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Food safety

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Food safety is a scientific discipline describing the handling, preparation, and storage of food in ways that prevent Foodborne illness.

Domestic foodborne illness prevention

At home, prevention of Foodborne illness mainly consists of:

  • separating foods while preparing and storing to prevent cross contamination. (i.e. clean cutting boards, utensils, and hands after handling meat and before handling ready-to-eat foods, etc.)
  • washing and drying hands before handling ready-to-eat foods.
  • not preparing food when sick or recovering from recent illness
  • respecting food storage methods (hot foods hot and cold foods cold) and food preservation methods (especially refrigeration), and checking the expiration date;
  • avoiding over-long storage of left-overs;
  • washing the hands before preparing a meal, and before eating;
  • washing fresh fruits and vegetables with clean water, especially when not cooked (e.g. fruits, salads), scrubbing firm fruits and vegetables with a brush to clean;
  • washing dishes after use, rinsing them well in hot water and storing them clean and dry;
  • keeping work surfaces and chopping boards clean and dry;
  • keeping the kitchen and cooking utensils clean and dry;
  • not relying on disinfectants or disinfectant-impregnated cloths and surfaces as a substitute for good hygiene methodology (as above);
  • preventing pets walking on food-preparation surfaces.

Bacterial growth

Bacteria need warmth, moisture, food and time to grow. The presence, or absence, of oxygen, salt, sugar and acidity are also important factors for growth. In the right conditions, one bacterium can multiply using binary fission to become four million in eight hours. Since bacteria can be neither smelled nor seen, the best way to ensure that food is safe is to follow principles of good food hygiene. This includes not allowing raw or partially cooked food to touch dishes, utensils, hands or work surfaces previously used to handle even properly cooked or ready to eat food.

High salt, high sugar or high acid levels keep most bacteria from growing, which is why salted meats, jam, and pickled vegetables are traditional preserved foods.

Botulism may come from smoked or salted meat according to the National Digestive Diseases Information Clearinghouse webpage.

The most frequent causes of bacterial foodborne illnesses are cross-contamination and inadequate temperature control. Therefore control of these two matters is especially important.

Food temperature

Thoroughly cooking food until it is piping hot, i.e. above 70 °C (158 °F) will quickly kill most bacteria, parasites and viruses. Clostridium botulinum, Clostridium perfringens and Bacillus cereus, produce heat-resistant spores some of which survive temperatures up to 100 °C (212 °F). Norovirus and Hepatitis A can sometimes survive temperatures up to 88 °C (190 °F). Once cooked, hot foods should be kept at temperatures out of the danger zone. Temperatures above 63 °C (135 °F) stop microbial growth.

Cold foods should also be kept colder than the danger zone, below 5 °C (41 °F). However, Listeria monocytogenes and Yersinia enterocolitica can both grow at refrigerator temperatures. Control of the Cold chain is critical.

Hot foods should be held at 57 °C (135 °F) or hotter until ready to cool. Hot foods need to be cooled quickly to limit the amount of time the food is in the danger zone (temperature range at which bacteria can grow.) The food should be cooled from 57 °C (135 °F) to 10 °C (50 °F) within two hours, then further chilled to less than 5 °C (41 °F) in 4 hours. Foods take much longer to cool than most people realize. Food should then be held chilled at 5 °C (41 °F) or less.

UK HACCP guidelines and other official information

The UK Food Standards Agency[1] publishes recommendations as part of its Hazard Analysis and Critical Control Points (HACCP) programme. The relevant guidelines at http://www.food.gov.uk/multimedia/pdfs/csctcooking.pdf state that:

"Cooking food until the CORE TEMPERATURE is 75 °C or above will ensure that harmful bacteria are destroyed.
However, lower cooking temperatures are acceptable provided that the CORE TEMPERATURE is maintained for a specified period of time as follows :

  • 60°C for a minimum of 45 minutes
  • 65°C for a minimum of 10 minutes
  • 70°C for a minimum of 2 minutes"

Previous guidance from a leaflet produced by the UK Department Of Health “Handling Cooked Meats Safely A Ten Point Plan” also allowed for:

  • "75°C for a minimum of 30 seconds
  • 80°C for a minimum of 6 seconds"

as well as the above. Secondary references for the above may be found at:

Note that recommended cooking conditions are only appropriate if initial bacterial numbers in the uncooked food are small. Cooking does not replace poor hygiene.

In the United States, federal regulations governing food safety are fragmented and complicated, according to a February 2007 report from the Government Accountability Office.[2] There are 15 agencies sharing oversight responsibilities in the food safety system, although the two primary agencies are the U.S. Department of Agriculture (USDA), which is responsible for the safety of meat, poultry, and processed egg products, and the Food and Drug Administration (FDA), which is responsible for virtually all other foods.

Critique

Note that the above advice is open to critique

  • For example, some spore forming bacteria can survive cooking until the CORE TEMPERATURE is 75 °C or above - and may in fact be stimulated to grow. If food is cooked to a core temperature of 75 °C, it must be kept out of the "danger zone" (5 to 60 °C) thereafter to prevent spore formers from multiplying. Spore formers like Clostridium perfringens can cause serious gastroenteritis.
  • Another problem is that although a core temperature of 75 °C will kill most dangerous vegetative bacteria it does not inactivate some toxins (eg staphylococcal enterotoxin). So it is possible to become ill after eating well cooked food, as the food may already be contaminated with toxins before cooking.

For more information, see Foodborne illness.

Academic resources

Industrial resources

See also

References

  1. ^ http://www.food.gov.uk/
  2. ^ GAO-07-449T, Federal Oversight of Food Safety
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