Contamination in Meat Production PDF

University of Baghdad College of Veterinary Medicine Dept. of Vet. Public Health/ Advance Food Contamination CONTAMINATION IN MEAT PRODUCTION The deep muscle tissues of healthy, slaughtered livestock contain few, if any, micr...

University of Baghdad College of Veterinary Medicine Dept. of Vet. Public Health/ Advance Food Contamination CONTAMINATION IN MEAT PRODUCTION The deep muscle tissues of healthy, slaughtered livestock contain few, if any, micro-organisms. However, their exterior surfaces (hide, hair, skin, feathers,) are naturally contaminated with a variety of microorganisms as are their gastro-intestinal tracts. From the moment of slaughter, each processing step subjects the carcass to opportunities for contamination with micro-organisms from the exterior surfaces, utensils and equipment and, most importantly, from the gastro-intestinal tract. Cutting of carcasses also involves the use of utensils and equipment and transfers micro-organisms to the cut surfaces. Theoretically removal of the skin should expose the sterile surface of the muscle but in practice the extra handling seems to contribute significantly to the bacterial load on the surfaces. This happens with meat production where the skin is removed early in the slaughtering process (e.g. beef, mutton, lamb, ostrich, and goat) or where the skin is removed later on (e.g. skinned chicken portions). There is ample opportunity to contaminate the exposed tissues of the carcass with micro-organisms from: exterior surface of the animal contents of the gastro-intestinal tract equipment and utensils workers garments and hands the abattoir itself (e.g. air, floor drains) water (and if used, ice) 1 Therefore, we need to control this opportunity for contamination by: _ Using properly cleaned equipment. _ Ensuring that the abattoir is properly cleaned/sanitised. _ Use hygienic methods of dressing that control contamination. _ Clean utensils at appropriate intervals during the process. _ Apply a high standard of personal hygiene. Meat with a good shelf-life has 102-104 organisms per cm2. To put the numbers of organisms associated with some sources of contamination into perspective: The exterior surfaces (hide, hair, skin, feathers) of healthy, live animals and birds are naturally contaminated with large numbers of a variety of micro-organisms. In a study of live cattle, 107 organisms were found per cm2 of hide. The soil (ground) is also a major source of micro-organisms and has comparable numbers (107) of bacteria per gram of soil. Faeces are about 100 x more contaminated and have an APC and “coli forms” of about 109 and 108 per gram of faeces, respectively. All of these can therefore serve as sources of microbial contaminants of the meat. The hide, fleece or skin of the animal is known to be a major source of carcass contamination (pathogens and spoilage bacteria). Special care should be taken to avoid contact with the meat. Removal of hides or fleece should be carried out in a manner that avoids contact between the outside of the skin and the carcass. When the surface of the hide touches the surface of meat during removal, can cause transfer of significant numbers of organisms to the meat surface. Likewise, hands and equipment that touch the outside of the hide can serve to transfer organisms to the meat and should not come into contact with the underlying carcass meat before thorough cleansing. 2 Since it is extremely difficult to obtain clean meat from dirty animals or birds, it is important that only relatively clean animals are presented for slaughtering. The cleanliness of livestock depends on husbandry, weather and climate (rainy, dry), methods of transport (stress causes defaecation and urination) and holding conditions at the abattoir. Cattle from feedlots may carry more faecal bacteria and less soil organisms than those from pastures. The modern trend is that excessively dirty animals should not be slaughtered until action has been taken to clean them. Also, strategies should be developed to reduce the number of such animals presented for slaughtering. From the figures quoted above, it is clear that under normal conditions, the heaviest and potentially the most dangerous load of bacteria is in the animal’s digestive tract. Already a small volume of material from the intestinal tract can contaminate the carcass with sufficiently high numbers of “coli forms’” to cause problems so that rupturing of the intestines or spillage of the intestinal content would cause severe contamination of the carcass. It is essential that great care be taken during evisceration to keep the viscera intact. In addition to the skin, the gastro-intestinal and respiratory tracts, urine and milk are other important animal sources of contamination. Meat handling and preparation involves contact with knives, hands and clothing of workers, processing equipment, (e.g. saws, hooks, boning tables, conveyers) and water used to wash carcasses, hands and equipment. Airborne spread of particles and aerosols will also occur in the abattoir. All of these factors can lead to the transmission of potentially hazardous organisms and contamination of carcasses. To minimise contamination, it is logical that attention should be paid to sanitation of all equipment (e.g. knife-sterilizers), well-chlorinated water, personal hygiene, hand-washing facilities near worker stations as well as the other methods of hygienic slaughtering. An important point to remember is that microbes firmly attach to meat and skin. This process is not yet well understood but it appears to become irreversible with time – the longer organisms remain on the meat the more difficult it becomes to remove them. In poultry 3 processing, the contact period between the meat surface and contaminating organisms is reduced by washing carcasses at intermediate points during processing before attachment occurs. The principle should not be applied to larger carcasses because too much wetting spreads rather than removes contamination. In fact, when small volumes of faeces, intestinal contents, mud or soil are spread over the carcass by rinsing, the clean areas of the carcass can become quite heavily contaminated. This is the reason why carcasses should not be rinsed. Wet carcasses also tend to spoil more rapidly - especially if wet and warm. Un-split carcasses should never be washed and split carcasses should only partially washed under lowest pressure possible. With any delay between consumption or further processing, it is essential to cool the carcass. As far as the microbiological quality of the carcass is concerned, fast chilling is indicated to restrict microbial growth. However, too rapid chilling can lead to cold-shortening of pre-rigor muscle and a loss of tenderness. With these conflicting requirements, optimal conditions for chilling must be a compromise. During chilling, contamination may occur by carcasses touching one another, by contact with dirty floors and walls, by splashing if cleaning is carried out in a loaded chiller and from the air, especially if the filters are not regularly cleaned. The main challenge to the meat industry in relation to hygiene is to minimise external contamination of meat with micro-organisms during all stages of the production chain. SPOILAGE BACTERIA A number of organisms are usually associated with meat spoilage. Some of the more important of these include Pseudomonas, Brochothrix, the Moraxella/Acinetobacter group, lactobacilli, psychrophilic Enterobacteriaceae and Psychrobacter. Depending on the growth requirements of the particular organism and the particular conditions of packaging and storage, different organisms are able to grow and spoil the meat. For instance, Pseudomonas spp need oxygen for growth and 4 are usually the main spoilage bacteria on conventionally packaged meat in oxygen permeable film at refrigeration temperatures. Lactic acid bacteria can again grow and spoil the meat when the oxygen tension in the package is low (in vacuum packaged meat). 11. FOODBORNE DISEASES A foodborne disease is an illness in humans in which the food is or contains the causative agent. Foodborne disease due to bacteria in the food usually manifests itself in episodes of gastro-intestinal disease (diarrhoea, vomiting etc). In recent times foodborne disease has been on the increase all over the world and even first world countries experience a worrying increase in outbreaks of foodborne disease. In fact, foodborne disease has been described by the World Health Organisation as one of the most widespread public health problems of the contemporary world. It creates an enormous social, cultural and economic burden on communities and their health systems. One of the important reasons why food safety management systems like the Hazard Analysis Critical Control Point System (HACCP) has been so widely introduced is to manage and control foodborne disease. 11.1 Agents of Foodborne Diseases _ Bacteria – Salmonella spp., Staphylococcus aureus, Clostridium perfringens, Campylobacter jejuni/coli, Clostridium botulinum, Bacillus cereus, certain strains of Escherichia coli and Listeria monocytogenes. Probably 20 or so could be listed. _ Chemical substances – ciguatera ,scrombroid , paralytic shellfish poisoning. _ Parasites - Giardia, Trichinella. _ Viruses - hepatitis A, Norwalk. 5 Food borne Disease Mechanisms _ Infection - The food acts as a vehicle to transport the infectious agent into the gastrointestinal tract where the micro-organisms colonise and produce illness. For example: Salmonella, Shigella. _ Intoxication - Microbial growth in the food causes the production of toxin(s) in the food prior to ingestion. For example: Staphylococcus aureus, Clostridium botulinum,. _ In Vivo Intoxication - The food acts as a vehicle for organisms that form toxin in vivo. For example: Clostridium perfringens and some Escherichia coli. Events Necessary for Food borne Illness to Occur The causative agent (chemical, physical or biological) must be present in the food. It can originate from the food itself, or from handling the food somewhere in the chain of production, from equipment or utensils and from the processing environment. Bacteria responsible for human illness can be associated with healthy or ill humans, animals or plants and with a normal or contaminated environment. For example, Staphylococcus aureus is common in the nasal passages of healthy humans. Pathogens such as Salmonella, Clostridium perfringens, Staphylococcus aureus, Yersinia enterocolitica, Campylobacter jejuni and Listeria monocytogenes are often present in small numbers as part of the micro- organisms on live, healthy animals. The causative agent must be present in sufficient numbers (e.g. bacteria) or high enough concentration (toxin) to survive normal handling of the food. Some bacteria will not cause foodborne illness unless large numbers are ingested or sufficient toxin is produced. For example, the number of staphylococci must be about 1 000 000 (106) per gram of food to produce a sufficient amount of toxin to make people ill. Even for organisms that have the capability to cause illness when ingested in low numbers (for example Salmonella), the chance of becoming ill is much greater when large numbers of organisms are present in the food than with smaller numbers of organisms. With some notable exceptions (Listeria monocytogenes, Yersinia enterocolitica, Clostridium botulinum 6 E), the common food pathogens do not grow at the typical commercial refrigeration temperatures. A sufficient quantity of food containing enough of the agent to exceed a person's resistance must be ingested. The resistance of individuals in a population varies greatly. People most susceptible are those with low resistance like infants, small children, the elderly, pregnant women and people who are ill. More recently it was shown that a severe bout of influenza or the common cold may significantly lower resistance to foodborne pathogens. 11.4 Sources Of Foodborne Disease Nearly 50% of all foodborne disease cases are associated with temperature abuse (inadequate cooling or heating) such as: _ Leaving foods at room temperature for several hours. _ Storage at too high a refrigeration temperature (keep below 5°C). _ Storage of foods in large containers in refrigerators so that it cools down only slowly (slow cooling gives time for pathogens to grow). _ When cooking meat (especially minced meat), not heating it to a core temperature of at least 70°C for 2 minutes. (Other time-temperature combinations are reaching a core temperature of 60°C for 45 minutes; 65°C for 10 minutes; 75°C for 30 seconds and 80°C for 6 seconds). _ Other causes of foodborne disease have to do with sanitary methods of preparation and storage: _ Wash hands before and after handling raw meat _ Clean raw meat preparation area before and after cooking _ Avoid contact with other foods  Clean raw meat reparation area befor and after cooking.  Avoid contact with other food. 7  Never allow raw food, used utensils or other surfaces likely to cause contamination to come in contact with cooked or ready-to- eat foods.  Never use the same unwashed plate that held raw meat to serve the cooked meat.  Do not handle food if you have diarrhoea/vomiting or uncovered infected sores or cuts.  Do not smoke while handling food and turn away from food and cover nose/mouth while coughing or sneezing. Assist Prof Dr.Huda N.Jasim 8