FAT TOM for Food Safety
Pathogenic — or disease-causing — bacteria are responsible for most cases and outbreaks of foodborne illnesses.
There are six primary conditions that allows these bacteria to survive and multiply, which you can remember with the acronym FAT TOM.
This article breaks down everything you need to know about FAT TOM for food safety.
FAT TOM 101
FAT TOM stands for Food, Acidity, Temperature, Time, Oxygen, and Moisture.
It’s a mnemonic device used to describe the six factors that bacteria — a biological hazard — love.
Here’s a breakdown of each factor:
Food
Like humans, bacteria require nutrients, namely protein, to support the growth and maintenance of life.
For this reason, protein-rich foods, such as meat, milk, eggs, fish, are most susceptible to bacteria growth.
Bacteria also love heat-treated plant-based foods, such as cooked onions, rice, baked potatoes, and soy protein products like tofu.
These foods are prone to time-temperature abuse and require time-temperature controls for safety (TCS).
TCS foods are formally known as potentially hazardous foods (PHFs).
Download this TCS Foods poster for FREE (includes English & Spanish versions!)
Acidity
The pH value is a measure of how acidic or alkaline something is.
The pH scale runs from 0 to 14, with 0 representing the most acidic, 14 representing the most alkaline, and 7 representing neutral.
Bacteria grow best in slightly acidic to neutral conditions (4.6–7.0 pH).
Foods that are slightly acidic to neutral generally require refrigeration and have relatively short shelf lives because they are prone to spoilage.
Examples of these foods include most fruits, vegetables, beans, dairy products, meats, and poultry.
Most bacteria will not grow in acidic conditions (< 4.6 pH).
Some foods are naturally acidic like tomato juice and citrus fruits, while other foods are formulated to be acidic, like dill pickles, pickled fish, and hot sauce.
Temperature
Different types of bacteria can grow well in cold and hot environments, but most prefer temperatures between 41ºF and 135ºF (5ºC and 21ºC).
This temperature range is known as the temperature danger zone.
Bacteria grow especially well between 70ºF and 135ºF (21ºC and 57ºC).
This is why you must cool foods from 135ºF to 70ºF (57ºC to 21ºC) twice as fast than you need to cool foods from 70ºF to 41ºF (21ºC to 5ºC) when following the two-stage cooling method.
Time
TCS foods can only remain in the temperature danger zone for a certain time before you have to toss, reheat, or move to a cooler.
This is because the more time you allow a food to be in the temperature danger zone, the faster bacteria grow and multiple and make food unsafe.
For this reason, food cannot spend more than four hours in the temperature danger zone.
Oxygen
Most bacteria are aerobic, meaning they require oxygen to survive.
Removing or reducing oxygen in food packages — such as by canning or vacuum packaging — stops the growth of bacteria.
However, Clostridium botulinum (botulism) grows well without oxygen, such as in damaged or improperly canned products.
Moisture
Bacteria don't grow well in conditions of low water.
This is why products low in water like bakery products, breakfast cereals, dried fruit, honey, chips, and other snacks have a long shelf life.
A measurement called water activity (aw) provides information about the amount of free water available for microbial growth.
Water activity is measured in values from 0.0 to 1.0.
Water has a water activity of 1.0.
Bacteria require a high amount of free water, and grow best in foods with a water activity (aw) 0.85 or above.
Water activity can be decreased by removing the water or reducing the free water that is available by adding salt or sugar, which bind to water.
Summary
FAT TOM stands for Food, Acidity, Temperature, Time, Oxygen, and Moisture. These factors allow bacteria to thrive.
FAT TOM overview
Here's a quick overview of FAT TOM
F Food | Protein-rich foods such as milk, meats, poultry, and seafood provide bacteria with the nutrients they need to grow and multiply. |
A Acidity | The pH value is a measure of how acidic or alkaline something is. The pH scale runs from 0 to 14, with 0 representing the most acidic, 14 representing the most alkaline, and 7 representing neutral. Foodborne pathogens grow best in slightly acidic to neutral conditions (4.6–7.0 pH). Most bacteria will not grow in acidic conditions (< 4.6 pH). |
T Temperature | Foodborne pathogens multiply quickly in the temperature danger zone. |
T Time | Foods should not remain in the temperature danger zone (41°F to 135°F) for more than four hours total. |
O Oxygen | Most bacteria require oxygen to grow. Removing or reducing oxygen in food packages — such as by canning or vacuum packaging — stops the growth of foodborne pathogens. However, Clostridium botulinum (botulism) grows well without oxygen. |
M Moisture | Water is essential for the growth of foodborne pathogens. A measurement called water activity (aw) provides information about the amount of water available to foodborne pathogens to use for growth. Foodborne pathogens grow best in foods with a water activity (aw) 0.85 or above. |
The bottom line
FAT TOM is a mnemonic device used to describe six factors required for bacterial growth.
FAT TOM stands for Food, Acidity, Temperature, Time, Oxygen, and Moisture.
While you can't control all of these factors, keep them in mind when storing and handling food to reduce the risk of foodborne illnesses.