FAQ’s from Curriculum Trainings

I want to encourage agents to submit their questions to this blog for answers.  I will make every attempt to answer appropriately.


Q1. What’s considered an outbreak? (widespread/foodborne)

The confirmed presence of disease or infection of one or more cases in a defined epidemiological unit (eg flock, herd, farm or village) and during a specified period of time. (Source www.fao.org/avianflu/en/glossary.html)

A sudden increase in the number of individuals who contract a specific infectious disease in a population, putting others at risk. (Source: www.sdnhm.org/exhibits/epidemic/teachers/glossary.html)

Q2. What are the current food safety laws?

Laws governing fresh produce are currently being developed.  As of right now, the fresh produce industry is governed by FDA with guidance documents.  Specifically,The Guide to Minimize Microbial Food Safety Hazards of Fresh-cut Fruits and Vegetables, issued in 1998 by FDA, and subsequent commodity-specific guidance documents for the Leafy Greens, Tomato, and Melon industries. More information on all these is included on the FDA Produce Safety: Guidance, Compliance & Regulatory Information website.

Q3. Are there any specific standards for Rainwater harvesting quality?

Harvested rainwater is considered like an open water source.  There is potential for contamination, especially from bird or small animal feces.  This water will need to be tested like any other open water source.

Q4. Is there a timeline for when you can use water for irrigation from sources like streams/ponds if it has been determined it was contaminated?

There are current guidelines included in the Leafy Green Marketing Agreement on remediation efforts should you receive an unacceptable quantified level on generic E. coli tests on irrigation water tests.  Specific information is detailed in Module 6 under Remedial Actions.

Q5.How much distance is required between animals and fields (especially on hills?)

There are some guidelines on buffer zones, but no regulations that I am aware of currently.   Specific guidance on buffers are included in the Leafy Green Marketing Agreement.  Additionally, I am aware to some current guidance/permits that might be required by NC Dept. of Environmental Health and Natural Resources that might impose some buffers should the growers be governed by the permitting.  Please see the Leafy Greens Marketing Agreement, pages 47 & 48 for further specific guidance.  Remember, the goal is to reduce the risk of contamination.

Q6. Are there any specific testing standards for leaching?

I am getting better clarification on this question right now…..

Q7. Are there any consumer handling regulations?

No regulations.  FDA’s primary function is to protect consumers.  That said, FDA has developed quite alot of information on how consumers should handle produce.  Please see Consumers Food Safety & Nutrition Information and Campaigns

Q8. Are there any current enforcement measures being taken for pick-your own enterprises?

No, as stated above, no regulations and thus enforcement measures are currently enforce.

Q9. Is there any size consideration in GAPs certification?

A farm of any size can get GAPs certified as long as they follow the necessary process to do this including forming a Fresh Produce Safety Manual and undergoing a third-party audit.  Government regulation and legislation is undecided at this point, but it is hoped that legislature will take a scale-appropriate and educational approach.

Q10. What are the sanitation requirements for harvest bins?

Q11. Are there any good examples of proper hand washing equipment?

Specialists from NC State University in the horticulture and agricultural engineering departments are teaming up to construct blueprints for a low-cost, effective hand-washing station plans.  This will hopefully be available to growers soon.

Q12. Best management practices for minimizing contamination from culled produce in the packinghouse or harvest?

Culled produce can be a source of pathogen contamination in the packinghouse or in the field.  Produce that is damaged or beginning to rot is more susceptible to pathogen contamination than fresh and in-tact produce.  It is important to minimize the amount of culls in a production field.  Culled produce not only can be a source of contamination, but may also attract animals into a packinghouse or field.  Do your best to move culled produce away from production areas or packinghouses to avoid contamination.  Placing the culls into a compost pile or dumpster away from production areas is advised.

Q13. Are there Hydrocooling vs. dump tank water temperature  specifics that can be referenced?

Hydrocoolers (Adapted from Hydrocooling,  M. D. Boyette, E. A. Estes, A. R. Rubin.  NCSU BAE AG-414-4)

When warm produce is cooled directly by chilled water, the process is known as hydrocooling. Hydrocooling is an especially fast and effective way to cool produce. With modern technology, hydrocooling has now become a convenient and attractive method of postharvest cooling on a large scale.


  • Cools produce rapidly (about 15 times faster than air).
  • Allows for greater harvesting and marketing flexibility.
  • Easily handles large amounts of produce (although hydrocoolers can also be designed for smaller quantities of produce).

There are also some limitations to using hydrocoolers:

  • They can be used only for produce not sensitive to wetting. Many diseases are encouraged by wetting.
  • Some hydrocoolers are not as energy efficient as other methods and therefore may not be as cost effective in some situations.
  • There are some restrictions on the types of packaging and stacking arrangements used for produce that is to be hydrocooled.

Hydrocooling Methods

In most hydrocoolers, a pump moves chilled water into contact with warm produce. The warmed water is then recooled and recycled. For cooling the water, many hydrocoolers have a vapor-compression refrigeration system similar to an air conditioner or refrigerator. A refrigeration system can be thought of as a pump that moves heat. The capacity of a refrigeration system to move heat is measured in tons. One ton of refrigeration is equivalent to 12,000 Btu per hour.

Some hydrocoolers do not use a refrigeration system. Instead, crushed or chunk ice is used to cool the water. Typically, large blocks of ice weighing as much as 300 pounds are trucked from an ice plant, crushed, and added as needed to a water reservoir attached to the hydrocooler. The capital cost of a hydrocooler of this type is much less than one with an integral refrigeration system and may be preferred by growers with a limited amount of produce or a short cooling season. However, to make a valid economic comparison, the cost of the ice must be considered. For a hydrocooler of this type, a reliable source of ice must be available at a reasonable cost.

Dump Tanks (Adapted from Handling Florida Vegetables Series – Round and Roma Tomato Types, S. A. Sargent, J. K. Brecht and T. Olczyk.  UFL IFAS Publication #SS-VEC-928)

In a packinghouse vegetables and fruit are normally transferred into a water flume system (dump tank) for gentle transfer to the packing line. Produce handled in field bins are automatically dumped into the dump tank, while those in gondolas are flumed out using the dump tank water. Plant pathogens will accumulate in dump tank water since the water is recirculated throughout the packing day. Therefore, dump tank water must be constantly sanitized to minimize the possibility of cross-contamination via infiltration of water and pathogenic microorganisms through the stem scar, the blossom-end scar or through cuts and punctures. If the time in the dump tank water is less than 30 seconds, water may be left at ambient temperature, however, longer exposure times require heating the dump tank water to about 10oF above the incoming fruit pulp temperature in order to avoid infiltration of bacterial pathogens into the tomatoes. For more details concerning management of tomato dump tanks, see Ritenour et al. (2002) and Mahovic et al. (2004).

Q14. Specific cost for GAPs certification audits?

The cost for a third-party GAPs audit varies.  The first thing a grower should do when considering GAP certification is to find out which third-party auditor their specific buyer is requiring.  Then, the grower should contact that third-party auditing company directly.  Audit process may depend on size of operation and the distance travelled by the specific auditor.  You can find a list of third-party auditors on the NC MarketReady Fresh Produce Safety Field to Family website.  http://www.ncmarketready.org/ncfreshproducesafety/ Then click on ‘Audits’ and then scroll down to the list of ‘Third-Party Audits’.

Q15. Can you get GAPs certified if you field-pack?

A grower can get certified if they field pack.  The USDA Audit Checklist provides good guidance for growers who are getting ready for their GAP audit.  On this Audit Verification Checklist, you will see that there are different areas in which you can get audited.

Everyone gets audited on the General Questions.  This section deals with the preparing and following of a food safety program that incorporates GAPs, traceability and worker health and hygiene.

The other audits that a grower can obtain are 1.  Farm Review, 2. Field Harvesting and Field Packing Activities, 3.  House Packing Facility, 4.  Storage and Transportation, 5.  Wholesale Distribution Center/Terminal Warehouse and 6.  Preventative Food Defence Procedures.

To obtain a copy of the USDA audit, visit the NC MarketReady Fresh Produce Safety Field to Family website: http://www.ncmarketready.org/ncfreshproducesafety/ Then click on ‘Audits’ and then ‘USDA Audit Checklist’.

Q16. What do you do with your wash water?

The NC Department of the Environment and Natural Resources (NCDENR) considers this wash water to be “wastewater”.  Contact NCDENR to find out how to properly dispose of this water.

Q17. Why are Listeria, B. cereus, and Clostridium now a problem?

Q18. Will there be a range of bacteria count that will acceptable/unacceptable?  During a water test?

It is important to understand the types of tests available to obtain the bactieria counts first.  There are generally three different water tests are available at most labs:

  • Total coliform
  • Fecal coliform
  • The recommended generic E. coli test.*

*It is important to understand the difference and to request the generic E. coli test that is quantitative.
Total coliform bacteria are microbes found in the digestive systems of warmblooded animals, in soil, on plants and in surface water. Fecal coliform bacteria are a kind of total coliform. The feces (or stool) and digestive systems of humans and warm-blooded animals contain millions of fecal coliforms. E. coli is part of the fecal coliform group and may be tested for by itself, such as with the recommended generic E. coli test.

Tests can indicate either a minimal reading of presence and/or absence or can quantify the amount of the pathogen’s presence. These quantitative tests are what you should be looking for with results measured in MPN (most probable number) or CFU (colony forming units).

Standards for microbiological testing of IRRIGATION WATER for
generic /E. coli/ are as follows
( in accordance with the
Clean Water Act of 1972 /Bacterial Water Quality Standards for
Recreational Waters (Freshwater and Marine Waters/ and the
Leafy Greens Marketing Agreement Guidance):

1.  Where edible portions of the crop ARE NOT contacted by water

  • Acceptable Criteria: Single Sample: less than or equal to 576 MPN/100 per mL
  • Acceptable Criteria: Geometric mean of 5 samples: less than or equal to 126 MPN/100 mL

2.  Where edible portions of the crop ARE contacted by water

  • Acceptable Criteria: Single Sample: less than or equal to 235 MPN/100 mL
  • Acceptable Criteria: Geometric mean of 5 samples: less than or equal to 126 MPN/100 mL

Standards for microbiological testing of Postharvest/Processing Water are as follows:

  • Water in direct contact with produce should meet EPA  MCLG (maximum contaminant level goal) microbial drinking water quality standards.  Acceptable Criteria: Generic E. coli negative test or below detection limit and MCLG for total coliform in drinking water is zero

Additional information that might be helpful to know from the lab is: Water collection protocol, test results turnaround time and how test results are relayed to you.

Growers are encouraged to find local laboratories that can run the generic E. coli tests. Using the local phone book, look under “Water Testing.”

Q19. Is there a desired chlorine ppm growers should aim for?

  • Rule of thumb is generally a range of 100-150 PPM of free chlorine, but accepted chlorine ppm level for dump tanks can vary depending on produce.  Dr. Trevor Suslow has a nice paper on parameters associated with chlorine use in dump tanks at: http://anrcatalog.ucdavis.edu/pdf/8003.pdf
  • In this paper the parameters to measure include free chlorine (PPM), temperature (F/C),  pH, and contact time in the dump tank.  As far as what kind of chlorine test strips to use, the growers can get chlorine and pH strips at the local pool supply place ( as well as K-mart, Walmart, and Target).  Temperature can be taken with a regular thermometer and temperature should be appropriate for the particular commodity.  As I don’t know the commodity you are dealing with, I can only give you general postharvest handling parameters which can be found at :http://www.ncmarketready.org/ncfreshproducesafety/postharvest.html
  • As far as how to mix up your dump tank for the required ppm, it depends on the chlorine produce you use and the %Acitive ingredient.  Florida has a nice publication on how to do this with different products in 100 gal tanks.   http://edis.ifas.ufl.edu/ch160

Q20.  Do all workers have to be certified?

All workers handling food product should be trained.  GAPs certification typically will fall to the grower and/or packing houses.

Q21. What if you have a grower that has gone through the training but doesn’t want to be recognized on the database or obtain a certificate of attendance?

Please pass along number of people to Diane_Ducharme@ncsu.edu

Q22. How do you do a SOP (Standard Operating Procedure)? Do you have any blank forms he could look at? Any directions on what needs to go in the thing? Something?

A22. Here are some good websites to understand better understand what an SOP is and how to write one:

* http://jifsan.umd.edu/pdf/gaqps_en/14%20GAqPs%20Manual%20SOPs.pdf

* http://foodsafety.unl.edu/haccp/prerequisites/sop.html

I have developed an instructional template with forms and examples called */Good Agricultural Practices Fresh Produce Safety Plan for Field Practices./* The plan is available electronically as a printable guide (pdf) or an editable document (MS Word). To download the plan, please visit the N.C. Fresh Produce Safety Blog: https://ncfreshproducesafety.wordpress.com and click on “Good Agricultural Practices Fresh Produce Safety Plan for Field Practices Template” in the left column.

/Additional Food Safety Plan resources can be found on www.ncmarketready.org <http://www.ncmarketready.org/> and click on “Fresh Produce Safety” on the left menu bar and choose “Food Safety Plans” on the left column/.

Q23. He needs more information on the chlorine tabs for the water. Where do you get those and how often are they used?

A23. There are several publication that accurately address the use of chlorine with produce.

_*UC Davis PostHarvest Technology* *website*_ http://postharvest.ucdavis.edu/postharvestdata/datareport.cfm?reportnumber=204&catcol=1809&categorysearch=Water%20Disinfection

*Water Disinfection: A Practical Approach to Calculating Dose Values for Preharvest and Postharvest Applications * <http://postharvest.ucdavis.edu/datastorefiles/234-405.pdf> http://postharvest.ucdavis.edu/datastorefiles/234-405.pdf
***Postharvest Chlorination: Basic Properties and Key Points for Effective Disinfection* <http://postharvest.ucdavis.edu/datastorefiles/234-404.pdf>*
Chlorine Use In Produce Packing Lines*_
*Oxidation-Reduction Potential (ORP) for Water Disinfection Monitoring, Control, and Documentation* <http://postharvest.ucdavis.edu/datastorefiles/234-406.pdf>*

* This article addresses what chemical combinations to avoid in dump tanks.


Q24. Washing produce. How do you wash the produce? Some fruits (strawberries, tomatoes) don’t do as well when washed then stored.

A24. Not all produce should be washed as it can effects the posthavest quality and shelf life. Growers should indicate to consumer that the produce has not been washed and encourage them to wash at home before eating. Washing produce before consumption is recommended, but doesn’t guarantee that produce will be free of pathogens. Studies have demonstrated that washing produce in cold chlorinated water will reduce microbial populations by 2 or 3 logs (Zhuang et al, 1995), but to-date there is no wash water treatment that can eliminate pathogens from produce. Growers should follow postharvest handling recommendation for their specific fruits and vegetable. While the below guides do not address specific use of wash water in postharvest handling, general guidance for the use of ice can help guide growers.

* National Sustainable Agriculture Information Service has a
publication that covers postharvest practices suitable for
small-scale operations, and points out the importance of
production and harvesting techniques for improving quality and
storability. http://attra.ncat.org/attra-pub/postharvest.html

* The Commercial Storage of Fruits, Vegetables, and Florist and
Nursery Stocks http://www.ba.ars.usda.gov/hb66/130strawberry.pdf

Q25. Where does Aflatoxin fit in? How to destroy it? What crops associated with?  How to recognize?

Q26. What is the research behind the uptake of soilborne pathogens by the roots of vegetables?

This research was done under ideal, laboratory conditions with very large quantities of inoculum.  I found one study that showed this result.

  • Bernstein, Nirit; Sela, Shlomo; Neder-Lavon, Sarit.  Assessment of Contamination Potential of Lettuce by Salmonella enterica Serovar Newport Added to the Plant Growing Medium.  Journal of Food Protection®, Volume 70, Number 7, July 2007 , pp. 1717-17  Abstract:  The capacity of Salmonella enterica serovar Newport to contaminate Romaine lettuce (Lactuca sativa L. cv. Nogal) via the root system was evaluated in 17-, 20-, and 33-day-old plants. Apparent internalization of Salmonella via the root to the above-ground parts was identified in 33- but not 17- or 20-day-old plants and was stimulated by root decapitation. Leaves of lettuce plants with intact and damaged roots harbored Salmonella at 500 ± 120 and 5,130 ± 440 CFU/g of leaf, respectively, at 2 days postinoculation but not 5 days later. These findings are first to suggest that Salmonella Newport can translocate from contaminated roots to the aerial parts of lettuce seedlings and propose that the process is dependent on the developmental stage of the plant.
  • Specialist, Dr. Chris Gunter at NCSU, stated that this is phenomenon is not likely.
  • A study conducted in Norway showed that there was no uptake of E. coli 0157: H7.
  • Gro S. Johannessen,1,3* Gunnar B. Bengtsson,2 Berit T. Heier,1 Sylvia Bredholt,2 Yngvild Wasteson,3 and Liv Marit Rørvik.  Potential Uptake of Escherichia coli O157:H7 from Organic Manure into Crisphead Lettuce,  Appl Environ Microbiol. 2005 May; 71(5): 2221–2225. Abstract:  To investigate the potential transfer of Escherichia coli O157:H7 from contaminated manure to fresh produce, lettuce seedlings were transplanted into soil fertilized with bovine manure which had been inoculated with approximately 104 CFU g−1 E. coli O157:H7. The lettuce was grown for approximately 50 days in beds in climate-controlled rooms in a greenhouse. As the bacterium was not detected in the edible parts of the lettuce, the outer leaves of the lettuce, or the lettuce roots at harvest it was concluded that transmission of E. coli O157:H7 from contaminated soil to lettuce did not occur. The pathogen persisted in the soil for at least 8 weeks after fertilizing but was not detected after 12 weeks. Indigenous E. coli was detected only sporadically on the lettuce at harvest, and enterococci were not detected at all. The numbers of enterococci declined more rapidly than those of E. coli in the soil. Pseudomonas fluorescens, which inhibited growth of E. coli O157:H7 in vitro, was isolated from the rhizosphere.
  • A similar study, showed similar results.  Hora, Rajneesh; Warriner, Keith Shelp, Barry J. Griffiths, Mansel W.  Internalization of Escherichia coli O157:H7 following Biological and Mechanical Disruption of Growing Spinach Plants   Journal of Food Protection®, Volume 68, Number 12, December 2005 , pp. 2506-2509(4).

Q27. How can you treat rainwater used for mushroom culture in a way that will not also harm the mushroom spores?

Q28. Can foodborne pathogens persist in worm castings that are used as a soil amendments?

From Dr. Rhonda Sherman, Extension Solid Waste Specialist, Biological and Agricultural Engineering, NCSU (919.515.6770, rhonda_sherman@ncsu.edu)

  • I regularly caution people about the possibility of foodborne pathogens in vermicompost.  If food waste containing significant levels of pathogens such as e. coli and salmonella is added to worm bins, there is a chance that the pathogens could end up in the vermicompost.  However, it is unlikely if the worm bin is being operated correctly.
  • Some studies have been conducted on pathogen reduction via vermicomposting. One study was published in Compost Science & Utilization, (2001), Vol. 9, No. 1, 38-49. “The Effectiveness of Vermiculture in Human Pathogen Reduction for USEPA Biosolids Stabilization” by Bruce R. Eastman1, Philip N. Kane2, Clive A. Edwards3, Linda Trytek4, Bintoro Gunadi3, Andrea L. Stermer1 and Jacquelyn R. Mobley 1; 1. Orange County Environmental Protection Division, Orlando, Florida, 2. Florida Department of Environmental Protection, Orlando, Florida 3. Soil Ecology Laboratory, Ohio State University, Columbus, Ohio, 4. Tri-Tech Laboratories, Inc., Orlando, Florida. The researchers made two windrows containing dewatered biosolids between 15 and 20 percent solids from a wastewater treatment plant. They added high levels of four types of common human pathogens to both windrows. Eisenia fetida earthworms (red wigglers) were added to one of the windrows. After 144 hours, the windrow with earthworms had significantly less pathogens than the control windrow. The test indicated that all of the pathogen indicators in the test row were decreased more than in the control row within 144 hours. The test row samples showed a 6.4-log reduction in fecal coliforms compared with the control row, which only had a 1.6-log reduction. The test row samples showed an 8.6-log reduction in Salmonella spp., while the control row had a 4.9-log reduction. The test row samples showed a 4.6-log reduction in enteric viruses while the control only had a 1.8-log reduction. The test row samples had a 1.9-log reduction in helminth ova while the control row only had a 0.6-log reduction. The study can be read on Ohio State University’s website.
  • Go to my website at http://www.bae.ncsu.edu/people/faculty/sherman and scroll down to “For more information…” and click on “Vermicomposting.” Scroll down to Soil Ecology Lab at Ohio State University.
  • NCSU 10th Annual Vermiculture Conference May 27-28, 2010 http://www.bae.ncsu.edu/workshops/worm-conference/

Q29. Can respiratory illness be spread on fresh produce?

From Dr. Ben Chapman:

  • No, the respiratory pathogens  (H1N1, rhinovirus) are not foodborne pathogens — they have to be inhaled and make it into the respiratory system to infect. Respiratory illness infected folks are theoretically more of an physical risk (snot and such). Respiratory-infected folks may shed (through runny noses) staph from their noses more than others but that would only really be a growth problem in fresh cut.