Vol. XII · Food Safety Plate 1 of 12food safety, hazards, biological, chemical, physical, allergens, norovirus, Salmonella, foodborne illness, CDCS

What Makes Food Unsafe.

In the United States alone, known pathogens in food cause an estimated nine million illnesses a year. Most could be prevented by four habits.

Food safety sorts hazards into four kinds. Biological: bacteria, viruses, parasites and the toxins some bacteria make — by far the largest cause of illness. Chemical: cleaning products, pesticide residues, natural toxins such as those in raw kidney beans or green potatoes, and contaminants formed in cooking (VIII.8). Physical: glass, metal, bone, stones. And allergens, harmless to most people and dangerous to some (XII.10).

The biological hazards behave unlike the others: they multiply. A few cells on a chopping board can be millions in a warm kitchen by evening (XII.2). So the core of kitchen safety is the World Health Organization's five keys: keep clean, separate raw and cooked, cook thoroughly, keep food at safe temperatures, and use safe water and raw materials. The workshop shows which pathogens account for most of the harm in one large study.

Below: the share of foodborne illnesses, hospitalisations and deaths caused by the leading known pathogens in the United States (published estimates), for the measure you choose.

What you will learn
Workshop
Scallan et al. (2011), estimates for 31 known pathogens in the United States: illnesses — norovirus 58 %, Salmonella 11 %, C. perfringens 10 %, Campylobacter 9 %, S. aureus 3 %; hospitalisations — Salmonella 35 %, norovirus 26 %, Campylobacter 15 %, Toxoplasma 8 %, E. coli O157 4 %; deaths — Salmonella 28 %, Toxoplasma 24 %, Listeria 19 %, norovirus 11 %, Campylobacter 6 %.

Few organisms, most of the harm

Norovirus alone causes about 58 % of the illnesses in these estimates, spread mostly by infected food handlers and contaminated surfaces, which is why handwashing heads every list. The serious harm is concentrated differently: Salmonella causes about 28 % of the deaths and Listeria about 19 %, though Listeria causes a tiny share of illnesses — it strikes pregnant women, newborns, the elderly and the immunocompromised, and it grows in the fridge (XIII.2).

Each key cuts a link. Clean hands and surfaces stop the transfer of norovirus and bacteria; separating raw from cooked stops raw-meat bacteria reaching food that will not be cooked again; thorough cooking kills what is on the food (XII.5); keeping food out of the danger zone stops the survivors multiplying (XII.3); and safe water and sound raw materials start the chain clean. Chemical, physical and allergen hazards are handled by care in storage, preparation and labelling.

At the stove

Walk through your kitchen with the five keys as a checklist: where do you wash hands, where do raw meats sit in the fridge, do you own a thermometer, how warm is the fridge, and where does your water come from?

The WHO Five Keys to Safer Food were published in 2001 and translated into more than 80 languages; they are deliberately simple enough to be taught in a single lesson.

Terms

Hazard
Anything in food that can cause harm.
Pathogen
A microorganism that causes disease.
Foodborne illness
Illness caused by eating contaminated food.
Five keys
The WHO's five rules: clean, separate, cook, chill, safe sources.
Food hazards are biological, chemical, physical and allergens; microbes cause most harm because they multiply. Follow the five keys.

Sources

  1. E. Scallan et al., "Foodborne illness acquired in the United States — major pathogens", Emerging Infectious Diseases 17(1), 7–15 (2011): an estimated 9.4 million illnesses a year from 31 known pathogens; shares of illnesses, hospitalisations and deaths by pathogen.
  2. World Health Organization, Five Keys to Safer Food Manual, 2006.