Zentralblatt fur Bakteriologie. 1. Abt. Originale B, Hygiene, Krankenhaushygiene, Betriebshygiene, praventive Medizin最新文献

In the present paper a mathematical model for the computation and costing of the sterilisation process in rendering plants has been developed and the computation of the F value in the canning industry has been used as a guide. In this, a test germ with the heat resistance parameters z = 10 degrees C and Dr = 10 sec is taken as a guide. If the steam-pressure heating regulation of the German Carcass Disposal Act which prescribes a temperature of 133 degrees C during 20 min after decomposition of the soft parts, is related to such a test germ, then a comparable sterilisation time of roughly 300 min at 121 degrees C is obtained, the heating-up phase and the cooling-down phase being disregarded. In computing the total lethality of a practical heating procedure in a dry melter, the result is a comparable heating process of abt. 640 min at 121 degrees C. While making allowance for the time lags in the temperature development in meat and bones during autoclaving and on the basis of a heating-up value of 100 minutes at 121 degrees C, various steam-pressure heat treating systems are suggested within the temperature range from 120 to 135 degrees C, having a comparable total lethal effect varying in duration.

Following a short historical outline of the former manner of disposing of cadavers and slaughter offals a detailed analysis is made of the Austrian spade-work in this field supported by an relevant documentation dating back to 1743, and of the importance for controlling animal epidemics and for meat hygiene.

The effect of the dry heat treatment in carcase disposal is dealt with in the light of the data on ther thermal resistance of spore-forming bacteria. The sources of recontamination in the carcass processing plants have been established on the basis of the microbiological examination of samples taken from the environment of these plants and from the end-product of seven plants. The results are compiled in tables. Standard values were established for the analyses of meat meal and bone meal. The main processes for the production of silage from animal raw material are described and illustrated with the help of a table containing typical results of analysis. Hygienic aspects of the silage production as well as the tenacity of micro-organisms and the possibilities of microbial and enzymatic activities are elucidated and supported by tables. Some basic principles for the culturing of the bacteria responsible for the gas-formation in the silage are briefly dealth with.

The raw-material basis of the rendering plants in Croatia is very solid. The lower average volume of material which is being processed anually in the 7 existing plants of the closed and semi-open type is estimated at 57000 tons roughly. This estimate is too low under the present circumstances and the more so in view of the future because of the constant expansion of the cattle-breeding and the meat industry. During the first phase, two rendering plants, one in the macro-area of Zagreb and another at Osijek, were erected and organised in keeping with the prevailing technological principles (dry system) and laid out for a capacity of 100 tons a day. The future erection of a third plant between the macro-area of Rijeka and Split is under study.

In Hungary more than half of the entire livestock is kept in industrial breeding plants i.e. under mass breeding conditions. So long as the industrial capacity of the plants remains insufficient to process the volume of carcasses, the animal breeding plants are compelled to find their own solutions for the disposal and/or rendering of the carcasses and waste. On some state farms the carcasses are processed into so-called meat-mash which must be utilised as fodder within 48 hours after the death of the animal. High-quality meat-meal can only be obtained from fresh carcasses. Carcasses are processed for reasons of economy, but the methods of carcass disposal are subject to stringent requirements imposed by the public health service, veterinary hygiene inspectorates and by the environment protection authorities. The carcasses or slaughter-house waste destined for processing must not contain any pathogens likely to be injurious to man or animal or to threaten the health of the persons concerned with the carcass processing. For this reason the carcasses must be kept in boilers for 2 to 4 hours at a pressure of 4 atü. The formulation of the factory rules and the technology of processing must make due allowance for these stipulations.

In Upper Austria, carcasses, offals and all kinds of animal material are collected in hygienically safe manner and taken to the Regau by-products plant. This plant was built in the light of the latest advances to keep environmental pollution at a minimum and is divided in a clean and unclean area. The raw material, including uncut carcasses, is dumped into troughs and then transported by a screw conveyor to the crusher. By steam pressure the material is pushed into a receptacle called "the gun" and from there it is conveyed to the extractor, which functions as sterilizer (30 min 134 degrees C), extractor and drier. The wet extraction procedure using perchloroethylene produces hygienically unobjectionable animal meal and fat. The method of deodorization, which was described in full detail, has made it possible to create not only optimum working conditions in the plant itself but also acceptable living conditions in the residential areas at a distance of some 400 m. Extensive automation of all processes results in optimum hygienic working conditions and also permits a reduction of the staff, in contrast to the conditions prevailing in the former knackeries.

The American rendering organization is different from that in Europe, it has historycally developed as an industry separate from slaughter houses, it has grown and waxed very profitable on a world wide basis, and finally it is now under technological attack which may eventually fundamentally change it and make it more like the organization of rendering that you have in much of Europe after all.

In Austria the legal basis of the activity of the veterinary officer in a carcass-processing plant, including his expertise in this field are outlined and illustrated, using the Regau carcass-processing plant as an example. In connection with the planning and expansion of this plant, the veterinary officer was responsible on questions of hygiene so that in the course of the expansion, it was possible to implement a chain of hygiene resulting from this preceding study. The strict separation between a clean and unclean area and the enclosed flow of the material received from the moment of arrival to putting the meal for animal feeding in sacks ensure humane working conditions for the staff and a hygienically impeccable quality of the products. It should be stressed that meat for animal feeding is not distributed and that the hides of dead animals are processed only in rare instances. The measures to be undertaken in the event of catastrophies with respect to carcasses are discussed and solutions are indicated. As the scope of tasks incumbent on the plant has been extended, it now also becomes responsible for conducting the fight against rabies. In 1977 alone 3300 test samples, including those of decapitated animals, were submitted to the federal institute. Furthermore, the carcass-processing plant is associated with a station for the observation and examination of domestic and wild animals suspected of rabies. This institution is practically indispensable. A dissecting room for the numerous dissections is also available to practising veterinary surgeons. However, the problem of waste water disposal has not yet been completely solved. All waste water coming from the unclean area is sterilised at a pressure of 4 atü but the question of whether the sewage should be discharged into the central purification plant has not yet been clarified. For reasons of hygiene and prevention of epidemics, the author advocates that a purification plant should be operated by the carcass-processing plant itself. The REgau plant represents an example of expedient and hygienically unobjectionable processing of waste into flour for animal feeding and fat and may also serve as a model for an economical system of environmental hygiene.

Just before the World War II rendering of all material of animal origin unfit for human and animal consumption was a fact and was later on regulated by Decree in 1942. The rendering act dates from 1957 referring to as "processing into useful product". There is a compulsery rendering which means that withdrawal of the material mentioned from rendering is in general prohibited. Material for rendering must be notified. In use is the dry rendering system (atmospheric batch cookers). At the moment there are four (three large and one small) rendering plants, the first being established in 1926, and they are under strict government supervision but not under government management. A licence is needed. Supervision is carried out by the Veterinary Public Health Inspectorate. After heating no micro-organism must be present and therefore regular checks for Clostridium perfringens as an indicator organism are carried out besides a contol of ther thermocharts. Recontamination should be avoided. As a result of the extensive bacteriological control since 1972 (Salmonella and other enterobacteriaceae, the latter as indicator organisms) there has been noticed a still growing improvement of the hygienic condition in the rendering plants. During the past half year Salmonella could not be isolated from samples endproduct. Transportation of raw material for rendering after notification to the head of the municipal meat inspection service is done by the rendering plant in completely watertight vehicles. There is a Rendering Board which must be consulted when legislative measures related to rendering are taken.