Pathogen transfer rates between postharvest surfaces and broccoli

Compared with other types of fresh produce, broccoli has not often been the focus of food safety-related research, despite the fact that it is commonly served raw in salads, salad mixes, and crudités platters. So, when Cornell M. Eng. student Yuezhi Wu consulted with Produce Safety Alliance Director Betsy Bihn about possible food science-related topics for his Masters in Engineering thesis, Bihn (who had recently signed on as a collaborator with the Eastern Broccoli Project) naturally thought of broccoli. The resulting study is the first to examine transfer rates of E. coli between broccoli and two surfaces commonly encountered in small packing operations. Though preliminary, the results will inform future risk assessments of the broccoli postharvest environment and help identify measures to prevent contamination events.

Wu’s co-authors on the study are his advisor, Cornell Biological and Environmental Engineering Professor Ashim Datta; Bihn; and Extension Specialist Lindsay Springer, a recent Food Science PhD who at the time was working with Bihn. After considering the postharvest surfaces that broccoli typically encounters in a small farm operation, the authors decided that gloved hands and conveyor belts pose the most risk. In a series of experiments with a nonpathogenic strain of E. coli, the team then measured bacterial transfer rates from contaminated broccoli to previously clean glove and conveyor belt material, and from contaminated conveyor belts and gloves to broccoli crowns and stems. To mimic contact between gloved hands and broccoli, small disks cut from nitrile gloves were pressed against broccoli stems or crowns for 5 seconds; to mimic contact with the conveyor belt, broccoli was dropped onto squares of belt material and kept there for 20 seconds.

The researchers found that the transfer rate from contaminated conveyor belt material to broccoli was much higher than the rate of transfer from contaminated broccoli to the conveyor belt. Contaminated glove disks transferred more bacteria to broccoli crowns and stems than contaminated crowns and stems transferred to glove material. Broccoli crowns in particular picked up more bacteria from contaminated gloves than did broccoli stems, which was attributed to the more porous structure of the crown. The authors noted that these results are consistent with studies using other fresh produce, which have found that transfer rates from non-organic surface (like the gloves and conveyor belt) to organic surfaces (broccoli and other vegetables) is typically higher than the reverse. The results emphasize the importance of cleaning and sterilizing conveyors and of sterilizing or replacing gloves frequently. Ultimately, this type of data can be used to construct models that will help growers understand contamination risks and determine the ideal cleaning schedule for their operation.

Reference

Wu, Y., L. Springer, E. Bihn, and A. Datta.  Quantifying Escherichia coli Cross-Contamination Rates among Broccoli, Conveyer Belt and Glove. https://hdl.handle.net/1813/57072

A new resource for plant research

The plant research community has a valuable and practical new resource available: a rapid-cycling Brassica oleracea population that can be used to map the genetics of many traits simply by phenotyping. The population and related resources are described in a recent publication led by Zach Stansell in Thomas Björkman’s lab at Cornell University.

  • The map and reference genome are complete
  • Bioinformatic-analysis pipeline is available
  • Seed is available for free
  • Researchers only need to phenotype and analyze


The BolTBDH population is derived from a from a cross of rapid-cycling Chinese kale with broccoli. It is particularly valuable for studying reproductive development because progeny lines have inflorescences that range from non-heading to fully heading broccoli. Variation is documented for many other traits, such as architecture and glucosinolate content, and variation in many others remains to be explored and documented.

To1000 is a small plant with long inflorescences, Early Big is a normal broccoli
Parents of BolTBDH: the rapid-cycling Chinese kale, TO1000 and the broccoli ‘Early Big’.

Continue reading A new resource for plant research

Selecting subjective traits in multiple sites.

Zach Stansell has adapted his tool for breeders so that it is usable for any crop that has a highly subjective breeding goal.

Stansell with computer code
Zach Stansell has developed an R package that helps breeders assess their criteria for subjective traits like beauty in many locations.

We are sharing the information with various media outlets. The first pass is a publication in the Cornell Chronicle.

Many horticultural crops need to meet the quality criteria of a particular market or of the main breeder. They need to meet those criteria in many environments. How can you test for   quality  in many locations at the same time. This technique is good at predicting the reference person’s quality score by having trained raters make objective measurements.

The package is posted on GitHub so that anyone can use it for free. It is annotated and revised to work with just about any trait of interest or any crop. The revision was done with Deniz Akdemir, Cornell statistician. The development of the method is published in HortScience (Stansell, Zachary, Thomas Björkman, Sandra Branham, David Couillard, and Mark W. Farnham. 2017. Use of a Quality Trait Index to Increase the Reliability of Phenotypic Evaluations in Broccoli HortScience 32:1490-1495. doi: 10.21273/HORTSCI12202-17 )

 

New Eastern Broccoli Buyer Listing

Small to mid-size growers in the eastern US have trouble finding reliable buyers for their broccoli, even as distributors, wholesalers, restaurants, and others say they cannot source enough regional broccoli to meet demand.  While matching specific buyers with specific sellers is beyond the scope of the Eastern Broccoli Project, we recently added a buyer listing webpage that may help the two groups connect. Growers can use the information to discover and introduce themselves to buyers with a declared interest in sourcing eastern-grown broccoli.  Buyers who agree to be listed have the opportunity to engage with local and regional suppliers of this popular produce item.

The Eastern Broccoli Project has developed numerous resources to help growers produce high quality broccoli and understand the expectations and challenges of the eastern broccoli supply chain (click on the ‘Resources’ tab of the menu to see some). However, it is up to growers and buyers to forge the good relationships that are critical to sustaining the eastern broccoli industry.  The buyer list is intended to help that process by fostering contacts and discussions between entities with complementary interests. Growers are generally advised to secure a buyer early, preferably before they have a crop in the ground.  Many buyers (not just the ones on our list) have specific expectations with respect to certifications, seasonal availability, minimum load size, and delivery.

All of the listings have been approved by their respective buyers. Each includes a brief description of the enterprise and the region they serve, along with a contact email address and logo with website link.  We expect the list to expand as more companies and food hubs find out about this opportunity to connect with eastern broccoli growers.

Hygienic Design for Post-harvest Facilities and Equipment

Preventing post-harvest contamination of broccoli and other fresh produce is easier when equipment and packing sheds are built with food safety in mind. A new resource developed with support from the Eastern Broccoli project brings the principles of hygienic design to the post-harvest environment to show how incorporating the right features and materials can simplify cleaning and eliminate common hiding spots for pathogens.

Hygienic design is the norm for food processing environments, but surprisingly little attention has been given to applying the principles to post-harvest equipment and facilities that handle raw agricultural commodities. That omission caught the attention of Produce Safety Alliance Director and Eastern Broccoli collaborator Betsy Bihn, who engaged University of Vermont Agricultural Engineer Chris Callahan to develop guidelines that would make it easier for cooling and packing environments to be in compliance with food safety standards. The result is Hygienic Design for Produce Farms, which is available for download from Callahan’s blog and via a link on the Eastern Broccoli Production resource page.

The publication explains the five key principles of hygienic design (visible and reachable surfaces; smooth and cleanable surfaces; no collection points; compatible materials; and preventing contamination) and discusses some of the tools and materials that can be used  to implement them in post-harvest operations.  The main goals are to eliminate “harborage points” (places where contaminants and pathogens can settle) and to ensure that all surfaces are accessible and suited to regular cleaning and sanitizing.  An “On-Farm Hygienic Design Checklist” is included in the publication and is also available in downloadable, stand-alone pdf and Excel formats.

The publication is intended for growers who are constructing or renovating their washing and packing operation. Agricultural equipment manufacturers will also find the publication useful, as it provides insights about the types of equipment improvements their customers need.

Managing nitrogen timing in summer-harvested broccoli

Picture of tight and loose heads, with cross-section of the heads
Late nitrogen application can cause early side-branch elongation, making the heads less desirable on the market. The top image shows a tight head with solid side branches. The lower image has a head that has begun to loosen at the sides. This effect can be reduced by having the last nitrogen application at least four weeks before harvest so that the growth rate is slowing down a bit just as harvest begins.

One of the challenges with raising broccoli in the East is getting heads to stay dense. In the warmth of summer, the outer branches of broccoli tend to start elongating a little before harvest maturity. They “blow up” in the words of many producers. The result is a head that doesn’t pack tightly in the box and has soft edges that are prone to damage in handling.

The solution is to let growth slow a little during the week before harvest. Growth is promoted by the combination of warmth, water, nitrogen, and sunlight. Warmth is a given for harvests in July and early August, sunlight we have no control over, and abundant water sometimes comes whether we want it or not. The main management tool is nitrogen.

Slowing growth by reducing nitrogen is a considerable challenge because abundant nitrogen is needed during the vegetative growth to get strong, healthy, fast-growing plants. The best approach is to supply nitrogen relatively early in the growing period, and not add nitrogen in the last four weeks.

Many popular broccoli varieties are harvested starting only eight weeks after transplanting. Therefore, the last nitrogen application should be only four weeks after transplanting. At that time, the foliage is near full cover, which a good time for a traditional side-dress application as well as cultivation to get escaped or newly germinated weeds. Fertigation through a trickle-irrigation system would be during the fourth week. At that time, the plants are large enough to take up the nitrogen but not so far along that excess growth at harvest will cause loose heads.

Applying all of the nitrogen before planting is a possibility. Ordinarily, applying 120 to 150 pounds per acre of nitrogen preplant is ill-advised because of the high likelihood of leaching before the crop takes it all up. However, because broccoli is only in the ground for about nine weeks through the end of harvest, and reaches its maximum uptake five weeks after transplanting, the risk of leaching loss is relatively low compared to the typical situation. Pre-plant application of the fertilizer opens up production options that don’t allow side-dressing or liquid fertilization.

This early-nitrogen approach is also helpful in reducing hollow stem. Hollow stem is likewise a symptom of excessive late vegetative growth. The main tool for managing hollow stem is adjusting the plant population. If hollow stem is a problem, it’s likely that both yield and quality will be improved by spacing the plants closer together. In New York we have found an in-row spacing of 8 inches to work quite well. But limiting late nitrogen also tempers the growth rate at the right time.

This article was published in VegEdge on June 5, 2019. A publication of the CCE Cornell Vegetable Program.

Fresh broccoli from Mexico now plays an important role

The Eastern Broccoli Project is intended to supply some of the growth in broccoli consumption in the East. The bulk of supply comes from coastal California in the summer and the desert southwest in the winter. But now, imports from Mexico are playing a greater role.

When the project started in 2009, Mexico was not a significant supplier of fresh broccoli to the East. That has changed. The volume from Mexico to the US is over $200 million per year. The frozen market is almost entirely from Mexico and Central America.

Fresh wholesale value is up from $60 to 250 million. Frozen has risen from $250 to $350 million.
The total value of imported fresh broccoli has quadrupled over the past ten years. Current imports represents about one fourth of the total wholesale volume. That amount can put pressure on prices. Frozen has risen modestly.
The wholesale price has risen from $0.30 to $0.50 since 2008
The wholesale price of imported broccoli has been rising steadily.

Mexican imports primarily compete with winter production in Florida and Georgia. The volume in the winter months has been rising over the last five winters, more than the summer imports. Growers in those areas are also expressing concern about the effect of the USMCA trade deal, fearing that it would allow dumping in their market.

Eastern production is closer to the Northeast market than either Mexico or the desert, but it is significant. The distance to the terminal market in Bronx NY from Hastings, Florida is 1000 miles in 15h of driving.  From San Luis Potosi, Mexico is 2400 miles in 36 hours, and from Yuma, Arizona is 2600 miles in 39 h.

Demand peaks at 60 million pound in January and bottoms in July at 20 million pounds. is fairl
Winter is the peak of fresh broccoli imports, but there is significant volume all year. The quantity shipped in January and February has been increasing most.

 

Volume varies modestly between 40 and 60 million pounds with peaks in March and October
Frozen broccoli imports are fairly stable throughout the year, reflecting a continuous consumer demand.

There are some facilities to freeze broccoli in New York. Developing a frozen deal for New York growers would be needed for a customer like a school system that specified New York broccoli under the farm-to-school program, but needed ready-to use product in their kitchens during the school year. The frozen-food giant Bonduelle raises and freezes broccoli in Québec, so the economics can be made to work nearby.

Thanks to USDA-ERS economists Kamron Daugherty and Broderick Parr for compiling this important information.

More Eastern farms are raising broccoli according to 2017 Census of Agriculture

We have eagerly awaited the 2017 Census of Agriculture to see whether the Eastern Broccoli Project is having an effect. Today, the results were released, allowing us to compare our early effect (2017) with the pre-project baseline. We are happy to see so many more Eastern farms finding a place for broccoli in their crop mix.

State
2012
2017
Gain
Maine 145 273 88%
Vermont 87 111 28%
New Hampshire 61 116 90%
Massachusetts 135 243 80%
Rhode Island 25 27 8%
Connecticut 51 132 159%
New York 290 535 84%
Michigan 158 443 180%
Pennsylvania 245 522 113%
New Jersey 64 136 113%
Delaware 5 19 280%
West Virginia 23 95 313%
Maryland 44 76 73%
Virginia 105 221 110%
North Carolina 140 317 126%
Tennessee 28 142 407%
South Carolina 34 100 194%
Georgia 44 138 214%
Florida 76 168 121%

Fertilizing the broccoli orchard

We have good fertility recommendations for various areas in the East on the resources tab.

A recent Bizarro comic has a great reference to broccoli’s ability to use fertilizer.

Fertilizer makes broccoli grow big
(c) Dan Piraro Used by permission.

We are not in cahoots with the “National Board of Broccoli Producers,” so broccolini is a fair stand-in at the Eastern Broccoli Project.

Waist high broccoli in a field with black soil.
Broccoli on muck soil gets a lot of nitrogen and water, and can grow very tall. Retired Cornell broccoli researcher Joe Shail provides the scale.

One consideration is that broccoli can get too big, and get hollow stem. Growers harvesting in the heat of summer find that making the last nitrogen fertilization four weeks before harvest helps avoid the excessive burst.

Some early varieties are maturing in 50 days in the summer. If you do the math, that means the last nitrogen side dress or fertigation is just three weeks after transplanting. Putting on ~150 lb/ac of nitrogen without burning the plants takes some planning.

Food Safety Workshop on Packing House Practices and Design

As part of their collaboration with the Eastern Broccoli Project, Produce Safety Alliance Director Betsy Bihn and University of Vermont Agricultural Engineer Chris Callahan have developed guidelines for the hygienic design of post-harvest equipment and surfaces in fresh vegetable packing operations. Prior to their efforts, this information was not readily available to growers and packers of fresh produce.

Now Bihn and Callahan are teaming up with Cornell Cooperative Extension Specialist Robert Hadad to host a workshop on Farm Food Safety – Sanitary Design and Practice Considerations. The event will take place on March 27 from 9 am to 4:30 pm in Jordan Hall at Cornell AgriTech, 630 W North St., Geneva, NY 14456.

Topics to be covered include:

  • Introduction to Produce Safety for the wash/pack facility
  • Cleaning – the “how’s and why’s”
  • Sanitizing – “how’s and why’s”
  • Drying – “how’s and why’s”
  • Hygienic Design and Practice Considerations
    • Visible and Reachable Surfaces
    • Smooth and Cleanable Surfaces
    • No Collection Points
    • Compatible Materials
    • Preventing Contamination
    • Equipment
    • Buildings
    • Tools and Practices
  • Applications
    • Greens Spinners – Comparison using evaluation checklist
    • Using SOP’s for hard to clean equipment
    • Barrel Washer
    • Brush Washer
  • And much more!

The cost, including lunch, is $20 for Cornell Vegetable Program enrollees and $30 for non-enrollees. An online pre-registration form can be found at: https://cvp.cce.cornell.edu/event_preregistration.php?event=1084.

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