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Bacteria grow rapidly, if we have a basic understanding of the ideal conditions bacteria need to reproduce then we’ll have a better understanding of how to control them.

The first of these conditions is Warmth the ideal temperature is around 37 degrees Celsius (around body temp) but they can grow between 20-50 degrees Celsius. 

This is the danger area and we need to make sure within food preparation we keep food out of this range.

One way of doing this is refrigeration and keeping the food stored around 1-4 degrees Celsius and making sure it’s regularly checked and monitored.

Freezing food is another method; freezing food at minus 18 degrees Celsius will prevent bacterial growth.

Heating foods can also kill bacteria but some bacteria produce spores and can remain active even after up to 5 hours of boiling, so we need to make sure everything we do reduces any possible risk of infection. 

Heating foods will kill bacteria and the higher the temperature the shorter the time required. Bacteria start to die at about 55 degrees Celsius but you need to have a core temperature of above 75 degree Celsius to be confident that most of the harmful bacteria in the food has been destroyed.

Even higher temperatures are needed to destroy toxins and spores produced by some of the bacteria types. Cooking processes like drying, boiling do not always kill the spores and these along with toxins can remain a hazard.

If we have to store food within the danger zone we can do this by preserving food by using an acid or alkaline solution or using sugar. Salt can also be used and is usually done in a salt solution of brine where salt is mixed with water.
If we're using any of these methods we must ensure it’s appropriate for the preserving that particular type of food.

Moisture is also needed for bacteria to survive and reproduce, removing moisture by drying foods can be a great way to control bacterial growth, for example, rice can be dried but can still hold dormant bacteria and when introduced to water the bacteria can start reproducing again.

Bacteria will grow on most foods, some foods are classed as high risk, these are generally protein-based foods such as:

  • Cooked Meats
  • Cooked poultry, Pates, gravy, soups, stews
  • Dairy products such as milk, cream, custard and soft cheeses
  • Eggs and egg products
  • Shellfish such as oysters crabs and prawns.

Outbreaks of food poisoning are usually in these high-risk categories.

The reason that low risk is un-cooked is that they still have to go through the cooking process, which will kill the bacteria. If we mix cooked and uncooked foods the bacteria from the uncooked food will easily reproduce when it comes into contact with the cooked food.

Ready to eat food such as fruits and vegetables can present problems with bacteria and viruses. Viruses only need to present in small doses in order to cause health issues.

If your dealing with any food mentioned in this category make sure it’s thoroughly washed and stored and the correct temperatures and that correct stock rotation is observed.