Food Storage Curriculum for Farmers and Processors

The project was planned with the following methods;

• Assessment,
• Benchmarking,
• Gap identification,
• Research,
• Education, and
• Impact evaluation.

A summary of work relative to each component is provided below.

Assessment. A survey preceding this project proposal in 2012 identified the need for and interest in educational programming on the topic. The work of the project was to develop a relevant and effective approach to improving the knowledge of participants in the topic area. Additional field-work by the project team ahead of and early in this project period had helped to “paint the picture” of storage systems and practice in the region. In short it is highly varied, small-scale, generally using single temperature zones, and not monitored or controlled very well.

The first year of the project allowed for initial curriculum and resource development based on assessment of available resources and needs among the community. This initial needs assessment and associated collection of existing information and resources was critical to avoid duplication of effort and redundant or conflicting information. The delivery of the first year of workshops resulted in a great deal of feedback that was taken into account in refining and revising the second year’s workshop delivery. The basic structure of the course remained the same: the growing importance of long-term crop storage, principles of energy and heat transfer, basic heating and refrigeration, construction for utility and efficiency, maintaining temperature, airflow and humidity, biological processes of crops in storage, storage characteristics of various crops, and sizing and design of storage systems. However, the duration of the course and the level of detail were both reduced based on feedback of the participants. Most participants encouraged a 3-4 hour workshop instead of a 6.5 hour workshop and some suggested several focused, shorter (30 minute) classes.

Benchmarking/Gap Identification. The benchmarking proposed in this project proved to be a slightly ahead of its time. The state of storage systems in the region prevented clear characterization in this manner. For example, often insulation values were difficult to capture clearly as the systems were self-built with varied wall construction and insulation materials which leads to a complex description. What was very clear was that many farms knew they needed more storage space and wanted to do it better (cleaner, higher insulation, better control.) The needs expressed during field visits, emails, and phone calls were more meaningful in helping to develop the course outline than a detailed benchmarking study would likely have been.

Site visits have been a critical part of this project as that provides for very intimate exchange of storage information such as practices, infrastructure, challenges and achievements. “Knowledge” gaps among producers were most often associated with crop handling, curing, precooling and storage conditions, equipment selection and use, building layout and design and storage sizing estimation. Several key “practice” challenges have been noted; best practices for handling between harvest and storage, container selection and availability, finding and using smooth cleanable finish surfaces in storage (and other postharvest areas), accurate measurement and control of both temperature and humidity and achieving multiple sets of storage conditions within a single space.

Research. Research related to this project included collection and review of existing resources and publications for others to use. A primary reference material is USDA Handbook 66: The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Stocks. This reference is freely available, now only as an online format. It is a crop-specific guide to postharvest handling and storage of most crops grown and consumed in the United States. Other references included guides to insulation, cooler construction, building plans, refrigeration manuals and general science and engineering texts. The PI attended two courses with other funding that complemented this project; (1) The Pennsylvania State University’s Food Science Short Course and (2) The University of California at Davis Postharvest Technology Short Course. Both of these activities resulted in increased knowledge in the areas of food science, food safety and postharvest technology. This is a case of combining the results of differently funded projects for increased impact. The activities of this project have benefited from the inclusion of learning at these two other courses and the activities of the SARE project helped to identify the other courses as being important for regional progress in the postharvest realm. This project has also helped to confirm the interest in postharvest practices among regional producers first identified in the 2012 survey. This interest remains strong, but also includes topics beyond storage (e.g. breeding for postharvest, variety trials, precooling, curing, food safety, quality, value addition, etc.) This has led to the formation of a regional group focused on postharvest research and education which aims to leverage multi-state effort in a coordinated way to deliver improved knowledge to the region’s producers.

Education. Educational activity included workshops, meeting/conference presentations, webinars, website resources, and individual consultations. Specific results and outcomes from this component of the project are noted in the Results section. In this section we will outline the educational content developed and delivered.

Based on the preceding project components, the following educational outline and approach was developed.

Educational Topics:

• Importance of Food Storage – Why is food storage important to the region and specific farms and businesses? What competitive advantage can be achieved through improved storage practice?
• Crop Characteristics – How does crop physiology impact how we maintain storage conditions? Why and how do different crops differ in their optimal storage conditions? What production, harvest and postharvest conditions impact storage life and quality? What crops can be stored together and which ones need to be separate? Why do my carrots become bitter and my cabbage become black?
• Energy, Heat and Moisture – How do basic scientific principles factor into storage practices? What is relative humidity and how to we measure and control it? How does a refrigeration system work (and not work?) What are effective means for precooling different crops prior to storage?
• Structures and Materials – How big does my storage space need to be to store a certain amount of each crop? Should I build or buy a cooler? What sort of finish surfaces should I include to make sure my cold room is clean and safe?
• Equipment – What are my options for refrigeration equipment and how do they compare in terms of cost? What are the basic annual maintenance items I should look out for?
• Controls and Monitoring – What are the best thermostats I should consider to ensure precise and accurate temperature control? What are my options for measuring and controlling relative humidity? What are my options for being able to monitor my coolers when I am not physically there?

Key Learning Principles:

1. Know your target conditions. Be informed about what storage conditions are ideal for each of your crops.
2. Provide multiple zones. May not be multiple rooms. It is likely that if you are growing a diverse set of crops, you will want multiple zones for storage.       This may not mean needing separate rooms as we have found even small rooms can have drastically different temperature and humidity conditions depending on the location of the cooling equipment relative to the location.
3. Informed design, construction and purchase of equipment. It is helpful to know ahead of time how much space you will need by estimating the required, zoned volume from bulk densities and groupings of crops by ideal storage conditions. Smooth cleanable finish surfaces should be planned and budgeted for to provide for longevity and sanitary conditions. There are clear trade-offs between conventional refrigeration systems and lower-cost CoolBot™ systems which should be understood before making a purchase decision.
4. Measure your actual conditions. It is often misleading to depend on the thermostat installed with your refrigeration equipment. It may not be accurate and it may not be measuring the actual location that matters. Investing in one or more digital, calibrated thermometers will enable you to know with certainty the air and pulp temperature anywhere in your system and to make adjustments as needed. Additionally, often a retrofit of a good digital thermostat will improve performance of the refrigeration system in place.
5. Improve crop selection on the way in. Storage is a hotel, not a hospital. Damaged or diseased crops going into storage are not going to improve and they are likely to degrade themselves and neighbors. Rigorous culling and sorting prior to storage and attention to detail during any precooling and curing steps will help to ensure a higher overall quality of stored product.

Learning Objectives:

• The student will know and appreciate that fresh produce is still alive and respiring.
  • Generating heat, water vapor and carbon dioxide.
  • Generating the ripening hormone ethylene.
  • Respiration is temperature dependent and crop specific.
  • Storage is a hotel not a hospital.
• The student will learn about the critical need for establishing and maintaining the “cold chain.”
• The student will learn about crop-specific temperature conditions
  • Precooling requirements
  • Chilling and freezing injury potential and limits.
  • Optimal storage temperature
• The student will learn about crop-specific humidity conditions.
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  • What humidity is.
  • Importance of high humidity to prevent desiccation
  • Importance of low humidity to prevent plant pathogen development (e.g. molds).
  • How humidity is different from liquid water
• The student will learn about basic storage room construction
  • Materials and practices that can and should be used (structure, insulation, finish).
  • Materials and practices to avoid.
  • Pre-fabricated options.
• The student will learn about basic refrigeration systems
  • How a refrigeration heat pump works.
  • How a common split refrigeration system functions (compressor/condenser, expander/evaporator).
  • How alternative systems work (e.g. CoolBot™, root cellars, outside air exchange).
  • General pro’s and con’s of different approaches.
  • The impact of refrigeration systems on “micro-climates” in the storage space.
• The student will learn about basic controls and monitoring.
  • Basic information about thermostats, stressing the need for precision and accuracy.
  • Basic information about humidistats, hygrometers and psychrometers, stressing the general lack of reliability in existing items on the market.

It is important to note that this project benefited from the work of other SARE funded projects. Specifically, the work done by SARE NH State Coordinator Seth Wilner in the area of adult education theory was particularly helpful. Below are some examples of activities that were integrated into the workshop series to facilitate improved adult learner experience.

Activities (Incorporating Adult Learning Theory)

• Reflection on Motivations - During introductions – Have participants describe their farm, business and organization and reflect on why they are present and what they hope to gain.
• Crop Characteristics – Summary Slide – Simply ask what is common and what is different about common storage crops.
• Crop Characteristics – USDA Handbook 66 – Have students pick a crop, look it up in USDA Handbook 66, read about its optimal handling and storage and summarize back to the group including any unexpected findings.
• Energy, Heat and Moisture – A Cold Glass of Water – Present a picture of a glass of ice water on a hot, humid day. Ask the class to reflect on what is happening the picture.
• Energy, Heat and Moisture – Measuring RH with a Sling Psychrometer – Allow students to use a sling psychrometer to measure the RH of the classroom air. Then send them outside to do it (preferably on a cold, dry day.)
• Structures and Materials – Insulation and Finish Surfaces – Pass around samples of insulation and finish materials for the students to touch and feel. These can also be placed on the desks and tables ahead of class as a tactile opportunity for those who benefit from that.
• Equipment – CoolBot™ Demonstration – A small CoolBot™ cooling system can be constructed and put on rollers. This can be used to demonstrate the basics of refrigeration while also demonstrating this novel approach to using a window air conditioner to provide cooling for small cold rooms.
• Equipment – Outside Air Exchange – A small demonstration panel can be made to show how two thermostats and a fan can be used to provide cooling using outside air on cold winter days.
• Controls and Monitoring – Thermostats – Pass around several examples of thermostats with different features and point out the differences. The outside air exchange panel noted above is also a good way to demonstrate a good thermostat and how they work. Other portable measurement devices can also be demonstrated (e.g. infrared, calibrated insertion thermometers).
• General Experiential Learning – Invite participants to bring pictures and short slide shows of their own storage spaces and projects, even planned projects. Provide time during breaks or at the end of class to allow participants to share what they have done at their own farms or are planning to do. Facilitate group discussion and encourage questions, tying discussion back into course content to reinforce learning.

This workshop is more than a review of example coolers. The content includes relevant science and engineering fundamentals. One student observed, “Your master plan worked. You snuck that math in and I didn’t even realize I was doing it.” We found that participants enjoyed the fundamental science involved in this topic when delivered in measured doses. The classes have been largely farmers and when the relevance of the math and science are made clear, there is strong uptake. We receive follow-up emails from students who have done calculations and are looking for review of the work. A significant part of this workshop series’ improvement has been integration of adult learner theory. The PI became aware of resources available in this area at a UVM Extension programming meeting were Mr. Wilner presented on adult education principles. We incorporated practices such as frequent breaks, hands-on exercise, student reflection, and open-ended questioning with plenty of time for response into the course outline. Students have responded positively to these changes, and I feel (based on evaluations), they leave the course excited about their learning and what they can do with it. One student at the Shelburne workshop noted, “I thought the practice exercises in small groups was a huge practical piece of the program. It allowed us to understand how to use the tools you gave us. This was one of the best workshops I have been to and found the material to be current and applicable. I liked how you switched commentators to keep it from getting boring with just one person always talking.”

Impact Evaluation. This project has engaged over 20,000 participants using a range of methods and varying degrees of formality. The impact of the work was most closely observed in direct consultations, followed by evaluation responses from workshops. This is covered more fully in the Impact of Results / Outcomes section.

• Theresa Snow (Salvation Farms, Morrisville, VT) gains hands on experience using a sling psychrometer to measure relative humidity of air and important factor in long-term storage of fruits and vegetables. October 2015.
• A table used to demonstrate how optimal storage conditions differ for 5 common storage crops. Note the differences in temperature, humidity, respiration (heat generation) rate, ethylene production and ethylene sensitivity.
• The 2014 workshop held at Shelburne Farms Coach Barn in Shelburne, VT.