Meat Science and Nutrition
There are several diseases well known to both the industry and the general public that are directly related to all the domestic meat species of beef, pork, lamb, and poultry. These include:
- E. coli from ground beef
- BSE (bovine spongiform encephalitis) from beef cattle
- Trichinosis from pork
- Salmonella from poultry
- Scrapie from lamb and mutton
In addition, the meat and food industry are vulnerable to a variety of other infectious diseases that can manifest in food processing areas due mainly to poor personal hygiene and processing sanitation practices, which in turn can develop the growth of bacteria, viruses, moulds, and yeasts.These can then set the stage for:
- Foodborne infection, such as salmonella or trichinosis, caused by ingesting food that is contaminated with bacteria, parasites, and viruses
- Foodborne intoxication, either bacterial, such as E. coli, or chemical, where food has been contaminated with toxic chemicals, such as cleaning compounds or pesticides
Two particularly dangerous foodborne bacteria that can cause serious illness require special attention:
- Clostridium botulinum, which can develop in vacuum-packaged and canned foods
- Listeria monocytogenes, which occurs due to poor cleaning of machines, dirty floors, and drains
Following is a brief overview of the major risks – in terms of bacteria and illnesses – associated with meat and the meat industry. Some of the bacteria are known to originate from meat; others can and do develop in food processing areas through unhygienic practices.
BSE (bovine spongiform encephalopathy): commonly known as mad cow disease, a fatal brain-degenerative disease (encephalopathy) in cattle that causes a spongy degeneration in the brain and spinal cord. BSE has a long incubation period, about two-and-a-half to eight years, usually affecting adult cattle at a peak age onset of four to five years. All breeds are equally susceptible. The disease can be easily transmitted to humans who eat food contaminated by the brain, spinal cord, or digestive tract of infected carcasses. In humans, it is known as the variant Creutzfeldt-Jakob disease, and as of June 2014 it had killed 177 people in the United Kingdom and 52 elsewhere. Controls on high-risk offal (internal organs) were introduced in 1989. The cause was cattle, which are normally herbivores, being fed the remains of other cattle in the form of meat and bone meal (MBM), which caused the infectious agent to spread. Outbreaks of BSE in Canada severely crippled Canadian beef exports, which have only recently been restored. Under Canadian law, it is now illegal to feed cattle MBM. The Canadian Food Inspection Agency (CFIA) strictly controls the slaughter of all beef animals over the age of 30 months.
- Due to the severity of the disease, the following prevention measures have been implemented at the harvesting point, which has eliminated any possible transmission of the disease to the public. All possible infected parts of these animals are removed at the harvesting plant, kept separate from all other animal waste, and destroyed to safeguard the food supply. The parts removed include the skull, tonsils, a thick slice of the central backbone including the spinal column from the base of the skull to the pelvis, and two sections of the small intestines.
Clostridium botulinum: an anaerobic microorganism (it grows without air) which forms spores that exist over a wide range of temperatures. The organism itself does not cause illness, but the toxin it produces is one of the most deadly known to humankind. The spores can survive in frozen, raw, and precooked food. Although it is not a frequent cause of illness, it is considered the most serious to deal with in the food industry. This nasty organism is found in the intestines of humans and animals and in soil and streams. The major source of botulinum is swollen and damaged canned products and/or air-tight packages such as vacuum-sealed products with low acid foods such as beans, fish, and meats.
- Understand that the spores of the organism are very heat resistant and can survive boiling temperatures.
- During any food packaging process, ensure product is heated to a core temperature of 82°C (180°F) for 20 minutes to kill any toxins.
Clostridium perfringens: an anaerobic organism that produces heat-resistant spores. It also grows in the danger zone of 4°C to 60°C (40°F to 140°F) and may double in numbers in 10 minutes. This bacterium is found in intestinal tracts of humans and animals, in sewage, and in manure, and it is considered widespread. Insects and rodents can also become contaminated. Unwashed hands and dirty clothing are major sources and carriers of the disease. The main food sources affected by C. perfringens are foods high in proteins such as fresh meat of all types, deli items, and cooked meats like stews and gravies that have cooled too slowly.
- Only proper hot holding of cooked foods (above 60°C or 140°F) or rapid cooling in shallow trays to below 4°C (40°F) can prevent this disease from taking hold.
- Heat product above 74°C (165°F) to kill most non-heat-resistant strains.
coli: A bacterium found naturally in the intestines of humans or other animals. The strain common to the meat and food industry is E. coli 0157:H7. E. coli does not cause a disease and is not considered parasitic because its source of food is the body waste in the intestinal tract. However, should E. coli gain access to the kidneys, bladder, or other internal organs, it can become parasitic and produce infections that can turn fatal. E. coli outbreaks associated with domestic animals (mainly beef) have strained the meat industry when it has been discovered in ground meat supplies. In addition, E. coli has occurred in milk, cheese, and related foods as well as in plants and plant products irrigated with contaminated groundwater supplies.
- Understand that E. coli cannot be destroyed by freezing.
- Cook products such as ground meat to a core temperature of 71°C (160°F) to kill E. coli.
- Follow and enforce good personal hygiene (hand washing) after using the toilet.
- Follow industry safeguards to prevent contamination during the harvesting of animals, especially during the removal of the hide, which is often covered in fecal matter. (One large harvesting plant in Alberta has a state-of-the-art hide wash to help eliminate contamination prior to removal of the hide.)
- Take the preventive measure, which should now be a common practice, of carefully trimming meat surfaces on sub-primals that are near the aitch bone portion of the pelvis and anal canal. These areas are located on the hip and sirloin, especially on the hindquarters of beef carcasses and pork and lamb legs.
Listeria monocytogenes: Listeria is commonly found in soil, stream water, sewage, plants, foods made from milk, and processed foods such as hot dogs and deli meats. It can also be found in uncooked meat and vegetables and fruit such as apples and cantaloupes. Animals can also be carriers. Contamination may occur after cooking and before packaging. Listeria is responsible for listeriosis, a rare but potentially lethal foodborne infection. Listeria can grow in temperatures from 4°C to 37°C (40°F to 96°F), which is human body temperature. The bacterium is known to cause meningitis, a potentially fatal disease.
- Implement thorough cleaning practices especially for equipment used to slice or needle meats (tenderize). This includes fully disassembling equipment, then scrubbing, rinsing, sanitizing, and air drying.
- Keep all floors and drains thoroughly cleaned; these areas are often overlooked and are known to be breeding grounds for listeria.
- Institute a deep-cleaning plan for any processing area as part of a sanitation program. This involves committing to extensive cleaning of the whole work area several times throughout the working year, including cleaning floors, walls, and drains and the complete disassembly of all equipment.
Scrapie: a fatal disease that affects the central nervous system of sheep and goats. Scrapie is a transmissible spongiform encephalopathy (TSE). It is similar to BSE, but it is not caused by the animal’s feed. While the exact cause of scrapie is still unknown, the disease is associated with the presence of an abnormal form of a protein called a prion. According to Health Canada, there is no known link between scrapie and human health. However, the CFIA does have a control program in place. The disease seems to present itself differently in different countries. Wasting and debility (weakness) appear to be more prominent clinical features in North America, while pruritus (intense itching) remains the most noted clinical feature in Europe. Scrapie is spread from an infected female to her offspring at birth, or to other animals exposed to the birth environment, through fluid and tissue from the placenta.
- Scrapie is not known to be transmissible to humans, so any measures in place are to safeguard the health of sheep stocks.
Salmonella: Foodborne bacteria with 1,300 types known. One of the most severe infections caused by salmonella is typhoid fever. The main sources and carriers of salmonella in the food industry are most poultry, eggs and cracked eggs, shellfish, raw milk, and service workers with unwashed hands. People and animals may be carriers without showing any symptoms.
- Cook products to an internal temperature over 60°C (140°F) for 12 minutes to kill salmonella.
Staphylococcus: an aerobic organism (needs air to grow) that causes food poisoning by releasing toxins into food. It does not form spores. However, it may survive for months in the soil and in a frozen state in food. The most common carrier is the human body, particularly through skin abrasions, wounds, infected sinuses, pimples, etc. Raw poultry is also known to be a carrier. Food poisoning usually occurs when already cooked or easy-to-eat food is re-contaminated with staphylococcus. In the food service industry, susceptible products are those high in protein, such as custards, cream-filled bakery goods, sauces, meat and meat products (especially chopped meats), chicken salads, and cheeses. Staphylococcus can grow to enormous numbers on meat without producing changes in colour, odour, or taste if the infected product has not been stored in the safe temperature zones below 4°C (40°F) or above 60°C (140°F).
- Wash hands frequently, especially after using the toilet and when coughing and sneezing.
- Always keep foods stored in the safe temperature zones below 4°C (40°F) or above 60°C (140°F).
Trichinosis: a disease caused by Trichinella (parasitic nematodes, intestinal worms, and roundworms) that initially enter the body when meat containing the Trichinella cysts (roundworm larvae) is eaten. For humans, undercooked or raw pork and raw dry cured pork products, such as pork salami, have been most commonly responsible for transmitting the Trichinella parasites.
Trichinosis is a foodborne infection and is not contagious from one human to another unless infected human muscle is eaten. However, almost all carnivores (meat eaters) or omnivores (meat and plant eaters), such as bears, can both become infected and, if eaten, can transmit the disease to other carnivores and omnivores. For example, undercooked or raw bear meat can contain living Trichinella cysts. Therefore, if humans, dogs, pigs, rats, or mice eat the meat, they can become infected. In rare instances, larvae in cattle feed can infect cattle. There are six species that are known to infect humans. Today, trichinosis has been virtually eradicated in Canada due to well-managed controls in the Canadian hog industry.
Note: Commercially raised pork in Canada is at low risk of this disease, and it is common now for pork to be cooked to medium instead of well done. Doing so is safe provided the core temperature of 60°C (140°F) is held for at least one minute. Pork can also be cooked as low as a core temperature of 54.4°C (130°F) and held at that temperature for 30 minutes.
- Eliminate the risk of infection through proper cooking of meat.
- Cook all wild game meat, pork, and horse meat to an internal temperature of at least 71°C (160°F).
- Understand that curing (salting), drying, smoking, or microwaving the meat does not consistently kill infective larvae.