Cold weather has set in and that has allowed me to scan the maple chat rooms. Many of the questions that keep popping up are about finishing maple syrup. Is it too thick or too thin? Should I use a thermometer, hydrometer, and/or refractometer? Here are some of my thoughts on the subject.
Most of these questions are coming from backyard producers with a relatively small number of taps. Making syrup on a flat pan or hobby rig is not an easy task. You deal with a lot more “what if’s” than you would on a big evaporator. The process is simple – build a fire under your pan and bring your sap to the boiling point of water. Use a thermometer to monitor the process. That thermometer reading will vary from day to day depending on the barometric pressure. When the temperature goes 2 degrees Fahrenheit above the boiling point of water, add more sap, preferably pre-heated sap. Continue the process until all your sap is in the pan and begins condensing down. At that point, stop boiling, take the liquid into the house to store, and finish the batch. Most hobbyists follow this procedure and it works well. The trouble starts when you have a rig that looks like a big evaporator but does not run like a big evaporator. Many hobby rigs have channels and a heater pan and that is good. Sap should come into the back channel and gradually work its way to the channel on the opposite side near the front. Higher density syrup should move ahead of the lower density syrup. The problem comes in when you have to decide how much sap to let in at any one time. It works okay as long as you can maintain a steady flow into the rig. You need to maintain a depth of 2-3 inches across the entire evaporator. Overflow the hobby rig with liquid, and you will kill the boil. Once this happens, the sap of lesser density intermingles with the heavier density syrup. Big problem! Despite the fact you have channels, you are now no better off than you would be with a flat pan. On commercial evaporators, we have a thing called a float that automatically maintains the level of sap moving across the rig. With a hobby evaporator, you are the float and maintaining the proper level takes time and experience.
A few words on syrup-testing instruments. As stated above, you absolutely must have a thermometer. Two other tools that I recommended are a hydrometer and a refractometer. The hydrometer is necessary and a refractometer is nice if it fits your budget. Others have mentioned the Murphy’s Compensation Cup. I have used one for the last three seasons, developed by Smokey Lake – the Murphy’s Cup is a very useful tool.
I have two ways of measuring density directly off the evaporator. Here is the formula I use. First, I draw a sample into a hydrometer cup once the temperature reaches 7 degrees above the boiling point of water. Remember thermometers need to be calibrated. With your hydrometer cup filled with hot syrup that is above 211 degree Fahrenheit, insert the hydrometer into the cup. When it hits the top red line, you have syrup. I check this several times. Once I have the syrup where I want it, I pour one of the samples into the Murphy Cup. This device has a dial with corresponding numbers to those on a hydrometer. You insert your hydrometer into the cup and let it settle for 3 to 5 minutes. When the reading on the dial and the hydrometer match, you are at the right density. After that, I can fine-tune my auto draw-off for subsequent runs. On the last run, we are hitting between 66.0 and 66.5 Brix with this system. Refractometers are available in digital and analog versions. The digital versions seem to be the most popular. They are very useful to check syrup prior to bottling. Do not use a refractometer at draw-off, a refractometer’s reading is only accurate on temperature-stable and filtered syrup. The only reason for us to have a refractometer in the sugarhouse is to check the sugar content of concentrate coming off your reverse osmosis unit.
Author: Les Ober, Geauga County OSU Extension 