Lesson 2: How Food and Produce Become Contaminated

Extrinsic and Intrinsic Factors

There are two factors that contribute to food contamination, extrinsic and intrinsic factors.

Extrinsic factors relate to the environmental factors that affect the growth rate of the microorganism.  These include:

• Temperature
• Oxygen availability
• Relative humidity

Intrinsic factors relate more to the characteristics of the substrate (food or debris) that support or affect the growth of the organism(s).  These include:

• Water activity (aw)
• Oxidation reduction potential
• Nutrient requirements
• Inhibitory substances

Biofilms

Biofilms are another cause of contamination of food.

Biofilms are matrices of microbial cells irreversibly adhering to a surface and encapsulated by a polysaccharide matrix.  An example of a biofilm is the plaque on your teeth.

• A biofilm is a preferred lifestyle for bacteria in the environment that can harbor and be a source of pathogens.
• Persistent biofilms can shed bacterial contamination on a product and be a major problem in food processing facilities.
• Biofilms are more resistant to conventional cleaning and sanitation processes.
  • Biofilms need to be scrubbed, not just washed.
• Specialty products and procedures may be required for remedial removal.
• Water quality can affect cleaning ability to remove biofilms.
  • Hard water vs. soft water.
  • May need water softeners or use a reverse osmosis process for water treatment.

Answer this multiple choice question to help your understanding.

Workers/Employees and Animals

Workers/Employees and Animals are additional causes of food contamination.

Workers:

• Can carry human pathogens.
  • Shigella, Hepatitis A, Norovirus, and others.
• Can spread human pathogens.
  • Harvest or pack food with their hands.
  • Lack of proper personal hygiene; e.g. not washing hands after using the bathroom (fecal-oral route).
• Require training to reduce risks.
  • Proper hand washing.
  • How to handle illnesses and injuries.

Animals:

• Can carry human pathogens.
  • e.g. E. coli O157:H7, Salmonella, Listeria monocytogenes.
• Can spread human pathogens
  • By depositing feces in fields.
  • By spreading fecal contamination as they move.
  • By leaving their droppings in facilities (rodents)
• Are very difficult to control.
  • Birds and small animals travel unnoticed.
  • If fencing is used, even the best fence can be breached.
  • Complete exclusion is not possible from fields.
  • Exclusion from facilities can be accomplished with a good pest control program.