Device and method for scalding poultry

The invention relates to a device for scalding poultry, comprising: a processing space provided with transport means for carrying the poultry for processing through the processing space, a conditioning space connecting to the processing space for composing a conditioning medium, and displacing means for displacing the conditioning medium from the conditioning space to the processing space. The invention also relates to a method for scalding poultry.

The present invention relates to a device for scalding poultry. The present invention also relates to a method for scalding poultry.

The scalding of poultry, and more particularly slaughtered and bled poultry such as chickens, ducks and turkeys, has the purpose of reducing the attachment of the feathers to the carcass, such that removal of the plumage during a subsequent (plucking) process becomes simpler. A prerequisite for scalding is that scalding must be completed shortly after poultry has been slaughtered because of the rapid onset of rigor mortis. Partially because of the desired speed use has heretofore usually been made of a basin with warm water in which the poultry is immersed. After a treatment time of about 3 minutes the poultry is taken out of the basin and the feathers can be removed relatively easily. A drawback of this so-called “immersion scalding” is that the poultry entrains a considerable amount of water from the basin, and there is also the problem of possible transfer of dirt, germs and bacteria from the basin.

An alternative method of scalding is described in U.S. Pat. No. 3,703,021. Here the poultry is pre-plucked, i.e. a substantial part of the feathers is already removed such that the poultry to be scalded is already almost bald, and that the pre-plucked poultry is then carried through a processing space in a time period of 30 to 40 seconds. Steam-heated liquid is blown into this processing space with air as carrier medium. A uniform temperature, a 100% air humidity and an excess of liquid can thus be maintained in the processing space. The process conditions are monitored and maintained by detection means and control means co-acting therewith. It has been found difficult in practice to obtain a constant and effective scalding result with this method. A main quality criterion is of course the extent to which the feathers are loosened. Other factors determining the quality of scalding are the degree of damage to the epidermis (surface epithelium/dermis) and the degree of denaturation (“boiling down”) of proteins in the meat directly under the skin. At least all these aspects must be taken into account in quality control of the scalding process.

It is the object of the invention to provide an improved method of scalding as well as the means required for this purpose, whereby an effective scalding result can be obtained quickly and without the risk of cross-contamination while retaining the advantages of the prior art.

The present invention provides for this purpose a device for scalding poultry comprising a full plumage, comprising: a conditioning space for composing a scalding medium with a dew point lying in the range of [49-61]° C., a processing space provided with transport means which define a transport path for the poultry leading through the processing space, and dispensing means for the scalding medium connecting the conditioning space to the processing space and provided with at least one outlet opening which is directed toward the transport path and with which the composed scalding medium is carried from the conditioning space into the transport path, as a result of which liquid from the scalding medium condenses onto the poultry, and more particularly onto the skin of the poultry. A targeted condensation of the scalding medium will thus occur at the position where the jet of scalding medium strikes the skin of the poultry. The important advantage of condensation is that it allows a very considerable heat transfer in a relatively short time without the risk of (local or other) overheating (“overscalding”) of the poultry. Excess damage to the epidermis (surface epithelium) of the slaughtered animals can thus be prevented. After all, not only is a great heat transfer realized as a result of the condensation, but the temperature of the poultry will also not exceed the wet bulb temperature, at least as long as the skin has not dried up as a result of evaporation or as long as the liquid on the skin is not heated any further. Both ways of exceeding the wet bulb temperature require a considerable energy transfer which, because of the limited capacity of air heating (since the more rapid heat transfer resulting from condensation is no longer possible), will be less likely to occur. The scalding process according to the present invention thus has a built-in safeguard against excessive heating of the poultry. Dispensing means are very generally understood to mean supply means intended for directed supply of the scalding medium; the dispensing means may optionally be provided with control means if desired. Another significant advantage of the present invention is therefore that the condensation can be performed in targeted manner; the scalding medium will thus be blown at least partially underneath the feathers. To this end the jet (or jets) of scalding medium will in particular have to be brought into contact with the poultry in a manner aimed against the direction of implant of the feathers; the scalding medium will thus penetrate the feathers and at least partially reach the skin. It thus becomes possible to scald poultry without immersion in liquid and without first removing a part of the feathers. Carrying the scalding medium into the transport path (i.e. the path followed by the poultry) in directed manner, which of course implies that the scalding medium is also fed directly targeted at the poultry, results in an unexpectedly great advantage. Targeted condensation resulting from one or more jets of scalding medium makes it possible to obtain a controlled and desired scalding result without pretreatment (pre-plucking) of the poultry, in extremely efficient manner (quickly) and with a process-inherent safeguard against excessive heating of the poultry. This means that sufficient loosening of the feathers can be coupled to acceptable damage to the epidermis which can be classified as “low scald”, “intermediate scald” or “high scald” and a minimal degree of denaturation of the poultry meat.

Another significant advantage is that a very favourable scalding result can thus be obtained; scalding can be performed with the device according to the present invention in “intelligent” manner by targeting determined positions on the skin of the poultry less than other positions, for instance with the intention that the feathers at least substantially come loose everywhere with the same resistance. This is not otherwise essential. If a subsequent process (such as more particularly plucking) requires a specific variation in the attachment of the feathers over the carcass of a poultry animal, this can then be achieved with the device according to the invention. It is possible here to envisage for instance scalding a poultry animal such that, at locations which are less readily accessible for plucking, the feathers are less firmly attached than at locations where plucking is simpler. Partly due to the absence of a basin filled with liquid, the device can moreover be embodied such that it can be cleaned effectively and efficiently.

In respect of the scalding medium that can be applied, heated air is in the first instance envisaged which has a dew point in the range of [49-61]° C. and which is at least partially or almost fully saturated with water. Other carrier gases or gas mixtures can however also be applied. It is also the case for the liquid that alternative liquids or liquid mixtures can be applied instead of water. The device according to the present invention is not limited in respect of the composition of the scalding medium to be applied therein.

The dispensing means for carrying the scalding medium into the transport path are preferably provided with at least one adjustable outlet opening. Using such an adjustable outlet opening it is possible to select the optimal direction and form of the jet of scalding medium. The form, starting position, length and direction of the jet of scalding medium can be modified subject to situational conditions. The device can thus be adapted to treat different types of poultry, for different batches of the same poultry animal, or even per individual slaughtered animal for scalding. For adjustment of the outlet opening(s) at individual level, and optionally also in the case of adjustment for different group of slaughtered animals, it can be advantageous to automate displacement of the outlet opening, for instance by incorporating at least one sensor (envisage a camera system in particular) and a drive coupled to the sensor and a control system for displacing the outlet opening(s) at the command of the control system. The dispensing means for the scalding medium can here comprise for instance at least one nozzle.

In order to prevent the scalding medium falling below the condensation temperature on the path which must be covered from the conditioning space to the poultry, it is advantageous if the dispensing means for the scalding medium comprise heating. This can also be advantageous when use of the device temporarily ceases; condensation of the scalding medium in the dispensing means can then be prevented by activating the heating.

The processing space can be embodied as a substantially tunnel-like space. An overhead conveyor as frequently used in poultry slaughterhouses and provided with poultry holders displaceable along the overhead conveyor can be readily carried through such a processing space. The poultry can be suspended by the legs from the poultry holders and thus pass through a transport path defined by the overhead conveyor, and is readily accessible for the feed of scalding medium. At least a part of the dispensing means is here preferably disposed relative to this transport path such that the dispensing means bring a part of the scalding medium into targeted contact with the wings, in particular the underside of the wings of the poultry. The “underside of the wings” is here understood to mean the part of the wing situated on the underside of the wing when a poultry animal is standing on its legs; since during transport through the processing space the poultry is often suspended upside down from the legs, in this situation the underside of the wing will, conversely, be situated on the top side. Bringing the scalding medium into targeted contact with the wings does not otherwise have to be the case along the whole length of the transport path; it is also possible for the scalding medium to come into targeted contact with the underside of the wings of the poultry along only a part of the length of the transport path. It is found in practice that the feathers on the wings of the poultry are particularly difficult to remove; it is precisely for this reason that scalding is expressly undertaken at the position of the wings.

The conditioning space for composing the scalding medium is desirably provided with at least one evaporation space with a feed for liquid. The conditioning space for composing the scalding medium can be embodied even more advantageously with at least two evaporation spaces placed in line, both provided with a feed for liquid, wherein the feed for liquid on the first in-line evaporation space is adapted for operation at a higher temperature than the second evaporation space. For the purpose of conditioning the scalding medium, and more particularly for adjusting the dew point, use can be made of for instance a washer as per se known from the prior art. The advantage of two (or even more than two) evaporation spaces running into each other is that an accelerated evaporation process can first be followed at a higher temperature and that the fine adjustment of the dew point takes place only in the final part of the evaporation process. An example of such a staged process consists of a first step of steam injection and a second step in which a determined medium temperature is set accurately with a 100% air humidity. The process time for conditioning the scalding medium can thus be shortened.

In order to displace the scalding medium from the conditioning space to the processing space the device can be provided with at least one fan, also referred to as blower or ventilator. It is further desirable that the processing space be provided with discharge means for discharging from the processing space condensation and/or gas/liquid mixture which is not (any longer) correctly conditioned. In order to limit the liquid consumption of the device the discharge means of the processing space can feed back at least partially to the conditioning space. In order to prevent scalding medium flowing outside from the processing space at the position where the poultry enters the processing space or at the position where the poultry leaves the processing space, a sluice construction can be applied. Not only is it thus possible to prevent a substantial quantity of scalding medium disappearing (limiting leakage), but the entry of ambient air into the processing space can also be limited in this way. This results in an improved controllability of the process conditions in the processing space. In a possible embodiment variant of a sluice construction upstream of the processing space the feed track leads upward when entering the processing space and leads downward again when leaving the processing space. At the position of the processing space the transport path thus lies in a higher position than in the vicinity of the processing space; because the warm scalding medium will tend to want to displace upward, leakage of scalding medium out of the processing space can thus be limited.

In order to automate the operation thereof, the device can also be provided at other locations, as already described above with reference to the displacement of the dispensing means for liquid in the processing space, with at least one sensor and a control communicating with the sensor. It is possible here to envisage for instance control of the composition of the scalding medium (time, quality and/or volume), the feed of heated liquid (time, quality and/or volume), the transporting speed of the poultry, the drive of the fan and so forth.

The present invention also relates to a method for scalding poultry, comprising the processing steps of: A) composing a scalding medium with a dew point lying in the range of [49-61]° C.; B) carrying into a processing space poultry for scalding which comprises full plumage; and C) supplying the scalding medium to the processing space such that at least one jet of the scalding medium is formed which is directed at the poultry. By means of this method the advantages as already described above with reference to the device according to the present invention can be achieved, such as, among others, a controlled, safe and improved scalding result. Other advantages are, among others, an efficient energy consumption and a reduced chance of cross-contamination/fouling. The dew point of the scalding medium lies in the range of [49-61]° C., preferably in the range of [49-53]° C., of [53-57]° C. or of [57-61]° C. It is precisely in these processing conditions that scalding results will be obtained causing epidermal damage specified respectively as low scald, intermediate scald and high scald. It is also of great importance here that a set dew point can be maintained within any of the above stated ranges within a limited margin of more or less 1° C., preferably even a margin of more or less 0.5° C. It is thus possible to keep the variations in the scalding result acceptably low.

In order to prevent premature condensation of the scalding medium, the scalding medium is preferably 90-100% saturated, more preferably 95-100% saturated when it enters into contact with the poultry during processing step C). Optimum use is thus made of the possibility of heat transfer as a result of condensation. In addition, there will be hardly any drying-out at all of the poultry for scalding during the scalding process in view of the relatively high degree of saturation of the air. (Undesirable) exceeding of the wet bulb temperature will therefore also be prevented.

The jet of scalding medium is advantageously specifically directed at the neck, the wings, the belly and/or the tail of the poultry during processing step C). Defeathering is relatively difficult at these particular locations. In order to compensate for differences in shape in different batches (groups) of poultry, the jet of scalding medium can be set per batch of poultry to be processed. In the case of large differences in shape and size of the poultry for processing it is even possible to opt for having such a setting take place on individual basis.

A jet of scalding medium with a dew point lying in the range of [49-61]° C. comes into contact with the epidermis of the poultry, and in a preferred variant the scalding medium has a temperature which is not much higher than said range of [49-61]° C., so that the chance of overheating of the skin of the poultry can be reduced still further. However, in order to have the process progress sufficiently quickly and to prevent premature condensation, it is still also possible to opt deliberately for operation with a scalding medium having a temperature higher than 60° C., for instance 62° C.

This makes it possible with the method according to the present invention to limit the treatment time of the poultry, more particularly chickens, in the processing space to [60-180] seconds. It will be apparent that a reduction in the processing duration is also possible in the case of poultry other than chickens, such as for instance turkeys and ducks. In order to obtain a uniform scalding result it can also be advantageous for an airflow to be generated in the processing space. It must also be taken into account here that this can result in a wet bulb temperature of the outer side of the poultry on which condensation has taken place which is a fraction lower than the condensation temperature. Discharge of condensed water out of the processing space prevents this water impeding the poultry treatment process. Reuse of the condensed water is possible by using this water once again to compose the scalding medium. Water consumption is thus reduced considerably.

FIGS. 1A and 1Bshow an integrated scalder1with a centrally located generator or conditioning space2to which gas (air) is fed via the top side as according to arrows P1by fans3driven by electric motors4. Liquid washers5are disposed in conditioning space2for bringing a scalding medium to the correct temperature and saturation level. The scalding medium is carried as according to arrows P2to processing spaces7located on either side of conditioning space2. Situated in processing spaces7are overhead conveyors8along which the poultry9for scalding is displaced hanging by the legs. The scalding medium is now blown through openings10in a partition wall in a manner directed into the path in which poultry9is being advanced. Also situated in processing spaces7are collecting basins11with which excess condensation12in processing spaces7can be collected and discharged via conduits13for reuse in conditioning space2(recirculation). For the purpose of recirculation of the collected scalding medium it is desirable that, prior to being reused, it is conditioned such that at least a substantial part of the bacteria present are killed. This is possible for instance by heating the collected scalding medium to a temperature higher than 60° C., preferably a temperature higher than 65° C.

FIGS. 2A and 2Bshow an alternative scalder20with conditioning spaces (generators)21located at a distance from a processing space22. A scalding medium with a dew point lying in the range of [49-61]° C. is carried by means of fans23through tubes24to processing space22as according to arrows P3. Scalding takes place in processing space22, wherein the poultry for scalding25is carried in processing space22through scalding medium supplied through tubes24by means of jets directed at the poultry for scalding. The mixture discharged from processing space22is fed back by means of return conduits26to conditioning spaces21. The advantage of the scalder20shown inFIGS. 2A and 2Bis that conditioning spaces21can be placed at a distance from processing space22such that a production space can be utilized optimally. The modular construction of the system also provides advantages in production (purchasing), transport, placing and maintenance.

FIG. 3shows a cross-section through a schematically represented scalder30with a processing space31through which poultry32is carried in four rows along overhead conveyors33. In a conditioning space34adjacent to processing space31a scalding medium is brought by washers35and a basin36with heating37to a desired dew point lying in the range of [49-61]° C. and a desired temperature. For this purpose the washers35and basin36are connected to a hot water boiler38, and the whole conditioning process is controlled by a control39. The scalding medium created in conditioning space34is blown through conditioning space34by a fan45and then blown through openings40in a plate41into blow pipes42. The scalding medium leaves blow pipes42through nozzles43arranged for this purpose at specific heights. The position of nozzles43is such that the jets of scalding medium leaving nozzles43are aimed directly at the paths through which poultry32is passing. Since poultry33hangs downward by legs44and nozzles43are also directed downward, the scalding medium will penetrate relatively easily under the feathers of poultry32. Once it has been in contact with poultry32, the scalding medium present in processing space31will be discharged again by fan45and reconditioned in conditioning space34to a scalding medium with a desired dew point lying in the range of [49-61]° C. and a desired temperature.

FIG. 4shows a slaughtered chicken50which is suspended in a holder51on an overhead conveyor52in a processing space not further shown in this figure. For the purpose of supplying a scalding medium with a dew point lying in the range of [49-61]° C. such that this is aimed directly at chicken50, spray heads53,54are placed in the processing space, in particular such that the neck55and wings56of chicken50are scalded more intensively than the other parts of chicken50. The position of spray heads53,54is vertically displaceable (see arrows P4). Feed conduits57,58for scalding medium coupled to the respective spray heads53,54are slidable in guides59for this purpose. The positioning of spray heads53,54can be automatically optimized by means of a camera60, the signal from which is carried by a signal line61to a control unit62. This control unit62subsequently controls the position of spray heads53,54by means of control lines63.

FIG. 5shows a schematically represented staged conditioning space70which consists of a first chamber71to which a gas for saturating is fed as according to arrow P5. In chamber71are placed washers72which are operated at a relatively higher temperature than that which the scalding medium ultimately has to have. Before the medium in chamber71reaches the operating temperature of washers72, this preheated scalding medium is carried further as according to arrow P6to a second chamber73with washers74. These washers74operate at a lower temperature than washers72in first chamber71. A considerable saturation and temperature increase of the medium can thus be rapidly realized in first chamber71, for instance by steam injection, while the fine adjustment of a precisely determined dew point is brought about in second chamber73For supply to washers72,74respective independent circulation systems75,76can be supplied by a combined supply system77which is shown only very generally.

FIG. 6Ashows a perspective view of an alternative embodiment variant of a processing space80of a device according to the present invention, whileFIG. 6Bshows the cross-section through this processing space80. Two transport paths81for poultry83here enter processing space80parallel to each other. The standing side walls82of processing space80are formed such that the volume of processing space80is limited without this limiting the possible throughfeed of poultry83. A smaller volume of processing space80has the advantage that the process conditions in processing space80can be better controlled and that the scalding medium is employed more effectively. A blower unit85is placed centrally on the upper side84of processing space80midway between transport paths81, whereby the volume of processing space80is limited still further. The hollow interior86of blower unit85also functions as feed channel for the scalding medium, and openings87are arranged in the wall of blower unit85such that the supplied scalding medium exits as according to arrows P7(seeFIG. 6B) in a direction toward poultry83. In this way it is also possible in advantageous manner to blow on the socks (i.e. the feathers connecting to the legs) of poultry83. In similar manner openings88are also arranged in the standing side walls82of processing space80, whereby scalding medium exits as according to arrows P8(seeFIG. 6B) in a direction toward poultry83, The supply of scalding medium from standing side walls82is advantageous, among other reasons because it is hereby possible to also blow the scalding medium properly onto the wings directed toward these side walls82; among others, the feathers on the wings are often difficult to remove in prior art scalding. The supply of the scalding medium to openings88in standing side walls82takes place through intermediate spaces89left clear for this purpose in the side walls.

As an alternative to the outflow openings87,88in standing side walls82and the blower unit85, is also possible to arrange separate pipes with nozzles in processing space80. Such an alternative embodiment variant of a processing space90of a device according to the present invention is shown inFIG. 7. In addition to being provided with the elements already known from foregoing figures, such as two transport paths91for poultry92, processing space90is also provided with a number of centrally disposed nozzles93and nozzles94disposed on the longitudinal sides of processing space90. Nozzles93,94are disposed such that they blow scalding medium onto poultry92from different heights and from different directions. It is optionally also possible to embody processing space90such that the position of nozzles93,94is changed subject to the quality of the poultry92for processing.

It is noted, perhaps unnecessarily, that a processing space with a combination of blow pipes as shown inFIG. 7and outflow openings87,88and blower unit85as shown inFIG. 6is also possible according to the present invention.