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A.10.1 Identify two main categories of food-transmitted diseases: food-borne infections and food poisoning.
Food-borne infections are caused by parasitic organisms (for example, worms, protozoa, bacteria and viruses) that use food to gain access to the human host. The parasites do not grow in the food but in the human host. Only a small dose is required to cause illness. Some of these diseases can be transmitted via contaminated water, directly from animals or indirectly from infected objects, such as toilets. Worm infections include tapeworm and roundworm. Proper meat inspection in abattoirs and good standards of hygiene reduce the incidence of these diseases. Amoebic dysentery is caused by protozoan infection.
Food poisoning occurs because certain foods are naturally toxic (for example, rhubarb leaves) or because they have become contaminated with toxic chemicals or food poisoning bacteria. Certain fungi are toxic. Toxic chemical contamination can occur if food is harvested too soon after spraying with pesticides and other chemicals. Bacterial food poisoning is the most significant food-transmitted disease in developed countries and is a far greater hazard than food-borne infections. However, in developing country contexts food-borne infections are important.
A.10.2 Identify two main categories of bacterial food poisoning: infective bacterial food poisoning and toxin-type bacterial food poisoning.
In infective bacterial food poisoning, food becomes infected with certain bacteria, for example, Salmonella. These grow in food (due to improper storage) and when consumed they continue to grow in the gut of the person who ate the food. Their growth and death in the gut causes the symptoms of food poisoning.
Toxin-type food poisoning occurs when bacteria growing in food, for example, Staphylococcus aureus, produce toxins. If food containing the toxins is consumed, then food poisoning occurs.
A.10.3 Outline the signs and symptoms of food poisoning.
Symptoms of food poisoning depend on the type of contaminant and the amount eaten. The symptoms can develop rapidly, within 30 minutes, or slowly, worsening over days to weeks.Usually food poisoning is not serious, and the illness runs its course in 24-48 hours. www.emedicinehealth.com
A.10.4 Explain how lifestyle factors contribute to the increased incidence of food poisoning.
In developed countries, more people eat outside their own homes, with a resulting increase in food poisoning. Additionally, there is increased consumption of ready meals, which, if not stored or reheated correctly, can contribute to food poisoning.
A.10.5 Describe how food poisoning can be avoided.
Preventing the contamination of foods with food-poisoning bacteria and/or preventing the growth of bacteria in the food.
A.10.6 Define food hygiene.
A.10.7 Explain how good personal hygiene can help to prevent the contamination of food with food-poisoning bacteria.
A.10.8 Explain how the design of food preparation areas can help to prevent the contamination of food with food-poisoning bacteria.
A.10.9 Describe “high-risk” foods.
Foods (for example, milk, mayonnaise, meat, fish) that can support the growth of food-poisoning bacteria are termed “high-risk” foods. To prevent the growth of food-poisoning bacteria, high-risk foods should be kept hot or cold but never warm.
A.10.10 Describe the temperature danger zone for bacterial growth.
The temperature danger zone is between 10°C and 63°C. Food-poisoning bacteria will not usually grow below 10°C because there is insufficient warmth to support growth and the bacteria are inactive. Above 63°C, food-poisoning bacteria, but not their spores, are killed by the heat.
A.10.11 Explain that cooking is an important means of controlling bacterial growth.
Proper cooking depends on four considerations: sufficiently high cooking temperature; sufficient time for cooking; the size of the food being cooked (food is a poor conductor of heat, and therefore large items of food, for example, joints of meat, need longer cooking times than smaller ones); and the initial temperature of the food (some frozen foods, for example, frozen poultry, which can be contaminated with Salmonella, need to be defrosted before cooking, otherwise the centre temperature will never be high enough to kill any bacteria present).
A.10.12 Explain how an understanding of food poisoning influences the design of individual convenience foods.
Bulleted list and italicised paragraphs are excerpted from Design Technology: guide. Cardiff Wales, UK: International Baccalaureate Organization, 2007.
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