Food poisoning
The major food safety hazard in modern meat production is contamination of the product with bacteria that cause food poisoning. There are many organisms that can cause food poisoning, but the most common ones associated with meat are:
- Campylobacter
- Salmonella
- Shiga-toxin producing E. coli
- Clostridium perfringens
- Listeria monocytogenes
- Staphylococcus aureus
Most of these organisms are carried in the faeces or on the skin of the animals processed for meat production, or on the skin of factory workers, so good hygienic practices will help to prevent contamination of the product. These organisms, however, can also establish biofilms on the factory equipment, and thus the equipment becomes a source of contamination.
Good sanitation between shifts will help to reduce the opportunity for the bacteria to persist in the environment and be carried over from day to day. Spot contamination, however, will still occur, so efforts should be made during processing to minimise cross-contamination between individual product units, and post-processing interventions to reduce the microbial load on products may be considered.
Campylobacter
Campylobacter is carried in the gut of livestock, and is excreted in the faeces. It does not survive very well in the environment, as it is very susceptible to drying, but accumulations of dirt can protect the organism. Thorough cleansing should eliminate it from the environment, while careful dressing will reduce the likelihood of it being transferred to carcass meat.
Salmonella
There are over 2,500 different salmonellae, only some of which cause illness. Some serotypes are extremely host-specific and are found only in certain species of animal, while others cause disease in a wide range of animals, for example Salmonella Typhimurium. Salmonella has been found on 0.22% of beef carcasses and 5.74% of sheep carcasses in Australia.
Salmonellosis is carried in the gut of livestock, and is present in faecal material. Through cross-contamination, the skins of livestock can carry up to five Salmonella organisms per square centimetre and the organism can survive for prolonged periods on hides and in the environment.
E. coli
There are many different E. coli serotypes, not all of which are pathogenic. Those strains that produce shiga-toxin are the most pathogenic.
Ground beef or mince and associated products, have been associated with a number of serious outbreaks of E. coli O157 illness in people, which has resulted in thorough testing programmes for ground beef and trim and a drive to prevent the organism being transferred to meat at all stages of the chain.
Clostridium perfringens
The Clostridia produce spores, small, highly resistant 'packaged' bacteria, that can survive cooking. The cooking process itself triggers the spores to germinate, forming vegetative Clostridia cells, which multiply in the food while the temperature of the food is still above 12°C. When large numbers of cells are consumed with the food, the cells produce a toxin within the intestine that causes enteritis.
To prevent Clostridium perfringens food poisoning, cooked products should be cooled rapidly following heat treatment. Botulism, associated with poorly canned foods, is caused by a fatal toxin produced by another member of the same bacterial family, Clostridium botulinum.
Listeria monocytogenes
Listeria is a food-borne pathogen that can survive and multiply at refrigeration temperatures and persists for long periods in food processing environments. It does not compete particularly well with the spoilage organisms on fresh meat, but ready-to-eat products are often implicated in outbreaks of human listeriosis.
Thorough cooking will destroy Listeria and it is important that cooked products are not exposed to recontamination following heat treatment.
Staphylococcus aureus
Certain strains of Staphylococcus aureus produce a toxin which causes gastroenteritis. The toxin is produced during the growth phase of the organism, between 8 and 47°C. The organism is carried on skin and high numbers are often associated with the nose, ears and wounds.
Poor personal hygiene practices during food handling lead to contamination of the product with the organism, and poor temperature control leads to microbial growth and toxin production. The toxin is heat-stable, so cooking kills the organism, but leaves the toxin in the food.