Food contamination happens when something gets into food that shouldn’t be there, rendering it unsafe to eat. Contaminated food can have dire consequences for the person who eats it, and for the business who sold it.
There are four main types of food contamination:
Serving contaminated food can lead to food-borne illness outbreaks, allergic reactions and injuries. Food Handlers must be aware of the risks of food contamination, as well as complete training to handle food safely, practise good personal hygiene and prevent cross-contamination, which is the transfer of contaminants, to protect customers and the food establishment.
Learn more about each type of contamination, how they happen, and ways to prevent them.
Biological contamination is when disease-causing bacteria or other harmful microorganisms called “pathogens” contaminate food and are consumed; it is a common cause of food poisoning and food spoilage. Bacteria are small microorganisms that split and multiply very quickly. In conditions ideal for bacterial growth, one single-cell bacteria can become two million in just seven hours.
Certain types of bacteria also produce bacterial toxins in the process of multiplying and producing waste. Bacterial toxins can be very dangerous. In fact, botulinum, the bacterial toxin that causes botulism, is the most potent natural poison known.
It's important to remember that all foods can harbour dangerous pathogens.
Norovirus, for example, doesn't grow or multiply on food, but it can survive for days or even weeks on any type of food and is a leading cause of food-borne illness in Australia.
HIGH-RISK FOODS
Certain foods are more vulnerable to biological contamination than others because they provide everything bacteria need to survive and multiply - food, water and neutral acidity (pH). These are called high-risk foods.
When high-risk foods are left in the Temperature Danger Zone (5ºC-60ºC) for too long, Food Handlers provide the other conditions bacteria need to grow - time and the right temperature. To slow down bacteria growth and minimise the risk of biological food contamination, Food Handlers must always follow safe food handling practices:
Chemical contamination occurs when chemicals get into food. Common sources of chemical contamination in a commercial kitchen include:
Physical contamination happens when physical objects enter food. Common sources of physical contamination include:
In a food setting, cross-contamination refers to the transfer of contaminants from a surface, object or person to food. This can happen in many different ways. Common causes of cross-contamination include:
The following table summarizes the four main types of food contamination, how they occur and key prevention measures:
| Type of contamination | What it is | Common sources/examples | Key prevention measures |
| Biological | Contamination by disease-causing bacteria, viruses, or other pathogens | High-risk foods (meat, poultry, seafood, eggs, dairy), poor temperature control, inadequate hygiene | Keep food out of the Temperature Danger Zone, follow safe cooking and storage practices, maintain hygiene, clean and sanitise surfaces |
| Chemical | Chemicals entering food and making it unsafe to eat | Cleaning agents, pesticides on produce, non-food grade containers, pest control products, equipment oils | Store chemicals away from food, wash fruits and vegetables, use food-grade containers and oils |
| Physical | Physical objects entering food | Hair, glass, metal, pests, jewellery, dirt, fingernails | Wear appropriate protective gear, discard damaged equipment, control pests, maintain cleanliness |
| Cross-contamination | Transfer of contaminants from surfaces, objects, people, or foods | Shared utensils, raw and cooked food contact, dirty clothing, pests, waste | Use separate utensils, store raw food below ready-to-eat food, wash hands, clean and sanitise regularly |
As a food handler, it's important to remember that contamination can happen many ways, and sometimes in unexpected or overlooked places. The best way to prevent food contamination from happening in a food business is through food safety training and education. Food Handlers must be trained in fundamental food safety concepts and practical skills, such as:
AIFS provides online food safety training for all levels of responsibility in a food business or organisation, including the nationally recognised online Food Handler Course and Food Safety Supervisor Course.
Find the food safety course for your needs and start your training today! If you have any questions about which training is right for you or your team, contact us and we’ll be more than happy to assist.
Biological contamination is the most common type of food contamination. It happens when harmful bacteria, viruses or other pathogens get into food, often due to poor temperature control, inadequate cleaning, or poor personal hygiene.
High-risk foods include meat, poultry, seafood, eggs, dairy products, cooked rice, and prepared foods containing these ingredients. These foods need careful temperature control and handling because bacteria can grow quickly if conditions are right.
Food Handlers can prevent cross-contamination by washing hands regularly, using separate utensils and chopping boards for raw and ready-to-eat foods, storing raw food below cooked food, and keeping work areas clean and sanitised.
Not always. Many types of food contamination, especially biological and chemical contamination, cannot be detected by sight, smell or taste. That’s why following food safety procedures at all times is essential, even when food looks fine.
Food safety training requirements vary by state and territory, but many Food Handlers and Food Safety Supervisors are legally required to complete the relevant food safety training. Even where it isn’t mandatory, training is one of the most effective ways to prevent food contamination and protect customers.