The muscles of living healthy animals such as cattle and pigs are normally sterile, but during the slaughtering process bacteria from the animals'gastro-intestinal system and skin may be transferred to the surface of the carcass. The presence of pathogens here may present a risk for the consumer's health.

Equipments have previously been designed for reducing the number of pathogenic bacteria on the surface of carcasses. Certain designs use hot water to decontaminate the surface. The use of hot water confers certain benefits, as it is well suited for destroying bacteria and does not in itself contaminate the meat. However, water can be applied in various ways, which may give rise to problems. For example, the use of spray nozzles will cause the water to cool down before it hits the carcass. In addition the water will form a mist in the room and the use of spray nozzles requires high pump pressure.

WO 8901738 (Commonwealth Scientific and Industrial Research Organisation) describes a system for decontamination of cattle carcass halves conveyed individually on a slaughter line. The system has a number of guide plates along the walls of the cabin for distribution of the supplied hot water into a film. The film is directed as a water jet against the sides of the carcass halves at various levels. When using such water jets the above-mentioned problems relating to use of water sprays are avoided.

A similar system is marketed by the company APV under the name"Steer-Cleer". Guide plates distribute water with a temperature of 80 °C into a film, which in the form of soft, waterfall-like jets is directed against the surface of individually conveyed cattle carcass halves, decontaminating them as a result of the short-term heating effect of the water on the surface. The system is unsuitable for the decontamination of pig carcass halves

because these are conveyed in pairs on a gambrel so that the waterfall-like jets do not sufficiently reach into the inner side of the carcass halves.

The object of the invention is to provide a system capable of decontamination of pig carcass halves conveyed in pairs suspended on a gambrel. The decontamination achieved thereby shall be effective over all surface parts of the carcass halves, but shall not cause over-treatment of particularly exposed areas, leading to deterioration of quality, and to a large extent the water shall be applied without the use of spray nozzles to avoid the disadvantages associated with this.

This is achieved in a system according to the invention, which system is characterized in that one or more water jet devices at the lengthways walls of the cabin are arranged to produce waterfall-like water jets which seen from above are directed mainly perpendicularly in towards the mid-plane of the cabin between the lengthways walls, and that one or more other water jet devices at the lengthways walls of the cabin are arranged to produce waterfall-like water jets which seen from above are directed mainly obliquely in towards the mid-plane.

Preferably, one or more water jet devices arranged to produce waterfall-like water jets directed obliquely in towards the mid-plane, produce jets which seen from above form an angle of between 45 and 75° with the mid-plane.

Preferably, one or more water jet devices comprise a jet pipe directed obliquely in towards a guide plate arranged to widen the water jet from the jet pipe into a water film which leaves the device as a waterfall-like water jet.

In this embodiment the jet pipe may be directed downwards, and the guide plate may be mainly vertical and in its lower part be bent in a curved shape away from the cabin wall so that the water film leaves the plate as a waterfall-like water jet directed in towards the mid-plane of the cabin. The system may in this instance comprise water jet devices where the non-curved part of the guide plate is mounted on the wall or in parallel with it, and

other water jet devices where the non-curved part of the guide plate seen from above is mounted at an angle in relation to the wall.

According to another embodiment of water jet devices with jet pipe, the jet pipe may be constricted at the mouth to a slit-like opening running mainly parallel with the guide plate, and the guide plate may be mainly plane and oriented so that the water film is leaving the plate as a waterfall-like jet which seen from above is directed obliquely in towards the mid-plane of the cabin.

One or more water jet devices may have side members along the edges of the guide plate running in the direction of the jet to restrict sideways widening of the film.

The system according to the invention may comprise means for holding the carcass halves oriented with their split plane mainly parallel to the mid-plane of the cabin.

The system according to the invention preferably has catching arrangements in the lower part of the cabin for receiving the water after it has left the water jet devices, of which a first catching arrangement is constituted by the floor of the cabin and has a drain to a recirculation container, and a second catching arrangement consists of a longitudinal channel raised above the floor of the cabin and has a separate drain, which is mainly connected to sewer. In a system of this kind, the recycled water is contaminated less, so that for instance the additions of fresh water may be reduced.

This can be exploited in a system for treatment of carcass halves with hot water on a slaughter line conveying pairs of carcass halves, which system comprises a cabin with water jet devices, in that the system according to the invention comprises catching arrangements in the lower part of the cabin for receiving water after it has left the water jet devices, of which a first catching arrangement is constituted by the floor of the cabin and has a drain to a recirculation container, and a second catching arrangement consists of a longitudinal channel raised above the floor of the cabin and has a separate drain, which is mainly connected to sewer.

The invention is described in greater detail in the following with reference to the drawings, wherein Fig. 1 shows a longitudinal section of a system according to the invention for treatment of carcass halves with hot water on a slaughter line conveying pairs of carcass halves, Fig. 2 shows a cross section of the same system along line A-A in fig. 1, and Fig. 3 shows details of two water jet devices in the system.

The system in figs. 1 and 2 comprises a cabin with two lengthways walls 1. Sliding rail 2 of a slaughter line passes through the cabin in the mid-plane m between the two walls 1.

On the walls are mounted water jet devices 10,11,12, which produce water-fall like water jets 13 (fig. 2) hitting the surface of pairs of carcass halves 3. The carcass halves are suspended on a gambrel 4 and they are conveyed through the cabin by means of a conveyor acting on the top hook of the gambrel on sliding rail 2. The water jet devices are placed at different heights so that the water jets hit different parts of the carcass surfaces.

The devices are placed in the same way on the two walls 1 and exist in three different designs.

Devices 10 are of the type, which in the upper part consists of a plane plate mounted in direct contact with wall 1, and where the lower part of the plate is bent away from wall 1 in an approximate quarter circular curve. Above each plate is a hot water jet pipe 10a. The end of the pipe is bent in towards the upper part of the plate, so that the water jet hits the upper part of the plate and is widened into a water film flowing down the plate. The film is deflected by the lower curved part of the plate so that it leaves the plate as a wide waterfall-like jet having sufficient speed to hit the surface of the carcass at an angle of typically between 30 and 60°. Devices 10 are set to hit the nearest carcass half directly on the outside.

Devices 11 are designed similarly to devices 10 and thus in the upper part consist of a flat plate 14 (fig. 3) and in the lower part of a continuation of the plate, which is bent away from wall 1 in an approximate quarter circular curve. Above each plate is a hot water jet

pipe 1 la. The end of the pipe is bent in towards the upper part of the plate so that the water jet hits the upper part of the plate and is widened into a water film flowing down the plate, and similarly to devices 10, is deflected by the lower curved part and leaves the plate as a waterfall-like water jet. The plane plate and the associated lower curved part are mounted on the wall 1 at an angle of about 25° seen from above by means of fitting 15, and are adjusted so that the water jet from the lower curved part hits the remote carcass half on the inside. Unlike devices 10, devices 11 have some side members 17 on the plane plate and the lower curved part, which restrict the sideways widening of the water film.

Devices 12 are made by pressing together the mouth of a jet pipe 12a into a kind of slit, giving the jet greater departure speed. A fan-shaped guide plate 17 is welded to the pipe at the mouth and is positioned obliquely to the path of the jet so that the jet is widened into a wider, waterfall-like jet directed upwards towards the tail part of the carcass at an oblique angle seen from above hitting the carcass from the back side. Side members 18 restrict the sideways widening of the water jet.

In the lower part of the cabin is a channel 5 (figs. 1 and 2) to catch the used water which flows off the lower part of the carcass halves. This water has a relatively high contamination level (meat dust from the splitting process and other loose or water-soluble material) and is led directly into sewer. The floor 6 of the cabin collects used or unused water not captured in channel 5 and leads it to a cleaning system for coarse filtration and surface skimming of the return water. After cleaning, the water passes through a heat exchanger, which reheats the water to 80 °C, and then passes it to the water jet devices (10,11,12) again for repeated use. A monitoring system measuring the turbidity of the recirculated water ensures that the water is of adequate quality. Use of channel 5 means less contamination of water, so that the system can run for a whole day with less topping up of fresh water (tap water). The ratio between recirculated water and water disposed of in the sewer is approx. 4: 1.

The carcasses 3 are conveyed into and through the cabin with their backs first in the direction of conveyance indicated by arrow P. To maintain this orientation and to keep the

carcass halves separated from each other on gambrel 4, two parallel rods 7 are positioned a little above gambrel level to prevent the carcass halves twisting while in the cabin.

The system is able to treat 400 carcasses per hour, corresponding to the normal capacity on Danish slaughter lines. After decontamination, the carcasses are sent for tunnel cooling and temperature equalisation. It has been investigated with swab samples whether the decontamination is effective in terms of uniformity and reduction of total bacteria number.

This was the case to a surprisingly degree. Following tunnel cooling a reduction in the number of E. coli bacteria of 2.7 log units was demonstrated, a fully satisfactory outcome.

Moreover, none of the meat surfaces showed a lasting deterioration of quality properties.

The meat became slightly greyish immediately after decontamination, but regained the colour over the next 24 hours. The system has therefore proved to be particularly valuable for the decontamination of pig carcass halves conveyed in pairs on a slaughter line.