Abstract:
A method of cooling foodstuff comprises immersing at least one perforated container containing foodstuff into an ice slurry bath for a period of time sufficient to allow ice slurry to enter the at least one perforated container and then subsequently removing the at least one perforated container from the ice slurry bath. Various apparatuses for cooling foodstuff are also provided.

Description:
This application is the national phase under 35 U.S.C. §371 of PCT International application Ser. No. PCT/CA2007/001599 which has an International filing date of Sep. 12, 2007, which claims priority to Canadian Patent application No. CA 2562722 filed Sep. 12, 2006; the entire contents of each of which are hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a method and apparatus for cooling foodstuff. 
     BACKGROUND OF THE INVENTION 
     As is well known, in many environments to preserve freshness and inhibit spoiling, foodstuff is often cooled or chilled prior to serving and/or shipping. For example, fishing vessels typically carry refrigeration equipment to allow fish to be chilled as the fish are caught. In this manner, the fish does not spoil and remains edible even over lengthy voyages. Vegetables that are transported by truck or rail are also typically refrigerated during transit to prevent spoiling. Many refrigeration techniques have been employed and include for example, air conditioning units and ice-making machines that produce ice. In the latter case, ice-making machines that produce a slurry of fine ice crystals in a solution have been used to chill food product such as fish and vegetables. 
     One exemplary type of ice-making machine of this type is disclosed in U.S. Pat. No. 4,796,441 to Goldstein, assigned to the assignee of the subject application, the content of which is incorporated herein by reference. This ice-making machine has a chamber with a fluid inlet to receive a brine solution from which ice is to be made and a fluid outlet to permit the egress of an ice-brine slurry from the chamber. The interior surface of the chamber defines a heat exchange surface. A tubular jacket surrounds the chamber. A refrigerant inlet and a refrigerant outlet communicate with the space between the jacket and chamber and are positioned at opposite ends of the ice-making machine. Refrigerant flowing through the space between the inlet and the outlet boils and in so doing, cools the brine solution in contact with the heat exchange surface. Refrigerant leaving the ice-making machine via the outlet is condensed and compressed before being fed back to the refrigerant inlet. A blade assembly is mounted on a rotatable shaft extending through the center of the chamber and is in contact with the heat exchange surface. A motor rotates the shaft so that the blade assembly removes a cooled layer of brine solution in contact with the heat exchange surface and directs the removed cooled layer into a body of brine solution within the chamber. The shaft is rotated at a rate such that the interval between successive passes of the blade assembly over the heat exchange surface inhibits the formation of ice crystals on the heat exchange surface. 
     Alternatively, the ice-making machine may be of the type disclosed in U.S. Pat. Nos. 5,884,501, 6,056,046 and 6,286,332 to Goldstein and assigned to the assignee of the subject application, the content of which is incorporated herein by reference. This ice-making machine includes a housing having a brine solution inlet to receive brine solution from which ice is to be made and an ice-brine slurry outlet to permit the egress of an ice-brine slurry from the housing. A heat exchanger within the housing has a heat exchange surface, a refrigerant inlet, a refrigerant outlet and at least one refrigerant circuit interconnecting the refrigerant inlet and the refrigerant outlet. Refrigerant flows through the at least one refrigerant circuit between the refrigerant inlet and the refrigerant outlet to extract heat from the brine solution contacting the heat exchange surface. A blade assembly within the housing carries a plurality of blades, each of which is in contact with the heat exchange surface. The blade assembly is mounted on a shaft, which is rotated by a motor at a rate such that the blades move across the heat exchange surface and remove cooled fluid therefrom thereby to inhibit the deposition of ice crystals on the heat exchange surface. 
     U.S. Pat. No. 4,936,102 to Goldstein et al., assigned to the assignee of the subject application, discloses an apparatus for cooling fish on board a ship employing for example, an ice-making machine of the type disclosed in aforementioned U.S. Pat. No. 4,796,441. The outlet of the ice-making machine is connected to a pump leading to a flexible hose. The flexible hose can be carried either to a vessel containing salt water or to a catch of fish to direct ice slurry produced by the ice-making machine directly to the catch of fish or to the vessel. 
     Depending on the product to be cooled and its packaging, delivering ice slurry such as that produced by the ice-making machines described above, can present challenges. For example, it is known to use a manifold to direct an incoming ice slurry to a plurality of stacked, perforated containers simultaneously. For example,  FIGS. 1   a  and  1   b  show top and side elevational views of such a manifold  100 . As can be seen, the manifold  100  is in abutment with one side of a rectangular array of stacked perforated containers  110  that are filled with foodstuff and that rests on a pallet  120 . During cooling of the foodstuff in the containers  110 , ice slurry is delivered to the inlet of the manifold  100 . The ice slurry in turn is discharged by the manifold  100  toward each row of containers  110  via its outlets. Discharged ice slurry in turn enters the containers  110  via the perforations therein. The foodstuff in the containers  110  acts as a filter, trapping ice crystals while allowing the liquid portion of the ice slurry to drain and exit the containers  110  through the perforations. In this manner, the containers  110  become packed with ice crystals. Unfortunately, during this process it is very difficult, if not impossible, to control the amount of ice deposited in each container  110 . As each container needs to be packed with ice, this uncertainty can be problematic. 
     It is therefore an object of the present invention to provide a novel method and apparatus for cooling product. 
     SUMMARY OF THE INVENTION 
     Accordingly, in one aspect there is provided an apparatus for cooling foodstuff comprising: 
     a tank containing an ice slurry bath, said tank being sized to receive a stack of perforated containers containing foodstuff with said stack of containers being immersed in said ice slurry bath; and 
     at least one agitator to agitate the ice slurry bath. 
     In one embodiment, the at least one agitator is positioned in the tank within the ice slurry bath. The at least one agitator may comprise for example at least one rotating paddle. Alternatively, the at least one agitator may comprise at least one nozzle discharging ice slurry into the tank. In this latter case, a pump draws ice slurry from the tank and delivers the ice slurry to the at least one nozzle. The at least one nozzle may be positioned in the tank within the ice slurry bath or in the tank above the ice slurry bath. A sensor to monitor the ice fraction of the ice slurry bath within the tank may also be provided. 
     According to another aspect there is provided an apparatus for cooling foodstuff comprising: 
     at least one tank containing an ice slurry bath and adapted to receive foodstuff to be cooled; 
     at least one nozzle within said tank to receive ice slurry and discharge said ice slurry into said tank; and 
     at least one pump to draw ice slurry from said ice slurry bath and deliver the ice slurry to said at least one nozzle. 
     In one embodiment, the at least one nozzle is positioned above the ice slurry bath. Foodstuff received by the tank is immersed in the ice slurry bath. At least one support frame may be provided within the tank onto which foodstuff is placed. In this case, the at least one support frame comprises individual foodstuff compartments and may be oscillated within the tank. 
     In an alternative embodiment, the at least one nozzle discharges ice slurry onto foodstuff suspended above the ice slurry bath. 
     In yet another embodiment, the apparatus comprises a plurality of stacked tanks, with each tank containing an ice slurry bath and at least one nozzle. The at least one pump delivers ice slurry to at least one of the nozzles. For example, the at least one pump may deliver ice slurry to the at least one nozzle of the uppermost tank in the stack with the nozzles of other tanks of the stack receiving ice slurry from overhead tanks. An oscillator may be provided to oscillate the stack of tanks. 
     According to yet another aspect there is provided an apparatus for cooling foodstuff comprising: 
     a tank adapted to receive foodstuff to be cooled and receiving a supply of ice crystals; and 
     at least one manifold within said tank having a plurality of outlets, said manifold receiving a supply of inlet air and discharging received air via said outlets in a manner to suspend ice crystals and create a fluidized ice crystal bed within said tank. 
     In one embodiment, the apparatus further comprises at least one blower drawing at least air from an intake port coupled to the tank and supplying air to the at least one manifold. The blower may draw both air and ice crystals from the tank. 
     According to still yet another aspect there is provided an apparatus for cooling foodstuff comprising: 
     a rotating drum comprising an inlet receiving foodstuff to be cooled and an outlet to discharge cooled foodstuff, said drum further comprising an ice crystal inlet receiving a supply of ice crystals; and 
     a foodstuff advancing mechanism to advance foodstuff from said inlet to said outlet as said drum rotates. 
     In one embodiment, the foodstuff advancing mechanism comprises formations on an interior surface of the drum that are shaped to advance the foodstuff. The drum may further comprise at least one drainage passage and may be inclined in a direction from the inlet to the outlet. 
     According to still yet another aspect there is provided a method of cooling foodstuff comprising: 
     immersing at least one perforated container containing foodstuff into an ice slurry bath for a period of time sufficient to allow ice slurry to enter said at least one perforated container; and then 
     subsequently removing said at least one perforated container from said ice slurry bath. 
     According to still yet another aspect there is provided a method of cooling foodstuff comprising: 
     exposing foodstuff to ice crystals to cool said foodstuff; and 
     agitating said ice crystals at least during said exposing. 
     The apparatus and method promote rapid cooling of foodstuff and generally achieve uniform contact between ice crystals and the foodstuff. Further, the apparatus allows the volume of the ice crystals surrounding the foodstuff to be controlled. These are important factors in the process of preservation and transportation of foodstuff. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will now be described more fully with reference to the accompanying drawings in which: 
         FIGS. 1   a  and  1   b  are top plan and side elevational views of a prior art container cooling technique; 
         FIGS. 2   a  and  2   b  are side elevational views of an apparatus for cooling product; 
         FIG. 3  is a side elevational view of an apparatus for chilling product; 
         FIG. 4   a  is a side elevational view of another embodiment of an apparatus for cooling product; 
         FIG. 4   b  is a side elevational view of yet another embodiment of an apparatus for cooling product; 
         FIG. 5  is a side elevational view of yet another embodiment of an apparatus for cooling product; 
         FIG. 6  is a side elevational view of yet another embodiment of an apparatus for cooling product; 
         FIG. 7  is a side elevational view of still yet another embodiment of an apparatus for cooling product; and 
         FIG. 8  is a side elevational view of still yet another embodiment of an apparatus for cooling product. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Turning now to  FIGS. 2   a  and  2   b , an apparatus for cooling product held in containers, such as for example perforated boxes, is shown and is generally identified by reference numeral  150 . In this embodiment, the apparatus  150  comprises an opened top tank  152  filled with an ice slurry bath  154 . The ice slurry bath  154  may be produced by one of the ice-making machines described above or may simply be crushed ice and water. Agitators  156  are provided adjacent at least two sides of the tank  152  to maintain the ice slurry bath  154  in the tank in an agitated state thereby to inhibit conglomeration of ice crystals and ensure a general even distribution of ice crystals throughout the ice slurry bath  154 . The agitators  156  are in the form of blades on paddles  156   a  mounted on upright rotating shafts  156   b  at different elevations. One or more motors (not shown) are coupled to the shafts  156   b  either directly or via gear trains (not shown) to rotate the shafts. A sensor  158  including a calorimeter is mounted on the tank  152  to sense the ice fraction of the ice slurry bath  154  within the tank  152 . When the sensor  158  detects that the ice fraction of the ice slurry bath in the tank  152  has dropped below a threshold level, the sensor provides an output signal which is used to control operation of ice-making equipment so that ice crystals are added to the ice slurry bath  154  thereby to increase the ice fraction until it reaches the desired level. For example, the signal from the sensor  158  may be used to actuate an ice storage and distribution unit such as that disclosed in U.S. Pat. No. 4,912,935 to Goldstein, assigned to the assignee of the subject application, the content of which is incorporated herein by reference, resulting in ice flakes being discharged from the ice storage and distribution unit into the tank  152 . 
     The tank  152  is sized to accommodate a stack of perforated containers filled with foodstuff allowing the entire stack to be submersed in the ice slurry bath  154 . In this manner, the foodstuff in a plurality of containers  210  can be chilled simultaneously allowing the apparatus  150  to maintain an effective throughput. During use as shown in  FIG. 2   a , the stack of the containers  210  is lowered into the tank  152  and immersed in the ice slurry bath  154 . Once immersed, ice slurry flows into the containers  210  through the perforations therein until the containers are flooded with ice slurry. Agitation of the ice slurry helps to establish a generally continuous flow of ice slurry through the containers  210 . 
     As stated previously, the foodstuff in the containers  210  acts as a filter trapping ice crystals resulting in the containers becoming packed with ice crystals. The stack of containers  210  is typically allowed to sit immersed in the ice slurry bath  154  for a period of time sufficient to ensure the containers become generally packed with ice crystals. By immersing the entire stack of containers  210  in the ice slurry bath  154  and agitating the ice slurry bath  154 , an even distribution of ice crystals within the containers  210  of the stacks is generally maintained. 
     Following this, the stack of containers  210  is lifted from the ice slurry bath  154  as shown in  FIG. 2   b , allowing the liquid portion of the ice slurry to drain out of the containers  210  through the perforations and back into the tank  152  as shown by arrow  212 , leaving the ice crystals trapped inside the containers  210 . In order to immerse and remove the stack of containers  210  from the ice slurry bath  154 , a lift (not shown) such as a forklift or a conveyer line is employed. 
     As will be appreciated, as the ice fraction of the ice slurry bath  154  is monitored by the sensor  158 , the amount of ice crystals trapped within the containers  210  can be determined by measuring the drop in the ice fraction of the ice slurry bath upon removal of the stack of containers. In this manner the amount of ice crystals trapped in the containers  210  can be controlled by adjusting the period of time in which the stack of containers  210  is allowed to sit immersed in the ice slurry bath  154 , by controlling the extent of ice slurry bath agitation and/or by adjusting the ice fraction of the ice slurry bath. 
     The volume of the ice crystals trapped inside the containers  210  may be increased by dipping the stack of containers  210  into the ice slurry bath  154  repeatedly. Depending on the foodstuff to the chilled, performance of the apparatus  150  may be further enhanced by varying the ice crystals of the ice slurry bath  154  and/or by changing the chemical composition of the ice slurry bath. For example, salt may be added to the ice slurry bath  154  and/or the ice crystal size may be changed to alter the flow characteristics of the ice slurry bath. 
     Funnels or traps can also be placed strategically around the stack of containers  210  so that when the stack of containers is lifted from the ice slurry bath, ice slurry flows downwardly through the stack of containers from top to bottom. Proper positioning of such devices helps to achieve a more uniform distribution of the ice crystals throughout the stack of containers. Different distributions of perforations in containers  210  may also be used to effect ice crystal distribution. 
     If desired, the ice slurry bath may be treated so that foodstuff in the containers  210  is washed and sterilized when immersed in the ice slurry bath  154 . For example, ozone, chlorine or other subtle additives may be added to the ice slurry bath. Alternatively, in addition fine gas bubbles may be introduced into the ice slurry bath  154  to lift dirt or other contaminants from the foodstuff. 
     As will be appreciated, unlike the prior art, the apparatus  150  allows the volume of ice crystals that remains in the containers  210  to be controlled and ensures intimate contact between foodstuff in the containers and ice crystals. The immersion process also inhibits mechanical damage to foodstuff during the icing process, as the foodstuff typically floats in the ice slurry bath  154  during the icing process. In conventional methods, foodstuff may be crushed by ice. 
       FIG. 3  shows an alternative apparatus  250  for chilling product such as foodstuff very similar to that of  FIGS. 2   a  and  2   b . In this embodiment, the apparatus similarly comprises a tank  252  filled with an ice slurry bath  254 . Rather than employing agitators, nozzle assemblies  256  are provided adjacent at least two sides of the tank  252 . Each nozzle assembly  256  has a series of nozzles  256   a  pointing inwardly towards the center of the tank  252 . A pump  260  has an inlet coupled to a drain adjacent the bottom of the tank  252  and an outlet coupled to the nozzle assemblies  256 . In this manner, ice slurry in the tank  252  is circulated from the tank through the pump  260  and to the nozzle assemblies  256 . The ice slurry is in turn discharged by the nozzles  256   a  towards the center of the tank  252  to maintain the ice slurry bath  254  in an agitated state. To enhance distribution of ice slurry, deflectors can be positioned within the tank to direct ice slurry exiting the nozzles  256   a  either towards or away from the stack of containers. A sensor  258  including a calorimeter is similarly mounted on the tank  252  to sense the ice fraction of the ice slurry bath  254  within the tank. 
     The operation of the apparatus  250  is virtually identical to that of apparatus  150 . Stacks of containers  210  are immersed in the ice slurry bath  254  so that the ice slurry enters the containers  210  resulting in ice crystals being trapped within the containers. As will be appreciated, use of the nozzle assemblies  256  increases the degree of agitation of the ice slurry bath  254  and hence ice slurry flow through the containers  210 . This enables the containers to be more densely packed with ice crystals or the throughput of the apparatus to be increased as compared to apparatus  150 . 
     If desired, agitators similar to those shown in  FIGS. 2   a  and  2   b  can be used in conjunction with the nozzle assemblies  256 . 
     For the embodiments of  FIGS. 2   a ,  2   b  and  3 , rather than employing agitators or nozzle assemblies to agitate the ice slurry bath, the ice slurry bath can also be agitated through movement of the stack of containers within the tank. 
     Turning now to  FIG. 4   a , another apparatus for cooling product is shown and is generally identified by reference numeral  320 . The apparatus  320  is best suited for chilling foodstuff with high thermal mass and low thermal conductivity. Cooling of such foodstuff requires a longer time and is generally limited not by the heat transfer from the ice slurry, but by the internal flow of heat. As can be seen, the apparatus  320  comprises a plurality of stacked tanks  340   a  to  340   c , each tank of which is filled with an ice slurry bath  342 . The ice fraction of each ice slurry bath  342  is adjusted to meet specific cooling and heat transfer requirements by monitoring the ice fraction of the ice slurry bath in each tank using for example sensors of the type described above and introducing ice into the ice slurry baths when appropriate. The temperature of the ice slurry baths  342  can also be adjusted by changing the concentration of temperature depressants in the ice slurry baths  342 . 
     A nozzle assembly  344  having a series of nozzles  344   a  is provided adjacent the top of each tank  340   a  to  340   c  and sprays ice slurry into its associated tank. A pump  350  has its inlet coupled to a drain adjacent the bottom tank  340   a  and its outlet coupled to the nozzle assembly  344  of the uppermost tank  340   c . A conduit  352  extending from the base of the top tank  340   c  supplies ice slurry to the nozzle assembly  344  of the middle tank  340   b  under the influence of gravity. Similarly, a conduit  354  extending from the base of the middle tank  340   b  supplies ice slurry to the nozzle assembly  344  of the bottom tank  340   a  under the influence of gravity. 
     During use, foodstuff  360  is placed into the ice slurry baths  342 . The foodstuff  360  may have a surface package or by its specific nature, may resist mixing with the ice slurry baths  342 . In any event, cooling occurs predominantly by contact between the ice slurry baths  342  and the outer surfaces of the foodstuff  360  and by conduction within the foodstuff  360 . To enhance heat transfer between the foodstuff  360  and the ice slurry baths  342 , the levels of the ice slurry baths within the tanks  340   a  to  340   c  can be varied. Also, small agitation devices can be provided in the tanks  340   a  to  340   c.    
     If desired, as shown in  FIG. 4   b , the stacked tanks  340   a  to  340   c  can be oscillated as identified by arrow  370  thereby to agitate the ice slurry baths  342  within the tanks. Movement of the foodstuff  360  as a result of the oscillating tanks  340   a  to  340   c , displaces the ice slurry baths  342  helping to improve heat transfer between the foodstuff  360  and the ice slurry baths  342 . 
       FIG. 5  shows yet another apparatus  420  for cooling foodstuff. In this embodiment, the apparatus  420  comprises a tank  422  filled with an ice slurry bath  424 . A nozzle assembly  426  having a series of nozzles  426   a  is provided adjacent the top of the tank  422  and sprays ice slurry into the tank thereby to agitate the ice slurry bath. A pump  428  has its inlet coupled to the bottom of the tank  422  and supplies ice slurry drawn from the tank to the nozzle assembly  426 . A support frame  430  is disposed within the tank  422  below the top level of the ice slurry bath  424  and is coupled to a vibrating device  432 . The support frame  430  has a plurality of compartments  430   a , each of which receives one or more pieces of foodstuff  434 . During operation, foodstuff  434  are placed in the compartments  430   a  of the support frame  430  and the support frame is vibrated via the vibrating device  432 . Vibration of the support frame  430  supplements agitation of the ice slurry bath  424  thereby ensuring adequate flow of ice slurry around the foodstuff  434 . 
     If desired, the ice slurry bath  424  can be further agitated by introducing gas bubbles into the bottom of the tank  422 . The apparatus  420  is beneficial for the cooling of foodstuff where cross-contamination is a problem, as the support frame  430  supports foodstuff  434  in individual compartments  430   a.    
     Referring to  FIG. 6 , yet another apparatus  450  for cooling foodstuff  460  is shown. In this embodiment, the apparatus  450  comprises an enclosed tank  470  having an intake port  472  adjacent the top of the tank. The intake port  472  is coupled to a blower  474  that feeds air to an exhaust port  476  adjacent the bottom of the tank  470 . An air injection manifold  478  having a series of outlets is positioned adjacent the bottom of the tank  470  and is coupled to the exhaust port  476 . An ice crystal inlet port  480  is provided in the top of the tank  470  to allow ice crystals to be supplied into the tank. Air is generally continuously circulated through the tank  470  by the air blower  474  which draws air from the top of the tank  470  via the intake port  472  and returns it to the air injection manifold  478  via the exhaust port  476 . The velocity of the air flowing through the tank  470  is selected to be sufficient to maintain the ice crystals in suspension, counterbalancing gravity&#39;s effect on the ice crystals, thus creating a fluidized bed  482  of the ice crystals within the tank  470 . 
     During operation, foodstuff  484  is placed in the tank  470  such that the foodstuff is immersed in the fluidized bed  482 . Contact between the foodstuff  484  and the ice crystals of the fluidized bed  482  causes the ice crystals to melt resulting in the efficient removal of heat from the foodstuff  484 . Melted water is drained from the bottom of the tank  470  via outlet  486  and new ice crystals are generally continuously added to the tank  470  via inlet port  480  to maintain the fluidized bed  482 . 
     If desired, both air and ice crystals may be re-circulated through the air blower  474 . In this case, the blower may be used to break ice crystal conglomerations thus ensuring that the fluidized bed  482  consists of homogeneous ice crystals. For example, the air blower  474  construction may be similar to that of a snow blower machine, which breaks, homogenizes, and discharges the ice crystals. 
       FIG. 7  shows yet another apparatus  620  for cooling foodstuff. As can be seen, in this embodiment the apparatus  620  comprises a tank  640  filled with an ice slurry bath  642 . Agitators  644  comprising paddles  644   a  mounted on rotating shafts  644   b  are positioned adjacent the bottom of the tank  640  at spaced locations. Nozzle assemblies  650  are provided adjacent at least two sides of the tank. Each nozzle assembly  650  has a series of nozzles  650   a  pointing inwardly towards the center of the tank  640 . Most, if not all of the nozzles  650   a  are positioned above the ice slurry bath  642 . A pump  676  has its inlet coupled to a drain at the bottom of the tank  640  and its outlet coupled to the nozzle assemblies  650 . In this manner, ice slurry in the tank  640  can be drawn from the bottom of the tank and discharged back into the top of the tank via the nozzles  650   a.    
     During operation, foodstuff  680  is suspended in the tank  640  above the ice slurry bath  642  and the pump  676  is operated so that the nozzle assemblies  650  spray the foodstuff with ice slurry. As a result, ice slurry is passed over the outer surfaces of the foodstuff  680 , with excess ice slurry falling back into the ice slurry bath. Ice crystals coming into contact with the foodstuff  680  melt thereby absorbing heat resulting in the foodstuff  680  being cooled. The presence of the ice crystals in the spray significantly improves the heat transfer in comparison to chilled water or brine. 
     If desired, a conveyor system can be used to deliver foodstuff  680  into the tank  640  between the nozzle assemblies  650 . Also, rather than using nozzle assemblies  650  to spray ice slurry onto the foodstuff  680 , the pump  676  can supply an outlet port adjacent the top of the tank  640  which is configured to pour a stream of ice slurry onto the foodstuff  680 . 
     Referring to  FIG. 8 , still yet another embodiment of an apparatus  820  for cooling foodstuff is shown. As can be seen, in this embodiment the apparatus  820  comprises a tumbler  840  in the form of an inclined, perforated drum having an inlet  842  at one end that receives a mixture of foodstuff and ice crystals. A foodstuff outlet  844  is provided at the opposite end of the tumbler  840 . A motor (not shown) is coupled to the tumbler  840  via a gear box  846  to rotate the tumbler  840 . A formation such as a spiral or pedals  848  is provided on the interior surface of the tumbler  840  so that when the tumbler is rotated, foodstuff within the tumbler advances along the tumbler from the inlet  842  to the outlet  844 . 
     Contact between the foodstuff and ice crystals within the tumbler  840  causes the ice crystals to melt resulting in the absorption of heat and cooling of the foodstuff. Water resulting from the melted ice crystals is continuously drained from the tumbler via the perforations therein while new ice crystals are added. The rotating and tumbling motion ensures close contact between the foodstuff and the ice crystals. Additional devices to prevent clumping of the ice crystals thereby to improve contact between the ice crystals and the foodstuff may be provided in the tumbler. Also, if desired separate inlets may be provided in the tumbler for the foodstuff and ice crystals. 
     Although embodiments have been described above with reference to the Figures, those of skill in the art will appreciate that variations and modifications may be made without departing from the spirit and scope thereof as defined by the appended claims.