Farmers growing produce commonly eaten raw will be contacting water testing labs about new rule

The Food Safety Modernization Act requires quantitative E. coli testing of water used on produce farms. Growers will be looking for local labs.

November 7, 2018 - Author: Benjamin Phillips, Michigan State University Extension

The Produce Safety Rule (PSR) is one of seven rules in the Food Safety Modernization Act (FSMA) coming into effect in the next three years. Growers will be calling labs for water testing, and they will be using new FSMA vocabulary that lab techs and support staff may not have heard before. They must establish a Microbial Water Quality Profile for each of their water sources. The source and use of that water dictates the type and frequency of water test they need performed. The two water types under FSMA are Production Water, and Postharvest Water.

Here is a 1-page printable lab resource for staffers to post near their phones, “Lab resource: Food Safety Modernization Act (FSMA) water testing expectations for farmers who grow produce that is commonly eaten raw.”

Production water

What is it?

Production Water is any water that contacts the harvestable portion of produce during its growth. This includes irrigation, crop protection sprays, frost protection and more.

What sources are there?

Growers use three primary water sources for Production Water, depending on their location. Municipal water sources come from township, city or county water treatment or filtration plants. This water is piped to the farm as a utility service. Groundwater sources come from wells drilled on the farm. Surface water sources are from spring pools, sinkholes, ponds, lakes, rivers, streams, open-air cisterns, reservoirs, etc.

How often do they need to test each water source?

Growers that use municipal water sources for Production Water just need copies of their municipality’s testing records. Growers that use groundwater sources need four quantitative tests in the first year, followed by 1 sample per year after to create a rolling 4-year data set of at least 4 samples. Growers that use surface water sources need 20 quantitative tests in the first 2-4 years, followed by 5 samples per year after to create a rolling 4-year data set of at least 20 samples. Every ground and surface water source on the farm that is used as Production Water must be tested, and regardless of filter systems.

What tests are allowed?

The FSMA PSR currently allows nine enumerative tests. Growers are required to deliver samples to labs within 6 hours of collection. The allowed tests are:

  • Method 1103.1 (mTEC agar)
  • Method 1603 (modified mTEC agar)
  • Method 1604 (MI agar)
  • Method D 5392-93 (mTEC agar)
  • Method 9213 D (mTEC agar)
  • Method 9222 B (m-Endo) followed by 9222 G (NA-MUG agar)
  • Method 9223 B (IDEXX Colilert test kit), with Quanti-tray 2000
  • Method 9223 B (IDEXX Colilert-18 test kit), with Quanti-tray 2000
  • Hach Method 10029 (m-ColiBlue 24 ampules)

What are growers doing with the test results?

Growers are required to maintain a Geometric Mean (GM) and Standard Threshold Value (STV) using the results from the water tests. They must maintain a GM of ≤ 126 CFU or MPN per 100 mL of water and a STV of ≤ 410 CFU or MPN per 100 mL of water. These calculations may be something that an entrepreneurial lab can assist with. There are some pre-made tools available, including the Arizona Ag Water Calculator.

If their water data exceeds either of those thresholds they are allowed to use three Corrective Actions. 1) They can delay harvest after their last use of Production Water on the harvestable portion of the crop for up to four days, accounting for a 0.5 log reduction in bacterial loads per day (see printable lab resource). 2). They can re-inspect the Production Water source and distribution system, fix any problems, document and confirm that the fix was effective with another test. 3). They can treat Production Water with a sanitizer labeled for use on fruits and vegetables or food contact surfaces as applicable.

Postharvest water

What is it?

Postharvest Water is any water that contacts the harvested portion of produce during or after harvest. This includes water used for washing, flume transportation, ice, hydro-cooling, wax/fungicide sprays, etc. Post-harvest water cannot be untreated surface water, even if there are no detectable E. coli. 

What sources are there?

For Postharvest Water, growers are allowed to use any of the aforementioned water sources except untreated surface water.

How often do they need to test each water source?

Growers that use municipal water sources for Postharvest Water just need copies of their municipality’s testing records. Growers that use groundwater sources need 4 tests in the first year, followed by 1 test per year after.

What tests are allowed?

Any one of the aforementioned quantitative E. coli tests are allowed., in addition to the following seven presence/absence tests. Growers are required to deliver samples to labs within 6 hours of collection for quantitative tests, and within 30 hours for presence/absence tests.

  • TECTA EC/TC medium and instrument
  • Modified Colitag, ATP D05-0035
  • IDEXX Colilert test kit
  • IDEXX Colilert-18 test kit
  • IDEXX Colisure test kit
  • E*Colite Bag or Vial test
  • Readycult Coliforms 100

What are growers doing with the test results?

Growers must maintain no detectable E. coli in their Postharvest Water. If water tests detect any E. coli in 100 mL of water, growers can use two Corrective Actions:

  1. They can re-inspect the Postharvest Water source and distribution system, fix any problems, document and confirm that the fix was effective with another test.
  2. They can treat Postharvest Water with a sanitizer labeled for use on fruits and vegetables and/or food contact surfaces as applicable.

Are Michigan labs ready?

To aid growers in finding a local lab, MSU Extension is creating a Google Map (http://bit.ly/MIagwaterlabmap) that highlights labs that offer the tests allowed by the PSR rule, as well as other information that can help growers find your lab to figure out how to get the water tests you need done. If you are a lab who offers one of the above tests and want to be included on this map for Michigan growers, filling out this form (http://bit.ly/MIagwaterlabsurvey) can help growers find you.

For more information on on-farm food safety, as well as updates on the PSR, visit the MSU Extension Agrifood Safety Webpage.

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