Bacterial Contamination (AQA GCSE Food Preparation & Nutrition)
Revision Note
Written by: Naomi Holyoak
Reviewed by: Lára Marie McIvor
Bacterial contamination of food
Food that has been contaminated by harmful bacteria can cause illness
Examples of types of bacteria that can cause illness, and common sources of these bacteria, include:
campylobacter
Raw poultry and other meat, and untreated water and milk
e-coli
Raw beef, untreated water / milk and unwashed salad
salmonella
Raw poultry and untreated milk / eggs
listeria
Soft cheese, pâté and shellfish
staphylococcus aureus
Human / animal hair and skin
There are multiple ways in which food can become contaminated with harmful bacteria, as well as techniques that should be used to reduce the risk of contamination:
Source of contamination | Explanation | Prevention |
---|---|---|
Other food | Bacteria may be transferred directly from contaminated raw meat, eggs, seafood or vegetables |
|
Surfaces or equipment | Bacteria may be transferred to food from improperly cleaned surfaces or equipment |
|
Person preparing food | People may have contaminated hands from touching other items, or they may have a bacterial infection that transfers to food from their hands or during coughing or sneezing |
|
Animal pests | Animals, such as rodents and insects, may transfer bacteria to food from their bodies, or via bodily waste such as urine or faeces |
|
Waste food and rubbish | Bacteria can be transferred to food from food waste bins and rubbish bins |
|
In addition to the contamination prevention methods described in the table, other risk-reducing procedures involve:
ensuring that food is heated to a high enough temperature during cooking to kill any bacteria
at-risk groups, such as the very young/old and pregnant women, avoiding high risk foods
food being served immediately after cooking or stored in a fridge / freezer
pasteurising milk, meaning that it is heated to a high temperature to kill bacteria, before it is sold in shops
vaccinating chickens against salmonella
Food poisoning
Eating food that has been contaminated by harmful bacteria can result in food poisoning
General symptoms of food poisoning include:
vomiting
nausea
diarrhoea
stomach pain
fever
Serious cases can result in death, especially in vulnerable individuals
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