Method for freezing food items

Abstract

Method and device for freezing food items in a gradual process, where the food items are first put through under-cooling before the food items are placed in a container or receptacle for freezing. The method and device are particularly suitable for freezing freshly slaughtered and bled fish for later processing.

Claims

1. A method for freezing food items, said method comprising: a) receiving food items, b) bringing the food items to an under-cooled state in salt-controlled and temperature-controlled liquid in at least one first container by: i) determining the salt concentration of the liquid and maintaining the temperature of the liquid such that the temperature is higher than the freezing point of the liquid, and ii) providing substantially continuous movement of the food items in the liquid during the step of bringing the food items to an under-cooled state, c) subjecting the food items to a temperature balancing step to allow the food items to rime before freezing the food items, d) transferring the food items to a receptacle for freezing, and e) bringing the food items to a temperature between ?4 and ?24? C. for storage before processing, wherein step c) is performed after bringing the food items to an under-cooled state and prior to freezing the food items.

2. The method of claim 1, wherein the food items are undercooled in step b) until the food items have reached a homogenous temperature within a range from about ?3? C. to about ?0.1? C.

3. The method according to claim 1, wherein the step b) is performed in a salt-controlled and temperature-controlled solution in at least two steps comprising: i) placing the food items in first salt-controlled and temperature controlled liquid having a salt concentration in the range from 0.1 to 10% and a temperature in the range from +1 to ?3? C., where the salt concentration and set temperatures of the salt-controlled and temperature controlled liquid brings the homogenous temperature of the food items to +2 to ?1? C., and ii) transferring the food items to a second salt-controlled and temperature controlled liquid having a salt concentration in the range from 1 to 20% and a temperature in the range from ?1 to ?12? C., where the salt concentration and set temperatures of the salt-controlled and temperature controlled liquid brings the homogenous temperature of the food items to ?0.1 to ?3? C.

4. The method of claim 1, wherein the food item is selected from fish, chicken, beef, pork and lamb meat products.

5. The method of claim 4, wherein the food item is fish comprising salmon, trout, cod, haddock, pollock, catfish, ling, blue ling, tusk, monkfish, carp, bass, bream, turbot, sea bass, sole, milkfish, grey mullet, grouper, sea bream, halibut, flounder, or Japanese flounder.

6. The method according to claim 5, wherein the fish is gutted and/or bled prior to step b) wherein the fish is bled in a tank or spiral pump.

7. The method according to claim 5, wherein the fish is placed in final packings after the temperature balance step and before freezing.

Description

DESCRIPTION OF VARIOUS EMBODIMENTS

(1) 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:

(2) FIG. 1 is a front view of the apparatus of the present invention

(3) FIG. 2 is perspective drawing of an apparatus according to one embodiment of the present invention.

(4) FIG. 1 shows a schematic drawing of an apparatus of the present invention where the devices for performing the sub-chilling step are either (a) two parallel connected spiral pumps 1 or (b) a spiral pump 1 followed by a tank 2 with a spiral blade 3 to advance slaughtered animals or food items along the tank during treatment. In the embodiment shown in solution (b), the spiral pump 1 can be used for facilitating bleeding of freshly slaughtered fish and the two sub-chilling steps can be performed in the cooling tank 2 with a the rotating spiral blade 3. Such a cooling tank is provided with heat exchange elements 4 and sensors (not shown) to provide a constant temperature and salt concentration during the process. The spiral pumps 1 have a helical wound tubing 5 around a frame 6 for transporting and treating slaughtered animals or food items in liquid. After the sub-chilling step the items are delivered to a device for temperature balancing 7, such as a conveyor belt in this case. The devices for performing the sub-chilling steps of the present invention are designed for treating the food items, such as fish, in a salt controlled and temperature controlled solution providing agitation or movement of the food items during the cooling process. The temperature balancing device is provided to allow the food items to rime or temperature balance before they are frozen. This will allow the temperature at the surface of the food items to penetrate the food items. The food items are then placed in packings for freezing after temperature balancing, which leaves the food items fully expanded before freezing. In this embodiment the freezer 8 is a plate freezer with automatic in-feeding for trays. By further providing trays 9 or lateral packing units, the food items will not be pressure damaged during freezing.

(5) FIG. 2 shows the steps of the method of the present invention up to the temperature balancing and the devices used to perform the method steps in an embodiment of slaughtering fish such as salmon. The steps of temperature balancing, placing the fish in boxes or trays and freezing are not shown. The fish is pumped or transported to a stunner 10 where the fish is stunned at 5? C. After stunning the fish is transported through piping into a first spiral pump 1a to facilitate bleeding of the fish in higher temperatures for a short time, such as up to 40-50? C. The spiral pump 1a receives warm liquid from a heat exchanger 4a and the warm water facilitates the bleeding steps as does the flow if the liquid against the fish in the rotating spiral tubing. When the fish and the liquid in each winding of the spiral pump is pumped out of the spiral pump 1a, the content is pumped through piping 13a to a separation device 11a where the liquid is separated from the fish and the fish enters the second spiral pump 1b, whereas the liquid is filtered in a collection tank 12a for blood and warm liquid for filtering and circulation back through a heat exchanger 4a and back into the spiral pump for continued bleeding. The fish entering the second spiral pump 1b are subjected to a short period of cool down as the first step of the sub-chilling method in 5? C. brine, where the cold brine facilitates rapid cooling of the fish together with the flow if the liquid against the fish in the rotating spiral tubing. When the fish and the liquid in each winding of the spiral pump 1b is pumped out of the spiral pump 1a b, the content is pumped through piping 13b to separation device 11b where the liquid is separated from the fish and the fish enters the cooling tank 2 with a spiral shaped blade 3, whereas the liquid is filtered in a collection tank 11b for brine for filtering and circulation back through a heat exchanger 4b and back into the spiral pump 1b for continued sub-chilling of fish. The second sub-chilling step is performed in the cooling tank 2 before the fish is transferred to means for allowing the fish to rime in a temperature balancing step followed by freezing (not shown).

(6) 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.

(7) 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.

(8) 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).

(9) 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.

(10) 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 can be made while still falling within 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.

(11) 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.

(12) 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.