. If you leave sap too long, the microbes consume all the dissolved oxygen. That's when the development of good flavors stops and off flavors can begin.
Aerobic bacteria make good flavors. Anaerobic bacteria make nasty flavors. There are similarities to other forms of fermentation in food production, like yeast in bread making, cheese making, and yes in beer, wine, and other alcoholic products.
The difference is that in the others, the producer controls quantity of materials, time, and temperature. Bakers and brewers choose yeast to add. Brewers and winemakers have vats and fill them to capacity. They measure quantities carefully. They measure temperature carefully. They add sugars and hops and baking powder and baking soda by the leveled tablespoon and teaspoon. Sugarmakers get yeasts and microbes that fall out of the sky in whatever variety and quantity nature gives them.
Sugaring is the bull riding of fermentation — except the bell doesn't ring after 8 seconds. The sap runs when it does. The quantity of sap you get is constantly changing. The temperature rises and falls with the world around you. We control so little compared to other food producers. So you see that flavor can change dramatically based on quantity of sap, environmental temperature, your collection system, how long between boils, how much you concentrate sap and how soon after you boil.