Fact Sheet 3: Preventing Food Poisoning – Bacterial Growth
We can control the growth of bacteria by controlling the conditions they need in order to survive and grow to dangerous levels.
These conditions are
- Food (to grow on)
- pH (level of Acidity)
Food can become unsafe for human consumption if harmful bacteria multiply on the food. When high-risk food is stored at the incorrect temperature for too long, bacteria can increase to dangerous levels, these bacteria can then produce toxins that cause food poisoning.
Cross-contamination from high-risk foods, raw food or unhygienic handling can also cause food poisoning.
Dangerous substances can contaminate food this can be caused by chemicals (such as cleaning agents, detergents and pesticides) and other things that should not be in food (such as dirt, hair, glass or stones).
The risk of food becoming unsafe in your business will depend on the types of food you sell and how you and others in the business store, prepare and handle food. What are ‘high-risk’ foods? High Risk Foods can be:
Time Control – Bacteria grows quickly in the ‘Danger Zone.’
Food held at room temperature (which is in the temperature danger zone of 5°C to 60°C) for long periods of time can cause spoilage and bacteria to grow quickly to large numbers in the food. This can cause gastro-type illnesses. Below you can see that both time and temperature contribute to bacteria growth.
The 2 hour / 4 hour rule provides a way of monitoring the time that high-risk foods spend in the temperature danger zone of 5°C to 60°C, to limit the risk of it becoming unsafe.
The rule provides the following steps:
The 2 / 4 HOUR RULE…..
If food has been in the danger zone for:
- Less than 2 hours … it’s safe to put back in the fridge
- More than 2 hours … use but DON’T put back in the fridge
- 4 hours………………. THROW IT OUT
Before using this rule, check:
- Is the food a high-risk food?
- Was the food previously kept at room temperature? If so for how long?
- Are your refrigerators working correctly?
- If this food was cooked and cooled, can you prove that it was done in line with the cooling rules?
- Are staff members familiar with the Food Safety Program instructions and use of the record sheets?
- Have you informed staff members about this rule? Do they know how to use it?
- If food is not eaten on the premises, how will you inform customers that it must be eaten within 4 hours?
- Place a label on the food or the tray to record the time it spends at room temperature.
- When preparing raw high-risk food for cooking, make sure that the time it is held at room temperature is kept to a minimum. Return food to the refrigerator during delays.
- Record on the time log if food is placed back in the refrigerator.
- Record on the time log how much food was disposed of.
Important temperatures to know:
To cool foods safely use the correct methods to cool food to 21°C in 2 hours,
then you can put food in the fridge to cool to 5° or colder within the next 4 hours.
One can use preserving methods that remove oxygen, as most bacteria will not grow without oxygen.
These methods include:
- Vacuum packing
- Covering with oil
Vinegar and other food acids are used to preserve food.
Common pickled foods include olives, cucumbers, peppers, corned beef, herrings as well mixed vegetables such as piccalilli or anti pasta.
Sushi is example of pH control.
Sushi products are prepared using vinegar as this lowers the pH and can protect against bacteria. However this must be done correctly, following the correct recipe.
Keep in mind that fruit and vegetables need to be washed before use.