UCGAPs Suslow 6/17/2010

Transcription

1 Overview of postharvest water applications Postharvest washing efficiencies Mechanical removal of pathogens Overview of disinfection: Goals and Options Emerging audit compliance standards Trevor Suslow Dept. of Plant Sciences Trevor Suslow Dept. of Plant Sciences The Predominant role of Disinfection is to prevent ti introduction ti and dt to minimize i i re-distribution ib ti of plant and human microbial pathogens in water Tertiary Wash 99.9% Removal Primary Wash 93% Removal Triple washed cilantro leaves (T. Suslow 1999) 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 1

2 S. enterica [GFP] on cilantro leaf 6 days after inoculation and vigorous washing Interactions between Food Borne Pathogens and Protozoa Isolated from Lettuce and Spinach. Gourabathini et al AEM p Vesicles with GFP labled EcO157:H7 Protozoa Glaucoma sp. Courtesy: Maria Brandl, USDA/ARS Enhanced Survival of Salmonella enterica in Vesicles Released by a Soilborne Tetrahymena Species. Brandl et al AEM p Tetrahymena with Salmonella vesicles Salmonella survival free floating or in vesicles Infiltration ti occurs: When outside water enters the produce In produce with air spaces within cellular tissues Temperature differential (water colder than produce) Causes air in cell space to contract Draw water in through pores, channels, bruises Photo courtesy: M.J. Mahovic, UF/IFAS Apples Melons Peppers Spinach Mango Citrus Temp Pressure Time Depth Water deficit Vacuum Fruit pulp should be 10 o F (6 o C) cooler than water temperature to prevent infiltration. Microbes in water Adequate water sanitation will minimize problems Pre-Cooling Operations: HydroVac Ice Injection Hydro-Cooling Wash and Dip Tanks Flume Wash Systems Spray Wash Systems Ice-making Cooling Canals tvsuslow@ucdavis.edu 2

3 Potential Transfer of Salmonella during Postharvest Handling Examples Brush bed Jacuzzi bath Ultrasonic bath CO 2 cavitation Disinfection treatment of postharvest water maintains cleanliness of brushes and rollers Water and Immersion only Water and Brush bed ClO2 and Immersion only ClO2 and Brush bed Pao et al Journal of Food Protection722: What is the origin of micro loading to dump tanks when bin dumping occurs in packing houses tvsuslow@ucdavis.edu 3

4 Sample Location Code Roma-type incoming Mature Green Incoming Fruit average log CFU/fruit (25 fruit/sample sample) PCA ECC-TC ECC-E. coli (presumptive) < Maintain consistent sanitizer levels in dump tanks and spray washers Regularly check automated sanitizer equipment during daily packing Double check automated equipment with manual methods Multiple utpec chemical ca choices ces Multiple product types Diverse microbe types Different load throughput Varying wash/cooling conditions Different equipment designs Different retention times Log CFU/fruit Start up + 3h TPC Total Coliform E. coli Unwashed T Unwashed T Washed T Washed T N = 25 Non Chemical Ultra Violet Ultra Filtration Chemical Oxidizer Oxidizer and Acid Non Oxidizer tvsuslow@ucdavis.edu 4

5 Self purging filtration Flume Flocculant Chlorination Hypochlorous Acid (HOCl HOCl) + ROS Chlorine Gas Sodium Hypochlorite Calcium Hypochlorite Chlorine Dioxide Chlorobromination Peroxyacetic Acid or Hydrogen Peroxide Ozone Copper ions + low HOCl (+ Silver ions) Sodium Hypochlorite (liquid) Most widely used method Relatively inexpensive Readily available and flexible Easy to adopt for small scale scale Broad spectrum of activity (yeasts, molds, bacteria, algae, many viruses) Less effective for parasite cysts, some fungal spores Total Chlorine Combined Chlorine Free Chlorine ph HOCl OCl % 5% % 20% % 50% % 80% tvsuslow@ucdavis.edu 5

6 e Form % Free Chlorine HOCl Highly active OC (32F) 20C (68F) Solution ph 30C (86F) OClless active Potential for toxic chlorine gas formation Poor penetration of biofilms and scale Corrosive Irritation (eye, respiratory, mucus membrane) Unstable (ph < 4, high temp), short half-lifelife Formation of potentially toxic by-products (THM s, chloramines) Potential for sodium injury (ex. some apples) 68% Ca(OCl)2 tablets tvsuslow@ucdavis.edu 6

7 120 Effect of EOW on Penicillium digitatum conidia in water % Kill Decay Incidence (% of fruit Time (Secs) Adapted from Whangchai et al 2009 Acta Hort. 837 ISHS ppm HOCl ph 4.8 Tangerine Storage Time (Days)@ 5C (40F) Adapted from Whangchai et al 2009 Acta Hort. 837 ISHS Oxidizer 2.5x more effective than chlorine Low Sodium, Low Chlorite Does not form by products THMs /DBP s Does not form chloramines Effective at wide ph ranges Good bioflim penetration Approved in U.S. for 5 ppm for 1 min treatment of whole and fresh cut fruits and vegetables with no rinse requirement Using Aqueous Chlorine Dioxide To Prevent Contamination of Tomatoes with Salmonella enterica and Erwinia carotovora during Fruit Washing PAO et al. JFP 2007 p Inoculum in Water Wet Inoculum Dose Range 0 ppm 5 ppm 10 ppm 20 ppm Dry Inoculum Time ; 0 60 sec Using Aqueous Chlorine Dioxide To Prevent Contamination of Tomatoes with Salmonella enterica and Erwinia carotovora during Fruit Washing PAO et al. JFP 2007 p tvsuslow@ucdavis.edu 7

8 Washing Conditions Sample Type Trihalomethane DBP (μg/l) Municipal Water Process Cooling Water <5 Washed Lettuce <5 Chlorine dioxide system: On-site chemical generator Two-chemical less expensive Three chemical more efficient conversion NaOCl (100 ppm) + COD@ 700ppm Process Cooling Water 217±38 30 min Washed Lettuce <5 Washed and rinsed Lettuce <5 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 3618±633 Washed Lettuce 540±141 Process Cooling Water <5 Washed Lettuce <5 Washed and rinsed Lettuce <5 Highly effective oxidizer No residual concerns converts to Oxygen Negligible DBP s Kills pathogens Cl doesn t A little too reactive Unstable (short half life) Concentration (ppm) Ozone Degradation in Postharvest Water Time (minutes) Municipal Water Recycled Water Unstable (short half life) Low solubility; best in cold water Difficult to monitor concentrations Difficult to adjust needs based on demand May require use of secondary disinfectant Must be generated on site Worker Safety Issues, Toxicity Highly Corrosive and Degenerative H 2 O 2 + CH 2 COOH H 3 COOH Hydrogen Acetic Peroxyacetic Peroxide Acid Acid tvsuslow@ucdavis.edu 8

9 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 Corrosive to soft metals and skin Strong, pungent odor of concentrate and dilute forms (worker discomfort & safety) Varied activity against fungi Build up of acetic acid in water; translucency Need to monitor water turn over closely Prolonged exposure may cause product damage Flume Line Shed A Flume Line Shed B Quality Turbidity (FAU) Conductivity 1558 ms 721 ms ph Free Cl ORP Total fecal coliform log 5.4 CFU/100ml < 0.9 log CFU/100ml Spot Checking Chemical Test Kit Chemical Test Strips Colorimeter Direct Measurement Meter Portable ORP and ph Meter Fixed Continuous Meter ORP and ph Meter Direct Ion Sensor tvsuslow@ucdavis.edu 9

10 Fast Spot Checking Simple Dip & Read 1 Step Colorimetric Analysis Visual Reading Low Cost IS THIS FLUME WATER IN GOOD SHAPE? Water Quality Measurements Oxidation Reduction Potential ( mv) Predicts Disinfection Potential Measures Disinfection Potential NOT ppm Single Value Assessment of Disinfection ph ORP (mv) Time of Sampling Following Day Time Temp (tank) Temp (bag) ph ORP ph ORP EC Turbidity Free Cl- TSS Water Source C C mv mv ms FAU mg/l Dump (Time 0) 12:35pm Dump (Time 2h) 2:40pm Flume (Time 0) 12:40pm Flume (Time 2h) 2:45pm ORP mv; ph Log CFU/100ml TPC Total E.coli Coliform Dump T Dump T Flume T Flume T N = 6; n = 12 Water Quality Measurements Time of Sampling Following Day Time Temp (tank) Temp (bag) ph ORP ph ORP EC Turbidity Free Cl- TSS Water Source C C mv mv ms FAU mg/l Dump (Time 0) 4:00pm Dump (Time 2h) 5:00pm Flume (Time 0) 4:15pm Flume (Time 2h) 5:10pm ORP mv; ph 8.8 Log CFU/100ml TPC Total E.coli Coliform Dump T Dump T Flume T Flume T N = 6; n = 12 Rate of diffusion of free chlorine through the membrane depends on temperature sensor response must be corrected for changes in membrane permeability Temperature compensated sensors ph compensated sensors tvsuslow@ucdavis.edu 10

11 Comparative Oxidative Disinfection Potential: Penicillium expansum Treatment 100 ppm Cl 100 ppm Cl 200 ppm Cl 200 ppm Cl MWS ph Free Cl ORP (mv) % Spore Kill 15 secs % Spore Kill 5 min NaOCl (bleach) ph endpoint Measured Free Chlorine (ppm) Municipal Water Source unadjusted Municipal Water Source adjusted MWS +100ppm unadjusted MWS +100ppm adjusted MWS +200ppm unadjusted MWS +200ppm adjusted ORP value (mv) Approx 6-log Inactivation Time (low burden water) E. coli Fecal Coliform > 1h >1h > 30min >1h < 15s <60s <10s <10s <10s <30s <10s <10s Example of relationship between chlorine, adjusted and non adjusted ph, ORP, and bacterial inactivation Comparison of Peroxyacetic Acid Concentration and ORP ORP (mv) ph 5.2 Municipal Water Tsunami 100 PeraSan Biocide HS Issue: Data from bench top and small scale studies may over or under predict efficacy Example: ORP sensors for chlorine dosing Dose (ppm) ph Temp = 2.5C T. Suslow UCD; unpublished data Electromagnetic interference ( EMI) creates a disturbance that affects an electrical circuit due to either electromagnetic conduction or electromagnetic radiation emitted from an external source. Broadband interference from electric motors Degrades the performance of a sensor circuit ORP and Ion Specific sensors reported to have limited EMI immunity 2010 tvsuslow@ucdavis.edu 11

12 POSTHARVEST AUDIT METRICS C. Product Water Management Q# Requirement Procedure Verification Corrective Action/ Disposition 2.15 Re-circulated and re-used water is changed at least daily, and records of changes are kept. Operation shall maintain records to demonstrate water changes. Water may be used for longer than daily if a validated regeneration system (e.g., a water pasteurization/filtra tion system) is being used. Auditor reviews records to verify at least daily changes of all wash water. Procedure is developed or revised. Retraining is performed If water quality is based upon a chlorine-based sanitizer and Oxidation Reduction Potential (ORP), the process shall be targeted to be at least 800 mv. ORP levels shall not be less than 650 mv, measured at the exit of the product from the water system, unless validation data are available to demonstrate a lower ORP is effective under operating conditions. Operation shall have a procedure to manage ORP levels, shall establish process adjustments for when the ORP drops below 800 mv, and shall maintain records to verify proper management of levels. Auditor shall review the procedure and shall review records of ORP measurement and appropriate management. Auditor reviews records for deviations and their disposition. Procedure is developed or revised. Retraining is performed. Tomatoes washed in water at ORP less than 650 mv shall be discarded back to the last evidence of compliance If water quality is based upon an aqueous chlorine dioxide sanitizer, chlorine dioxide levels shall not be less than 1 ppm,measured Operation shall have a procedure to manage aqueous chlorine dioxide levels, shall establish process targets so as not to drop below the minimum ppm, shall establish adjustments for Auditor shall review the procedure and shall review records of aqueous chlorine dioxide measurement and appropriate management. Auditor reviews records for deviations and their at the exit of when the chlorine disposition. the product dioxide drops below from the water the target ppm, and system, unless shall maintain validation data records to verify are available to proper management demonstrate a of levels. lower ORP is effective under operating conditions. Procedure is developed or revised. Retraining is performed. Tomatoes washed in water at less than 1 ppm aqueous chlorine dioxide shall be discarded back to the last evidence of compliance. The potential risks of waterborne contamination demand special attention for Quality and Safety Select disinfectant on microbial reduction objectives Weigh the pros and cons of each sanitizer to find the one that s right for your operation How Do I Calculate How Much Bleach To Add To My Wash Tank? (target ppm of Free Chlorine) x (total tank volume) x conversion (% NaOCl in source) x (10,000) = Volume to add Example: I want 100 ppm to wash cucumbers. 100 ppm x 50 gallons x 128 oz./gallon 5.25% NaOCl x 10,000 ppm/% = 12 oz or 1.5 cups 100 ppm x 189 liters 5.25% NaOCl x 10,000 ppm/% = 0.36 liters or 360 ml or 1.5 cups tvsuslow@ucdavis.edu 12