Maple syrup is the product of boiling sap over heat until it reaches 7 degrees above the boiling temperature of water. While that is typically 219° F, the boiling temperature is influenced by atmospheric pressure. The amount of time required to cook sap down to syrup depends on the heat, the volume of sap being cooked, and the percentage of sugar (an indication of how much water needs to be boiled off).
We tapped about 550 trees for years, placing 10-quart pails on each tree. We collected sap with the help of many friends, pumped it into tanks in the back of our truck and a trailer, then drove back to our cabin to cook it down to syrup. A 600-gallon batch of sap would take about 20 hours to cook, with firing up the box under the pans every 45 minutes. Our life changed when we invested in a reverse osmosis (RO) machine. This machine removed 75% of the water from the sap. The outcome was a tremendous reduction in the number of hours required to cook a batch of syrup. We no longer had to cook throughout the night.
We now have a larger operation, with 4400 trees and vacuum lines. Due to the scale, we are using a larger RO machine, with each column measuring 8 inches x 48 inches. It is sized for the scale of the operation. Our little RO machine would not have met the challenge. Removing a large percentage of water from the sap enables us to cook in small batches and keep up with the sap flow. Instead of flat pans, we now cook with fluted pans that increase the surface area in contact with the sap. There is more engineering behind this operation, but we still cook over a wood fire.
You may be wondering why we cook over a wood fire. Most maple syrup producers use wood, oil or gas (propane or natural) as a heat source. We have always used wood, just as the generations before Karl did. There is a little bit of “if it isn’t broken don’t change it” to our method, but we also consider economics, resource availability, maintaining consistent quality and our own enjoyment of the process of cooking maple syrup.
Firewood is plentiful and we have three sons involved in this operation that share the labor. Logan loves using the chainsaw, so his job is cutting wood. Lincoln and Lance run the splitter and stack the wood. Neither one of them would use the word love to describe their feelings about this work, but they get the job done.
We use mostly hardwood and mix in softwood. The most important thing is that the wood be dry. Replenishing the firewood supply is a critical job in the off season. There were not enough dry downed trees on the property last summer to fill the woodshed, so we had 13 logger cords of wood delivered. A logger cord is 8 feet x 4 feet x 4 feet. For comparison, a face cord is one-third of a logger cord, or 8 feet x 4 feet x 16 inches. The last dimension is the length of wood commonly used in woodstoves.
This winter has provided an opportunity to supplement our store of firewood to ensure we have enough dry wood to get through the maple syrup season. Beavers, yes, they truly are busy, built dams causing water to back up in several acres of mixed woods on our property. With the water frozen, Logan has been cutting some of the dead black spruce. The wood is dry and stacked in our machine shed.
Over the past 25 plus years of cooking syrup, we have received praise for the quality of our syrup’s flavor. Quality is the outcome of many efforts, including actions we take to prevent the growth of bacteria. Cleanliness is essential, as is using fresh sap. We also believe that some of the depth of flavor in our maple syrup is related to our use of firewood as a heat source under the pans. Maybe the pace of cooking encourages caramelization, or perhaps a little waft of smoke kisses the surface of the syrup.
Is it is possible that taking the same precautions we do now but cooking over oil would achieve the same delicious flavor? Certainly. But I would miss the smell of the burning wood mixing with the unique and delicious fragrance of syrup forming in the pans. That combination is a little bit of heaven.