Microbial contamination of foods

Different sources of food contamination

1. BY
Dr. A. FreedaRose
Assistant Professor
Department of Botany
Holy Cross College
Tiruchirappalli
MICROBIAL CONTAMINATION OF FOODS

2. MICROBIAL CONTAMINATION OF FOODS
Definition–FoodMicrobiology
“Thestudyofmicroorganismsassociated
withfood,foodspoilageandfoodpoisoning
andtheirroleinwelfareofhumanbeingsboth
inharmfulandusefulways”

3.  Allfooditemsareassociatedwithmicroorganisms
inoneorotherform
 Evennaturallyoccurringfoodsuchasfruitsand
vegetablescontainmicroorganisms
 Foodgetscontaminated
–Duringhandling
–Harvesting
–Methodsofcookingandpreparation
–Storingandpreparedfoods

4. Microbial contamination of Foods –
Sources and factors
Growing plants carry a typical flora of microorganisms
on their surfaces and may become contaminated
from outside sources
Animals have a typical surface flora plus an intestinal
one given off organisms in excretions and secretions
and also become contaminated from various outside
sources.

5. Microorganismsfromvariousnatural
sources
Fromgreenplantsandfruits
FromAnimals
Fromsewage
Fromsoil
Fromwater
Fromair
Duringhandlingandprocessing

6. I.FROMGREENPLANTSANDFRUITS
–Thenaturalfloraofplantsvarieswiththe
plantbutusuallyincludesspeciesof
•Pseudomonas,
•Alcaligens,
•Flavobacterium,
•Micrococcus
•Lacticacidbacteria(Lactobacillusbrevis,L.plantarum,
Leuconostocmesenteroides,Leuconostocdextranicum,
Streptococcusfaecium,andStreptococcusfaecalis).

7. –Thenumberofbacteriawilldependontheplantand
itsenvironmentandmayrangefromafewhundred
(or)thousandspersquarecentimeterofsurface.
–Thesurfaceofawellwashedtomatomayshow400
to700microorganismspersquarecentimeter,while
unwashedtomatohasseveralthousandsofmicrobes.
–Anoutertissueofunwashedcabbagemightcontain1
millionto2millionsmicroorganismspergram,but
washedcabbagecontains200,000to500,000.

8. –Theinnertissueofthecabbagecontainsfewerkinds
andnumberrangingfromafewhundredto1,50,000
pergram.
–Somefruitshavebeenfoundtocontainviable
microorganismsintheirinterior.
–NormalhealthytomatoescontainPseudomonas,
Coliforms,AchromobacterMicrococcusand
Corynebacteriumandyeastshavebeenfoundinside
undamagedfruits.

9. II. FROM ANIMALS
•Sources of microorganisms from animals include the surface flora,
the flora of the respiratory tract and flora of the gastrointestinal
tract.
•The natural surface flora of meat animals usually is not important
as the microbes from intestinal (or) respiratory tract.
•Feathers from animals and feet of poultry carry heavy
contaminations from soil.

10. •The skin of many meat animals may contain Micrococci,
Staphylococci, and beta hemolytic Streptococci
•Staphylococcion the skin (or) from the respiratory tract may
enter on carcass and then to the final raw products.
•The faces and fecal contaminated products of animals can
contain many enteric organisms including Salmonella
•Salmonellosis in animals can result in contamination of animal
products and contaminate the foods.

11. PigandbeefcarcassesmaybecontaminatedwithSalmonella.
Becauseoffurtherprocessingandhandling.
Meatfromslaughteredanimalsisnotfrequentlyassociatedwith
humanSalmonellosis
Statisticsinrecentyearsreportedeggsandeggproductscause
Salmonellosisinhumanmuchmorefrequently.
Salmonellosisassociatedwitheggshasbeenreducedbecauseofthe
pasteurizationofeggproducts.

12. III .FROM SEWAGE
Whenuntreateddomesticsewageisusedtofertilizeplantcrops,the
rawplantfoodwillbecontaminatedwithhumanpathogens
especiallythosecausinggastrointestinaldiseases.
Inadditiontothepathogens,Coliformsbacteria,Enterococci,
intestinalbacteriaandvirusescancontaminatethefoodsfromthis
source.
Naturalwaterscontaminatedwithsewagecontributetheir
microorganismstoshellfish,fishandseafoods.

13. IV. FROM SOIL
Thesoilcontainsthegreatestvarietyofmicroorganismsof
anysourceofcontamination.
Notonlynumerouskindsofmicroorganismsbutalsolarge
totalnumberofmicroorganismspresentinfertilesoil
readytocontaminatethesurfaceofplantsgrowingin
themandsurfacesofanimalsroamingovertheland.

14. Soildustiswhippedbyaircurrentsandsoilparticles
arecarriedbyrunningwatertogetintofoods.
Thesoilisanimportantsourceofheatresistantspore
formingbacteria.Variouskindsofyeasts,moldsand
bacterialspeciesareBacillus,Clostridium,Enterobacter,
Micrococcus,Chromobacterium,Escherichia,
StreptococcusandAcetobacter

15. V. FROMWATER
Naturalwatercontainnotonlytheirnaturalflorabutalsomicroorganismsfrom
soilandpossiblyfromanimalsorsewage
Surfacewatersinstreamsorpoolsandstoredwaterinlakesandlargeponds
varyconsiderablyintheirmicrobialcontentfrommanythousandspermilliliter.
ThekindofbacteriainnaturalwatersarechieflyspeciesofPseudomonas
Chromobactrium,Proteus,Micrococcus,Bacillus,Streptococcus,Enterobacterand
Escherichia.
Contaminationoffoodmaycomefromwaterusedasaningredient,forwashing
foods,forcoolingheatedfoodsandmanufacturediceforpreservingfoods

16. Thegasformingcoliformbacteriamayentermilkfromcooling–tank
waterandcausetroubleincheesemadefromthemilk.
Cannerycoolingwateroftencontainscoliformandotherspoilage
bacteriathatentercannedfoodsduringcooling.
Thebacteriumcausingthesurfacetaintofbutter,Pseudomonas
putrifacienscomesprimarilyfromwater.
Thebacterialfloraofcrushedicetobeappliedtofish(or)otherfood
consistsmostlyofCornybacterium,Alcaligens,Flavobacterium,
Pseudomonas,andCocci.

17. VI. FROM AIR
Airdoesnotcontainanaturalfloraofmicroorganisms,forallthatarepresent
havecometherebyaccidentandusuallyareonsuspendedsolidmaterials
(or)inmoisturedroplets
Microorganismsgetintoairondustorlint,drysoil,sprayfromstreams
,lakes,oceans,dropletsofmoisturefromcoughing,sneezingortalking
Itispossibleforanykindofbacteriumtobesuspendedinair,especiallyon
dustparticlesorinmoistdropletsbutsomekindsaremorecommonlyfound
inair.Cocciareusuallymorenumerousthanrodshapesbacteria.
Moldspores(Fungi),becauseoftheirsmallsize,resistanttodrying,andlarge
numberofsporesinfungiareusuallypresentinair.

18. VII. DURING HANDLING AND PROCESSING
Inadditiontoabovementionedsourcesadditionalcontamination
maycomefromequipmentscomingincontactwithfoods,from
packagingmaterialsandfrompersonnel
Personnelinfoodprocessingplantscancontaminatefoodsduring
handlingandprocessing
Theprocessorattemptstocleanandsanitizeequipmenttoreduce
suchcontaminationstoemploypackagingmaterialsthatwill
minimizethecontamination.