Frequently Asked Questions from Farms going through GAPs Audit

Q1: What measures can be taken to deter animals from fields? 

If we see evidence of animals or the physical presences of animals, what are acceptable actions?

What can we do about deterring animals in the pack house (birds, etc)?


 A1: a sample food safety plan has been put together to help growers navigate through some of the details on the 3rd party audits.  You may want to look at website: , under the Food Safety plans the document called “Good Agricultural Practices – Fresh Produce Safety Plan for Field Practices” for some examples of how to deter animals and what some documentation might look like for the field.   Remember that is helpful to identify the risk first, then identify and manage that risk with the various tools that you might have in your particular toolkit!  In the field, SOP 6/0 Animals/Wildlife might have some good suggestions for you.  As far as deterring animals in the packhouse, some general suggestions include the use of bird netting, management of garbage or refuse that will attach animals, active pest management traps and scouting.  Idaho Center for Potato Research &Education has a potato plan reference that might be helpful (, click on the “SOP Appendix”.  Also University of Maine has a good resource for the “Packing House Facility” (


Some additional resources that might be helpful for potatoes:$department/deptdocs.nsf/all/agdex1250/$file/258_65-1.pdf?OpenElement


Q2: Can you clarify/distinguish between what is meant by Climate control vs refrigeration systems in the USDA audit matrix  ( 4-19, 4-20, 4-21)? 

A2: Climate control typically can refer to controlled atmosphere (CA) storage, modified atmosphere (MA) storage and gas storage were the addition or removal of gases resulting in an atmospheric composition different from that of normal air.  The levels of oxygen, carbon dioxide, nitrogen, acetaldehyde  and ethanol can be manipulated in these systems.  This reference might be helpful to help you distinguish your storage practices.

The way that you described your refrigeration would be called forced-air and is very typical.  This publication can help you to understand better the best management practices with this method of cooling.


Q3: Traceability  – what is needed?

A3:   Generally speaking, One step forward and one step back sums it up.

•        A documented traceback program has been established.

•        Finished product is traceable to:

–        the packing house

–       a group of growers/the specific grower

–       a group of orchards or fields/to the specific orchard or field.

–       a group of harvest dates/a specific harvest date

–       a packing date.

•        The operation has performed a “mock recall” that was proven to be effective.

•        Grower

•        Uniquely identify all growers in a value chain

•        Machine readable (barcode or RFID)

•        And human readable (growers name, address)

–       Specific Field location (Premises ID)

•        Coordinates (get a map of your fields online)

•        Use the Farm Service Agency numbers

–       Assign a Product ID for each commodity

–       Identify each picker or group of pickers

–       Date of harvest (and time of day)

–       Date of pack


The Produce Traceability Initiative (PTI) has some good ground rules for the entire fresh produce supply chain to allow for both internal and external traceability- getting everybody to speak the same language.  This might be a valuable resource to consider as you develop your own traceability system.   Check out the website of  We have also provided a structure for traceability in our Tier 2 & 3 trainings which can be found on under “ Trainings & Events”.


Q4: What are the water testing parameters that I need to be looking at?  When do I need to take corrective actions? 

A4: It is important to understand the types of tests available to obtain the bacteria count 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 warm-blooded 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.”

Q5: What is the acceptable PPM of chlorine for potatoes, pH, and temperature?


A5: A good general resource for potatoes is
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:
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.  General postharvest handling parameters which can be found at :
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.
Temperature of the wash water (dump tank, flume, spray bar)  is important as a gradient can be established that would allow for potential contaminants to be infiltrated.  Water temperature should be maintained within 10 degrees F of the product’s pulp temperature to discourage this gradient formation.