Discover the options that are out there, the pros and cons of commonly used sanitizers, the National Organic Program standards for postharvest sanitizers, interpreting sanitizer labels, how to monitor their concentrations and more.

1. Sanitizer Application for
Postharvest Water:
When, Where, Why and How?
Annette Wszelaki + Faith Critzer
University of Tennessee
Vegetable Specialist+
Former Food Safety Specialist

2. Today’s Objectives
After the workshop you will be able to:
1. Establish a monitoring systemfor your wash water
quality.
2. Identify pros and cons of commonly used sanitizers.
2. Differentiate between free and total chlorine.
3. Identify the importance of a compound having organic
approval for contact with produce after harvest.
4. Recognize NOP guidance document 5026 as a key
resource if using chlorine in postharvest water
applications.
5. Measure sanitizer concentrationsin wash water.
6. Identify when, where and how to establish clean breaks.

3. Why Focus on Water?
Criticalpoint capableof amplifyingan error
in sanitationor hygiene management
during production,harvest, or postharvest

5. Critical Factors to Control
Cross-Contamination Risk
Water
Quality
Antimicrobial
Selection,
Application
and
Monitoring
Establishing
Clean
Breaks

6. Water
Quality

7. 0 15 150 300 3000
FAU = NTU
The unit of measure for water clarity
(dissolved and suspended solids)
Suspended and dissolved solids
causing turbidity interfere with
antimicrobial activity
Slide courtesy of T. Suslow, UC Davis

8. Slide courtesy of T. Suslow, UC Davis

9. Monitoring Methods
Turbidity Meters Modified Secchi Disk

10. Slide courtesy of T. Suslow, UC Davis

11. Slide courtesy of T. Suslow, UC
Davis

12. Antimicrobial
Selection,
Application
and
Monitoring

13. Sprays, Dips and Other Solutions
• There is an extensive list of chemicals
• Check product approval (EPA and NOP)
• Important! Never use a chemical that has not
been approved (and only at its approved
level)
Slide courtesy of K. Schneider, University of Florida

14. Commonly Used Chemicals in
Postharvest Processing Water AND
Allowed in Organic Systems
• Chlorine
– Sodium hypochlorite(liquid)- e.g. Pac-Chlor, Dixichlor
– Calciumhypochlorite(powder/tablet)-e.g. Dry Tech FG,
Enochlor, ECR Aquafit, Accutab
• Chlorine dioxide (e.g., Sanova, Oxine, Selectrocide,
etc.)
• Peroxyacetic acid (e.g., SaniDate, Tsunami, VigorOx,
BioSide)
• Ozone (not commonand expensive)

15. • Organic Materials Review Institute (OMRI)
– Reviews products and determine if they are allowed
for use in organic production and processing
– Companies pay a fee to have their products
reviewed/approved by OMRI
– A product DOES NOT HAVE TO BE OMRI APPROVED
to be used in an organic operation
– But products on OMRI list are allowed for use in
organic productionand processing

16. https://producesafetyalliance.cornell.edu/resources/general-resource-listing

17. +
Chlorine

18. Chlorination
• Sodium hypochlorite
– NaOCl
– Liquid
– 5.25 or 12.5%
• Calcium hypochlorite
– Ca(OCl)2
– Tablets/powder
– 68%
• Chlorine dioxide
– ClO2

19. Chlorination (HOCl)
• Relatively inexpensive
• Can effectively reduce pathogens in wash
buckets,dump tanks, hydrocoolers,etc.
• Reduces the transfer of decay organismsto
healthy fruit
• Can kill some existing pathogens on fruit
surfaces, but this is where it’sleast effective

20. Factors Affecting
Chlorine’s Effectiveness
• Water pH (ClO2 least affected)
• Chlorine concentration
• Contact time
• Water temperature
• Type of pathogen

21. Chlorine Dosage

22. Total vs. Free Chlorine
Interacts with inorganic matter
(ex. minerals)

23. Total vs. Free Chlorine
Interacts with inorganic matter
(ex. minerals)
Interacts with organic
matter (ex. soil and plant
matter)
Kill
Microorganisms

24. Free vs. Total Chlorine
• Since free chlorine gives us the antimicrobial
power, that is what we always monitor
• However, free chlorine must be in the
correct form
– Influenced by pH of the water

25. Water pH and Chlorine
Effectiveness
• Hypochlorite and Cl2 form hypochlorous
acid (HOCl)
•THIS is what kills pathogens at neutral (7) pH
NaOCl
Ca(OCl)2
Cl2
HOCl+ H2O

26. High pH
• At high pH, hypochlorous acid
converts to hypochlorite ion (OCl-)
•Hypochlorite ion is relatively
ineffective against pathogens
HOCl H+ + OCl-

27. 0
10
20
30
40
50
60
70
80
90
100
5 6 7 8 9 10
SOLUTION pH
%ChlorineinAvailableForm
OC (32F)
20C (68F)
30C (86F)
Chlorine Efficacy Curve

28. An Example of When
More is Not Better
• Example 1: Let’s use
200 ppm at 6.5 pH
• Example 2: Let’s use
2,000 ppm
– But sincethe addition
of more NaClO will drive
the pH higher, let’s say
the resulting pH will be
8.5 (couldbe much
higher)
• In example 1 the total
active free chlorine is
180 ppm
• In example 2, 200 ppm
• Ten times the
chemistryfor
effectively the same
amount of active
ingredient= 10x the
cost for no more
activity

29. 0
10
20
30
40
50
60
70
80
90
100
5 6 7 8 9 10
SOLUTION pH
%ChlorineinAvailableForm
OC (32F)
20C (68F)
30C (86F)
Example of Free Active Chlorine
200 ppm yields
180 ppm HOCl
@ 6.5 pH
200 ppm yields
100 ppm HOCl
@ 7.5 pH
2,000 ppm yields
200 ppm HOCl
@ 8.5 pH

30. Practical Applications-
Calcium Hypochlorite

31. Practical Applications-
Calcium Hypochlorite
1) Check label for approved use:

32. Practical Applications-
Calcium Hypochlorite

33. Chlorine Monitoring
• Test Strips
– Free Chlorine
• Low range and high range to encompass
concentrations you mayexperience
• You get what you pay for
• Follow directions- especially with respect to time
• Inaccuratereadings with very turbid/discoloredwater
– pH
• Test strips can be used in place of meter
• If you need to acidify, inorganic acids
(e.g. hydrochloric acid)recommended

34. Slide courtesy of T. Suslow, UC Davis

35. Slide courtesy of T. Suslow, UC Davis

36. Chlorine Monitoring
–Oxidation Reduction Potential (ORP)
• 650-800 mV
• Continuous measurement
• Controller/recorders

37. NOP Guidance Document 5026
• Residual chlorine levels in the water shall not
exceed the maximumresidualdisinfectant limit
under the Safe Drinking Water Act (SDWA).
– 4 ppm free chlorine**CA exception to this
• Certified operatorsshould:
– Monitorchlorine level at point where water last
contactsthe organic productin direct
applications.
– A descriptionof the operation’smonitoring
procedure should be contained in their OSP.

38. Washing with Chlorine is a
Two-Step Process
Step 1: Water used in direct
postharvest crop or food contact
is permitted to contain chlorine
materialsat levels approved by
the FDA or the EPA for such
purpose.
Step 2: Rinsing with potable
water that does not exceed 4
ppm must immediatelyfollow
this permitteduse.
penandpepperfarm.com
Do you see a problem
with this approach?

39. A Common Misconception
Washing Will Remove 100%
of Attached Pathogens
Triple washed cilantro leaves
Primary Wash
93% Removal Tertiary Wash
99.9% Removal
Slide courtesy of T. Suslow, UC Davis

40. Issues with Two-Step
Chlorine Washing Approach
• Harmful bacteria may still be
present on produce after first
wash
• Residual chlorinelevels will
easily drop in final rinse step
since there is only 4 ppm
• Risk of cross-contamination will
be likely if you are immersing
produce in water
baybranchfarm.com
Recommendation:
Rinse with potable water in second step- do not immerse!

41. Chlorine as an
Equipment Sanitizer
• Chlorine may be used up to maximum-
labeled rates for disinfecting and sanitizing
– Typically200 ppm free chlorine
• Rinsing is not required unless mandated by
the label use directions.

42. +
Peroxyacetic
Acid
(PAA)

43. Does PAA also have these
limitations?
• NO!
• PAA may be
used as
directed on the
label without a
secondary
washing step USDA

44. Peroxyacetic Acid
aka. Peracetic Acid
H2O2 + CH3CO2H çè CH3CO3H + H2O
Hydrogen
Peroxide
Acetic Acid
(Vinegar)
Peracetic Acid Water
n24-85 ppm peracetic acid common use levels
for postharvest water

45. Compared to Chlorine…
• Not as impacted by
organic matter- big
advantage!
• Retains activity over wide
pH range
• More expensive

46. Practical
Applications-
Peracetic Acid

47. Practical
Applications-
Peracetic Acid

48. Practical Applications-
Peracetic Acid
• Monitoring
– Titration
solutions
– Test stripswill
detect
peroxyaceticacid
and hydrogen
peroxide- giving
you falsely high
readings

49. Practical Applications-
Peracetic Acid
• Monitoring
– OxidationReduction
Potential (ORP) cannot
be used accurately
– Meters specific to PAA
shouldbe used

50. Weighing Your Options for
Wash Water Antimicrobials
• Has it been approved by the EPA?
• Has it been approved by NOP?
• Has it been certified by OMRI?
– Not a requirement, but helps
• What is the appropriate concentration for the
application?
• What is the required contact time?
• What are the monitoring requirements to
demonstrate control?

51. Establishing
Clean Breaks
penandpepperfarm.com

52. Whichever Antimicrobial You
Select….
• Recordkeeping is a must to
demonstrate control over washing step
• Intervals based on throughput
–Ask yourself, “If I check and find I’m
out of control (e.g. concentration too
low), how much product am I
comfortable being implicated?”

53. Food Safety Decision Trees

54. Establishing Clean Breaks
• A clean start-up is recommend
v Start with cleaned and sanitized
equipment and fresh water
• Carrying over water is a risk for continued
contamination if control is lost
v Limit your losses
• Think through order in which you wash

55. Email:
annettew@utk.edu
Phone:
865.974.8332
Thank you!
Questions?