BASIC FOOD MICROBIOLOGY

(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. Equipmen

ts

1. PLANTS 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.

2. ANIMALS  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.

3. AIR  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.

4. SOIL 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.

5. SEWAGE  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.

6. WATER 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.

7. HUMAN 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.

8. EQUIPMENTS 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.