Multiple Barriers for Controlling the Growth of Microorganisms

FAT TOM is the key to controlling the growth of microorganisms in food. By putting in place as many barriers as possible, you remove conditions that support bacterial growth. The list below provides some simple steps that, when combined, can create multiple barriers to control the growth of pathogens and ensure food safety. To kill or reduce the level of pathogens, food must be cooked to required minimum internal temperatures.

Make food more acidic. Add vinegar, lemon juice, lactic acid, or citric acid.

Raise or lower food temperature. Move food out of the temperature danger zone by cooking it to the proper temperature, by refrigerating it to 4l°F (5°C) or lower, or by freezing it.

Lower the water activity of food. Dry food by adding sugar, salt, alcohol, or acid. Food can also be air-dried or freeze-dried to remove water.

Limit the amount of time food is in the temperature danger zone. Prepare food in small batches, as close to service as possible.

Viruses

Viruses are the smallest of the microbial contaminants. They consist of genetic material wrapped with an outer layer of protein. While a virus cannot reproduce outside a living cell, once inside a human cell, it will reproduce more viruses. Viruses are responsible for several foodborne illnesses, such as hepatitis A and infections caused by Norwalk virus and rotavirus. Rotavirus infections are the leading cause of severe gastroenteritis among infants and young children worldwide.

Basic Characteristics of Viruses

Viruses share some basic characteristics.

Unlike bacteria, they rely on a living cell to reproduce.

They are not complete cells.

Unlike bacteria, they do not reproduce in food.

Some may survive freezing and cooking.

They can be transmitted from person to person, from people to food, and from people to food contact surfaces.

They usually contaminate food through a foodhandler's improper personal hygiene.

They can contaminate both food and water supplies.

Practicing good personal hygiene is an important way to prevent the contamination of food by foodborne viruses. It is especially important to minimize bare-hand contact with ready-to-eat food.

Parasites

Parasites are organisms that need to live in or on a host organism to survive. A host is a person, animal, or plant on which another organism lives and takes nourishment. Parasites can live inside many animals that humans use for food, such as cattle, poultry, pigs, and fish. Foodborne parasites include protozoa, roundworms, and flatworms. Parasites require many different hosts to carry out their life cycles; however, they are typically passed to humans through the meat of an animal host. To prevent foodborne illness caused by parasites, make sure food has been properly frozen, use proper cooking techniques, avoid cross-contamination, use sanitary water supplies, and follow proper handwashing procedures, especially after using the restroom.

Basic Characteristics of Foodborne Parasites

Parasites share some basic characteristics.

They are living organisms that need a host to survive.

They grow naturally in many animals—such as pigs, cats, and rodents— and can be transmitted to humans.

Most are very small, often microscopic, but larger than bacteria.

They may be killed by proper cooking or freezing.

They pose hazards to both food and water.

FUNGI

Fungi range in size from microscopic, single-celled organisms to very large, multicellular organisms. They are found naturally in air, soil, plants, animals, water, and some food. Molds, yeasts, and mushrooms are examples of fungi. The fungi of concern to restaurants and foodservice establishments are molds and yeasts.

Molds

Individual mold cells can usually be seen only with a microscope. However, fuzzy or slimy mold colonies, consisting of a large number of cells, are often visible to the naked eye. Bread mold is an example. The spores produced by molds are not the same as the spores produced by bacteria. Molds use spores for reproduction.

Molds are responsible for the spoilage of food. This spoilage results in discoloration and the formation of odors and off-flavors. Molds are able to grow on almost any food at almost any storage temperature. They can also grow in environments that are moist or dry, have a high or low pH, and are salty or sweet. They typically prefer to grow in and on sweet, acidic food with low water activity. Molds often spoil fruit, vegetables, meat, cheese, and bread because of their water activity and pH.

Some molds produce toxins that can cause allergic reactions, nervous system disorders, and kidney and liver damage. For example, aflatoxin, produced by the molds Aspergillus flavus and Aspergillus parasticus, can cause liver disease.

Food such as corn and corn products, peanuts and peanut products, cottonseed, milk, and tree nuts (such as Brazil nuts, pecans, pistachio nuts, and walnuts) have been associated with aflatoxins.

Basic Characteristics of Foodborne Molds

Molds share some basic characteristics.

They spoil food and sometimes cause illness.

They grow under almost any condition, but grow well in sweet, acidic foods with low water activity.

Freezing temperatures prevent or reduce the growth of molds, but do not destroy them.

Some molds produce toxins called aflatoxins.

Although the FDA recommends cutting away any moldy areas in cheese - at least one inch (2.5 centimeters) around them—to avoid illnesses caused by mold toxins, throw out all moldy food, unless the mold is a natural part of the food (e.g., cheeses such as Gorgonzola, Bleu, Brie, and Camembert).

Although mold cells and spores can be killed by heating them, toxins that may be present are not destroyed by normal cooking methods. Food with molds that are not a natural part of the product should always be discarded.