handbook of food safety engineering

Handbook of Food Safety Engineering

Edited by

Da-Wen Sun

A John Wiley & Sons, Ltd., Publication

This edition first published 2012 © 2012 by Blackwell Publishing Ltd

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Library of Congress Cataloging-in-Publication Data

Handbook of food safety engineering / edited by Da-Wen Sun. p. cm. Includes bibliographical references and index. ISBN-13: 978-1-4443-3334-3 (hardback) ISBN-10: 1-4443-3334-8 (hardback) 1. Food–Safety measures. 2. Food–Microbiology. 3. Food industry and trade–Sanitation. I. Sun, Da-Wen. TX546.H36 2011 363.19'26–dc23 2011019196

A catalogue record for this book is available from the British Library.

This book is published in the following electronic formats: ePDF 9781444355291; Wiley Online Library 9781444355321; ePub 9781444355307; Mobi 9781444355314

Set in 10/12 pt Times by Toppan Best-set Premedia LimitedPrinted in Singapore

1 2012

Contents

List of Contributors xviiAbout the Editor xxiiPreface xxiv

PART ONE: FUNDAMENTALS 1

1 Introduction to Food Microbiology 3MartinAdams

1.1 Introduction 31.2 Microorganismsandfoods 41.3 Foodborneillness 51.4 Foodspoilage 81.5 Foodfermentation 91.6 Microbialphysiologyandfoodpreservation 101.7 Microbiologicalanalysis 121.8 Foodsafetymanagementsystems 141.9 Conclusions 16

2 Overview of Foodborne Pathogens 18AmaliaG.M.Scannell

2.1 Introduction 182.2 Bacterialpathogens 20

2.2.1 Salmonellaspecies 202.2.2 Campylobacterspecies 222.2.3 Shigellaspecies 242.2.4 EnterovirulentEscherichia coli 252.2.5 Yersiniaspecies 282.2.6 Vibriospecies 292.2.7 AeromonasandPlesiomonasspecies:putative

Gram-negativepathogens 302.2.8 Listeria monocytogenes 322.2.9 Staphylococcus aureus 332.2.10 Clostridiumspecies 332.2.11 Bacillusspecies 36

iv Contents

2.3 Foodborneviruses 372.3.1 Norovirus 372.3.2 HepatitisA 39

2.4 Foodborneparasites 392.4.1 Cryptosporidium parvum 392.4.2 Giardia intestinalis 42

2.5 Conclusions 42

3 Chemical Safety of Foods 57SteveL.TaylorandJosephL.Baumert

3.1 Introduction 573.2 Natureofchemicalhazardsinfoods 57

3.2.1 Naturallyoccurringtoxicantsinfoods 583.2.2 Potentiallytoxicmanmadechemicalsinfoods 65

3.3 Foodsafetyengineeringandcontrolofchemicalhazards 713.3.1 Monitoringandcontrolofrawmaterials 713.3.2 Storageandtransportationofingredientsandfoodproducts 723.3.3 Removalorcontrolofchemicalhazardsbyprocessing 72

3.4 Foodallergencontrol 723.4.1 Purchasingstrategies 733.4.2 Receiving 733.4.3 Operations/manufacturing 733.4.4 Rework 743.4.5 Sanitation 743.4.6 Allergenauditing 753.4.7 Packagingstrategies 75

3.5 Conclusions 76

4 Intrinsic and Extrinsic Parameters for Microbial Growth and Heat Inactivation 79VijayK.Juneja,LihanHuangand XiangheYan

4.1 Introduction 794.2 Factorsaffectingmicrobialgrowth 80

4.2.1 Intrinsicfactors 804.2.2 Extrinsicfactors 85

4.3 Factorsaffectingheatresistance 884.4 Combiningtraditionalpreservationtechniques 894.5 Conclusions 90

5 Kinetics of Microbial Inactivation 92OsmanErkmenandAykutÖ.Barazi

5.1 Introduction 925.2 Microbialinactivationkineticsbasedonfoodprocessingmethods 92

5.2.1 Thermalinactivationkinetics 935.2.2 Inactivationbypressure 995.2.3 Inactivationbypulsedelectricfield 100

Contents v

5.2.4 Microwaveandradiofrequencyprocessing 1015.2.5 Ohmicandinductiveheating 102

5.3 Kineticparametersfortheinactivationofpathogens 1025.3.1 Salmonella 1025.3.2 Listeria monocytogenes 1035.3.3 Staphylococcus aureus 1035.3.4 Escherichia coli 1045.3.5 Bacillus cereus 1045.3.6 Clostridium 1045.3.7 Vibrio 1045.3.8 Otherpathogens 105

5.4 Conclusions 105

6 Predictive Microbial Modelling 108UrsulaAndreaGonzales-Barron

6.1 Introduction 1086.2 Classificationofmodels 108

6.2.1 Kineticandprobabilitymodels 1096.2.2 Empiricalandmechanisticmodels 1106.2.3 Primary,secondaryandtertiarymodels 1126.2.4 Deterministicandstochasticmodels 115

6.3 Descriptionofmainmodels 1176.3.1 Modellinggrowthcurves 1176.3.2 Modellinginactivation/survivalcurves 1226.3.3 Secondarymodels 1276.3.4 Probabilitymodels 133

6.4 Applicationsofpredictivemicrobialmodelling 1366.4.1 Hazardanalysiscriticalcontrolpoint(HACCP)and

quantitativeriskassessment(QRA) 1366.4.2 Microbialshelf-lifestudies 1366.4.3 Temperaturefunctionintegrationandtemperature

monitors 1376.4.4 Productresearchanddevelopment 1376.4.5 Designofexperiments 137

6.5 Predictivemicrobialmodellingandquantitativeriskassessment 1386.6 Conclusions 140

7 Integration of Food Process Engineering and Food Microbial Growth 153LijunWang

7.1 Introduction 1537.2 Inactivationofmicrobialgrowth 154

7.2.1 Inactivationofmicrobialgrowthbythermalfoodprocessing 154

7.2.2 Inactivationofmicrobialgrowthbyfoodrefrigeration 1557.2.3 Inactivationofmicrobialgrowthbynonthermalfood

processing 156

vi Contents

7.3 Process-dependentmicrobialmodeling 1607.3.1 Predictivemicrobialkineticmodels 1607.3.2 Temperature-dependentmicrobialgrowthkineticmodels 1617.3.3 Irradiation-dependentmicrobialgrowthmodel 1627.3.4 Pulsedelectricfield-dependentmicrobialgrowthmodel 1637.3.5 High-pressure-dependentmicrobialgrowthmodel 164

7.4 Processmodeling 1657.5 Integrationofprocessandmicrobialgrowthkineticmodels 1697.6 Conclusions 170

PART TWO: ADVANCED FOOD SAFETY DETECTION METHODS 177

8 Rapid Methods and Automation in Microbiology: 30 Years of Trends and Predictions 179DanielY.C.Fung

8.1 Introduction 1798.2 Samplepreparation 1798.3 Microorganismdetection 180

8.3.1 Viablecellcounttest 1808.3.2 Antigenandantibodytest 1838.3.3 Immuno-magneticseparationtest 1838.3.4 DNA-basedtest 1848.3.5 Biosensortest 185

8.4 Futuredevelopments 1858.5 Conclusions 185

9 Phage-based Detection of Foodborne Pathogens 190UditMinocha,MindyShroyer,PatriciaRomeroandBruceM.Applegate

9.1 Introduction 1909.2 Fundamentalsofbacteriophage 192

9.2.1 Historyofbacteriophages 1929.2.2 Classification 1939.2.3 Phagelifecycle 1959.2.4 Environmentalpresenceandpotentialimpactofphage 197

9.3 Phage-baseddetectionofpathogens 1979.3.1 Phageattachment 1989.3.2 Genomeexpression 1999.3.3 Celllysis 2029.3.4 Progenydetection 203

9.4 Bacteriophage-mediatedbiocontrol 2059.4.1 Considerationsofphagebiocontrolstrategy–advantages

anddisadvantages 2069.4.2 Biocontrolandbioprocessing:applicationofphage

therapytoindustry 2079.4.3 Phageasantimicrobialagents 208

Contents vii

9.4.4 Preharvestcontrol–foodsofplantoriginandfoodsofanimalorigin 209

9.4.5 Postharvestcontrol–foodsofplantoriginandfoodsofanimalorigin 209

9.5 Conclusions 210

10 Real-time PCR 217AlanG.Mathew

10.1 Introduction 21710.2 Real-timePCRtheoryandtechnologies 218

10.2.1 Real-timePCRtheory 21810.3 Real-timePCRsystems 23110.4 Real-timePCRapplicationsforfoodsafety 232

10.4.1 Real-timePCRapplicationsforfoodborneviruses 23310.4.2 Real-timePCRapplicationsforfoodbornebacteria 24610.4.3 Real-timePCRapplicationsforfoodborneyeastsandfungi 24810.4.4 Real-timePCRapplicationsforfoodborneparasitedetection 24910.4.5 Real-timePCRapplicationsforfoodauthentication 250

10.5 Conclusions 252

11 DNA Array 258MagdalenaGabig-Ciminska,JoannaJakóbkiewicz-BaneckaandGrzegorzWegrzyn

11.1 Introduction 25811.2 History–fromdoublehelixviablottoDNAarray 25911.3 Principle 26011.4 DNAarraystructureandoperatingrules 261

11.4.1 Arrayfabricationtechnology 26111.4.2 DNAarrayconcept 26211.4.3 Bird’seyeviewofDNAarraytechnology–todayand

tomorrow 27211.5 ApplicationsandpotentialuseoftheDNAarrays 27311.6 Conclusions 274

12 Immunoassay 279DavidL.BrandonandJ.MarkCarter

12.1 Introduction 27912.1.1 Usesofimmunoassayinfoodsafety 27912.1.2 Matrices 280

12.2 Strategicconsiderations 28112.2.1 Sampling 28112.2.2 Analyticalcriteria 28212.2.3 Antibodies 284

12.3 Immunoassayformats 28812.3.1 Generalconsiderations 28812.3.2 Cellularassays 290

viii Contents

12.3.3 ELISA 29012.3.4 Lateralflowassays(LFA)andrelatedformats 29012.3.5 Immunosensorsystemsandarrays 29212.3.6 Fluorescencepolarization 29512.3.7 Agglutinationassays 29612.3.8 Electrochemiluminescence 296

12.4 Combinedmethodologies 29712.4.1 Immunoblotting 29712.4.2 Immunomagneticbeadsandotherimmunocapture

separations 29812.4.3 Immunoaffinitycolumns 29812.4.4 Flowinjectionanalysis 29912.4.5 Immuno-PCRmethods 299

12.5 Selectedexamplesofimmunoassayappliedtofoodsafety 29912.5.1 Proteins 29912.5.2 Lowmolecularweightcompounds 30112.5.3 Bacterialpathogens 303

12.6 Troubleshootingandvalidation 30412.6.1 Troubleshooting 30412.6.2 Validation 304

12.7 Futuredevelopments 30512.7.1 Multiplexingandimprovedautomation 30512.7.2 Newlabels,molecules,andanalyticalchallenges 306


13 Biosensors 313FrancisJ.MulaaandPetraM.Krämer

13.1 Introduction 31313.2 Biosensorsforfoodcontrolandsafety 314

13.2.1 Typesofbiologicalrecognitionelements 31513.2.2 Immobilizationtechniques 32413.2.3 Typesoftransducers 32813.2.4 Labelingtechniques 33213.2.5 Biosensorapplicationsinmonitoringfoodcomponents 33513.2.6 Commerciallyavailableandprototypebiosensorsforfood

analysisandsafety 34213.3 Conclusions 342

PART THREE: CONVENTIONAL PROCESSING SYSTEMS OF PRODUCING SAFE FOODS 353

14 Pasteurization and Sterilization 355TatianaKoutchma

14.1 Introduction 35514.2 Sterilization 35614.3 Pasteurization 356

14.3.1 Acidandacidifiedfoods 35714.3.2 Low-acidpasteurizedproducts 357

Contents ix

14.3.3 Microbialreductiontechniques 36014.3.4 Establishmentofpreservationprocess 36414.3.5 Regulatorystatusofnovelsterilizationandpasteurization 36614.3.6 Futuretrends 368


15 Microwave Processing 371ShaojinWang

15.1 Introduction 37115.2 Mechanismofmicrowaveheating 37215.3 Microwaverelateddielectricproperties 373

15.3.1 Frequencyeffects 37515.3.2 Temperatureeffects 37515.3.3 Compositioneffects 377

15.4 Computersimulationstoimprovemicrowaveheatinguniformity 38015.4.1 Simulationmethods 38015.4.2 Validationmethods 38015.4.3 Applicationsofcomputersimulationinfoodprocessing 381

15.5 Practicalandcommercialmicrowaveprocessing 38215.5.1 Microwavedryingandcombinationtreatments 38215.5.2 Thawing-tempering 38315.5.3 Microwavepasteurizationandsterilization 384


16 Drying of Foods 394NaphapornChiewchan,SakamonDevahastinandArunS.Mujumdar

16.1 Introduction 39416.2 Occurrenceofmycotoxinsandpathogenicbacteriaindried

foodproducts 39516.2.1 Contaminationofmycotoxins 39516.2.2 Importantmycotoxinsindriedfoods 39516.2.3 Contaminationbypathogenicbacteria 398

16.3 Controlofmycotoxinsandpathogenicbacteriaindriedfoodproducts 40016.3.1 Decontaminationviadrying 40016.3.2 Reductionofinitialcontaminationviapretreatments 402


17 Frying of Foods 412SerpilSahinandIsilBarutcu

17.1 Introduction 41217.2 Oilabsorption 413

17.2.1 Mechanismofoilabsorption 41317.2.2 Parametersaffectingoilabsorption 414

17.3 Changesinoilduringfrying 41817.3.1 Volatiledecompositionproducts 41917.3.2 Nonvolatiledecompositionproducts 42217.3.3 Regenerationofoilsusedfordeepfrying 424

x Contents

17.4 Formationoftoxicsubstancesinfriedfoodduringfrying 42717.4.1 Heterocyclicamines(HCAs) 42717.4.2 N-Nitrosocompounds 43017.4.3 Acrylamide 430


18 Food Refrigeration 444AdrianaE.DelgadoandDa-WenSun

18.1 Introduction 44418.2 Foodmicrobiologyandrefrigeration 445

18.2.1 Wateractivity 44618.2.2 Predictivemicrobiology 44918.2.3 Refrigerationmethods–qualityandsafetyaspects 452

18.3 Refrigeratedpreparedmeals 45518.4 Refrigeratedstorageandsafety 45718.5 Activeandintelligentpackaging 46118.6 Conclusions 463

19 Sous Vide and Cook-chill Processing 468RonanGormleyandFergalTansey

19.1 Introduction 46819.2 Sous videprocessing 469

19.2.1 Introduction 46919.2.2 Elementsofsous videtechnology 46919.2.3 Advantages/disadvantagesofsous videprocessing 46919.2.4 Stepsinsous videprocessing 46919.2.5 Thermaltreatment 47019.2.6 Safetyofsous videfoods 47119.2.7 Sensory,nutrientretentionandqualityofsous videfoods 47419.2.8 Casestudiesonsous videprocessingofvegetables,

musclefoods,carbohydratefoods,andfruitpurees 47519.3 Cook-chillprocessing(non-sous vide) 482

19.3.1 Introduction 48219.3.2 Elementsofcook-chilltechnology 48219.3.3 Advantages/disadvantagesofcook-chillprocessing 48219.3.4 Stepsincook-chillprocessing 48319.3.5 Packagingofcook-chillfoods 48619.3.6 Thermaltreatmentofcook-chillfoods 48619.3.7 Safetyofcook-chillfoods 48619.3.8 Sensory,nutritionalandqualityaspectsofcook-chillfoods 48719.3.9 Airlinecatering 48719.3.10 Freeze-chilledready-meals 488

19.4 High-qualityshelf-life,distributionandretailing 48819.4.1 Hurdletechnology 48819.4.2 Thechillchain 489


Contents xi

20 Irradiation 497MoniqueLacroix

20.1 Introduction 49720.2 Definitionofirradiation 49820.3 Gammairradiation 499

20.3.1 Gammairradiationforthetreatmentoffreshfruitsandvegetables 499

20.3.2 Gammairradiationforthetreatmentofcheese 50120.3.3 Gammairradiationforthetreatmentoffish,meatand

poultry 50120.4 UV-Cirradiation 502

20.4.1 UV-Cirradiationforthetreatmentoffreshfruitsandvegetables 502

20.4.2 UV-Cforthetreatmentofliquideggproducts 50320.4.3 UV-Cirradiationforthetreatmentoffishandmeat 503

20.5 Combinedtreatments 50420.5.1 Combinedtreatmentswithgammarays 50420.5.2 CombinedtreatmentswithUV-C 514


21 Aseptic Processing and Packaging 524JuliusAshirifie-GogofioandJohnD.Floros

21.1 Introduction 52421.2 Abriefhistoryofasepticprocessinginthefoodindustry 52521.3 Basicprinciplesandapplications 525

21.3.1 Continuousheatingandcoolinginasepticprocessing 52521.3.2 Fluidflow 52521.3.3 Microbialinactivation,chemicalkineticsandheatexchange 526

21.4 Asepticpackagingapplications 52721.5 Asepticpackagingsystems 53121.6 Asepticbulkstorage 53221.7 Selectionofanasepticpackagingsystem 53321.8 Asepticprocessingoperation:establishment,validation

andregulations 53421.9 Safetyofasepticallyprocessedfoods 53521.10 Advantagesofasepticallyprocessedfoods 53621.11 Futuretrendsforasepticprocessingandpackaging 53821.12 Conclusions 539

22 Modified Atmosphere Packaging 543FranciscoArtés,PerlaA.Gómez,EncarnaAguayoandFranciscoArtés-Hernández

22.1 Introduction 54322.2 Atmospheremodification 54422.3 Effectsoftheatmospheremodification 54722.4 Potentialbenefits 547

xii Contents

22.5 Potentialdisadvantages 55022.5.1 Physicalchanges 55022.5.2 Physiologicalandbiochemicalchanges 550

22.6 TolerancetoO2andCO2 55122.7 Nonconventionalatmospheres 55222.8 Maprecommendations 55322.9 Packagedesign 55622.10 Modelling 55722.11 Typesoffilms 55922.12 Activeandintelligentpackaging 560

22.12.1 ActivepackagingforcontrollingO2 56122.12.2 ActivepackagesforcontrollingCO2 56122.12.3 ActivepackagesforcontrollingC2H4 56122.12.4 Activepackagesforcontrollingrelativehumidity 56222.12.5 Antimicrobialactivepackaging 562


PART FOUR: NOVEL PROCESSING METHODS FOR FOOD MICROBIAL INACTIVATION 575

23 High Pressure Processing 577MontserratMor-MurandJordiSaldo

23.1 Introduction 57723.2 BasicsonHPPequipmentdesign 57823.3 Modelingoftheeffectofhighpressuretreatments 580

23.3.1 Indicatorsformonitoringhighpressuretreatments 58423.4 Modeofactionofhighpressureonspoilingandpathogenicagents 585

23.4.1 Factorsaffectingpressuresensitivity 58823.4.2 Useofpressurecycles 59023.4.3 HPPdamagerepair 591

23.5 Pressureassistedthermalsterilization(PATS) 59223.6 Packagingmaterials 59423.7 Commercialandeconomicalaspects 59523.8 Futureperspectivesandpromisingapplications 59623.9 Conclusions 597

24 Pulsed Electric Field Processing 603OlgaMartín-Belloso,AngelSobrino-LópezandPedroElez-Martínez

24.1 Introduction 60324.2 Microbialinactivation 603

24.2.1 PEFinactivationmechanism 60324.2.2 Influenceoftreatmentvariables 60624.2.3 PEFincombinationwithotherpreservationmethods 61124.2.4 ModelingPEFinactivation 613

24.3 Qualityandshelf-lifeofPEF-treatedfoods 616

Contents xiii

24.4 ManagementofPEFprocessing 61824.4.1 Treatmentchamber 61824.4.2 Energyconsumptionapproach 619


25 Radio Frequency Technology 627ValérieOrsatand RameshMurugesan

25.1 Introduction 62725.2 Radiofrequencyheatingtechnology 628

25.2.1 Dielectricmaterialproperties 62825.2.2 HeatingmechanismofRF 630

25.3 RFtreatments 63125.3.1 Microbialinactivationinmeatprocessing 63125.3.2 Radiofrequencypasteurizationofvariousfoods 63225.3.3 RFcooking 63425.3.4 Radiofrequencypestcontrolinfreshfruits 635

25.4 RoleofRFIDinfoodproducttraceability 63625.4.1 RFIDprinciple 63625.4.2 RFID–foodproducttraceability 638


26 Pulsed Light Technology 643VicenteM.Gómez-López

26.1 Introduction 64326.2 TypesofUVlamps 64426.3 Characterizingpulsedlighttreatments 64426.4 Pulsedlightsystems 64626.5 Microbialinactivationmechanismsandrelatedtopics 650

26.5.1 Photochemicaleffect 65126.5.2 Photophysicaleffect 65226.5.3 Photothermaleffect 65226.5.4 Sublethalinjury 65426.5.5 Acquiredresistance 65426.5.6 ReparationofdamagetoDNA 654

26.6 Inactivationkinetics 65526.7 Technologicalchallengestodeliverappropriateillumination 65726.8 Microbial-relatedfactorsaffectingPLefficacy 65926.9 Inactivationofpathogenicmicroorganismsandtoxins 660

26.9.1 Inactivationofviruses 66026.9.2 Inactivationofbacteria 66026.9.3 Inactivationoffungi 66426.9.4 Inactivationofparasites 66426.9.5 Decompositionoftoxinsandallergens 665

26.10 Pulsedlightphotosensitization 66526.11 Conclusions 665

xiv Contents

27 Ohmic Heating Treatment 669AntónioA.Vicente,InêsdeCastro,JoséA.TeixeiraandLuísF.Machado

27.1 Introduction 66927.2 Ohmicheatingtheory 671

27.2.1 Basicprinciple 67127.2.2 Predictionofohmicheating 672

27.3 Ohmicheatingeffects 67327.3.1 Ohmicheatingeffectsonmicroorganisms 67327.3.2 Ohmicheatingeffectsonenzymes 675

27.4 Commercialapplications 67627.5 Conclusions 677

28 Ozone Processing 681KasiviswanathanMuthukumarappan

28.1 Introduction 68128.2 Ozoneanditsproduction 682

28.2.1 Definitionofozone 68228.2.2 Productionofozone 682

28.3 Microbialinactivationoffoodmaterials 68428.3.1 Applicationofozoneinsolidfoodmaterials 68528.3.2 Applicationofozoneinliquidfoodmaterials 68728.3.3 Effectsofozoneonproductquality 688

28.4 Safetyrequirements 68928.5 Conclusions 689

29 Intelligent Packaging 693I.brahimSaniÖzdemir

29.1 Introduction 69329.2 Intelligentpackagingsystems 694

29.2.1 Time-temperatureindicators(TTI) 69529.2.2 Sensors/indicators 69629.2.3 RFID 69829.2.4 OLED 69929.2.5 E-ink 701

29.3 Anti-counterfeitingapplications 70129.4 Legislation 70229.5 Conclusions 702

PART FIVE: FOOD SAFETY MANAGEMENT SYSTEMS 707

30 Introduction to Food Safety Management 709IoannisS.ArvanitoyannisandMariaSakkomitrou

30.1 Introduction 70930.2 GMPandGHPsystemsandtheirapplicationinfoodsafety 71030.3 HACCP 71330.4 BRCandIFS 723

Contents xv

30.5 ISO22000:2005 72630.6 Conclusions 730

31 Good Manufacturing Practice (GMP) 733ÓlafurSveinnOddgeirsson

31.1 Introduction 73331.2 Rightsandresponsibilities 734

31.2.1 Responsibilityofafoodbusinessoperator(FBO) 73431.2.2 RightsoftheFBO 73431.2.3 Responsibilityofanauditor 73431.2.4 Rightsofauditors 735

31.3 GMPandprerequisiteprogrammes 73531.3.1 Potablewatersupply 73631.3.2 Pestcontrol 73831.3.3 Cleaning 73931.3.4 Temperatureregimes 74231.3.5 Checksonoperationalhygiene 74331.3.6 Training 74431.3.7 Traceability 74431.3.8 Maintenance 745

31.4 Productionpremises 74531.4.1 Structureandlayout 74531.4.2 Installationsandequipment 74631.4.3 Maintenanceandcleanliness 75731.4.4 Operationalhygiene 75831.4.5 Transport 759

31.5 Checksonfinishedproducts 75931.6 Informationonaudits 759

31.6.1 Conductofstakeholders 76031.6.2 Typesofdeficienciesdetected 76031.6.3 Majorandminordeficiencies 76031.6.4 Summaryofanaudit 76031.6.5 Confirmationbymanagement 76031.6.6 Auditreport 76131.6.7 Conclusionsofanaudit(officialorcommercial) 761

31.7 Furtherinformation 76131.8 Conclusions 762

32 Sanitation Standard Operating Procedures 763FelixH.Barron,AngelaFraserandKennethHerring

32.1 Introduction 76332.2 PrincipleofSSOPs 764

32.2.1 SSOPsasrelatedtohazardanalysiscriticalcontrolpoints(HACCP) 764

32.2.2 Processflow 76432.2.3 Sourcesofmicrobialcontamination 76432.2.4 Controlofmicrobialcontamination 764

xvi Contents

32.3 ApplicationproceduresofSSOPs 76532.3.1 DevelopmentofSSOPs 76532.3.2 ImplementationofSSOPs 76532.3.3 MaintenanceofSSOPs 76532.3.4 Correctiveactions 76632.3.5 Recordkeeping 76632.3.6 EffectivenessofSSOPs 766

32.4 USASSOPsregulations 76632.4.1 USAregulationsformeatandpoultry 76632.4.2 Regulationsforfruitandvegetablejuices 76732.4.3 Regulationsforseafood 76832.4.4 Foodservicesanitationregulations 768


33 Hazard Analysis Critical Control Point (HACCP) System 772KerriB.Harris

33.1 Introduction 77233.2 HistoryofHACCPanditsprinciples 772

33.2.1 AdoptionofHACCP 77333.2.2 TheprinciplesofHACCP 77433.2.3 ThesevenHACCPprinciples 775

33.3 ImplementingHACCP 78233.4 Training 78233.5 Conclusions 784

34 ISO 22000 Food Safety 786PeterRasporandMatejaAmbrožič

34.1 Introduction 78634.2 Historyoffoodstandards 78734.3 Reviewofexistingstandardsrelatedtofood 78834.4 Conceptualprinciplesforstandarddevelopment 79034.5 ISO22000 792

34.5.1 Purpose 79234.5.2 Principles 793

34.6 ApplicationofISO22000inpractice 79834.6.1 FoodSafetyManagementSystem(FSMS) 79934.6.2 Managementresponsibility 80034.6.3 Resourcemanagement 80234.6.4 Planningandrealizationofsafeproducts 80434.6.5 Validation,verificationandimprovementofthefoodsafety

managementsystem 81034.7 Advantagesanddisadvantagesofstandardization 81134.8 Futureneeds 81234.9 Conclusions 813

Index 817

List of Contributors

Martin AdamsFaculty of Health and Medical SciencesUniversity of SurreyGuildford, UK

Encarna AguayoDepartment of Food EngineeringTechnical University of CartagenaCartagena, Murcia, Spain

Mateja AmbrožicDepartment of Food Science & TechnologyBiotechnical FacultyUniversity of LjubljanaLjubljana, Slovenia

Bruce M. ApplegateDepartments of Food Science and Biological SciencesPurdue UniversityWest Lafayette, IN, USA

Francisco ArtésDepartment of Food EngineeringTechnical University of CartagenaCartagena, Murcia, Spain

Francisco Artés-HernándezDepartment of Food EngineeringTechnical University of CartagenaCartagena, Murcia, Spain

Ioannis S. ArvanitoyannisDepartment of Ichthyology & Aquatic EnvironmentSchool of Agricultural SciencesUniversity of ThessalyMagnisia, Greece

Julius Ashirifie-GogofioDepartment of Food ScienceThe Pennsylvania State UniversityUniversity Park, PA, USA

Aykut Ö. BaraziDepartment of Food EngineeringUniversity of GaziantepGaziantep, Turkey

Felix H. BarronDepartment of Biological SciencesCollege of Agriculture, Forestry and Life SciencesClemson, SC, USA

Isil BarutcuFood Engineering DepartmentMiddle East Technical UniversityAnkara, Turkey

Joseph L. BaumertDepartment of Food Science & TechnologyUniversity of NebraskaLincoln, NE, USA

xviii List of Contributors

David L. BrandonWestern Regional Research CenterUSDA Agricultural Research ServiceAlbany, CA, USA

J. Mark CarterWestern Regional Research CenterUSDA Agricultural Research ServiceAlbany, CA, USA

Inês de CastroCastro, Pinto & Costa, Lda.Maia, Portugal

Naphaporn ChiewchanDepartment of Food EngineeringKing Mongkut’s University of Technology ThonburiBangkok, Thailand

Adriana E. DelgadoFood Refrigeration and Computerised Food TechnologyNational University of Ireland, Dublin (University College Dublin)Agriculture & Food Science CentreDublin, Ireland

Sakamon DevahastinDepartment of Food EngineeringKing Mongkut’s University of Technology ThonburiBangkok, Thailand

Pedro Elez-MartínezFood Technology DepartmentUniversitat de LleidaLleida, Spain

Osman ErkmenDepartment of Food EngineeringUniversity of GaziantepGaziantep, Turkey

John D. FlorosDepartment of Food ScienceThe Pennsylvania State UniversityUniversity Park, PA, USA

Angela FraserDepartment of Biological SciencesCollege of Agriculture, Forestry and Life SciencesClemson, SC, USA

Daniel Y.C. FungDepartment of Animal Sciences and IndustryKansas State UniversityManhattan, KS, USA

Magdalena Gabig-CiminskaLaboratory of Molecular BiologyInstitute of Biochemistry and BiophysicsPolish Academy of SciencesUniversity of GdanskGdansk, Poland

Perla A. GómezInstitute of Plant BiotechnologyTechnical University of CartagenaCartagena, Murcia, Spain

Vicente M. Gómez-LópezInstituto de Ciencia y Tecnología de AlimentosFacultad de Ciencias, Universidad Central de VenezuelaCaracas, Venezuela

Ursula Andrea Gonzales-BarronSchool of Agriculture, Food Science and Veterinary MedicineUniversity College DublinDublin, Ireland

Ronan GormleyAshtown Food Research CentreAshtown, Dublin, Ireland

Kerri B. HarrisInternational HACCP AllianceCenter for Food SafetyDepartment of Animal ScienceTexas A&M UniversityCollege Station, TX, USA

List of Contributors xix

Kenneth HerringDepartment of Biological SciencesCollege of Agriculture, Forestry and Life SciencesClemson, SC, USA

Lihan HuangEastern Regional Research CenterUSDA Agricultural Research ServiceWyndmoor, PA, USA

Joanna Jakóbkiewicz-BaneckaDepartment of Molecular BiologyUniversity of GdanskGdansk, Poland

Vijay K. JunejaEastern Regional Research CenterUSDA Agricultural Research ServiceWyndmoor, PA, USA

Tatiana KoutchmaFood Process EngineeringAgriculture and Agri-Food CanadaGuelph Food Research CenterGuelph, ON, Canada

Petra M. KrämerResearch Unit Microbe-Plant InteractionsHelmholtzZentrum München – German Research Center for Environmental HealthNeuherberg (Munich), Germany

Monique LacroixINRS-Institut Armand-FrappierQuebec, Canada

Luís F. MachadoInstitute for Biotechnology and BioengineeringCentre of Biological EngineeringUniversity of MinhoBraga, Portugal

Olga Martín-BellosoFood Technology DepartmentUniversity of LleidaLleida, Spain

Alan G. MathewDepartment of Animal SciencesPurdue UniversityWest Lafayette, IN, USA

Udit MinochaFood Science DepartmentPurdue UniversityWest Lafayette, IN, USA

Montserrat Mor-MurCER Planta Tecnologia dels alimentsFacultat de VeterinàriaUniversitat Autònoma de BarcelonaBellaterra, Barcelona, Spain

Arun S. MujumdarDepartment of Mechanical EngineeringNational University of SingaporeSingapore

Francis J. MulaaBiochemistry DepartmentUniversity of NairobiNairobi, Kenya

Ramesh MurugesanDepartment of Bioresource EngineeringMacdonald Campus of McGill UniversityQuebec, Canada

Kasiviswanathan MuthukumarappanAgricultural and Biosystems Engineering DepartmentSouth Dakota State UniversityBrookings, SD, USA

Ólafur Sveinn OddgeirssonFood Control Consultants LtdAbercorn SchoolNewton, Broxburn, Scotland

xx List of Contributors

Valérie OrsatDepartment of Bioresource EngineeringMacdonald Campus of McGill UniversityQuebec, Canada

Ibrahim Sani ÖzdemirTübitak Marmara Research Center, Food InstituteGebze Kocaeli, Turkey

Peter RasporDepartment of Food Science & TechnologyBiotechnical FacultyUniversity of LjubljanaLjubljana, Slovenia

Patricia RomeroFood Science DepartmentPurdue UniversityWest Lafayette, IN, USA

Serpil SahinFood Engineering DepartmentMiddle East Technical UniversityAnkara, Turkey

Maria SakkomitrouDepartment of Ichthyology & Aquatic EnvironmentSchool of Agricultural SciencesUniversity of ThessalyMagnisia, Greece

Jordi SaldoCER Planta Tecnologia dels alimentsFacultat de VeterinàriaUniversitat Autònoma de BarcelonaBellaterra, Barcelona, Spain

Amalia G.M. ScannellSchool of Agriculture, Food Science and Veterinary MedicineUniversity College DublinDublin, Ireland

Mindy ShroyerFood Science DepartmentPurdue UniversityWest Lafayette, IN, USA

Angel Sobrino-LópezFood Technology DepartmentUniversity of LleidaLleida, Spain

Da-Wen SunFood Refrigeration and Computerised Food TechnologyNational University of Ireland, Dublin (University College Dublin)Agriculture & Food Science CentreDublin, Ireland

Fergal TanseyNovaUCDUniversity College DublinBelfield, Dublin, Ireland

Steve L. TaylorDepartment of Food Science & TechnologyUniversity of NebraskaLincoln, NE, USA

José A. TeixeiraDepartment of Biological EngineeringUniversity of MinhoBraga, Portugal

Antonio A. VicenteDepartment of Biological EngineeringUniversity of MinhoBraga, Portugal

Lijun WangBiological EngineeringNorth Carolina A&T State UniversityGreensboro, NC, USA

List of Contributors xxi

Shaojin WangDepartment of Biological Systems EngineeringWashington State UniversityPullman, WA, USA

Grzegorz WegrzynDepartment of Molecular BiologyUniversity of GdanskGdansk, Poland

Xianghe YanEastern Regional Research CenterUSDA Agricultural Research ServiceWyndmoor, PA, USA

About the Editor

Born in Southern China, Professor Da-Wen Sun is a world authority in food engineering research and education; he is a Member of Royal Irish Academy which is the highest academic honour in Ireland. His main research activities include cooling, drying and refrigeration processes and systems, quality and safety of food products, bioprocess simula-tion and optimisation, and computer vision tech-nology. Especially, his innovative studies on vacuum cooling of cooked meats, pizza quality inspection by computer vision, and edible films for shelf-life extension of fruit and vegetables have

been widely reported in national and international media. Results of his work have been published in over 500 papers including 200 peer reviewed journal papers. He has also edited 12 authoritative books. According to Thomson Scientific’s Essential Science IndicatorsSM updated as of 1 July 2010, based on data derived over a period of ten years plus four months (1 January 2000–30 April 2010) from ISI Web of Science, a total of 2554 scientists are among the top 1 percent of the most cited scientists in the category of Agriculture Sciences, and Professor Sun tops the list with his ranking of 31.

He received a first-class BSc Honours and MSc in Mechanical Engineering, and a PhD in Chemical Engineering in China before working in various universities in Europe. He became the first Chinese national to be permanently employed in an Irish university when he was appointed College Lecturer at National University of Ireland, Dublin (University College Dublin, UCD) in 1995, and was then continuously promoted in the shortest pos-sible time to Senior Lecturer, Associate Professor and Full Professor. Dr Sun is now Professor of Food and Biosystems Engineering and Director of the Food Refrigeration and Computerised Food Technology Research Group at University College Dublin (UCD).

As a leading educator in food engineering, Professor Sun has significantly contributed to the field of food engineering. He has trained many PhD students, who have made their own contributions to the industry and academia. He has also given lectures on advances in food engineering on a regular basis in academic institutions internationally and delivered keynote speeches at international conferences. As a recognised authority in food engineer-ing, he has been conferred adjunct/visiting/consulting professorships from over ten top universities in China including Zhejiang University, Shanghai Jiaotong University, Harbin

About the Editor xxiii

Institute of Technology, China Agricultural University, South China University of Technology, Jiangnan University and so on. In recognition of his significant contribution to Food Engineering worldwide and for his outstanding leadership in the field, the International Commission of Agricultural and Biosystems Engineering (CIGR) awarded him the CIGR Merit Award in 2000 and again in 2006, the Institution of Mechanical Engineers (IMechE) based in the UK named him Food Engineer of the Year 2004; in 2008 he was awarded the CIGR Recognition Award in honour of his distinguished achievements in being among the top 1 percent of Agricultural Engineering scientists in the world. In 2007 he was presented with the AFST(I) Fellow Award by the Association of Food Scientists and Technologists (India), and in 2010 he was presented with the CIGR Fellow Award. The title of Fellow is the highest honour in CIGR and is conferred to individuals who have made sustained, outstanding contributions worldwide.

He is a Fellow of the Institution of Agricultural Engineers and a Fellow of Engineers Ireland (the Institution of Engineers of Ireland). He has also received numerous awards for teaching and research excellence, including the President’s Research Fellowship, and has twice received the President’s Research Award of University College Dublin. He is Editor-in-Chief of Food and Bioprocess Technology – an International Journal (Springer) (2010 Impact Factor = 3.576, ranked at 4th position among 126 food science and technology journals), Series Editor of the Contemporary Food Engineering book series (CRC Press / Taylor & Francis), former Editor of Journal of Food Engineering (Elsevier), and Editorial Board Member for Journal of Food Engineering (Elsevier), Journal of Food Process Engineering (Blackwell), Sensing and Instrumentation for Food Quality and Safety (Springer) and Czech Journal of Food Sciences. He is also a Chartered Engineer.

On 28 May 2010, he was awarded membership of the Royal Irish Academy (RIA), which is the highest honour that can be attained by scholars and scientists working in Ireland; and at the 51st CIGR General Assembly held during the CIGR World Congress in Quebec City, Canada on 13–17 June 2010, he was elected Incoming President of CIGR, and will become CIGR President in 2013–2014 – the term of his CIGR presidency is six years, two years each for serving as Incoming President, President, and Past President.

Preface

Food safety engineering is an emerging multidisciplinary field of applied physical sciences combining engineering knowledge and skills with food microbiology and safety. It aims to develop various processing techniques and hurdles in complex processes that are capable of addressing food safety challenges, with minimum alteration in food quality and nutri-tional value. Although in today’s competitive market, the food industry has striven to provide a wide variety of products with enhanced shelf-life, functionality and quality attributes in order to meet versatile consumer demands, concerns about food safety are still overwhelming among consumers, retailers, and the food industry. Such concerns accentuate the rapid developments in the specialisation of food safety engineering, as in recent years it has become clear that engineering approaches and methods play a critical role in the development and application of rapid and reliable techniques for microbial pathogen detec-tion and inactivation. Therefore there is an urgent need for a book devoted to this emerging area.

In order to meet the market demands, it is timely to publish the Handbook of Food Safety Engineering. The book is divided into five parts, beginning with Part One, which details the principles of food safety including microbial growth and modelling; followed by Part Two, covering new food safety detection methods; Parts Three and Four, discussing various traditional and novel thermal and nonthermal processing techniques for microbial inactivation; and concluding with Part Five on food safety management systems such as GMP, SSOP, HACCP and ISO22000.

As the first book in the subject area, Handbook of Food Safety Engineering is written by the most active international peers in the subject area with both academic and profes-sional credentials. The book is intended to provide the engineer and technologist working in research, development, and operations in the food industry with critical and readily accessible information on the art and science of the emerging food safety engineering. The book should also serve as an essential reference source to undergraduate and postgraduate students and researchers in universities and research institutions.

Da-Wen SunDublin, 2011

Part OneFundamentals

1.1 INTRODUCTION

The microbial world is defined by its size – organisms that generally have microscopic dimensions attract the interest of microbiologists. One consequence of this is that the birth of microbiology coincides with the advent of the microscope, which enabled us to see microorganisms for the first time. It is particularly associated with the work of Robert Hooke, who described the fruiting bodies of the mould Mucor on leather in 1665, and of Antonie van Leeuwenhoek, who saw bacteria while examining pepper-water infusions in 1676 (Bardell 1982; Gest 2009).

Despite these early observations, it was not until the nineteenth century and the work of luminaries such as Pasteur and Koch that microbiology can be truly said to have taken off as a scientific discipline. Like many who followed them, the interest of these pioneers was focused primarily on what microorganisms do rather than what they are. As a result, the struggle against infectious disease understandably looms large in any history of the subject. However, food microbiology, which studies the ways in which microbial activity associated with foods impinges on humankind, also has considerable practical and eco-nomic importance and was not entirely ignored. Pasteur (Debré 1994), for example, worked extensively on fermented food products such as wine, beer and vinegar, elucidating how deviations from the usual fermentation pattern can produce disorders in the product.

Currently the most fundamental division of the living world is into three domains based on differences in cell type: the Bacteria, the Archaea and the Eukarya. There are microor-ganisms of interest to food microbiologists in each of these domains. Members of the Bacteria naturally predominate but in the Eukarya, the fungi (yeasts and moulds) are extremely important in a number of areas such as food fermentations, spoilage and myco-toxins. The Archaea are of little significance in food other than in some very specific situ-ations such as extreme halophilic bacteria that can sometimes spoil heavily salted products and may play a role in the manufacture of products such as the fish sauces of Southeast Asia. Some basic features of the different groups of cellular microorganisms are described in Table 1.1.

One very distinctive group of microorganisms not included here are the viruses. These lack a cellular structure and can only multiply within a susceptible living cell. They are

1 Introduction to Food Microbiology

Martin Adams

Handbook of Food Safety Engineering, First Edition. Edited by Da-Wen Sun.© 2012 Blackwell Publishing Ltd. Published 2012 by Blackwell Publishing Ltd.

4 Handbook of Food Safety Engineering

much smaller than other microorganisms, have typical dimensions in nanometres as opposed to micrometres and contain only one type of nucleic acid (DNA or RNA). Some viruses pathogenic to humans can be transmitted by food and some which attack and use bacterial cells as their host (bacteriophages) can adversely affect starter bacteria used in food fermentations such as cheese making.

1.2 MICROORGANISMS AND FOODS

Foods are natural organic materials and as a consequence are rarely sterile. They carry a mixed population of organisms derived from the natural microflora of the plant or animal from which they originate and from the microorganisms that contaminate the food during

Table 1.1 Cellular microorganisms and their basic features.

Kingdom Characteristics Significance in food microbiology

Bacteria Single-celled organisms. Prokaryotes, i.e. they lack a nuclear membrane surrounding their DNA

Cells:• are enclosed by a cell wall containing the

polymer peptidoglycan• are generally spherical (coccus), rod-shaped

(bacillus), spiral or curved• are normally reproduced by binary fission

where one cell splits into two indistinguishable daughter cells

• may form chains or clumps• are sometimes motile by means of flagella

Different bacteria can be responsible for spoilage, foodborne illness and food fermentation processes

Eukaryotes Eukaryotic, i.e. possess a distinct nucleus enclosed by a nuclear membrane and containing their DNA

Fungi have cell walls containing the polymer chitin and include the moulds and yeasts. The moulds are multicellular organisms. They grow as filaments called hyphae which grow, spread and branch to form a visible mass known as mycelium. Can produce characteristic structures associated with spore production and dispersal

Yeasts are unicellular fungi and are generally spherical or oval cells, larger than bacteria that multiply by budding off daughter cells and sometimes by fission

Protozoa are unicellular, eukaryotes

Some moulds produce toxic secondary metabolites known as mycotoxins

Moulds and yeasts are both important in the production of a wide range of fermented foods

Some pathogenic protozoa can be transmitted by foods

Archaea Prokaryotic cells (see above). Where they possess cell walls peptidoglycan is absent

Often found in extreme environments, e.g. extreme halophiles in very salty conditions

Do not cause disease in humansMay be responsible for spoilage

of some high salt products and contribute to the production of high salt products such as fish sauce

Introduction to Food Microbiology 5

Fig. 1.1 The food microflora.

Raw materialmicroflora

Contamination

Growth/Survival/Death

Food microflora

Storage conditions(Temperature, humidity,gaseous atmosphere)

Properties oforganism (growthrate, substrateaffinity…)

Properties offood (pH, aw,redoxpotential…)

Processing

harvesting/slaughter, processing, storage and distribution. The precise composition of this microflora will depend on the microorganisms present and whether they die, survive or multiply in the product up to the point at which it is consumed. Borrowing a term from ecology, a food’s microflora is frequently described as an association and is often charac-teristic of a particular food type (Fig. 1.1).

In most cases the presence of a food’s microflora will go unremarked by the consumer. Occasionally it becomes apparent, however, when it manifests itself in one of three ways:

• it causes illness;

• it causes spoilage;

• it produces desirable changes in the food’s sensory and/or keeping qualities.

1.3 FOODBORNE ILLNESS

Food has long been established as a vehicle for illness, and foodborne pathogens are described in detail in Chapter 2 of this volume. The precise mechanisms by which they cause illness can be very complex but in its broadest terms there are two fundamental scenarios. In the first, the organism grows in the food and produces toxin(s) which are then ingested along with the food, causing illness. This occurs with organisms such as Staphylococcus aureus, Clostridium botulinum and cereulide, the emetic toxin produced by Bacillus cereus, as well as some toxic secondary metabolites of fungi; mycotoxins such as aflatoxin produced by Aspergillus flavus and A. parasiticus. For toxin production to occur it is necessary for the organism to grow in the food and so these types of food poi-soning can be prevented by ensuring that conditions in the food or its storage environment do not allow the growth of the pathogen concerned.

With other bacterial pathogens the pathogenic effect is elicited by the activity of the viable organism in the gut, so that living cells rather than a microbial product need to be ingested. The infectious potential of an organism will depend on a number of factors such

6 Handbook of Food Safety Engineering Introduction to Food Microbiology 7

as the particular strain of the organism, the food vehicle, and the susceptibility of the indi-vidual consumer. Strains differ in their virulence: some foods, particularly fatty foods, are thought to protect bacteria from antimicrobial barriers such as the stomach’s acidity, and foodborne illness can be much more severe in vulnerable groups such as the very young, the very old, the very sick, the immuno-compromised and, in the case of listeriosis, preg-nant women and their babies.

Infectious potential can be described in the form of a dose–response curve which relates the ingested dose of an organism to the chances that it will cause illness, although in prac-tice there is often insufficient data available to produce such curves with any great confi-dence (Holcomb et al. 1999). Since risk is related to dose, if the pathogen is able to grow in a food then the risk of its causing illness will increase. However, unlike those organisms that produce a toxin in the food, it is not essential that infectious pathogens grow in the food, and mere survival may well suffice to cause illness. If conditions prevent growth but do not necessarily inactivate the organism, as for example in a dried food, then risk will not increase but remain static. Examples of this situation have been noted with outbreaks of Salmonella and E. coli O157 infections caused by acidic products such as apple juice and home-made mayonnaise where the organism cannot necessarily grow but was able to survive in sufficient numbers to cause illness (Besser et al. 1993; Centers for Disease Control and Prevention 1975, 1996; Lock and Board 1995).

In most cases foodborne illness is characterised by symptoms restricted to the gastroin-testinal tract such as some combination of nausea, vomiting, stomach pains and diarrhoea. Quite a number of different organisms can produce this type of illness and a number of these are described briefly in Table 1.2. Where such illness is the result of toxin production in the food its onset is generally more rapid than infections where the organism has to have time to grow in the gut to produce its effect. Some foodborne pathogens exert their effect beyond the confines of the GI (gastrointestinal) tract such as typhoid and paratyphoid fevers, botulism, listeriosis and the Haemolytic-Uraemic Syndrome (HUS) caused by Verotoxin-producing E. coli.

In addition to the personal suffering that it causes, foodborne illness is of considerable economic importance through its effect on economic activity and the burden that it places on health services. The incidence of foodborne illness in society is difficult to estimate precisely. Most countries produce some relevant statistics but they are always acknowl-edged to be an underestimate of the true level. The degree to which this happens will depend on the efficiency of the data collection system as well as the particular illness concerned: more severe illness is more likely to be reported. Some indication of the extent of under-reporting was obtained from the Infectious Intestinal Disease (IID) Study conducted in England in the period 1993–1996. This was concerned with the totality of infectious intes-tinal disease and was not therefore confined to those caused by food, but it showed that only one case was reported to national surveillance for every 23 cases presenting to their family doctor 7 and for every 136 cases that occurred in the community at large. The degree of under-reporting was lowest for a well-recognised pathogen such as Salmonella with one case appearing in the statistics for every 3.2 cases in the community. It was slightly worse for Campylobacter infections (7.6:1) and huge for norovirus (1562:1) (Wheeler et al. 1999). Similar studies in other developed countries have shown broadly the same picture. A second IID study is currently in progress in England to determine how (or whether) the situation has changed in the last 10 years.

Over the last half century, improvements in reporting procedures, in our understanding of the behaviour of foodborne pathogens, in methods to control them, and the development

6 H

andbook of Food Safety EngineeringIntroduction to Food M

icrobiology 7

Table 1.2 Principal microorganisms associated with enteric symptoms.

Organism Incubation period Duration of symptoms Clinical features Common mode of transmission

Aeromonas spp. Unknown Variable V, D Food, WaterBacillus cereus Emetic syndrome 1–5 h 24 h N, V, (D, P) Food Diarrhoeal syndrome 8–16 h 24 h D, V, (N, P) FoodBacillus subtilis 1–4 h 24 h N, V, D FoodBac. licheniformis 2–14 h 24 h D, P FoodCampylobacter jejuni, C. coli 2–5 d 2 d−1 week D, P, Fe, B Food, Water, Animal contactClostridium perfringens 12–18 h 24 h D, P FoodEnterovirulent Escherichia coli Attaching and effacing (AEEC) Unknown Unknown D Food Diffusely adherent (DAEC) Unknown Unknown D Unknown Enteroaggregative (EAggEC) 20–48 h Unknown D, B Food Enteroinvasive (EIEC) 12–72 h 5–7 d D, B Food, Water Enteropathogenic (EPEC) 12–72 h <2 wk D Person-to-person, Food, Water Enterotoxigenic (ETEC) 12–72 h 3–5 d D Food, Water Verotoxin-producing (VTEC) 1–6 d 4–6 d (not HUS) D, B, HUS Food, Water, Person-to-person, Animal contactSalmonella (non-enteric fever) 12–72 h <3 wk V, D, Fe Food, Person-to-person, Animal contactShigella 1–7 d <2 wk D, B Person-to-person, Food, WaterStaphylococcus aureus 2–4 h <12–48 h V, P, Fe FoodVibrio cholerae 2–3 d <7 d D Water, FoodVibrio parahaemolyticus 12–18 h <7 d D FoodYersinia 3–7 d 1–3 wk D, P, Fe FoodNorovirus 1–3 d 1–3 d V, D, Fe Person-to-person, Food, Aerosols

Key: B, blood in stool; D, diarrhoea; Fe, fever; HUS, haemolytic uraemic syndrome; N, nausea; P, abdominal pain; V, vomiting.Source: Adapted from Food Standards Agency (2000).


of appropriate food safety management tools, have been hugely important weapons in the struggle against foodborne illness. They have had to be deployed, however, not in a static situation but in a continually shifting scenario where a number of factors are acting to increase the incidence of foodborne illness around the world:

• Increased industrialisation and urban living have meant that the food chain has become longer and more complex, increasing opportunities for contamination. It also means that more people are likely to be affected by a single breakdown in food hygiene.

• In poorer countries increased urbanisation and rapid population growth have not been matched by development of the health-related infrastructure, including basic sanitation, and this has led to increased risk of contamination of the food and water supply.

• Increasing affluence in other areas has led to greater consumption of foods of animal origin such as meat, milk, poultry and eggs. These foods are recognised as more common vehicles of foodborne pathogens and this situation can be exacerbated by the methods of intensive production required to supply the market.

• There is greater international movement of both foods and people as a consequence of trade, tourism and migration.

• Changing lifestyles also means that food preparation may be in the hands of the rela-tively inexperienced or untrained and more people may be eating pre-prepared foods from street vendors or other catering establishments.

• An increasing proportion of the population is more susceptible to foodborne illness – the malnourished, the elderly, the very sick and the immuno-compromised (Adams and Motarjemi 1999).

Hence, despite huge improvements in our understanding of the organisms concerned, it would be wrong ever to describe the struggle against foodborne illness as over. The best that can be hoped for is to maintain the upper hand.

1.4 FOOD SPOILAGE

Microorganisms play a crucial role in the economy of the biosphere where they are respon-sible for the decomposition of organic materials and recycling the elements they contain. Microbial spoilage occurs when the early stages of this process in a food adversely affect its sensory properties; generally its appearance, odour or taste. This can be a very subjec-tive process; what may be spoiled for one person can be perfectly acceptable to another and it is also influenced by social, economic and cultural factors.

Over the years there have been numerous studies identifying the chemical or biochemi-cal basis of spoilage in more perishable food such as fish and meat, using sophisticated analytical techniques to identify the chemical composition of an off odour or flavour. However, it remains true that ‘Current methods for the rapid detection of spoilage in meats are inadequate . . . they are time consuming and labour intensive and therefore give retro-spective information’ (Ellis and Goodacre 2006). Sometimes we have yet to surpass the abilities of our own senses.

What is clear, however, is that it is generally a small subset of the total microflora on a product that is responsible for its initial spoilage. Work establishing the relationship between specific organisms and the development of spoilage characteristics in fish goes back to the 1950s (see, for example, citations in Lerke et al. 1965). These and related studies led to


the more general concept of specific spoilage organisms (SSOs), individual organisms responsible for producing the most pronounced quality defect, and the development of microbiological media for their detection and enumeration (Gram and Dalgaard 2002; Jespersen and Jakobsen 1996).

Although not all food spoilage is necessarily microbial in origin, microbiological spoil-age is paramount in more perishable foods such as meat, fish and dairy products. The reason for the loss of acceptability can vary and is often commodity-specific, reminiscent of Tolstoy’s dictum that ‘All happy families resemble one another but every unhappy family is unhappy in its own way.’ To illustrate this, some examples of different types of spoilage are presented in Table 1.3.

One feature of microbial spoilage that can often help distinguish it from nonmicrobiologi-cal spoilage is its apparent sudden onset. Chemical or physical reactions tend to proceed in a linear fashion whereas microbiological reactions often reflect the exponential increase in microbial numbers in the product. Thus it may take some time to reach a threshold level of a particular factor that determines acceptability, e.g. an off odour, but once that level is reached logarithmic growth of the causative organism ensures that it is very rapidly surpassed. Another characteristic of microbiological spoilage is that it can also be passed from one batch of product to another by material (and microbial) transfer from spoiling product to a fresh one.

1.5 FOOD FERMENTATION

From the preceding two sections it is understandable how, from the point of view of the food safety engineer, microorganisms can be viewed solely as the enemy. Equipment and production processes must be designed and engineered to exclude, discourage or destroy

Table 1.3 Food spoilage.

Cause/example

NonmicrobiologicalRancidity Autoxidation or lipolysis of fats – fish, meat dairy productsStaling Retrogradation or degelatinisation of starch – baked goodsSeparation Loss of emulsion stability – mayonnaiseFreezer burn Loss of water from frozen material – frozen fish, meat and pastaWilting Loss of moisture, limpness – leafy vegetablesBrowning Enzymic caused by polyphenol oxidase, bruising – fruits

Non-enzymic – caramelisation as a result of Maillard reactionsIce recrystallisation Ostwald ripening of ice crystals to reduce surface area: volume ration – ice

creamCold injury Discolouration, loss of texture – tropical fruits such as bananas

MicrobiologicalVisible growth Mould growth, visible yeast colonies – jam. Fruit

Turbidity – wines, beers etc.Slime production Bacterial polysaccharides – lactic acid bacteria in fruit juices and beerPolymer degradation Soft rots – pectinolytic bacteria in vegetablesGas production Carbon dioxide production – yeast growth in fruit juices, clostridial growth

in canned foodsOff flavours Microbial breakdown of food components – spoilage of fish and meatOff odours Microbial breakdown of food components – spoilage of fish and meatPigment production Pigmented microbial growth – halophilic bacteria on salt fish


microorganisms. It is, however, worth remembering that there is a huge group of foods where certain microorganisms exert a benign effect, transforming the properties of a food material in a highly desirable way. One only needs to think of the transformation that occurs in relatively prosaic materials such as milk or grape juice when they are made into one of countless varieties of cheese or wine.

Traditionally these processes relied on natural sources of microorganism to accomplish the desired fermentation. The initial processing of the raw material is in some way selective and encourages the growth of the required components of the microflora, enabling them to outcompete other organisms present and exert their beneficial effect. Nowadays, particu-larly in larger scale operations producing foods such as cheese, yoghurt and salami, no chances are taken and commercially produced starter cultures are used to ensure a repro-ducible and reliable fermentation virtually 100% of the time.

During a food fermentation the activity of microorganisms frequently contributes to improved keeping quality in the product by inhibiting the normal spoilage flora. The lactic acid bacteria are notable in this regard and are responsible for numerous fermentations of milk, meat and vegetables to produce products such as yoghurt, salami and sauerkraut. The lactic acid bacteria, a group of phylogenetically related Gram-positive organisms, generate their cellular energy as a result of the fermentation of sugars to produce, principally lactic acid but also in some cases, and in smaller quantities, ethanoic (acetic) acid and ethanol. The organic acid reduces the pH which inhibits the growth of many bacteria but it also exerts a more specific antimicrobial effect through the ability of the weak undissociated organic acid to penetrate the plasma membrane and acidify the cell’s cytoplasm. Microbial cells have (homeostatic) mechanisms in place to maintain a relatively equable and constant environment inside the cell to promote efficient cell metabolism, but these come at a cost. As cellular energy is diverted away from supporting vegetative growth to maintaining pH homoestasis, growth is slowed and, if the burden becomes excessive, growth is stopped altogether and the cells begin to die.

The production of organic acids is undoubtedly the principal mechanism by which lactic acid bacteria inhibit competitors, though a number of other antimicrobial factors have been identified. These include bacteriocins (polypeptides which are produced by bacteria, not just lactic acid bacteria, and which are normally inhibitory to closely related species). One bacteriocin produced by strains of Lactococcus lactis (a common starter organism used in the production of cheese), nisin, has a broader range of activity than most bacteriocins. It is active against most Gram-positive bacteria but is particularly inhibitory to the outgrowth of bacterial endospores. As a result it is produced commercially and has found widespread use as a food preservative in heat-processed foods such as canned foods, processed cheeses, dairy desserts and pasteurised egg where the survival and growth of spore formers can be a problem. While this can clearly be an advantage to the producing organism, production of bacteriocins in situ does not necessarily improve food fermentations since other lactic acid bacteria important in the overall process may also be inhibited along with less desir-able species. In fact nisin was first discovered as a result of the failure of a cheesemaking process when its activity against other lactic acid bacteria slowed the fermentation process.

1.6 MICROBIAL PHYSIOLOGY AND FOOD PRESERVATION

A review by Mossel and Ingram published in 1955 (Mossel and Ingram 1955) was seminal in the development of food microbiology in the analytical approach that it adopted to describing how the particular microbial association in a food might develop. This was based


on an understanding and analysis of what they termed intrinsic and extrinsic factors associ-ated with the food (properties of the food such as its pH or nutrient content and its storage environment such as the relative humidity or temperature) and how these interact with the physiology of different groups of microorganisms.

A detailed and up to date discussion of these factors affecting microbial growth and survival is the subject of Chapter 4 in this volume. Knowledge of how these factors influ-ence the behaviour of different organisms can be employed to predict the types of micro-organisms that would be associated with specific foods, for example the tolerance of yeasts and moulds for low water availability and pH means that these organisms predominate in the spoilage of products such as grains or yoghurt. It can also be used in a more quantita-tive way to predict how a particular organism (usually a pathogen) will survive or grow under a given set of intrinsic and extrinsic factors. Trying to put the predictions on a sound quantitative basis has been the subject of much research activity and has resulted in the availability of tools such as ComBase (http://www.combase.cc/toolbox.html). These devel-opments in predictive modelling of both survival and growth are discussed in Chapters 5 and 6.

All food preservation techniques exert their effect by manipulating one or more intrinsic or extrinsic factors with a view to slowing or stopping microbial growth or inactivating (killing) microorganisms. Where microbial growth is slowed, shelf life is extended and different organisms may predominate, changing the character of the spoilage when it does occur. Similarly where microorganisms are inactivated or killed, the shelf life will depend upon what types of organisms can survive the inactivation treatment or whether the product is subject to any post-treatment contamination.

Some inactivation processes, such as ionising irradiation and hydrostatic pressure, employ environmental factors that were not included as extrinsic factors by Mossel and Ingram (1955). This was because factors such as electromagnetic radiation and pressure are not normally sufficiently extreme or variable in the day-to-day food environment to have a significant influence on microorganisms in foods. In modern food processing, however, they can be and are deliberately manipulated to levels where they inactivate microbial cells.

Though modification of one intrinsic or extrinsic factor can often achieve an acceptable degree of preservation, this often means that the product’s qualities are changed in a dra-matic way. For example, to preserve a food by acidification it may be necessary to produce a very acidic product of possibly limited acceptability. More frequently though a number of factors are adjusted less severely and operate in concert to achieve the overall antimi-crobial effect in what is known as the hurdle concept or multiple-barrier concept of food preservation (Leistner and Gould 2002). Each factor on its own modifies the food’s sensory properties to a limited extent yet achieves an acceptable overall aggregate effect in terms of microbial inhibition. This is the basis of many traditional food products such as con-serves and cured fish and meats and is frequently an approach adopted in the development of new food products.

Fermented foods are often excellent examples of the hurdle concept. For example, the hurdles of low pH, ethanol content, dissolved CO2 and hop resins all combine to restrict the range of organisms that can grow in and spoil beer. The hurdles present in a fermented meat product such as salami are presented in Table 1.4. In fermented foods, the fermenta-tion process is frequently combined with reduction in the water activity of a product through drying and/or the addition of a solute such as salt or sugar. Examination of the keeping qualities of a spectrum of related products demonstrates quite clearly that reduction in water activity has a greater impact on shelf life than fermentation, as can be seen by

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comparing the shelf life of yoghurt with cheese or the shelf lives of cheeses with different moisture contents e.g. cottage cheese and parmesan. It can also be seen in the shelf lives of a range of fermented fish products from Thailand (Adams 2001).

The use of food preservation techniques is essential to secure the food supply of large urban populations remote from the site of food production. They operate either by reducing the microbial load on a product and/or inhibiting the growth of viable microorganisms present on the food thus slowing the rate of spoilage. Most food preservation techniques were developed empirically before the existence of microorganisms was appreciated but they have been refined considerably in the light of our developing understanding of the types or organism responsible for spoilage and their characteristics. For example, the crude empirical approach used in the early days of canning is now replaced by the application of well-defined time and temperature regimes to ensure the desired lethality and an accept-able spoilage rate.

With very few exceptions, foods will always have a defined shelf life, after which they are deemed to be unacceptable for consumption. It is the responsibility of the food manu-facturer to determine the shelf life of their products. Predictive models describing the growth of microorganisms in foods under a variety of environmental conditions have already been mentioned (see above). In these the focus has been primarily on predicting the growth of pathogens rather than spoilage organisms. Although there have been efforts towards developing mathematical models to describe spoilage and thus assist in the deter-mination of shelf life (Braun and Sutherland 2006), shelf-life determination is still largely performed on an empirical basis. Product is stored at appropriate temperatures and tested periodically to determine a shelf-life end-point. The end-point can be defined by a chemical or microbiological test but, as noted above, sensory evaluation is often used since it is quicker, more sensitive and is generally the technique used by the consumer (Ellis and Goodacre 2006; IFST 1993). This can be quite a time-consuming exercise and so there is some interest in accelerated shelf-life determination. It usually employs a higher incubation temperature than would normally be expected but, based on previous experiments, extrapo-lates mathematically back to the expected storage temperature. The advantages are obvious but there are a number of problems relating to changes in the make-up of foods at different temperatures as well as the fact that (to the delight of Hegelians) quantitative changes in temperature can produce qualitative changes in the spoilage microflora and the SSO.

1.7 MICROBIOLOGICAL ANALYSIS

Fundamental to studying the behaviour of microorganisms in foods is the ability to isolate and enumerate them. Assuming a microbial cell typically occupies about 1–10 µm3, then a population of 105 mL−1 would correspond to a concentration of about 0.1–1.0 ppm. In the

Table 1.4 Antimicrobial factors in a typical fermented sausage.

NitriteLactic acid bacteriaAntimicrobial herbs and spicesReduced water activity – salt + dryingLow redox potential(Antimicrobials from smoke)


light of the performance of analytical techniques currently available this might seem a fairly modest challenge, but the fact that microbial cells are composed of essentially the same constituents as their surrounding environment, namely proteins, lipids, polysaccharides, nucleic acids and water indicate that the problem becomes rather less straightforward. For most of its history, food microbiology (and microbiology in general) has solved this problem by exploiting the microorganism’s unique ability to self-amplify, i.e. grow expo-nentially. Thus a single microorganism with a doubling time of 20 minutes will produce more than 10 million cells in 24 hours, sufficient to produce turbidity in a broth medium or a small colony on solid media. The critical problem is giving the organisms an environ-ment in which they can multiply.

In the case of enumerating organisms, a food sample is generally diluted down in a rela-tively inert liquid medium that will not subject the microorganisms to undue osmotic or pH stress and the dilutions are inoculated on to an appropriate solid medium and incubated. Several dilutions are usually inoculated in this way so that a countable number of colonies is obtained – not too few to give a reasonably accurate count but not so many that the plate is difficult to count and organisms are close enough to inhibit one another, thus preventing colony formation. With a reasonable count and knowledge of the dilution counted, then this can be related back to the microbial concentration in the original material.

There is no universal culture medium; whether an organism grows will depend upon the components of the medium and the incubation conditions such as temperature and gaseous atmosphere. A whole industry has developed around exploiting nuances in the biochemistry of microorganisms to produce selective and/or diagnostic media that favour the growth of a particular target organism and/or allow the presence of target organisms to be clearly distinguished from other components of the microflora. The common ingredients that go into a laboratory medium and their function are outlined in Table 1.5.

Table 1.5 Typical media components and their function.

Component Function

Carbohydrate: glucose, sucrose, lactose, starch, (glycerol)

Source of energy and carbon. Sometimes specific carbohydrates act as an elective agent allowing the growth of target organisms

Source of amino nitrogen: peptones or other digests or extracts of meat, casein, yeast, soya

Many microorganisms cannot utilise native protein or grow better when provided with as source of predigested or hydrolysed protein. Can also sometimes serve as a source of energy and carbon

Growth factors: yeast extract Source of vitamins and co-factorsPhosphates Source of the elemental phosphorus and buffering capacity to control

pH changes in the mediumMinerals salts and trace

metals: phosphates, sulphates

To provide key elements such as sulphur, phosphorus, Ca2+, Mg2+, K+, Fe3+. Numerous trace elements or micronutrients may be added but are often present in sufficient quantities as contaminants of other medium constituents

Indicators: neutral red, bromocresol purple

To indicate pH changes in the medium signal utilisation or production of acidic or basic compounds

Selective agents: antibiotics or dyes

To exert a selective antimicrobial action that inhibits a proportion of the microflora but allows growth of target organism(s)

Agar Gelling agent


Though cultural techniques are simple and relatively straightforward to perform, there are drawbacks to conventional cultural techniques. They can be labour-intensive and have high recurrent costs, but the most widely acknowledged problem is the long elapsed times that are sometimes required before a result is obtained. Waiting for a microorganism to grow and produce a signal in the form of turbidity or a colony can typically take at least 24 hours. When an isolation and identification procedure involves more than one cultural step the problem is compounded so, for example, the traditional internationally recognised cultural technique for the isolation of Salmonella takes at least four days to produce a negative result. Where food is held on a positive release system this causes costly delays in releasing product and increased storage costs. Where product in process is being tested it means that results cannot be used as a real-time monitoring procedure for critical control points in a Hazard Analysis and Critical Control Points (HACCP) scheme (see below). As a result, numerous techniques have been developed to refine isolation and identification procedures and some of these are the subject of chapters in Part Two of this book.

1.8 FOOD SAFETY MANAGEMENT SYSTEMS

In parallel with improvements in the scientific basis of food microbiology, developments have also been made in the more prosaic business of ensuring that this knowledge is applied in a systematic way in order to be certain that foods are produced, processed and served with the minimum risk of causing illness. This area is the subject of the third and final section of this volume and will not be dwelt on in great detail here.

Various religious and social prohibitions about eating certain kinds of foods and how they should be handled go back a very long way. One motivation for these may have been an observed association between particular foods and behaviours and outbreaks of illness but this is probably not the whole story, particularly in regard to religious taboos. However there are some more recent examples where the association between a food and illness is clearly made. Thus in 1802 in Stuttgart an official warning was issued detailing the symp-toms of botulism, the dangers associated with eating spoiled sausage, and the proper methods for preparing and curing sausages (Dickson 1918).

With the advent of microbiology as an experimental scientific discipline, the possibility of testing foods to see if they contained pathogens or other organisms of concern became a possible means for controlling quality. This approach persists to this day although it now plays more of a complementary role to other management schemes since its limitations are widely recognised. The distribution of organisms in solid foods means that truly representa-tive samples for testing are not easily obtained – the only way to increase confidence in a test result is to take an unfeasibly large proportion of the lot for testing. Hence with any realistic sampling scheme there is an appreciable chance that acceptable product will be rejected or that unacceptable product will be accepted. A further drawback is that results from failing samples do not necessarily indicate where in the production process a problem arose. Therefore in the absence of any remedial information similar failures in the future cannot be prevented. Thus it became recognised that application of good practices during the manufacture or production of food was a more effective way of controlling quality. This view was summarised by Sir Graham Wilson at a meeting on microbiological stand-ards held in 1969:

handbook of food safety engineering

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