The “In-Between”: Precooling and curing fruits and vegetables for improved quality and profit

Final report for LNE16-347

Project Type: Research and Education
Funds awarded in 2016: $129,514.00
Projected End Date: 10/31/2019
Grant Recipient: University of Vermont
Region: Northeast
State: Vermont
Project Leader:
Christopher Callahan
University of Vermont Extension
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Project Information

Performance Target:

100 farmers who gain knowledge and skills about curing and pre-cooling processes, systems and measurements will adopt improved curing and pre-cooling practices on their farms, resulting in a total revenue benefit of $800,000 due to reduced indirect costs of culled products.

Cooperators

Click linked name(s) to expand
  • Robert Hadad

Research

Hypothesis:

Demonstration of scale appropriate precooling and curing practices will enable increased adoption of improved practice resulting in higher produce quality lower postharvest waste.  The research component of this project is focused on developing improved understanding of precooling and curing processes as currently practiced in the region and in other areas to seek improvement via extension educational programming.  There is a strong foundational work in this areas as noted in the literature review; our task is to leverage that work and adjust it for regional relevance, scale appropriateness and cost efficacy.

Materials and methods:

The project team explored several farm-scale approaches to precooling including: CoolBot(TM) powered carton cooler, counter-top forced air cooler, and pallet forced air cooler. We had planned to also explore small scale hydrocooler demonstrations, but the grower interest in the forced air coolers was greater than hydrocooling due to the simplicity of the approach.  Although forced air cooling and hydrocooling are suited for different crops, we focused our attention on forced air cooling for the majority of this project.

Two forced air coolers were built and documented using a build guide and bill of materials for others to replicate the designs.

UVM-Ext-Forced-Air-Cooling-Fact-sheet-v1.0-2018-10-03-draft-1.2-AC-Edits

The rapid reduction of produce pulp and core temperature is important to maintaining postharvest product quality. Forced air cooling is one method that accomplishes this and it is practiced widely among larger scale producers and aggregators. This project was intended to demonstrate this practice and its potential benefit to small and medium scale growers.

We performed a series of precooling trials using small-scale forced air coolers to cool eggplant, watermelon, strawberries, blueberries, zucchini, and roasting peppers. The forced air cooling was done in parallel with standard room cooling and was shown to result in cooling rates ranging from 1.2 to 2.2 times faster than room cooling. This test demonstrated the feasibility and benefit of simple forced air cooling systems to smaller scale farms.

In each trial, two batches of the crop with roughly equivalent mass were harvested into standard cartons or bins based on the practice of the farm. One batch was cooled using room cooling—allowing the product to cool as it would when simply set in the walk-in cooler or CoolBot room. The other batch was cooled using a forced air cooling system built from one of the two plans referenced above. The batches were cooled in parallel with a target of reaching 7/8 of the optimal storage temperature for each crop (“7/8 temperature”).

Product temperature was monitored in each batch using an insertion probe thermocouple and a data acquisition system with a 3 second sampling period. These data were used to fit a cooling rate curve using an exponential decay model and minimizing the error between the model and the actual data. The cooling rate curves were used to estimate 7/8 cooling time for larger, more dense crops or those that did not reach 7/8 temperature during the time allowed for the test.

The details of these tests are documented in the fact sheets below.

Blueberries: Forced-Air-Cooling-Field-Trial-Results-Blueberries-v1.1

Eggplant: Forced-Air-Cooling-Field-Trial-Results-Eggplant-v1.1

Peppers: Forced-Air-Cooling-Field-Trial-Results-Peppers-v1.1

Strawberries: Forced-Air-Cooling-Field-Trial-Results-Strawberries-v1.1

Watermelon: Forced-Air-Cooling-Field-Trial-Results-Watermelon-v1.1

Zucchini: Forced-Air-Cooling-Field-Trial-Results-Zucchini-v1.1

Hydrocooling was explored using engineering analysis and initial plans were developed for a low cost, farm-built hyrdocooler approach which we plan to demonstrate with partner farms in 2020.

Farmer interest in precooling was slow to develop in this project.  This impacted the team’s ability to achieve the level of on-farm implementation we had projected.  Despite the slow start, farmer interest has accelerated in 2019 and into 2020 with 20 farms expressing interest in the educational materials and indicating an intent to adopt the practice of forced air cooling.  Others are also expressing interest in hydrocooling for greens and we intend to continue the educational and technical assistance needed to help these farms with implementation of the practice.

Research results and discussion:

Four farms partnered in demonstrating a prototype forced air cooler used on 9 different crops.  As noted above, we performed a series of precooling trials using small-scale forced air coolers to cool eggplant, watermelon, strawberries, blueberries, zucchini, and roasting peppers. The forced air cooling was done in parallel with standard room cooling and was shown to result in cooling rates ranging from 1.2 to 2.2 times faster than room cooling. This test demonstrated the feasibility and benefit of simple forced air cooling systems to smaller scale farms. The details of these tests are documented in the fact sheets above and are summarized in the table below.

 

Research conclusions:

Two designs of forced air coolers were developed that utilize common farm materials and construction methods.  These designs were used in a series of precooling trials to cool eggplant, watermelon, strawberries, blueberries, zucchini, and roasting peppers. The forced air cooling was done in parallel with standard room cooling and was shown to result in cooling rates ranging from 1.2 to 2.2 times faster than room cooling. This test demonstrated the feasibility and benefit of simple forced air cooling systems to smaller scale farms.

Participation Summary
20 Farmers participating in research

Education

Educational approach:

RECRUITMENT – We were able to connect with ten (10) farms expressing interest in this topic.  The recruited farms were representative of the (a) scale, (b) crop and (c) market diversity of the region to ensure applicability of the work to others. The collaborative work .

DELIVERY METHODS – The educational programming followed three modes of delivery; (1) direct consultation and (2) workshops and (3) web-based document and video learning.

DIRECT CONSULTATIONS: We aimed to work directly with 10 farms actively pursuing precooling and curing improvements on their farm and were able to recruit this number. The ability to implement the practice on each farm was variable, but the effort was critical in collecting field test data as reported above.

WORKSHOPS: Current good practice at regional farms were documented through interview, photo, video and fact sheet development together with foundational material. Educational events were held at selected sites with relevant and significant pre-storage infrastructure to demonstrate both principles and practice using site infrastructure and demonstration systems built for the workshops.

WEB-BASED: Lasting outputs from this project include documentation of case studies of pre-cooling and curing infrastructure demonstrations, consolidated crop-specific guidance on precooling and curing conditions and processes, and plans for demonstration systems developed as a result of the project.  Materials have been captured and distributed via existing websites as noted in the outputs section.

CURRICULUM TOPICS – Workshop and conference topics included crop physiology (e.g. metabolic respiration), cold chain, basic heat transfer, post-harvest precooling systems and equipment, post-harvest curing systems and equipment, measures of quality, process control, monitoring and record keeping.

BENEFICIARY SUPPORT – As noted above, the educational delivery has been diverse and a key component of the project has been to establish on-line resources for reference by others seeking to make improvements in this area.  These have included fact sheets, videos and plans for systems.  However, as the team has experienced in prior projects, workshops and materials help to set a foundation of common knowledge from which direct, project specific collaboration can be built.  We have provided direct support of practitioners and remain an available resource in support of future adoption.

Milestones

Milestone #1 (click to expand/collapse)
What beneficiaries do and learn:

DIRECT CONSULTATION PARTNERS – 18 month engagement x 10 participants

We worked directly with 10 farms actively pursuing precooling and curing improvements on their farm. This work enableed pragmatic and focused research by the project team while also supporting immediate behavior change and infrastructure adoption among beneficiaries and allowed for documentation of case studies for use in workshops and educational materials.

Proposed number of farmer beneficiaries who will participate:
10
Proposed number of agriculture service provider beneficiaries who will participate:
3
Actual number of farmer beneficiaries who participated:
11
Actual number of agriculture service provider beneficiaries who participated:
5
Proposed Completion Date:
December 31, 2019
Status:
Completed
Date Completed:
December 31, 2019
Accomplishments:

The project team conducted recruitment outreach and worked with 11 farm partners / beneficiaries. Eight of these farmers have provided direct feedback on their intended use and design detail. The team has also developed two forced air precoolers of two different scales.  This work was presented at the NEVFC (2017 & 2019) and generated increased interest in the project among potential partners. Fact sheets have been developed documenting the forced air cooler construction (http://go.uvm.edu/forcedaircooling). Initial trials with the forced air coolers has led to the accumulation of performance data which was published as an additional fact sheet.

Milestone #2 (click to expand/collapse)
What beneficiaries do and learn:

WORKSHOP PARTICIPANTS – 9 month overlapping engagements (~12 months) x 4 workshops x 50 participants per workshop

Current good practice at regional farms will be documented through interview, photo, video and fact sheet development together with foundational material. Hands-on, on-farm workshops will be held at selected sites with relevant and significant pre-storage infrastructure to demonstrate both principles and practice using site infrastructure and demonstration systems built for the workshops.

Proposed number of farmer beneficiaries who will participate:
200
Proposed number of agriculture service provider beneficiaries who will participate:
4
Actual number of farmer beneficiaries who participated:
860
Actual number of agriculture service provider beneficiaries who participated:
30
Proposed Completion Date:
December 31, 2019
Status:
Completed
Date Completed:
December 31, 2019
Accomplishments:

A combination of twilights sessions, farm meeting presentations, and conference presentations were provided for 890 attendees over 829 contact hours.

2017      Postharvest Handling Can Improve Fresh Market Success. C. Callahan. New England Vegetable and Fruit Conference. Manchester, NH. December 14. 2017. [70 attendees, 45 minutes, 53 contact hours]

2017      Postharvest Cooling and Curing. C. Callahan. New England Vegetable and Fruit Conference. Manchester, NH. December 13. 2017. [320 attendees, 45 minutes, 240 contact hours]

2017      Postharvest Handling and Storage for Small Farms. C. Callahan. Great Lakes Expo. Grand Rapids, MI. December 7, 2017. [30 attendees, 45 minutes, 23 contact hours]

2018      Allium Twilight. C. Callahan, C. Stewart, H. Prussack. High Meadows Farm. July 12, 2018. [25 attendees, 3 hours, 75 contact hours]

2018      Postharvest Practices in Berries. C. Callahan. Northeast Berry Call. June 12, 2018. Webinar.

2018      Produce Safety in Broccoli. C. Callahan and E. Bihn. May 14, 2018. Webinar. [36 attendees, 1 hour, 36 contact hours]

2019      Pre-Cooling and Curing Crops. New England Fruit and Vegetable Conference. C. Callahan and A. Chamberlin. Manchester, NH. December 12, 2019. [230 attendees, 30 minutes, 115 contact hours]

2019      Post-Harvest Handling of Onions & Garlic. New England Fruit and Vegetable Conference. C. Callahan. Manchester, NH. December 11, 2019. [100 attendees, 30 minutes, 50 contact hours]

2019      Techniques & Set-Ups for Washing and Postharvest Handling. A. Chamberlin and C. Callahan. Maine Organic Farmers and Gardeners Association (MOFGA) – Farmer to Farmer Conference. Northport, ME. November 3, 2019. [15 attendees, 3 hours, 45 contact hours]

2019      Winter Crops: Handling, Washing, and Storage. C. Callahan and A. Chamberlin. Maine Organic Farmers and Gardeners Association (MOFGA) – Farmer to Farmer Conference. Northport, ME. November 3, 2019. [15 attendees, 3 hours, 45 contact hours]

2019      The New Frontiers in Garlic Production. Half-Day Intensive. C. Stewart, E. Fraser, B. Fox, & C. Callahan (Postharvest handling.) NOFA-NY Winter Conference. Saratoga Springs, NY. January 19, 2019. [49 attendees, 3 hours, 147 contact hours]

Milestone #3 (click to expand/collapse)
What beneficiaries do and learn:

WEB-BASED: Lasting outputs from this project will include documentation of workshops and case studies of pre-cooling and curing infrastructure demonstrations, consolidated crop-specific guidance on precooling and curing conditions and processes, and plans for demonstration systems developed as a result of the project. Materials will be captured and distributed via existing websites. Beneficiaries will be able to access project outputs and guidance at their convenience for self-paced, and self-directed learning and adoption of practice.

Proposed number of farmer beneficiaries who will participate:
800
Proposed number of agriculture service provider beneficiaries who will participate:
2
Actual number of farmer beneficiaries who participated:
2961
Proposed Completion Date:
December 31, 2019
Status:
Completed
Date Completed:
December 31, 2019
Accomplishments:

Project outputs were posted on the UVM Extension Ag Engineering blog and shared via social media. The seven (7) individual resources (noted below with views) have been viewed and/or downloaded a total of 2,364 times with a total online engagement time of 1,545 minutes (26 hours).

http://blog.uvm.edu/cwcallah/2018/10/09/forced-air-cooling-on-the-farm/ (891)

http://blog.uvm.edu/cwcallah/2018/10/09/construction-details-for-a-pallet-forced-air-cooler/ (419)

http://blog.uvm.edu/cwcallah/the-in-between-precooling-and-curing-fruits-vegetables-for-improved-quality-and-profit/ (408)

http://blog.uvm.edu/cwcallah/2019/06/17/forced-air-cooling-field-trial-results/ (302)

http://blog.uvm.edu/cwcallah/2018/10/09/construction-details-for-a-counter-top-forced-air-cooler/ (185)

http://blog.uvm.edu/cwcallah/2018/07/04/all-about-alliums-twilight-meeting/ (81)

http://blog.uvm.edu/downloads/cwcallah/files/2018/10/UVM-Ext-Forced-Air-Cooling-Fact-sheet-v1.0-2018-10-03-draft-1.2-AC-Edits.pdf

Videos of project outreach and educational events were compiled and published on the UVM Extension Ag Engineering YouTube channel (https://www.youtube.com/channel/UCwLVR4LaVPtvm4m3XW5Kv9w). These videos have had a total of 1416 views.

Forced Air Cooler Prototype Walk Around: https://www.youtube.com/watch?v=wwgb9CsJsyc 0:37 (240)

Small-scale Forced Air Cooling demo:https://www.youtube.com/watch?v=Ccy5KxrVhPk 1:30 (971)

Allium Twilight Playlist: https://www.youtube.com/playlist?list=PLRhtZw1o6RdF2ntRjuFnts2Gu1zwz6Vot 5 videos, (205)

Milestone Activities and Participation Summary

40 Consultations
9 Curricula, factsheets or educational tools
5 On-farm demonstrations
1 Tours
10 Webinars / talks / presentations
1 Workshop field days

Participation Summary

3800 Farmers
70 Number of agricultural educator or service providers reached through education and outreach activities

Learning Outcomes

40 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
10 Service providers reported changes in knowledge, attitudes, skills and/or awareness as a result of project outreach
10 Agricultural service providers reported changes in knowledge, skills, and/or attitudes as a result of their participation
Key areas in which farmers reported changes in knowledge, attitude, skills and/or awareness:

Importance of precooling for product quality

Practices and approaches for effect precooling

Appropriate approaches for precooling according to crop

Easy, low cost ways to adopt precooling on the farm

Performance Target Outcomes

Target #1

Target: number of farmers:
40
Target: change/adoption:

Incorporation of precooling measures into postharvest practices.

Target: amount of production affected:

$320,000 sale value of produce

Target: quantified benefit(s):

$320,000 sale value of produce

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.