Evaporators & Finishing

All Things Evaporators: Part II

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Scroll down or click under the Evaporators and Finishing Archive tab to read Part I.

Managing Your Syrup Pan

What happens in the syrup (or front) pan determines the success or failure of every producer’s season. It is here that all the standards of maple syrup quality come together. Ideally, the right density meets the right color and the right flavor. The science is using instruments to determine the exact time to draw off the syrup. The art is that sixth sense of knowing when everything is moving toward the perfect draw-off. That sixth sense is something that requires experience and is often handed down generation to generation. If the science and art come together properly, the result is golden amber maple syrup with the perfect maple flavor.

When sap transitions from the flue pans to the syrup pans, many gallons of water have already been removed leaving a sap concentration of roughly 18-19 Brix. If syrup represents 1 gallon of the remaining liquid, approximately 9 more gallons of water still need to be evaporated in the syrup pans. The speed at which this happens is relative to the size of the evaporator you are running and the quality of your fuel source. In most rigs, the transition happens quickly, and operators must devote their undivided attention to avoid problems and ensure a quality product.

Unlike flue pans, the front or syrup pan is a flat bottom designed to create a surface with even heat exchange. There are several types of front pans on the market today. Traditional drop flue evaporators were equipped with a standard reverse flow pan which allowed the operator to change the side used to draw off when niter (sugar-sand) built up. Over the years, this style of evaporator has seen modifications.

One improvement included designing the pan so that the flow can be reversed while allowing the draw-off to remain on one side. This is accomplished with a series of valves and external plumbing directing the flow of sap from one side to the other. An example of this would be the “Leader Revolution Pan.” Producers found this improvement to be helpful to avoid the movement of draw-off equipment from one side of the rig to the other.


Cross flow design on a raised flue evaporator.  Electronic floats calibrate sap depth between the back and front pans.

Another front pan configuration is the cross-flow design. Cross-flow pans are installed setting across the arch hooked in series with the draw-off near the front of the last pan. There can be anywhere from two pans on a standard rig to four pans on bigger rigs designed to handle “High Brix Concentrate”.  Because niter tends to accumulate in the draw-off pan first, that pan needs to be switched out to avoid excessive niter build-up. Most producers using this system have one or two extra pans cleaned and ready if the draw-off pan needs to be switched.

The depth of the sap in the front pan is determined by the design of the evaporator. A drop flue rig will maintain the depth set by the flue pan float, but a raised flue rig allows producers to set a separate depth in the front plan. Producers should carry approximately 2 inches of liquid across the front pans allowing syrup to boil evenly to the draw-off point. As pointed out in the first evaporator post, if hot spots develop, that area of the pan will tend to boil faster increasing the risk of burning. The trouble usually occurs when you draw off large volumes of syrup at one time. This causes the liquid level to become very uneven, you might have 2 inches in one part of the pan and only a half-inch in another.  Removing small batches more often will prevent uneven syrup levels and ensure a steady even boil.


Site gauge for monitoring sap depth on a raised flue evaporator.

It bears repeating that producers should pay close attention to bubbles in the sap. As liquid temperatures go above 219 F, the liquid will gravitate toward the hot area, localized boiling becomes more intense over the hot spot, and steam and bubbling from the more intense boil becomes more concentrated and noticeable. The result is that the sap is becoming more concentrated in the hot zone. This means the sap is becoming more concentrated in that area. As concentration increases and sap thickens to syrup, the thicker liquid will not flow evenly toward the draw-off point, and you could be headed for trouble. At this point, you need to let more liquid into that portion of the pan to re-establish flow toward the draw-off. Maintaining a constant even flow of syrup in the form of low volume draw-offs stabilizes the process. Make all your adjustments in small increments and remember it takes time for that adjustment to affect the process.

Three important factors must be controlled to maintain a constant boil.

  • First, maintain a steady even fire in the firebox.
  • Second, control your foam in the flue pan.
  • Finally, control niter build-up.

In Part 3 of this series, the focus will be on controlling foam and niter build-up in the syrup-making process – come back next week!

Author: Les Ober, Geauga County OSU Extension

All Things Evaporators: Part I

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A Simple Yet Complex Process

Many producers refer to boiling as the art of making maple syrup.  Boiling on a modern evaporator is a process requiring about 45 minutes to move from the inlet at the start to the draw-off at the finish.  Bringing 2% sap through a float at the back of the machine and moving the sap forward  through a series of channels until it reaches 66 Brix at the opposite end may sound quite simple; however, properly boiling syrup is a very complex scientific process based on physics, chemistry and microbiology.

To meet USDA Standards, maple syrup must be at least 66 percent sugar. This is referred to as syrup density which is measured in Brix. Brix is a measurement scale based on the percentage of sugar in a sample. Because Syrup is made up of over 98% Sucrose sugar, we simply define the density of maple syrup as percent sugar. In this case, 66 Brix syrup would be 66 percent sugar. Once we know the percentage of sugar in sap, we can determine the amount of sap that it takes to make a gallon of syrup. To do this we apply a simple formula – the “Jones Rule of 86” – where you take the factor of 86 and divide it by the percent sugar to obtain the number of gallons of sap required to make one gallon of syrup.  For example, 86 divided by 2% sugar content sap equals 43 gallons of sap to produce one gallon of syrup.

You can start to see how chemistry and a little math plays a role in converting sap to syrup. What about physics? When sap is boiling, a gradient is formed causing the heavy syrup to move in front of the lower density sap. If the pan on the evaporator is boiling, then the two will not mix unless you suddenly lower the temperature in one section of the pans. Disrupting the boil results in an intermingling of sap temperatures which causes a drop in boiling intensity. The result is the dreaded big batch and improper syrup density.

Microbiology comes in to play when colonies of microbes begin to increase. Lack of microbial sanitation is the most common reason for the darkening of syrup potentially resulting in an off flavor. Microbial action changes the sucrose to invert sugars (glucose and fructose). As the percentage of invert sugar increases, heat causes syrup color to darken. It is possible to darken the syrup to a level where the color and flavor are severely impacted. If you ignore any or all of the science involved, you could end up with something that you will definitely not want to put on your own table let alone sell to your neighbor.

Managing Your Flue Pan

The flue pan is where all the heavy lifting of the boiling process is done. There are two basic types of modern evaporators, raised flue and drop flue. The level of sap in a pan is controlled by a float box. With a drop flue, you only have one float box controlling the depth of the sap throughout the entire machine. The sap level is maintained at 1.5-2 inches from back to front. Two inches depth is a safe starting point for beginners. Any change you make to the float at the back of the evaporator will be transferred forward to the draw-off point. Thus, all changes should be minimal and incremental. A raised flue evaporator has two floats, one for the back pan or flue pans and one for the front pan or syrup pans. Though you are still running just one evaporator, you can control two separate processes. The double float design allows you to run your depth in the back pan at 1 inch while running the front pan between 1.5-2 inches. The dual control increases evaporator efficiency, more rapidly boils off water, and better controls the draw-off process. The shallower you can run the back pan the more heat you transfer into the sap and the harder the boil. If you run your back pan too deep, the boil slows, and efficiency is reduced.


Raised Flue Evaporator with device to evacuate away steam from boiling process.

Which style of evaporator you prefer is strictly a personal preference. And once you learn your evaporator’s sweet spot, once the depth is set, you can generally leave it alone. All evaporators should have at least one sap level gauge on the flue pan (raised flue evaporators should have a second gauge between the two front pans). A properly calibrated gauge allows you to know the exact sap level no matter if the flue pan is hooded or clouded with steam.


Drop Flue Evaporator with reverse front flow pan.

When running your evaporator, the basic goal is to maintain a boil across the entire rig with the hardest boil occurring in the flue pan. There is an old saying among maple producers, “You haven’t earned your producer’s badge until you have burnt a pan.” Trust me if you have never scorched a pan, or come close to burning one, consider yourself lucky. Usually the most common reason for burning a pan is human error, usually caused by a distraction. When you are running a rig, you are dealing with extreme heat. Stack temperatures can run between 600-1000 degrees F. You are applying that heat to a relatively small skinny volume of liquid (2 inches spread across the surface of the pan) separated by a thin layer of stainless steel. The only thing that keeps that metal from melting is the thin layer of sap on top. If the sap boils out because you forgot to turn on a valve or you ran out of sap, bad things happen very quickly. Uncontrolled high temperatures can go from a scorch to buckling a pan in just a few short minutes. Your season could be over if you cannot find a replacement.

Tracking bubbles in your sap is a good way to monitor your boil. The bubbles in the pan should be moving slowly in one direction toward the draw-off. If the boil decreases and the bubbles move back and forth then an adjustment needs to be made immediately. If you spot trouble the first thing you must do is avoid panic. Move quickly and precisely. This is where knowing what to expect and what to do is vital and that only comes with experience.

Stay tuned for Part II next week!

Author: Les Ober, Geauga County OSU Extension

A Few Thoughts on Finishing Maple Syrup

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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

Things You Can Do to Ensure the Quality of Your Maple Syrup

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This post is in response to Dr. Michael Farrell’s article on maple syrup quality from the most recent Maple News. First let me say that the article was not only excellent but very timely. The article addresses an issue that all maple syrup producers should consider as another season is upon us. What I hope to do is highlight some of the areas in the production process where syrup quality can be compromised often resulting in off flavors. The University of Vermont and the Vermont Ministry of Agriculture has provided an excellent tool for identifying the sources of off flavors in maple.

After producing maple syrup for over 40 years and teaching seminars on maple syrup production for close to 20, I have made or personally witnessed most of the common mistakes that lead to off flavors and poor syrup quality. In this article I will go over some, but certainly not all, of the factors that lead to poor syrup quality. The good news is that most of the factors can be controlled by producers with best practices, in turn meaning you control the quality of your syrup. The Map of Maple Off Flavors (linked above) identifies 5 primary areas where off flavors occur: Mother Nature, defoamer, processing, chemicals and others. I want to address each area in order of how they would occur from start of season to finish.

When you start out the season, you need to be aware of several problem areas that can lead to off flavors. Most problems arise from the previous season’s equipment maintenance and show their ugly faces as the new season kicks off. When producers ask how they should clean equipment, my response is with a lot of water and elbow grease – and my answer is the same from large-scale producers all the way down to backyard hobbyists. Anytime chemicals are used to clean equipment, residuals left behind can compromise flavor. If you use chemicals on your pans to clean them at the end of the season, you need to thoroughly scrub away any chemical residue. If you use a tubing cleaner, make sure it is flushed entirely from the system. If you store filters make sure there is no mold on those filters when you dig them out of storage. (And never use detergents to scrub away mold on filters, THROW THEM AWAY!) The list could go on. A final guideline for this area is to always store your chemicals in a secure place away from your syrup processing so as to avoid unintended contamination of your final product. Most of the above is common sense but they need to be mentioned.

Probably the biggest culprit for off flavors comes during the processing stage. This is where the majority of mistakes are made that result in off flavors. When we grade syrup, we look at 4 primary areas density, color, clarity, and flavor. Even though each is judged separately they are actually all interrelated. Syrup must be 66 Brix to meet USDA standards and if it is below 66 Brix it can ferment and cause an off flavor. Syrup above 67 Brix normally does not have an off flavor but the higher density can cause crystallization in the bottom of each container resulting in lost revenue to the producer. As syrup moves across the front pan, density and color changes rapidly. Density changing with the rapid removal of water that increases sugar concentration, and color as heat changes the sugar molecules. Anything that interferes with flow of sap through the evaporator can cause the syrup to get darker and possibly cause an off flavor. Many feel that density is the most critical part of the process and at times reaching the proper density can be very difficult. Improper density management can lead to two off flavors that are very common in syrup – fermented and scorched. And these off flavors are often accompanied by undesirable colors as well.

We use three tools to measure density, the hydrometer, the thermometer and the refractometer. All sugarmakers use a hydrometer. Hydrometers should be inspected or checked for possible problems and replaced if suspect. Often the paper with the scale printed on it can slip resulting in the wrong Brix reading. Hydrometers can become coated with film resulting in inaccurate readings. A good hydrometer will give you an accurate reading only if it is used at the right temperature. Temperatures below that require consulting a chart to convert to the right Brix reading based on the specific temperature. Maple syrup boils at 7 degrees Fahrenheit above the boiling point of water or 219 degrees, and many producers use a thermometer to determine the draw off point. The only problem is that the 219 reading is only accurate if the barometer is at 29.9 Hg barometric pressure. Therefore, a thermometer needs to be recalibrated every time the barometric pressure rise or falls. Having an accurate syrup temperature is especially vital when it comes to setting an automatic draw off.

The final tool is what many consider the grand judge and jury of maple syrup density – the refractometer. For a refractometer to work properly, syrup must be finished and stable in temperature. This was pointed out the other day in a conversation with Robert Crooks of Marcland Instruments. For a refractometer to work properly, it has to be able to refract light coming through the sample and that can only be done accurately if the sample in the instrument is a clear finished sample. Taking a sample of cloudy unfiltered syrup will lead to an inaccurate reading. The temperature of the syrup also affects light refraction. Even though refractometers are built to automatically compensate for temperature, temperature must be stable. If you leave freshly drawn off syrup set in a container, it will continue to evaporate water until it cools down. Think of what happens to a pot roast when you pull it from the oven, it continues to cook beyond the temperature when you pulled it from the oven. This is why it is best practice to cover containers of hot unfiltered syrup in order to stop moisture loss. If you use a refractometer to set the draw off, run a sample of syrup through your filter and allow the sample to sit for 15 minutes before taking your refractometer reading. This will give you the most accurate reading from your refractometer.

If you use a conventional auto draw-off, be aware that it takes time to complete the draw off process. This means that syrup will be drawn off over a range of temperatures. Therefore set the draw off to actuate slightly below the desired temperature and it will finish slightly above. Using a hydrometer is the best way to set your draw off. However, make sure you are reading the hydrometer at the recommended syrup temperature. You can use a refractometer but remember it must be used on a finished, stable-temperature product, and this process may take more time than you have to make a correction on the draw-off.

As sap moves across the evaporator, a temperature gradient sets up. Ninety percent of the water is removed by the time the sap reaches the middle of the front pan, so syrup needs to move from the middle of the syrup pan to the outlet relatively fast to avoid darker and denser syrup than desired. A common mistake is to allow the pans to cool during the firing process. Anytime you cool off the pans, the temperature of the sap drops and this causes the boiling temperature to drop resulting in the sap on one side of the gradient to mix with sap on the other. Keeping constant and stable heat levels on the front pan is must and particularly crucial for wood-fired evaporators.

Another problem is foam control. Excessive foam in the back pan can cause problems with your float and may interfere with your ability to control the level of the sap in the evaporator. If this happens you will need to use a defoamer to control the problem. When using defoamer, the only place the defoamer should be added is at the point where sap enters the rear pan, and occasionally a couple of drops if needed at the draw-off if foam builds up as you are drawing off. This should be done at regular intervals placing the prescribed number of drops (2 drops per foot of width) where the sap enters the evaporator. Never spray defoamer across the front pan to control foam. Using defoamer in this manner will impede the boil and break down the temperature gradient. This can lead to the dreaded big batch.  If the front pan is foaming excessively, then the foam is not being properly controlled in the back pan, correct the problem back there. Use only small amounts of defoamer, excessive use can result in an off flavor. Organic producers must use safflower or canola oils which are very poor defoamers. And be careful with organic products as well because an excessive amount can produce off flavors.

Another potential problem (there are a lot of them, right?!) is niter build-up which can lead to scorching in your evaporator. Any niter build-ups will insulate the bottom of the pan from the syrup creating a potential hot spot which can eventually result in a scorched spot on the pan. You must keep liquid in contact with the pan at all times. Always keep your pans as niter free as possible by rotating sides or using a clean set of pans between batches. Using a good syrup filtering system to remove niter is vital if you want to produce syrup that meets the highest clarity standards. You should be able to read newspaper print through a sample bottle of syrup that has been properly filtered. Cloudy syrup with a lot of niter can produce an off flavor. Remember every time you heat your syrup to a boil, more niter will precipitate out and needs to be re-filtered. That is why you do not want to bring your syrup to a full boil when canning. 185 degrees Fahrenheit is the required temperature for canning.

As maple producers, we fight the growth of bacteria through our entire system. When bacterial colonies multiply in sap, they convert Sucrose sugar molecules to Glucose and other invert sugar molecules. This increase in invert sugar, when exposed to heat, will lead to a darker finished product. This is most prevalent at the end of the season when the bacterial content of sap is at its highest. Bacteria can affect the entire process of making syrup from the taphole to canning. Because sap has sugar content, it is a perfect media for bacterial growth. It goes without saying you can never be too clean when it comes to making syrup. Sap needs to be collected in clean equipment, it needs to be kept cool, and it must be processed quickly. If you start with a properly sanitized system at season’s beginning, you will have far fewer issues at season’s end – though issues may still crop up. Maple producers need to know when to end the season. Producing syrup late in the season when the trees are near budding and the sap is out of peak condition has little value to you and even less to the industry’s customers.

As you can see, there are many factors that a sugarmaker must consider in order to maintain the highest standards of product quality. From equipment sanitation to efficiency throughout processing, paying attention to details is critical and is what separates the best producers from the rest of the pack. Making the highest quality product possible should be your goal. Your reputation as a maple producer depends on it.

Author: Les Ober, Geauga County OSU Extension

Tips on Managing Sugar Sand

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Every year, I have a few questions about the universal problem faced by all sugarmakers – fighting heavy niter build-up.  With heavy flood runs, this can be increasingly problematic to battle.

Here is one question I received:

Does anybody have any advice on how to get this pasty mud-like stuff to filter better. I have been battling this for three years now and don’t know why, any advice would be greatly appreciated!

This was my answer to his question:

You have a problem that hundreds of producers have every year. So you are not alone in your question of how to deal with this problem.

Niter is caused by minerals precipitating out of the sap as it boils, and every woods if different in the amount produced. In fact, the amount of niter you battle in your sugarhouse is correlated with the mineral content of the soil in your sugarbush. When we boil sap, it is very similar to lime forming on a pan after you boil hard water several times.The only difference is that we are keeping the niter in solution and filtering it out. That is the key to removing niter. You must keep it in the solution until you run it through your filter, and you need to keep your syrup very hot and filter it immediately. If the filters cool for a long period of time, sugar will likely crystallize on the filter and slow flow. If you are using a felt or orlon filter, always use a pre-filter. In fact, try stacking several filters in layers and when the filter flow slows down, you can just pull off the top layer and continue to filter the syrup.

If you use a filter press, make sure you use enough filter aid to initially charge the filter. Even though filter presses have filter papers in between the metal plates, it is the filter aid that actually does the filtering. Make sure you use enough filter aid, but do not over do it. Mix the filter aid and the syrup completely before running the press. Keep the syrup hot and try to run larger batches. If you run small batches, the filter press cools and you will not be able to run as much syrup through until you change filters. Watch your pressure and change filters when the pressure starts to build excessively. This should prevent blowouts and having to re-filter.

Normally we filter with a conventional filter tank with a stack of 5 to 10 pre-filters on the tank and 1 orlon filter. I try to put enough pre-filters on for the better part of the day. After we filter, we transfer to a 20-gallon heating tank. Heat the the syrup to 185 and then run it through a pressure filter into 15 gallon drums. I try to never bring syrup back to boil or more niter will precipitate out.

Hope this helps and good sugaring.

Author: Les Ober, Geauga County OSU Extension

Fighting Foam, a Never Ending Battle

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Now that the syrup season is in full swing, here are a few tips to keep your evaporator running smoothly. When running your evaporator, the goal is keep a steady boil across the entire rig with the hardest boil occurring in the flue pan. It’s important to remember you remove 80% of the water is removed in the flue pan. This requires that you get the maximum amount of performance out of this section of the evaporator. When foam builds up in the back pan, the evaporation rate decreases and the liquid level drops. Once the foam level drops (using defoamer), the float registers that there is not enough sap in the rig and reacts by sending a large slug of raw sap into the flue pan. This immediately slows the boil. This reaction is eventually transmitted across the entire evaporator in the form of a large batch of syrup that comes off all at once, instead of small batches coming off at regular intervals. In most cases, large batches can be traced back to inconsistent foam management.

Let’s take a close look at defoaming an evaporator. First – the products used in this process. Today’s commercial defoamers are made of a natural food grade product. They come in liquid or powder form. Several methods are used to put defoamer in the evaporator. One is to simply put it in by hand. If this method is used, the defoamer should be put into the evaporator somewhere near the flue pan inlet. Other methods would be the use of a defoamer cup in the corners of the pan and injection devices that administer a precise number of drops over a set period of time. The cups work well on larger rigs where the boil in the flue pan is very aggressive. I have found on smaller rigs, especially if no pre-heater is used, the boil never gets close to the cups and the defoaming action is inconsistent. The most consistent results can be obtained with the by-hand method simply by placing a precise number of drops into the flue pan every 5 to 10 minutes or every time you fire the rig. A timer works well to remind you to keep this process going. For me personally, the biggest problem I have is remembering to place the defoamer in the flue pan because we are not using wood and not firing on regular intervals.

The number of drops used varies anywhere from 3 drops for small rigs up to 10 drops on larger rigs. The width of the evaporator determines the number of drops and this increases by 1 drop for every 6 inches of evaporator width, (3 drops in a 2 foot wide rig, 4-5 in 3 foot rig, up to 10 drops on a 6 ft rig). There are only two places to put defoamer, in the inlet corner of the flue pan and, only if needed, at the draw off point. One of the biggest mistakes is to put defoamer randomly across the middle of the pans, especially the syrup pan. Doing this kills the boil and promotes intermingling of syrup of different densities. The result will be the dreaded big batch. Incidentally if your syrup taste a little oily, and I sincerely hope not, you are probably using too much defoamer. If you are organic, use organic Canola Oil in place of commercial defoamer.

Managing foam looks simple (and it is!), but if you forget, the penalty is a bunch of chain reactions that can ultimately end up in inconsistent syrup draw-off and improper density of the syrup that you are processing. You end up constantly trying to compensate in the syrup pan for a problem that should have been handled in the flue pan. If it gets too far out of control and you end up taking too much syrup off your front pan at one time the result could be a scorched pan. When evaporators do not run smoothly bad things happen. Been there done that and believe me it is no fun.

One new item I tried during the 2015 season was Wendell Maple Foam Fighter. It is an electronic device that precisely places defoamer into the evaporator inlet over a precise number of minutes. On the first day of use, we were boiling fast and hard and the foam was starting to really build. I kicked on the new device and within 15 minutes the foam in the flue pan settled down. When it came time for the first draw-off of the day, we expected the usual bigger than normal batch. That did not happen. The first draw-off was average size and the rest were the same and evenly spaced over the time we were boiling. If this any indication what this device will do, it was money well spent.

Author: Les Ober, Geauga County OSU Extension

Maintaining the Quality of Maple Syrup Through the Proper Handling of Maple Sap

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The taste of pure maple syrup is one of nature’s most enjoyable flavors. If it is produced properly, the taste ranges from sweetly delicate to a pronounced robust, uniquely maple flavor. However, maple syrup that is improperly made or handled can be just as unforgettable for other reasons. Maple producers need to be very conscious of how easy it is to destroy the quality of the product they are producing. They need to take every precaution to preserve the integrity of this unique product. How sap is handled during the course of the season will determine the volume of high quality syrup produced.

Maple syrup is made up of 98.5% sugar. The level of sugar is measure in Brix or a percentage of the sugar present in the product. For all practical purposes, we simply say that the product is maple syrup when it reaches 66 Brix or contains 66% sugar. For this reason, maple syrup in Ohio and elsewhere must be finished at 66 Brix.

Simply stating that syrup is all sugar smooths over some of the important details. The primary sugar in maple syrup is Sucrose; however, there are small amounts of Glucose and a trace of Fructose present. Glucose and Fructose sugars are referred to as the invert sugars, and invert sugar levels can determine if a specific batch of maple syrup is usable to make certain value-added maple products. The remaining portion of the syrup is composed of various minerals, amino acids, and organic acids. The most common organic acids are Malic and Fumaric acid, the same found in many fruit juices. The presence of these acids is a relevant fact and has a bearing on how maple syrup is processed.

The quality of maple syrup normally declines as the season progresses. The sap that comes from the tree when the weather is cold and the taps are fresh will most often produce the lightest and the highest quality syrup of the season. The primary reason for this is the relatively low level of bacteria found in the sap. Research done at the University Of Vermont by Dr. Mariafranca Morselli documented the fact that sap inside the maple tree is essentially sterile; however, because sap is normally 1.5 to 2.5% sugar, it becomes an ideal medium for bacterial growth. Once a tree’s sap reaches the taphole, environmental conditions cause bacterial colonies in the sap to flourish. This bacterial growth is responsible for two processes, one inside the tree and another outside. First, bacteria will cause the taphole to dry out and heal thus reducing the flow of sap from that tap. And second, sap containing large concentrations of bacteria will produce darker grades of syrup. A study by Legace, Petri, Jacques and Roy found that:

The presence of microorganisms in the sap has the ability to breakdown the sucrose molecules, the main organic component sap, into glucose and fructose subunits. These subunits react with the heat in the evaporation process to cause the darkening of the syrup and an intense, caramelized flavor.

Morselli & Wahlen also found that if producers can keep sap from being contaminated with bacteria, trees will produce light colored syrup almost to the end of the season. Maple producers can learn much from these studies. Best practices, such as not blowing in the hole to dislodge wood chips, drilling holes straight and clean, properly seating the spout, and regularly replacing or cleaning spouts and drops, all help prevent bacterial growth.

Bacterial growth that starts at the taphole will multiply and flourish as the sap is collected and stored prior to evaporation. This is the reason that sanitation is so important during the collection process. Tubing systems have solved many problems when it comes to collecting sap, but they have also created a few. Sap being collected with a vacuum tubing system moves sap quickly away from the tree to the collection point. It creates a cleaner environment for sap collection unless it is improperly maintained. Unfortunately, poorly maintained tubing presents one of the highest risks for increased bacterial growth. Stagnant sap sitting inside of tubing warms quickly, and research done by Morselli and Wahlen at the University of Vermont, found that bacterial populations sitting inside warm tubing systems double every twenty minutes. Therefore, tubing systems need to be installed properly and maintained with tight lines all sloped toward the collection point.

Changing spouts every season and rotating drop lines on a regular interval enables modern-day producers to achieve a high level of vacuum line sanitation. The invention of the Check Valve Adapter (CVA) by the researchers at Proctor Research Center has totally changed the way we think of taphole sanitation. The research done at Proctor documented that sap actually siphons back into the tree in the absence of vacuum. CVAs prevent that back siphoning from occurring. The other important revelation was that if we can maintain vacuum on the lines even during periods of minimum flow, lines are kept cooler and bacterial growth is minimized. The result is that in many maple operations the only time that vacuum is turned off is when the temperature goes below freezing for a prolonged period of time. We are definitely changing the way we run our vacuum tubing systems and it has not only improved syrup production but also syrup quality.

At the end of the season all collection lines need to be thoroughly cleaned and drained. If possible they should be rinsed again before the start of the next season. Sanitation is no less important in bucket operations. Buckets should be washed before the start of every season. During the season sap needs to gathered often, and buckets should be washed, dried, and stored quickly at season’s end.

Once the sap arrives at the sugarhouse it should be processed quickly. Do not allow sap to sit in open tanks for long periods of time. Collection tanks need to be drained and washed down between runs. To speed up processing, evaporator capacity should be properly matched to the volume of sap coming into the sugarhouse. Producers who struggle to keep ahead of the sap flow and allow large volumes of sap to sit unprocessed for long periods of time often struggle to make top quality syrup.

There are several techniques that can slow bacterial growth and speed up the processing time. Sap can be exposed to ultraviolet (UV) light. Morselli and Wahlen found that sap treated with in-line UV lamps reduced bacteria by 99.4 % early in the season and reduced bacteria 86.2 % later in the season. Evaporation rates can be increased by using pre-heaters or enhanced evaporator units such as the Steam-A-Way or Piggyback. By far the most popular means of cutting down on processing time is by using a reverse osmosis (RO) machine. The invention of the RO has revolutionized the maple syrup industry. Because of the use of modern RO technology, extensive expansion of maple operations is now possible. Modern RO machines can concentrate sap from 2% to over 20% before it ever goes through the evaporator. However, a word of caution, sap that has been run through the RO process is subject to increased bacterial growth, therefore concentrated sap needs to be processed as soon as it comes out of the RO to prevent darkening of the finished product. Of course, the final step in the syrup-making process is proper setup and operation of the evaporator and the maple syrup filtering systems. Once again proper sanitation of all the processing equipment is very important if quality is to be maintained.

The purpose of this post is to get you to thinking about the importance of sanitation and the role sanitation plays in the process of making high quality maple syrup. The beginning of the season is the time to adopt good sanitation practices.

Author: Les Ober, Geauga County OSU Extension

The Finishing Pan: Where The Art and Science of Making Maple Syrup Meet

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The old timers called it an art, modern maple producers call it a science. In reality, it is probably a little of both. One thing is for certain, what happens in the finishing pan determines the success or the failure of a season. It is here that all of the maple syrup quality standards rise or fall. Here the right density meets the right color and the right flavor. The science is using instruments to determine the exact time to draw off the syrup. The art is that sixth sense of knowing when everything has coalesced for the perfect draw-off.  The result is golden amber maple syrup with the perfect maple flavor.

There are several types of finishing pans on the market today. The reason for the difference is to manage niter or sugar sand. Niter is the mineral content in the sap that precipitates out in the boiling process. To manage niter, most front pans are designed to either change to a side or to a pan with a lower niter deposition. Reverse flow allows the operator to switch sides when niter builds. A variation on design is the one-sided draw-off which utilizes reverse flow and a series of valves to redirect the flow of sap from one side to the other. An example of this would be the Leader Revolution. The other style is the cross flow in which there are multiple front pans connected by stainless tubing. In this configuration, the pan closest to the draw-off point is rotated with a clean pan. The best policy is to start with a clean pan every day and change during the day when needed. Pans can be cleaned with white vinegar and hot water. This is a very effective way to clean pans with a minimal amount of elbow grease. The amount of niter present in sap varies from season to season and from woods to woods. If improperly controlled the result can be a scorched pan.

Once the sap, or in this case concentrated sap, reaches the front pan or finishing pan, the sap is approximately 19% sugar. This is sap that has not been run through a reverse osmosis unit. It has been concentrated by boiling only. RO concentrate enters the pan at a higher concentration. As the concentrated sap is crossing over into the front pan, it should reach 213 degrees at 29.9 inches barometric pressure. It is also at this temperature that the concentrated sap is not only becoming denser but also starts changing color. As the density increases, the sugars react with the heat to form the amber color we associate with pure maple syrup. It is also at this time when the bacteria in the sap can interact with the heat and the sugars to darken the syrup. All of this happens in the finishing pan and over a relatively short amount of time. This reaction can occur quickly and if the operator is not paying attention, syrup can actually burn or caramelize further darkening the color. In this case, the density often goes past 66 Brix as well resulting in a thick heavy syrup and potential profit loss.

To make sure we pull the syrup off at the right density, we can use a variety of instruments. The most common and least expensive are the thermometer and the hydrometer. Most evaporators come with a thermometer that is placed at the point of draw-off. Water boils at 212 degrees Fahrenheit at sea level and a barometric pressure of 29.9 inches of mercury (Hg). Because syrup is rarely produced in a location at sea level and the barometer is seldom at 29.9, producers must make some adjustments. We must boil water near the evaporator and reset the thermometer that is used to make syrup. This process of adjusting to match the barometric pressure must be done daily and whenever the barometer changes due to weather front movement. This can occur quite often during an average sugar season. This is why most producers prefer to use a hydrometer for the final test, and use the thermometer to give them an approximation of when to draw-off.

The hydrometer is the judge and the jury. There are two lines on a hydrometer.  The top line is for hot syrup and the bottom line for cold. Use the top line. Always use a hydrometer cup full of syrup that is at least 211 degrees Fahrenheit. Bring the instrument up to eye level or set it on a stable object close to eye level for the most accurate reading. Producers need to test their hydrometer annually against a calibrated refractometer. Hydrometers get jarred around and the paper containing the scale can move or become dirty and give a false reading. If the reading is inaccurate, replace it. A refractometer (the instrument used to verify hydrometers) is very accurate, the new ones are digital, and refractometers make temperature adjustments on the fly – however, they are also cost prohibitive for many.

The automatic draw-off is a great tool for any producer in any size operation. It makes drawing off syrup a lot easier, especially when boiling RO-concentrated sap. It is nothing more than a digital thermometer hooked to a valve that draws the syrup off at a very precise temperature. Everything I said about the syrup thermometer applies to automatic draw-offs. Most producers set there draw-offs with a hydrometer. During the sequence of opening and closing the auto draw-off, the syrup is actually being drawn off within a small band of temperatures. The thing to remember is that the draw-off will open at a very precise temperature, but if the flow is slowed by foam or a valve coming into the draw-off is restricted, the temperature will rise above the desired level resulting in denser syrup.  All automatic draw-offs should be installed with a valve between the pan and the draw-off. This allows the producer to adjust the flow of sap coming off the pan. Open the pan valve so a steady stream flows through the draw-off mechanism, and try to avoid a heavy stream that will result in a large batch. The draw-off should close and the temperature on the readout should drop 4 to 6 degrees and then quickly come back to the desired temperature. The result is a series of small batches coming off in a relatively short amount of time. The producer needs to check the final product in the bucket or tank when the auto valve closes and adjust the draw-off settings accordingly. It is very easy to get a denser product than desired if you are not making continual fine-tuning adjustments. It is not a set-and-forget instrument. Today there are newer auto draw-off that compensate for barometric pressure but again the cost may be prohibitive for smaller scale producers.

Another area to consider during the finishing process is foam control. You only control foam in the front pans at the point of draw-off and only if the flow out of the draw-off point is being held up by the foam. If this happens, a single drop of defoamer will reduce the foam to the point where the bubbles will decrease and flow will increase. Avoid using defoamer anywhere else as it causes the gradient to break down and syrup densities will intermingle. If you are foaming over in the front pan, it is usually because the foam is not properly controlled in the flue pan. Occasionally it may be necessary to knock this foam down but try to avoid this if possible.  If the foam is properly controlled in the flue pan there should be minimal problems in the front pan. The only exception would be coming into the first draw-off after a layoff. All types of sap will behave differently during the initial draw-off. Watch for increased bubbles and denser steam, this is a sign that you are making syrup across the front pan. In this case do not panic, just slow your boil down and stabilize the evaporator as quickly as possible. The result is usually one big batch of syrup followed by reduced boiling temperature. The next batch should be normal – if not, look for the problem.

Author: Les Ober, Geauga County OSU Extension