Bacteria are everywhere, and a few harmful ones on food are not always a problem — danger comes when they multiply to large numbers. Bacteria need six conditions to grow, remembered by the word FAT TOM. Remove any one of them and growth slows or stops.
The six growth conditions
FAT TOM stands for the six things bacteria need to thrive. As a food handler, almost everything you do is really about taking one or more of these away:
- Food — bacteria feed on nutrient-rich foods, especially protein-rich ones
- Acidity — most prefer low-acid, near-neutral foods (pickling and fermenting add acid to protect food)
- Time — given time, one bacterium can become millions; under ideal conditions numbers can double roughly every 20 minutes
- Temperature — they grow fastest in the danger zone of 5°C to 60°C
- Oxygen — some need oxygen, some grow without it (such as those in vacuum-packed or canned food)
- Moisture — moist foods support growth; salting, drying and sugar reduce available moisture
Potentially hazardous foods
Foods that are moist, low in acid and rich in protein are the ones bacteria love most. These are called potentially hazardous foods (sometimes 'high-risk' foods) and they must be kept under temperature control.
- Raw and cooked meat, poultry and small goods
- Seafood and shellfish
- Dairy products and egg dishes
- Cooked rice and cooked pasta
- Prepared salads, cut fruit and cut vegetables
- Soy products, gravies, sauces and soups
Practical examples
- Drying meat into jerky removes moisture, so bacteria cannot multiply.
- Keeping a curry above 60°C removes the right temperature, stopping growth.
- Lemon juice on a dish lowers acidity (pH), slowing some bacteria.
Key points to remember
- FAT TOM = Food, Acidity, Time, Temperature, Oxygen, Moisture.
- Removing even one condition slows bacterial growth.
- Bacteria can double in number about every 20 minutes in ideal conditions.
- Moist, low-acid, protein-rich foods are potentially hazardous and need temperature control.