risky foods, safer choices avoiding food poisoning
DESCRIPTION
Risky Foods, Safer Choices Avoiding Food Poisoning by Paresh c. RayTRANSCRIPT
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RiskyFoods,SaferChoices
ABOUTTHEAUTHORS
PETERCEREXHEisanawardwinningjournalistwhohasalsoworkedasalawyerandeditor.HespenteightyearsasajournalistforChoicemagazine(thejournaloftheAustralianConsumers'Association).HeistheauthorofthehighlysuccessfulbookBeforeandAfterRetirement(ChoiceBooks,1998)andhascontributedchapterstoseveralothertitles.
DRJOHNASHTONisaconjointSeniorLecturerinFoodTechnologyattheUniversityofNewcastleandalsodirectsaleadingAustralianfoodtestinglaboratory.Heistheauthorofseveralhighlysuccessfulbooksonhealthandtheenvironment,hismostrecenttitlebeingThePerilsofProgress(UNSWPress,1998).DrAshtonisanelectedFellowoftheRoyalAustralianChemicalInstituteandaprofessionalmemberoftheAustralianInstituteofFoodScienceandTechnology.
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RiskyFoods,SaferChoicesAvoidingFoodPoisoning
PeterCerexhe+JohnAshton
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ACKNOWLEDGEMENTS
Abooklikethisonecrossesmanyareasofindividualexpertiseandreliesonthecontributionsofexpertsandonavastrangeofpublishedresearchandopinionfromallcornersoftheworld,whetherinacademicorpopularjournals,websites,booksornewspaperreports.ThemosthelpfulofthesereferencesarelistedunderFurtherReading,forthosewhowishtopursuemattersingreaterdepththanispossiblehere.Werecommendthesereferencestoyou.
Theauthorswouldliketotakethisopportunitytoacknowledgethespecificassistanceandsupportofthosewhoaidedthisproject.Inparticularwewouldliketothankthefollowingpeople,gratefullyacknowledgingtheircontribution:DrMichelleAdamsandDrBobHoskenattheCentreforFoodIndustryResearchandDevelopmentattheUniversityofNewcastleDrSidCole,FellowoftheAustralianInstituteofFoodScienceandTechnologyandMattO'NeillandstaffattheAustralianConsumers'Association.RosemaryStantonkindlyreadthemanuscriptandmademanyusefulsuggestions.
AUNSWPressbook
PublishedbyUniversityofNewSouthWalesPressLtdUniversityofNewSouthWalesSydney2052Australiawww.unswpress.com.au
P.CerexheandJohnAshton2000Firstpublished2000
Thisbookiscopyright.Apartfromanyfairdealingforthepurposeofprivatestudy,research,criticismoreview,aspermittedundertheCopyrightAct,nopartmaybereproducedbyanyprocesswithoutwrittenpermission.Inquiriesshouldbeaddressedtothepublisher.
NationalLibraryofAustraliaCataloguinginPublicationentry:Cerexhe,Peter.Riskyfoods,saferchoices:avoidingfoodpoisoning.Bibliography.Includesindex.ISBN0868405221.1.Foodpoisoning.2.Foodcontamination.3.Food.4.Foodservice.5.Foodhandling.6.Foodindustryandtrade.7.Cookery.I.Ashton,John.II.Title.363.192
PrinterGriffinPress,AdelaideDesignerDiQuick
CONTENTS
IntroductionWhyGetsoWorkedupaboutItAll? 4
Part1UnderstandingFoodPoisoning,andYourProtection
7
Chapter1We'reAllinThisTogether
8
WhatIsFoodPoisoning?WhatAretheSymptoms?HowBigIstheProblem?TheFoodTheyCallBackCanYouTellIfFoodIs'Off'?HowDoYouProtectYourself?
Chapter2KnowYourEnemy!
19
BacteriaVirusesYeastsandMouldsParasitesAccidentalExtras
Chapter3WhoIsMostVulnerable?
34
ChildrenThosewithReducedImmunityWhyAreOlderPeopleatGreaterRisk?PregnantWomen
Chapter4HowDoIProtectMyself,MyFamilyandFriends?
38
HowYourBodyProtectsItselfFoodStorage,PreparationandPreservationRecognisingFoodAdditives
PartIIAWalkthroughtheShoppingCentre
45
Chapter5TheDelicatessen
46
SmallgoodsRulesforSmallgoodsHerbsandSpicesDairyFoodsJamsandPreservesPate
Chapter6TheGreenGrocer'sShop
59
PotatoesMushroomsandFungiAlfalfaSproutsPackagedRawSalads
ManteshwerTypewritten Text
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ManteshwerTypewritten Text
ManteshwerTypewritten Text
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Chapter7TheButcher'sShop
64
SpoiledMeatMincedMeatsandSausagesWholePoultryMarinatedMeatsProtectionStrategies
Chapter8TheFishShop
69
FishyRisksATaleofToxinsMolluscsProcessedFish
Chapter9ASweetTooth
75
CakesIcecreamandOtherFrozenTreatsChocolate
Chapter10TheSupermarket
81
CannedFoodsFrozenFoodsTheGoodEggVegetarianMeatSubstitutes'Useby'DatesIsThatMould?
Chapter11Drinks
88
TheTownWaterSupplyIsBottledWatertheAnswer?FruitJuicesMilkDrinksDirtyIce
Chapter12TakeawayFoodShops
95
HamburgersSaladBarsDonerKebabsRicePizzaChickenSandwiches:TheSafeAlternative?WhenSaferChoicesAreImportanttoYouFoodWorkersSickatWorkPicnicTips
PartIIITravel,PartiesandWhoLooksafterUs
105
Chapter13EscapingtheTravelBugs
106
WhichCountriesPosetheGreatestRisk?CruiseBluesChoosingaRestaurantSafeWaterBottledWater:IsItSafe?ProbioticaidSalads:ADifficultChoice
Chapter14It'sMyParty...
114
CookinginAdvanceDealingwithLeftovers
Chapter15SchoolLunches
117
CanteenorHomePackedLunches?TipsforPackagedLunchesChildrenandGastroenteritis
Chapter16FoodAllergies
120
WhatAretheMainFoodAllergens?HowCanIFindoutIfIHaveaFoodAllergy?
Chapter17StoringFood
124
TheFreezer:WhatCanItDoforMe?TheRefrigeratorFridgeandFreezerTipsHowLongWillFoodLast?InthePantry
Chapter18YouandYourKitchen
134
HowShouldICleanMyKitchenBenches?CuttingBoards:WoodorPlastic?PersonalHygiene
Chapter19TheBusinessofFood
139
QualityControlDetectingtheForeignLegionTestingandComplaintsNewTechnologiestotheRescueNewHopes,NewProblems
Chapter20FutureUncertain
148
AretheRisksIncreasingorDecreasing?GettingaroundandBecomingKnownAreWeOverlyDependentonAntibiotics?ChangingOurPreferencesTheGeneArmouryARoleforGovernment
Chapter21OnefortheRoad
157
Glossary 158
FurtherReading 159
Index 160
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INTRODUCTION:WHYGETSOWORKEDUPABOUTITALL?
Foodpoisoninghappensweallknowthat.Butitusuallypassesquicklyandwegetwellagain.Itwasjustbadluckoristheremoretoit?
Theworldweliveinisverydifferentfromtheworldof30yearsago.Notonlyaretheremorepeople,moretravelandterribleflu,andothervirusesmovingaroundtheworldwithastonishingspeed,butalsonewfoodpoisoningbacteriasuchastheingloriouslynamedE.coliO157:H7,firstreportedbackin1982.Thisbacterium,whichisnowcarriedintheintestinesandfaecesofupto40percentofcattleinsomecountries,cancausenotonlyvomitinganddiarrhoeabutcanleaveanaffectedchildpermanentlywithdiabetes.Ithasalsobeenknowntoproducebraindamage.
Fortunatelynotallfoodpoisoningbacteriaproducesuchseriousandpermanentsymptoms.And,inacountrylikeAustralia,wearemercifullyfreefrommuchseriousfoodborneillness.Yetthehumanraceisinadvertentlyplayingaroleinitsownfoodhazarddevelopment.Technologyhasproducedtheconveniencesofmobilephones,microwaveovens,cheaptravel,megafarmsandfastfoods,butsomehowintheequationwehavealsocreatedanenvironmentconducivetotheemergenceandspreadoffoodpoisoningmicroorganismswiththepotentialtoaffectusall.
Thiswillchangethewaywelive.
Manyofthefoodpoisoningbacteriawhichnowconcernauthorities,suchasCampylobacterjejuni,haveonlyemergedinthepast25years.Yetmorethan11,000casesofCampylobacterjejunifoodpoisoningwerereportedinasmallcountrylikeAustraliain1998,withanuntoldnumberofcasesgoingunreported.
Thischangingfoodenvironmenthasnecessitatedthewritingofthisbook.Itcontainstheinformationyouneedtohelpyoutochoose,storeandpreparefoodinwayswhichwillreducetheriskofcontractingafoodborneillness.Wediscussthingslikemealplanning,cookingtemperatures,safefoodstorageandmanyotherfactorswhich,webelieve,nowrequiremorediligencethanweperhapshavegiventheminthepast.
Therearerealincentivesfordevelopinggoodhabits:
Yourfoodwilltastebetterandbebetterforyou.Thesamegoodpracticeswhichkeepfoodsafealsopresentyouwithmealsthatarefreshandwiththeirfullcomplementofnutrients.Badpracticesdegradeyourfoodasthebacteriamultiply.Goodpracticesdeliverfoodwiththerightaromas,texturesandtastes.
You'llsavemoney.Doctors'bills,medicinesandtimeoffwork(orasouredholiday)aretheexpensiveconsequencesofaboutoffoodillness.
Yourfriendswillcontinuetocomeovertoyourhouse.Ifguestsfeeltheygotfoodpoisoningatyourplace,oriftheysawthewaythefoodwaspresentedandwerenotimpressed,youmightbeleftwonderingwhytheynolongeracceptyourdinnerinvitations.
Youlearnhowtolookaftervulnerablepeople,helpingthemtogoodhealth.Manyofthefoodbornepathogensareofparticularconcerntothosewhoaremostvulnerableinoursocietythefrailelderly,babiesandveryyoungchildren,thoseundergoingcancertreatmentorotherwisewithloweredimmunity.Goodfoodpracticeshelpsupportthehealthofyourfamilyandfriends.
Tohelpyouwiththistask,wehaveprovidedagreatdealofinformation:aboutmicroorganismswhichcanmakeussick,howtheygettous,howtheyworkwithinus,ourdefences,howthefoodindustryworks,andwhatthefutureholds.Alongthewaywehavesimplifiedthecomplexitiesofmuchofthisinformationsothatyoumightmorereadily
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graspprinciplesandruleswhichyoucanthenapplyinyourdailylife,whethershopping,attendingfunctionsorsimplyeatingathome.
Thisbookisdividedintothreeparts.PartIhighlightstheprevalence,dangersandimpactoffoodpoisoning,liststhemostcommonfoodpoisoningagentsandhowtheyaffectyou,andlaysdownsomegeneralrulestoprotectyourselfandyourfamily.PartIItakesyouonawalkthroughtheshoppingcentre,withchaptersdealingwithseparateshopssuchasthedelicatessenorfishshop,andpointsoutwhichfoodsareriskier,andwhicharesaferchoices.PartIIIlooksatfoodpoisoningrisksfromtraveldestinations,partiesandpackedlunches,whatyoucandotostoreandpreparefoodmoresafely,whatthefoodindustrydoes,andotherriskstodowithfoodsuchasallergiesandgeneticallyengineeredproducts.
Manyofthelists,tablesandtipsinthisbookarebasedontheassumptionthatcertainfoodshavebeentreatedandhandledequally.Byreturningtobasicprinciplesoffoodscienceitispossibletosuggestthatonefoodisriskierthananother.Thepointmightbecontroversialandcouldbearguedaboutbyexpertsforever.Thisbook,however,iswrittenforconsumerswhowantsomehelpandguidanceindealingwithdifficult,sometimesobscureproblems.Inprovidingthisguidancethewritersare,insomeinstances,statingapersonalopinion.
WehaveincludedmanycasestudiesfromtheUnitedStatesandBritain,aswellasfromAustralia.InsomecasesthebacteriaorviruseswhichfeatureinthoseoverseasstoriesaremoreofaproblemtherethaninAustralia.Yettheyremainrelevanttoallwhotravelwidely.Forexample,ifyou'reoneofthethousandsofAustralianswhohaveembarkedonaUnitedStatesfamilyholiday,itisworthknowingthatyoushouldcheckyourhamburgermincehasbeencookedthoroughlyhamburgershavebeenanongoingsourceoffoodborneillnessintheUnitedStates.SimilarlytheUnitedStateshassufferedsomemajoroutbreaksofillnesstracedtolocalwatersupplies.AgainitisaproblemthatAustraliansarenotnecessarilypreparedfor.
Whenwebeganourresearch,weconsideredwhethertheconcernintheUnitedStatesoversafedrinkingwaterandfruitjuiceswasrelevanttoAustralians.Bythetimewecompletedthisbook,AustralianshadwitnessedthefrenzyarisingfromtheSydneywaterscareandtherecallofNippy'sAussieGoldandOrangeGrovefreshchilledfruitjuicesforSalmonellacontamination.Ahealthconcernmayariseononesideoftheworld,butitshouldnolongercomeasasurprisetoseeitpopupinourownbackyard.
Areyoupreparedtotakeariskoffoodpoisoning?Sometimestheanswerwillbe'Yes',atothertimes'No'.Yourownstateofhealthwillhaveagreatbearingonhowyouanswerthisquestion.Wehavefoundthatmanypeoplewhoworkinthefoodindustryhavesafetytipswhichtheyapplyintheirownlives.Somewillnoteatcustardtarts,forexample,simplypreferringtoremoveawholecategoryoffoodfromtheirordinarydietratherthantakewhatatmosttimeswouldbeaverysmallrisk.Inthisbookwe'llshowyoumanyofthesetips.
Itisimportantfromtheoutsetyouunderstandthatsuchtipsareasimplificationofverycomplexissuesandprocesses.Asocalled'risky'food,provideditispreparedandhandledproperly,mightbequitesafetoeat.Atthesametime,a'safer'foodmightstrikeyoudownwithillnessbecauseitwashandledbyachefwhofailedtowashhishands.
Thereareplentyofcorporationsandadvertiserswhowanttoscareusallaboutthesafetyofourfoodsupplyandthewaywerunourhomekitchens.Werejectthefearcampaign,andtheirnotionthatcommercialantibacterialdisinfectantsarenecessaryinthehome:goodfoodpracticesandsoapandwaterarecompletelyadequate,andhavebeenforcenturies.Withoutbuildinguptherisksor,ontheotherside,playingthemdown,webelievethatconsumersarmedwithgoodinformationwillgetthebestoutoftheirmealsgreaterenjoyment,greatersafetyandbetterhealth.
Wehopethisbookwillhelpyoudevelopapositiveattitudetofoodandmealpreparation.
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PARTIUNDERSTANDINGFOODPOISONING&YOURPROTECTION
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Chapter1We'reAllinThisTogether
Haveyoueversufferedfromfoodpoisoning?Maybeyou'vewokenuparoundthreeo'clockinthemorning,clutchingyourstomachinpain,andcursingtherestaurantwhereyouhaddinner.Sometimesyoudevelopabadfeelingaboutaparticularfoodalmostassoonasyou'veputitinyourmouth.
Minutes,hours,days...foodpoisoningcanbefastorslow.Sometimesyouanticipateit('Idon'tfeelgoodaboutthoseoysters!')anditnevershowsup.Forthisreasonitcanbedifficulttoknowwheretolaytheblame.Wasitlastnight'srestaurantoryesterday'slunchofreheatedleftovers?Canyourightlycalltherestaurantandcomplaintothemanager,orshouldyoubelookinginsteadforaproblemwithinyourownkitchen?
Foodpoisoningisanissueofgreatconcerntoallofus.Maybeyouareaparent,wantingtodowhatisnecessarytoprotectyourchildren.Perhapsyouareabusinesstravellerwhocannotaffordtocomedownsickwhileracingtomeetdeadlinesandenduremeetings.Forsomeofusitisamatterofcaringforfriendsorfamilywhoareinpoorhealthandatriskofseriousillnessfromanyinfectionpeoplewithcompromisedimmunesystems,theelderly,pregnantwomenandbabies.
Themoreyouknowaboutfoodpoisoning,thebetteryourchancesofenjoyingyourtravelsandkeepingyourfamilyindailygoodhealth.
WhatIsFoodPoisoning?
TheWorldHealthOrganisationdefines'foodpoisoning'asanyillnesscausedbyorthoughttoberelatedtotheconsumptionoffoodorwater.Itisaverybroadconcept.Inthisbookwewillusetheterm'foodborneillness'.
Expertssometimesdividefoodborneillnessintodifferentcategorieswhichassistintheiranalysisofwhatisgoingon.Forexample,somemicroorganismsmultiplyinfoodandproduceatoxinwhichpoisonsuswhenweeatitothermicroorganismsmultiplyinsideourbodies,havinggainedaccesswhenfoodordrinkareconsumed(orfingerslicked).
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Noteveryonewhoeatsortakesinaharmfulmicroorganismortoxinwillfallsick.Sometimesthisisbecausethe'dose'thenumberoforganismsorquantityandstrengthofthetoxinisinsufficienttocauseillnesssometimesthepersonhasadegreeofimmunityduetopriorexposuretothemicroorganismsorbecausetheyenjoybetterhealthgenerally.
Apersonwhocarriestheharmfulorganism,yetshowsnosymptoms,mightstillbeablepassitontosomeoneelse,whodoesbecomeill.Wecanbesymptomless('asymptomatic')carriersoffoodbornepathogens.
Whatisitthatmakesussick?
Foodpoisoningisusuallythefaultofbacteriaandother'bad'microorganisms.Wegetsickbecausewehaveconsumedthembyeatingordrinking,orbyputtingobjectsinourmouthsthatarecontaminatedwiththem.
Thefourmostcommonsituationsthatcanresultinanepisodeoffoodborneillnessare:
poorstorageofthefood
inadequatecookingorreheating
crosscontamination:fromonepersonorutensil/surfacetoanother
infectedfoodhandlers.
Onceinsideourbodiestheytravelthroughthestomachandintotheintestines.Mostfoodpoisoningbacteriatargetthecellsofthesmallintestine.Someattachtotheintestinewallsandstarttomultiply,effectivelycolonisingtheareabeforeproducingtheirtoxinsothersreleasethetoxinwithouthavingtocreateacolonyfirst,sometimessimplyfromwithinthefoodmassitselfotherswillpassthroughtheintestinewallsandheadforotherpartsofthebody,forexample,theviruswhichcauseshepatitisAgoestotheliver.Thenwegetsick.
However,thisisonlypartofthestory.Therearemanythingsthatmakeussick,andbacteriaareonlyonetypeofculprit.Therearegoodbacteriaandbadbacteriatherearegoodchemicalsandbadchemicals.Almosteverythingyoucaneatisapoisonifyouswallowtoomuchofitevenvitaminsandotherhealthythingsinourfoodanddrink.Itisusefultoknowthedifferentsourcesofproblemssoyoucanthenunderstandwhichwaytotreatthem,andhowtoprotectyourself.
Whoarethebadguys?
Asyoumightexpect,therearemanythingsbacteriaandviruses,moulds,yeasts,parasitesandchemicalswhichcanleadtothesymptomswecallfoodpoisoning.YouhaveprobablyheardofSalmonella.Therearemorethan2300differentkindsofSalmonellabacteria,butyoudon'tneedtoknowaboutthemall,andnotallofthemwillmakeyousick!Inotherwords,wecanmakeamoremanageablelistoftheproblembacteria,virusesandothermicroorganisms.ThatformsthesubjectofChapter2.
Notalltoxinsthatgiveusfoodpoisoningcomefrommicroorganisms.Therearealsosomeothernaturalpoisonstobeawareof:
Whenpotatoesturngreenincolouritisasignthatthepoison'solanin'hasbeenproduced.
Oxalicacid,foundintheleavesofspinachandrhubarbcan,intheory,leadtokidneydamageasaresultoftheformationofinsolublecalciumoxalatecrystals.
Theseaishometosomeverypowerful,allnaturaltoxins.Thetoxininpufferfishhasbeenknowntokillthepersonwhoeatsit.InJapanthisfearispartofwhatattractsthethrillseekingdiner.Butit'snotjustaconcernfortheJapanese.Pufferfishhasturnedup,accidentally,inafrozenfoodproductsoldinAustralia.Whenthecompanybecameawareofthemixup,theproductwasrecalled.Anotherseafoodpoisonis'ciguatoxin',whichhasalsoledtoafoodrecallin
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Australia.Thistoxinstartsinmarineplantswhicharetheneatenbysmallfishwhich,inturnareeatenbylargerfish.Asitmovesupthefoodchainweseetheconcentrationofthepoisoninlargefishcaughtnearcoralreefs.Theonestobecautiousaboutarelargepredators,suchassnapper,coraltrout,coralcod,Spanishmackerelandredemperor.
Sometoadstoolsandmushroomscanbeverytoxic.AccordingtoarecentradioreportfromRussiaatleastonepersoninthatcountrydieseachdayfromeatingthewrongtypeofmushroom.
ThemostcommoncausesoffoodPoisoning
ThemostcommoncausesoffoodpoisoninginAustralia(indescendingorder)are:CampylobacterSalmonellaHepatitisAShigellaandYersina.IntheUnitedStatestheordergoes:CampylobacterjejuniSalmonellaShigellaCryptosporidiumfollowedbyE.coli0157:H7.AndinBritainthetopfiveare:SalmonellasmallroundstructuredvirusClostridiumperfringensBacilluscereusandfifth,Campylobacter.
Whileallthreenationsfacefoodborneillnessfromallofthese,thereisashiftinemphasisbetweenthoseatthetopofeachlist.(Someofthedifferencesdependontheintensityoffollowupofcasesbypublichealthauthorities,andontheabilityoflaboratoriestodetectfoodillnessagentsatwork.)
WhatAretheSymptoms?
Symptomsoffoodpoisoningmayincludethefollowing:
diarrhoeawatery,maybeevenbloody
nausea
vomiting
dehydration(duetofluidlossfromdiarrhoeaandvomiting)
fever
paininthestomachorabdomen
swellingintheabdomen
dizziness.
Inextremecases,severeillnessordeathcanresultfromcertainfoodbornepathogens.
Don'tbealarmed!Notallfoodpoisoningisfatal.InAustralia,recentkillershavebeen:SalmonellaVibrioparahaemolyticus(cholera)E.coliStaphylococcusaureus.Thisrepresentsonlysixdeathsovera15yearperiod(19801995).Howeverasthisbookwasgoingtopress,sixfatalcasesoflisteriaassociatedwitheatingfruitsaladwerereported.FoodpoisoningisnotabigkillerinAustralia.Ifyoufindyourselfinapoornation,however,theriskbecomesmorereal.IncountrieslikeAustralia,NewZealandandBritainwegrowupwithlittleappreciationoftheriskelsewhereontheplanet.
Havingsaidthat,therisk(althoughsmall)ofalifethreateningattackoffoodpoisoning,remainsrealeveninadevelopednation.Attheendof1998,12peoplediedintheUnitedStatesfromwhatisbelievedtohavebeenpackagedmeattaintedwithListeria.Itwasasingleinstanceofmeatcontamination.Twoyearsearlier,20elderlypeoplediedfromanE.coli0157:H7infectionincentralScotland.Thesenumbersfordevelopedcountriesarerelativelysmallwhenthesizeofthepopulationisconsidered.Itisatragedywhenithappens,butitisnotoften,andfewdie.
ChronicDiarrhoea
Forsomepeopleaboutofdiarrhoeacanlastforweeks.Isfoodordrinktoblame,ordoestheproblemlieelsewhere?Diarrhoeacanbecausedbyfoodpoisoning.AtfaultmaybeparasitessuchasGiardiaandCryptosporidium,viruseslikeNorwalkorRotavirus,orbacteriasuchasCampylobacter,E.coli,
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Listeria,SalmonellaorShigella.Buttherearemanyotherreasonsforchronicdiarrhoeawhichshouldnotbeignored,andforwhichmedicaltreatmentshouldbesought,including:
theuseofantibiotics
cancer,andcancertreatmentdrugs
diabetes
colitis
foodallergies
somefoodadditivesorcomponents(e.g.fructose,sorbitolandothers)
medicationsfortreatinghighbloodpressure
Crohn'sdisease
thyroidandendocrinediseases
previoussurgeryorradiationoftheabdomenorgastrointestinaltract.
HowBigIstheProblem?
Foodpoisoningfiguresareveryuncertain.InMay1999,theAustraliaNewZealandFoodAuthority(ANZFA)releasedareportestimatingthat11,500Australianssufferedfromfoodpoisoningeachday,costingthenationmorethan$2.6billionayear.Accordingtotheresearch,absenteeismfromworkduetofoodpoisoningcostAustraliamorethan$370millionin199697alone.Whilehighlightingjusthowsafethefoodsupplywas,ANZFAsaidAustraliansfacea1in5000chanceofgettingfoodpoisoningfromameal,outofanestimated20billionmealseateninoneyear.Someauthoritiesbelievefoodpoisoningisontheincrease.
In1995theUSDepartmentofAgriculture'sFoodSafetyBranchattemptedtoestimatelossestotheUScommunityfromfoodborneillness.Includingmedicalcostsandlostproductivity,itcameupwitharangeofUS$5.69.4billionannually.Fouryearslater,inearly1999,theUSDepartmentofAgriculture'sUndersecretaryforFoodSafetyplacedtherangemuchhigher,atbetweenUS$6.637billionannually.
TheUSCentersforDiseaseControlandPrevention(CDC)reportedthefindingsoftheFoodNetsurveillanceprojectinApril1998:'Theoverallburdenofdiarrhealdiseaseisgreat.FoodNetestimatesthat360millioncasesofdiarrhealillnessoccurperyear,resultinginapproximately28millionmedicalconsultations.'TheCDCestimated,fromitsresearch,thatapproximately8millioncasesoffoodbornebacterialinfectionsoccurredin1997intheUnitedStates.
AstudyofreportedcasesoffoodrelatedillnessinEnglandandWalesfrom1992to1994identified1594distinctoutbreaks,affectingatleastthe34,158peoplewhoreportedtoadoctororhospital.Ofthese,2percentwereadmittedtohospital,and55peopledied.Overthethreeyearsoftheperiodunderreview,halfthecaseswerefoodborne,andafurther40percentwerepassedbypersontopersoncontact.
Thereportedcausesalsovary.AccordingtotheUnitedStates'CDC,therearemorethan250differentdiseaseswhichcanbecausedbycontaminatedfoodordrink.Somearenolongerthebigproblemstheyoncewere(suchasbotulism)whilenotifiedcasesofcertainothersmaybeontheincreaseoverthelastdecadeorso(forexample,reportedinfectionsduetoListeria).Itisnotastaticpicturebutamoveablefeastofsorts:sometimesthefiguresgoup,sometimesdown.
Morethan39,000casesofsalmonellosis(illnessduetoSalmonella)weredocumentedbytheCDCin1996alone.However,thisisjustthetipoftheiceberg.Expertsestimatethat,intheUnitedStates,thetruenumberofcasesfallsintherange696,000to3.8millioneachyear.This,ofcourse,isavastrangeofpossiblecases,servingtoindicatejusthowinexactisourknowledgeofthefullimpactoffoodpoisoningandfoodintoxicationinourcommunities.Evenallowingforthosestatistical
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shortcomings,thenumbersarehuge.
Inpracticefewpeoplewhocomedownwithfoodborneillnessseekmedicalattentionorotherwisearerecordedasanofficialstatistic.Thatiswhythehealthauthoritiestalkaboutwideestimatesratherthanhardnumbers.Peoplesufferathome,missingtheodddayofschoolorwork,perhapsblamingtheflu(manyofthesymptomsaresimilar)orshruggingtheirshouldersandgettingonwithlife.
FoodpoisoningisrarelyfatalinAustralia.InasubstantialreviewofthesituationinAustraliafortheyears1980to1995,performedbyScottCrerarandothersandpublishedintheMedicalJournalofAustralia,128outbreaksoffoodbornediseasewereidentified.Almost6000peoplewereaffectedbytheseoutbreaks,butonly185werehospitalised,andonlysixpeopledied.
ItisonethingtoknowthatnotmanyAustraliansdieorendupinhospitalthankstofoodborneillnesses.Thedramaticcasesarecomparativelyfew,giventhesizeofthepopulationandthenumberofmeals,foodsandbeveragesweconsume.Butwhataboutthelessdramaticinstances?Howoftendoesoneofyourfamilymemberscomedownwiththesymptomsoffoodpoisoningorsomefoodrelatedillnesssuchasmilddiarrhoea,nauseaorpaininthebelly?Ifweknewtheanswertothisquestionwewouldhaveamuchbetterunderstandingabouttherealimpactandcosttothecommunityoffoodborneillness.
ResearchiscurrentlyunderwayinboththeUnitedStatesandBritaintofindthetrueincidenceoffoodborneillnessfortheirpopulations.InfactAustralianscientistshelpeddesignthesurveyscurrentlybeingusedintheUSresearch.InitiallyitseemedthatAustraliawouldnotbecarryingoutitsownresearch.However,latein1998thefirstSentinelSurveillanceProjectgotunderwayinAustraliatofindouthowmanyofussufferfromfoodpoisoningandotherfoodborneillness,andhowoftenitstrikes.TakingplaceintheHunterregionofNewSouthWales,theprojectbytheHunterPublicHealthUnitoftheNewSouthWalesGovernment,involvessurveyinganareawithapopulationof500,000people.Inparticulartheresearcherswillbelookingforevidenceofactionoftwoofthemostcommonharmfulfoodbacteria:SalmonellaandCampylobacter.Thefirstresultsareexpectedbytheendof1999.
AnearlierpilotstudytookplaceinCanberra.Forthatstudy,telephonesurveyswereundertakeninhouseholdsthroughoutthecity,questioningthepersonwhowasthefoodhandlerattheirhome.Resultsindicatedthatupto60percentofdiarrhoealillnesscouldbetheresultofpoorfoodhandlingpracticesathome.
ResearchfromtheUnitedStatesconfirmsoneimportantfindingofthisCanberrastudy:ordinaryhouseholdersdon'tappeartoblametheirownfoodhandlingpractices,orrecognisethehazardtheytrulycanbe.
FoodborneillnessalsoappearstobeontheincreaseintheUnitedStateswheretherearearound400to500outbreaksreportedannually.Inpartthisispossiblyduetobetterrecordingandmorethoroughresearch,butwecan'tdiscountthepossibilitythatmorepeoplearesimplygettingsickermoreoften.Importantcontributingfactorsmaybethewayswerunourkitchens,changesinthefoodsweeat,andtrendsinhowandwhereweeatourmeals.Wewillconsiderthesefactorslater.
Wheredoesillnessstrikemost?
Itiscommonforthefoodindustrytolaytheblameforfoodpoisoningonpoorhygienepracticesinthehome.YetinAustralia,ANZFAconsidersthat80percentoffoodborneillnessoccursoutsidethehome.Stillmuchfoodrelatedillnessispreventable.TheBritishresearchersnoted:
Mostoftheoutbreaksreportedandtheassociatedmorbidityandmortalitycouldhavebeenpreventedbyfollowingstandardfoodhygienepractices,implementinginfectioncontrolpolicies,andensuringthatfoodenteringkitchenswasofthehighestmicrobiologicalqualitypossible.
AreviewofinstancesoffoodrelatedillnessinEnglandandWalesfrom1992to1994investigated1594generaloutbreaks.Thetable
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NUMBEROFOUTBREAKSOFFOODBORNEILLNESSFROMVARIOUSLOCATIONS
Place Mainlyfoodborne
Mainlypersontoperson
Nursinghomesandsimilarinstitutions
59 199
Hospital 19 156
Restaurant 170 2
Hotel 75 25
Home 101 6
Schools/colleges 30 64
SourceSurveyofEnglandandWales,199294,USCentersforDiseaseControlandPrevention,CDRReview,29March1996.
aboveshowsthemostcommon'settings'orplaceswheretheillnesswaspickedup.
Arehomessaferthaneatingout?There'salotofdifference.Takenasawhole,eatingoutatrestaurants,cafes,canteens,pubsandhotelsaccountedfor27percentofoutbreaksnursinghomesandthelikeadded22percentandhospitals15percent.Theprivatehomeonlyaccountedfor9percentofoutbreaks.
Alsointerestingisjusthowoftenafunctionorpartywastheoccasionwhenthebaddeedtookplace.Thevastmajority(88percent)ofoutbreaksconnectedwithprivatehomesoccurredatweddingreceptions,dinnerparties,engagementandbirthdayparties,barbecuesandothergroupmeals.Justoverhalftheoutbreakstrackeddowntocommercialpremises(suchasrestaurants)werealsofunctions,notnormalpublictrading.
Clearlythefunction,whetherataperson'shomeorinacommercialsetting,isanoccasioncallingforgreatercarebycaterersandconsumersalike.Expertshavesaidthatthepracticesandfacilitiesfoundinthehomearenotappropriateforcateringforlargenumbersofpeople.Inmanyoutbreaksthefoodwaspreparedatsomeone'shomeandthentransportedtotheplaceoftheparty(acommunityhall,forinstance).Asyoureadthroughthisbook(particularlyChapter19)youwillseethelengthstowhichcommercialpremisesmustgoinordertoprovideanacceptableleveloffoodsafety.Itisbeyondwhatmostofuswouldbepreparedtodoinourownhomes.
TheFoodTheyCallBack
Haveyoueverboughtafoodproductwhichwaslaterthesubjectofafoodrecallcampaign?Usuallytherecallisbroughttotheattentionofthepublicbyaspecialnoticeinthenewspaper,orasignmightbedisplayedattheentrancetothesupermarket.Intheworstcases,wherenumbersofpeoplehavebecomesickaftereatingordrinkingtheproduct,you'llhearabouttheproblemontheradioortelevision.
Foodrecallsonlydealwithasmallnumberofthefoodsandoccasionswhereconsumerhealthisplacedinperil.Nevertheless,theyarewelldocumented,andthathelpsuslearnusefulinformationaboutwhereandhowfoodbornedangersarise.Forastart,foodrecallsarenottobedismissedassomethingthatonlyhappensto'bad'foodmanufacturers.Someofthefoodswhichhavebeensubjecttoaproductrecallcampaignsincethemid1990sincludewellknownbrandnames.
ThelistandquotesonthenextpagearefromthelistofpublicrecallnotificationscompiledbytheCommonwealthDepartmentofIndustryScienceandTourism(ConsumerAffairsDivision).Asfarasweareaware,allthoserecallslistedabovewereinstancesofthemanufacturerordistributortakingpreventiveactiontolookaftertheircustomerswherecontaminationoraforeignobjectwasintroduced(orwassuspectedofbeingintroduced)tothefoodaccidentally.
Thesecondpointtonoteisthatnofoodgrouporpackagingstyleseemsimmune:fromdairytomeatandfishvegetablestosnackfoodscans,glassjarsandpacketfoods.
Thesedaysitseemstherearealotoffood
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FOODRECALLSINAUSTRALIA
Attikifettacheese 'Listeriamonocytogenescontamination'
BiLochoccoatedicecreams 'MaybecontaminatedwithListeria'
CadburySchweppesblackforestfruitandnutchocolateblocks
'Consumerswithanallergytonutsmayhaveanallergicreaction'
ClassicandJosephineLAGourmetvariousdips
'MaybecontaminatedwithListeriamonocytogenes'
Farmland(Coles),BiLoandAlpinemudcakes
'Theremaybeanomissionofeggsbeinglistedoningredientlabelling'
DonLatvianliverspreadanddelisupremekabana
'ContaminatedwithSalmonellabacteria'
GoldenCirclecannedpeas 'Doesnotcontainpackingliquid(syrup)thereforecanshavenotreceivedthescheduledthermalprocess'
Heinzappleyoghurtdessertbabyfood 'Maycontainglassfragmentsinthejars'
Bird(PontiacTradingCompany)peanutsnack
'Highleveloffungalcontamination'
SalmonKingsmokedsalmon 'MaybecontaminatedwithListeria'
Santoscrushednutsandcrushedmixednuts
'PossibleSalmonellacontamination'
Plumrose(Simplot)cannedchicken,turkey,delihamandlegham
'Damagetocansmayallowairpenetrationresultinginproductdeteriorationandpotentialhealthrisk'
Smith's'Twisties'(cheeseandchicken) 'Maycontainfragmentsoffinewire'
Streets'GraveRobber'icecream 'Confectionarypiecescontainedintheicecreamarehighinleadandcadmium'
Giardiniera(Triou)pickledvegetables 'Possiblechemicalcontaminationduringmanufacture(formaldehyde)'
recallcampaigns.Aretheremorethanever,orarewejustmoreawareofthem?ThenumbersofrecallsinAustraliaforfoodandbeveragesfortheyears198697areshownonpage15.Inthelate1980sthenumbershoveredaroundfivetoseveneachyear.Thisrepresentedroughly2or3percentofallproductrecallsincludingcarsandotherhouseholdproductsfortheyear.
Intheearly1990sthenumbersandproportionsjumpedtoanewlevel.Proportionally,foodrecallswereincreasingaspartofthetotalmixofconsumerproductrecalls.Anotherleap,inthemid1990s,sawfood/beveragerecallshitnewheights:52recallsintheoneyear,representing15percentofallconsumerproductrecallcampaigns.Thereforewecansay:yes,thenumbersoffoodandbeveragerecallshavebeenincreasingandyes,foodandbeveragerecallsrepresentanincreasingproportionofallconsumerproductrecalls.
Thisdoesn'tnecessarilymeanthattherearemoreproblemsthaneverwiththesafetyofourfoodsupply.Itmightsimplybeacasethatmorecompaniesarecomingforward,or
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beingcaught,whentheyhaveaproblemwiththeirfoodandbeverageproducts.Oritmightbeacasewhereabitofbothisgoingon.
IntheUnitedStatesin1998,bycomparison,therewere39foodrelatedproductrecalls.Surprisinglyalmostallconcernedmeat.Ofthese,thelargestsingleproblemproductwasmincedmeat(forhamburgerpattiesandotherwise),with13occasions.Hamandsausagesfacedfourrecallseachchickenproductssix(threeofwhichwereduetometalobjectsturningupinthefood)andFrankfurtsthree.Aroundhalfofallrecallswereforbacterialcontamination,whileanotherseveninvolvedbitsofmetal.
InAustralia,too,asurprisingnumberofrecallsaretodowithforeignobjectsappearinginthefoodsordrinks.InJuly1995,foodrecallcampaignswerelaunchedovermetalshavings(somepacksofKellogg's'RiceBubbles'and'CocoPops'),glassfragments(glassjarsofAyamseafoodandchickencurrypaste),andstainlesssteelwirefromamanufacturingsieveincansofinfantformula('Infasoy').
Many'foreignobject'recallsareduetofoodcontaminationbybrokenpartsofthemanufacturingassemblyline:anutfallsoffaboltinthemachine,awiresievewearsoutandfragments,apieceofelectricalwirefallsout.Othersaremoreunusual:acapsuleofantibioticAmpicillinTrihydratefounditswayintosomeseedlessdateswirebristlesfromabrushendedupinsomewholemealfruitbarsandcausticcleaningsolutioncontaminatedmilk.
Anothertypeofforeignobjectcontaminationwhichalsomightleadtoarecallcampaigniswherethewrongfoodgetsintothepackage.Whiletheremightbenothingwrongorunhealthyaboutthe'foreignfood'itself,thelabellingoftheproductisnowincorrectand,forsomemembersofthecommunity,theremightbeahealthissue.Allergiesareaclassicexample:peanutsinchocolatebars,hoummosandricecrackersgluteninapackofsausageslabelled'glutenfree'.Youcanunderstandthepotentialhealthrisksthesetypesofmessupscanbringabout.
Foreignobjectsrepresentalargeproportionofallfoodandbeveragerecalls:around45percent.However,unlikefoodrecallsduetobacterialcontamination,itisgenerallythecasethatonlyafewpacksmaybeonlyonehavebeenfoundtobeaffected.Bycomparison,microorganismsrepresentthelargestthreattopopulationsofpeople.
CanYouTellIfFoodIs'Off'?
Foodrecallsareonlythetipoftheiceberg.Ifthefoodworldisfullofdangersthevastmajorityofwhich,wehastentoreassureyou,willpassyoubyitisfairtoask:CanIpickbadfoodfromgoodfood?CanItelliffoodis'off'or'spoiled'?
NumberofFoodRecallsinAustraliaSourceCommonwealthDepartmentofIndustry
ScienceandTourism(ConsumerAffairsDivision)
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Insomecasesyoucancertainlyrelyonyourwhatyoursensestellyou.Therearevisualsignsthatthefoodhasgone,orisgoing,'off',spoiledorstale.
Haveyoueverseen:
breadwithmouldonit
greenpatchesonpotatoes
blackspotsonfruit
fishwithdulleyes?
Therearealsosomeoccasionswhenyoucansmellthatafoodisspoiling.Haveyoueversmelled:
a'wetdog'odourfromwine
rottenegggas
sourmilk
oldmeat?
Sometimesit'syoursenseoftouchwhichgivestheclue.Haveyoueverfelt:
vegetables,suchaszucchini,whichhavegonesoftandsquishy
slimyham?
Ifyoulistenedtowhatyourmotherorgrandmothertoldyou,youwouldknowmanyofthesignsthatfoodiseitherspoilingor,alternatively,isinpeakcondition.Thisisimportantfolkknowledgethathashelpedussurvivefromonegenerationtothenext.
Butnotallfoodpoisoningissoeasilydetected.Inmanycasesthetruenatureofthefoodordrinkcanonlybeknownaftertestinginalaboratory.Foodpoisoningmightnotaffectthelook,smell,feeloreventasteofthefoodordrink.
Useyoursenses,butdon'trelyontheminallcircumstances.
Whynot?Thereisabasicconfusionhere:themicroorganismswhichbreakfood
WAITER,THERE'SATACKINMYHAMBURGER!
Whileeatingahamburgeratthebeachoneday,oneoftheauthorstookabiteandwassurprisedtofindathumbtackstickingintohismouth.
Howdidthetackgetthere?Maybetheshopusedtackstopinupthemealordersabovethefoodpreparationareaperhapsithadbegunitsvoyageinthemincedmeatfromthebutcher'sshop.Sowhoshouldgettheblame?Therearemanyopportunitiesforforeignobjectstofindtheirwayintofood.
Sometimesthethinggetstherebyaccidentandsometimesitisfromdeliberatetampering.
downandleadtospoilingarenotusuallythesameoneswhichpoisonpeople.(Asmentionedearlier,notallmicroorganismsarebadforus.)However,thesamefactorswhichallowfoodtoharmlesslyspoilmightalsoprovideanopportunityforpathogenstocontaminatethefoodandmultiply.Inanyevent,itisnotagoodideatoeatfoodwhichhasspoiled.
Inmanycasestherearenoobvioussignsofbacteriaandvirusesatworkinfoodanddrink,soyoucannotalwaysrelyonwhatyoursensesaretellingyou.However,insomecasesthechangesshowthemselvesinonewayoranother.
ForeignBodies
Youshouldalsowatchforforeignbodies,suchaswormsorinsectsinrice,flouranddriedfoods.Thesedonotleadtofoodspoilageinthesenseofmicroorganismactivity,buttheycanadverselyaffectthequalityandpalatabilityoffood.
Aforeignobjectcancauseagreatdealofphysicalandemotionaltrauma.Apoison,ofcourse,mayevenbefatalifswallowed.Morecommonly,however,wehearoffragmentsofbrokenglassorwire:awiresievemaywear
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throughandfallapart,aglassjarmightshatterunderstress.
Wheredoforeignobjectscomefrom?Thereareasmanysourcesasthereareobjects:
stones,dirtandsoilfromthefields
timberfrompalletsandboxesusedtocarttheproduce
glassandmetalfromprocessingmachinery
glassfromlightbulbsandlightfittings
asbestos,fibreglassandotherbuildingmaterials
bonefragmentswhichhavesurvivedthefoodprocessingintact
plasticfrompackaging
jewellerypins,birosandotherpersonaleffectslostbystaff.
Forconsumers,thesethingscanleadtocuts,choking,brokenteeth,infection(resultingfromcuts),aswellasillness(fromdirtbornebacteria).
HowDoYouProtectYourself?
Ifwecannotgenerallypickapotentiallyharmfulfoodusingoursenses,howdoweprotectourselves?Unfortunately,therecanbeno100percentguaranteesofsafetyunlessyouhavealaboratorytestallyourfoodbeforeyouconsumeit!Foodsafetyawarenessisamixof:
whatcausesfoodpoisoning
howwegetit
therawmaterialsinthefood
whatyoursensestellyou
whereyouboughtthefood
howtheshopshadstoredthefoodbeforeyougotit
howthosewhodeliveredthefoodtotheshopshadhandledit
howyouhavebroughtthefoodhome
howyoustoredthefood
howyoupreparedorcookedthefood.
Wewilldiscusstheseissuesinthechaptersthroughouttherestofthisbook.
USEYOURCOMMONSENSES
Sense Signs
Sight(colourchange) Greensporesofpenicilliumoncheeseorbluewhiskersonbreadwhitewhiskersonzucchinigreenpatchesonpotatoesdarkspotsonmeatblackspotsonbananas,applesandtomatoessilverycolouronmeat.
Sight(damagedpackaging)
Canswhicharedented,rustyorhaveswollenendsmilkandotherdrinkcontainerswhichhaveblownoutopenorleakingcontainers.
Smell Foulodoursfromgasproductionandbacterialbreakdownsoursmellingmilkacrid,ammoniaor'wetcardboard'smells.
Touch Sticky,viscous,'ropy',slippery,slimy(forexample,lettucemeat,ham),hollow,softandsquishy(vegetablesandfruit).
Taste Sour,unpleasant,overpoweringnothowitusuallytastes.
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Summary.
Checkthenewspapersandwatchthetelevisionnewsregularlysothatyouareawareofanyfoodrecallsorotherhealthrisksinyourcommunity.
Rememberthatfoodsafetyproblemsdon'tjuststrikesmallmanufacturerssometimesthebigbrandshaveproblemstoo.
Useyoursensesandexperiencetohelpdetectwhetherfoodis'off'.However,beawarethatyoursenseswon'thelpyoudetectallharmfulchangestofood.
Justbecauseafoodhasgone'off'orspoileddoesn'tautomaticallymeanifyoueatityouwillgetsick.
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Chapter2KnowYourEnemy!
Ifwecannotalwaystrustoursensesandexperiencetowarnusoffoodswhichmayharmus,whatcanwedotoimprovetheposition?.Thepositivemessageofthisbookisthatyoucanreduceyourriskoffoodpoisoningbyknowingalittleaboutthewaythepathogensworkandthefoodstheyliketocontaminate.
Thischapterintroducesthebadguysthebacteria,viruses,toxins,yeasts,mouldsandnaturalpoisonswhichgiveourfoodsupplysomuchtrouble.Alongthewayyouwillpickuptipsthatwillhelpyouindailylivingandeating.
Bacteria
Bacteriaaretinylivingthings:microorganisms.Theyarebasic,singlecellcreatures,andaresosmallaroundonemillionthofametreindiameterthatyoucannotseethemwiththenakedeye.Theycomeinavarietyofshapes.Themostcommonofwhichlookabitlikearod('bacillus'),comma('vibrio'),ball('coccus')orspiral('spirillum').Somehavemanylittlelegs('flagella')whichhelpthemmovearoundiftheyareinaliquidofsomekind,butmostbacteriacan'tmovethemselves.Theygetaroundthankstothewindorbyhitchingarideonpeople,animalsandinsects,orinfood.
Asawayofgettingtoknowbacteriabetter,let'stakeacloserlookatoneofthebetterknownones:Salmonella.IntheUnitedStates,Salmonellaisoneofthemostfrequentlyreportedcauseoffoodborneillness.TherearemanydifferenttypesofSalmonella,buttwo(called'serotypes')accountforabouthalfofallcasesofsalmonellosis:SalmonellaenteritidisandSalmonellatyphimurium.Salmonellalivesintheintestinesofwarmbloodedanimalsandinsects,andtheirfaecescanalsocontainSalmonella.Humanscanbecarriers,sometimesshowingnoilleffects,butabletopassSalmonellaontoothers.AnimalswhichharbourSalmonellaincludechickensandcattlethepestswhichinvadeourkitchens,suchascockroaches,flies,ratsandmiceaswellasthefamilydogsandcats.
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InfectionwithSalmonellacanresultinlongtermillness(suchasreactivearthritis)andsepticaemia.Insomepeople,particularlytheelderly,Salmonellainfectioncanbefatal.AfewwilldevelopReiter'ssyndrome.Thisillness,whichhassymptomsincludingeyeirritation,jointpainandpainfulurination,cancontinueformonths,evenyears,andmayleadtoterriblearthritis.
FoodswhichhaveaparticularconnectionwithSalmonellainclude:meat,eggs,icecream,cheese,milk(raworpasteurised),pate,hamanddrinkingwater.TherearethreemainwaysinwhichSalmonellamakesitswayintoourbodies:
directcontaminationfromanimalfaeces
contaminationfrompeoplewhodon'twashcarefullyaftergoingtothetoilet
crosscontaminationfromrawfoodstocookedorotherwisecleanfoods.
Whenanimalsareslaughteredforfood,theSalmonellapresentintheirintestinescan,throughcontact,contaminateotherpartsoftheanimalcarcase,includingthebitspeoplewilleat.Animalfaecesmaycovereggsfromchickens,ducksandthelike,andmicroorganismsinthefaecescanbeabsorbedthroughtheeggshelltocontaminatetheeggitself.Duringthemilkingprocessacow'sfaecescancomeincontactwiththemilkandcontaminateit.Inplainlanguage,whatwe'retalkingabouthereissomesortofpathwaybetweenSalmonellainananimal'sintestineandcontactwithrawfoods.
Thesecondpathwayissimilar:itistheproblemoftracesofhumanfaecesgettingontoaperson'shands,usuallyatthetoilet,andhandlingkitchenutensilsorfood.
ThethirdrouteforSalmonellatoaffectfoodistopassfromacontaminatedrawfooduncookedmeatormilktootherwise'clean'food,suchassaladorvegetables.Thistypicallyhappensifthecookusesthesamechoppingboardforrawmeatandthevegetables,orthesameknifesandutensils.Thisisthereasonwhyitisrecommendedyoukeepandusedifferentchoppingboardsforrawmeat,cookedmeat,andvegetablesandsalad.Alternatively(butitisharderwork)youcancleanandsanitisetheboardbeforeitisusedagain.
ReproducingTrouble
Bacteriareallybecomeaproblemwhentheyreproduce,andthiscanhappenveryquicklyinfood.Initiallythereisa'lag'stagewhenthebacteriagetusedtothenewfoodtheyfindthemselvesin.Thisprocesscouldtaketwoorthreedays,oraslittleasacoupleofhours.Then,onceadaptedtotheplace,andundertherightconditionsoftemperatureandlocation,eachcelldividestoformtwocellsevery20minutesorso.Thismeansthatifyoustartwith,say,10,000bacteria,itwilltakelessthantwohoursand20minutes(plusthelagperiod)toreachmorethanonemillionbacteria.Therearelargevariationsinthenumberofmicroorganismsnecessarytocausefoodpoisoning.ResearchrevealsthatsomemicroorganismscancauseharminverysmallnumbersSalmonellaandShigella,forexample.TherearedocumentedoutbreakswheretestsshowedonlyoneSalmonellaorganismpergramoftheaffectedfood.
Timeisakeyissueinprotectingyourselffromfoodpoisoning.Ingeneralittakesbetweenfourandsixhoursforbacteriatoreachsufficientnumberstomakeapersonill.Largernumbersmeanthereisagreaterlikelihoodthatenoughwillsurvivetobeeatenitalsomeanstheincubationperiodcanbeshorter.However,thelagstagecouldextend
TIPKeepfoodsoutofthetemperature'dangerzone'ofbetween5and60C(40140F).
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formanyhoursordaysafterthefoodfirstbecomesinfectedwiththebacteria.Itwon'talwaysbeaquickprocess.
Secondly,theconditionsunderwhichthebacteriafindthemselvesarealsovital:theywilldivideandgrowmoreslowlyiftheconditionsareunfavourable.Ifyouknowwhatmakestheconditionsfavourableyou'reonthewaytoknowinghowtomakelifehardorimpossibleformanytypesoffoodpoisoningmicroorganisms.
Idealconditionsforbacteriagrowthare:
atemperaturerangeof560C(40140F).Thepaceofbacterialgrowthreallypicksuparound3032C(8687F).
anenvironmentwhichismildlyacidicorneutral(measuredasapHof4.5to7).Alkalineorveryacidicfoodsinhibitmostbacterialgrowth.Moulds,however,canbequitehappyinveryacidicfoodslikefruitjuice.
plentyofnutrientsforthebacteria.Bacteria,aslivingorganisms,needtheirownfoodtosurvive.Clearlythen,theycaneitherstarveorthriveaccordingtothenutrientsavailableintheirlocation.Bacteriapreferfoodscontaininglotsofprotein:likemeat,dairyproductsandeggs.Deprivethemofproteinandtheyfindthegoingtough.
moistratherthandryconditions.Youdon'tusuallyfindlargenumbersofbacteriagrowinginhouseholdfoodslikeflourorcustardpowderwhilesittinginthecupboard.However,onceyoumakeupthecustardorpowderedmilk,itprovidesawonderfulhavenforbacteriatogrow.Moisturecanbefoundeitherinthefooditselforintheplacewherethefoodislocated(thekitchen,pantryorcarboot).Anatmosphereofhighhumiditypromotesbacterialgrowthdryconditionsslowitdown.
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air,orlackofit,Somebacterianeedoxygen('aerobic'bacteria),othersprefertoavoidit('anaerobic'bacteria),whileathirdtype('facultative'bacteria)doesn'tmindwhetherthere'soxygenornot.
BetweenHotandCold
Oneofourbesttoolsforfightingfoodbornediseaseiscontrolovertemperature.Microorganismsshutdownwhenitistoocoldandarekilledwhenitgetstoohot.Whiletherearesomeexceptionstothisrule,youwillgreatlyimproveyoursafetyifyoukeepyourfoodatsafetemperatures.Keepfoodsoutofthetemperature'dangerzone'between560C(40140F).Bacteriapositivelythriveataroundhumanbodytemperature,andonhotsummerdays.
BacterialToxins
Noteverycauseoffoodpoisoningisalive.Thegreatexceptionsarevariouspoisonsortoxinsproducedbybacteria.Thebacteriathemselvesmightcomeandgo,living,reproducing,dyingorfreezingintoinaction.Butthetoxinstheyreleasepaynoheedtothevariousconditionswhichmightstopamicroorganismdeadinitstracks.
Whathappensisthis:bacteriagrowinsideafood.Atacertainpointthebacteriareleaseatoxin.Somebacteriareleasetheirtoxinintothegutafterthefoodhasbeeneaten,whilesomedothisbefore.Withthesebacteriaitisthetoxinthatmakesthepersonsick,notstrictlythebacteria.Butthebacteriaareneverthelessdangerousforhavingthistoxicability.
SomeofthebacteriawhichproducedangeroustoxinsincludeBacilluscereus,Clostridiumperfringens,Escherichiacoli(E.coli)andStaphylococcusaureus.Somemouldsproducepoisonsknownas'mycotoxins'.Thesecanbefoundinmanytypesofgrainsandnuts,includingpeanuts,maizeandwheat.Suchmycotoxinscancausecancerorotherseriousillnessinhumansifcontaminatedfoodsareeatenoveraperiodoftime.
THEACIDTEST
Microorganismsalsodonotlikebeinginfoodwhichiseitherstronglyacidicorstronglyalkaline.Theypreferfoodswhicharemildlyacidicorneutral.AcidityismeasuredbythepHlevelonascalefrom0to14.
IfyouownandmaintainaswimmingpoolyouwillbefamiliarwiththeneedtokeepthepHintherightrange,wherethewaterisclean.OncethepHmovesoutofthatrangeitdoesnottakelong,duringthesummerheat,foralgaetogrow,turningthewatergreenand,eventually,almostblackincolour.Itissomethingsimilarforbacteria.
Oneofthewayswetryandcontrolthegrowthofmicroorganismsisbymanipulatingtheacid/alkalicharacteristicsoffood.Forexample,jamsandmostpreservesareacidic.
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AEROMONASSPP.
Whatisit? Bacteriawhichproducestoxinsoncethefoodhasbeeneaten.
Signsandsymptoms: Diarrhoea,abdominalpain,dehydration.
Timetosicknessafterconsuming. 648hours.
Illnesslasts: 17days
Favouritefoods: Seafood,shellfishandrawfoodsofanimalorigin.
Howdiditgetthere? Contaminatedwater,commonlyfromsinksanddrains.
Protectionstrategy: Cookingreadilykillsthesebacteria.
BACILLUSCEREUS
Whatisit? Abacteriumwhichcanproduceenterotoxins(toxinsabsorbedintheintestine).
Signsandsymptoms: Diarrhoea,abdominalpain,nausea,vomiting,sometimesfever.
Timetosicknessafterconsuming: 816hoursforthe'diarrhoeal'toxinand16hoursforthe'vomiting'toxin.
Illnesslasts: 1214hours(heatunstabletoxin)624hours(heatstabletoxin).
Favouritefoods: Cerealslikecorn,previouslycookedrice,pasta,potatoes,sauces,puddings,cookedvegetables,vegetablesprouts(forexample,mungbean),meat,meatloaf,icecream,freshorpowderedmilk,custard,coldsoups,puddings,commercialbattermixes,spices,sauces.
Howdiditgetthere? Foodborne,soil,airandwater.
Protectionstrategy: Keepfoodsoutofthetemperaturedangerzone.
CAMPYLOBACTERJEJUNI
Whatisit? Abacteriumwhichcanproduceatoxin.
Signsandsymptoms: Diarrhoea,vomiting,fever,tirednessandabdominalpain.
Timetosicknessafterconsuming: 25daysormore.
Illnesslasts: Lessthan7days.
Favouritefoods: Rawandundercookedchicken/poultryandhamburgermince,cakeicing,water,processedturkey,rawclams,eggs.
Howdiditgetthere? Faecalcontaminationandpoorhandlingcontaminatedwater.
Protectionstrategy: Cookingandprocessingtechniquessuchassalting,acidandheat.
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CLOSTRIDIUMBOTULINUM
Whatisit? Abacteriumwhichcanproduceatoxin.
Signsandsymptoms: Weakness,dizziness,extremethirst,doublevision,vocalcordparalysis(can'tspeak),paralysisofdigestivesystem,heartandlungs,uncontrollableconvulsions,tetanuslikesymptoms.Canleadtodeath.
Timetosicknessafterconsuming: 1236hours.
Illnesslasts: Severalmonths.
Favouritefoods: Homebottledvegetablesandfruitslowacidornonacidiccannedfoodssuchastunafermentedfoodsmushroomssoupandsmallgoodssuchascannedmeatvegetablesfishandsalamisalmoneggsgarlicinoilbakedpotatoesvacuumpackedfoodslikelotusrootssmokedfish.
Howdiditgetthere? Fromsoil,dust,waterandair,intestinaltract.
Protectionstrategy: Boiling.Adequateheatingofcansandcontents(100Cor212Fforsevenhours)fixesmostcases,althoughsporesrequirelongerheating.Commercially,acidityisatoolusedtocontrolitasthebacteriadoesnotgrowwherethepHisbelow4.6.Commercialcanneriesalsousehighertemperaturesandshortertimes(forexample,at121Cor250Ffor15minutes)toensurethatsporesaredestroyed.
CLOSTRIDIUMPERFRINGENS
Whatisit? Bacteriawhichproducesporeswhich,upongermination,produceatoxinintheintestine.
Signsandsymptoms: Diarrhoea,stomachcramps,headachevomitingisrare.
Timetosicknessafterconsuming: 624hours
Illnesslasts: 1224hours.
Favouritefoods: Largepiecesofmeatsuchasporkandrolledroasts,casserolesandmeatgravies.
Howdiditgetthere? Anaturalcontaminantofmeatandfoundinsoil,dust,waterandsewage.
Protectionstrategy: Cookyourfoodinsmallerbatches,ensuringthefoodisheatedthoroughly.Rapidcooling:donotleaveleftoverstocoolslowly.Putleftoversinthefridgeorfreezerinsmallservessotheycoolmorerapidly.
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ESCHERICHIACOLI(E.COLI)
Whatisit? Bacteriacapableofcausingfoodborneillnessbyarangeofmechanisms.
Signsandsymptoms: Diarrhoea(maybewaterythenbloody),dehydration,headache,abdominalcrampsandpaincanleadtodeath.
Timetosicknessafterconsuming: 38days.
Illnesslasts: Severaldaystomanyweeks,dependingoncomplications.
Favouritefoods: Meats(particularlybeefbutalsochicken),dairyfoodslikemilkandsoftcheeses(particularlyifunpasteurised),mincedmeat,fermentedsalamisandsausages.
Howdiditgetthere? Crosscontaminationattheabattoirorathomenotwashinghandsaftergoingtotoilethandlingrawmeatandpassingthebacteriaacrosstocookedfoods.
Protectionstrategy: Sometypescansurviverefrigeratorandfreezertemperaturesandsomehavedevelopedresistancetoantibiotics.Cooking,washinghandsandavoidingcrosscontaminationinthekitchenhelp.
LISTERIAMONOCYTOGENES
Whatisit? Bacteria.
Signsandsymptoms: Headache,fever,nausea.Canleadtomeningitis,septicemiaanddeath.Itcanbeespeciallydangeroustoagedpeople,pregnantwomen(spontaneousabortionorstillbirthpossible),andpeoplewithcanceroracompromisedimmunesystem(canleadtoarthritis,braindamageandvariousinternalinflammations).
Timetosicknessafterconsuming: Approximately3weeks.
Illnesslasts: Varies,dependingoncomplications.
Favouritefoods: Highproteinmoistfoodssuchaschickenandsoftcheese,unpasteuriseddairyfoods,pate,fermentedsausage,rawfish,leafyvegetables,salads(forexample,coleslaw),smokedmussels.
Howdiditgetthere? Fromanimals,soil,water,sewage,cropsfertilisedwithsewage.
Protectionstrategy: Cookingto70C(158F),ensuringthateventhecentreofthefoodreachesthistemperature.Cangrowatrefrigeratortemperatures,butiskilledbyshortwaveultravioletlight.
Anoutbreakoflisteriosis,whichoccurredinFrancein1992,wastracedtoconsumptionofjelliedporktongues.Therewaswidespreadillnessleadingtothedeathsof63people.InastartlinreminderofthespecialriskListeriamonocytogenesposestopregnantwomen,thisoutbreakresultedin22miscarriages.
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SALMONELLA
Whatisit? Bacteria.
Signsandsymptoms: Nausea,fever,diarrhoea,stomachcrampsanddehydration,sometimesfeverandchills.Canleadtomeningitis,pneumoniaordeathinelderlyorsickpeople.
Timetosicknessafterconsuming: 1224hours,average18hours.
Illnesslasts: 2448hours.
Favouritefoods: Highproteinfoodssuchaschicken,turkey,shellfish,meat,eggs,rawvegetables,unpasteurisedmilk,andincompletelyreheatedlarge,frozenorrefrigerateddishesofhighproteinfood(e.g.fromthemicrowaveoven).
Howdiditgetthere? Faecalcontaminationfromanimals,humans,birds.Poorhandling.Itcanbecarriedbyfliesandotherinsects.
Protectionstrategy: Cookingto70C(158F)for10minutes.
SHIGELLA
Whatisit? Bacteriaanditstoxin.
Signsandsymptoms: Diarrhoea(sometimesbloody),vomiting,fever,abdominalpainandacontinualfeelingofneedingtogotothetoilet.
Timetosicknessafterconsuming: 17daysbutgenerally14days.
Illnesslasts: 47days.
Favouritefoods: Beans,milkproducts,rawvegetables,salads(e.g.tuna,potato,prawn/shrimpsalads),wellwater.
Howdiditgetthere? Spreadbypersontopersoncontact,foodandpersonalhygiene,water,fliesfaecesofinfectedpeople.
Protectionstrategy: Goodpersonalhygienewillreduceriskofinfectionwashfruitandvegetableswithtreatedorboiledwaterchildrenareahighriskgroup.
STAPHYLOCOCCUSAUREUS('GOLDENSTAPH')
Whatisit? Abacteriumwhichproducesatoxin.
Signsandsymptoms: Vomiting,diarrhoea,stomachcramps,headaches,chills,fever,weakness.
Timetosicknessafterconsuming: 16hoursbutgenerally23hours.
Illnesslasts: 624hours.
Favouritefoods: Hamanddelimeats,custard,cream,cheese,milk,prawns/shrimp,smorgasbords,saltyandsugaryfoods,lowacidcannedfoodspotatosaladsoffish,poultry,hamorpotatoextendedshelfliferefrigeratedfoodsandmodifiedatmospherefoods.
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Howdiditgetthere? Carriedinnoseandfacialhair,onhandsandbyunhygienichandling.Watchforinfectionsonhandsofpeoplehandlingfood,orfoodpreparerswithcolds/flu,runnynose,pimples,acne,burns.
Protectionstrategy: Heatingto70C(158F)for30minutes.
VIBRIOCHOLERAE
Whatisit? Bacteriaproducingatoxin('cholera'istheillness).
Signsandsymptoms: Diarrhoea(sometimesbloody),vomiting,nausea,severedehydrationcanleadtosepticaemiaordeath.
Timetosicknessafterconsuming: 6hoursto5days.
Illnesslasts: Uptoseveraldays.
Favouritefoods: Rawseafoodsincludingprawns/shrimp,crabandoystersindevelopingnations:water,iceandfoodsrinsedinwater,suchasvegetablesandrice,softdrinks.Grainsandlegumesgrownincholeraendemicareas.
Howdiditgetthere? Humanfaecescontaminatingfoodandwater.
Protectionstrategy: Cookingkeepingsewageawayfromfreshwater.
VIBRIOPARAHEMOLYTICUS,V.VULNIFICUS,V.MIMICUS,V.HOLLISAE&V.FUNISSII
Whatarethey? BacteriaofseveralspeciesintheVibrio(cholera)family.
Signsandsymptoms: Diarrhoea(canbebloody),abdominalpain,cramps,vomiting,headache,nausea,chillsandfevercanleadtodeath.
Timetosicknessafterconsuming: 4hoursto5days,dependingontype.
Illnesslasts: 36days.
Favouritefoods: Raworundercookedseafood,particularlyoysters,shellfish,clams.
Howdiditgetthere? Theyarenaturallyoccurringintheseaandmaybelinkedtosewagecontamination.
Protectionstrategy: Cookinganddryingcansurviverefrigerationandfreezing
YERSINAENTEROCOLITICA
Whatisit? Bacteriaanditstoxin.
Signsandsymptoms: Strongabdominalpain,diarrhoea,canleadtoulcerationofthecolon,dermatitis,lymphsysteminflammation,septicaemiaandarthritis.
Timetosicknessafterconsuming: 25days.
Illnesslasts: 12daysbutcanlastweeks.
Favouritefoods: Dairyproductswherepasteurisationhasbeenineffectiveorcontaminationhasoccurredafterpasteurisation,water,icecream,powderedmilk,chicken,vacuumpackedmeat,pigmeats,seafood.
Howdiditgetthere? Contaminationbyanimalfaecesafterthefoodprocessingstage,poorhandlingoffood.
Protectionstrategy: Coldisineffective:itcangrowatrefrigerationtemperatures.Cookfoodsto75C(167F).
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Viruses
Apartfrombeingthesmallesttypesofmicroorganismsaslittleasonehundredththesizeofsomebacteriavirusesareunlikebacteriaandfungiinthattheycanonlyreproduceoncetheyhavemadetheirwayinsidelivingcells.Theydonotgrowandincreasetheirnumbersinsidefood.Foodissimplyaveryneatwayforthevirustomovefromoutsidetoinsideabody,whereitworksitswayintothecellsandcanthenreproduce.Oncetheviralnumbersreachasufficient'dose',thehostbecomesill.
Whenasickpersonvomits,coughs,sneezesorspits,theyspreadviralparticlesbythemillionsintheirsaliva,possiblypassingthemtoothernearbypeople.Virusescansurviveonyourclothing,getpickeduponyourhandsandpassontothefoodyouarepreparing.Extracaremustbetakenwhencaringforyoungchildrenandinvalids,asurineandfaeces,itshouldbenoted,canalsospreadviruses.
Itisestimatedthatvirusesarethecauseofaround10percentoffoodborneillnessesinAustralia.SomeevidencefromtheUnitedStates,however,placesthefigurecloserto35percent.Twoexamplesofviralillnessesaregastroenteritisandhepatitis.
Themaintroublespotswithfoodbornevirusesincludemolluscs,rawfruitandvegetables,andoftenhandledfoodssuchassaladsanddesserts.Molluscshellfishsuchasoysters,musselsandcocklesmaybecontaminatedfromsewageinthewaterinwhichtheygrow,oftencoastalorestuarinewatersorriversintowhichsewageisdumped.Theshellfishactasfilters,leadingtoaconcentrationofthevirus.And,ofcourse,suchshellfishareofteneatenraworwithminimalcooking.
Fruitandvegetableswhichareservedrawcancarryvirusespickedupfromirrigatingorfertilisingthemwithsewageorsewagecontaminatedwater.Iftheyarenotthencooked,theviruscomesstraightfrom
CHOLERA:THEEPIDEMICTHATWON'TDIE
EpidemicsofcholerahavesweptthroughEurope,AsiaandAfricaforhundredsofyears,killingmillionsofpeopleandcripplingtheirsocieties.Andthen,quitesuddenlyintheearly1900s,theillnessappearedtodieoutindevelopednations.Bythistimeweknewhowtoconstructbettersewersandtheimportanceofmaintainingapurewatersupplyfordrinkingandcooking.Inthepoorernations,however,choleracontinuedtoclaimlivesthroughoutthecentury.
ButcholeracontinuestoappearevenincountriesliketheUnitedStates.In1973therewasacaseofcholerainTexasfiveyearslater11peopleinLouisianacamedownwithitandanother12in1986andmoreintheearly1990s.Theriskissmall,however,indevelopednations.ButbeextracarefulwhentravellinginCentralandSouthAmerica,Africa,Asiaandinanycountrywithpoorlyperformingwaterorsewagesystems.
thepaddocktoyourplate.Withfruitandvegetables,unlikeshellfish,theviruswillbefoundonthesurfaceofthefoodwhereitishighlysusceptibletoheattreatment(cooking).
Saladsanddesserts,whichoftenrequiremuchhandlingbychefsandkitchenstafftogetthemintotherightshape,mayalsoeasilybecontaminated.Again,saladsanddessertsreceivelittleornocookingaftertheyhavebeenhandled,whichisaperfectopportunityforavirustopasswiththefood.
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Virusesposeaparticularproblembecause:
thereisnosimplemeansofdetectingtheirpresenceinfood
unlikemostbacterialproblems,itdoesnottakealargenumberofvirusparticlestopassillnesstoaperson
acookorwaitermighthavebeencontaminatingfoodfordaysbeforeshowingthefirstsymptomsofillnessthemselves
virusesaretough.Theycanresistchilling,freezing,preservativesandionisingradiation,aswellasacidicfoodsandpicklinginvinegar.
Fortunatelyvirusescanbekilledquicklybyheatingfoodto85C(185F).Youshouldunderstandthatyouaretakingabiggerviralriskwithrawfoods,especiallyshellfish(seeChapter8).
HEPATITISA
Whatisit? Virus.
Signsandsymptoms: Fever,vomiting,malaise,lossofappetite,followedbyjaundice.Deathisrarebutmayoccur,particularlyintheelderly.Symptomsdevelopgraduallyandareusuallymoresevereinadultsthanchildren,
Timetosicknessafterconsuming: 36weeks.
Illnesslasts: Uptoseveralmonths,dependingoncomplications.
Favouritefoods: Oysters,prawns,molluscs.
Howdiditgetthere? Persontopersontransmission.Itcomesfromthehumanintestine,passingbypoorfoodhandlingorbycontactwithcontaminatedwater(forexample,thesewagepollutedwaterinwhichtheoystersgreworwereheldcropirrigation).
Protectionstrategy: Personalhygieneavoidinghighriskfoods.
NORWALK
Whatisit? Virus.
Signsandsymptoms: Suddenonsetofvomiting(maybeprojectile),explosivediarrhoeaandabdominalpain.
Timetosicknessafterconsuming: 1572hoursbutgenerally2436hours.
Illnesslasts: About3days.
Favouritefoods: Orangejuice,water,oystersandsalads.
Howdiditgetthere? Persontopersontransmission,comesfromhumanintestine,poorfoodhandlingorbycontactwithsewagecontaminatedwater.
Protectionstrategy: Useonlytreatedwaterorboiledwaterforwashingsalads,foodpreparationanddrinkingavoidrawseafood.
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YeastsandMoulds
Yeastsandmouldsarelivingmicroorganisms,likebacteria.Yeastscanmakefoodgo'off',accompaniedbybubbling,sometimesslime,andanaromasomethinglikebeerorwine.Thereareusefuland'good'yeasts(suchastheonesusedwhenbreadismadeorbeerisbrewed),aswellasbadyeaststoavoid.Yeastsarenotusuallyassociatedwithfoodpoisoning:onlyfoodspoilage.
Mouldsareamongthemostobvioustypesoffoodspoiling.Youhaveprobablyseentheirspidery,bluegreenpowderonoldbreadontheskinsofrottingorangesonthetopofjamsandpreservesoronthesideofablockofcheese.Theirsmellcanbepungent,likeawetdogorawetcardboardbox.
Infactonsomefoodsyouaremorelikelytofindmouldsratherthandangerousbacteria.(Generally,bacterialikeawetfoodwithplentyofmoisturetohelpthemmovearound.Oneofthewaystocontrolbacterialgrowthisbydryingtheproduct,forexample,thecuringofham.)Mouldswillhappilygrowatmuchlowermoisturelevels.Theyturnuponfoodslikenuts,grains,peanuts,cereals,bread,cheeseandjams.
Moulds,likesomeferns,spreadbyforming'spores'whichblowawaytocoverotherpartsofthehostfood,eventuallygrowingtomaturityandproducingfreshspores.
Themouldwehaveheardmostaboutinthemediaistheoneassociatedwithpeanutsandpeanutbutter.ThemouldAspergillusflavusgrowsnaturally,inthefieldorevenafterthecrophasbeenharvested,andcanproduce'aflatoxin',mostcommonlyinpeanutandcorncrops.Themouldproducesthetoxininitshighestandmostdangerouslevelsinyearsofdroughtorothertraumawhichhasdamagedthosecrops.
Foodstandardsplaceanupperlimitontheamountofaflatoxinwhichispermittedinpeanuts(notmorethan15partsperbillioninAustralia),andmostmanufacturershaveequipmenttodetectit.However,whoischeckingthepeanutsinsmallhealthfoodshops(whereyoucangrindyourownpeanutpaste)orinlocalstreetmarkets?
Anotherfamoustoxinproducedbyamouldispatulin,whichturnsupinapple
ASPERGILLUSFLAVUS
Whatisit? Mouldthatproducesaflotoxins.
Signsandsymptoms: Largeexposurescanproduceabdominalpain,swellingduetofluidretentioninbodytissues(oedema),liverdamage,hepatitiscanleadtolivercancerandimpairedimmunesystem.
Timetosicknessafterconsuming: Severaldaysorevenyears,dependingondose.
Illnesslasts: Canbelongtermillness.
Favouritefoods: Peanuts,peanutbutter,peanutoil,corn,nuts,figs,cocoabeans.
Howdiditgetthere? Naturalmouldonthecrop,particularlyindroughtconditions.
Protectionstrategy: Governmenttestingofcrops.
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juice,organicciderandfruitssuchasmouldyapples,apricots,cherries,grapes,peaches,pearsandplums.Studiessuggestitmaybeacarcinogen.(However,don'tconfuseamouldytasteorodourwiththesafebutsour,vinegarliketastethatfruitjuicesacquire.Thissourness,whichindicatesfermentationistakingplace,isnotahazard.)
Whatshouldyoudowithmouldyfoods?Inmostcases,throwthemawayorputtheminthecompost.(SeealsoChapter10.)
Parasites
Bacteriaandvirusesarearguablywhatmostpeoplethinkaboutwhentheyturntheirmindstofoodborneillness.Whilethesearethemostcommoncausesoffoodpoisoningthereareotherproblemswhichcomewithfood.
Tapeworm,roundwormandflukesaretypesofparasiteswhichliveinsidecattle,sheep,pigs,fishandthelike,andcanalsobefoundinvegetableswhichhavebeenirrigatedorfertilisedusingsewagecontaminated
CRYPTOSPORIDIUMPARVUM
Whatisit? Protozoan.
Signsandsymptoms: Profuse,waterydiarrhoea,abdominalpain,vomiting,lowgradefever,weightloss,lossofappetite,anorexia.Itcanleadtodeathinsomepeoplewithlowimmunity.
Timetosicknessafterconsuming: 214days.
Illnesslasts: 23weeksbutcanlast6weeks.
Favouritefoods: Waterusedfordrinking,foodpreparationorforswimmingrawmeat(particularlysausagesandoffal),unpasteurisedmilk,fruitandvegetables.Itcanpassfrompersontopersoninplaceslikechildcarecentres.
Howdiditgetthere? Fromliveanddeadanimals,persontopersoncontact,contaminatedrawfoodsandthewatersupply(arguablyfromfarmandwildanimals).
Protectionstrategy: Specialfiltrationofwatersupplyitresistschlorinetreatment.Itisinactivatedbydryingheat,suchascookingorboiling,andbyfreezing.
GIARDIALAMBLIA(ORGIARDIADUODENALIS)
Whatisit? Protozoa.
Signsandsymptoms: Diarrhoea,weakness,nausea,excessivesmellysulfurousburps,wind.
Timetosicknessafterconsuming: 710days.
Illnesslasts: Afewdaystoafewweeks.
Favouritefoods: Water
Howdiditgetthere? Itisfoundwidelyinnaturefaecalcontamination.
Protectionstrategy: Filtrationanddisinfectionofdrinkingwateruseofbottledwaterboilwaterforoneminuteandallowtocool.Donotwashsaladsinuntreatedwater.
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water.Oftenthisismoreaproblemindevelopingnations.
Parasitesaboundinnature,butoftenourproductionpracticesmaketheproblemworse.Inaquaculture(anemergingindustrywherefish,oftenforsushi,areraisedintanks)theenvironmentcanbecontrolled.Unfortunatelyaquaculture,throughitscreationofamonoculturalenvironment,mayactuallycontributetothespreadofpathogenssincemanycompetingorganismshavebeenremovedfromthefoodchain.Someaquacultureavoidsthisbyusingoceanpens.
Iffoodisservedraworundercookedsushi,sashimi,rawbeefslices,salmonandsoontheparasitescansurvivethekitchenandpasstothediner.Onceinside,theyheadforplacesliketheliver,intestineorlung,wheretheygrowandcauseproblemslikemalnutrition,hungerpains,increasedappetite,musclepain,headache,vomiting,respiratoryproblemsandconvulsions,dependingonthetypeofparasiteandtheageoftheperson.
Thereisaparasitewecanacquirefromhandlingrawmeat,orfromcats.Toxoplasmagondiicanbepickedupifwehandleorcomeincontactwithinfected,stalecatfaeces(inthegarden,forexample),givingussymptomssimilartoaboutoftheflu(called'toxoplasmosis').Generallythesymptomspassquickly.Butpeoplewithlowimmunity,orpregnantwomen,shouldbemorecarefulandweargloveswhenpreparingrawmeat,gardeningorhandlingkittylitter.Indeedifthemothergetsinfectedthebabymightbebornwiththeparasitewhichmightinterruptthenormaldevelopmentofthechildatsomestage.Peoplewithreducedimmunitycanbecomeblindor,intheworstcases,mightdiefromtoxoplasmosis.
Cookingkillsmostoftheparasiteswecomeacross.Freezingisnotalwaysaseffective.
AccidentalExtras
Youeatameal,yougetsick,youblamethebugs.Butyoumaybewrong.Thereareallsortsofchemicalswhichgetintothefoodsupply.Somearequiteharmless,whileothersbecomepoisonousiftheyarethereintherightamountoriftheygotintothefoodatasensitivetime.
Forexample,farmersusechemicalpesticidesandherbicidestocontrolweeds,diseasesandinsectpestswhichmightotherwisedevourorruintheircropsoffruitandvegetables.Werelyonsuchchemicalsforthewideandcheapavailabilityoftheseimportantfoods,althoughthedemandisgrowingforfruitandvegetablesthatare'pesticidefree'and'organicallygrown'.
AJanuary1999USDepartmentofAgriculturesurveyofpesticideresiduesinfoodfoundlowlevelsofresiduesin57percentoffruitandvegetablesamples,87percentofsoybean,80percentofwheatand15percentofmilksamples.Thesamplescamefromfoodsoriginatingin43statesoftheUnitedStatesand23foreigncountries,soitwasafairlylargepoolthatwassurveyed.Puttingthistogether,theresearchersfoundlowlevelbutwidespreadpesticideresiduesinasmanyas28foodseatenbyAmericans.Onequarterofthepesticideresiduesfoundinfruitandvegetableshadbeenaddedafterthefoodhadbeenharvested(forexample,whileinstorage,tokeeppestsatbay).Itisahugeissue,andonedaywemayhavedifferentideasaboutwhatallthesepesticidesaredoingtousevenatlowlevels.
Scientistsandchemicalmanufacturersknowthegenerallyaccepted'safe'dosesofthesechemicals,butthereisnothing(otherthantheirhighcost)tostoptheindividualfarmerusingtoomuchofthepoison.Educationaboutagriculturalchemicalsisessentialforfarmers,thoughitislackinginmanypartsoftheworld.
Asecondproblemoccursifthechemicalsareusedatthewrongtime.Themostobvi
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ousdangeriswhenacropfindsitswayintotheshopsbeforethechemicalshavehadsufficienttimetobecomeharmless.Pesticidesandagriculturalchemicalshavewhat'sknownasa'withholdingperiod':aperiodofanumberofdaysduringwhichthefruitorvegetablesmustnotbeeatenasitmaybepoisonoustohumans.
Otherpoisonouschemicalswhichmaygetintofoodinclude:
leadandmercuryheavymetalsandotherpollutantsinthesea.
disinfectantsandcleaningchemicals,suchascausticsoda,usedinthefoodprocessingmachinerytocleanandsterilisetheworkplaceortheircontainers(suchasglassbottles)laterusedforfoodordrink.Benchtops,pots,pansandknivescanbecontaminatedinthesameway.
thecontaineritself,whichcanintroduceapoisonintothefood.Oneexampleisthetincoatingusedtopreventcorrosionofcans.Acidicfoodsmaydissolvesomeofthetin.
monosodiumglutamate(MSG),usedasaflavourenhancer.ItisastapleoftherestauranttradeandiswellknownforgivingthedineraterrificthirstaftereatingamealhighinMSG.TheremaybeothermoreseriousreactionstoMSG,suchasatypeoffoodallergyreaction,andasthma.However,theresearchisnotconclusive.Italsooccursnaturallyandathighconcentrationsintheskinsofsomefruits.
Summary.
Foodborneillnessmaybeduetobacteria,avirus,amould,fungusoranonlivingtoxinreleasedbyamicroorganism.Sometimesprotozoaareatfault.
Thereisoftenarelationshipbetweenparticularfoodsandparticularpathogens.
Werelyondifferenttoolsandtechniquestoneutraliseorcontroldangerousmicroorganisms.Thetechniquesareusuallysimpletoimplementeveninthehomeandhighlyeffective.
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Chapter3WhoIsMostVulnerable?
Intrackingdownthecauseofaparticularboutoffoodpoisoning,itishandytoknowthatsomeillnesseshitcertainagegroupsmoreoftenorwithgreaterseveritythanothers.
Forexample:
theelderlyandtheunbornareatparticularriskfromListeria
forSalmonellaitischildrenagedunderoneyear
forCampylobacter,itistheonetofouragegroup
symptomsofGiardialambliaaremoresevereinchildrenthanadults
E.coli's'enterohaemorrhagic'formsappeartohavetheirmostprofoundeffectonyoungchildren,particularlyaroundtheageoffourorfive.
Children
NowherewastherealityofanagelinkseenmoreforciblythanintheGaribaldimettwurstincident(seepage49).Herewasasalamithatwaseatenbyadultsandchildren,yetalmostallthoseaffectedstronglybyfoodpoisoning(inthiscaseE.coli)werechildrenagedfromfourmonthsto12years,withmostcasesinagrouparoundfouryearsofage.Wedon'treallyknowalotaboutwhythishappens.Theconnectionshaveonlybeenpickedupbyresearcherswhoaddupthenumbersofreportedcases.
Onetheoryisthatchildrenhaveareasintheirlargeintestineswhichbindthebacteriaoritstoxin,whereasinadultsthesesiteshaveclosed.Accordingtothisview,thesereceptorsmayopenagaininoldage,helpingtoexplainwhytheelderlyareatheightenedrisk,oncemore,fromcertainbacteria.
'Itisacomplexsituation,largelyuninvestigated,'saysAssociateProfessorScottCameron,ClinicalAssociatewiththeDepartmentofHealthattheUniversityof
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Adelaide,'Theremaysimplybeabiasinthesystembecausewerushofftothedoctorandgetthechildtestedbutnottheadult.'ProfessorCameronsuggeststwobroadreasonswhychildrenareoftenmoreaffectedbycertainpathogens.Firstly,thereistheideathateveryoneisexposedtothesepathogens,andwedevelopasymptomaticillnessatthetimeoffirstexposurewhenwearechildrenbeforedevelopingsomekindofimmunitythatprotectsuslaterinlife.
Secondly,itmaybethatveryyoungchildrenaremorelikelythanadultsandolderchildrentoeatcontaminatedfood.'Behaviouralaspectsmakeitmorelikelyforonegrouptobecomesick,'headds.Forexample,it'sthechildwhoismostlikelytolickthecakemixoutofthebowl,consumingsomeraweggatthesametime.
Parentsshouldalsobearinmindthatbacteriasurviveandgrowonthevariousbitsandpiecesofbabyfeedingequipment,frombottlesandteatstononspillcupswithnarrowopeningsorplasticstrawswhichcanbedifficulttoclean.Oftenthesethingsarenotsterilisedtheymayevenbouncearoundinsidethenappybag,pickingupbacteriaandmicrobesfromallaround.Littlechildrenalsolikeexploringtheirenvironment,therebyexposingthemselvestorisks.
Areweputtingnaturalimmunityatrisk?
IntheUnitedStateswinterof1997,sevenchildrenacquiredapathogenicstrainofE.colifromadaycarecentreinSpokane,Washingtonfromplayingwithcontaminatedmodellingclay,toys,sandandsoil.AnotherpathogenicE.colioutbreak,thistimeinAtlantaGeorgia,saw26childrencomedownsickafterplayinginapoolatthelocalwaterparkonechilddevelopedkidneycomplicationsanddied.Aleakingnappywassuspectedofbeingthesourcewhichintroducedthepathogenintothepool.
Acurrentcontroversialhypothesis,underinvestigation,isthatbytryingtoridourlivesofthepresenceofbacteria,weriskreducingourimmunity.Thisisperhapsmerelythescientificcommunityputtingaglossonwhatparentsalreadyknow:ifyousendyouryoungchildtoapreschoolorplaygrouptheywillcomehomewithallmannerofcoldsandillnesseswhichsomehowhelpthechildgrowupwithamorerobustconstitution.
Therecentdebate,however,hascentredmoreonhealthproblemswhichseemtorelatetoaffluenceandcleanliving.Publichealthauthoritiesknowthattheratesofasthma,hayfever,childhoodeczemaandotherallergiesaregenerallyincreasingindevelopednationssuchasWesternEurope,Australia,JapanandtheUnitedStates.Accordingtothehypothesis,bycleaningupourimmediateenvironmentsothoroughlywithantibacterialsurfacecleansers,soapsandevenantibacterialpillowschildrengrowupwithoutthestimulinecessarytoputtheirimmatureimmunesystemstothetest.Itisthesetests,itisargued,whichhelpdeterminewhetherinfutureaperson'simmunesystemwillrespondtoanallergenortoxininawaywhichreleaseshistaminesinsidethebody.(Histaminestriggersomeveryfamiliarsideeffects,includingitchyeyes,arunnynoseandwheezybreathing.)
Itisaninterestingproposition.Ifwearenotexposedtoaverywiderangeofbacteriaandothermicroorganismsatanearlyage,doourdefencemechanismsproperlydevelopallroundprotectiontechniques,oronlyalimitedresponsetobodilythreats?Arewecleaningourselves,ourhomesandevenourfoodstothepointofourownharm?Shouldwegetupfrominfrontofthetelevisionandspendmoretimeoutside,playinggames,rollinginthedirt,swimmingatthebeachandsocialisingwithawiderangeofpeople?Perhapsitistruethatthemoreweisolateourselvesfromtheenvironment,themoresicklywemightbecome.
Ofcoursethereismoretothisissuethanasinglesimpleanswer.Wedon'treallywanttogobacktoexperiencingpolio,measlesoralifethreateningboutoffoodpoisoning.Nor
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shouldweignoretheroleourgenesplayindeterminingourhealthandaffinityforcertainillnesses.Hopefully,furtherresearchwilltellushowtodevelopourimmunesystemstotheirfullestpotential.
ThosewithReducedImmunity
VibriovulnificusandtheparasiteCryptosporidium,generallyfairlyharmlesstoahealthyperson,couldcauseseriousillness,perhapsevendeath,inapersonwithlowimmunity.Peoplewithlowimmunityinclude:children,pregnantwomen,nursingmothers,theaged,transplantrecipients,thoseusingimmunosuppressantdrugstotreatcancerorevenasthma,peoplewithHIV.
Itisrecommendedthatpeoplewithlowimmunityboilalldrinkingandcookingwater(onastoveorinakettlewithoutanautomaticcutoff).OneofthemainreasonsistokillCryptosporidiumparvum,whichisparticularlydangerousforthosewithreducedimmunity.Normallytheillnessassociatedwiththisprotozoanrunsitscourseofdiarrhoea,weightlossandabdominalpainwithintwoorthreeweeks.However,ifapersonhasreducedimmunityitcanlasttwiceaslongorcanevenbecomeachronichealthproblem,withinfectionofthebody'sorgansandtissues.Atpresentthereisnoknowneffectivemedicaltreatmenttocombatthisillness.
Cryptosporidiumisfoundinthewatersuppliesofmanytowns,citiesandcountries,particularlyindevelopingnationsbutalso,onoccasion,inindustrialisedcitiesandtowns.ItwasinvolvedintheSydneywaterscareofJulySeptember1998.(ItisimportanttonotethatthereareanumberofdifferentstrainsofCryptosporidium,butnotallstrainscauseillness.Somearepathogenic:othersarenot.)
BecauseitissocommoninplaceslikeAfricaandAsia,itisbelievedtobeamajorcauseoftravellers'diarrhoea.Thisprotozoanisresistanttochlorinetreatment(asusedbywaterauthorities)and,thankstoitsminutesize,canevadeallbutthemostsophisticatedfiltrationsystems.Itisariskforeveryonebutamostparticularriskforchildren,theelderly,peoplewithHIV,thoseundergoingcancertherapy,andotherswithlowimmunity.
WhyAreOlderPeopleatGreaterRisk?
Therearesomeideasastowhywebecomemorevulnerabletofoodpoisoningaswemoveintooldage.Forexample,anolderpersonsecreteslessacidintheirstomachwheneating,andstomachacidisoneofthetoolsourbodyusestocombatbacteriainfoodanddrink.Generalimmunitycangointoagradualdeclinetoo.
Sometimesoursensesdeteriorateasweage,particularlyourresponsetosmellandtaste.Whilethismightmeanwebecomemoreatriskofeatinganddrinkingspoiledfood(likesourmilk)thisshouldnotbeconfusedwithanyabilitytospotfoodwhichmightleadtopoisoningorinfection.
Olderpeoplecanalsobeatincreasedriskoffoodborneillnessforawholerangeofsocialandeconomicreasons,includingincreasedreliance(forthehomebound)onfoodpreparedelsewhereandbroughtover,orfromtryingtosavemoneybyhangingontoleftoversorfoodpastitsusebydate.
PregnantWomen
Listeria,inparticular,isadangerousformoffoodpoisoningforanyonewhoispregnant:theunbornchildcanbeaffected,andmiscarriagecanoccur.Listeriosiscanevenbefataltotheadult.Sometimestheauthoritiesissuespecificwarnings:theBritishDepartmentofHealthadvisespregnantwomennottoeatpatewhilepregnant.Formosthealthy,nonpregnantadults,however,Listeriaisnotmuchofaproblem.
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VirusessuchashepatitisAandhepatitisE,whichcanbefoodborne,maycauseamoresevereillnessinpregnantwomen,resultinginahighmortalityrate.Figuresforwomenindevelopingnationsshowdeathratesofabout17percentforhepatitisAandashighas33percentforhepatitisE.Indevelopednationsthedeathrateswouldnotbethisgrim,butthewarningremainspertinent.
Summary
Theelderlyandpregnantwomenshouldbewaryoffoodslikesoftcheeses,pateandcoleslaw.
BeparticularycarefulwithfoodslikechickenforchildrenunderoneyearofagebecauseoftheheightenedsusceptibilityofthisagegrouptoSalmonellainfection.
Rawmeatsareaspecialproblemforthoseagedonetofouryears.
Thosewithlowimmunityshouldboiltheirdrinkingwater.
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Chapter4HowDoIProtectMyself,MyFamilyandFriends?
Genrallyspeaking,peoplewhoarestressed,overtired,recoveringfromillness,aswellastheveryyoungandtheelderly,aremoresusceptibletofoodpoisoningandfoodborneillnessthanarehealthypeople.
Maintainingyourgoodgeneralhealthisyourfirstlineofdefence.Thisinvolves:
havingaproperdiet
drinkingplentyofcleanwater
gettingadequaterestandrecreation
gettingregularexercise
breathingcleanair
havingapositiveattitudeonlife.
HowYourBodyProtectsItself
Ourtechniquesandtricksformakingfoodsafetoeatareonlypartoftheequation.Indeed,themostspectaculardefencesoccurnaturally,withinourbodies.
Thebody'sfirstlineofdefenceistheacidinourstomachs.Stomachacid,whichistypicallyaroundapHof3,killsmanyharmfulbacteriabeforetheyreachtheintestinewheretheyfindmorefavourableconditionsforgrowth.Ontheotherhand,fatinfattyfoodslikechocolatecanhelpprotectbacteriafromstomachacids,therebylettingthemmaketheirwaytotheintestinewheretheygrow.Theuseofantacidmedicines,orsimplyhavingalottodrinkwithyourmeal,candilutestomachacidsandleadtothesameresult.
TIPColdstoragemerelybuysyoutime:notsafety!
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Anotherlineofdefenceisthemultitudeofharmlessbacteriawhichnaturallyliveinourdigestivesystem.Thesebacteriacompeteforavailablenutrientsandtherebylimitthegrowthofanypathogenicbacteria,whichthendieofforpassoutofthebodybeforetheygetachancetomultiplyandcauseproblems.Theuseofantibioticscanleadtoareductioninthelevelsofgoodbacteriainourdigestivesystemandtherebymakeusmorevulnerabletofoodpoisoningforafewweeksaftertakingthetreatment.Thisiswhereeatinga'probiotic'food,suchasayoghurtcontaininglivebacteria,mayhelpbuildupthenumbersofgoodbacteriaandincreaseourresistancetofoodpoisoning.Thispracticeisparticularlybeneficialwhenrecoveringfromillness,orbeforegoingoverseas.
Somebacteriamultiplytolargeandharmfulnumbersoncetheyreachourintestine:forexample,Salmonellatyphi(whichproducestyphoidfever)andVibriocholera.Oneofthebody'sdefencestosuchbacteriaistheproductionofwhitecellswhichconsumeanddestroytheinvaders.Whitecellsarealsoanimportantdefenceagainstfoodpoisoningcausedbyviruses.Theimmunesystemalsoproducesantibodieswhichdestroythevirusparticles.
Someofthesymptomstraditionallyassociatedwithfoodpoisoningvomitinganddiarrhoeaaremechanismsusedbythebodytoriditselfoftoxicsubstancesbeforetoomuchpoisonhasbeenabsorbed.Andtheyactquicklytomovelargevolumesout.
Theliverisanothermajorplayerinourdefenceagainsttoxinssuchaspesticideresidues,orchemicalssuchasleadandarsenicwhichmaybeinourfoodanddrink.Oncethesechemicalshavebeenabsorbedbythebodytheygenerallypasstotheliverwheretheyare'detoxified',orconvertedtoaformwhichcanbeexcretedfromthebodyinurineorfaeces.
Insomeinstances,suchaswhere'heavy'metalsareinvolved,thedetoxificationprocesstransportstheelementtoyourhair,whereitcanbestoredoutofharm'swayuntilthehairfallsoutoriscut.Itbecomes,inaway,geographicallyisolated.
FoodStorage,PreparationandPreservation.
Livinginadevelopednationitiseasytogainahighlevelofprotectionagainstfoodpoisoningandfoodintoxication.Ofcourse,youcanneverhavefoolproofprotectionfromfoodborneillness,butyoucangetalongwaybylearningtherules.Herewewillrunthroughwhatworksandwhatdoesn'ttosolvetheproblems.
Cold
Freezingwillnotkillbacteria,butitwillstopthemgrowingandreproducing,holdingtheminakindoflimbo.Howcoldiscoldenough?Youneedtokeepfoodatatemperaturebelow5C(40F)intherefrigeratororbelow18C(0F)ifitistobeputinthefreezerforlongertermstorage.Ofcourse,thismeansyouhavetobecarefulwhenyoutakefoodoutofthefridgeorfreezerasitmightcontainbacteriajustwaitingfortherighttemperatureandconditionstomultiplyrapidly.
Coldfixesnothingandmakesnofoodsaferthanitwaswhenitfirstwentintothefridgeorfreezer.
HeatandCooking
Cookingisperhapsournumberonehomeprotection.Cooking(toasufficientlyhightemperatureandforasufficientperiodof
TIPCookingisyourmostimportantallyinthefightagainstfoodpoisoning.Itisnottheperfectanswerforallsituations,butitdealseffectivelywithmostofthecommonproblems.
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time)willeffectivelykillawholehostoforganismsandvirusescontaminatingfood,including:Salmonella,Campylobacterjejuni,Clostridiumperfringens,Clostridiumbotulinum,Cryptosporidiumparvum,Giardialamblia,Listeriamonocytogenes,Staphylococcusaureus,Vibriocholerae,E.coli,hepatitisA,Norwalkvirus,yeastsandmoulds.
Tokillyeastsandbacteriayoumustheatfoodabove60C(140F)for15minutes.Virusescanrequirehighertemperaturesstill:atleast80C(176F).Manymouldswillgiveupifheatedabove60C(140F)for10minutes.Somebacterialsporesmaysurviveevenhoursofboiling,asinstewsandsoupsforexample.However,ifyoueatthesoupsoonafterheating,thebacteriawillnothavesufficienttimetobecomeaproblem.
'Pasteurisation'isaformofcookingusedextensivelyinthefoodprocessingindustry,particularlyfordairyfoods,cannedfoodsandjuices.Takingmilkasanexample,pasteurisationinvolvesheatingthemilktoahightemperature(butnotboiling)ofatleast72C(162F)for15seconds(oraslightlyhighertemperatureforaslightlylowertime)themilkisthencooledquicklytobelow5C(40F).Milk,evenwhenpasteurised,needstobekeptintherefrigerator,assomebacterialsporesandevensomebacteriacansurvivepasteurisation.UHTmilkis'ultraheattreated'to133C(271F)andthenplacedinasterilepack.Thepackagingisapapercartonorplastictublinedwithpolytheneoraluminiumtokeepoutoxygenandlight.Asaresultofthisprocessandcare,acartonofUHTmilkdoesn'tneedrefrigerationuntilopened.
Butsomeorganismscansurviveattackswhichwouldkillmostothers.Forexample,cookingwillnotalwayskillBacilluscereusandClostridiumperfringensspores.Heatalsohaslittleeffectontoxinsitmightkillthebacteria,butnotthechemicaltoxinsproducedbythosebacteria.NorwillheatdestroytoxinsproducedbyStaphylococcusaureus(thatcontaminatesfoodbycoughsandsneezes).
Drying
Anothermethodofcontrol,withoutnecessarilykillingbacteria,istodrythefood.Byremovingmoisturefromthefooditmakesithardformicroorganismstogrow.Thisistheprocessusedforfoodssuchasdriedsultanas,currants,apricotsandsoon,aswellaspowderedmilkandsundriedtomatoes.Sugar,asusedinjamsandfruitpreserves,alsodriesupanymoisture.'Smoking',wherefoodishungorpacedonarackoverasmoky,woodfire,isanothertraditionaltechniquefordehydratingmeatandfish.
Salting
Saltingisoneoftheveryoldestformsoffoodpreservation.Itisoftenusedincombinationwithdryingthefood,asisthecasewithdehydratedandsaltedmeatslikebeefjerky.Byreducingtheavailablewater,wemakeitdifficultforbacteria,yeastsandmouldstogrow.However,certainlacticacidbacteria,yeastsandmouldscaneithertolerateoradapttomoderatesaltlevelsandstillgrow,causingfoodspoilage.Saltinggenerallydoesnotkillbacteria,sosalted,rawfoodsshouldstillbecookedbeforeeating.
Acid
Acidfoods(measuredasalow'pH'value)alsomakeitdifficultfororganismstogrowandmultiply.ManufacturerswilloftenusevinegarorcitricacidtoturnfoodsfromalkalineorneutralintoamoreacidicpH.
TIPDon'tthinkfoodissaferbecauseitisspicier.
Curriesaresaferfromthelongcookingtime,notthespices.
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Spices
Inthemain,spicesdolittletopreservefood,actingprimarilytooverpoweranyunpleasanttastesthatmightdevelopasthefoodgetsolder.However,sometraditionalspices,includingchilli,cinnamon,cloves,garlicandmustardseeds,dohaveamildpreservativeaction.
Alcohol
Alcoholisapreservative.Youmighthaveseenfruit,suchasprunes,keptinajarwithalcohol:itimpartstheflavouroftheliquoraswellaspreservingthefruit.FruitcakesandChristmaspuddingsalsobenefitfromalittlealcohol,althoughthecooking(heat)andhighsugarcontent(fromthedriedfruits)alsoplayapart.
ArtificialPreservatives
Oneofthecommonandbestknownartificialpreservativesissulfurdioxide.Asusedwithfoodsfromprawnstodriedapricotsandwine,itisaveryeffectivepreservative,butpeoplewhosufferfromasthmamaybeunluckyenoughtoexperienceanasthmaattackbroughtonbyeatingfood,oropeningacontainerorpackoffood,preservedusingthiscompound.
Manysalamisusenitratesandnitritesaspreservativesandtogiveapinkcolour(theycanalsobepartofthe'curing'processforhams).Someartificialpreservativeshavelittleornothingtodowithmakingfoodsafe:rather,theyareusedtomaintainadesirableandattractivetaste,textureandappearanceofthefoodsoverthelongperiodfromprocessingtoeventualconsumption.
Manyconsumers,however,wouldrathernothavesomeofthesearguablyunnecessaryadditives.Insomecasespeoplehavefoundtheirhealthorthehealthorbehaviouroftheirchildrenhasimprovedonceartificialadditivesareremovedfromthenormaldiet.
Whenyoueat,doyousometimesfeeldiscomfortandbloatedwithgaswhichsmellslikerotteneggs?GailVines,in'AGutFeeling'inNewScientistforAugust1998,reportedresearch,byJohnCummingsandothersattheDunnNutritionUnit,Addenbrooke'sHospital,Cambridge,lookingataharmfulroleforsulfurdioxide.Thisresearchindicatedthatdietshighinsulfurouscompoundslotsofmeat,takeawayfoods,beer,wine,cider,driedfruitsandmanyotherprocessedfoodscanencouragebadbacteriatoflourishintheintestine,pushingasidetheessentialgoodbacteriaweneedtogenerateprotectivesubstances.Thesuggestionisthatsomegutdiseaseandillness,fromcolitisandCrohn'sdiseasetoirritablebowelsyndromeandpossiblycoloncancer,mightbeencouraged,maintainedoratleastnotpreventedbythesebacteria.Researchcontinuesinthisarea.
UltravioletLight
Ultravioletlightisapurplishlightfromoneendofthelightspectrum:lookforitabovetherowsofhamandslicedmeatsinyourdelicatessen.Itisoflimiteduse,butwillkillsomebacteriaonthesurfaceoffoodshitdirectlybythislight.ItisusedeffectivelyagainstListeriamonocytogenes.
Irradiation.
Radiationkillslivingthings,includingbacteriaandinsectsinfood,andcanstopthemreproducing.Thisisthesimpleideabehindtheprocessofirradiationusingtheradioactiveelementcobalt60.Itcanbeusedondriedfoodssuchasriceandspices,somemeat(hamburgermince),chicken,prawnsandsomefruitandvegetablessuchasstrawberriesandmushrooms.WhilefoodirradiationisnotpermittedinAustraliaatpresent,someimportedfoods,suchascertainprawnsandspices,mayhavebeenirradiated.
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VacuumPacking
Vacuumpackingisonewaywemakelifedifficultforthosetypesofbacteriawhichrequireoxygen.Whensomefoodsarecanned,theairissuckedoutofthecontainerjustbeforethelidissealed.Inthecanningindustry,heattreatmentusuallyfollows,andthesealed,airlesscanisheatedtoahightemperature.Foodsarealsosealedinplasticbags,thenvacuumpacked.
Antibiotics
Justasweuseantibioticmedicinestostopthespreadofabacterialinfectioninourbodies,sodofoodmanufacturersintheirfoods.Cheeseandcrumpets,forexample,relyontheantibioticNisin.
GeneticEngineering
Althoughnotnecessarilyanaidinthefightagainstfoodpoisoning,researc