Farmer-Built Grain Pearling Machine

Final report for FNE19-945

Project Type: Farmer
Funds awarded in 2019: $14,748.00
Projected End Date: 12/31/2022
Grant Recipient: Weatherbury Farm
Region: Northeast
State: Pennsylvania
Project Leader:
Nigel Tudor
Weatherbury Farm
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Project Information


I built a small scale 10hp grain pearling machine that is capable of operating on the electrical service of most small farms. I designed the machine in CAD (Fusion 360), constructed my design and ran some grain pearling trials. I also studied using pearling to reduce the vomitoxin content of small grains with elevated vomitoxin. The machine pearls grain and also reduced the vomitoxin in wheat from 6.5ppm to 1.1ppm. The plans for this machine will be available through SARE and Dr. Elizabeth Dyck / Organic Growers Research and Information-Sharing Network. It is my hope that farmers around the world will build similar machines.

Project Objectives:

This project seeks to build a small farm-scale pearling machine. The pearling machine will have a theoretical throughput of 1,000lbs of grain per hour.  I will design the machine in CAD so that when I am finished plans will be available for other farmers to build their own pearling machines. Once construction of the machine is finished, I will test it with several different small grains. I intend to figure out the settings to partially pearl grain in one pass and fully pearl grain in 2-3 passes.  I will also work with project advisor Dr. Elizabeth Dyck to get grain that has elevated DON levels and pearl it to different levels. The grain would then be sent out for testing to benchmark the potential for DON reduction.


Pearled grains are used commonly in cooking but machinery doesn't currently exist to do this on a small scale. The goal of this project is to develop a small scale pearling machine that can be run on most farms. Local pearled grains would be a unique value added product.

  • Lightly pearling grain reduces the cooking time.
  • Pearling also shows promise as a way to reduce DON content in grains and help farmers be able to market higher DON grains.

Locally grown pearled grains is an untapped market in North America. The advantage of lightly and fully pearled grains is that they cook quicker than whole grain berries. For example, cooking time for emmer can be reduced from 45-50 minutes for un-pearled grain to 15-25 minutes for semi-pearled grain. The downside of bran removal is the loss of the nutrients contained in the bran. Partial bran removal retains some of these nutrients while still reducing cooking time by 50-66%. Grains that could be sold partially or fully pearled are wheat, rye, barley, spelt, emmer and einkorn.

The pearling machine could also be used to dehull barley to produce a food-grade product (no small-scale farm machines currently exist to do this task). Whole barley can currently only be used for malting and feed.

For small farmers to create pearled products from the grains that they are growing, they need a scale- appropriate machine to do the pearling. One of the biggest challenges for small farmers is having adequate power to run a pearling machine. The smallest machines that I have found are 15KW (20hp) that are built in Italy and China.

A serious problem of growing small grains in the Northeast is Vomitoxin/DON. Food-grade grain has to be under 1ppm DON. The threat of vomitoxin always hangs over farmers’ heads in the Northeast. The wet climate of the Northeast is much more conducive to vomitoxin contamination of grains than the drier climate of the upper plains. The ability to pearl grain would allow a farmer to manage DON in their crops.  Vomitoxin/DON is primarily located in the bran. Pearling would remove the bran, either in whole or in part (depending on the level of DON). The ability to remove the bran and reduce DON would allow farmers to ”save” grain that otherwise would not be under the 1ppm DON food-grade limit. Unlike conventional farmers that can apply fungicide to wheat, organic farmers don’t have any management tools other than crop rotation to minimize DON levels in their small grains. The ability to pearl grains and remove bran thus reducing the DON on a crop would give organic grain farmers in the Northeast a powerful management tool.

Thus, the opportunity a grain pearling machine offers is twofold:

The market for pearled grains is virtually untapped in the USA and offers a huge value-added opportunity. To educate consumers, information about pearled grains would be spread through press releases, as well as our website, email newsletters and Facebook. Additionally, information about pearled grain opportunities would be spread to farmers through field days and regional conferences.

In addition to opening up a potential value-added market, the pearling machine can be used to manage DON levels in grains, a major risk factor for small grain production in the Northeast.



Description of farm operation:

Weatherbury Farm has been operated by the Tudor family for 37 years. It raises grass-fed beef, grass-fed lamb, organic grains and mills those grains into flour. The primary focus is added value production and selling directly to consumers.


Click linked name(s) to expand/collapse or show everyone's info
  • Dr. Elizabeth Dyck - Technical Advisor (Educator and Researcher)


Materials and methods:

I designed the pearling machine in CAD (Fusion 360) and constructed the machine. The result is a machine that pearls grain which only uses 10hp which would be able to be operated on most small farms. My goal was to design a machine that was easy for one person to operate and easy to clean out between product types. 

I also explored using pearling to reduce the vomitoxin content in small grain.

Research results and discussion:

I built a small-scale grain pearling machine that only uses 10hp. Commercial machines use 20 -150hp which cannot be run on most farms. The primary focus of the grant was the design and construction of the pearling machine. The plans for the machine will be available in .dwg and .pdf format; there is a 62 page construction manual available for anyone interested in building the machine.

Unlike my previous spelt dehuller SARE Grant where I was able to look at many different spelt dehullers in person, I only know of one pearling machine in the Northeast which is a vertical design at Maine Grains and not really applicable (additionally, it was not at Maine Grains when I was there in 2013). My design was influenced by one Italian machine and 2 Chinese machines. I also looked at rice polishing machines which are a close cousin to pearling machines.

Considering that I had no machine to see in person and to act as a pattern, my machine runs well and is able to pearl grain. There are some modifications that I plan to make. The discharge door needs to be actuated manually to keep the machine’s motor in the correct amperage range. I plan to make some modifications that should allow this discharge door to function without constant supervision. Commercial pearling machines use slotted screens. As a result of supply chain issues, I ended up using a commercially available .078” round perforated screen. I purchased punches to make the screens for the pearling machine but their delivery was delayed. I plan on making 2 sizes of slotted screens for my machine and trying them out. I will let anyone know who contacts me what improvements I have made to my machine.  

Because the weather in December is variable I decided to hold off painting the machine before I used it as I didn’t want to be stuck waiting for warm enough days for the paint to cure properly. In the spring I will sand blast and paint the machine and put it in my mill room.

The biggest impact of having a grain pearling machine will be the ability to create additional products from the grains I am already growing. Here is a chart of the names of pearled products made from some of the common small grains.

Grain Lightly Pearled Full Pearled
Barley Pot Barley Pearled Barley
Emmer Faro Medio (common Faro)  
Spelt Faro Grande  
Einkorn Faro Piccolo  
Wheat   Frumenty

Lightly pearled grain and full pearled grain take less time to cook than raw grain berries.

I used the pearling machine to explore the possibility of reducing vomitoxin in small grains. My advisor Elizabeth Dyck helped me secure some high vomitoxin samples. These were cleanings from grain that had a special cleaning process to reduce vomitoxin in the grain but the cleanings were high vomitoxin.  Before starting I took a baseline sample. About 1/3 of the way through each pass I took sample A and 2/3 of the way through I took sample B. I ran the grain through the machine 3 times.  There is a definite reduction in vomitoxin. Possibly a 4th run would be merited. Further testing is needed to figure out the best methods for vomitoxin reduction.


Vomitoxin ppm Test Identification
2.5 Rye Baseline
0.9 Rye 1A
1.2 Rye 1B
1.6 Rye 2A
1.3 Rye 2B
1.3 Rye 3A
0.9 Rye 3B

Hard Red Spring Wheat

Vomitoxin  ppm Test Identification

HRSW Baseline

4.1 HRSW 1A
2.7 HRSW 1B
3.0 HRSW 2A
2.7 HRSW 2B
1.1 HRSW 3A
1.1 HRSW 3B
Research conclusions:

My goal was to design and build a small pearling machine with a 10hp motor that would be capable of operating on the electrical service of most small farms in the USA. I designed the machine in CAD and have made extensive plans (103 pages) which will be available. There is also a 62 page construction manual available. In the spring I plan to paint the machine and start using it. The pearling machine will allow me to create several new products from the grains I am already growing.

I also explored the possibility of using a pearling machine to reduce the vomitoxin content in small grains. There was a definite reduction in vomitoxin. Further testing will need to be done to find the best practices and best process for using pearling as a means of vomitoxin reduction.  Reducing vomitoxin could be of great importance to small farms in years when there is a lot of rain, thus making the grain susceptible to vomitoxin --- and unsaleable for the food market!

Participation Summary
1 Farmers participating in research

Education & Outreach Activities and Participation Summary

1 Curricula, factsheets or educational tools

Participation Summary:

1 Farmers participated
1 Number of agricultural educator or service providers reached through education and outreach activities
Education/outreach description:

I plan to have a field day and have a page on my website devoted to this project and previous SARE projects. Already there is a farmer who is interested in seeing the machine in operation and potentially building one for himself. I will be talking at the 7th February Hudson Valley Value-Added Grain School. At the grain school I will be talking about dehulling grain, rolling grain and will also talk about pearling grain including this SARE project. 

I have put together a 62 page Construction Manual. I will be sending copies of the plans in .pdf and .dwg format to both SARE and Dr. Elizabeth Dyck who will share the plans with interested farmers. The manual and plans are available ain .pdf format under this project's information products.


Learning Outcomes

1 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key areas in which farmers reported changes in knowledge, attitude, skills and/or awareness:

Farmers have already noticed this and are eager to come and see the machine in operation.

The initial tests show that this machine is effective at reducing vomitoxin but more tests are needed. Prior to this organic farmers have not had a means of controlling vomitoxin in their small grain crops.

This machine’s design allows small farms to pearl grain, creating additional value added products from grains they already grow. Since this technology wasn’t available to small farms, it was not something that farmers previously considered.  

Project Outcomes

1 Farmers changed or adopted a practice
1 Grant applied for that built upon this project
1 Grant received that built upon this project
$14,748.00 Dollar amount of grant received that built upon this project
Project outcomes:

Pearled Grains will likely be the next big thing in the local value-added grain scene. Pearling will allow farms to offer additional products without having to grow additional crops. This means that farms currently doing on farm value added grain production will be able to add value to more of their crop by offering additional products.

I plan to paint the pearling machine and start using it in early 2023.

For consumers the advantage of pearled grains is the quicker cooking time compared to grain berries.  Additionally, farro by definition is lightly pearled emmer, einkorn and spelt.  What is sold in this country as farro, is often unpearled grain berries.

Using pearling to reduce vomitoxin has the potential to allow some crops that have too high of a vomitoxin level to be able to be marketed as food grade. This is especially valuable with heritage or specialty grains that may not have a secondary market (i.e. feed).

Assessment of Project Approach and Areas of Further Study:

Even though outwardly the pearling machine looks fairly simple, there are a lot of parts that took a long time to design and fabricate. I wasn’t able to look at a machine in person and only had a couple of pictures and spec sheets that I found on the internet. This meant I had to spend a good deal of time thinking about how every part would function and how it would interact with other parts.

One of the biggest challenges was finding time to work on this project. In 2020, 2021 & 2022 I seemed to be busier than previously. Another problem endemic to this time period was supply chain issues. I couldn’t always get what I wanted in a timely fashion or at all. An example of this is the electrical components some of which had up to a 16week lead time so I turned to eBay to buy new old stock items.

The end result is a functional pearling machine. In my construction manual I list both changes I am planning on making to my machine and potential modifications to the design that the next person might consider making to their machine.

 As it was a dry year in the Northeast, my project advisor had trouble finding high vomitoxin grain samples. We did find rye and hard red spring wheat cleanings that both had high vomitoxin. The results show a decline in vomitoxin by the 3rd pass. Further research will need to be done to figure out the limits and best practices when using pearling to reduce vomitoxin. 

I expect that as with my SARE compost turner and, especially the spelt dehuller, I will be in contact with farmers from all over the world, many of whom eventually will build the machine and make their farm more sustainable.

Information Products

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.