ucgaps suslow 6/17/2010ucce.ucdavis.edu/files/datastore/234-1633.pdfucgaps suslow 6/17/2010...

UCGAPs Suslow 6/17/2010

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Trevor SuslowTrevor SuslowDept. of Plant SciencesDept. of Plant [email protected]@ucdavis.edu

Overview of postharvest water Overview of postharvest water applicationsapplications Postharvest washing efficienciesPostharvest washing efficiencies

Trevor SuslowTrevor SuslowDept. of Plant SciencesDept. of Plant [email protected]@ucdavis.edu

Postharvest washing efficienciesPostharvest washing efficiencies Mechanical removal of pathogens Mechanical removal of pathogens Overview Overview of of disinfectiondisinfection: Goals and Options: Goals and Options Emerging audit compliance standardsEmerging audit compliance standards

The The PredominantPredominant role of role of DisinfectionDisinfection is to is to t i t d ti d t i i it i t d ti d t i i i di t ib tidi t ib tiprevent introduction and to minimize reprevent introduction and to minimize re--distributiondistribution

of plant and human microbial pathogens in water of plant and human microbial pathogens in water

Tertiary Wash99.9% Removal

Triple washed cilantro leaves

Primary Wash93% Removal

(T. Suslow 1999)Lopez‐Galvez, F., et al., Cross‐contamination of fresh‐cut lettuce after a short‐term exposure during prewashing...,Food Microbiology (2009)

Unwashed Unwashed E. coliE. colion lettuceon lettuce

Washed Washed E. coliE. coli100 100 ppmppm HypochloriteHypochlorite

PostPost‐‐washed washed E. coliE. coli


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S. S. entericaenterica [GFP] on cilantro [GFP] on cilantro leaf leaf 6 days6 days after after inoculation inoculation

and vigorous washing and vigorous washing

Courtesy: Courtesy: Maria Maria BrandlBrandl, USDA/ARS, USDA/ARS

Interactions between Food‐Borne Pathogens and Protozoa Isolated from Lettuce and Spinach. Gourabathini et al. 2008. AEM p 2518–2525

Protozoa‐Glaucoma sp.

Vesicles with Vesicles with GFPGFP‐‐labledlabled EcO157:H7 EcO157:H7

Enhanced Survival of Salmonella enterica in Vesicles Released by aSoilborne Tetrahymena Species. Brandl et al. 2005. AEM p 1562–1569

Salmonella survival free‐floating or in vesiclesTetrahymena with Salmonella vesicles

I filt tiI filt tiInfiltration occurs:Infiltration occurs:

•• When outside water enters the produceWhen outside water enters the produce•• In produce with air spaces within cellular tissuesIn produce with air spaces within cellular tissues•• Temperature differential (water colder than produce) Temperature differential (water colder than produce)

••Causes air in cell space to contractCauses air in cell space to contract••Draw water in through pores, channels, bruisesDraw water in through pores, channels, bruises

Photo courtesy: M.J. Mahovic, UF/IFAS

Fruit pulp should be 10Fruit pulp should be 10ooF (6F (6ooC) cooler C) cooler than water than water temperature temperature to to prevent infiltration.prevent infiltration.

Microbes in water

ApplesApplesMelonsMelonsPeppersPeppersSpinachSpinachMangoMangoCitrusCitrus

TempTempPressurePressureTimeTimeDepthDepthWater deficitWater deficitVacuumVacuum

Adequate water sanitationAdequate water sanitationwill minimize problems will minimize problems

PrePre--Cooling Operations:Cooling Operations: HydroVacHydroVac™™ HydroVacHydroVac Ice InjectionIce Injection HydroHydro--CoolingCooling

Wash and Dip TanksWash and Dip Tanks Flume Wash SystemsFlume Wash Systems Spray Wash SystemsSpray Wash Systems IceIce--makingmaking Cooling CanalsCooling Canals


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ExamplesExamples Brush bedBrush bed “Jacuzzi” bath“Jacuzzi” bathUltrasonic bathUltrasonic bathCOCO22 cavitationcavitation

ExamplesExamples Disinfection treatment of postharvest water

Potential Transfer of Salmonella during Postharvest Handling

Disinfection treatment of postharvest water maintains cleanliness of brushes and rollers

Pao et al. 2009 Journal of Food Protection722: 2448–2452

Water and Immersion only

Water and Brush‐bedWater and Brush bed

ClO2 and Immersion only

ClO2 and Brush‐bed

What is the origin of microWhat is the origin of micro‐‐loadingloading to dump to dump tanks when bin dumping occurs in packing tanks when bin dumping occurs in packing houseshouses


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Fruit Fruit –– averageaverage log CFU/fruit (25 fruit/log CFU/fruit (25 fruit/samplesample))

Sample Location Code

PCA ECC-TC ECC-E. coli(presumptive)

Roma-type incoming

6.25 5.11 < 1.0

Mature Green Incoming

7.16 6.16 4.15

Maintain consistent sanitizer levels in dump tanks and Maintain consistent sanitizer levels in dump tanks and h hspray washersspray washers

Regularly check automated sanitizer equipment during Regularly check automated sanitizer equipment during daily packingdaily packing

Double check automated equipment with manual Double check automated equipment with manual methodsmethods

•• Multiple chemical choicesMultiple chemical choicesu t p e c e ca c o cesu t p e c e ca c o ces•• Multiple product typesMultiple product types•• Diverse microbe typesDiverse microbe types•• Different load throughputDifferent load throughput••Varying wash/cooling conditionsVarying wash/cooling conditions•• Different equipment designsDifferent equipment designs•• Different retention timesDifferent retention times

TPC Total Coliform E. coli

Unwashed T0 5.79 4.67 1.01Unwashed T3 5.70 3.27 2.07Washed T0 3.83 2.04 0.35Washed T3 3.27 0.88 0.35

N = 25N = 25

Log CFU/fruitLog CFU/fruitStart‐up + 3h

Non ChemicalNon Chemicall ll lUltra VioletUltra Violet

UltraUltra‐‐FiltrationFiltrationChemicalChemicalOxidizerOxidizerOxidizer and AcidOxidizer and AcidNonNon‐‐OxidizerOxidizer


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Flume Flume FlocculantFlocculant

SelfSelf‐‐purging filtrationpurging filtration

ChlorinationChlorinationHypochlorousHypochlorousAcid (Acid (HOClHOCl) + ROS) + ROSHypochlorousHypochlorousAcid (Acid (HOClHOCl) + ROS) + ROSChlorine GasChlorine GasSodium HypochloriteSodium HypochloriteCalcium HypochloriteCalcium Hypochlorite

Chlorine Dioxide Chlorine Dioxide ChlorobrominationChlorobrominationPeroxyaceticPeroxyacetic Acid or Hydrogen PeroxideAcid or Hydrogen PeroxideOzoneOzoneCopper ions + low Copper ions + low HOClHOCl (+ Silver ions)(+ Silver ions)

Sodium Hypochlorite (liquid) Sodium Hypochlorite (liquid) •• Most widely used methodMost widely used method•• Relatively inexpensiveRelatively inexpensive•• Readily available and flexibleReadily available and flexible•• Easy to adopt for smallEasy to adopt for small‐‐scalescale•• Broad spectrum of activity (yeasts, molds, bacteria, Broad spectrum of activity (yeasts, molds, bacteria, algae, many viruses)algae, many viruses)

•• Less effective for parasite cysts, some fungal spores Less effective for parasite cysts, some fungal spores

Combined ChlorineTotal Chlorine

Free Chlorine

pH HOCl ‐OCl6.5 95% 5%7.0 80% 20%7.5 50% 50%8.0 20% 80%


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70

80

90

100

e Fo

rm OC (32F)20C (68F)

0

10

20

30

40

50

60

5 6 7 8 9 10

Solution pH

% F

ree

Chl

orin

e 30C (86F)

4

HOClHighly active

OCl‐less active

Potential for toxic chlorine gas formationPotential for toxic chlorine gas formation Potential for toxic chlorine gas formationPotential for toxic chlorine gas formation Poor penetration of Poor penetration of biofilmsbiofilms and scaleand scale CorrosiveCorrosive Irritation (eye, respiratory, mucus membrane)Irritation (eye, respiratory, mucus membrane) Unstable (pH < 4, high temp), short halfUnstable (pH < 4, high temp), short half--lifelife Formation of potentially toxic byFormation of potentially toxic by--products products (THM’s, chloramines)(THM’s, chloramines)

Potential for sodium injury (ex. some apples)Potential for sodium injury (ex. some apples)

68% Ca(OCl)2tablets


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6060

8080

100100

120120

Effect of EOW on Penicillium digitatum conidia in water

% Kill % Kill

00

2020

4040

00 3030 6060 9090 120120 240240

215 215 ppmppm HOClHOClpH pH –– 4.84.8

Adapted from Adapted from WhangchaiWhangchai et al 2009et al 2009ActaActa Hort. 837 ISHS 211Hort. 837 ISHS 211‐‐215215

Time (Time (SecsSecs))

% of fruit

Storage Time (Days)@ 5C (40F)

Dec

ay In

cide

nce (%

Adapted from Adapted from WhangchaiWhangchai et al 2009et al 2009ActaActa Hort. 837 ISHS 211Hort. 837 ISHS 211‐‐215215

Tangerine

••Oxidizer 2.5x “more effective” than chlorineOxidizer 2.5x “more effective” than chlorine•• Low Sodium, Low ChloriteLow Sodium, Low Chlorite•• Does not form byDoes not form by‐‐products THMs /DBP’sproducts THMs /DBP’s•• Does not form chloraminesDoes not form chloramines•• Effective at wide pH rangesEffective at wide pH ranges••Good Good bioflimbioflim penetrationpenetration

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 entericaand Erwinia carotovora during Fruit Washing

PAO et al JFP 2007 p 629 634PAO et al. JFP 2007 p 629‐634

0 ppm5 ppm10 ppm20 ppm

Dose RangeInoculum in Water

Using Aqueous Chlorine Dioxide To Prevent Contamination of Tomatoes with Salmonella enterica and Erwinia carotovora during Fruit Washing PAO et al. JFP 2007 p 629‐634

20 ppmWet Inoculum

Dry Inoculum

Time ; 0‐60 sec


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Chlorine dioxide system:On-site chemical generator

• Two-chemical • less expensive

• Three chemical• more efficient conversion

Washing Conditions Sample Type Trihalomethane DBP (μg/L)

Municipal Water Process‐Cooling Water


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Less impacted by organic matter and soilLess impacted by organic matter and soilL f iL f i Low foamingLow foaming

Very good Very good biofilmbiofilm penetrationpenetrationVery good on molds and spores Very good on molds and spores

Oxidizer and Metabolic PoisonOxidizer and Metabolic PoisonNo residue or DBP’s No residue or DBP’s Breaks down to water, oxygen and acetic acid)Breaks down to water, oxygen and acetic acid)Generally nonGenerally non‐‐corrosivecorrosive

Corrosive to soft metals and skinCorrosive to soft metals and skinS d f d dil f S d f d dil f Strong, pungent odor of concentrate and dilute forms Strong, pungent odor of concentrate and dilute forms

(worker discomfort & safety)(worker discomfort & safety)Varied activity against fungiVaried activity against fungi Build up of acetic acid in water; translucency Build up of acetic acid in water; translucency Need to monitor water turnNeed to monitor water turn‐‐over closelyover closely Prolonged exposure may cause product damageProlonged exposure may cause product damage

0 15 150 300 3000 0 15 150 300 3000

Flume Line Shed A

Flume Line Shed B

Quality Turbidity (FAU)

3060 333

Conductivity 1558 mS 721 mS

pH 7.2 6.4

Free Cl 55 12

ORP 420 825

Total fecal coliform

log 5.4 CFU/100ml

< 0.9 log CFU/100ml

••Spot CheckingSpot Checking••Chemical Test KitChemical Test Kit••Chemical Test KitChemical Test Kit••Chemical Test StripsChemical Test Strips••ColorimeterColorimeter•• Direct Measurement MeterDirect Measurement Meter

•• Portable ORP and pH MeterPortable ORP and pH Meter•• Fixed Continuous MeterFixed Continuous Meter

••ORP and pH MeterORP and pH Meter•• Direct Ion SensorDirect Ion Sensor


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Fast Spot Checking Fast Spot Checking

Simple “Dip & Read” 1 Step

Colorimetric Analysis

Visual Reading

Low CostIS THIS FLUME WATER IN IS THIS FLUME WATER IN GOOD SHAPE GOOD SHAPE ??

Oxidation Reduction Potential ( mV)Oxidation Reduction Potential ( mV) Predicts Disinfection PotentialPredicts Disinfection Potential Measures Disinfection Potential Measures Disinfection Potential NOTNOT ppmppm Single Value Assessment of DisinfectionSingle Value Assessment of Disinfectiongg

pH ORP (mV)

Water Quality Measurements

Time Temp (tank) Temp (bag) pH ORP pH ORP EC Turbidity Free Cl- TSS

Water Source °C °C mv mv ms FAU mg/LDump (Time 0) 12:35pm 25.6 25.0 6.8 795 6.5 755 0.92 79 4.6Dump (Time 2h) 2:40pm 29.3 30.1 6.8 795 6.5 804 1.17 131 8Flume (Time 0) 12:40pm 36.0 34.4 6.8 780 6.9 811 0.68 15 21Flume (Time 2h) 2:45pm 36.5 36.1 6.6 821 6.6 843 0.85 19 37

Time of Sampling Following Day

ORP 795ORP 795‐‐821 mV; pH 6.6821 mV; pH 6.6‐‐6.86.8

TPC Total Coliform

E.coli

Dump T0 2.98 -0.05 -0.05Dump T2 2.95 -0.05 -0.05Flume T0 2.95 -0.05 -0.05Flume T2 4.02 -0.05 -0.05N = 6; n = 12N = 6; n = 12

Log CFU/100ml

Water Quality Measurements

Time Temp (tank) Temp (bag) pH ORP pH ORP EC Turbidity Free Cl- TSS

Water Source °C °C mv mv ms FAU mg/LDump (Time 0) 4:00pm 37.5 32.0 8.8 655 8.9 668 3.47 19 194Dump (Time 2h) 5:00pm 36.4 34.9 8.5 667 8.8 682 3.30 46 112Flume (Time 0) 4:15pm - 36.3 8.7 650 - - - - - -Flume (Time 2h) 5:10pm - - - 663 - - - - - -

Time of Sampling Following Day

ORP 650ORP 650‐‐667 mV; pH 8.8667 mV; pH 8.8

TPC Total Coliform

E.coli

Dump T0 3.30 -0.05 -0.05Dump T2 5.31 -0.05 -0.05Flume T0 3.95 -0.05 -0.05Flume T2 5.85 -0.05 -0.05N = 6; n = 12N = 6; n = 12

Log CFU/100ml

Rate of diffusion of Rate of diffusion of free chlorine free chlorine through the through the membrane depends on temperaturemembrane depends on temperature sensor response must be corrected for changes in sensor response must be corrected for changes in membrane permeabilitymembrane permeabilityp yp y TemperatureTemperature‐‐compensated sensorscompensated sensors

pH compensated sensorspH compensated sensors



99.99999192006.9200 ppm Cl

99.9207422019.8200 ppm Cl

99.9909001007.1100 ppm Cl

550.96981008.2100 ppm Cl

% Spore Kill 5 min

% Spore Kill 15 secs

ORP (mV)Free ClpH Treatment

Comparative Oxidative Disinfection Potential: Comparative Oxidative Disinfection Potential: Penicillium expansumPenicillium expansum

0.10.13722.27.5MWS

99.99999192006.9200 ppm Cl

NaOCl (bleach) pH endpoint Measured Free Chlorine(ppm)

ORP value(mV)

Approx 6-log Inactivation Time

(low burden water)E. coli Fecal

ColiformMunicipal Water

Sourceunadjusted

8.3 0.2 365 > 1h >1h

Municipal Water Source

adjusted

7.0 0.2 595 > 30min >1h

MWS +100ppmunadjusted

9.8 100 656 < 15s



C. Product Water ManagementQ# Requirement Procedure Verification Corrective Action/

Disposition2.15 Re-circulated

and re-used water is changed at least daily, and records of changes are

Operation shall maintain records to demonstrate water changes. Water may be used for longer than daily if a validated

Auditor reviews records to verify at least daily changes of all wash water.

Procedure is developed or revised. Retraining is performed.

POSTHARVEST AUDIT METRICS

gkept. regeneration

system (e.g., a water pasteurization/filtration system) is being used.

2.16 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

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.

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.

2.18 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

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

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.

when the chlorine dioxide drops below the target ppm, and shall maintain records to verify proper management of levels.

disposition. compliance. The The potential risks of potential risks of waterborne contamination waterborne contamination

demand special attention for Quality and Safetydemand special attention for Quality and Safety

Select disinfectant on microbial reduction objectivesSelect disinfectant on microbial reduction objectives

Weigh the pros and cons of each sanitizer to find the Weigh the pros and cons of each sanitizer to find the one that’s right for your operationone 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

pp 5 g /g5.25% 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

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