Biological Hazards

Biological hazards are organisms, or substances produced by organisms, that pose a threat to human health. They are a major concern in food processing because they cause most food borne illness outbreaks.  

Major biological hazards  

  • Bacteria (ex: Salmonella spp., Enterohaemorrhagic Escherichia coli, Campylobacter jejuni, Yersinia enterocolitica, Listeria monocytogenes, Bacillus anthracis, Bacillus cereus, Staphlococcus aureus, Clostridium botulinum, Clostridium perfringens, Vibrio vulnificus, Vibrio parahaemolyticus)  
  • Virus (ex: hepatitis A virus, Norwalk viruses, Rotavirus)  
  • Parasites (ex: Toxoplasma gondii, Cryptosporidia, Giardia spp., Trichinella spiralis, Taenia solium, Anisakis spp.)


These organisms can affect human health, including infection, intoxication and even death. Infection occurs when organisms invade the host and multiply in the body. Intoxication occurs when bacteria produce toxins that affect the body.  

Infection can be prevented by properly processing and handling food products because pathogens are easily destroyed by heat. However, some bacteria that produce spores can survive cooking temperatures. For example, steam cooking significantly reduces non-spore-forming food borne pathogens, but only inactivates spores. Examples of spore forming bacteria include Bacillus cereus, Clostridium botulinum and Clostridium perfringens.

Bacteria must first grow in the food before producing toxins. These toxins are very difficult to eliminate. They survive normal cooking temperatures and even temperatures higher than 80°C (176°F).  The risk of intoxication is prevented by controlling the growth of toxin producing bacteria. These include: Clostridium botulinum, Bacillus cereus, and Staphylococcus aureus.


The major sources of biological contaminants in food are:

  • animal guts: faecal contamination
  • soil and water contaminated by non-treated manure
  • cross contamination:
    • human contamination due to poor personal hygiene (skin, clothing, especially hands), faecal contamination (human guts), failure in infection control (illness not reported)
    • Cross-contamination of food products spread from processing environment due to poor/improper sanitation  

Factors affecting the growth of microorganisms in foods

Most foods contain sufficient nutrients to support microbial growth. The most important factors that affect microbial growth are:

  • The temperature values for microbial growth depend on the type of microorganism. For example, psychrotrophs such as Listeria monocytogenes grow at refrigeration temperature (4°C or 39°F), while thermotrophs can grow at higher temperatures (45°C or 113°F).
  • The pH of a product is related to the acidity or alkalinity of the product. The pH of products affects the growth of bacteria. Most bacteria grow in on a pH range between 5 and 9.
  • The Water Activity (Aw) refers to the water available in the product. The more water available, the better bacteria will grow.  Table 1 shows the impact of water activity on bacterial spoilage.
Aw of product Bacterial Spoilage Examples
>0.90 spoils easily Fresh vegetables, fresh meat, processed meat, milk, fish
0.78-0.90 susceptible to spoilage dry cheeses, flour, cakes, beans, cereals
<0.78   little bacterial spoilage but mold may grow rolled oats, dried fruits, caramels, dehydrated foods

Each of these factors is important for the control of microbial growth. It is the interaction among these factors that determines the growth or control of micro-organisms.

Factors affecting the growth of food borne pathogens such as temperature, pH and Aw can be found in the Foodborne Pathogens Booklet (PDF 1.03 MB) published by MAFRD.

Control and prevention

The most effective way to control biological hazards is by prevention. Potential biological hazards need to be identified and the risk of microbial growth assessed. The implementation of Good Manufacturing Practices (GMPs) and Hazard Analysis and Critical Control Point (HACCP) will help prevent biological hazards in your facility. GMPs ensure hazards associated with personnel and environment are controlled during food production. HACCP controls hazards that may be present in ingredients and packaging materials and also those that occur during food processing, packaging and storage.

Processing strategies to control biological hazards:

  • effective thermal processing used as a kill step (ex: cooking, pasteurization)
  • use of appropriate process controls:
    • storage temperatures (ex: cooler, freezer)
    • processing parameters (ex: temperature and time for cooking, water activity during dehydration)
    • adequate cooling system
  • effective cleaning and sanitizing procedures (ex: Sanitation Standard Operating Procedures (SSOPs))
  • use of food technologies to prevent the growth of bacteria or other biological hazards:
    • packaging techniques (ex: use of vacuum packaging, modified atmosphere packaging)
    • preservatives
    • processing techniques (ex: dehydration)


  • Micro-organism and toxins are detected using several methods.
  • A list of labs that test for bacterial hazards is posted on MAFRD's website.
  • A list of suppliers of microbial rapid tests is provided under the Analytical Testing section of MAFRD's website.

Related Links

The USDA Food Safety & Inspection Service (FSIS) and the USDA Agricultural Research Service (ARS) have produced the Predictive Microbiology Information Portal (PMIP) to assist small and very small food companies in the use of Predictive Models and Food Microbiology information. The PMIP is especially useful for locating and retrieving predictive models and research data for use in HACCP systems.  


Lee, S.Y., Chung, H.J., Shin, J.H., Dougherty, R.H., Kang, D.H. 2006 Survival and growth of food borne pathogens during cooking and storage of oriental-style rice cakes. Journal of Food Protection. 69(12): 3037-3042.

Peck,M.W., Lund, B.M., Fairbairn, D.A., Kaspersson, A.S., Undeland, P.C. 1995.  Effect of heat treatment on survival of, and growth from, spores of nonproteolytic Clostridium botulinum at refrigeration temperatures. Applied-and-Environmental-Microbiology. 61(5): 1780-1785.

For more information, email the CVO/Food Safety Knowledge Centre or call 204-795-8414 in Winnipeg.