The maple season is now underway and this is a good time to talk about handling you 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 from the time the sap leaves the tree 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 tap hole. 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 microbe’s 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, the microbes multiply rapidly. Producers can monitor the potential for microbial growth by checking the temperature of the sap. If the temperature is close to freezing the growth is suppressed. Below 40 degrees F the growth of bacteria is slow but once the temperature rises above 50 microbial growth is rapid. The Chances for 50 degree and above temperatures are greatest at the end of the season.
The sugar present in sap when it leaves the interior of the tree 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 level increases the 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 high levels of bacteria can develop a very strong almost bitter in taste known as sour syrup. The syrup consistency takes on a thick almost rubber like appearance, 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 tap hole 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. Let it heat up to over 50 degrees and you asking for trouble. That happen 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 collect your buckets and let them hang until the next run. Do not leave 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. Sounds expensive to run the pumps 24/7 but it works to your advantage, keeping lines cool and dry when the sap is not running. Another essential is to follow the tubing sanitation guidelines, installing new spout 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 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 put your tank in the shade. Surround it in snow if possible. Freeze some sap and put it in the tank during warm spells. What ever it takes to keep you sap cold. Check the sap temperature periodically. If it reaches 50 degrees boil immediately.
What about the evaporator. Boil your sap as quickly as possible. If you ae using and 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 in in some cases quadruple the sugar concentration. Bacteria will build 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 F shortly after the season. Paying attention to detail when it comes to handling sap and syrup pays big dividends.