UVM Extension Ag Engineering


UC Davis Guide: Small-Scale Postharvest Practices

This guide from the UC Davis Postharvest Center is jam packed with information relevant to VT’s small-scale growers seeking improved post-harvest handling and processing. I think it is a nice companion to the New England Vegetable Management Guide and USDA’s Handbook 66. The UC Davis Postharvest Center has a wonderful on-line library with many other titles which may be of interest including an overview of small-scale cold room options and one on root cellars and other passive storage options.

One question that seems to come up regularly is “how big a cooler do I need?”  I’d recommend grower’s review Table 7 in Heatcraft’s Engineering Manual which includes typical “product loading densities” in pounds per cubic foot.  Based on your typical yields and acres in production you can use this to estimate a reasonably sized storage space.

“The three main objectives of applying postharvest technology to harvested fruits and vegetables are:

  1. to maintain quality (appearance, texture, flavor and nutritive value)
  2. to protect food safety, and
  3. to reduce losses between harvest and consumption.

Effective management during the postharvest period, rather than the level of sophistication of any given technology, is the key in reaching the desired objectives. While large scale operations may benefit from investing in costly handling machinery and high-tech postharvest treatments, often these options are not practical for small-scale handlers. Instead, simple, low cost technologies often can be more appropriate for small volume, limited resource commercial operations, farmers involved in direct marketing, as well as for suppliers to exporters in developing countries.”

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.”

Food Storage Survey Results

Thanks to all of those who took the time to respond to the food storage survey several weeks back.  The information you provided has been really helpful.  A clear desire for additional programming in this area was expressed, and I’ll be working to develop that.

Here are the survey result highlights:

  • 82% of respondents expressed interest in a formalized course on food storage topics with the overwhelming majority preferring classroom / workshop format and/or a webinar.
  • 66% of respondents have plans to expand your food storage capacity in the next 24 months.
  • While most respondents expressed concern about the utility costs of their storage systems, relatively few (37%) currently know those costs.
  • 60% are storing in multiple zones (Temp and RH), but the overall knowledge of optimal storage conditions is relatively low (see related post on USDA Handbook 66).
  • Winter markets included (% reporting sales to each)
    • Wholesale (74%)
    • Retail (41%)
    • Farmer’s Markets (41%)
    • Winter CSA (38%)
  • The most common systems in use are (% reporting use):
    • Walkin cooler (57%)
    • Chest freezers (55%)
    • Heated Winter Storage (39%)
    • Root Cellar / Other Cool Storage (not refrig’d) (31%)
    • CoolBot(TM) (28%) – CoolBots(TM) website
    • Walkin freezer (16%)
    • Other cooler refrigerated (16%)
  • Other areas where respondents expressed interest in learning more included:
    • basic refrigeration principles / fundamentals
    • equipment overview
    • construction how-to
    • general post-harvest handling best practices
    • insulation trade-off / bang for your insulation buck
    • building in resilience / what happens when the power goes away?
    • making better use of cold winter air and thermal storage
    • how to best segment a walkin / zoning the storage space
    • short vs. long term storage practices
    • economics; what is this actually costing me now and in the future?
  • When asked about their own lessons learned, respondents noted:
    • Get field heat out quickly and keep it cold
    • Excellent storage is key to having excellent product
    • Insulate, insulate, and then insulate some more
    • Measurement of temperature (and RH) is critical, don’t assume you are hitting your target conditions
    • Watch out for ethylene off-gas from, e.g., apples
    • Climate change is impacting harvest timing and therefore marketability and storage needs
    • Plan for power loss
    • Insure your product for loss while in storage
    • Build bigger than what you presently need. Coolers and freezers are quickly outgrown.
    • Consider “keeping it on the hoof” instead of harvest and storage.
    • Pre-sell – grow only what you know you can sell – Sales and product movement are critical.  Do the pre-planning.

Efficiency Vermont Incentives for Agriculture

Efficiency Vermont Logo




Are you considering any equipment upgrades in the near future.  Check Efficiency Vermont’s webpage to research available technologies and to see if any of their many incentives apply to you. They have a set of rebates specific to agriculture and some for commercial refrigeration which may apply to folks with refrigerated storage on their farm.  Been thinking about an outside air economizer to take advantage of the chilly winter air in your walk-in?  Check out the rebates.  They even have some programs focused on heating, ventilation and air conditioning systems which may apply to greenhouse heating with a pellet furnace or boiler. Want to learn more about Efficiency Vermont, including where the money comes from? Read on…

USDA Handbook 66 – Fruit, Berry and Vegetable Storage Guide

USDA Handbook 66The USDA regularly produces its Agricultural Handbook 66 – “The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Stocks” to help guide long term storage of these products. The handbook is dense with info on optimal storage conditions for everything from Jerusalem Artichokes to Watercress. Each crop is given a brief overview which summarizes the expected loss when stored at certain conditions and also a summary of respiration rates to help with the sizing of any refrigeration that may be needed.

Many Vermont growers are probably familiar with the green book from 1986.  But did you know that a newer version is available online?  I was surprised to see how much the online version had that the printed version did not and (believe it or not) some recommendations have changed.  As you are putting things in storage for winter markets and other outlets, consider reviewing the revised Handbook 66 online. You may be surprised by what you find.


Food Storage Survey

I’m collecting information on Vermont’s commercial food storage practices.  This is most commonly a walk-in cooler or freezer on the farm or at a food hub, but there is room in the survey to tell me all about the other ways you store food.  The purpose of the survey is to provide a baseline against which to assess future growth and improvement, but also to determine where the need for more work and research is.

Please take 5 minutes to offer your perspectives by Wednesday, November 7, and spread the word.

Survey Link: http://survey.constantcontact.com/survey/a07e6ljmhoah94m2gdr/start

Food System Energy Use

Thanks to Eric Garza (UVM RSENR) for putting me onto this dense and fascinating report that summarizes the energy use in our food system. I was surprised to learn the per capita energy use in our food system increased significantly from 1997 to 2002.

From the report;

“Energy is an important input in growing, processing, packaging, distributing, storing, preparing, serving, and disposing of food. Analysis using the two most recent U.S. benchmark input-output accounts and a national energy data system shows that in the United States, use of energy along the food chain for food purchases by or for U.S. households increased between 1997 and 2002 at more than six times the rate of increase in total domestic energy use.

The use of more energy-intensive technologies throughout the U.S. food system accounted for half of this increase, with the remainder attributed to population growth and higher real (inflation-adjusted) per capita food expenditures.”

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.

Skip to toolbar