About Birch Syrup
Introduction
If you’ve never heard of birch syrup, much less tasted or used it, you’re not alone. Birch syrup is produced much like pure maple syrup through tapping trees to collect sap and then boiling the sap to concentrate and caramelize sugars. However, birch syrup is not to be confused with-or substituted for-pure maple syrup. A sampling of birch syrup quickly reveals a mix of fruity-tart and complex caramelized sugar flavors reminiscent of raspberries, tart-cherry juice, apple-butter and molasses. The syrup produced from birch trees does not have the distinct wintergreen aroma and flavor some people associate with birch beer or soda. The wintergreen oil is found within the bark of the tree and does not exist in the sap.
The infancy of the birch syrup industry in North America allows for different interpretations of birch syrup that may or may not appeal to different consumers. Individuals that have consumed birch syrup produced in the Northeastern United States most likely experienced a product that could be described as a mix of balsamic vinegar and molasses with a fruity raspberry like element.
Birch trees are a common hardwood species in northern hardwood and boreal forests. Birch trees, like maples, have an added benefit of significant sap flow which can be consumed as sap or turned into a syrup. Producers in Alaska, Canada and Europe, where there would generally be no sugar maples, turn to birch trees to make a unique and distinct sweetener.
As an existing or beginning maple producer, birch trees present a way to diversify product line by creating a unique and interesting product while extending the production season, and utilize existing processing equipment otherwise not being used at the time. The information provided here will help you understand timing of tapping, sap flow, sap collection and yield, evaporation and packing of finished product.
Trees
Any birch tree can be tapped for sap collection and all birch species tend to yield similar quantities and quality. In order to tap birch trees, you must be able to identify them. The stark white bark of the paper birch and the distinct golden strands of bark on a yellow birch make this task easy. However, in heavy stands of aspen, it can be a little tricky to distinguish paper birch. Additionally, as yellow birch ages, it’s bark becomes thick and plate-like making it visually very distinct from its younger counterpart.
To better aid in identifying birch trees, view Cornell University’s College of Agriculture and Life Sciences woody plants database below. The following trees are common native birch species in the eastern United States and can be successfully tapped for syrup production:
Yellow–http://woodyplants.cals.cornell.edu/plant/32
Paper/White–http://woodyplants.cals.cornell.edu/plant/34
Tapping & Sap Collection
So, when are birch trees tapped? The biggest difference between tapping birch and maple trees is the time of year. Unlike maples whose sap flows during freezing and thawing temperatures that creates stem pressure within the tree, birch sap flow is controlled through root pressure as sap is moving up the trees for bud break. As a result, birch sap flow typically does not occur until temperatures consistently reach 50 degrees F or higher. Colder weather prohibits sap flow while the warmer the weather, the greater the sap flow. Birch is a great addition to a maple operation because the season starts almost seamlessly when maple production ends. At the Cornell Uihlein Research Forest in Lake Placid, NY we generally tap our birch trees in mid-April with production lasting into the first week of May. A timing of tapping project was conducted in 2018, funded by the Northern New York Agricultural Program, looked at the best time for tapping birch trees and found that right at the end of maple season was best; a summary of that research is included in another section.
Except for the time of year trees are tapped, tapping and sap collection methods are comparable to maple. As in contemporary maple production, vacuum tubing systems are the ideal way to collect birch sap. If you are not familiar with tubing systems for sap collection the Cornell Maple Program offers resources on tubing and a maple beginner’s handbook which can be found on the Cornell Maple website. Use of a tubing system makes sap collection easy and keeps utility vehicles and other heavy equipment out of the woods during mud season. For beginners or small producers, options for sap collection can include traditional bucket or bags on a tree, a gravity tubing system, or a combination of tubing and buckets.
At the Cornell University Uihlein Research Forest we have been tapping birch trees since 2012. Original sap collection concepts and research involved an integrated maple and birch tubing system. Through using our existing maple system we were able to keep upfront costs low by adding only lateral lines to existing mainlines and valves to isolate the birch sap from the maple sap. However, the end of maple season and the start of birch is not necessarily an abrupt transition. It is recommended, if you have an existing maple tubing system, to keep the sap lines separate so fresh and quality birch sap can be collected and remain uncontaminated by buddy maple sap. Our systems have since been separated. However, we do hang our birch sap mainlines below the maple mainlines, from the same high-tensile wire, in areas where the birch lines follow the maple lines. This saves a significant amount of labor and material costs in the initial installation. With easy planning, existing sap collection tanks and releasers can be cross utilized from maple to birch season.
The equipment, tools, supplies and nomenclature used in maple sap collection are directly applicable to birch sap collection. The following terms are typical to tubing collection systems:
Tap Hole: A hole drilled with a specialized tree tapping bit which allows sap to flow from the tree. The standard tap hole diameter is 5/16” with a depth of 1.5”.
Spout (spile, tap): A tubular piece pounded into the tap hole, seating against the wall of the tap hole, and allows sap to flow through and either into a bucket or tubing system. These can be of varying diameter: 7/16”, 5/16”, ¼” and more obscure 19/64”. The standard spout is 5/16” diameter, low taper and made of some form of plastic. These spouts are generally one-time use. Stainless steel spouts are available as a reusable option but sterilization is necessary.
Drop Line (drop): A vertical section of 5/16” or 3/16” tubing connecting the spout in the tree to the lateral line. Drop line length varies but is generally over 30 inches allowing flexibility for tap hole location in the tree.
Lateral Line: A length of 5/16” or 3/16” tubing which runs perpendicular to the main line, pitches up and away while running along the trees and connects drop lines to the main line system. Lateral lines generally have less than 10 trees included on each and for best results should be under 150 linear feet from the main line.
Manifold (saddle): Connects the lateral line to the main line. There are many variations of this item including specialized “plastic welded” on fittings requiring minimal maintenance.
Main Line: Large diameter tubing in these standard sizes (inches): ¾, 1, 1.25, 1.5, 2 and up to 3. This tubing allows the system to drain all sap from the lateral lines to one collection point. A mainline could have sub-mainlines branching off.
Releaser (sap extractor): A sealed vessel which collects and separates air from the sap when a vacuum pump is in use. The releaser allows sap to be removed from the system while holding vacuum on the system. When a releaser fills with sap, it then dumps sap into a holding vessel through mechanical means or via a pump. Releasers are not needed if a diaphragm pump is used.
Vacuum Pump: Piece of equipment which removes air and lowers the pressure in the tubing system facilitating sap flow. Use of a vacuum pump in a tubing system can potentially increase sap yield by 50-150 % over traditional bucket or a gravity tubing system in regard to maple production. However, it is yet unclear if sap yield from birch trees is increased through use of a vacuum pump. In the least, a pump in a birch system aids in quickly moving sap from the woods to a holding area.
Standard 5/16” spouts, fittings and tubing are recommended in a vacuum system for birch trees. Use of the newer 3/16” tubing and fittings is generally not suggested; if used, care should be taken to keep tap hole shavings from entering the tubing system. The smaller inner diameter of 3/16” tubing is susceptible to plugging with bacteria and yeast restricting sap flow in the system. Due to warmer daily temperatures during birch season the build up from micro-organisms can be exacerbated.
Vacuum tubing systems are intricate and initial costs can be high. For the beginner, this system can also be confusing and intimidating. A simple gravity system using many of the same elements from the vacuum pump system, can easily be established. A gravity system can be installed using mainlines and lateral lines connecting the trees to a central collection point. A less complex concept involves using only lateral line tubing and fittings to collect sap in buckets or larger vessels.
Sap can also be collected in buckets using 5/16” spouts or the less recommended 7/16” spouts. A spout with 7/16” diameter leaves a larger wound within the tree. Birch sap is slightly acidic, therefore, food grade plastic or stainless steel buckets are suggested against galvanized (which should be avoided anyway) and aluminum buckets because of chemical reactions with the sap. When using buckets a lid is recommended to keep out insects and debris. Buckets can be hung from the spout on the tree or left on the ground using a single drop line going into the bucket; a few trees can be connected by tubing and dropped into a bucket for convenience. With tubing systems, sap is delivered to a location of your choosing, buckets need to be collected whether by hand or mechanical means. Having equipment in the woods during birch season can cause severe damage to tree roots and road systems during this sensitive time when soils are soft.
With a collection system in place tapping birch trees is just like maples: locate a healthy spot on the tree to the side of any existing tap hole, use a sharp 5/16” tapping bit to drill a clean hole 1.5” deep and be prepared to get a little wet! Sap flow in birch trees is quite vigorous and on occasion can squirt the person tapping the trees. You can now insert your spout, gently pound it into the tap hole and move to the next tree!
What can be expected in terms of sap volume and sugar concentration? Sap flow is strong, in our 2019 season we collected an average of 20 gallons of sap per tap in a 14 day period. In the same year, our maple forest produced 12.5 gallons of sap per tap in a 35 day period. Despite higher sap flow we start to really see the divergence from maple production with sap sugar concentration (%brix). The brix average in our last three seasons was 0.86%, with concentration generally landing between 0.5-1.0% (you did read that right). The average sap to syrup ratio for the same seasons was 104:1 sap to syrup. The average ratio for maple sap to syrup during the same three seasons was 37:1. To determine your ratio of sap to syrup you divide the 87.5 by the percent sugar in your sap as in the formula below (assuming finished syrup brix of 66.0):
Processing: reverse osmosis, evaporation, filtration and packaging
Once birch sap is collected it is highly recommended to concentrate the sap through reverse osmosis (RO). Reverse osmosis machines are available for any sized operation and there are even machines that come in a bucket for hobby operations. These machines are used to remove water and concentrate sugar in the sap quickening the evaporation process and saving energy. With sap sweetness of 0.7% it would take substantial time and energy to use an evaporator exclusively to turn birch sap into syrup. Use of existing equipment is also recommended, where possible, however, many existing operations don’t have dense stands of birch trees or comparable amounts of birch to maple. As a result, not all maple equipment (reverse osmosis, evaporators, filters, etc.) will be compatible for the smaller volume of birch sap you will process. Other variables to consider include tank size and location which will change from producer to producer.
Because birch sap is collected during warmer temperatures than during maple season it is important to process sap daily to protect sap quality and in turn, syrup quality. Daytime temperatures during birch season, even in Northern New York, can run over 70 degrees Fahrenheit! Sap will degrade very quickly if left to wait for processing because of equipment constraints. Spoiled sap will generally not make good syrup.
Due to such low sap sweetness it is recommended to pass the sap through an RO twice or cycle the sap through the RO until you achieve a high sugar concentration. At Cornell’s Uihlein forest we concentrate birch sap twice, once to 4-6 brix then a second time to achieve 12-16 brix, the higher the better! The resulting concentrated sap is known as concentrate and the pure water being removed is permeate. Permeate necessary in the cleaning of the RO so having the appropriately sized RO is important.
Once the sap is concentrated it is time to evaporate to finish the syrup. Any style of evaporation can be used, but care must be taken not to burn or scorch the delicate sugars (high amounts of fructose) in the birch sap, which results in an unfavorable bitter flavor. We have experimented with a few different processing techniques: wood fire 2’x6’ evaporator start to finish, start on wood and once 50 brix is achieved move to steam to finish, as well as steam only start to finish. All have produced satisfactory product. In the 2020 season we used our steam kettle exclusively and found that small batch processing with steam creates the most approachable birch product. We evaporate 5-10 gallons of concentrate at a time taking the finished syrup to 67% brix. This technique allows for quick evaporation at high heat. Because the evaporation takes place relatively quickly there isn’t enough time to scorch the sugars, yet allows for some caramelization to create complex flavors that move away from molasses and balsamic vinegar and mimic tart cherry juice, dried cherries and apple butter and a color that is more reddish brown than black. Birch syrup tends to be darker than maple and have more complex caramelized sugar flavors along with fruity aroma and tart flavor. The dark color comes from the specific sugar profile of the sap, which is primarily fructose with lower amounts of glucose and sucrose. Fructose has a lower temperature threshold for caramelization than sucrose or glucose.
Birch syrup is finished by removal of concentrated minerals and sediment through filtration. The same equipment used for maple can be used in birch production, however, we recommend double filtration as mineral content is very high in birch syrup due to such high concentration of the final product.
When packing birch syrup, we recommend using packaging that differentiates your birch product from your maple product. Birch syrup is best for cooking with rather than a table syrup. At our facility we pack our birch syrup in a similar bottle that would be used for balsamic vinegar or olive oil, showing that the product is best used in cooking rather than on pancakes.
Birch Recipes and suggested uses
Birch syrup has been described throughout as having flavors and aromas ranging from apple butter to a balsamic vinegar reduction. With such variations in flavor what are the best uses for birch syrup? The following are suggested uses for birch syrup as well as a few tested recipes.
Suggested uses (non-specific recipe uses):
Use birch syrup to enhance sandwiches, using a hearty bread like sourdough or peasant bread makes the experience even better. Make chicken salad to your preference and then drizzle a small amount on your sandwich for a sweet and tart element (think Waldorf chicken salad-grapes and walnuts). A sandwich made of roasted and then sliced beets, fresh goat cheese (chevre) and mixed greens with a drizzle of birch syrup on toasted or grilled bread makes a great lunch or light dinner. For a simple breakfast a good everything bagel, cream cheese, mixed greens and smoked or cured salmon with a drizzle of birch syrup is another great sandwich, even better if you’ve cured the salmon with birch syrup and fresh balsam or spruce tips. Avocado toast with birch syrup drizzled over is also fantastic.
Use birch syrup when grilling, roasting and smoking meats. When applying birch syrup directly to meat in grilling and roasting it is suggested to do so only near the very end of cooking to keep from burning the sugars in the syrup. When roasting meats, birch syrup can be used ahead of time as in the form of a brine for your Thanksgiving turkey or weekend pork roast.
Birch Syrup Recipes
Ingredients:
Directions: Preheat the oven to 400 degrees Fahrenheit. Place Brussels sprout halves in a large bowl. Toss with the olive oil, salt, and pepper. Dice the bacon. Spread the Brussel sprouts and bacon on a sheet pan in a single layer.
Roast for 20-30 minutes, or until nicely browned, tossing the sprouts about halfway through cooking. Once removed from the oven, drizzle with birch syrup and toss again. Serve immediately.
