April 6, 2021
In this issue:
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Breakfast with the Food Safety Group
Looking at Surface Water Testing & Evaluating Test Results
Last week we focused on water testing of well water. Many of the same procedures apply when testing surface water. Surface water is defined as any water source which is exposed to the environment. That would include ponds, streams, open cisterns, spring houses, and rain barrels. Pathogens can be moved by windblown dust. Any open body of water has the potential to be contaminated.
The system of pipes and junctions from the water source to the point of use also need to be inspected. PSR, MDA GAP and HGAP require a water risk analysis and inspection of the water distribution system. As with the well water system, a checklist and map can help organize the inspection and assessment. Remember, if water is leaking out of a fitting, contamination can enter the system.
Photo credit, Carol Allen
A risk assessment is a vital part of understanding your water system and being able to both prevent issues with water quality and to be prepared to mitigate any loss of water quality, should it occur. A good explanation can be found in this webinar. https://www.youtube.com/watch?v=9vf8O1aufes&t=12s. Though the intended audience is farms seeking HGAP or HGAP+ certification, the video outlines the basic steps to making a risk assessment.
Water from a pond or similar water source is often pumped from the source to the point of use. When a sample is taken, care should be made to take the sample as close to the intake pipe as possible. If sampling from a pond or stream, try to position the sample bottle in the center of the water column. Don’t drag the bottom where there is a concentration of sediment, nor skim the surface where blown-in dust may be concentrated. If your farm uses several different ponds or other surface water sources, tests must be taken from all water sources used during the crop cycle.
As with water testing from a well, your Maryland State approved lab* will have supplied a sample bottle containing a preservative. Take care not to rinse the bottle before taking the sample. Make sure your hands are clean and wear gloves to ensure your hands do not contaminate the sample. Do not put your fingers inside either the cap or the bottle. Aim to fill the bottle from the center of the water column and fill the bottle to the required line. Cap firmly and place in a sealable plastic bag to contain any leaks. Place on ice or in a refrigerator until delivered to the lab.
The test required by PSR, MDA GAP and HGAP for surface water when used for irrigation, is a quantitative number of generic E.coli. expressed in either Most Probably Numbers (mpn) or Colony Forming Units (cfu) per 100 mL of sample.
MDA GAP and HGAP certifications require an average (samples taken at the beginning, middle and end of the crop cycle) of generic E. coli to be less than 126 cfu/100 mL water. One sample is allowed to be 576 cfu/100 mL water when irrigation water does not touch the edible portion of the crop. Example of that type of irrigation would be drip or furrow.
Irrigation water that does touch the edible portion of the crop, such as sprinkler or overhead, the average should be less than 126 cfu/100mL water. One sample is allowed to be 235 cfu/100mL water, but no greater.
Water testing for compliance to the FSMA, Produce Safety Rule (PSR) is still waiting final guidance by FDA. That guidance is expected to be announced later this year. In the meantime, adhere to the GAP requirements as presented above.
What to Do If the Sample Comes Back Higher Than Allowed
Use an alternative and trustworthy water source until the issues of poor water quality have been mitigated. The possibility of needing an alternative water source should be part of your water risk assessment.
Photo credit, Carol Allen
The first step is to retest. Make sure your handling of the sample was done under clean, aseptic conditions.
If well water was sampled, recheck the conditions of the well head and surrounding area. Are there abandon wells or septic fields nearby that could be sources of contamination? Contact a well service for additional troubleshooting. Shocking the well can return sanitary conditions to the well once any issues have been mitigated.
If surface water was sampled, check for upstream contamination. Your risk assessment should have included nearby land use. Do your neighbors have livestock? Or a poultry operation? Did you test immediately after a rain event? Rain and surface runoff can both stir up and add to the sediment in the water. Sediment can carry pathogens. Check your records. Is a rise in generic E.coli a predictable condition as water temperatures rise in late summer?
Your local agriculture agent or food safety specialist can help work through the process of troubleshooting your water system. Contact Carol Allen (callen12@umd.edu, 240-994-5043) if you farm in southern, central or western Maryland. Contact Angela Ferelli (angfer@umd.edu, 302-353-7159) if you farm north of Baltimore or on the Eastern Shore.
*If you not sure of your closest lab, here is an interactive map that provides the locations of the soil conservation district offices, the agriculture extension offices and the water testing labs. (https://maryland.maps.arcgis.com/apps/webappviewer/index.html?id=4228cc4917f84bc3aea03a00992ea563).
The Plant Science Food Safety Group YouTube Page!
There are signs available through the MDA Food Quality Assurance Program to encourage good consumer practices while in the market and on the farm. Contact the Food Safety Group for availability.
This 12" x 18" poster comes either as a corrugated poster board or as a magnetic sign and is perfect for Pick-Your-Own operations.
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Breakfast with the Food Safety Group from 7:00 - 10:00 am!
We are offering virtual office hours from 7:00 - 10:00 am.
Carol Allen can be reached at 240-994-5043 on Monday, Wednesday & Friday mornings.
Angela Ferelli can be reached at 302-353-7159 Tuesday and Thursday mornings.
Call in with your questions about food safety for fresh produce!
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Carol D. Allen, Agent Associate and Editor
Chris Walsh, Professor Emeritus and Co-PI
University of Maryland
Plant Science Food Safety Group
callen12@umd.edu
Questions for MDA Food Quality Assurance Program:
Deanna Baldwin, Program Manager
Food Quality Assurance Program
Maryland Department of Agriculture
produce.safety@maryland.gov
Funding for this publication was made possible, in part, by the Food and Drug Administration through grant PAR-16-137. The views expressed in written materials or publications and by speakers and moderators do not necessarily reflect the official policies of the Department of Health & Human Services; nor does any mention of trade names, commercial practices, or organization imply endorsement by the United States Government. University programs, activities, and facilities are available to all without regard to race, color, sex, gender identity or expression, sexual orientation, marital status, age, national origin, political affiliation, physical or mental disability, religion, protected veteran status, genetic information, personal appearance, or any other legally protected class
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