Rapid chill process for poultry carcasses

Abstract

Poultry carcasses are chilled rapidly when exposed to a flow of gaseous air at a temperature in the range from about 50 C. to about 120 C. for a period of time in the range from about 1 s to about 60 s. The flow is directed over and into the body cavity of the carcasses. The carcasses are orientated in the flow such that the sternum of each carcass faces downstream. One advantage of the process is that the number of viable microorganisms present on the carcasses is reduced significantly while avoiding freeze-damage to the carcasses.

Claims

1. A process for rapidly chilling poultry carcasses to reduce the number of viable microorganisms present thereon, said process comprising: conveying poultry carcasses through an insulated chill chamber for a period of time in the range from about 1 s to about 60 s; circulating gaseous air that has been warmed by the carcasses from the chill chamber through a first duct to a heat exchanger; cooling the air in the heat exchanger by indirect heat exchange with a liquid cryogen to create chilled air at a temperature in the range from about 50 C. to about 120 C.; circulating the chilled air from the heat exchange through a second duct back to the chill chamber; and flowing the chilled air over said carcasses and into the body cavity of said carcasses, wherein said carcasses are orientated such that the sternum of each carcass faces downstream with respect to the flow of the chilled air.

2. A process according to claim 1, wherein said poultry carcasses are conveyed on a continuous shackle line that passes through said flow of said gaseous air.

3. A process according to claim 1, wherein a first plurality of said poultry carcasses is conveyed on a first continuous shackle line through a first flow of said gaseous air, and a second plurality of said poultry carcasses is conveyed simultaneously and in parallel on a second continuous shackle line through a second flow of said gaseous air, said first and second flows of gaseous air being provided from a common duct located between said parallel shackle lines.

4. A process according to claim 1, wherein said flow of gaseous air is in the form of a planar sheet.

5. A process according to claim 1, wherein said temperature is lower than 75 C.

6. A process according to claim 1, wherein said temperature is no lower than about 110 C.

7. A process according to claim 1, wherein said temperature is about 100 C.

8. A process according to claim 1, wherein said period of time is at least 15 s.

9. A process according to claim 1, wherein said period of time is no more than about 55 s.

10. A process according to claim 1, wherein said period of time is in the range from about 30 s to about 45 s.

11. A process according to claim 1, wherein said carcasses are pre-chilled to an initial temperature in the range from about +7 C. to about 1 C. prior to exposure to said flow of gaseous air.

12. A process according to claim 1, wherein after said exposure to said gaseous air, said carcasses are allowed to recover by natural warming.

13. A process according to claim 1, wherein after said exposure to said gaseous air, said carcasses are allowed to equilibrate for a period of time of at least 5 mins before further processing.

14. A process according to claim 13, wherein said equilibration time is no more than 30 mins.

15. A process according to claim 1, wherein said flow of gaseous air has a flow rate from about 1500 m.sup.3/h to about 2500 m.sup.3/h.

16. Apparatus for rapidly chilling poultry carcasses to reduce the number of viable microorganisms thereon, said apparatus comprising: an insulated chill chamber having an entry port and an exit port; a continuous shackle line located within said chill chamber for conveying poultry carcasses from said entry port to said exit port; a heat exchanger for cooling air by indirect heat exchange against a liquid cryogen; at least one nozzle located parallel to said continuous shackle line for feeding a flow of cooled air into said chill chamber in the form of a planar sheet, said nozzle being arranged to direct said flow over said carcasses and into the body cavity of said carcasses on said shackle line; a first duct for feeding cooled air from said heat exchanger to said nozzle(s); a second duct for feeding warmed air from said chill chamber to said heat exchanger; and a fan for circulating air from the chill chamber through the second duct, across the heat exchanger, and through the first duct to the chill chamber.

17. Apparatus according to claim 16, comprising two continuous shackle lines in parallel and at least one nozzle having a rectangular aperture for each shackle line, said first duct being common to said at least one nozzle.

Description

(1) Examples of the present invention will now be described with reference to the figures in which:

(2) FIG. 1 is a schematic representation of apparatus used to test the process according to the present invention;

(3) FIG. 2 is a schematic representation in part of one embodiment of apparatus according to the present invention involving at least one continuous shackle line and a duct providing twin flows of super-chilled gaseous air;

(4) FIG. 3 is a partial cross-sectional view of another embodiment of apparatus according to the present invention involving at least one continuous shackle line and a duct providing twin flows of super-chilled gaseous air; and

(5) FIG. 4 is a schematic representation in part of a further embodiment of apparatus according to the present invention involving a section of continuous shackle line passing through a rapid chiller retro-fitted to an existing continuous shackle line from a conventional chiller.

(6) In FIG. 1, there is depicted a batch chiller 2 comprising an insulated chill chamber 4 with an entry/exit port 6 for introducing chicken carcasses 8 to be chilled into the chiller 2 and for removing chilled carcasses from the chiller 2. Each carcass 8 is hung upside-down from a shackle (not shown) by the legs in front of a series of nozzles 10 provided in a row in the wall of a first duct 12. The carcasses are orientated such that the breast faces away from the nozzles 10 and downstream in the flow of gaseous air.

(7) A heat exchanger 14 is provided in which air is cooled to a temperature in the range from about 50 C. to about 120 C., e.g. about 100 C., by indirect heat exchange against liquid nitrogen provided from a liquid nitrogen supply 16. The liquid nitrogen is evaporated and vented 18 to a safe location.

(8) The super-chilled air passes through the first duct 12 to the nozzles 10. The flow of air from the nozzles is in the form of a sheet which is directed downwards over the exterior surface of the carcasses and into the body cavity through the entrance at the rear end of the carcasses. After cooling the carcasses, the air is circulated back to the heat exchanger 14 through a second duct 22.

(9) Air is circulated around the chiller 2 using a fan 24.

(10) In FIG. 2, there are depicted two sections 26, 28 of shackle line(s) suitable for use in a continuous chilling process. The sections 26, 28 could form part of the same single shackle line in which case the sections would be moving in opposite directions (as in FIG. 4), or could each form part of the different lines in a twin shackle line in which case the sections would be moving in the same direction.

(11) The first and second sections 26, 28 of shackle line(s) are provided in parallel with a first duct 12 located therebetween providing twin flows of super-chilled gaseous air. Each section of line has a plurality of shackles 30 by which poultry carcasses 8 are hung upside-down in front of the nozzles 10. The sections 26, 28 of shackle line move the carcasses 8 through the flows of gaseous air.

(12) As depicted in detail in the inset, the carcasses are orientated such that the sternum of each bird faces downstream. The flow of gaseous air is directed over the exterior surface of the carcasses, and into the body cavity through the entrance at the rear end.

(13) The breast-out orientation of the birds is depicted in FIG. 3. This figure also depicts the preferred angle of about 45 for the twin flows of super-chilled gaseous air.

(14) FIG. 4 depicts one possible configuration for a shackle line through a rapid chiller (not shown) that has been retro-fitted to a shackle line from a conventional chiller (not shown).

(15) The features in FIGS. 3 and 4 that are common to FIGS. 1 and 2 have been given the same reference numerals.

EXAMPLE 1

(16) A series of trials using a batch chiller according to FIG. 1 have been carried out. Since levels of Campylobacter infection in poultry flocks vary from one location to another in the UK, the different trials involved chicken flocks from different locations in the UK. The different flocks had different initial levels of Campylobacter infection.

(17) In each trial, the chickens were slaughtered, defeathered and eviscerated, and the head and feet were removed. A flap of skin from the neck was left on each carcass.

(18) The level of Campylobacter infection was measured before and after the rapid chill treatment. In this regard, half of the neck flap was removed prior to treatment and tested for Campylobacter infection. The remaining half of the neck flap was then removed after treatment and also tested for Campylobacter infection.

(19) The carcasses of different sized birds from different geographical locations were hung in the chiller such that the sternum of each bird was facing downstream, and then exposed to a flow (2000 m.sup.3/h) of super-chilled air at different temperatures (60 C., 80 C. or 100 C.) for different periods of time (30 s, 40 s and 50 s). The angle at which the flow of super-chilled air impinged on the carcass was about 45.

(20) The carcasses were inspected visually after each chill cycle, paying particular attention to the quality, discoloration and texture of the breast meat. In this regard, no discoloration or texture changes were apparent on the meat after the skin was removed for carcasses exposed to the super-chilled air at 100 C. for 30 s, 40 s or 50 s and the meat therefore met the required quality standard.

(21) The level of Campylobacter infection both before and after treatment was measured using the colony-count technique described in Part 2 of the Technical Specification entitled Microbiology of food and animal feed stuffsHorizontal method for detection and enumeration of Campylobacter ssp. (DD ISO/TS 10272-2:2006). This technique involves inoculating a selective agar medium (modified charcoal cefoperazone deoxycholate or mCCD agar) with specified quantities of dilutions of a test sample and incubating the plates at 41.5 C. in a micro-aerobic atmosphere for 40 h to 48 h. The colonies presumed to be Campylobacter are subcultured on a non-selective agar medium (Colombia blood agar), then confirmed by means of microscopic examination and appropriate biochemical and growth tests. The number of Campylobacter per gram of the test sample is calculated from the number of confirmed typical colonies per plate.

(22) The results from these trials are provided in the following table:

(23) TABLE-US-00001 Trial T.sub.air EV weight Infection before Infection after Log % No. Location ( C.) 30 s 40 s 50 s (kg) (cfu/g) (cfu/g) reduction kill 1 Hertfordshire #1 100 x x 2.46 1000 50 2.3 95.0 100 x x 2.46 10000 20 2.7 99.8 100 x x 2.46 2400 20 2.1 99.2 2 Essex 100 x x 1.78 20000 200 2.0 99.0 100 x x 1.79 2300 40 1.8 98.3 100 x x 1.80 510 30 1.2 94.1 100 x x 1.84 5222 64 1.6 98.8 100 x x 1.84 33264 437 2.2 98.7 100 x x 1.84 4804 22 2.7 99.6 3 Perthshire 100 x x 1.30 3000 33 2.0 98.7 100 x x 1.31 160000 2100 1.9 99.7 100 x x 1.32 12000 38 2.5 97.5 4 Hertfordshire #2 100 x x 1.85 270000 40 3.8 100.0 100 x x 1.85 23000 49 2.7 99.8 100 x x 1.85 20000 60 2.5 99.7 100 x x 1.91 23000 50 2.7 99.8 100 x x 1.91 13000 150 1.9 98.8 100 x x 1.91 14000 100 2.1 99.3 5 Cambridgeshire #1 100 x x 1.86 145000 50 3.5 100.0 100 x x 1.86 13000000 7000 3.3 99.9 100 x x 1.86 830000 57 4.2 100.0 6 Cambridgeshire #2 100 x x 1.85 710000 530 3.1 99.9 100 x x 1.85 690000 90 3.9 100.0 100 x x 1.85 2800 10 2.4 99.6 7 Suffolk #1 80 x x 1.69 50000 6000 0.9 88.0 80 x x 1.69 28000 560 1.7 98.0 80 x x 1.69 11000 640 1.2 94.2 8 Suffolk #2 60 x x 1.66 470 10 1.7 97.9 60 x x 1.66 800 10 1.9 98.8 60 x x 1.66 800 10 1.9 98.8

EXAMPLE 2

(24) During the test program of Example 1, several chilling cycles were completed in which the six poultry carcasses were hung in the shackles the other way round, i.e. breast inwards, and then exposed to the flow of super-chilled air at 100 C. for 30 s, 40 s or 50 s.

(25) After the chill cycle, the carcasses were inspected visually. Discoloration and texture changes were visually apparent on the breast meat of almost all of the birds after the skin was removed.

(26) While the invention has been described with reference to the preferred embodiments depicted in the figures, it will be appreciated that various modifications are possible within the spirit or scope of the invention.

(27) In this specification, unless expressly otherwise indicated, the word or is used in the sense of an operator that returns a true value when either or both of the stated conditions are met, as opposed to the operator exclusive or which requires only that one of the conditions is met. The word comprising is used in the sense of including rather than to mean consisting of. All prior teachings above are hereby incorporated herein by reference. No acknowledgement of any prior published document herein should be taken to be an admission or representation that the teaching thereof was common general knowledge in Australia or elsewhere at the date thereof.