Tapping New Forest Farming Opportunities in Central Appalachia Through Black Walnut Syrup Production

View the project final report

Commodities

• Additional Plants: trees
• Miscellaneous: syrup

Practices

• Crop Production: forest farming, forestry
• Farm Business Management: new enterprise development, value added
• Sustainable Communities: local and regional food systems

To address the questions surrounding vacuum on sap harvest, the proposed research will take vacuum measurements along the length of three tubing systems: 3/16” gravity vacuum, 3/16” mechanical vacuum 5/16” mechanical vacuum (5/16” tubing does not work with gravity vacuum because the larger diameter does not allow capillary sap flow). Knowing the actual level of vacuum delivered to the tap will remove one of the major questions about sap flow in black walnut trees: how to get the most sap from each tap. Following the methodology detailed below, data will provide evidence to inform recommendations on types of tubing systems, the maximum length of lines, and cost-benefit ratio of mechanical versus natural vacuum systems. These findings would help to provide guidance for development of new walnut syrup businesses, including the most cost-effective systems. With this information, new farms and forest landowners can enter the walnut syrup market using existing technology without the risk of costly trial and error.

The qualitative side of the proposed research will provide answers about the flavor profiles of walnut syrup. The maple syrup industry grades products based on color and depth of flavor: golden delicate, amber full-flavor, and dark robust flavor. These are generally correlated with the period in the season when sap was harvested, with early sap producing the lightest mild tasting syrup, and later sap runs producing darker syrup with more intense flavors. It has been observed that walnut syrup also varies in flavor and color, but correlations are not well-established. What is needed is a system to grade the quality of walnut syrup. Farmers and landowners would benefit through guidance on controlling variables to  determine specific flavors of walnut syrup. Quality standards also contribute to consumer awareness and marketability of this new product. 

As one of the largest black walnut syrup producers, Tonoloway Farm is able to produce batches of walnut syrup throughout the season with consistent processing methods. Qualitative analysis by expert members of the advisory board will evaluate syrup from specific batches from two seasons and multiple farms. In addition, off-flavors produced by bacteria (if present) or harvesting too late in the season can also be analyzed and defined to inform standards for walnut syrup production.

Update July 2024

This is the Final Report for the SARE funded project “Tapping New Forest Farming Opportunities in Central Appalachia Through Black Walnut Syrup Production”.  An Annual Report was submitted in December 2023 which would have served as final report.  However, the project end date was extended, so this is the final report for the project.  Separately, four reports that summarize the research have been uploaded on the SARE Southern website.

Our research site is at Tonoloway Farm which is located on the Highland Turnpike, in McDowell, Virginia (in Highland County, East of Staunton).  The farm has web presence at https://tonolowayfarm.com/ and email contact is ForestFood@tonolowayfarm.com.  During the project period the farmer researcher, Mr. Christoph Herby, moved to Switzerland with his family to take an overseas assignment with the International Red Cross.  Now managing the farm are Will Shepherd and Jen Rattigan.  During the past two years of transition they have taken over the tapping and syrup making operation, and work related to this project. 

Entrance to the Tonoloway Farm, research site (photo courtesy of Will Shepherd)

The research envisioned by Herby and Hammett was divided into two portions.  To address the questions surrounding vacuum on sap harvest, the first portion sought take vacuum measurements along the length of three tubing systems. The qualitative side of the proposed research sought to provide answers about the flavor profiles of walnut syrup. What follows is a final update on work in these two core areas: 1) sap harvesting methods and 2) qualitative characteristics of walnut syrup (i.e., tasting panels to evaluate flavors and grades).  The results for both portions have been documented in detail in two reports uploaded to the SARE website.

Progress

What follows is a brief summary of progress.  Documents and reports that describe our work in more detail and results of project activities have all been uploaded to the SARE website.

1) Sap harvest with vacuum tubing

While capillary vacuum works well with maple, walnut trees release more gas into the sap lines, which reduces the transmission of vacuum through the line.  In order to accurately understand the dynamics of the layout of the trees and their elevations, a land survey was conducted. Three maps are attached that depict the trees tapped and their location.

During the first year, labor for research line set up, tapping and sap collection and processing was slightly less than planned, as setup and data collection didn't take as much time as anticipated. Remaining activities this first syrup making season included cleaning the research lines, conducting a professional site survey to locate (map) and determine the elevation for the trees tapped in the study.  The report compiling data and analysis, and reports on our findings. 

Data collection is complete for the quantitative part of the vacuum study. We collected vacuum data on 4 different days during the 2022 black walnut sap flow season (usually during March), on 6 different lines in 3 configurations as detailed in the research plan.

This portion of the research was conducted during the first year and a half of the research period.  We conducted a controlled study on sap flow in the three combinations of tubing diameter and vacuum source. Quantitative data shows vacuum measurements for multiple points along the length of the sap lines. This data was charted against elevation (for gravity vacuum) and distance from the vacuum source (gravity and mechanical vacuum) to determine which method results in the best transmission to vacuum at the tap. The same data was collected throughout the season at times of low, medium and high sap flow. 

With this new information, new producers can enter the walnut syrup market using existing technology without the risk of costly trial and error.  A separate but detailed report on the vacuum tubing research, along with copies of the survey maps that contributed to the vacuum tubing research, was submitted with the annual report in late 2023. All should be useful to existing and new producers of walnut syrup.

The next step is to submit the vacuum report for review at a peer-reviewed journal article.   The report uploaded separately will be synthesized for a broad audience using the black walnut social media platforms, and through extension and university reporting venues.

Measuring vacuum in the sap collection tubing lines (Tom Hammett photo)

2) Qualitative characteristics of walnut syrup

The purpose of this portion of the project sought to provide answers about the flavor profiles of walnut syrup. The maple syrup industry grades products based its grading system on color and depth of flavor: golden delicate, amber full-flavor, and dark robust flavor. These are generally correlated with the period in the season when sap was harvested, with early sap producing the lightest mild tasting syrup, and later sap runs producing darker syrup with more intense flavors. It has been observed that walnut syrup also varies in flavor and color, but correlations are not well-established.   What is needed is a system to grade the quality of walnut syrup. Farmers and landowners would benefit through guidance on controlling variables to determine specific flavors of walnut syrup. Quality standards also contribute to consumer awareness and marketability of this new product. We introduced our project to tasting panel members with this introduction (see the sensory panel report). 

The maple syrup industry product grades are based on color and depth of flavor: golden delicate, amber full-flavor, and dark robust flavor.  But, a similar system to grade the quality of black walnut syrup is needed. Farmers and landowners will benefit through guidance on controlling variables (season, timing of tapping) to determine specific flavors of walnut syrup. Quality standards would also contribute to consumer awareness and marketability of this new product. 

Christoph Herby boiling sap to make syrup (Tom Hammett photo)

To achieve this, the research team coordinated and conducted two tasting panels to meet and ascribe qualitative characteristics. The first tasting or sensory panel included persons with a scientific background in tree syrup research and maple industry professionals.  A second tasting panel included culinary professionals, in addition to the principal investigator and collaborating farmer. Originally, due to COVID restrictions, it was planned that samples be mailed to each member of the panel, along with clear instructions and a survey sheet to collect qualitative data detailed above. The panels were delayed and eventually the COVID-19 restrictions were abated.  So, we could meet with the panels in person.  We chose local/regional experts thus avoiding the need to travel, delays due to shipping, and packaging and mailing costs.

Observations for and the results of these panels are summarized in a separate research report which has been submitted with this report.  A draft copy was provided for review to SARE in late 2023.  Plans are to use the report as the basis for a peer-review paper, social media venues appropriate to those interested in black walnut syrup, and through extension and university publications.

This portion of our research was unique – no other such research with walnut syrup was found.   Hence it attracted attention from a group of unanticipated collaborators - many of which are listed in the next section.  Virginia Tech also secured additional funding to help support further testing for nutrition and pectin content. We enlisted the Department of Food Science and Technology at Virginia Tech in this effort.  A report on the results of the testing has been uploaded on the SARE website.

Another unanticipated additional collaboration (at no-cost addition for the project) was a sensory panel held as part of a food science course taught at Virginia Tech.  This opportunity arose after planning for the project was complete. The syllabus for the course and findings of the class panel can be forwarded on request.  A detailed report on the research and its results for this segment report have been uploaded separately from this final project report.

We continue to see great interest in this work.  Others participated on sensory panels.   Here is a representative list of cooperators in this research.

1. Christopher and Lauren Herby owners, Tonoloway Farm in Highland County, VA, are now based in Switzerland; original research collaborator
2. Will Shepherd with Jen Rattigan, now serving as manager and producer of syrup at Tonoloway Farm, Highland County, VA – the site of the on-farm research.
3. Dr. Mike Rechlin, Maple Specialist, Future Generations University, Franklin, WV
4. Mary Hufford, LiKEN Associate Director, and faculty member at The Ohio State
5. Faculty, Food Science & Technology Department, Virginia Tech – offers course in sensory observation; in 2023 focused on comparing maple with black walnut syrups

6. Melissa Wright, Director, Food Producer Technical Assistance Network at Virginia Tech

1. Gary Mangold, black walnut syrup producer near Petersburg, West Virginia; provided syrup for the sensory (tasting) panels; found market for the “pectin” from black walnut sap; buys this material from Tonoloway Farm
2. Albert Yodder, black walnut syrup producer in Maryland; provided syrup for panels
3. Ellie Maben, black walnut syrup producer in WV; provided syrup for the panels

Proposed research on walnut syrup production will focus on two core areas: 1) sap harvesting methods and 2) qualitative characteristics of walnut syrup (i.e., expert panel to evaluate flavors and grades).

1) Sap harvest with vacuum tubing

In recent decades, the maple syrup industry shifted from drip harvest methods to vacuum tubing systems. Numerous studies demonstrated that maple trees respond to negative pressure at the tap hole with increased sap flow (van den Berg 2012). It’s worth noting that current tapping standards maximize sap flow without detriment to the trees themselves. In early 2020, Tonoloway Farm contributed to research showing preliminarily that black walnut trees respond favorably to vacuum too (Rechlin 2020). However, there are two methods of vacuum used in the maple industry: gravity pulling on capillary action through 3/16” tubing, and mechanical vacuum through either 3/16” or 5/16” tubing. While capillary vacuum works well with maple, walnut trees release more gas into the sap lines, which reduces the transmission of vacuum through the line. It remains unclear if high levels of vacuum can be transmitted with walnut sap all the way up 3/16” and 5/16” tubing. 

The proposed research would perform a controlled study on sap flow in the three combinations of tubing diameter and vacuum source. Quantitative data would show vacuum measurements for multiple points along the length of the sap lines. Vacuum gauges will be installed at every other tap along the length of two 3/16” lines with gravity vacuum, two 3/16” lines with mechanical vacuum, and two 5/16” lines with approximately 20 taps each, for a total of 120 data points. This data can be charted against elevation (for gravity vacuum) and distance from the vacuum source (gravity and mechanical vacuum) to determine which method results in the best transmission to vacuum at the tap. The same data would be collected throughout the season at times of low, medium and high sap flow. 

2) Qualitative characteristics of walnut syrup

To evaluate the qualitative characteristics of walnut syrup, samples will be retained from each batch produced at Tonoloway Farm during the 2021 and 2022 seasons. A minimum of three samples per season (early, mid, late) will be taken, with potential for 5-6 samples if conditions allow. They will be labeled by date and charted according to that year’s harvest calendar: early, mid and late harvests.  Samples will be finished to 66-68 degrees brix (measurement of sugar content) and bottled for storage according to industry standards (180-190 degrees F) to ensure stability in storage. Notes will be recorded for any notable circumstances during the production of each batch. In addition, finished syrup samples will be purchased from other walnut syrup producers, to be compared with those from Tonoloway. 

Following the 2022 harvest season, an advisory board will be invited to meet and ascribe qualitative characteristics to each sample. The advisory board will include two persons with a scientific background in tree syrup research, a maple industry professional, and two culinary professionals, in addition to the principal investigator and collaborating farmer. Potential characteristics include visual properties, acidity, flavor profiles, intensity of flavor, and presence of any off-flavors. These characteristics will be correlated to the harvest period from the two sample seasons, and compared with syrup samples taken from other farms. This qualitative data will be used to determine if walnut syrup properties vary according to the period of harvest, while also revealing if there is a point in the late-season after which flavor deteriorates. The advisory board will aim to correlate potential off-flavors with processing notes to determine their origin, if present. Such observations will help producers evaluate their own syrup and avoid practices that lead to off-flavors.

N.B. In the event that COVID-19 prevents the gathering of the advisory board in person, samples will be mailed to each member of the board, along with clear instructions and a survey sheet to collect qualitative data detailed above.