Tunnel freezer and method for freezing layers of food products

Abstract

The present application relates to a tunnel freezer configured to freeze food products arranged in layers. The tunnel refrigerator includes a housing and a conveyor unit. The housing includes a plurality of housing sections. The conveyor unit is configured to convey a layer of food product through each of the plurality of shell sections. Each housing section comprises a fan for providing a flow of a gaseous medium, and a cooling unit arranged to cool the gaseous medium in the flow. A first housing section of the plurality of housing sections is configured to force a flow of a gaseous medium through the food layer in a first direction. A second housing section of the plurality of housing sections is configured to force the flow of the gaseous medium through the food product layer in a second direction different from the first direction. The present application also relates to a method for freezing food products arranged in layers and to a method for operating a tunnel freezer.

Description

[0001] The present application relates to a tunnel freezer configured to freeze foodstuffs arranged in layers and a method for operating such a tunnel freezer. The present application also relates to a method for freezing foodstuffs arranged in layers.

[0002] Tunnel freezers are known in the art and include: a housing including a plurality of housing segments; and a conveyor unit configured to convey a layer of foodstuffs through each of the plurality of housing segments. Each housing segment includes a blower for providing a flow of a gaseous medium and a cooling unit arranged to cool the gaseous medium in the flow.

[0003] Typical examples of foodstuffs frozen using such tunnel freezers are French fries, vegetables, fruits, (diced) meat or (shellfish) fish. However, a tunnel freezer can be used to freeze any foodstuff that can be spread out on the conveyor unit to form a layer. For the sake of convenience, the present application will explain the invention with respect to French fries, but this is merely an example and is not intended to limit the present application in any way.

[0004] For French fries to be considered frozen, all or at least most of the water present in the French fries needs to change state from liquid water to solid ice. Water freezes at different temperatures depending on the medium containing the water. The applicant has found that for French fries (or more specifically, the water in French fries), the freezing point is approximately -14 degrees Celsius. When the French fries freeze, the aforementioned phase change (from liquid water to solid ice) occurs and latent heat (also known as potential energy) is released, thereby increasing the temperature of the French fries. The applicant has found that the latent heat released during the freezing of French fries can cause the temperature of the French fries to jump by approximately 5 degrees Celsius. If the French fries are frozen at -14 degrees, this means that the resulting frozen French fries will have a temperature of approximately -9 degrees Celsius. The frozen French fries can then be further cooled to a final desired temperature, such as approximately -10 or approximately -12 degrees Celsius.

[0005] However, those skilled in the art will understand that at the aforementioned freezing point, water does not necessarily always freeze immediately. In the absence of ice nuclei (also known as seed crystals), liquid water can supercool, thereby reaching a temperature below the freezing point without undergoing a phase change. The applicant has found that French fries (or more specifically, the water in French fries) can supercool to approximately -14 degrees Celsius. After the French fries enter this supercooled state, the French fries can still freeze and release latent heat at any point in time, as described above.

[0006] Figure 5The measurement results confirming this process are shown in the graph. The graph shows a part of the temperature change of each of the fries S2 - S4 as they pass through the tunnel freezer. The X - axis represents time. Since each of the fries S2 - S4 is conveyed through the tunnel freezer at a relatively constant speed, the passage of time shown on the X - axis can be directly related to the distance that the fries S2 - S4 travel through the tunnel freezer. The Y - axis represents temperature in degrees Celsius. For each of the fries S2 - S4, a sudden increase or jump in the measured temperature is observed. This increase in temperature corresponds to the release of latent heat and can thus be considered an indication that the desired phase change has occurred.

[0007] In tunnel freezers known in the prior art, the following situation occurs: A batch of fries is measured to have a desired average temperature, for example, between - 10 and - 12 degrees Celsius, preferably about - 11 degrees Celsius, while most of the fries in the batch are not actually frozen but are in this supercooled state. Thus, some of the fries in this batch are wrongly considered to be frozen when storing the batch of fries.

[0008] However, these supercooled fries will eventually freeze. When this happens, the above - mentioned latent heat is released, and the average temperature of the stored batch of fries increases. The applicant has found that this effect is very significant, resulting in an increase in the final average temperature of a stored batch of fries of up to 5 degrees Celsius. A stored batch of fries frozen by a tunnel freezer known in the art can have a final average temperature in the range of about - 20 to about - 15 degrees Celsius. This delayed release of latent heat and the resulting temperature increase are considered to be very problematic.

[0009] For fries, as with all foods, there is a threshold temperature below which the fries can be stored to ensure the quality of the fries and / or avoid spoilage of the fries. If the fries are cooled to just around this threshold temperature, the above - mentioned delayed release of latent heat may cause the "final" temperature of a batch of fries to be higher than the threshold, thus putting the batch at risk of spoilage.

[0010] Another problem that occurs when fries are stored at a temperature that is not low enough is that ice crystals will start to grow on the fries. These ice crystals may give the fries a white sheen, which is an undesirable aesthetic. The ice crystals may also cause the fries to freeze together, thus forming clumps of fries in the stored fries.

[0011] An anticipated temperature increase due to the delayed release of latent heat can be expected by cooling the French fries to a temperature around the threshold temperature minus the anticipated temperature increase. However, this is also not ideal as it requires additional cooling capacity in the tunnel freezer as well as in the storage facility. These in turn require additional investment and generally use more electricity. A person skilled in the art will appreciate this motivation to cool and store the French fries at the highest possible temperature.

[0012] A person skilled in the art will understand that the temperatures and temperature ranges mentioned in the introduction with respect to French fries may be different for other foods.

[0013] The present application provides a tunnel freezer configured to freeze food arranged in layers, a method for operating the tunnel freezer, and a method for freezing a layer of food, which at least partially alleviates some of the above-mentioned disadvantages.

[0014] The present application also provides a tunnel freezer, a method for operating the tunnel freezer, and a method for freezing food. Compared with food processed by a tunnel freezer or method known in the prior art, the tunnel freezer and method provided by the present application are capable of freezing food such that a smaller portion of the food is in a supercooled state and / or a larger portion of the food undergoes a phase change from liquid water to solid ice.

[0015] The present application also provides a tunnel freezer, a method for operating the tunnel freezer, and a method for freezing food, wherein the distribution of the final average temperature of a batch of food frozen using the tunnel freezer or any of the methods has a smaller variance compared to the distribution of the final average temperature of a batch of food frozen using a tunnel freezer or method known in the prior art.

[0016] At least some of the above-mentioned objectives are at least partially solved in the tunnel freezer according to claim 1, which is configured to freeze food arranged in layers. The tunnel freezer includes a housing and a conveyor unit. The housing includes a plurality of housing segments. The conveyor unit is configured to convey a layer of food through each of the plurality of housing segments. Each housing segment includes a ventilator for providing a flow of gaseous medium and a cooling unit arranged to cool the gaseous medium in the flow. The first housing segment of the plurality of housing segments is configured to force the flow of gaseous medium to flow through the food layer in a first direction. The second housing segment of the plurality of housing segments is configured to force the flow of gaseous medium to flow through the food layer in a second direction different from the first direction.

[0017] When most of the food is in an acceptable state, it is advantageous to trigger the freezing of the aforementioned food and / or the corresponding temperature jump. In a preferred embodiment, the conveyor unit is configured to convey a layer of food from the first section to the second section when the percentage of the food in a supercooled state is within a predetermined range, which is preferably from 20% to 80%, more preferably from 30% to 70%, and even more preferably from 40% to 60%.

[0018] The applicant has found that the effects of the present invention are maximized when the first direction and the second direction are opposite to each other. In existing tunnel freezers, the first direction is usually from bottom to top, and in this case, the most advantageous second direction is from top to bottom.

[0019] In some embodiments that are implementable and thus advantageous, the housing is elongated, and a plurality of housing sections are longitudinally distributed on the elongated housing.

[0020] Preferably, the gaseous medium is air.

[0021] At the same time, the greater the difference between the first direction and the second direction, the greater the likelihood of their collision. To limit this situation, in some embodiments, the first housing section and the second housing section are substantially isolated from each other such that the flow of the gaseous medium flowing through these respective housing sections is substantially contained within the respective housing sections.

[0022] In some embodiments, the plurality of housing sections further includes a third housing section configured to force the flow of the gaseous medium to flow through the food layer in the first direction, and the conveyor unit is configured to sequentially convey the food through the first housing section, the second housing section, and the third housing section. Such a configuration results in two changes in direction, thereby achieving favorable technical effects twice.

[0023] In a preferred embodiment, the amount of time the food is conveyed through the first housing section is approximately twice the amount of time the food is conveyed through the second housing section and / or the third housing section, and / or wherein the amount of time the food is conveyed through the second housing section and the third housing section is approximately equal. In a preferred embodiment, the conveyor unit is configured to convey the food through the first housing section, the second housing section, and the third housing section at a substantially constant speed.

[0024] To achieve a continuous process of freezing each food item, the conveyor unit can be a belt conveyor that includes a conveyor belt on which the food can be spread out to form a layer. The conveyor belt is preferably provided with a plurality of holes to allow the flow of the gaseous medium to flow through the conveyor belt.

[0025] In a housing section configured to force a gas medium to flow through the layers of food from top to bottom, the belt can be suspended loosely in order to avoid the flow of the gaseous medium pressing the layers together. This slack causes the layer to rearrange itself during conveyance, thereby creating new places through which air can pass.

[0026] In some embodiments, the first housing section is configured to force a flow of the gaseous medium through the conveyor unit from bottom to top, and / or the second housing section is configured to force a flow of the gaseous medium through the conveyor unit from top to bottom.

[0027] The gas flow can be provided in several ways. In some embodiments, each housing section is divided into a first partition and a second partition, where the second partition is defined from the first partition by the conveyor unit and by a separating device including an opening, and a ventilator is arranged in the opening. The conveyor unit is permeable to the gaseous medium, and the separating device can be made of a material impermeable to the gaseous medium.

[0028] Specifically, in some embodiments, at least a part of the first partition is adjacent to the underside of the conveyor unit, and / or at least a part of the second partition is adjacent to the upper side of the conveyor unit.

[0029] In some embodiments, by arranging a ventilator in the first housing section to draw the gaseous medium from the second partition and push it into the first partition and / or to increase the pressure in the first partition relative to the second partition, the gaseous medium is forced to pass from the first partition through the conveyor unit and, when a food layer is arranged on the conveyor unit, through the food layer into the second partition, thereby providing a flow of the gaseous medium.

[0030] Similarly, in some embodiments, by arranging a ventilator in the second housing section to draw the gaseous medium from the first partition and push it into the second partition and / or to reduce the pressure in the first partition relative to the second partition, the gaseous medium is forced to pass from the second partition through the conveyor unit and, when a food layer is arranged on the conveyor unit, through the food layer into the first partition.

[0031] In some embodiments, the first housing section and the second housing section are adjacent to each other.

[0032] In some embodiments, a housing wall is disposed between the first housing section and the second housing section, the housing wall including a slot through which a conveyor unit extends. For those embodiments, the conveyor unit may include a first side and an opposite second side of the layer on which food is to be transported. In such embodiments, the tunnel freezer may further include slats that are hingedly attached to a first edge of the slot opposite the first side of the conveyor unit, and / or the slats are configured to at least partially contain a flow of gaseous material in the housing sections on both sides of the housing wall.

[0033] Specifically, the gap between the second side of the conveyor unit and the second edge of the slot opposite the second side is preferably small enough to allow a pressure difference to exist between a first partition of the first housing section and a first partition of the second housing section.

[0034] The slot may at least partially extend into a portion of the housing wall disposed between a second partition of the first housing section and a second partition of the second housing section, and / or the slot may not extend into a portion of the housing wall disposed between a first partition of the first housing section and a first partition of the second housing section.

[0035] Similarly, the plurality of housing sections may include an end housing section that is a front housing section or a rear housing section, and a portion of the housing that defines the end housing section includes an opening through which the conveyor unit extends. The opening may at least partially extend into a portion of the housing that defines a second partition of the end housing section, and / or may not extend into a portion of the housing that defines a first partition of the end housing section.

[0036] To further limit air leakage from the housing section to the outside, the pressure in the first partition of each housing section in the housing section may be substantially equal to the ambient pressure and / or substantially equal to the standard atmospheric pressure.

[0037] Some of the foods that benefit from the present invention are French fries, green beans, carrots, or any other type of elongated food.

[0038] Those skilled in the art will understand that the temperatures used will vary depending on the actual freezer being discussed. In some embodiments, in the first housing section and the second housing section, the gaseous medium flowing through the layer of food is between about -18 and about -36 degrees Celsius, preferably about -24 degrees Celsius. In some embodiments, the plurality of housing sections further includes a pre-cooling section in which the gaseous medium flowing through the layer of food is between about 28 and about -1 degree Celsius, wherein the conveyor unit is preferably configured to first convey the food into the pre-cooling section.

[0039] According to another aspect of the present invention, there is provided a method for freezing food arranged in layers, which method preferably uses a tunnel freezer according to any one of the preceding claims. The method comprises:

[0040] - conveying the layers of food through each of a plurality of housing sections included in the housing using a conveyor unit,

[0041] - in each housing section, providing a flow of gaseous medium and cooling the gaseous medium in the flow,

[0042] - in a first housing section of the plurality of housing sections, forcing the flow of gaseous medium to flow through the food layer in a first direction,

[0043] - in a second housing section of the plurality of housing sections, forcing the flow of gaseous medium to flow through the food layer in a second direction different from the first direction.

[0044] According to another aspect of the present invention, there is provided a method for operating a tunnel freezer for freezing food. Such a tunnel freezer comprises a housing and a conveyor unit. The housing comprises a plurality of housing sections. The conveyor unit is configured to convey layers of food through each of the plurality of housing sections. Each housing section comprises a ventilator for providing a flow of gaseous medium and a cooling unit arranged to cool the gaseous medium in the flow. A first housing section of the plurality of housing sections is configured to force the flow of gaseous medium to flow through the food layer in a first direction. A second housing section of the plurality of housing sections is configured to force the flow of gaseous medium to flow through the food layer in a second direction different from the first direction. The method comprises the following steps:

[0045] - determining, for the food, the supercooling temperature range in which the water in the food is supercooled;

[0046] - cooling the food layer in the first housing section until the average temperature of the food is within the supercooling temperature range, and,

[0047] - when the average temperature of the food is within the supercooling temperature range, conveying the layer of food into the second housing section.

[0048] Preferably, the method is implemented in an embodiment of a tunnel freezer as previously described in the present application.

[0049] Next, the present invention will be described with reference to the accompanying drawings, in which like or similar parts are denoted by the same reference numerals, and in which:

[0050] Figure 1 shows a cross-section of a tunnel freezer according to the present invention;

[0051] Figures 2A to 2B shows Figure 1Isometric view of the freezing section of a tunnel freezer;

[0052] Figures 3A to 3B Shows a cross-section of a conventional freezing section;

[0053] Figures 4A to 4B Shows a cross-section of the freezing section in which the air flow is reversed; and

[0054] Figure 5 Shows the variation of the temperature of some individual parts over time during the freezing process.

[0055] Reference Figure 1 , shows a cross-section of the tunnel freezer 1. The tunnel freezer 1 includes an elongated housing 2, a belt conveyor 3, a plurality of cooling elements 4, and a plurality of ventilators 5. The elongated housing 2 is divided into housing sections 2A, 2B, 2C, 2D, and 2E. The tunnel freezer 1 may further include a controller 100 that is functionally connected to at least the belt conveyor 3, the plurality of cooling elements 4, and the plurality of ventilators 5.

[0056] The elongated housing 2 is divided into a pre-cooling section 2A, a water-cooling section 2B, and three freezing sections 2C, 2D, and 2E. Each section includes a number of cooling elements 4 and a number of ventilators 5, which are respectively composed of corresponding plural cooling elements and plural ventilators. Those skilled in the art will understand that the housing sections may be provided with any number of cooling elements and / or ventilators.

[0057] In the tunnel freezer 1, the pre-cooling section 2A and the water-cooling section 2B may be provided with cooling elements 4 that rely on water as a coolant. The freezing sections 2C, 2D, and 2E may be provided with cooling elements that rely on ammonia as a coolant. However, those skilled in the art will understand that it is also possible to use other heat transfer liquids, and other cooling elements can generally also be used.

[0058] Food can be arranged in layers on the belt conveyor 3 and conveyed through the elongated housing 2 in this form. Considering the tunnel freezer 1 from Figure 1 's perspective, the food is conveyed from left to right, thus passing through each housing section. Those skilled in the art will realize that the belt conveyor 3 is only one embodiment of the conveyor unit, and other conveyor units, such as roller conveyors, tray conveyors, etc., can also be used.

[0059] To cool and ultimately freeze the food, the tunnel freezer 1 is configured to force a cold air flow through the food layer. The ventilator 5 is configured to provide an air flow, and the cooling unit 4 is used to cool the air in the air flow. Embodiments relying on gaseous media other than air can be envisioned. The tunnel freezer can specifically be an "individual quick freezing" or IQF tunnel.

[0060] In the context of the present application, the term "ventilator" (used to describe elements 5, 5A and / or 5B) is to be understood as covering conventional ventilators, but the term should not be understood as being limited thereto. It thus also covers devices provided with turbine impellers or other turbine-like embodiments which are also suitable for providing the required air flow.

[0061] In the precooling sections 2A and 2B, the air flowing through the layer of food is between approximately 28 degrees Celsius and approximately -1 degree Celsius. In each of the freezing sections 2C, 2D, 2E, the air flowing through the layer of food is between approximately -18 and approximately -36 degrees Celsius, preferably approximately -24 degrees Celsius.

[0062] The precooling sections 2A, the water cooling section 2B and the freezing sections 2C and 2E are each configured to force the air flow from bottom to top (represented as the first direction d1 in Figure 1 through the food layer. The freezing section 2D is configured to force the fluid from top to bottom (represented as the second direction d2 in Figure 1 through the food layer.

[0063] The applicant has found that freezing the layer by forcing the air to flow through the food layer in only a single direction results in an unevenly frozen layer. For example, in the tunnel freezer 1, this occurs if the food layer is only conveyed through sections 2A, 2B and 2C.

[0064] In the context of the present application, uneven freezing is to be understood as: (a) in the food, at the first side of the layer, the desired phase change from liquid water to solid ice occurs more frequently than at the second opposite side of the layer, and / or (b) the food at the second opposite side of the layer is in a supercooled state more frequently than the food at the first side of the layer. Uneven freezing should not be understood as meaning that the food at the first side of the layer is necessarily colder than the food at the second opposite side.

[0065] The applicant has found that changing the direction in which the air is forced through the layer triggers the desired phase change from liquid water to solid ice in many, if not all, of the food in a supercooled state. For example, in the tunnel freezer 1, this occurs when the food layer is conveyed from the freezing section 2C into the freezing section 2D, and occurs again when the food layer is conveyed from the freezing section 2D into the freezing section 2E. These changes in direction at least slightly alleviate the above problems and help to provide a more evenly frozen layer.

[0066] Any change in direction will achieve the above effect. However, the applicant has found that the greater the change, the greater the effect. Thus, it is not necessary for the directions d1 and d2 in the tunnel freezer 1 to be opposite to each other, but it is particularly effective.

[0067] The following embodiments can also be contemplated: wherein when considered in the conveying direction, the difference between the first direction and the second direction is at least 10 degrees, at least 45 degrees, or at least 90 degrees.

[0068] Furthermore, although in the tunnel freezer 1, the air flow changes at two points along the conveyor unit 3 (from section 2C to 2D, and from section 2D to 2E), a single change in direction would also have provided the desired effect.

[0069] Triggering these phase changes in the tunnel freezer 1 ensures that the latent heat is released in an environment where this heat can typically be removed from the food.

[0070] Triggering these phase changes in the tunnel freezer 1 also ensures that they do not ultimately occur when the food is in storage. Thus, food cooled using the tunnel freezer according to the invention will have a more constant final average temperature.

[0071] Reference Figure 2A and Figure 2B , shows the freezing sections 2C, 2D, and 2E. Each freezing section includes a cooling element 4. In Figure 2A and Figure 2B it is specifically shown that in the freezing sections 2C and 2E, a first ventilator 5A is arranged to force air upward (first direction d1) through the food layer, and in section 2D, a second ventilator 5B is arranged to force air from top to bottom (second direction d2) through the layer. In Figure 2A and Figure 2B both, the conveyance of the food can generally be described as from left to right.

[0072] There are housing walls 6 between the freezing section 2C and the freezing section 2D and between the freezing section 2D and the freezing section 2E. In these housing walls, slots 7 are provided through which the conveyor unit extends. As Figure 2A and Figure 2B shown, the tunnel freezer 1 is also provided with an optional deflector 8. Optionally, there are also housing walls 6 between the housing sections 2A and 2B and between the housing sections 2B and 2C.

[0073] Reference Figure 3A and Figure 3B , shows a cross-section in a plane perpendicular to the conveying direction representing the freezing section 2C or 2E. The freezing section 2C / 2E likewise includes a housing 2, a belt conveyor 3, one or more cooling elements 4, one or more ventilators 5A, slots 7, and a deflector 8.

[0074] In Figure 3ASpecifically pointed out in the text, the housing 2 is divided into a first partition 21, a second partition 22 and a third partition 23. Air flows from the ventilator 5A through the first partition 21 (F1) to the belt conveyor 3. The air further flows through the belt conveyor 3, and when there is a food layer on the belt conveyor, the air is forced through the food layer. The air further flows from the belt conveyor 3 through the second partition 22 (F2) to the cooling element 4. The air further flows through the cooling element 4 and is cooled during this process. The air further flows from the cooling element 4 through the third partition 23 (F3) and returns to the ventilator 5A.

[0075] In Figure 3B it is shown that the deeper the area, the higher the air velocity. By pushing air into the first partition 21, the ventilator 5A increases the pressure in the first partition 21. At the same time, the pressure in the second partition 22 generally remains unchanged or increases slightly. The resulting pressure difference naturally ensures that the air present in the first partition 21 forces its way through the belt conveyor 3 and, when present, through the food layer P, entering the second partition 22 from bottom to top.

[0076] Reference Figure 4A and Figure 4B show a cross-section in a plane perpendicular to the conveying direction of the freezing section 2D. The freezing section 2D also includes a housing 2, a belt conveyor 3, one or more cooling elements 4, one or more ventilators 5A, a slot 7, and a deflector 8.

[0077] In Figure 4A it is specifically pointed out that the housing 2 is divided into a fourth partition 24, a fifth partition 25 and a sixth partition 26. Air flows through the sixth partition 26 (F3) to the cooling element 4. The air further flows through the cooling element 4 and is cooled during this process. The air further flows from the cooling element 4 through the fifth partition 25 (F2) to the belt conveyor 3. The air further flows through the belt conveyor 3, and when the air appears on the belt conveyor, the air is forced through the food layer P. The air further flows from the belt conveyor 3 through the fourth partition 24 (F1) towards the ventilator 5B. In Figure 4B it is shown that the deeper the area, the higher the air velocity. By extracting air from the fourth partition 24, the ventilator 5A reduces the pressure in the fourth partition 24. At the same time, the pressure in the second partition 25 generally remains unchanged or increases slightly. The resulting pressure difference naturally ensures that the air present in the fifth partition 25 forces its way through the belt conveyor 3 and, when present, through the food layer P, entering the fourth partition 25 from top to bottom.

[0078] The following embodiments of the freezing sections 2C / 2E can be conceived: in which an upward air flow is achieved by reducing the pressure in the second partition 22 while generally keeping the pressure in the first partition 21 the same. The following embodiments of the freezing section 2D can be conceived: in which a downward air flow is achieved by increasing the pressure in the fifth partition 25 while generally keeping the pressure in the fourth partition 24 the same. In both types of freezing sections, the cause of the air flow is the pressure difference between the two partitions below and above the belt conveyor 3.

[0079] In order to ensure that the belt conveyor 3 can convey the food layer from the freezing section 2C to the freezing section 2D, and from the freezing section 2D to the freezing section 2E, a slot 7 is provided in the housing wall 6.

[0080] The slot is large enough for the belt conveyor 3 to extend through and into the part of the housing wall 6 that defines the second partition 22 of the freezing section 2C / 2E and the fifth partition 25 of the freezing section 2D.

[0081] Preferably, the slot 7 extends into the said part of the housing wall 6 by a distance approximately equal to the thickness of the layer of food, or slightly further. This allows the food layer to pass through the slot. The slot 7 creates an open connection between the second partition 22 of the freezing section 2C / 2E and the fifth partition 25 of the freezing section 2D for the food to pass through.

[0082] Therefore, those skilled in the art will recognize that the tunnel freezer 1 is a particularly advantageous embodiment because in each housing section thereof, the required pressure difference between the partition above and below the belt conveyor 3 is provided by changing (e.g., increasing / decreasing) the pressure in the partition below the belt conveyor 3 (e.g., in the first partition 21 / fourth partition 24) while generally keeping the pressure in the partition above the belt conveyor 3 (e.g., in the second partition 22 / fifth partition 25) the same.

[0083] Optionally, the slats can be attached to the upper edge of the slot 7 in a hinged manner. This is the edge of the slot 7 opposite to the side of the belt conveyor 3 where the food can be arranged. Such slats have a rest position in which gravity pulls them downwards, thus providing a substantial barrier between the adjacent sections defined by the corresponding housing wall. Since they are connected in a hinged manner, the passing food can push them to one side to ensure passage. These slats improve the containment of the air - material flow in the adjacent housing sections defined by the corresponding housing wall.

[0084] Preferably, the slot 7 does not extend into the portions of the housing wall 6 that define the first partition 21 and the fifth partition 25 of the freezing sections 2C / 2E. This allows the first partition 21 of section 2C or 2E to be sealed with the fourth partition 24 of section 2D, and vice versa. This sealing can be achieved by bringing the lower edge of the slot 7 as close as possible to the lower side of the conveyor belt 3. Alternatively, it can also be achieved by providing some additional sealing means (such as one or more rubber elements) between the lower edge of the slot 7 and the lower side of the conveyor belt 3.

[0085] This sealing, in combination with the arrangement of the fans 5A and 5B discussed earlier, enables a higher pressure difference to be generated between the first partition 21 of section 2C or 2E and the fourth partition 24 of section 2D, and vice versa.

[0086] To avoid blockages in the food layer when the air flow is forced to pass through the food layer from top to bottom, the conveyor belt included in the conveyor 3 can be suspended loosely. In the context of the present application, this should be understood as between the pulleys that suspend the conveyor belt, the conveyor belt starts from one pulley, first decreases in height, then increases in height, and then reaches the next pulley. This slack causes a change in the slope of the conveyor belt. When the food layer is conveyed on a conveyor belt with a changing slope, especially when the slope changes downward, and even more so when the slope changes from a positive slope to a negative slope, the food layer has at least a slight natural tendency to rearrange itself, thereby creating new openings in the food layer for the air flow to be forced through from top to bottom. Other devices for rearranging the layers of food can also be included.

[0087] Those skilled in the art will understand that the tunnel freezer 1 can be operated to freeze any of various types of food. Given a specific type of food, the supercooling temperature range can be determined. The supercooling temperature range includes those temperatures when the water present in the food is supercooled.

[0088] The layered food can then be cooled until the average temperature of the food is within the supercooling temperature range. For the tunnel freezer 1, this can be achieved, for example, using the freezing section 2C or a combination of the housing sections 2A, 2B, and 2C. To achieve this, several configurations of the tunnel freezer can be adjusted, such as but not limited to the speed of the conveyor belt 3, the cooling capacity of the cooling element 4, and / or the power supplied to the multiple fans 5.

[0089] When the average temperature of the food is within the supercooling temperature range, the layered food can then be conveyed into the second housing section. For the tunnel freezer 2, this can be achieved by the conveyor belt 3 that conveys the food layer from the freezing section 2C to the freezing section 2D.

[0090] In the foregoing, the present invention has been described with reference to detailed embodiments. However, the present invention is not limited to these embodiments. Instead, various modifications can be made without departing from the scope of the present application as defined by the appended claims.

Claims

1. A tunnel freezer configured to freeze food arranged in layers, the tunnel freezer comprises: a housing including a plurality of housing segments, a conveyor unit configured to convey a layer of food through each of the plurality of housing segments, each housing segment including a ventilator for providing a flow of gaseous medium and a cooling unit arranged to cool the gaseous medium in the flow, wherein: - a first housing segment of the plurality of housing segments is configured to force the flow of the gaseous medium to flow through the layer of food in a first direction, - a second housing segment of the plurality of housing segments is configured to force the flow of the gaseous medium to flow through the layer of food in a second direction different from the first direction; wherein the food has a determined supercooling temperature range within which the water in the food is supercooled; wherein the first housing segment is configured to cool the layer of food until the average temperature of the food is within the supercooling temperature range; and wherein the conveyor unit is configured to convey the layer of food into the second housing segment when the average temperature of the food is within the supercooling temperature range.

2. The tunnel freezer according to claim 1, wherein the food is French fries, green beans, carrots, or any other type of elongated food.

3. The tunnel freezer according to claim 1 or 2, wherein the conveyor unit is configured to convey the layer of food from the first housing segment to the second housing segment when the percentage of the food in a supercooled state is within a predetermined range; the range is preferably 20% to 80%, more preferably 30% to 70%, and even more preferably 40% to 60%.

4. The tunnel freezer according to claim 1, 2 or 3, wherein the first direction is from top to bottom or from bottom to top, and / or wherein the second direction is opposite to the first direction.

5. The tunnel freezer according to any one of the preceding claims, wherein the housing is elongated and wherein the plurality of housing segments are longitudinally distributed on the elongated housing.

6. The tunnel freezer according to any one of the preceding claims, wherein the gaseous medium is air.

7. The tunnel freezer according to any one of the preceding claims, wherein the first housing segment and the second housing segment are substantially isolated from each other such that the flow of the gaseous medium flowing through these respective housing segments is substantially contained within the respective housing segments.

8. The tunnel freezer according to any one of the preceding claims, wherein the plurality of housing segments further includes a third housing segment configured to force the flow of the gaseous medium to flow through the layer of food in the first direction, and wherein the conveyor unit is configured to sequentially convey the food through the first housing segment, the second housing segment and the third housing segment.

9. The tunnel freezer according to claim 8, wherein the amount of time the food is conveyed through the first housing section is approximately twice the amount of time the food is conveyed through the second housing section and / or the third housing section, and / or wherein the amount of time the food is conveyed through the second housing section and the third housing section is approximately equal.

10. The tunnel freezer according to claim 8 or 9, wherein the conveyor unit is configured to convey the food through the first housing section, the second housing section, and the third housing section at a substantially constant speed.

11. The tunnel freezer according to any one of the preceding claims, wherein the conveyor unit is a belt conveyor, the belt conveyor comprises: a conveyor belt on which the food can be spread to form the layer, and wherein the conveyor belt is preferably provided with a plurality of holes to allow the flow of the gaseous medium to flow through the conveyor belt.

12. The tunnel freezer according to claim 11, wherein, in at least one housing section configured to force the flow of the gaseous medium to flow downward through the layer of the food, the belt is suspended slackly.

13. The tunnel freezer according to any one of the preceding claims, wherein: the first housing section is configured to force the flow of the gaseous medium to flow upward through the conveyor unit, and / or the second housing section is configured to force the flow of the gaseous medium to flow downward through the conveyor unit.

14. The tunnel freezer according to any one of the preceding claims, wherein, each housing section is divided into a first partition and a second partition, wherein the second partition is defined from the first partition by the conveyor unit and by a separating device including an opening, and the ventilator is arranged in the opening; wherein the conveyor unit is permeable to the gaseous medium, and wherein the separating device is made of a material impermeable to the gaseous medium.

15. The tunnel freezer according to claim 14, wherein at least a part of the first partition is adjacent to the lower side of the conveyor unit, and / or wherein at least a part of the second partition is adjacent to the upper side of the conveyor unit.

16. The tunnel freezer according to claim 14 or 15, wherein, in the first housing section, the ventilator is arranged to extract the gaseous medium from the second partition and push the gaseous medium into the first partition, and / or the ventilator is arranged to increase the pressure in the first partition relative to the second partition, thereby forcing the gaseous medium to pass through the conveyor unit from the first partition and, when the layer of the food is arranged on the conveyor unit, through the layer of the food into the second partition, thereby providing the flow of the gaseous medium.

17. The tunnel freezer according to claim 14, 15 or 16, wherein, In the second housing section, the ventilator is arranged to extract the gaseous medium from the first compartment and push the gaseous medium into the second compartment and / or reduce the pressure in the first compartment relative to the second compartment, thereby forcing the gaseous medium to pass through the conveyor unit from the second compartment and, when the layers of food are arranged on the conveyor unit, through the layers of food into the first compartment, thereby providing a flow of the gaseous medium.

18. Tunnel freezer according to any one of the preceding claims, wherein the first housing section and the second housing section are adjacent to each other.

19. Tunnel freezer according to any one of the preceding claims, further comprising: a housing wall arranged between the first housing section and the second housing section, the housing wall including a slot through which the conveyor unit extends.

20. Tunnel freezer according to claim 19, wherein the conveyor unit includes a first side and an opposite second side on which the layers of food are to be transported.

21. Tunnel freezer according to claim 20, further comprising a slat hingedly attached to a first edge of the slot opposite the first side of the conveyor unit and / or the slat is configured to at least partially contain the flow of gaseous material in the housing sections on both sides of the housing wall.

22. Tunnel freezer according to claim 20 or 21 and any one of claims 14 to 17, wherein the gap between the second side of the conveyor unit and a second edge of the slot opposite the second side is small enough to allow a pressure difference to exist between the first compartment of the first housing section and the first compartment of the second housing section.

23. Tunnel freezer according to any one of claims 19 to 22 and any one of claims 14 to 17, wherein the slot: extends at least partially into the part of the housing wall arranged between the second compartment of the first housing section and the second compartment of the second housing section and / or does not extend into the part of the housing wall arranged between the first compartment of the first housing section and the first compartment of the second housing section.

24. Tunnel freezer according to any one of claims 14 to 17, wherein the plurality of housing sections includes an end housing section, the end housing section being a front housing section or a rear housing section, and wherein the part of the housing defining the end housing section includes an opening through which the conveyor unit extends, and wherein the opening: extends at least partially into the part of the housing defining the second compartment of the end housing section and / or does not extend into the part of the housing defining the first compartment of the end housing section.

25. Tunnel freezer according to claims 23 and 24, wherein the pressure in the first compartment of each housing section of the housing sections is substantially equal to the ambient pressure and / or substantially equal to the standard atmospheric pressure.

26. A tunnel freezer according to any one of the preceding claims, wherein, in the first housing section and the second housing section, the gaseous medium flowing through the layer of the food is between about -18 and about -36 degrees Celsius, preferably about -24 degrees Celsius.

27. A tunnel freezer according to any one of the preceding claims, wherein the plurality of housing sections further includes a precooling section, in which the gaseous medium flowing through the layer of the food is between about 28 and about -1 degree Celsius, and wherein the conveyor unit is preferably configured to first convey the food into the precooling section.

28. A method for freezing food arranged in layers, the method preferably using a tunnel freezer according to any one of the preceding claims, wherein the food has a determined supercooling temperature range within which the water in the food is supercooled, the method comprises: using a conveyor unit to convey a layer of the food through each of a plurality of housing sections included in a housing; in each housing section, providing a flow of a gaseous medium and cooling the gaseous medium in the flow, in a first housing section of the plurality of housing sections, forcing the flow of the gaseous medium to flow through the layer of the food in a first direction, and cooling the layer of the food in the first housing section until the average temperature of the food is within the supercooling temperature range, when the average temperature of the food is within the supercooling temperature range, using the conveyor unit to convey the layer of the food into a second housing section of the plurality of housing sections; and in the second housing section, forcing the flow of the gaseous medium to flow through the layer of the food in a second direction different from the first direction.

29. A method for operating a tunnel freezer for freezing food, the food having a determined supercooling temperature range within which the water in the food is supercooled, the tunnel freezer comprises: a housing including a plurality of housing sections, a conveyor unit configured to convey a layer of food through each of the plurality of housing sections, each housing section including a ventilator for providing a flow of a gaseous medium and a cooling unit arranged to cool the gaseous medium in the flow; wherein a first housing section of the plurality of housing sections is configured to force the flow of the gaseous medium to flow through the layer of the food in a first direction, and a second housing section of the plurality of housing sections is configured to force the flow of the gaseous medium to flow through the layer of the food in a second direction different from the first direction; the method comprises: cooling the layer of the food in the first housing section until the average temperature of the food is within the supercooling temperature range, and, when the average temperature of the food is within the supercooling temperature range, conveying the layer of the food into the second housing section.

30. A method for operating a tunnel freezer according to claim 29, wherein the tunnel freezer is a tunnel freezer according to any one of claims 1 to 27.

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