Food contamination

• Micro-ops are everywhere
• They are present in the air, in the water and even on the human body
• They are found in abundance on animals and in plants that we use as food
• They contaminate crops during harvesting and storage in silks and bulk grain bins
• They occur on utensils and work surfaces used for food preparation
• They can be carried through the air from one object to another
• Food may become contaminated during growth, harvesting, storing and preparation processes
• Microbial contamination


  Contamination occurs when micro-organisms such as bacteria, parasites and viruses find their way into a food product
• A food may taste and smell perfectly safe but contains enough microbes to make you sick
• Cooking the food before eating will always make it safe
• Cooking will destroy Salmonella bacteria, but Staphylococcal bacteria are heat resistant and the food needs to be cooked for several hours to destroy this toxin
• If you are not sure how safe food is, throw it out without tasting it
• Signs of microbial contamination

  • Smell - food may develop an unpleasant smell as bacteria start to break down the proteins
  • Sliminess - food becomes covered with an unpleasant jelly
  • Discolouration - food can become discoloured, for example vacuum-packed meat may develop a pinkish-yellow colour and fresh meat may show greenish streaks
  • Gas - bacteria often produce gas that can affect the food, for example, cans of food, especially fish and meat, swell and make a hissing sound when opening
• Common contributors to microbial contamination


  • Food stored too far in danger zone temperature (above 5°C)
  • Food not cooled or heated quickly enough
• Danger zone temperature

  Temperature range where bacteria can grow rapidly, usually between 5°C and 60°C
• How to prevent microbial contamination

  • Store high risk food at 5°C or below, use a fridge and monitor temperature
  • Do not store high-risk food at room temperature for more than 4 hours
  • Cool food quickly in small batches
  • Heat food quickly to over 80°C to destroy bacteria