Microbiological hazards include bacteria, viruses, yeasts, moulds and parasites.
Viruses differ to bacteria because they don’t need food or water to survive. They live on food and then get into our bodies and make us ill. Viruses are killed by cooking. In relation to food safety, the main two to be aware of are Norovirus and Hepatitis A.
Micro-organisms such as bacteria are found in many places, including:
- Raw foods such as raw meat, poultry, eggs, fish, shellfish, and fruit and vegetables
- Pests and pets
- Rubbish, especially if it’s not handled or disposed of correctly
- People. We carry a lot of bacteria in our intestines and these come out in our faeces. Bacteria can also come from our clothing. The bacteria Staphylococcus aureus is commonly found in or on humans. For example; it’s found on our skin and hair and in our nose, ears and throat.
- Dirt and dust
- Surfaces and equipment that haven’t been cleaned properly
- Soil (for example on unwashed fruit and vegetables)
- Untreated water
The 4 key things bacteria need to grow:
1. Time: in the best conditions bacteria will multiply every 10-20 minutes.
They grow (or reproduce) by dividing in two. The process is called binary fission.
2. Warmth: bacteria can grow anywhere between 5°C and 63°C. This is called the danger zone.
3. Moisture: it’s critical for bacteria to grow.
The water content of food is measured in water activity (aw). Pure water is 1.00aw, fresh meat is 0.98aw and dried pasta 0.80aw. Generally, below 0.80aw bacteria can’t survive.
4. Nutrients: bacteria need nutrients, in the form of food to grow. They grow best in protein-based products such as meats, seafood, dairy products but they will also grow very well in cooked rice and pasta dishes. They don’t generally grow in foods that are high in sugar or salt.
The key way to control bacteria is to keep high-risk foods out of the danger zone. That means either keep them cold below 8°C (ideally below 5°C) or keep them hot above 63°C. Essentially, strict time and temperature control.
