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1 UC Postharvest Technology of Horticultural Crops June 19, 2014 Trevor Suslow UC Davis Dept. Plant Sciences Treatment of process water to inactivate ; Pathogenic bacteria Plant pathogens Human pathogens Spoilage Microbes Fungi Bacteria Yeast Human Parasites Viruses Human pathogens Field Harvest Operations Cleaning knives Cleaning tools Field packed products tvsuslow@ucdavis.edu 1

2 Rinsing/Washing product Wash and dip tanks Flume wash systems Spray wash systems Pre cooling operations after harvest (remove heat field) Top icing of broccoli Hydro cooling by water spray Hydro cooling by drench shower 2

3 The role of process water disinfection is to prevent and to minimize the redistribution of plant and human pathogens from incoming produce into the water Prevent crosscontamination The reduction of the microbial load on plant and fruit surfaces is a secondary consequence Tertiary Wash 99.9% Removal Primary Wash 93% Removal Triple washed cilantro leaves Unwashed E. coli on lettuce Washed E. coli Post washed E. coli 100 ppm Hypochlorite Lopez Galvez, F., et al., Cross contamination of fresh cut lettuce after a short term exposure during prewashing...,food Microbiology (2009) tvsuslow@ucdavis.edu 3

4 Water utilized for post harvest operations will be in direct contact with raw product Incoming Lettuce leaves Contaminated with E. coli Batch 1 Incoming Lettuce leaves Batch 2 Clean process water Contaminated water With E. coli Lettuce leaves Contaminated with E. coli Batch 1 Lettuce leaves Contaminated with E. coli Batch 2 Water utilized for post harvest operations will be in direct contact with raw product Incoming Lettuce leaves Contaminated with E. coli Batch 1 Incoming Lettuce leaves Batch 2 Clean CROSS process water CONTAMINATION Contaminated water With E. coli Lettuce leaves Contaminated with E. coli Batch 1 Lettuce leaves Contaminated with E. coli Batch Cl + Citric acid (ph 6.5) SmartWash 1 wash tank 2 wash tank 4 ppm Cl 15 ppm Cl log CFU/g LOD Time (min) tvsuslow@ucdavis.edu 4

5 Lactic Acid & Phosphoric Acid Needs adequate contact time Combined with plant extract surfactants 5

6 Not all state Department of Public Health will ignore this discrepancy 6

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8 celery load 30% water exchange 1 celery load THE WATER 425 TPLB CFU/100 ml 685 TPLB CFU/100 ml Cooling Cycle THE PRODUCT TPLB CFU/25g 685 TPLB CFU/25g TPLB Total pectolytic bacteria Cooling Cycle tvsuslow@ucdavis.edu 8

9 Apples Cantaloupe Peppers Spinach Mango Citrus Cucumber Squash Temp Pressure Depth Water deficit Vacuum credit: M.J. Mahovic, UF/IFAS Fruit pulp must be < 10F {6 o C} warmer than water temperature to prevent infiltration. Microbes in water Adequate water sanitation will prevent problems Attachment to stem scar and micro wounds is still a cross contamination issue Examples Jacuzzi bath Ultrasonic bath CO 2 cavitation tvsuslow@ucdavis.edu 9

10 Ultrasonic washing High frequency ultrasound (1-10 MHz) khz for sensitive products Combination with water disinfectant CO2 All solutions were less effective at 4C compared to 24C irrespective of the presence of surfactants. Nonionic surfactants could potentially be used with NaOCl to improve control of P. expansum in flotation tanks, but the efficacy of such formulations should be validated under apple packing conditions. 10

11 Multiple chemical choices Multiple product types Diverse microbe types Different load throughput Varying wash/cooling conditions Different equipment designs Different retention times Non Chemical Ultra Violet Ultra Filtration Chemical Oxidizer Oxidizer and Acid Non Oxidizer High performance UV disinfection system 11

12 Oxidizing Reagent Oxidizing Potential Ozone 2.07 Hydrogen Peroxide 1.77 Permanganate 1.67 Hypochlorous Acid 1.49 Chlorine Gas 1.36 Hypobromous Acid 1.33 Oxygen 1.23 Bromine 1.09 Hypoiodous Acid 0.99 Chlorine Dioxide 0.95 Hypochlorite 0.94 Chlorite 0.76 Iodine 0.54 Chlorine Gas Sodium Hypochlorite Calcium Hypochlorite Chlorine Dioxide Acidified Sodium Chlorite Electrolyzed Oxidizing Water Chlorobromination Peroxyacetic Acid or Peroxyoctanoic Acid Hydrogen Peroxide Carbonic Acid Ozone Copper ions + low HOCl (+ Silver ions) ph (acidity) Critical when hypochlorite is used Use of food grade organic acids to maintain right ph values (citric acid) Phosphoric Muriatic HCl Water temperature May be a factor Cooling may be decision factor Some systems use heated water Water turbidity Soil, dirt, leaves, debris tvsuslow@ucdavis.edu 12

13 Moderate Impact Iron Manganese Chloramine Nitrites (NO 2 ) Hydrogen sulfide (H 2 S) Sugars Starches from harvest wounds Strong Impact Ammonia Copper Nickel Cobalt Proteins from harvest wounds Amino acids UV direct sunlight Strong acidity (very low ph) Tri Halo Methane (THMs) Chlorine, Bromine, Iodine Drinking water research indicates that certain byproducts of water disinfection have the potential to be harmful. Some research indicates that certain byproducts of water disinfection are linked to increases in cancer incidence, including bladder cancer. Some research indicates that certain byproducts of water disinfection can be linked to liver, kidney, central nervous system problems, and reproductive effects. Some research indicates that certain byproducts of water disinfection can be linked to anemia. tvsuslow@ucdavis.edu 13

14 Oxidizer 2.5x more effective than chlorine (more killing) No formation of by products Effective at wide ph ranges Regulated dose limitations (3 5ppm) Requires potable rinse (<0.8 ppm) Washing Conditions Sample Type Trihalomethane DBP (μg/l) Municipal Water Process Cooling Water <5 Washed Lettuce <5 NaOCl (100 ppm) + COD@ 700ppm 30 min NaOCl (700 ppm) + COD@ 1800ppm 60 min ClO2 (3.7 ppm) + COD@ 700ppm 30 min F. López Gálvez et al. / Postharvest Biology and Technology 55 (2010) Process Cooling Water 217±38 Washed Lettuce <5 Washed and rinsed Lettuce <5 Process Cooling Water 3618±633 Washed Lettuce 540±141 Process Cooling Water <5 Washed Lettuce <5 Washed and rinsed Lettuce <5 tvsuslow@ucdavis.edu 14

15 Trevor Suslow UC Davis Dept. Plant Sciences 15

16 Monochloramine is commonly used as a secondary disinfectant to protect the water as it travels from the treatment plant to consumers. Monochloramine is effective in killing bacteria, viruses, and other potentially harmful organisms. Monochloramine produces fewer potentially harmful currently regulated disinfection by products than chlorine. Monochloramine can react with natural organic matter present in water to form potentially harmful disinfection byproducts. Many municipal and private water districts, seasonally, use high rates of chloramines that can release irritating offgassing if acid injection is not well controlled and distributed in wash system. tvsuslow@ucdavis.edu 16

17 :36:34 AM 8:16:34 AM 8:56:34 AM 9:36:34 AM 10:16:34 AM 10:56:34 AM 11:36:34 AM 12:16:33 PM 12:56:33 PM 1:36:33 PM 2:16:33 PM 2:56:32 PM ph Line 3 **= Cl Addition Even in well managed wash systems, ph control can fluctuate outside of the desired control range for minutes at a time Line 2 8:06:24 AM 8:38:25 AM 9:10:24 AM 9:42:24 AM 10:30:24 AM 11:02:24 AM 11:34:23 AM 12:06:23 PM 12:38:24 PM 1:10:23 PM 1:42:24 PM 2:14:23 PM 2:46:23 PM 3:18:22 PM ph Line 2 ph Line 3 (Set point 6.0) J. Brennan; New Leaf Foods Determine the concentration of the disinfectant agent 75 to 200 ppm of sodium hypochlorite Up to 5 ppm for chlorine dioxide Determine the oxidative state of the water (how much disinfection potential is there?) Oxidation reduction potential (ORP) Measures disinfection potential not ppm >650 mv (most systems mv) % Free Chlorine Form HOCl Highly active Solution ph OC (32F) 20C (68F) 30C (86F) OClless active tvsuslow@ucdavis.edu 17

18 How well is ph controlled? Does automated chlorine deliver system keep up with demand? Do you achieve the product surface contact and residence time needed? Validation Do we understand the critical conditions for controlling the process? A systematic data gathering and process design under controlled conditions Verification Can we demonstrate the validation criteria are being satisfied on site? Operational data gathering within variation of the system process control tvsuslow@ucdavis.edu 18

19 Definition A Stable Process has the same normal distribution at all times. A stable process is In Control A stable process still has variation Stable Process Prediction Time A stable process still has variation Normal distribution at all times?? Prediction Time Any process that is not stable is called an unstable or out of control process. tvsuslow@ucdavis.edu 19

20 NaClO 2 + H + Any GRAS acid HClO 2 ph ASC results by acidification of NaClO 2 solution (e.g. citric acid) Dose ranges between ppm (FDA) No by products formation log 3,0 2,5 2,0 1,5 1,0 High doses can result in damages of tissue surface Acidic nature: effect on equipment?? 0,5 0,0 500 Dose (mg L -1 ) time (s) Effect of ASC and contact time on E. coli reduction of inoculated Tatsoi leaves. Tomas Callejas et al. (2011) Effect of EOW on Penicillium digitatum conidia in water % Kill Time (Secs) Adapted from Whangchai et al 2009 Acta Hort. 837 ISHS ppm HOCl ph 4.8 Peroxyacetic Acid Sanitizers Approved as water treatment May require post treatment rinse Approved for all food contact surfaces Mode of Action: Causes oxidation of cellular constituents Metabolic poison cell death appears to continue in storage tvsuslow@ucdavis.edu 20

21 Less impacted by organic matter and soil Low foaming Very good biofilm penetration Very good on molds and spores Oxidizer and Metabolic Poison No residue or DBP s Breaks down to water, oxygen and acetic acid Generally non corrosive Perceived disadvantages Unit cost is higher than sodium hypochlorite In reality, requires complex comparisons Will cause injury to some tender commodities Typically a problem of infrequent water turn over Pungent odor and irritation at higher doses Generally only with high aerosolization tvsuslow@ucdavis.edu 21

22 Low voltage electrodes release ions in water stream Research supports efficacy Cooling towers Ponds and pools Well water holding tanks Very stable in clean water systems Very slow acting Performance requires low chlorination Disinfectant Concentration 5 sec 10 sec 15 sec 30 sec 45 sec 1 min 2 min 5 min 10 min 20 min 60 min 90 min 2 h Copper Free Chlorine Copper + Free Chlorine 1 ppm ppm ppm ppm ppm Cu : 2 ppm Cl ppm Cu : 2 ppm Cl Inoculated with 10 million cells of E.coli O157:H7 tvsuslow@ucdavis.edu 22

23 Hydrogen Peroxide: % Peroxyacetic Acid:...5.3% INERT INGREDIENTS: % Dose volumes provided in the charts are calculated to achieve practical ppm (parts per million) of 100% peroxyacetic acid based on labeled percent composition Trevor Suslow Extension Research Specialist UC Davis Department of Plant Sciences Wash Water Basin or Tank (gallons) Target Dose (values are fully rounded* ounces of SaniDate 5.0/tank working volume) 20 ( Common treatment for ag chemical spray tanks) (Common wash water dose) Maximum label dose * For simplicity in measuring, the volumes to be added to the tank mix are rounded up to an even number. The values provided are not intended to achieve a precise dose but, rather, make routine additions on smallfarm and packing facility operations easy and reproducible. Wash Water Basin or Tank (gallons) 20 ( Common treatment for ag chemical spray tanks) Target Dose (values are milliliters of SaniDate 5.0/tank working volume) (Common wash water dose) Maximum label dose * For simplicity in measuring, the volumes to be added to the tank mix are rounded up to an even number. The values provided are not intended to achieve a precise dose but, rather, make routine additions on small farm and packing facility operations easy and reproducible. tvsuslow@ucdavis.edu 23

24 Fast Spot Checking Simple Dip & Read 1 Step Colorimetric Analysis Visual Reading Low Cost Chemical Test Kit o Titration visually read o Colorimetric Visual Hand held devices Portable ORP and ph Meters In line Sensors o Measure o Record o Control Free Chlorine still need to know ph Sensor flow cell Chlorine Dioxide Fast Response Membrane or Double Platinum Disc design Auto-flush hourly Daily cleaning HAND-HELD CROSS-CHECK Measurement Range ppm low range ppm standard ppm optional tvsuslow@ucdavis.edu 24

25 New bleach injection system installed Calibrated to wash tank Operators trained Run 4 weeks.great arrival Next 3 shipments increasing problem with pitting Severe pitting day 6.Pack line shut down Direct market no issues not washed What s going on? What would you check? Sensor:Pump failure 1 week chemical inventory used in 2 days Minimal fresh water added over 6 day pack schedule No manual dose cross check Relationship between ORP and ppm in Low Turbidity Water Approx. $ ORP (mv) ph 6 ph 7 ph 8 ph 9 Approx. $ Measured Free Chlorine (ppm) tvsuslow@ucdavis.edu 25

26 E. coli Salmonella Molds Tough Molds Listeria Common Free Cl needed for control ORP (mv) ph 6 ph 7 ph 8 ph Measured Free Chlorine (ppm) TIME OF CONTACT IS IMPORTANT NO FEAR DUDE We re exempt * Most common as Retrospective Data for system improvements Water chemistry affects process control! Packing facility water should be analyzed for: Hardness both Ca & Mg Affects ph control, scale, biofilms Silicates Iron Some water conditioning may be required Water Chemistry can vary seasonally & by source Retest or review annually tvsuslow@ucdavis.edu 26

27 Soil + Organic matter reduces disinfection potential NTU FAU (Units of turbidity) Common practice to minimize water consumption and wastewater discharge rates Effectiveness of chemical sanitizer can be affected by water quality Investment in filtration/sedimentation makes all recirculating systems perform better Self purging filtration Flume Flocculant Water turbidity (NTU) Salmonella serovars Time of 5 ppm ClO 2 Newport (PTVS 077) Gaminara (PTVS 041) Poona (PTVS 026) Enteritidis (PTVS 044) Montevideo (PTVS 045) >120 >120 >120 >120 tvsuslow@ucdavis.edu 27

28 WHY COD vs BOD? 1. all organic compounds can be fully oxidized to carbon dioxide with a strong oxidizing agent under acidic conditions 2. COD is few hour test vs BOD is a 5 day test Start Finish Suspended Organics + Acid + K2Cr2O7 (Green) Cr+3 (Orange) 150 C + silver catalyst tvsuslow@ucdavis.edu 28

29 Log CFU/ml Standard limit of detection Time (sec) mg/l O 2 E. coli O157 COD 20 Salmonella COD 20 Listeria COD 20 E. coli O157 COD 140 Salmonella COD 140 Listeria COD 140 E. coli O157 COD 280 Salmonella COD 280 Listeria COD min contact tvsuslow@ucdavis.edu 29

30 1. Preventing cross contamination in wash water requires coordination between field and process 2. COD strongly influences ability to maintain critical dose levels throughout system 3. Setting industry performance standards with single pathogen surrogates is risky 4. Advanced system management is attainable WRAP UP POINTS Water that will be in contact with raw food is likely to become a vehicle to distribute microbial pathogens if a disinfection strategy is not applied There is not a perfect disinfectant! Define the objective of the water disinfection program to achieve microbial reduction objectives FOR THE SYSTEM tvsuslow@ucdavis.edu 30