Postharvest Resource Survey

We are seeking input regarding a research and education project with the goal of consolidating postharvest information in a single set of resources.

Our proposed project aims to consolidate existing knowledge, best practices, and new developments in postharvest equipment, infrastructure, and buildings into a web-based handbook, workshop curriculum / educational materials and recorded videos.

Click here or on the picture to take the survey! 

This survey is voluntary and anonymous. Summarized and anonymized results will be included in a grant project proposal and also on our website ( Please direct any questions to Chris Callahan,, 802-447-7582 x256.

The survey should take an average of 3 minutes to complete.

Thanks for your help.

Finding a Better Way: Engineering on the Farm (Podcast)

Check out episode 10 of this podcast with Chris Callahan, and Trevor Hardy from Brookdale Fruit Farm talking about engineering on the Farm! Full series available on iTunes.

The Our Farms, Our Future podcast series brings together the sustainable agriculture community for thought-provoking conversations about the state of agriculture, how we got here, and where we’re headed. With each episode, we hope to share different perspectives within the sustainable agriculture community while tackling such topics as building resilient farming systems, farm profitability, and fostering community through local food systems.

This series is being produced in conjunction with the Our Farms, Our Future conference, held in April 2018 to coincide with SARE’s 30th anniversary.

For this episode, two agricultural engineers discuss adapting innovation on the farm.

Trevor Hardy is manager of one of New England’s largest distributors of agricultural supplies at Brookdale Fruit Farm in Hollis, New Hampshire. Chris Callahan is an agricultural engineer with University of Vermont Extension. Both guests say engineering plays a crucial role in synthesizing the newest research and technology with the diversity and complexity of farming practices on the ground.

Click the image to open the podcast page, and listen to Episode 10!

DewRight Debut: From Product to Patent

This video is an episode from Across the Fence! It holds an interview with Judy Simpson as well as a description of the product.

The video below highlights the 9min segment specifically talking about the DewRight.

Read the write up from Vermont Business Magazine here.

Read the press release from UVM’s University Communications here.

Upcoming Produce Safety Training (November 6-7, 2017)

The Vermont Agency of Agriculture and UVM Extension are co-sponsoring a VT-Style Produce Safety Alliance (PSA) Grower Training on Tue-Wed, November 7 & 8, 2017 (8:30am – 5:00pm) at the VYCC Monitor Barn in Richmond, VT. This is the official required training for FSMA covered farms (Click here to determine whether your farm may be covered or exempt).

The $30 heavily subsidized training fee includes the massive training manual, multiple meals, ample coffee, and the Association of Food and Drug Official (AFDO) certificate (a $130 value—not including space rental or instructor fees!). The AFDO training certificate satisfies FSMA Produce Safety Rule training requirement.

EVERYONE is invited: Regardless of scale, annual sales, or market outlets, all produce growers can benefit from learning about integrating practical produce safety practices on a working produce operation. Technical assistance providers, educators, and regulators are also invited and will benefit from this training. Whether you are a covered farm fully subject to Produce Safety Rule (PSR) regulations, or an exempt farm required to keep certain records related to your exemption, all aspects rule compliance will also be covered during this training.

The Training Schedule at a glance:
Day One (November 7, 8:30am–5:00pm) will provide an introduction to the FSMA Produce Safety Rule, employee health, hygiene and training requirements, and information about management of soil amendments as well as domesticated animals and wildlife. Includes on-farm exploration to apply concepts in the field.
Day Two (November 8, 8:30am–5:00pm) will cover agricultural water, postharvest handling and sanitation, and writing produce safety plans. Includes on-farm exploration to apply post-harvest concepts.

View more details and registration visit:  PSA Training Registration via Regonline

2013 VVBGA Annual Meeting

I had the pleasure of joining the Vermont Vegetable and Berry Grower’s Association yesterday for their annual meeting.  This event is packed with presentations ranging from the latest pests to farmer outreach in distant lands.

My talk was on crop storage, and it was a great chance to summarize my recent work in this area.  I’ve been fortunate to have worked closely with several growers in this area including Isaac Jacobs and Pete Johnson of Pete’s Greens, Jon Satz of Wood’s Market Garden, Andrew Knafel of Clearbrook Farm, Howard Prussak of High Meadows Farm, and Jeremy Gildrien of Gildrien Farm. I’ve also benefited from conversations with Jim Thompson and the resources he helped create at the UC Davis Postharvest Technology Center.

The presentation slides are available at the VVBGA’s website. I’m still very grateful for the responses to the food storage survey, and we discussed these at the meeting.  I also highlighted 5 things I think are critical considerations for VT growers storing vegetables and berries.

  • Zoned Storage – While many are zoning (or grouping) their stored products based on optimal temperature and relative humidity (RH), it is also important to consider a zone for pre-cooling product as it comes into storage. The sudden addition of product with field heat and elevated respiration can contribute significantly to the cooling load in the room and could lead to slightly warming other crops already in storage.  Additionally, we talked about the need to consider ethylene production of crops and also their sensitivity to it; sometimes requiring outside air exchange to remove the ethylene.  Most are familiar with ethylene production from apples, but even common vegetable crops also produce some. Storage conditions for main crops as well as respiration rates and ethylene emission rates can all be found in USDA Handbook 66.
  • Measurement and Monitoring – It is understandable that one should expect a cooler to be at the temperature you set on the thermostat.  But I’m a believer in secondary, accurate measurement to confirm storage conditions.  This means both temperature and RH.  I urge growers to check it regularly (daily), and to keep track in some sort of log so that trends are captured.  This can take the form of an advanced remote data monitoring system, but it can also take the form of a simple clipboard or notebook.  The important thing is that the conditions are actually measured with an accurate device such as a certified and calibrated thermohygrometer or sling psychrometer and be recorded. Here’s a video showing how to use a sling psychrometer (equally useful in a greenhouse or cooler, although I recommend “slinging” for 1 minute or more, taking 3 readings to check for stability, and using a psychrometric calculator to determine RH as the slide calculator on the device is not terribly accurate.)

  • Scouting – Despite all the best intentions; zoning your storage and confirming the conditions, sometimes you still run into problems.  There are varietal differences in storage and many other factors that will influence how the crops keep in storage.  So it is important to “scout” the storage as well.  This can be daunting with bins and boxes piled high, but catching a problem early could help prevent a major loss.  It is possible, as well, that you have to deviate from the published references for storage conditions for a certain crop.  The verification of the storage conditions is the measurement step above, but the validation is the crop quality.  The proof is always in the pudding.
  • Cooler Audits – It is hard to make time to stop and smell the roses, and it is hard to take time to stop and audit your cooler. But there are things you can do on a routine basis that take little to no additional time.
  • Check Door Seals – Walk inside the cooler, shut off the lights and look around the door for daylight.  If you find spots with light shining through look more closely at the seal in that area, it may need repair or replacement.  Look also for frost (on freezers) or condensation (on coolers) which can also be signs of air leakage.
  • Door Closure Tightness – Even if your seals are in good condition, the door must shut snugly to have them work.  Most commercial cooler doors have adjustable latches.  Make sure there is no play in the latch when the door is closed, and adjust as needed so it closes tightly.
  • Mold, Condensation – Keep an eye out for mold and/or water condensation, this may point to air circulation issues or dead spots of air flow that need to be addressed.
  • Noise – Noise is energy, and if you get to know the typical “hum” of your compressor and fans, you’ll be able to tell when something is amiss.  New noises or more frequent operation of the compressor can signal a significant change in the refrigeration system (a higher than normal load, or heavier work than normal.) Keep an ear out for new noises and do a complete walk around on a regular basis to catch maintenance issues early.
  • Coil Cleaning – The air coils are the lungs of the system, and they need to be clear of debris.  Regular coil cleaning should be added to any preventative maintenance or seasonal job list.  If your system can’t reject heat (either inside the box or outside the box), you’re not cooling as effectively as you could.  This definitely means reduced efficiency and increased energy use, but it could also mean reduced storage efficacy and premature spoilage.
  • Mechanical Maintenance – A trained mechanical contractor should inspect your system on a regular basis (yearly prior to your main storage season). This will help minimize the chances of system failures and (worse) crop loss.
  • Technical Resources – There are several excellent resources available on crop storage.  The New England Vegetable Guide is an excellent overall crop guide that includes basic storage information.  To dive a bit deeper, look at the USDA Handbook 66, note that the online edition has increased detail than the last print edition. I also recommend the UC Davis Postharvest Technology site which has a wide array of searchable resources, many of which are crop specific. If you get real deeply involved in environmental control (temperature and humidity), you might want to learn more about psychrometric charts and calculators.  These allow you to very accurately understand the relationship of water vapor and air and are especially useful when used with a sling psychrometer.


Remote Data Monitoring – 1st Install at Pete’s Greens

As an engineer, I love data.  It turns out farmers do also.  At least, Pete Johnson and Isaac Jacobs at Pete’s Greens in Craftsbury, VT do. “Is it working yet?” Isaac asks as I put the finishing touches on the remote data monitoring system we have been installing in the four zone drive-in cooler. “Just about… I think.” I say with trepidation. Isaac has been up and down in a scissor lift several times at placing and removing a sensor that was being difficult. And I’ve been wrestling with a data station to make it communicate over the wireless network so that we can actually see the data being collected by the new remote monitoring system.

Installing Remote Sensor in Cabbage Room
Isaac Jacobs of Pete’s Greens (Craftsbury) installs a remote temperature and relative humidity sensor in the cabbage room of the farm’s cooler.

This is the first time we’ve installed this kind of system which consists of a “base station” and “remote sensors”.  The remote sensors in this case measure temperature and relative humidity (RH), both parameters which can drastically influence the storage life, quality and food safety of produce.  In fact, the motivation for multiple storage “zones” in the cooler is to provide each group of vegetables their desired set of conditions; e.g. potatoes at 38 °F and 90-95% RH, onions at 32 °F and 65-70% RH, cabbage at 32 °F and 99% RH and squash at 55 °F and 70% RH.

Setting up the Data Logger
The items to the left of the laptop are the remote data logging system. Each of the five sensors can measure temperature and relative humidity over a wide range and report it back to the base station which uploads it to a website for review. Alarms can be set to alert users via email if conditions exceed high or low limits.

“What are those spikes in temperature?” Pete asks as we glance over the first set of data that pops onto the screen.  There are spikes in temperature every 8 hours in the potato room that last about one hour.  Not big spikes (2 °F above the nominal), but they stand out.  And perhaps as important, relative humidity drops by 2% when the temperature goes up.

Later, when Isaac and I are looking at the electrical wiring to see where we can plug in additional sensors we note that evaporator defrost system in that room is on an 8 hour timer; that’s the source of the heat.  “Well, they don’t even need to be on right now, that room isn’t even being cooled.” The circuit breakers for the evaporator heaters (intended to defrost the evaporator when it freezes up) are shut off, reducing the farm’s electric bill slightly over the next few months. And this is only two hours after we started getting data.

The power of data is three-fold.  First it is inspired by inquisition. It then raises additional questions and with further review, it should answer questions and improve life.  The principle behind this project is to allow for easier access to process data for Vermont’s growers and to demonstrate this type of system. As farms push the seasonal envelope in response to increased local demand, year-round production and long term storage of fruits and vegetables will be increasingly important. I plan to use this system at multiple locations in Vermont to collect data on refrigerated storage, greenhouse and high tunnel production, and whatever else comes along that is interesting and makes sense.

VPR Series on VT Food – All Week on Morning Edition

Visit VPR’s site to listen to archived episodes.

“VPR looks at the economic impact of food production in Vermont in the special series The Business of Food.

All this week during Morning Edition, we’re looking at the expansion of farmer’s markets from a summer calendar schedule to a year-round operation, how community planners in southeastern Vermont say it’s time to go beyond co-ops and plan for a “post-oil” world, how “farm to plate”initiatives have resulted in good social policy and how downtown planners are using food co-ops as a lure to enliven central business districts.

Listen this week at 7:50 a.m. during Morning Edition.”

The Start of Something New

As you may know, UVM Extension has initiated an Agricultural Engineering program and I am so pleased to have been selected to lead it. My job is to conduct research, technology development & transfer, applied engineering, education and outreach to support the development and enhancement of Vermont’s small-scale food and agricultural systems.

I’m incredibly excited to have this opportunity to support Vermont’s food systems and to continue working with farmers and other agricultural professionals throughout the state and beyond.

Some of the specific areas I expect to focus on initially include greenhouse energy efficiency, renewable fuels, post-harvest fruit and vegetable processing, enhanced refrigeration, and application of control technologies to food production. But I am very interested in hearing what technical challenges you think are most critical to you. If you have a moment, please send me your thoughts on where you think the most significant technical challenges are in your operation. My complete contact information is provided on the left hand side of this site.

The right hand side of the site includes links to some of my favorite references and calculators which may be useful for you as well. If you run into problems with any of them or have additional questions, let me know. Or if you have ideas for references or links that I should include, let me know that as well.