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Unformatted text preview: FOODBORNE ILLNESS By the end of this lesson, you will be able to: • Describe how bacteria thrive under adverse circumstances • Explain how foodborne viral infections occur • Identify how parasites and fungi can contaminate food • Describe how crow-contamination occurs • List the common causes of food allergies • Identify the causes, likely food sources, symptoms, and control measures for several common foodborne illnesses In the last lesson we have seen how bacteria thrive under favorable conditions: being on the right foods, and in the right temperature range. In this lesson, we will explore mechanisms bacteria use to survive adverse circumstances. BACTERIA AT BELOW 41 ° F When PHF (TCS) are kept in a refrigerator below 41 ° F, bacteria are still multiplying, only more slowly. In frozen food, the bacteria become dormant. They are still there, but are not active, and not multiplying. Drying food can have the same effect: by removing available water, the bacteria become dormant. But in both freezing and drying, the bacteria are still alive. And later, when the food thaws, or when water is added, the bacteria spring back to life and begin to multiply at normal speed. BACTERIA AT ABOVE 135 ° F Cooking is a different situation. Most bacteria are destroyed in cooking. But some bacteria have a defense against this as well: they turn into “spores”, a change that protects them against these harsh conditions. Spores can change back and grow again when the food they are on has been time and temperature abused. Bacterial Spores • Spores withstand normal cooking • Spores form within bacteria • Spores become new bacteria Some bacteria can: • Infect • Poison • Both infect and poison FOODBORNE INFECTION • Harmful bacteria grow inside you and make you ill FOODBORNE INTOXICATION: • You eat foods contaminated by toxins and become ill FOODBORNE TOXIN-MEDIATED INFECTIONS • Result when you eat foods containing pathogens, which then produce illness-causing toxins in the intestines INCUBATION PERIOD: The period of time after eating contaminated food until the first symptoms of illness appear is called the incubation period. Incubation periods for different foodborne periods for different foodborne illnesses vary greatly. This fact can be useful in identifying the food source of a foodborne illness. Incubation periods tend to be longer for foodborne infections than for foodborne intoxications. In a foodborne infection, there is there is typically a lengthy incubation period, while the harmful bacteria grow to a number sufficient to overwhelm a body’s defenses. For example, the incubation period for Salmonellosis, a foodborne infection, is from 6 to 48 hours....
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- Spring '11
- Bacteria, Gastroenteritis, Foodborne illness, Escherichia coli O157:H7