go-mr-54-3-spin-or-sieve-extby Kristen M. Castrataro
In some ways, making maple syrup is the simplest process in the world. You stick a spigot in a tree, hang a bucket from it, boil off the water, filter out the sediment and there you have it; the sweet nectar of the gods. It’s a process that requires no questioning, no redesigning, no tinkering. That is, of course, unless you are Charlie Chase of Charlie’s Sugar House in Coventry, Rhode Island.
Chase has been making syrup for 40 years. Each year he taps 2,000 buckets. Many of the taps are located on neighbors’ land, who grant permission in exchange for a bottle of finished syrup. He is working out of a new 30- by 40-foot sugarhouse, which is open for tours by appointment.
Charlie Chase is a man who lives by questioning and experimenting. Over the years he has performed many on-farm experiments with funding from USDA Sustainable Agriculture Research and Education (SARE) Farmer Grants. Those grants have addressed marketing state-shaped maple candies, tapping immature trees in a high-density sugar orchard, and developing an alternative icehouse refrigeration system. (Final reports on these projects can be accessed on the SARE website at: www.sare.org)
His most recent query challenges the current model: Is there a better way to filter the sediment out of syrup? The majority of sediment in maple syrup is called sugar sand, or niter, and is the natural result of heating the syrup. Minerals the tree uses for food clump together during the heating process and need to be filtered out. Other impurities such as dirt and bark can also collect, particularly when using buckets.
Hobbyists do not need to be overly concerned about the amount of sugar sand in their syrup. It is safe to eat and, if you have ever found some at the bottom of your syrup container, you know it is extra-sweet. For commercial producers, however, sediment is considered verboten. Its presence lowers the quality (grade) of the syrup and consequently reduces the price a producer can ask.
The color class of the syrup is measured by a spectrophotometer, an electronic machine that measures the amount of light that goes through the syrup, ensuring an industry-wide standard. The readings are conveyed in terms of light transmittance (% Tc). Each of the four classes has a range of approximately 25 points.
There is currently only one filtration method used in commercial syrup making: The filter press. After the sap has been boiled to evaporate off excess water, an additive is introduced to the syrup to help settle out any sediment. The syrup is then pumped under pressure into a set of plates (hollow and waffled) fitted with paper filters. The paper fibers are too far apart to provide adequate filtration, so diatomaceous earth is used as a filter aid. The microscopic “sea shells” interlock, creating a zig-zag effect as the syrup courses through, leaving dirt and niter behind.
While this is a very quick and relatively efficient process, it has some innate drawbacks. The first is that the filter paper needs to be replaced every hour or so to avoid tears. Torn paper results in poor filtration and lower grade syrup. For producers who bottle directly into glass, a small tear could ruin gallons of syrup. Those who bottle into plastic have a little more leeway on the marketing end, but the grade will still be lowered.
Cleaning the plates and changing the filter paper takes about thirty minutes, significantly reducing the amount of syrup that can be filtered in a day. Large producers can have multiple presses, eliminating down time, but smaller producers do not find that cost-effective.
Chase began questioning the status quo while watching an on-line video on biofuel. French fry oil was filtered using a centrifuge. The centrifuge is, in many ways, the polar opposite approach to a filter press. Rather than forcing syrup through a strainer, the centrifuge is gravity-fed. An inner bowl spins at 6,000 revolutions per minute, and the “clean” liquid gently spills over the edge into a catch basin beneath. The heavier, sediment-laden fluid remains in the bottom.
If it the system is effective enough to convert used oil into fuel, he wondered, why not use it for syrup? A little research suggested that the centrifuge may have been tried on syrup in the 1950’s, but he was unable to find records or results. He applied to SARE for a Farmer Grant and was approved.
SARE grants have a limitation, however. They do not finance long-term capital improvements. The centrifuge, costing around $1,500, was definitely considered a capital improvement. Never one to be defeated, Chase contacted the manufacturer, WVO Designs and asked, “How many centrifuges do you sell to maple syrup producers?”
The idea of a brand-new market was intriguing, so WVO Designs agreed to donate a centrifuge for the project.
With his new centrifuge set up, Chase and fellow collaborator Robert DuBos of Bats of Bedlam Maple Farm in Chaplin, CT, could begin work. To conduct the experiment, batches of syrup were divided in half with one being filtered and the other centrifuged. The grade of syrup can vary from batch to batch, so it was important that the processes be compared within batches.
The immediate benefit observed with the centrifuge is the reduction in clean-up time. If a producer has two collection bowls, it is possible to stop the machine, wait for the bowl to stop spinning, swap out bowls, and begin filtering with the second bowl while cleaning the first. The entire down time? Ten minutes.
Negating the down time, however, is the speed at which it works. The machine can only handle up to 15 gallons an hour. For small producers or those who finish separately from the evaporation process, this may not be a problem. Larger producers might find it a limiting factor.
An additional drawback is that the process turns the syrup into foam. Up to 10 percent of the volume of the finished product is actually air. The foam will rise to the top of the syrup, but it takes several days. Those who sell to brokers by weight may be willing to accept the inconvenience; those who intend to bottle immediately may not.
The final issue is how effective the centrifuge is as a filtration method. In this area, arguably one of the most critical, the filter press is superior. When measuring the color using the spectrophotometer, the centrifuged syrup scored 9 percent lower than the filter. For syrups in the middle of a class, that 9% is negligible. If syrup is on the edge, the filtration method might make the difference between an amber and a dark grade, for example.
So the question of spin or sieve, like so many things in agriculture, comes down to the needs and priorities of your particular business. If you have a clientele who would appreciate a no-additives approach, perhaps the centrifuge would be a good option for you. For many producers, however, this may be confirmation that they’ve been doing it right all along.