MEAT CONTAMINATION.

When we buy meat, we expect it to be free from dangerous microorganisms and to keep well in refrigerators or deep freezers. Such confidence says a great deal for the efforts that have been made in the field of meat microbiology. But food chains are becoming more and more complex, from the production stage, through processing and distribution. This calls for new techniques to avoid meat being spoilt and to prevent food poisoning. There are two basic and complementary strategies of control. The first is to prevent, wherever possible, contamination and the consequent growth of microbes, the second, is to keep those detailed knowledge of the sources of contamination of the physiological and biochemical characteristics of bacteria that have to do with the way they grow. Our main aim as veterinarians has been to find out how meat becomes contaminated, what microbes grow on it, and at a fundamental level, what happens when they become established. Such work has improved our understanding of handling and storage conditions that are necessary for meat to be safe.
                                           CONTAMINATION AT SLAUGHTER .
Just how difficult it is to prevent contamination while carcasses are being skinned and eviscerated can be explained if we imagine sterile meat has been sandwiched between two heavily contaminated layers. The first is hide and the gut with their high bacteria population. Contamination with mud, feces or gut content is easily recognized but carcasses that seem clean may carry relatively large number of potential dangerous bacteria such as salmonella. How long meat may keep well in stores has a lot to do with how much it is already contaminated when the animal is slaughtered. That is also reflected in the shelf life of the many meat products on sale. Efforts have long been directed towards improving the cleanliness of abattoirs. Attention has been paid to cleaning, developing new techniques for cleaning carcasses and generally improving the structure at abattoirs walls, ceiling and other parts. Without a reliable objective technique for making microbiological comparisons, many measures were introduced without any idea how effective they were likely to be.
                                                 MONITORING BACTERIA.
There has been developed base plan to sample and monitor bacteria on carcasses. It has been used to compare abattoir performances in various communities. It has also been used in Norway in the study of bacteria on beef and pork carcasses where it enables microbiologists to identify one abattoir that showed consistently poor standards. The plan is also applied in British abattoirs to show the bacteriological effects of modernizing automated slaughter lines, and to improve abattoir which has been merely cosmetic, without significantly reducing bacterial contamination of meat. The new sampling scheme has made it possible to assess the effects and propose changes in abattoir design and operation as well as slaughter and dressing techniques so that before they are implemented, they can be tested experimentally. It will also allow various surface decontamination treatments to be evaluated, bearing in mind that the use of certain chemicals is prohibited in many countries.                                                                              SPOILAGE
When carcasses are chilled after slaughter and the chill temperature are kept at the proper level, putrefactive changes caused by the growth of anaerobes (microbes that live without oxygen) are inhibited so it is aerobic spoilage at the surface of meat that determines how long it will keep on the shelf. In some atmosphere, bacterial growth is hindered and moulds may be the main problem. Under commercial storage conditions, meat surfaces usually remain moist because the humidity gets high. There is little movement of air in chill rooms, which usually helps to reduce evaporation, but carcasses are hung too close to one another, stagnant air pocket may form close to the surface. The problems become worse if the carcasses are in touch, bacterial growth on surfaces in contact. This becomes the cause of dissatisfaction about chill room spoilage. It has been known for many years that growth of spoilage bacteria on fresh meat depends on ion concentration (PH) and the water content of the meat, as well as the temperature. That in contact with the surface is also involved, and that in turn, h as to do with the way the meat is packaged. Though, spoilage as hitherto been thought of in terms of the number and types of bacteria growing on the meat, it is now obvious that spoilage rate is affected by the availability of carbon sources and that bacteria at taxonomic study alone, do not explain what happen, there is a third factor, the metabolic activities of the bacteria as they grow on meat. The bacteria mainly responsible for slimming the surface belong to the genius pseudomonas. Not all the factors that are present during spoilage contribute to bad smell in fish; for example less than ten percent of the pseudomonas on fish can produce the characteristic odours. Our priority has been to distinguish between a various types of pseudomonas growing on red meat that has gone bad. The usual techniques for identifying bacteria take up a great deal of time. Dr. Gordon Shaw shown that pattern of carbon source used by more than hundred strains of pseudomonas on spoiled beef and pork has been divided into only four groups, using only eleven specific carbon source tests. So, our investigation into how meat becomes spoiled are focused on the relationship between the growth of certain kind of microorganism and the production of certain kind of spoilage compounds. Meat with a high PH of 6.0 or more from animals that have worked hard before slaughter or have been stressed in some other ways spoils much more rapidly in spite of the fact that the growth rate of pseudomonas is slightly affected over the growth range in pure culture. If meat with a high PH vacuum packed spoilage might be rapid and the odour produced might be offensive, this can be prevented by using pack laminates with very low oxygen permeability and by paying strict attention to controlling storage temperature.      
                                                           SUMMARY
Meat contamination is a battle the Veterinarians must win to ensure the health of the nation is intact. Government is thereby implored to join in the battle by passing out laws that will aid meat inspection and control. Also, researchers should be financed, extension programmes intensified and both ante mortem and post mortem examination should be made a priority. Veterinarians should therefore implore there vast knowledge to ensure that meat is not contaminated.