Join our own Les Ober and Mike Rechlin to learn about maple syrup quality standards along with the ins and outs of syrup grading Thursday evening 7 PM on April 15th. Register HERE!
The maple season is now underway and this is a good time to talk about handling your sap during and after collection. How you handle your sap prior to boiling will strongly affect the quality of the syrup you make. When quality syrup is the goal, timing is everything, and the clock starts as soon as the sap leaves the tree and doesn’t stop until it hits the evaporator.
When sap comes from the tree, it is sterile. That all changes once the sap starts to drain from the taphole. The air and surfaces surrounding the tap contain an abundance of microbes. The sap supplies the food source and a media for the microbes to grow and multiply. Research at Center Acer in Quebec found 21 different strains of microbes present in sap. At first you would think that could be problematic, but the reality is, you need certain strains of bacteria to produce the color and flavor that is unique to maple syrup. For microbial growth you also need the right temperature. Once the environment warms the sap, microbes multiply rapidly. Producers can monitor the potential for microbial growth by checking the temperature of sap. If the temperature is close to freezing, growth is suppressed. Below 40 degrees Fahrenheit, the growth of bacteria is slow, but once the temperature rises above 50 Fahrenheit microbial growth is rapid. The chances for 50 degrees and above temperatures are greatest at the end of the season.
When sap leaves the tree, the sugar is 100% sucrose. Once the sap is exposed to bacterial action, a small fraction of the sucrose is converted into glucose and fructose, often referred to as “invert sugars.” When maple sap containing sucrose, glucose, and fructose is heated, you create an amber color and a unique maple flavor. The problem is when undesirable bacteria begins to outnumber the good bacteria. This changes the chemistry of the sap. As the invert sugar level increases, syrup begins to take on a darker color and a stronger maple flavor. This produces the different grades of syrup. Syrup early in the season has a light color and very mild flavor. The maple syrup produced at the end of the season is often darker and stronger flavor. Syrup containing higher levels of bacteria can develop a very strong almost bitter off-taste known as sour syrup. The syrup consistency takes on a thick almost rubber like appearance and is often referred to as ropey syrup. Sour sap is often confused with buddy syrup because it happens most often at the end of the season. Buddy syrup is caused by sap coming from trees where the buds are getting ready to bloom. The chemistry is completely different from sour sap. Sour sap can happen any time during the season when a warm spell causes extreme flushes of bacteria growth. Sour sap can be prevented with good sanitation practices. Buddy syrup is a natural occurrence every year at the end of the season.
The quality of syrup produced from buckets and bags is best early in the season. Once the hole is drilled and the spout is exposed to the air, microbial development and taphole healing begins. Your season has begun, and you are now on the clock. A normal season for a bucket, bag or gravity tubing producer is 4 to 6 weeks. During the cold periods early in the season, the sap stays fresh just like it would if you put it in your refrigerator. Keep your sap below 40 degrees Fahrenheit and you are fine, but let it heat up to over 50 degrees and you asking for trouble. That happens readily at the end of the season. What many producers forget is that the bucket is an incubator for bacteria if it is not cleaned out regularly throughout the season. Leaving sap sit in a dirty bucket for any length of time is a problem. Remember bacteria does not grow in a clean dry bucket. If you are in a warm spell wash out your buckets and place them upside down next to the tree. If you are in a extended cold period, you should collect your buckets and let them hang until the next run. And never let stale sap sit a bucket, hot or cold.
As for tubing, we have discussed tubing sanitation multiple times over the years and those articles are in the Ohio Maple Blog Archive. Keep your lines as clean as possible throughout the season. This is difficult unless you are on continuous high vacuum. I know it sounds expensive to run the pumps 24/7, but it works to your advantage by keeping the lines cool and dry when the sap is not running. Another essential is to follow the tubing sanitation guidelines, installing new spouts every year, and new tees and drops every three years. You will improve the quality of your syrup.
Once you get the sap to sugarhouse, there are additional things you can do to improve quality. Sap that is going to be stored for longer periods of time needs to be stored in a stainless steel tank. Avoid poly tanks for sap storage. Plastic tanks are incubators for bacteria. Older galvanized tanks, like galvanized buckets, need to be discarded because of the risk of lead contamination. For the backyard producer, make sure your tank is in the shade. Pack around it with snow if possible. You can even freeze some sap and put it in the tank during warm spells. What ever it takes to keep your sap cold, take those necessary precautions. Anytime your sap reaches 50 degrees Fahrenheit and you can’t immediately cool it back down, boil immediately.
What about the evaporator? Boil your sap as quickly as possible. If you are using a reverse osmosis machine, make sure you do not let your concentrate sit. Boil it as soon as it comes through the RO. You double, triple, and in some cases, quadruple the sugar concentration in your sap, and bacteria builds fast in concentrated sap. If you are using a small evaporator, it is a good idea to drain and flush your rig. Leaving partially boiled sap on an evaporator in a warm sugarhouse can result in ropey syrup. Once the syrup is filtered get it into a barrel or a container as fast you can. Do not let it sit around. Pack your drums hot and do not open them until you are ready to use them. Do not store syrup drums in a warm building. Move them into the basement where it is cool or package the syrup at 185 degrees Fahrenheit shortly after the season. From the tree to final container, paying attention to details pays big dividends.
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.
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.