Source of Microorganism in Food

MIKROBIOLOGI PANGANSEKOLAH ILMU DAN TEKNOLOGI HAYATI - ITB

IntroductionMicroorganisms get into foods from:

Natural (including internal) sources• Plant origin : the surfaces of fruits, vegetables, and

grains; the pores in some tubers.• Animal origin : skin, hair, feathers, gastrointestinal

tract, urogenital tract, respiratory tract, and milk ducts (teat canal) in udders of milk animals.

• Microbial types and levels vary greatly with the type of plants and animals , their geographical locations and environmental conditions

External sources to which a food comes into contact ( from production to consumption)• Include: air, soil, sewage, water, feeds, humans,

food ingredients, equipment, packages, insects, etc.

• Depend on the degree of sanitation used during the handling of foods

An understanding of the sources of microorganisms in food is important to:

• develop methods to control access of some microorganisms in the food,

• develop processing methods to kill them in food,

• determine the microbiological quality of food,

• set up microbiological standards and specifications of foods and food ingredients.

Source of microorganism in food

SoilWater and

Sewage

Animals, Birds, Fish, and Shellfish

Plants

(fruits and vegetables)

Humans

Air and dust Food Ingredients Equipment Miscellaneous

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1. Plants (fruits and vegetables)Fruits and vegetables harbor microorganisms on the surface. Microorganisms expected from this source: Pseudomonas, Alcaligenes, Micrococcus, Erwinia, Bacillus, Clostridium, Enterobacter.

Some plants produce natural antimicrobial metabolites that can limit the presence of some microorganisms

Factors increasing the microbial numbers and the predominant types:

• Diseases of the plants,

• damage of the surface (before, during, and after harvest),

• long delays between harvesting and washing,

• unfavorable storage and transport condition after harvesting and before processing,

• improper storage conditions following processing

Factors reducing microbial load in foods of plant origin:

• Proper methods used during growing (such as use of treated sewage or other types of fertilizers),

• damage reduction during harvesting,

• quick washing with good quality of water to remove soil and dirt,

• storage at low temperature before and after processing

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2. Animals, Birds, Fish, and Shellfish

Normal/Indigenous microorganisms• Food animals and birds normally carry many types of indigenous microorganisms in the

digestive, respiratory, urogenital tracts, skin, hair, and feathers

• Fish and shellfish also carry normal microflora in the scales, skin, and digestive tracts

• Their numbers can be very high (large intestinal 1010 cfu/g)

• Many can carry pathogens: Salmonella spp, E. coli, Campylobacter jejuni, Yersinia enterocolitica (without showing symptoms)

• Situation that can change the ecology of normal microflora:

• Diseases such as mastitis in cows and intestinal, respiratory, and uterine infections

• Injury

• poor husbandry resulting in fecal contamination of body surface (skin, hair, feather, udder)

• supplying contaminated water and feed (e.g., contaminated with salmonellae)

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2. Animal (cont)External/ contamination microorganisms

• Water quality, feeding habits, and diseases can change the normal microbial types and level in fish and shellfish. Pathogens such as Vibrio parahaemolyticus, Vib. vulnificus, and Vib.cholerae are of major concern from these sources.

• Many spoilage and pathogenic microorganisms from fecal material ( enteric pathogens) can get into foods of animal origin (milk, egg, meat, and fishery products) during production and processing

• Milk can be contaminated with fecal materials on the udder surface,

• Egg shells with fecal material during laying,

• Meat with the intestinal contents during slaughtering,

• Fish with intestinal contents during processing.

• Meat from food animals and birds can be contaminated with several spoilage and pathogenic microorganisms from skin, hair, and feathers, (Staphylococcus aureus, Micrococcus spp., Propionibacterium spp., Corynebacterium spp., and molds and yeasts).

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2. Animal (cont)

• The use of effective husbandary of the live animals and birds

• Testing animals and birds for pathogens

• Use of good quality water for wahing carcasses

• Care in removing digestive, urogenital, and respiratory organs without contaminating rissues

• Proper sanitation during the entire processing stage

• Fish and marine products shoud be harvested from unpolluted and recommended water

• Proper storage to prevent further contamination and microbial growth

Prevention of food contamination:

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3. Air and DustMicrobes are present in dust and moisture droplets in the

air.

• They do not grow in dust, but are transient and variable, depending on the environment.

• Their level is controlled by the degree of humidity, size and level of dust particles, temperature and air velocity, and resistance of microorgansims to drying.

• Dry air with low dust content and higher temperature has a low microbial level

Predominant microorganisms:

• Spores of Bacillus spp., Clostridium spp., molds, yeasts, and some Gram-positive bacteria (Micrococcus, Sarcina)

• Pathogens and viruses (incl. bacteriophages), can be transmitted via the air if the surroundings contain a source of pathogens (e.g., animal and poultry farms or a sewage-treatment plant)

Microbial contamination of food from the air can be reduced by:

• removing the potential sources, • controlling dust particles in the

air (using filters air), • using positive air pressure, • reducing humidity level, • installing UV light

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4. Soil• Soil, especially the types used to grow agricultural produce and raise

animals, contains several varieties of microorgansims (≥ 106 cfu/g)

• Molds, yeasts, and bacterial genera found in soil: Enterobacter, Pseudomonas, Proteus, Micrococcus, Enterococcus, Bacillus, Clostridium, etc

• Soil contaminated with fecal materials can be the source of enteric pathogenic bacteria and viruses in food

• Sediments where fish and marine foods are harvested can also be a source of microorganisms, including pathogens in those foods

• Removal of soil (and sediments) by washing and avoiding soil contamination can reduce microorganisms in foods from this source.

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5. Water and Sewage

Water

• Water quality can influence the microbial quality of food

• Producing: irrigation of crops, drinking by food animals, raising fishery and marine product, washing foods

• Processing: pasteurization, canning, and cooling of heated foods, etc

• Storing: storage of foods, e.g. Fish on ice

• Potable water does not contain coliforms and pathogenss, but it can contain other food spoilage bacteria : Pseudomonas, Alcaligenes, Flavobacterium.

• Water used for food processing has higher microbial quality than potable water

Sewage

• Sewage, especially when used as fertilizer in crops, can contaminate food, especially enteropathogenic bacteria and viruses→major concern with organically grown food and many imported fruits and vegetables, in which untreated sewage and manure might be used as fertilizer.

• To reduce incidence of microbial contamination of foods from sewage:

• It is better not to use sewage as fertilizer.

• If used, it should be efficiently treated to kill the pathogens.

• Effective washing of foods following harvesting is important.

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6. Humans

Human carriers have been the source of pathogenic microorganisms in foods, especially with ready-to-eat foods.

Improperly cleaned hands, lack of aesthetic sense and personal hygiene, and dirty clothes and hair can be major sources of microbial contamination in foods.

Infection in hands and face and mild generalized diseases (e.g. Flu, strep throat, and hepatitis A in an erly stage) can amplify the situation

In addition to spoilage bacteria, pathogens such as Salmonella spp., Staphylococcus aureus, Shigella spp., E. coli, Hepatitis A, etc. can be introduced into foods from human source

Proper training of personnel in personal hygiene, regular checking of health, and maintaining efficient sanitay and aesthetic standards → reduce contamination

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7. Food IngredientsMany ingredients or additives can be the source of both spoilage and pathogenic microorgansims

• Various spices generally have very high populations of mold and bacterial spores

• Starch, sugar, and flour can have spores of thermophilic bacteria

• Pathogens have been isolated from dried coconut, egg, and chocolate

The ingredients shoud be produced under sanitary conditions and given antimicrobial treatments.Setting up acceptable microbial specifications for the ingredients will be important in reducing microorganisms from this source

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8. Equipment

Used in harvesting, transportaion,

processing, and storage of foods.

Microorganisms from air, raw foods, water and

personnel can ge into the equipment and

contaminate foods

Level of microorganisms depends upon the

environment (moisture, nutrients, and

temperature) dan time

Dead spot can serve as source of both

pathogenic and poilage microorganisms in food

Cutting boards, knives, spoons, and similar

articles can be the source of cross-contamination

Proper claning and sanitation at prescrived

intervals → reduce microbial level

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9. Miscellanous

Foods may be contaminated with microorganisms from several other sources: wrapping materials, containers, flies, birds, pets, and rodents

Packaging materials used in ready-to-eat-foods should be in good quality

Flies, birds, and rodents in food processing and food preparation facilities → source of pathogenic microorganisms