METHOD AND DEVICE FOR HOMOGENEOUS FREEZING

Abstract

A method and device for freezing food items in a controlled and homogeneous manner. The method and device use plate freezers to bring the food items in a regulated manner through the whole freezing process.

Claims

1-23. (canceled)

24. A system for freezing food items, said system comprising: providing freezer apparatus further comprising an isolated chamber (1), a plurality of plates (2) arranged in the chamber (1) with spacing (3) between the plates (2), where each plate (2) further comprises: i) a hollow space (5) within the plate for cooling medium to flow through, ii) an inlet (6) and an outlet (7) for the cooling medium to enter and exit the plate (2), iii) an inlet valve (8) and an outlet valve (9) to control the flow of the cooling medium through each plate (2), means for loading the food items (4) to be frozen into the freezer between each two plates (2), providing a flow of cooling medium into each plate at a pre-determined temperature, and a control means for regulating the flow of cooling medium through the freezer apparatus, characterized in that the apparatus further comprises a sensor (12) near the outlet for each plate to monitor the temperature of the cooling medium as it exits the plate (2), and the control means regulates the flow of cooling medium to and from each plate individually, where the flow of cooling medium to each plate is determined by the temperature of the cooling medium leaving each plate throughout the freezing process.

25. The system according to claim 24, wherein a pre-defined temperature limit is set for the cooling medium leaving each plate throughout the freezing process and wherein the control means regulates the flow of cooling medium to each plate to keep the temperature of the cooling medium below said pre-defined temperature limit.

26. The system according to claim 25, wherein the pre-defined temperature limit set for the cooling medium leaving each plate throughout the freezing process is gradually decreased until the food items in the freezer are frozen.

27. The system according to claim 25, wherein the pre-defined temperature limit set for the cooling medium leaving each plate throughout the freezing process is based on keeping the temperature of the cooling medium leaving each plate near the phase transition of the cooling medium from liquid phase to gas phase.

28. The system according to claim 27, wherein the pre-defined temperature limit is set at a value where the cooling medium leaving each plate throughout the freezing process is in gas phase.

29. The system according to claim 24, wherein the hollow space (5) is in the form of flow channels within the freezing plates and allow the cooling medium to flow from one side of the plate to the other.

30. The system according to claim 24, wherein the cooling medium is NH3.

31. The system according to claim 24, wherein the control means regulates the flow of cooling medium to and from each freezing plate according to a predefined scheme based on the food items to be frozen.

32. An apparatus for freezing food items, said apparatus comprising: an isolated chamber (1), a plurality of plates (2) arranged in the chamber (1) with spacing (3) between the plates (2) for food items (4) to be loaded into the freezer apparatus between the plates (2), wherein each plate (2) further comprises: i) a hollow space (5) within the plate for cooling medium to flow through, and ii) an inlet (6) and an outlet (7) for the cooling medium to enter and exit the plate (2), an inlet valve (8) and an outlet valve (9) to control the flow of the cooling medium to each plate (2), a control computer for controlling the flow of cooling medium into each plate, characterized in that the apparatus further comprises a sensor (12) near the outlet for each plate to monitor the temperature of the cooling medium as it exits the plate (2), and in that the flow of cooling medium to each plate is determined by the temperature of the cooling medium leaving each plate throughout the cooling/freezing process and wherein the control computer regulates the flow of cooling medium to and from each plate individually.

33. The apparatus according to claim 32, further comprising in-feed piping (10) and outlet piping (11) to transfer the cooling medium to and from each cooling plate.

34. The apparatus according to claim 33, wherein the sensor (12) is positioned in the outlet piping (11) for each plate.

35. The apparatus according to claim 32, wherein the freezer plates are horizontally arranged within the freezing chamber.

36. The apparatus according to claim 32, wherein the hollow space (5) within the plate is formed as a flow channel for the cooling medium to flow through from the inlet to the outlet.

37. The apparatus according to claim 32, wherein the isolated chamber is a freezer chamber arranged to house plates with channels for heat exchange medium to flow through said plates.

38. A method for freezing food items, said method comprising the steps of: a) loading food items onto a plate of the freezer apparatus of claim 32, b) starting a flow of cooling medium into the plate with food items at a pre-determined temperature, c) determining the temperature of the cooling medium after it has flowed through the plate, d) repeating steps a) through c) for each plate in the freezer, characterized in that the control computer regulates the flow of cooling medium to and from each plate individually, and wherein the flow of cooling medium to each plate is determined by the temperature of the cooling medium leaving each plate throughout the cooling/freezing process.

39. The method according to claim 38, wherein the computer regulates the flow of cooling medium to maintain a predetermined ΔT between the food items and the cooling medium in each plate throughout the cooling/freezing process.

40. The method according to claim 39, wherein the ΔT between the food items and the cooling medium in each plate differs for different stages of the cooling/freezing process.

41. The method according to claim 39, wherein the control computer regulates the ΔT between the food items and the cooling medium in each plate such that the temperature of the cooling medium in each plate is gradually cooled down at a first predefined rate to the phase transition of the food items, then at a second predefined rate through the phase transition of the food items and then at a second predefined rate after the phase transition of the food items.

42. The method according to claim 38, wherein the plates are horizontally arranged in the freezer apparatus and wherein the freezer apparatus is loaded from top to bottom or vice versa and wherein the plate above the food items contributes to the cooling of the food items as is following an adjacent scheme of cooling/freezing.

43. The method according to claim 38, wherein the control computer regulates the flow of cooling medium through each plate such that the items on each plate are gradually cooled down towards the phase transition of the food items and then taken slowly through the phase transition of the food items to provide a homogeneous cooling and freezing process for the whole product through the freezing process.

44. The method according to claim 38, wherein the food items are packed in boxes with or without being individually packed within the boxes.

45. A method for thawing frozen food items, said method comprising the steps of: a) loading food items onto a plate in the chamber of the apparatus of claim 24, b) starting a flow of heat exchange medium into the plate with food items at a pre-determined temperature, c) determining the temperature of the heat exchange medium after it has flowed through the plate, d) repeating steps a) through c) for each plate in the chamber, characterized in that the computer regulates the flow of heat exchange medium to each plate individually and wherein the flow of heat exchange medium is determined by the temperature of the heat exchange medium leaving each plate throughout the thawing process.

46. The method according to claim 45, wherein the control computer regulates the flow of the heat exchange medium through each plate such that the items on each plate are gradually heated up towards the phase transition of the food items and then taken slowly through the phase transition of the food items to provide a homogeneous thawing process for the whole product.

Description

DESCRIPTION OF VARIOUS EMBODIMENTS

[0058] The present invention will become more fully understood from the detailed description given hereinafter and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

[0059] FIG. 1 is a cross section of a horizontal plate freezer.

[0060] FIG. 2 is a top view of a horizontal plate freezer.

[0061] FIG. 3 is a top view of a plate in the apparatus of the present invention.

[0062] FIG. 4 is a perspective view of a stack of plates for the apparatus of the present invention.

[0063] FIG. 1 shows a cross section of an automatic plate freezer, and FIG. 2 shows a projection (or top view) of the same freezer chamber 1. FIG. 1 shows food items 4 packed in boxes hi rows on each plate 2 in the freezer. The food items enter the freezer in boxes by a conveyor belt, and an in-feeding device 13 places the boxes onto the freezer plates. The freezer shown in FIGS. 1 and 2 comprises 24 freezing plates, but the number and size of places for each freezer depends on the performance required and the size of the boxes desired. The size of the gap/space 3 between the freezer plates can be varied based on the size of the packings containing the food items to be packed. This will result in that the food products will not be harmed or crushed, and careful handling is ensured. The in-feeding device 13 is kept at a constant height whereas the freezer plates on which the boxes are being placed are adjusted to the height of the in-feeding device 13. In this embodiment, the in-feeding starts for the top plate and then the next one below and then one by one until the freezer is filled with boxes for freezing. The outlet belt 14 is shown on the other side of the chamber,

[0064] FIG. 3 is a top view of a single plate in an apparatus of the invention. The plate has an inlet 6 and an outlet 7 for the heat transfer medium to enter and exit the plate 2 and the dotted lines indicate flow channels within the plate for facilitating flow of heat exchange medium through the plate. The inlet 6 is connected to an inlet valve 8 through an in-feed piping 10 and the outlet is connected to an outlet 9 through an outlet piping 11. The valves 8, 9 control the flow of the heat transfer medium through the plate 2 through the in-feed piping 10 and outlet piping 11. The flow of cooling medium into each plate is controlled by a control computer (not shown). A sensor 12 is provided for each plate in the outlet piping 11 near the outlet valve 9 to monitor the temperature of the heat transfer medium as it exits the outlet piping 11.

[0065] FIG. 4 shows a rack of plates 2 for an apparatus of the present invention. The figure shows how each plate has its own in-feed piping 10 and outlet piping 11, as well as a sensor 12 in each of the outlet piping 11. The sensor is then connected to the control computer so that the control computer can regulate the flow of the heat transfer medium to each plate based on the temperature of the heat transfer medium leaving each plate at any time individually.

[0066] As used herein, including in the claims, singular forms of terms are to be construed as also including the plural form and vice versa, unless the context indicates otherwise. Thus, it should be noted that as used herein, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.

[0067] Throughout the description and claims, the terms “comprise”, “including”, “having”, and “contain” and their variations should be understood as meaning “including but not limited to”, and are not intended to exclude other components.

[0068] The present invention also covers the exact terms, features, values and ranges etc. in case these terms, features, values and ranges etc. are used in conjunction with terms such as about, around, generally, substantially, essentially, at least etc. (i.e., “about 3” shall also cover exactly 3 or “substantially constant” shall also cover exactly constant).

[0069] The term “at least one” should be understood as meaning “one or more”, and therefore includes both embodiments that include one or multiple components. Furthermore, dependent claims that refer to independent claims that describe features with “at least one” have the same meaning, both when the feature is referred to as “the” and “the at least one”.

[0070] It will be appreciated that variations to the foregoing embodiments of the invention can be made while still falling within the scope of the invention. Features disclosed in the specification, unless stated otherwise, can be replaced by alternative features serving the same, equivalent or similar purpose. Thus, unless stated otherwise, each feature disclosed represents one example of a generic series of equivalent or similar features.

[0071] Use of exemplary language, such as “for instance”, “such as”, “for example” and the like, is merely intended to better illustrate the invention and does not indicate a limitation on the scope of the invention unless so claimed. Any steps described in the specification may be performed in any order or simultaneously, unless the context clearly indicates otherwise.

[0072] All of the features and/or steps disclosed in the specification can be combined in any combination, except for combinations where at least some of the features and/or steps are mutually exclusive. In particular, preferred features of the invention are applicable to all aspects of the invention and may be used in any combination.