Microorganisms specifically harmful ones or food borne pathogens (the ones that cause foodborne illnesses) require things in order to sustain their lives, just like us humans. Luckily for us, the Earth is abundant in everything for us to survive—like air, water and food. As for the microscopic world, there are 6 main factors that affect growth of harmful microorganisms or foodborne pathogens: food, acidity, time, temperature, oxygen and moisture.

Too many to remember? People in the food industry better know them as the FAT TOM, for fast memory retention.

Who is FAT TOM?

FAT TOM basically are the requirements for microbes to grow. With these factors or conditions at optimum levels, pathogens would be very happy to grow.

The bad thing is that it raises the chance of experiencing foodborne illness to us humans if contaminated food is consumed. And for most of the time, there’s no telling that because these microorganisms do not produce perceivable changes like in odor color. Unless we start exhibiting symptoms, which something we wouldn’t really like.

Regular training or seminar must be conducted in every organization so every personnel, especially food handlers, are aware of these. Most food safety classes would likely include FAT TOM at the start of the course.

By fully understanding FAT TOM, one would be able to maximize the food’s shelf life, know how to keep food from spoiling fast, promote proper food handling, and prevent foorborne illnesses.

Food

Pathogens very much like carbohydrates or protein-rich foods. It’s the main reason why food such as eggs, fish, meat and bread spoil faster than others. These perishables are what pathogens like salmonella and E. Coli love to live in. Storing them in low temperature environment like in a freezer slows their growth down.

Acidity (pH level)

The level of acidity of a substance (food) is measured by its pH level. The food industry works a lot on this pH level (with a scale of 1 to 14). Acidic substances have lower pH (less than 7) while basic substances have higher pH (more than 7). Neutral pH (neither acidic nor basic) has a pH of 7.

Pathogens grow well in low acidic environments, somewhere at 4.5 to 7.5. But too acidic environments (lower than 4.5) aren’t favorable to them. Food items like vinegar, tomatoes, pickled or soured products can make an environment too acidic for pathogens to survive.

Time

Food that can provide the necessities like nutrients and favorable pH level (low acid) will eventually spoil, even faster at optimum conditions. If you leave food at such condition for considerably long, the number of bacterial population in it could double in just 20 minutes. To better see the picture, a single bacterium could multiply in millions in just a few hours. Leaving food to stay in the Temperature Danger Zone for considerably long is even scarier.

The Temperature Danger Zone (TDZ) is a temperature range of 40°F (4°C ) to 140°F (60°C) where you don’t want your food to stay at for too long as bacteria growth is faster. Never put your food somewhere within this range for more than 2 hours. If you inevitably do, discard the food right away.

Temperature

Refrigeration of food slows down bacterial growth. However, removing the food out of refrigeration activates bacteria to multiply. The movement is even faster within the Temperature Danger Zone.

The general rule is to keep the food out of the Temperature Danger Zone. Keep hot food hot and keep cold food cold. Hot food should be at or above 140 (60°C). Hot food can be stored while maintaining its temperature in slow cookers, steamers or warming tray.

Cold food should stay at temperature of 40°F (4°C ) or below. Cold food can be placed in coolers or fridge to maintain their low temperature. Just make sure the fridge is working properly and is maintaining low temperature.

You might also like: Helpful Refrigerator Tips

When cooking food, it’s necessary to obtain a temperature high enough (at least 165°F) for a certain duration to kill pathogens.

Oxygen

Like humans do, bacteria need oxygen to live. Aerobic bacteria require an oxygenated environment to grow and thrive—most pathogens belong to this group. However, a few pathogens require no oxygen to live and are called anaerobic bacteria. One notorious anaerobic bacterium is Clostridium Botulinum, a pathogen that causes Botulism, a severe and potentially fatal food poisoning. Botulism usually occur from low acid canned products like fruits and veggies.

Another form of bacteria is facultative bacteria. They prefer to live with oxygen but not generally necessary in order to survive.

One common preservation method that deprive bacteria of oxygen is canning, something that we have been practicing since the Napoleonic Wars in the early 1800s.

The idea with canning is that the processed food is sealed in an airtight container. During processing, the heat removes air from the container and creates a vacuum seal later on. When done well, the food can be stored a minimum of one year.

Moisture

Aren’t we all used to reading instructions to keep food items in dry places? One reason for this is to prevent the growth of microorganisms as just like us, they also need water.

Pathogens are water or moisture- rich food loving microorganisms. Food scientists usually deal with calculating the amount of moisture content and water activity level in raw ingredients and finished products. As much as possible, they want to keep them low. For further discussion on water activity, visit this post: Water Activity (a_w) and Food Safety.

Over the years, people have developed ways to preserve food by depriving microorganisms of water. One of the most common and oldest ways of reducing moisture content is drying.

Another common way of reducing water is by osmotic dehydration using solutes such as sugar and salt. A process known as osmosis draws the moisture out of the food and to the surface where it evaporates. This method also directly eliminates the bacteria by dehydration by attacking their cell wall.

Since the earliest times, people have used sun drying, air drying and smoking to preserve food such as mushrooms, cereals, seafood like octopus and shrimps and fruits like grapes and oranges .

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