Summary

Microbial contaminants are responsible for the majority of foodborne illnesses. Because bacteria, viruses, parasites, and fungi can be introduced at any point in the flow of food, they must be monitored and controlled throughout. Understanding how these microorganisms grow, reproduce, contaminate food, and infect humans is critical to understanding how to prevent the foodborne illnesses they cause.

Of all foodborne microorganisms, bacteria are of greatest concern to the manager. Bacteria are living, single-celled organisms that can be carried by a variety of means. Some cause food spoilage; others cause illness. Some bacteria cause illness by producing toxins as they multiply, die, and break down. Under favorable conditions, bacteria can reproduce very rapidly. Although vegetative bacteria may be resistant to low - even freezing - temperatures, they can be killed by high temperatures, such as those reached during cooking. Some types of bacteria, however, have the ability to form spores, which protect the bacteria from unfavorable conditions. Since spores are so difficult to destroy, it is important to thaw, cook, cool, and reheat food properly to keep bacteria from growing to harmful levels.

The acronym FAT TOM – which stands for Food, Acidity, Time, Temperature, Oxygen, and Moisture - might help you remember the conditions that promote the growth of foodborne microorganisms. Needing nutrients to grow, specifically proteins and carbohydrates, microorganisms grow best in food with a slightly acidic-to-neutral pH. Most foodborne microorganisms grow well between the temperatures of 4l°F and 14O°F (5°C and 60 °C). They also need sufficient time within these temperatures to grow. If contaminated food remains in the temperature danger zone for four hours or more, pathogenic microorganisms can grow to levels high enough to make someone ill. Most microorganisms that cause foodborne illness can grow either with or without the presence of oxygen, and require the moisture in food to grow. FAT TOM is the key to controlling the growth of microorganisms. Multiple barriers denying the microorganisms as many growth-supporting conditions as possible need to be put in place. These barriers include making food more acidic, raising or lowering its temperature, and lowering water activity.

Viruses are the smallest of the microbial contaminants. While a virus cannot reproduce in food, once ingested it will cause illness. Viruses can be transmitted from person to person, from people to food, and from people to food-contact surfaces. They can contaminate both food and water supplies. Some may survive freezing and cooking. Practicing good personal hygiene and minimizing bare-hand contact with ready-to-eat food is an important defense against foodborne illness from viruses.

Parasites are organisms that need to live in, or on, a host organism to survive. They can live inside many animals humans eat, such as cattle, poultry, pigs, and fish. They can be killed by proper cooking and freezing.

Molds and yeasts are examples of fungi, another concern of restaurant and foodservice establishments. Fungi are mostly responsible for the spoilage of many kinds of food, while some molds can produce harmful toxins. Molds are able to grow in a variety of environments, but they typically prefer to grow in and on sweet, acidic food with low water activity. Yeasts are known for their ability to spoil food rapidly. They are similar to molds in that they grow well in sweet, acidic food with low water activity.

Foodborne diseases are classified as infections, intoxications, or toxin-mediated infections. Each occurs in a different way. Foodborne infections result when a person eats food containing pathogens, which then grow in the intestines and cause illness. Typically, symptoms do not appear immediately. Foodborne intoxications result when a person eats food containing illness-causing toxins produced by pathogens found on the food or the result of a chemical contamination. The toxin might also come from a plant or animal that was eaten. Typically, symptoms of foodborne intoxication appear quickly, within a few hours. Foodborne toxin-mediated infections result when a person eats food that contains pathogens, which then produce illness-causing toxins in the intestines.

Our ever-changing world is opening new doors for microorganisms. Many new pathogens are emerging. New product formulations are creating niches for microorganisms that may not have been able previously to grow in the product. However, many new technologies are available and others are being developed to prevent the growth of pathogenic microorganisms.