The invention relates to a method and a system for cleaning the surface of a pig carcass or part thereof, in particular after singeing or flaming.

In the slaughtering of pigs the whole carcasses are singed in a singeing furnace or alternatively flamed in order to tighten up the skin, sterilize the surface and remove remaining hair on the carcasses. After singeing or flaming there is a more or less dark layer of burnt hair and cuticle to be removed from the carcasses. This is nowadays effected by means of e.g. so-called scraping stations with rotating scraper bla¬ des, whereby the outermostRinged layer of the skin is scraped off. Rotating brushes are used as a supplement to the scraper blades on the areas of the carcass which are missed by the scraper blades.

In order that the scraping step may be carried through with a good result it is necessary firstly to moisten the carcasses and this is effected .by spraying them with cold water. A serious drawback of this prior art is that it is not possible to clean the scraping plants thorough¬ ly. The result is that the carcasses which, moreoever, have been superficially sterilized by the singeing are imparted a strong rise in their bacterial count. Under disadvantageous circumstances this may affect the good keeping quality of the meat.

The object of the invention is to provide a method of cleaning the surface of pig carcasses which is put through with no bacteriological pollution. With a view to obtain this the method according to the invention is characterized in that solid part¬ icles poor in germ, such as granular plastics, salt or preferably ice particles, accelerated by an accelera¬ tion unit hit the surface of the carcasses.

The system according to the invention is further characterized by comprising an acceleration unit for accelerating solid particles poor in germ and direct them towards the pig carcass. Danish patent No. 92 884 deals with a method by which meat is removed from the bones by abrasive blasting with ice particles. After being subjected to the method described in said reference the meat is torn into shreds which may be used in sausages, forcemeat, puddings and the like.

The novel and surprising features of the inven¬ tion consist in that blasting with ice particles or a similar _: proceεs by which solid particles are made to hit a surface may be >used for cleaning the surface of pig carcasses. It is known to make use of blasting pro¬ cesses for cleaning hard surfaces whereas the surface or the rind of a pig carcass immediately after singeing or flaming is quite soft.

Preferred embodiments will appear from the dependent patent claims.

The invention will now be explained- in detail by means of examples, partly with reference to the schematical drawings, in which

Fig. 1 illustrates the cleaning of- the surface of a carcass by means of an ejector wheel, viewed from the side, and

Fig. 2 a corresponding surface cleaning, viewed from above.

Figs 1 and 2 sho ^' w the cleaning of the surface of a carcass 7 by means of ice particles ejected from a rotary wheel 1 of a type known per se.

The ejector wheel l comprises a wheel 5 with radial blades 2, an inlet 3 and a guard 4. The wheel 5 is driven by an electric motor 6. The example makes use of scaled ice with a mean diameter preferably smaller than 5 mm. The scaled

ice has shown to have a tendency to be comminuted by the rotary wheel so that the mean diameter of the ice particles becomes smaller than 2 mm. On entering into the inlet 3 of the ejector wheel, the ice particles used have a temperature of less than -5° and preferably less than -8 ^β , thereby obtaining a better result. To further lower the temperature does not appear to improve the result. In order to obtain a reasonable effect of the surface cleaning the ice particles are preferably made to hit the surface of the carcass at a rate of more than 30 m/sec, e.g. between 30 and 50 m/sec, corresponding in the example to a circum¬ ferential velocity of the ejector wheel of more than 40 m/sec, e.g. between 40 and 60 m/sec. In the example the distance between the surface of the carcass and the ejector wheel 1 (the periphery of the wheel 5) is preferably kept under 30 cm, preferably between 20 and 25 cm.

It has turned out to be advantageous that the particles hit the surface of the carcass at an angle of incidence α (Fig. 2) larger than zero,- preferably between 45 and 85°, and most preferably between 60 and 80°. This increase of the angle of incidence in rela¬ tion to zero (perpendicular to the surface) results in that a larger area is being processed at the same time, thereby improving the economy of the process.

The surface cleaning will be most effective if the carcass is humid either by spraying with water prior to the blasting process or by dosing together with the ice particles a smaller quantity of water (for instance approximately 4 dl the carcass). Moreover, it has turned out to be advantageous that the blasting process is carried through as quickly as possible after singeing or flaming so that the cleaning process starts when the carcass is as hot as possible.

By the above described cleaning process the sur¬ face of a carcass is cleaned off the dark layer

deposited on it after singeing or flaming without damaging the surface of the carcass.

In another example, a carcass has been processed by blasting with ice crystals. The ice crystals had a temperature of -6.1 ^C C and use was made of blower equip¬ ments operating according to the injector principle. Pressurized air with a pressure of 6 bar was used for the blasting, but experiments down to 4 bar did not show any considerable change of the surface cleaning. The result of this cleaning process was a neat and uniform surface which was not torn. Moreover, the thawing of ice contributed to moistening the surface which is,-useful in the cleaning process.