Final report for OS21-143
Project Information
The proposed solution comes through answers to two studies: quantitative research into the delivery of vacuum through tubing systems to tapped black walnut trees, and qualitative evaluation of the characteristics of walnut syrup. The proposed research will be conducted on Tonoloway Farm in Highland County Virginia.
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 [email protected]. 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.
- Christopher and Lauren Herby owners, Tonoloway Farm in Highland County, VA, are now based in Switzerland; original research collaborator
- 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.
- Dr. Mike Rechlin, Maple Specialist, Future Generations University, Franklin, WV
- Mary Hufford, LiKEN Associate Director, and faculty member at The Ohio State
- Faculty, Food Science & Technology Department, Virginia Tech – offers course in sensory observation; in 2023 focused on comparing maple with black walnut syrups
- Melissa Wright, Director, Food Producer Technical Assistance Network at Virginia Tech
- 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
- Albert Yodder, black walnut syrup producer in Maryland; provided syrup for panels
- 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.
Cooperators
- - Producer
Research
Much of the time leading up to tapping and syrup collection was spent purchasing and installing the equipment needed for the research, and laying out the initial black walnut sap collection (tapping). Most of the material acquisition is complete.
The timing and duration of the tapping season is weather dependent and may change slightly from year to year. This year tapping started in late February and lasted most of March.
During the first year, labor for research line set up, tapping and sap collection and processing is has been slightly less than planned, as setup and data collection didn't take as much time as anticipated. Remaining activities this season include cleaning the research lines, conducting the site survey, compiling data and analysis, and reporting 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 (during March), on 6 different lines in 3 configurations as detailed in the research plan.
Early in the second year we will have all the trees in the study surveyed (i.e., to determine location and altitude). We hope to schedule this in late Spring as weather and ground conditions permit. With this data we can plot results against tubing length and elevation, rather than just tap 1, tap 2, tap 3, etc.
For the qualitative black walnut syrup flavor study, we have multiple samples gathered from the research site (Tonoloway Farm) for the 2021 and 2022 seasons, representing quite a variety of syrup color and flavor profiles. We have also requested black walnut syrup samples from other sites throughout the black walnut growing range in the US to be delivered.
Prior to convening the panel of experts, we are obtaining samples for the black walnut syrup flavor study. Those should be delivered during April. We will schedule the expert panel to taste and analyze these samples - tentatively during May 2022.
Initial review of the data gives some very interesting and surprising insights on how vacuum impacts walnut sap flow. Analysis will be conducted after the syrup season and cleanup are complete in April. Other results from vacuum study, and the taste panel, will be reported on in the second year.
Update July 2024
Vacuum study
The key finding from the vacuum study is a game-changer for black walnut syrup production. It demonstrated that under the right conditions, walnut can achieve high vacuum and high flow rates similar to maple using 3/16 tubing. The critical aspect is maintaining an air-tight tubing system, which requires significantly more continual follow-up than maple, especially leak-checking at the taps, slowly driving them in further over the course of the season to maintain a tight seal. An important enabler for this method is having enough slope to achieve strong capillary vacuum. The implications are that we can set up a high vacuum system with walnut in a more cost-effective manner, with lower cost of tubing and without requiring a high-end vacuum pump.
Early in the second year we had all the trees in the study area located and mapped to determine their location and altitude. Details of this survey have been uploaded to the SARE Southern web site.
The study demonstrated that some level of mechanical vacuum is advantageous for stimulating flow. With 3/16 that mechanical vacuum does not transmit far up the lateral line from the mainline, presumably due to the same type of line friction and the "spring effect" of air bubbles mitigating the vacuum. With 5/16 it is possible to transmit the vacuum further up the lateral, but this didn't outweigh the negative factors like higher system cost, more stagnant sap in the lines, and needing to maintain continuous downslope. These findings were demonstrated consistently throughout the season, and some of the anomalies due to human error also provided interesting learning opportunities that are documented in the report. (see the full report uploaded on the SARE website: “The Tonoloway Black Walnut Vacuum Study” 2023)
Tasting panels
We conducted two expert tasting (sensory) panels to taste and analyze samples during May 2022. A summary of the results from this work compiled in a separate report was uploaded to the SARE website at the same time as the submission of this final report. (see “Black Walnut Syrup Sensory Panel Report” 2024)
From a marketing perspective, the tasting experiment provides us with the first rigorous comparison of walnut syrup throughout all stages of the production season. This resulted in clear understanding that walnut syrup intensifies in flavor over the course of the season, similar to maple syrup. While starting off mild and with flavors described as "butterscotch" the flavors evolve towards more acidity and intensity, eventually becoming too robust to be palatable when tasted alone. Our commercial experience has shown that these full-flavored late-season syrups remain valuable for production of blended syrups, imparting the walnut flavor on milder maple. The tasting panel of experts from the maple and culinary world also provided rich descriptions of the varying flavors of walnut syrup, providing a vocabulary to describe variance in this syrup that is largely unknown in the world of food science.
Ongoing is the testing for pectin content and sugar and nutritional values. A report on this collaborative activity has been uploaded separately at the time of this final report.
One challenge is that black walnut sap contains a “sludge” or particulate matter that many refer to as “pectin” that may not be appealing to consumers. This material accumulates in the bottom of the syrup container. The challenge is that this sludge settles in the bottom of the bottle while on the shelf. n years past local users would just calmly shake the bottle to dissipate the “sludge”. To build a market for this relatively new syrup product, it would be desirable to remove this material before selling to the public. One solution, Tonoloway Farm and other producers have started to put sap through a centrifuge to spin out this material with some success. The “pectin” is collected and then sold to another black walnut syrup producer in the area, Gary Mongol, who has found a market for this material. While it is not FDA approved, it seems to relieve some pain and discomfort from arthritis.
We have collaborated with the Department of Food Science and Technology at Virginia Tech. Faculty have included black walnut syrup in the sensory lab for classes. As more enterprises start to produce walnut syrup, we feel that this collaboration will grow. Especially as there is need to develop a grading system and marketing materials that describe walnut syrup and its attributes.
We have gained in kind support from collaborators including Future Generations University (i.e., loan of equipment such as a centrifuge for removing pectin, funding for testing syrup), and Virginia Tech (i.e., transportation, technical advice, equipment, support cost of food science lab, and analysis of syrup for nutrients and pectin).
Findings will be dissemination plans will include technical papers, and peer reviewed articles. Technical articles will be submitted to maple syrup industry publications (i.e. Maple Digest, MapleNews.com). In short, Tonoloway Farm has become a role model for others that are considering produce black walnut syrup.
Nest steps
We are confident that this research will form a valuable foundation for future work. The response that we have from those with whom we have consulted has been very encouraging to say the least.
Here are two interesting opportunities for further research: 1) testing of pectin separation via centrifuge and 2) long-term study of the impact of vine reduction and canopy thinning on sap yields and sugar content. For the first proposal, we tested a small centrifuge during the last two seasons, which allows the removal of pectin from sap prior to processing, resulting in two benefits: the possibility of using reverse osmosis to reduce boiling time and gain energy efficiency, and increasing yields by reducing the amount of sugar binding to pectin and subsequently filtered out from the finished product.
For the 2nd proposal, we have anecdotal observations that other farms produce higher yields per tree when they tap mature trees with wide canopies. We have noticed this on some of our own trees, although yield can be widely variable from one tree to another. Nonetheless, it is proven that maple trees produce higher volume and sugar content when they are allowed to develop a broad canopy, and our observations suggest this is true for black walnut too. With our large black walnut grove, there is an opportunity to do a controlled study on the impact of removing grapevines and thinning trees to promote wider canopies among the healthiest trees, testing the hypothesis that selective thinning could potentially increase the yield while reducing the number of taps.
Already we have embarked on several efforts that are beyond the timing and resources of this project. We also have garnered support, much of it unanticipated, to expand the project activities.
We welcome input and suggestions for next steps.
Educational & Outreach Activities
Participation Summary:
Outreach efforts will include a variety of activities. Initial outreach activities will focus on documenting the on-farm research activities in a form that is appropriate for farmers and landowners, agriculture service providers, and other stakeholders. In Year 1, these activities will include stand-alone educational materials including signage, and take-home or downloadable handouts. Also in Year 1, the research site will host farm tours for small groups by appointment. Working with our collaborators (i.e., Appalachia Beginning Forest Farmers Coalition, Virginia Tech Cooperative Extension Service) and through our network and web sites, we will target experienced and potential forest farmers who may wish to tap black walnut, agriculture service providers, and potential buyers or processors of syrup products. In Year 2 of the project, outreach activities will include a field day, a presentation at the Southern Syrup Research Symposium, and drafting a review of the research and its applications for posting on digital platforms (i.e., Black Walnut Producers Facebook group). We will also target larger and more diverse groups including the general public by providing research information at agritourism events such as the Highland County Maple Festival.
Findings will be disseminated through web-based distribution as appropriate through email blasts, and social media. Digital outreach for reporting results will use multiple online platforms such as the Virginia Tree Syrup Producers Association website and Facebook page. The team will also produce a peer reviewed journal article and other technical papers. Technical articles may be promoted through maple syrup industry publications (i.e. MapleNews.com).
An education plan will be developed for a field day that will focus on black walnut syrup production. The field day will include visits to the tapped walnut stand and the processing facility at Tonoloway Farm. Presentations of research will take place in the farm’s multi-use building. It will aim to give people enough information to start tapping black walnut trees and producing syrup. The first part of the field will discuss the differences between black walnut trees and maple trees, highlighting why a farmer cannot tap a black walnut in the same way a maple tree is tapped. Demonstrating tapping, and discussing tapping system set up, tap size, tapping depth, and timing of tapping will follow. The final portion of the workshop will cover the ongoing research and questions lingering in black walnut production. As a new industry, the process of making walnut syrup has yet to be perfected, further justifying the proposed experimentation.
Acknowledgement of the challenges of conducting this project in the era of COVID:
The actual research will be conducted outdoors, and alone by the project cooperator at Tonoloway Farm. However, for all planned activities, the project will take proper precautions and will follow all VA Department of Health COVID and CDC recommendations and guidelines. We will also follow procedures set by Virginia Tech and our collaborators. For instance, in response to the COVID reality, this year the project team has experience in providing safe learning experiences through organizing and presenting online tree syrup workshops, webinars, and certificate classes. Even with these new formats, the workshops have provided benefits across the region as participants have come from several states.
Because there aren't guidelines specific to farm visits, it is suggested that agritourism sites follow the guidance for farmers' markets. We will follow these recommendations and modify our procedures as the situation changes. For instance recommendations include only receiving one group of visitors of no more than 10 persons at a time, and these visits are conducted entirely outdoors. Physical spacing of 6 feet is maintained between farmers/presenters and visitors, and masks are worn at all times. Discussions will take place outdoors or in an open-air space. Signage about health public health reminders will be posted, and will be communicated with visitors prior to their arrival. Although sampling is discouraged, sampling products is important to this project. As needed we will provide samples in a modified format - small individual containers that will be disposed of after use, available hand sanitizer and hand washing and other recommendations according to CDC guidelines will be followed. Should on-farm in-person sampling not be possible, we will arrange to send samples with questionnaires by mail to the advisory board members.
Learning Outcomes
Incorporating black walnut production in land management systems with special emphasis on agroforestry
Management of vacuum systems for efficient production of sap collection
Developing taste and other product attributes for better marketing and product development
Project Outcomes
This farm is becoming a role model for others that might produce black walnut syrup.
1 small grant of $5,000 was obtained to help support testing of black walnut syrup in the Virginia Tech food science lab. A summary of the results of that testing is uploaded on the SARE Southern website.
Full recognition of SARE support has and will continue to be given on all Information Products.
When possible, a description of the research is summarized for visitors to the farm.
Presentations at workshops and conferences have been conducted and will continue. For instance, Dr. Hammett gave a presentation at the New River Symposium in April 2024.
Two major reports described above have been uploaded as Information Products to the SARE Southern website. As mentioned earlier, these two reports will each be the basis for potential peer-reviewed journal articles, and for articles in other outlets.
The results of walnut syrup testing in the Virginia Tech Department of Food Science and Technology have also been uploaded as an Information Product to the SARE Southern website. Future plans for further testing are outlined in the report.
A comparison of maple syrup and black walnut syrup through a sensory panel held as a lab during a course at Virginia Tech was conducted.
Tonoloway Farm and its production of black walnut syrup were the focus of LiKEN case study written by Dr. Hammett. A copy is uploaded with the other Information Products for this project to SARE Southern website.
In November 2023, during the first project period extension, a representative of Southern SARE, met with Dr. Hammett in Staunton, Virginia and we proceeded together to visit and tour the research site on Tonoloway Farm, and met with the Will Shepherd, the farm manager. A report on her visit entitled “Getting the Most Sap from Each Tap in Black Walnut Syrup Production” is available on the SARE website. https://southern.sare.org/news/getting-the-most-sap-from-each-tap-in-black-walnut-syrup-production/
A formal report on the analysis for “pectin” in black walnut sap and syrup is forthcoming.
Information Products
- The Tonoloway Black Walnut Vacuum Study (Manual/Guide)
- Research area mapping - results of survey (Manual/Guide)
- Black walnut testing results report (Workbook/Worksheet)
- Branching Out: Alternative Tree Saps Integrated with Agroforestry (Fact Sheet)
- Black Walnut Syrup Sensory Panel Final Report (Manual/Guide)