Lecture 3 (mic 204)

Sources of microbial contamination of
food
Prepared by: Hajar

Sources
of
microbes
in food
1. Plants
2. Animals
3. Air
4. Soil
5. Sewage
6. Water
7. Human
8.
Equipments

 The inside tissue of plant / animal is sterile.
 Some plants produce natural antimicrobial metabolites that can
limit the presence of microbes.
 Fruits and vegetables harbour microorganisms on their surface.
 The type and number varies with soil condition, type of
fertilizers and water used.
 Pathogens can be present if soil is contaminated with untreated
sewage.
 Disease plants, damaged plants during harvesting, unfavorable
storage condition can increase the number of microorganisms.

 Animals and birds carry many types of
microorganisms in the digestive system, in teat canal
/ udder, skin, hooves, hair and scales.
 Disease situation such as mastitis in cows can change
the ecology of the microflora.
 Poor husbandry can lead to fecal contamination.
 Milk can be contaminated with fecal material on the
udder surface.
 Meat contaminated with intestinal content of
animals.
 Eggs can be contaminated from the eggshell

Steps to prevent contamination of food:
 Good condition of animals and birds husbandry.
 Properly slaughter.
 Washing with clean water.
 Removal of digestive system without contaminating other
tissue.
 Proper sanitation during entire processing.
 Proper cleaning of udder before milking.
 Collecting of eggs soon after laying. Washed and stored using
recommended procedure.
 Fish and marine product should be harvested from unpolluted
water.

 Microorganisms present in the dust don’t grow
because of the arid condition.
 Their level is controlled by degree of humidity,
temperature, air velocity etc.
 Pathogens can be transmitted through air from
their spores.
 Microbial contamination from air can be reduced
by removing the potential sources, controlling
dust particles in the air (using filtered air), using
positive air pressure, reducing the humidity level
and installing ultraviolet light.

 Soil contains several varieties of
microorganisms. Soil is used to grow
agricultural product and raise animals.
 Microbes can get into food from soil and
multiply; their numbers can be very high.
 Soil contaminated with fecal material can be
the source of enteric pathogenic bacteria
and viruses in food.

 If used as fertilizers in crops,
microorganisms in sewage water can
contaminate food especially
enteropathogenic bacteria and viruses.
 Especially organically grown food and many
imported fruits and vegetables.
 Prevention:
 Avoid using sewage as fertilizer.
 Washing.
 Treat sewage to kill pathogens.

 Used to process, produce and store food.
 Others: irrigation, drinking, washing, canning
and freezing.
 Also used as ingredients in many processed food.
Therefore, water quality is greatly influence the
microbial quality of foods.
 Chlorine treated potable water should be used in
processing, washing, sanitation etc. because
improperly treated water can contain pathogen
and spoilage of microorganisms.

 Food come in contact with different people handling the foods, such as people processing the
food, food handlers in restaurants, catering services, suppliers and producers.
 Human has been the source of pathogenic microorganisms in foods that later caused food borne
diseases especially ready to eat foods.
 Factors affecting:
 Improperly clean hands.
 Lack of personal hygiene and aesthetic sense.
 Dirty clothes and hair.
 Presence of minor cuts.
 Infections on hands and face.
 Mild generalized diseases e.g.: flu and throat infection
 Prevention:
 Proper training of personnel in personal hygiene.
 Regular check up.
 Maintain efficient sanitary.

 A wide variety of equipment is used in
harvesting, processing, transportation and
storage of foods.
 Many types of microorganisms from air, raw
foods, water and personnel can get into the
equipment and contaminate foods.
 When processing equipments are used
continuously for a long period of time,
microorganisms present initially can multiply
and act as a source of contamination.

Lecture 3 (mic 204)

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Lecture 3 (mic 204)