Wash Water Monitoring in a Field and Facility Packing Operation FAITH CRITZER UNIVERSITY OF TENNESSEE DEPARTMENT OF FOOD SCIENCE & TECHNOLOGY

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1 Wash Water Monitoring in a Field and Facility Packing Operation FAITH CRITZER UNIVERSITY OF TENNESSEE DEPARTMENT OF FOOD SCIENCE & TECHNOLOGY

2 How is wash water applied post harvest? Dump tanks Spray lines Flumes Flotation tanks Hydrocooling

3 Post Harvest Washing Regardless of how water is applied if not properly controlled, a single mistake can impact everything processed Water Only 150 ppm Free Chlorine Salmonella transfer onto tomatoes from one contamination event 218,776 per g of tomato <10 per g (none detected) Salmonella remaining in wash water 4,365,158 per ml of water <1 in 10 ml (none detected) Harness et al 2015

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

5 Water Quality FSMA Requirements: Any postharvest water must not have any detectable generic E. coli per 100 ml You must establish a water change schedule for recirculated water You must visually monitor water for buildup of organic material Other factors such as water hardness also impact antimicrobial activity Picture: T. Suslow, UC Davis

6 Suspended and Dissolved Soils causing Turbidity Interfere with Antimicrobial Activity FAU = NTU The unit of measure for water clarity (dissolved and suspended solids) Slide courtesy of T. Suslow, UC Davis

7 Monitoring Methods Turbidity Meters Modified Secchi Disk

8 Slide courtesy of T. Suslow, UC Davis

9 Antimicrobial Selection, Application, and Monitoring

10 Commonly Used Chemicals in Post Harvest Processing Water Chlorine Sodium hypochlorite (liquid)- e.g. Pac-Chlor, Dixichlor Calcium hypochlorite (powder/tablet)-e.g. Dry Tech FG, Enochlor, ECR Aquafit, Accutab Chlorine dioxide (e.g., Sanova, Oxine, Selectrocide, etc.-clo 2 ) Peroxyacetic acid (e.g., SaniDate, Tsunami, VigorOx, BioSide) Ozone (not common and expensive)

11 Sprays, Dips and Other Solutions There is an extensive list of chemical du jour s. The main thing to consider is if the product has approved for use with the product. Important! Never use a chemical that has not been approved (and only at its approved level) Slide courtesy of K. Schneider, U Florida

12 Weighing Your Options Wash Water Antimicrobials Has it been approved by the EPA? If organic producer, has it been OMRI approved? What is the appropriate concentration for your application? What is the required contact time? What are my monitoring requirements to demonstrate control?

13 Chlorine

14 Chlorination Sodium hypochlorite NaOCl Liquid 5.25 to12.5% Calcium hypochlorite Ca(OCl) 2 Tablets/powder 68%

15 Chlorination (HOCl) Relatively inexpensive Controls cross-contamination- can effectively reduce pathogens in dump tanks, hydrocoolers, etc. Reduces the transfer of decay organisms to healthy fruit. Can kill some existing pathogens on fruit surfaces, but this is where it s least effective 90-99% reduction or 100,000 is reduced to 1,000 or 100, but if we re talking harmful pathogens like Salmonella, that can still make someone sick

16 Factors Affecting Chlorine s Effectiveness Water ph (ClO 2 least affected) Chlorine concentration Contact time Organic matter in the water Water temperature Type of pathogen

17 Practical Applications- Calcium hypochlorite

18 Practical Applications- Calcium hypochlorite 1) Check label for approved use:

19 Practical Applications- Calcium hypochlorite

20 Practical Applications- Calcium Hypochlorite Monitoring- Test Strips Free Chlorine ph Low range and high range to encompass concentrations you may experience You get what you pay for Follow directions- especially with respect to time Inaccurate readings with very turbid/discolored water Test strips can be used in place of meter If you need to acidify inorganic acids (e.g. hydrochloric acid) are recommended

21 Practical Applications- Calcium Hypochlorite Monitoring Oxidation Reduction Potential (ORP) mv Continuous measurement Controller/recorders

22 Peroxyacetic Acid

23 Peracetic Acid H 2 O 2 + CH 3 CO 2 H CH 3 CO 3 H + H 2 O Hydrogen Peroxide Acetic Acid (Vinegar) Peracetic Acid Water ppm peracetic acid common use levels for postharvest water

24 Compared to Chlorine Not as impacted by organic matter Retains activity over wide ph range More expensive

25 Practical Applications- Peracetic Acid

26 Practical Applications- Peracetic Acid

27 Practical Applications- Peracetic Acid Monitoring Test strips- not recommended Titration methods preferred for accuracy Oxidation Reduction Potential (ORP) not accurate for continuous measurement Specialized monitors for inline detection if size/sale warrants

28 Whatever Antimicrobial You Select. Recordkeeping is a must at this point to demonstrate control over washing step

29 Establishing Clean Breaks A clean start-up is recommend Hard to meet initial water quality requirements Carrying over water is a risk for continued contamination if control is lost Limit your losses

30 Thank you! Faith Critzer A BIG THANK YOU TO KEITH SCHNEIDER (UNIV OF FL) AND TREVOR SUSLOW (UC DAVIS) WHO CONTRIBUTED SLIDES