Value Adding Culinary Chestnut Seconds Through the Development of a Marketable Fine Flour

Progress report for ONC22-111

Project Type: Partnership
Funds awarded in 2022: $39,662.00
Projected End Date: 09/30/2023
Grant Recipient: Rural Action
Region: North Central
State: Ohio
Project Coordinator:
Tom Redfern
Rural Action
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Project Information


Rural Action will partner with three farmers from the Route 9 Chestnut Cooperative and the Shagbark Seed & Mill to develop value-added fine chestnut flour that can be marketed to our region’s bakeries, restaurants and retail markets. 

The demand for culinary chestnuts far exceeds the supply from our region. However, chestnut farmers from the Route 9 Chestnut Cooperative report that up to 20% of their harvest is Grade B (up to 20,000 lbs) and therefore unsellable as fresh chestnuts. These Grade B chestnuts promise a good return if they could be processed into a fine culinary flour, but the system for drying and milling is not yet developed in our region. Currently, the Cooperative uses low-tech equipment to create a coarse flour and does not have the capital to scale up and optimize the process to produce a fine chestnut flour. This project will research and document best milling practices, convene producers at two field days for peer learning, and gather qualitative data from buyers who are provided chestnut flour samples to evaluate. We seek to meet the need of diversifying producers’ chestnut portfolios in order to increase the production of this sustainable, climate-resilient crop.

 For more information about the Appalachian Staple Foods Collaborative’s Chestnut Partnership work, please contact Michelle at 
Project Objectives:
  • Research and develop the processing requirements to make fine chestnut flour out of grade B chestnuts
  • Identify the optimal milling equipment needed 
  • Record best practices for processing at a margin that’s economically viable for the farmer and miller 
  • Improve chestnut flour product through gathering qualitative data from a select customer base that is given samples to evaluate
  • Write elements of a business plan for processing grade B chestnuts that could be incorporated into any chestnut grower business plans
  • Host two field days at Route 9 to gather producers and customers to learn about value-added products and chestnut potential 


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Materials and methods:

Equipment: We purchased a B&W Manufacturing grain aeration pencil dryer from QC Supply to reduce moisture in the nuts prior to milling. The tool consists of a fan head and a 6’ tube that pulls large volumes of hot, damp air out of the chestnuts. This is especially important for milling during the summer months since humidity remains an issue.

Route 9 Cooperative's current process of milling chestnut flour consists of the following steps:

  1. Air dry chestnuts down to 10-12% moisture using drying boxes. Each box holds about four boxes each of which holds 800-1000 fresh weight (close to 8K lb).
  2. Peel using an impact peeler.
  3. Roast in convection ovens (2) at 75C to improve flavor and bring moisture down to 10% based on scent and texture. Typically it takes 2-4 hours to roast 50 lbs.
  4. Mill into quarter size particles. Milling capacity: feed 25 lbs at a time, takes 10 minutes. 

Moisture Levels

Moisture is an ongoing concern during the milling process since chestnuts have a 40-50% water content by mass. The moisture content of the chestnuts was just a bit high during our milling day at Shagbark Seed & Mill in May, as indicated by the tendency of the flour to bridge in the mill and the eventual growth of mold inside the refrigerated flour bags. 

Greg Miller of Route 9 Cooperative, previously found that 18% moisture is the threshold for mold in chestnut products. While the batch of chestnuts in May 2022 at Shagbark was below 18% moisture, when the flour was quickly refrigerated after milling, moisture picked up from the high humidity the day of milling concentrated moisture in a small portion of the bag, raising the moisture levels in above the 18% threshold.

In contrast, when Amy Miller took samples back to Route 9 Cooperative from the same milling run, they sat out for a few days before storing them in the fridge which allowed the bags to fully cool and dry before refrigerating. 

Regarding mycotoxins in mold, Greg Miller did extensive mycotoxin sampling during his original milling work in the early 90s and at an Iowa State University lab and found no mycotoxins in his samples considered consumable.

Brian Jacobson, Associate Director of Strategic Operations at University of Illinois at Urbana-Champaign is partnering with a PhD candidate Vince Yang to analyze the properties of a mix of chestnut cultivars and offered some advice about dehydration techniques. Using an airflow dryer, they aim to reduce water activity below 0.6 at least, or similar to the wheat flour. However, Amy Miller points out that individual chestnut kernels have very non-uniform drying patterns compared to other grains so the average moisture level of the "batch" doesn't necessarily match the moisture level of any individual kernel. Therefore, she says, “even if nuts are all dried in the same conditions, after four weeks we'll find some kernels so dry that they shatter and others that are still spongy and chewable.” This inconsistency makes it difficult to develop and scale up drying equipment.

Research results and discussion:


chestnut milling
  Map of milling cooperators.

5/13/22 Shagbark Seed & Mill Chestnut Milling

Our first milling day took place at Shagbark Seed & Mill in Athens County on May 13, 2022. We split 140 lbs of chestnut chunks into two milling groups: 800 micron screen and 450 micron screen. A micron, also called a micrometer, is the metric unit of measurement for 0.001 millimeters. It is used here to refer to the diameter of the milled material, so the greater the amount of microns, the larger the particle size. 

Trial Micron size Start weight Total yield Flour yield % flour yield
1 800 micron 70 lbs 63.4 lbs 52 lbs 74%
2 450 micron 70 lbs 68.82 lbs 25 lbs 36%

We then bagged the milled flour (77 lbs) and distributed it to eight local bakers and chefs who produced a range of products including sourdough bread, baguettes, and cake.

Shagbark Seed & Mill Production Manager Joe Beres operates the mill.
Chestnut Flour
Chestnut flour sampling.

8/23/22 Walnut Creek Seeds Chestnut Sifting

Amy Miller brought sifted combination chestnut flour and a 1cm screened polenta grade chestnut flour to sift at Walnut Creek Seed in Fairfield County. 25.8 lbs of the sifted flour was sifted through a 100 mesh screen to produce 6.85 lbs of ultra-fine flour. The remaining 31.9 lbs of sifted flour was sifted through a 40 mesh screen to produce 20.15 lbs of fine flour. The polenta grade chestnuts were also sifted through the 40 screen to produce 3.8 lbs of fine flour. Total yield was nearly 100% for all the trials on account of the large amounts of ‘leavings’ that remained leftover from the screened flour. These leavings are a coarser grade similar to grits.

Mesh size refers to the number of openings in one inch of screen. For example, an 800-mesh screen means that there are 800 squares within one inch of the screen. As the mesh size increases, the particle size decreases to create a finer milled product (opposite of micron size).

Trial Mesh size Start weight Total yield Flour yield Leavings yield % flour yield
1 100 mesh 25.80 lbs (sifted combination flour) 25.80 lbs 6.85 lbs 18.95 lbs (fine leavings) 27%
2 40 mesh 31.90 lbs (sifted combination flour) 31.85 lbs 20.15 lbs 11.70 lbs (coarse leavings) 63%
3 40 mesh 27.50 lbs (1cm screened polenta) 27.45 lbs 3.80 lbs 23.65 lbs (ultra-coarse leavings) 14%


Chestnut flour
Sifting chestnut flour.
Chestnut flour
Amy Miller of Route 9 Cooperative chats with Walnut Creek Seeds owner Jay Brandt and employee.
Chestnut flour
Amy Miller shows dried whole chestnuts.
Chestnut flour
Bagged chestnut flour.

12/2/22: Stutzman Farms Milling and Sifting

Amy Miller of Route 9 Cooperative met us at Stutzman Farms in Holmes County, Ohio to mill 60 lbs of whole chestnut into culinary flour. The whole chestnuts were first run through a burr mill to break into large chunks then milled to make smaller chunks some of which were subsequently put through the third mill to produce a fine flour. 

Stutzman milled the fine flour for a cost of $0.75/lb. The other 20 lbs he milled into coarse pieces with the steel burr mill (either 1x or 2x through the mill) at a cost of $0.25/lb. Those 20 lbs were divided into samples of different sizes: Steel burr mill 1X, Steel burr mill 2X, Steel burr mill and Roller mill (settings 1 & 2 on the roller mill). He reported that the moisture in the chestnuts caused the chunks to get lodged in his mill. Stutzman explained that to achieve the fine flour, the chestnuts had to be run three times. Per advice from Amy Miller, he used a pencil dryer to reduce the amount of moisture prior to milling. 

A range of chestnut flour was sent to Michell’s Ice Cream (Cleveland) and Jeni’s Splendid Ice Cream (Columbus) for sampling. Remaining samples were distributed to local bakers and chefs to produce products for our OEFFA presentation.

Chestnut flour
Stutzman Farms mill.
Chestnut flour
Chestnut samples after the roller mill.
Chestnut flour
Finely sifted chestnut flour.


Recipes: To better aid our research, we distributed a variety of flour types to bakers, chefs, and brewers from our region and beyond to experiment and provide feedback.

chestnut flour
Sourdough chestnut flour bread loaf made by Athens Bread Company.
chestnut flour
Chestnut flour crust made by John Gutekanst of Avalanche Pizza.
Chestnut cranberry scones made by Village Bakery & Cafe.
chestnut flour
Chestnut pretzel buns made by Village Bakery & Cafe.

Participation Summary
4 Farmers participating in research

Educational & Outreach Activities

4 Published press articles, newsletters
1 Tours
2 Webinars / talks / presentations
1 Workshop field days

Participation Summary:

8 Farmers participated
18 Ag professionals participated
Education/outreach description:

Field day: Our Chestnut Field Day held at Route 9 Cooperative on September 30, 2022, garnered more than 20 attendees from across the state to learn about the grant research, tour the processing facility, and test the value-added chestnut flour products made by local chefs and bakers. We are in the process of planning our second field day which will take place in September 2023.

Event agenda:

  • 2-2:15pm: welcome and food introduction
  • 2:15-3pm: slide presentation and questions
  • 3-3:45pm: facility tour
  • 3:45-4pm: questions and close

Participants had the opportunity to sample chestnut products from Village Bakery, Athens Bread Company, Avalanche Pizza, and the Athens Asian American Alliance.
Participants had the opportunity to sample chestnut products from Village Bakery, Athens Bread Company, Avalanche Pizza, and the Athens Asian American Alliance.
Amy Miller demonstrates the impact sheller.
Amy Miller demonstrates the impact sheller.
Greg Miller describes his early work with chestnuts.
Greg Miller describes his early work with chestnuts.
Amy Miller demonstrates how chestnuts are cleaned and processed.
Amy Miller demonstrates how chestnuts are cleaned and processed.

Promotion: Our grant research and field day event was promoted through ATTRA, Morning Ag Clips, OEFFA, and featured in Cleveland’s WKYC news.

Within Rural Action’s network, our research was also highlighted in three newsletters including the Staple Pulse, Rural Action's Sustainable Agriculture and Forestry Newsletter, and Rural Action's Rural Rambler Newsletter, cumulatively reaching 8.4k readers.

Future Outreach: We recognize the importance of promoting our work beyond Rural Action’s social media accounts to ensure outreach continues beyond the grant timeline. To that end, we will be assisting Route 9 Cooperative with creating and maintaining an active social media presence in the second year of the grant.

We also connect with food manufacturers and distributors to promote sales to food service customers. Finally, we plan to seek out venues and events that will feature chestnut flour and pancake mix to the general public.

Presentations: We began planning our OEFFA (Ohio Ecological Food & Farm Association) Conference presentation slides, outreach and collaborations with local bakers for the event in February, 2023. We will include that event and others in our final report. 

Field day promotional image.
Field day promotional image.
Collage image of milled chestnut ice cream.
Collage image of milled chestnut ice cream.

Learning Outcomes

6 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation

Project Outcomes

Project outcomes:

Project Outcomes

We’ve connected with a number of chefs, bakers, brewers, and retailers to increase the economic opportunities of value-added chestnut products. Our goal is to create interest in the prospect of purchasing course and fine flour, as well as chunks that can be used as ingredients in new menu items. Route 9 saw an increase in sales after we distributed chestnut flour samples to chefs.

  • Monroe Stutzman of Stutzman Farms purchased 100 lbs of chestnut chunks from Route 9 Cooperative after collaborating on the grant. He plans to mill the chestnuts into flour to sell at his facility in Millersburg, OH.
  • Andrew Luxmore of Blue Hill at Stone Barn purchased just over 100 lbs to use in research and development for Blue Hill restaurants in NYC and at Stone Barns Tarrytown, NY in December 2022.  Specifically, they ordered 20 lbs fresh chestnuts in shell, 10 lbs fresh peeled kernels, 5 lbs dried kernels, 60 lbs fine flour; and received a sample of 10 lbs coarse flour Route 9 Cooperative. They produced a chestnut butter and tart shell for the restaurant.
  • Alex Rinehart of Fibonacci Brewery out of Cincinnati purchased 22 lbs of coarse chestnut flour to experiment with chestnut beer. Alex and Amy discussed  particle sizes for brewing. He'll let us know if the coarse flour is good, or if we need to adjust one way or another

Tree crops, specifically chestnut trees, offer a range of ecological benefits including carbon sequestration, soil stabilization, and opportunities for alley cropping. In Appalachia, small, irregular plots with acid soil types are well suited to chestnut trees. By increasing market interest in culinary chestnuts and standardizing milling methods, our work incentivizes farmers to incorporate chestnut trees amongst existing crops and even creates viable alternatives to traditional row crops.


Reducing moisture: Route 9 found the pencil dryer to be too large for the batch sizes they would prepare for milling. In the remaining year of the grant, we will: 

  • Reassess the pencil dryer as a viable addition to their equipment in conjunction with the 2023 fall harvest
  • Reach out to mechanical engineering programs at Ohio University and Ohio State to explore the possibility of fabricating a smaller dryer. 
  • Explore the possibility of using one of the local coffee company’s coffee roaster for smaller batches. 

 We will be including additional recommendations in our final report next year. 

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.