Method for preparing fish product

A method for preparing a fish product. In the method, a slaughtered fish is filleted in pre-rigor state, skin is removed from the fillet in pre-rigor state, the skinless fillet is arranged in a pre-salting process in pre-rigor state and allowed to remain there for the pre-salting period, the fillet is removed from the pre-salting process, the fillet is arranged in its transport package, in which it is subjected to a second salting process, and the fillet is allowed to remain in the transport package for at least one day.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase entry of International Application No. PCT/FI2016/050885, filed Dec. 16, 2016, which claims priority to Finnish Patent Application No. 20155968, filed on Dec. 18, 2015, the entire contents of which are incorporated herein by reference.

BACKGROUND

The invention relates to a method for processing fish into food.

In the fish processing industry, fish are typically slaughtered at an entirely different location to where they are consumed; for instance, fish is produced in Norway and consumed in Central or Southern Europe. Because of this, the transport time for fish is long, typically 4 to 7 days. In addition, processing fish into a fish product for delivery to end-users, such as wholesalers, retail outlets, restaurants, or households, may take as many as 7 more days. The problem is that, after such a long period, it is not possible to prepare a high-quality fish product from such fish, due to factors such as uncontrolled autolysis caused by the enzymes in the fish meat.

BRIEF DISCLOSURE

The method behind the invention is characterised by what is stated in the independent claim. The other embodiments of the invention are characterised by what is disclosed in the rest of the claims.

The idea is that, using the presented method, the slaughtered fish is filleted in its pre-rigor state, skin is removed from the fillet in the pre-rigor state, the skinless fillet is arranged in a pre-salting process in the pre-rigor state and allowed to remain there for the pre-salting period, the fillet is removed from the pre-salting process, the fillet is arranged in its transport package, in which it is subjected to a second salting process, and the fillet is allowed to remain in the transport package for at least one day.

The advantage of this is that autolysis is brought under control, as a result of which the degradation in the quality of the fish product due to autolysis can be substantially reduced. In this description, autolysis refers to the proteolysis caused by enzymes in the tissue of the fish, which begins immediately after death. Uncontrolled autolysis unfavourably affects the sensory properties of fish: taste, smell, colour, and structure. Uncontrolled autolysis also promotes the microbiological deterioration of the fish by producing peptides and amino acids that bacteria use as nutrients.

Inventive embodiments are also disclosed in the specification and drawings of this application. The inventive content of the application may also be defined differently than in the claims presented below. The inventive content may also consist of several separate inventions, particularly if the invention is examined in the light of disclosed or implicit subtasks or from the point of view of gained advantages or groups of advantages. In such a case, some of the definitions in the claims below may be irrelevant to the separate inventive ideas. The features of the different embodiments of the invention may be applied to other embodiments within the scope of the basic inventive idea.

For the sake of clarity, the figures show the invention in a simplified manner.

DETAILED DESCRIPTION

FIG. 1shows the most essential method steps of an embodiment of the method in general.

After the fish is slaughtered1, it is filleted2as soon as possible and in any case while the fish is still in pre-rigor state.

During filleting2, it is also possible to trim the fillet, i.e. form a fillet of a desired shape. In this context, it should be noted that the term “fillet” refers herein to a fish flank without the backbone, with the flesh intact on both sides of the bones.

After filleting2, the skin3is removed from the fillet, and preferably also the dark meat under the skin.

According to one approach, the ‘110’ attachment of the bones to the fillet flesh is affected. The attachment mechanism of the bones can be affected in many ways when the fish fillet is skinless: for example mechanically, electrically, thermically, chemically, or by a combination of these. At best, effect110essentially targets the area of the bone rather than the entire fillet.

Affecting bone attachment through110can be implemented, for example, by the following means: (a) cutting the end of the bone away with a blade, (b) targeted electrical stimulation, (c) a precise, targeted thermal shock, for example with a laser, (d) injecting salt or a suitable enzyme in the vicinity of the bone, (e) a targeted ultrasound pulse or other vibration, (f) a high-pressure water jet that may be pulsed, or a combination of these.

According to one idea, affecting110the bone attachment does not remove the bones; rather, the bones are not removed until after the pre-salting process, once the salt (NaCl) has had time to affect the area around the bones.

According to an idea, at the latest after the removal of the skin, the fish meat is subjected to antibacterial treatment4. Antibacterial treatment4may comprise ozone treatment in gaseous or liquid form, such as water, dissolved ozone (O3), concentrated saline solution (salt content 8 to 33%), saline solution with ozone and/or hypochlorous acid (HCIO) dissolved therein, ultra violet light, laser radiation, alcohol or a combination of the above-mentioned treatments.

According to an idea, the antibacterial treatment4comprises plasma treatment with either cold or hot plasma. Cold plasma treatment uses gas having only a small part, such as approximately 1%, of the gas molecules ionised, whereas in hot plasma treatment, the gas is ionised almost entirely. With the treatment, it is possible to destroy any adverse microorganisms on the surface of the fillet without substantially heating the fillet. It should be noted that in a fresh fillet that is prepared with the method described herein, microorganisms are on the surface of the fillet and can be destroyed before they enter the meat. A useful plasma treatment method is a method that goes by the tradename Openair® Plasma.

According to an idea, a washing/rinsing treatment of the fillet is combined with the antibacterial treatment. Further, the antibacterial treatment can be performed in such a manner that it contains a function that cools the fillet. For instance, the washing/rinsing water may be so salty that its temperature can be lowered to below zero.

According to an idea, the fillet is cooled immediately after filleting to a low temperature, preferably below 8° C., to approximately 0° C., for example. The cooling can be done using sprayable or dousable saline solution having a temperature of +8° C. to −20° C., for instance.

The above-mentioned work processes are performed as quickly as possible after slaughtering, within an hour, for example. The faster it is done, the better the quality of fillet can be achieved.

A skinless fillet is placed in a pre-salting process for 3 to 48 hours, for example, after which the bones are removed from the fillet.

According to an idea, in pre-salting process5, a solution salting method is used, wherein the salt content of the solution is 1.5 to 33%, preferably 10% at most. In solution salting, the temperature of the fillet is below +4° C., preferably 0° C. or even lower. Salt typically comprises sea salt, i.e. sodium chloride (NaCl), but it may also comprise potassium chloride (KCl), for instance. It should be noted in this context, that the percentages (%) given in this description are percentage by weight, unless otherwise stated.

According to another idea, in pre-salting process5, an injection salting method is used, wherein a 5 to 33% saline solution is injected into the fish meat.

Pre-salting5may last for 3 to 48 hours, for instance, but preferably 3 to 24 hours. During this time, the fillet may, for instance, be transported 6 closer to the end market.

According to an idea, the salting degree of the fillet after pre-salting is 0.5 to 4%, for instance.

Solution salting can be done freely, in which case the fillets are freely in the saline solution, or alternatively in such a manner that the fillets are in a controlled manner in the saline solution, stacked in a certain way, for example. In the embodiment mentioned last, it is possible to influence the contraction of the fillet by setting the fillets under pressure, for instance.

According to an embodiment, after the pre-salting5, the bones are removed7from the skinless and pre-salted fillets. Bones can be removed by known bone removal machines. Thanks to the pre-salting5and skinlessness, the pulling force required to remove the bones is reduced to at least a third of the original force. For example, a typical pulling force of bones from a pre-rigor salmon fillet is approximately 1400 grams and is reduced to approximately 250 grams typically only after five days. Thanks to pre-salting5, the pulling force is approximately 250 grams in less than 24 hours as salt weakens the adhesion of the bone.

According to another embodiment, bones are only removed at a later stage, after the fillet has been taken out of its transport package.

According to an idea, a skinless and pre-salted fillet can be treated before the removal of the bones by electrostimulation12, with which the transfer of the fillet into post-rigor state and/or the removal of the bones can be speeded up.

After the bones have been removed7, the fillet is a skinless and boneless initially-salted fillet. The fillet is also as bacterially clean as possible or even sterile. The fillet may also be trimmed to its final form. It is only at this stage decided, which final product will be prepared from the fillet. A salmon fillet can be prepared into salt-cured salmon or a cold-smoked salmon fillet.

It should be noted in this context that no sugar or other spices are used in pre-salting5. Any required spices are added to the fillet only at spicing step8, which is just before packaging9and transportation10to the destination, which is a fish processing plant, such as a smokehouse, wholesaler or retail outlet, restaurant, or private customer. Said spices may be sugar, pepper, dill, dry salt and/or any other spice known per se. It is also possible to add aromatic oil or alcohol.

Even though no salt was added in the spicing step8, a certain part of the salt used in the pre-salting5will remain. Therefore, the fillet is in a second salting process, which is a dry-salting process, during transport10. In other words, the fillet is salted in a two-step salting process, in which it is in the solution salting process during pre-salting5and in the dry-salting proves during transport10. Solution salting prevents or at least substantially reduces the tendency of the fillet to contract. The dry-salting process drains water from the fillet, which improves the hygiene level and general quality of the fillet. In addition, the dry-salting process enhances the absorption of the spices into the fillet.

During packaging9, the fillet is packed into a package that may be a protective gas package (MAP), vacuum package, pressure-aided vacuum package, mechanical pressure package with protective gas, or antibacterial ozone package/transport system, or some other suitable package. These package formats are described in more detail below.

According to an idea, during transport, the temperature is in the range of −5° C. to +4° C., preferably 0° C. or even lower, i.e. “super-chilled”, which refers to a temperature range of −1.5° C. to −4° C. The super-chilled state is achieved in such a manner, for instance, that the fillet is cooled quickly, whereby part of the fish meat freezes on its surface to a depth of 1 mm, for example, or in such a manner that small ice crystals form in the fish meat. The cooling needs to be efficient and fast, because otherwise large ice crystals form and they destroy the meat completely. To reach the super-chilled state, cooling tunnels having a temperature of −60° C. are typically used.

According to an idea, while the fillet is in its transport package in the second salting process, the process liquid formed in the package is recovered so that it cannot affect the quality of the fillet in any way. This is done, because the process liquid contains dissolved proteins and other muscle residue that affect adversely the quality of the fillet.

According to an idea, the fillet is in its transport package under pressure, when the fillet is cured, which corresponds to a dry-salting process. The pressure may be a weight of 2 kg for the fillet, for example, when salt-cured salmon, salt/sugar salmon or raw material for cold-smoked salmon, for instance, is made. The pressure enhances water drainage from the fillet, whereby the correct texture is achieved in the meat, when it arrives at its destination. At the same time, it is ensured that the meat is bacteria-free, because water activity in the meat is less than 0.90 aw.

FIG. 2shows the quality of a fish product achieved by the method described in this description in comparison with previously known fish products. Herein, a measuring system of the French company, NovoCib, is applied to the measurement of the freshness of the fish product. Said measuring system has been disclosed in publication Journal of Food Science-Volume 63, No 4, 1998, pages 634 to 637, D. Wang et al. “Postmortem Changes of Cultivated Atlantic Salmon and Their Effects on Salt Uptake”.

Reference numbers13and14show the IMP (Inosine Mono Phosphate) measurements on the fillets that are taken from the same fish, but from opposite halves. IMP indicates the freshness of the product in such a manner that the higher the number, the fresher the product. Said fish is a 6 kg farmed salmon from Norway and represents one of the best qualities in the world from a farmer that supplies sashimi-quality pre-rigor salmon fillets to Japan.

Reference number13represents a fillet made with the method described in this description, whereas reference number14represents a fillet made with a previously known method.

As shown inFIG. 2, the difference in IMP values is significantly in favour of the method described in this description, because the IMP value13of the fillet made with it is 80%, whereas the IMP value14of the fillet made with the previously known method is only 55%, as measured 24 hours from slaughter. The difference only increases with time.

Hypoxanthine (Hx) values also show a clear difference in favour of the present method. Reference number18represents a Hx measurement of a fillet made with the method described in this description, whereas reference number17represents a fillet made with a previously known method. Both fillets are of the above-mentioned highest possible quality.

The Hx value18of the fillet made with the present method remains constant at a range of approximately 4% during 48 hours, and actually considerably longer as long as the temperature is sufficiently low, such as 0° C.

Instead, the Hx value17of the sashimi-quality fillet made with the known method has already risen to 12% during the first day and exceeds 40% after 14 days.

In the above-mentioned measuring results, the raw material was a premium-quality salmon farmed with special diets and a fish density of less than 10 kg/m3 water.

In farming a normal-quality open water salmon, the fish density in the pool is approximately 25 kg/m3 water and, in closed pools, the density may be even 150 kg/m3 water.

Curve15represents the IMP value development and curve16the Hx value of a normal-quality fish that is typically sold in stores. As can be seen, the IMP value decreases during one day from 78% to as low as 24%. Correspondingly, the Hx value increase during one day from 0% to 38%. This is still pre-rigor quality, even though already after one day, the Hx value of the fillet is higher than the IMP value.

The above-mentioned method for preparing a pre-rigor fillet comprises the transportation of the fillet with skin and bones to its destination, in which case it transfers from pre-rigor state to post-rigor state within 4 days, for instance, after which the bones can be removed from the fillet by known methods.

When the fillet is transported to its destination in accordance with the new method, it transfers into post-rigor state in such a manner that the level of microorganisms, such as bacteria, the level of lactic acid and/or the Hx level do not increase significantly. For this to happen, according to an idea, the temperature of the fillet is close to 0° C. and the salt content is at least 0.7%, preferably 2%, for example.

A combination of temperature and salt content affects autolysis very effectively: for instance, a salt content of 3% and a temperature of −1.5° C. substantially prevent the effect of autolysis on fish meat. Autolysis can be slowed down, as shown by the new method, by means of a suitable amount of salt (over 0.5%, preferably 3%) and low temperature (e.g. −1° C. to +1° C.) in combination with filleting, skin removal, and pre-salting processes quickly after slaughter (e.g. one hour after slaughter).

FIG. 3shows a comparison between a known method on the left and an embodiment of the method according to the present invention.

In the known method, the fish is slaughtered19and filleted in pre-rigor state, after which the fillet is placed typically with skin and bones intact into an insulated box with ice, and loaded into a transport vehicle as soon as possible. After this, the fillet is transported20at a temperature of 0° C. to +3° C. during 3 to 8 days to a fish processing plant, where first the bones are removed21from the fillet and the fillet is possibly salted typically with an injection salting method. The waiting time22is typically very short: usually cold-smoking23, for instance, is performed immediately after injection salting.

The above-mentioned work processes are performed on a fillet with the skin intact. The skin is only removed if the fillet is sliced and packed in small packages.

A problem with the known method is that it does not act on autolysis in any way and the fish is transported as a pre-rigor fillet with skin and bones intact. Another known method comprises delivering the entire fish to its destination. This method does not act on autolysis in any way, either. In fact, most fish products are prepared at the destination country from an entire fish. The reason for this is that transporting a fillet is problematic, since it is much more sensitive to deterioration than an entire fish.

Extremely low IMP values, which are mainly below 25% and even have an average of 16%, are measured from typical cold-smoked and salt-cured salmon prepared by known methods.

Because the known methods do not act on autolysis immediately after slaughter, i.e. in pre-rigor state, autolysis becomes uncontrollable. The result is that the freshness of the fish disappears very quickly, as indicated by the rapid change in the IMP value.

In the method described in this description, first pre-rigor filleting24is done and at the same time at least the skin and preferably also as much as possible of the dark meat under it are removed. The skin, in particular, but also the dark meat promotes substantially the growth of microorganisms, such as bacteria, yeast and viruses, in the fillet.

Pre-salting helps in removing bones, because it softens the tissues surrounding the bones. If the skin is in place, salt cannot affect the root area of the bones, that is, the place right under the skin, where the bone attaches strongest to the surrounding tissue.

If a slaughtered fish was healthy and undamaged, its meat is substantially free from harmful organisms. However, harmful organisms can transfer to the fish meat from an external source, such as air, work machine, tools, human beings, fish skin, or process water.

The first measure is to control the time function, that is, the time from slaughter to the time when a skinless fillet is placed in pre-salting. The quicker things are done, the better the quality will be. According to an idea, this time is at most 24 hours, preferably less than 1 hour and even more preferably at most 15 minutes.

Another important measure is to keep the temperature of the fillet low, because the higher the temperature, the fiercer the contraction of the pre-rigor fillet and the stronger the reproductive and contamination capability of the foreign microorganisms. According to an idea, the temperature should not be higher than +12° C. during the filleting step, preferably as close to or even below 0° C., such as −1° C. to +1° C. Further, according to an idea, the temperature of the fillet must not be higher than the temperature during pre-salting.

In the next work phase26, the fillet is taken out of pre-salting, after which, according to an embodiment, bones are removed from it using known bone removal machines, such as a machine in the Marel Pinbone Remover MS series. According to an idea, spices can be added to the fillet, the fillet can be salted by a dry-salting method, for instance. Finally, the fillets are placed in a selected package depending on what end product is to be prepared of the fillet. The package formats are described later in this description.

The next measure is transportation27to the destination. The transportation typically takes 1 to 8 days. According to an idea, the fillet cures without heating under the effect of controlled autolysis during transportation so that it is ready for processing at its destination. It should be noted that in this description the term “curing” refers to curing without heating, unless otherwise stated.

The method of the invention is not necessarily longer in time than the known methods.

According to an idea, the method of the invention contains the transportation of a fillet in such a manner that the fillet becomes ready for use for cold-smoking or as such for salt-cured fish at the destination, and the transportation takes 2 to 8 days. This time may include one day for pre-salting and the rest for the second salting process, i.e. dry-salting.

According to an idea, after the pre-salting process and the subsequent bone removal, the fillet is brought to a spicing step, in which spices, such as sugar, pepper, dill, salt or some other known spice or mixture of spices, are added to the fillet. However, the spicing step is not an essential method step.

The skinless and, according to an embodiment, boneless fillet undergoes dry-salting in its package during transportation27—regardless of whether a spicing step took place or not or whether salt was added during the possible spicing step. The primary intention of the dry-salting process is to reduce the amount of water in the fillet. In the thus performed two-step salting process—pre-salting and dry-salting—the duration of the pre-salting process implemented by solution salting is typically 3 to 24 days, whereas the dry-salting process typically takes 1 to 8 days.

Since both salting steps can be performed while the fillet is transported, the new method is at least as fast as the known method in terms of transportation. The difference between the new and known methods is that in the known method, a “raw” fillet with skin and bones intact arrives at its destination, whereas in the new method, a skinless, boneless and cured fillet arrives at its destination.

FIG. 4shows some packing formats with which the pre-rigor fillets can be transported from the preliminary process to the final process that takes place preferably close to the end-product markets.

For instance, fish may originate from Norway, where it has been slaughtered, filleted and placed into pre-salting29. After this, the fillets can be transported to Sweden, for example, where the fillet33is taken out of pre-salting29, its bones are removed, and it is possibly seasoned with salt, sugar, pepper, citric acid, dill, or some other known spice or combination of spices.

After this, the fillet is placed in a transport package that may be a vacuum package36, vacuum-aided pressure package37, protective gas package38, salt-curing transport box39, protective gas-aided salt-curing transport box40, or contraction-controlled protective gas package/box41. The fish fillet is transported in these package formats to its final destination, which is France, Italy, USA, or China, for instance.

According to an idea, the pre-salting takes place as solution salting in a tub or container29and at a low temperature, such as 0° C.±1° C. The contraction can then be well controlled, and a fast uncontrollable contraction does not occur in a mild salt solution of less than 8%. In addition, in the salt solution31, the boneless and skinless fillets are, during this entire work phase, protected from microorganisms causing contamination. If the tub29is used as a transport container, it is preferably equip the tub29with a cover and to sterilise the free space between the salt solution31and cover30or to fill it with protective gas.

FIG. 5shows a means intended for controlling contraction of a fillet that can be placed in a protective gas package (MAP, Modified Atmosphere Package).

The means presses the pre-rigor fillet with suitable force, which reduces the rate and/or intensity of contraction.

The means comprises a net-like structure42made of elastic material that is a sock-like construction in shape, for instance. Between the net-like material or its strands46,47, empty space45remains that is for instance 40% of the surface area of the means, most preferably over 50% of the surface area of the means.

The strands may be made of polymer material, for example. The means is elastic in structure. The enlarged figure shows how the strands of the net-like material may be joined together to form a uniform net-like means.

According to an idea, the fillet is placed on a hard underlay, for instance, and both the fillet and underlay are place inside the means. According to another idea, the means is arranged around the fish fillet without an underlay.

The fillet is place in the means preferably before the salting process. The means does not stop the penetration of salt into the fillet, nor does it prevent an antibacterial treatment or sterilisation of the fillet owing to its open structure. The means directs pressure on the fillet to prevent or at least essentially reduce the contraction of the fillet in pre-rigor state and during salting, in particular.

FIG. 6shows an embodiment of a storage and/or transport container as a schematic cross-sectional view. A protective gas package50, its inside space49filled with a desired protective gas, is placed in the storage and/or transport container48. A liquid-absorbing pad51that produces carbon dioxide and/or citric acid when it becomes wet can also or alternatively be placed in the space.

The fillet52may be equipped with the pressing means shown in connection withFIG. 5, whereby the protective gas surrounds the fish fillet52, which boosts the operation of the protective gas.

The pressing means may be an elastic net-like structure (as shown in the figure) or rigid, box-like structure, for example, which is substantially open on its sides and shaped in such a manner that the process liquid produced in the dry-salting process may escape from the vicinity of the fish fillet. According to an idea, an insulation box48may comprise protective films50,53that form said protective gas package50.

The box48may be heat-insulating or non-heat-insulating.

The pressing means allows fillets52to remain separate from each other. Furthermore, the pressing means allows fillet52to be hung from or attached to the inner walls of box48or a separate frame470.

Box48may comprise a gas management system presented inFIG. 19. In this, stored gas such as carbon dioxide is fed into box48, preferably from a gas management system inside it, or alternatively, oxygen is used which is fed into an ozonisation system that generates ozone inside the box. Preferably, the box is equipped with a valve, allowing the gas to be changed and new gas to be fed in to replace it.

Box48preferably has a separate cover part54that forms a tight55entity when connected to box48.

Fillets with the skin intact can also be placed in box48, because the fillets can be kept separate from each other, thus eliminating contamination between skin and meat.

FIG. 7shows an embodiment of a pressure package as a schematic side view. Here, the fillet57is placed on an underlay58. Air or protective gas between the film60and underlay58has been removed with a vacuum packaging machine, whereby negative pressure has formed inside the package to press the fillet57. The negative pressure and pressing can be formed in the package, because the underlay58has an empty space59that does not compress even though air pressure surrounding the package is directed to it. The size of the pressing force may be 1 to 688 kg depending on the size of the negative pressure or, to be more precise, the difference in the pressures outside and inside the package.

The empty space59receives and also stores the process liquid from the fillet and generated during the salt-curing process, for instance. There may be 4 to 15% of process liquid based on the weight of the fillet. The empty space59is preferably dimensioned to be substantially larger than the estimated volume of liquid formed during the process.

The empty space59is positioned away from the fillet, i.e. the fillet is not in contact with the empty space59and the process liquid stored therein. Nothing reaches the fillet from the empty space59, when the movement is always in the direction of the negative pressure, or away from the fillet.

FIG. 8shows a pressure package as a schematic cross-sectional view. The fillet67is placed on an underlay62and both are surrounded by a packing film61. When air is removed from inside the packing film61with a vacuum machine, negative pressure is formed in cavities63in the underlay62, as a result of which the film61presses the fillet67. The cavity63also serves as a storage space for the process liquid.

The underlay62may comprise on its surface grooves or holes68that facilitate the travel of liquid from the fillet67to the cavities63inside the underlay62.

FIGS. 9 and 10show as a schematic cross-sectional view a salt-curing transport package with a large number of fillets in the same space. The number of fillets may be more than 10, for instance, preferably more than 100, such as 400 fillets.

The frame69of the salt-curing transport package is a box-like solution made of wood material, such as plywood, which is placed on an underlay71. Inside the frame69, an inner package70is placed, which may be made of a plastic film, for example, and forms a sealed boundary layer. An edge73of the inner package70can be bent over the edge of the frame69. According to an idea, supports or platforms72that remain outside the inner package70are arranged at the bottom of the frame69.

FIG. 10shows how an inner package70that forms a bag or inner trough is placed in the frame69. Inside it, a plate74is arranged and fillets77can be placed on it on top of each other. The process liquid leaking from the fillets77accumulates at the bottom of the frame69, which, according to an idea, holds an absorbing substructure75for liquid. This absorbing substructure75may be equipped with a CO2emitter which, when becoming moist, develops carbon dioxide gas or some other emitter of gas that improves the preservation of the product.

According to an idea, the bottom of the package is connected to the top of the box by means of a pipe81, for instance, so that gas is also allowed to enter the space above the fillets77.

After the package has been filled with fillets77, it is advantageous to close it in an air-tight manner. This can be done by gluing, welding, or hot-soldering80, for instance, the air-tight film79that closes the package to the inner package70.

According to an idea, a gas-filled flexible element700is placed into the box in an at least partially compressed form. This causes a pressing force to which the fillets are subjected, essentially preventing the fillets from moving around in the box.

Flexible element700may be, for example, a pressurised gas bladder such as an air bladder, or an element with a cellular structure with the cells filled with gas.

Protective gas, such as ozone or another gaseous substance, can be fed into the box.

It should be noted that frame69of the box shown inFIGS. 9 and 10can also be made of metal or plastic. Frame69may be reusable or disposable.

According to an idea, the salt-curing transport container described above is used to cure and/or salt-cure a fillet having a salt content of less than 5%. The produced process liquid is recovered so that it cannot affect the quality of the fillet. Thus, this is a dry-salting and curing process. Because the fillets are on top of each other, an optimum pressing force is formed in them and the fillet becomes firm and well preservable, because the movement of water in the meat has been minimised. A correct fillet has at least 2%, preferably at least 10% of the water in the filled removed during the salt-curing/salting process.

FIG. 11shows a small package83made of metal or plastic and intended for the transport of one or at most ten (10) fillets.

The frame of the package83is deep-drawn or injection-moulded plastic and/or metal. The bottom part of the frame83has deep shapes made into it to stiffen the structure of the package and to serve as cavities85, i.e. empty spaces, when a perforated plate84has been placed at the bottom of the frame.

As a result of the suction of negative pressure, the film or plastic film82presses the fillet81, because there is negative pressure in the cavities85. The cavities85are also used in receiving process liquid so that it does not come into contact with the fillet.

It is also possible to place a gas emitter into the cavities85to form protective gases, such as carbon dioxide, in the manner described earlier herein. The package83can be used in both vacuum packaging and protective gas packaging. According to an idea, a net-like means, described in connection withFIG. 5, is arranged in a protective gas package. This way, it is possible to affect the contraction of the fillet.

FIGS. 12 to 18show a method for transporting and storing fish fillets within an extremely precise temperature tolerance. This solves the problem related to the defrosting and freezing of a fillet that arises when storing the fillet close to its freezing point or when the fillet is in the so-called super-chilled state. Typically, a fish fillet freezes at a temperature below −1.4° C. According to an idea, and optimum transport and storage temperature for a fish fillet is −1.4° C.±0.1° C., when the fish fillet should not freeze at all. The freezing point of the fillet may, of course, also be lower than 1.4° C. depending on the salt content of the fillet.

According to another idea, the fillet is intentionally allowed to freeze in a controlled manner so that ice crystals form inside the fish meat or an ice surface is formed on the fish fillet. In such a case, it is possible that the transport temperature of the fillet is as low as −5° C.

If the temperature variation of the fillet is too great, the fillet may melt and freeze repeatedly, as a result of which large ice crystals form in the meat and break the meat. This type of meat is not of good quality and cannot be used in making cold-smoked salmon, salt-cured salmon or sushi salmon, for instance.

The new method solves this cooling/melting problem, because the temperature can be maintained at an accuracy of ±0.1° C.

FIG. 12shows on the left a known package92, in which a plastic film or the like95is arranged around a fish fillet94placed on a cardboard or plastic underlay90. When air is removed from inside the film, a known vacuum-packed fish fillet product is formed.

FIG. 12shows on the right a new package93, in which the underlay91contains cavities, i.e. empty space, in gas exchange-connection with the space, where the fillet94is. According to an idea, the underlay92is like the one shown inFIG. 7 or 8.

Typical for both underlays92,93is that the underlay92,93extends beyond the fillet94at their longitudinal ends and in the lateral direction. According to an idea, this is utilised in the manner described in the following.

FIG. 13shows an embodiment for positioning packages shown inFIG. 12, for instance, into a storage and transport container105. The container105typically has a bottom part100, top part101, and vertical parts99on both sides to form a box-like structure. The containers105can be placed on top of each other and/or beside each other, and their walls and surfaces are typically straight, i.e. planar.

The container105is open into at least two directions either entirely or partly so that cooling air can flow through the container105and cool the fillets94that are placed on the underlay90,91, for example, shown inFIG. 12. According to an idea, the container105is shaped in such a manner that the fillets94or their packages do not touch each other and there is a free space between them for air flow to flush all surfaces of the package that are essential for cooling the fillet.

According to an idea, the bottom and top parts of the container are mostly—that is more than 50%, but preferably more than 80%—open. This way, two or more containers105can be stacked on top of each other to form a tower-like structure, in which air can flow laminarly through all containers in the stack. For the air flow to enter and exit said tower structure, flow space is arranged under the lowest container105and above the highest container105. The container105can be shaped to have more than one open wall. According to an idea, the container105is only a frame or rack with no or only a few actual surface plates. According to an idea, the container105covers only 50%, preferably 40% and more preferably 30% and even more preferably 10% of its external surface area by walls.

The underlays90,91are preferably arranged in the container105in such a manner that they are aligned with the air flow, in other words, the narrow edge of the fillet toward the air flow, as shown inFIG. 13.

The enlargement shows how the edge98of the underlay90,91is in the corresponding recess or groove97of the container105. This way, the packages and fillets94remain in a specific position so that air may flow in a controlled manner between the packages.

In this context, it should be noted that the fillets can be packed into the container105in any way as long as they can be kept separate from each other for the air to flow in a controlled manner between the packages. Examples of this include hanging the fillets up, using a suitable spacer, etc.

FIG. 14shows an embodiment for arranging containers105shown inFIG. 13, for example, on top of each other in the transport space106, preferably cold storage, of a vehicle, such as truck.

According to an idea, the air flow108controlling the temperature of the fillets is directed at the tower structure formed by containers105. The tower is arranged on a platform, such as pallet, that allows the air to flow. The air flow108is produced and/or directed by an air flow unit96that is arranged to perform the temperature control of an entity made up of one or more towers. Preferably, each air flow unit96manages the temperature control of one tower. The temperature of the transport space106can be adjusted by one or more air flow units96. This way, the temperature of different parts of the transport space106can be controlled in a precise and controlled manner.

According to an idea, the air flow unit96directs the air flow to the containers105from the ceiling107of the transport space downward. However, the direction of the air flow can also be selected to be from the bottom up or sideways from the walls, for example.

In an embodiment, an air-permeable wall, such as a fabric, perforated or porous plastic film, or the like, which preferably extends the width and length of the transport space, has been placed on the ceiling107of the transport space. When air is fed between the ceiling107of the transport space and said wall, it spreads evenly on the entire surface area of the transport space.

In another embodiment, one or more bags with a diameter of 200 mm, for example, are arranged in the vicinity of ceiling107of the transport space parallel to the ceiling. The bag is made of air-permeable material, such as those already mentioned above. Through openings in the bag, the air flow is distributed evenly on the entire surface area of the transport space.

Small holes, such as microholes, can also be made into the wall or bag to allow a certain amount of air through. According to an idea, this type of wall or bag can also serve as an air filter.

According to an idea, the temperature of the transport space106is approximately 0° C. or below zero, 0° C. to −8° C., for example. Most preferably the temperature is between −1° C. and −1.5° C., in which case no ice crystals whatsoever typically form in the fillet. If the temperature is lower than this, −2° C. to −8° C., for example, partial freezing occurs.

FIG. 15shows an embodiment of using a container according toFIG. 13, for instance.

The container105is not heat-insulating in itself, actually quite the opposite. The container105can be arranged inside111the heat-insulating container110, in which case the container105can be transported to a restaurant or store without the fillets warming up.

In this context, it should be noted that the transport and storage of a fillet in its production and preparation phases is different from how the fillets are delivered to the storage of the end-customer, such as a restaurant or store.FIG. 15shows an embodiment of packaging the fillet for transport to the storage of the customer. This procedure is done in the very last phase after the transport part that belongs to the preparation of the fillet. For instance, the fillet is transported from Norway to Italy at a temperature of −1° C. as a transport according toFIG. 14and packed in a package according toFIG. 13. This transport ends in a distribution centre and only there the fillets are placed in a separate heat-insulated container, of which an embodiment is shown inFIG. 15. After the customer has made an order, the goods are delivered in the heat-insulated package.

FIG. 16shows an embodiment of the method, wherein protective gas packages113are transported and stored in a rack115that forms a shelf-like construction in such a manner that cooling air114,116,117can flow around the packages113everywhere.

The protective gas package113may be a one-fillet package or a protective gas package (MAP) for several, such as ten, fillets.

FIG. 17is a schematic representation of an embodiment of the method. A product, such as fillet, is packed and stored in a cold storage space119that has the same temperature as the transport vehicle118, for instance a truck, and the load is further unloaded directly into a cold storage space117that has the same temperature as the cold storage space119and transport vehicle118. This is a particularly advantageous procedure, when the temperature of the product is close to 0° C., such as −1° C., or in the range of “super-chilled”, such as −2° C. to −4° C. The inventors have found that for the quality of the fillet, the minimising of temperature variation is one of the most essential matters from the packaging time to the delivery to the customer, such as store or restaurant.

The concept “super-chilled” refers herein to the state of the fillet in which very small ice crystals are formed inside the fillet, for instance in such a manner that 5% to 25% of the water in the fillet is frozen, in the form of crystals.

FIG. 18shows a cold-storage vehicle with fish fillet packages placed in its cold storage space120in such a manner that a tower-like structure122is formed in the manner shown inFIG. 14.

According to an idea, a refrigeration element or air flow controller123is placed above the tower-like structure122. This way, an efficient laminar air flow is achieved from the top126through the tower-like structure122with the air flow exiting from under127said structure.

According to an idea, at least part of the energy required by the refrigeration elements or air flow controllers123is generated by solar panels121. The solar panels may be arranged on the roof of the cold storage space120, for instance. The typical length of truck cold storage space120is approximately 20 m and the width is 2.60 m, in which case the surface area of the roof is 20 m×2.50 m, i.e. 50 m2. A typical output is approximately 200 W/m2, i.e. this type of solution produces approximately 10 000 W or 10 kW.

FIG. 19shows an embodiment of the method that utilises a novel type of MAP package.

Typically in known MAP packages, the protective gas is put in the package together with the product, after which the package is hermetically sealed. This type of procedure can naturally be utilised in the present method.

The protective gas can also be formed in the hermetically sealed package during storage or transport by means of a gas emitter inserted in an absorbing pad, for instance, as already described above.

According to an idea, the MAP package comprises a valve that lets gas out of the package in a controlled manner, but does not allow gas to enter the package from the surroundings. In addition, the package comprises means for generating gas inside the package. In other words, the internal gas atmosphere of the package is renewable. This way, the gas atmosphere of the MAP package can be kept fresh and efficient.

According to an idea, the means for generating gas may comprise a gas emitter arranged inside the package to generate carbon dioxide and/or citric acid, or the like. The generated gas may form pressure in the package, which may be released through the valve from the package. However, the valve does not allow gas to enter through it into the package.

According to another idea, the means for generating gas may comprise a compressed gas container that is connected to supply gas into the package.

According to a third idea, the means for generating gas may comprise at least two gas-supplying gas container systems. The first gas container system is arranged to supply passive protective gas that does not kill bacteria but slows down their reproduction, especially in combination with a substantially low temperature. One passive protective gas of this type is carbon dioxide. The second gas container system is arranged to supply reactive gas that kills bacteria. One reactive gas of this type is ozone (O3), for example. Ozone may be already in a gas container or it may be made from oxygen gas supplied from a gas container in an ozone reactor reserved for this purpose. Because ozone is an unstable gas, it is preferable to produce it on site in an ozone reactor.

In the embodiment shown inFIG. 19, the gas container system comprises three containers with pure oxygen (O2) arranged in the first container125, with oxygen and a protective gas, which is carbon dioxide, mixed therein in the second container126, and oxygen and a protective gas, which is nitrogen (N2) in the third container127. The second and third container126,127may alternatively contain pure protective gas or a protective gas mixture, such as carbon dioxide and nitrogen.

The gas or gas mixture is led to a control centre124, through which gas of different type can be directed straight128or129to the package by adjusting valves131. The control centre124may be equipped with an ozone reactor for producing ozone.

The control centre124also preferably has a discharge system for the gas used in the package. This may be implemented, for example, by utilising the same channel, from which the gas is led in the package, but by turning the gas flow into the opposite direction. Another alternative is to use in the package a separate discharge channel, which may be equipped with a valve adjusting the gas flow.

According to an idea, the gas supply system only comprises an ozone reactor and oxygen gas source: as the ozone reacts with organic matter, it turns into carbon dioxide, i.e. protective gas, and water. The package can be equipped with a water-drainage channel or the like.

The volume of the gas container125,126,127is 1 to 100 ml, for instance, depending on the volume of empty space in the package.

According to an idea, the gas container is integrated into one unit with the control unit124, on one circuit board, for example. Said unit may comprise fastening elements, with which is quickly detached and replaced by a new unit.

FIG. 20shows an embodiment for placing a control centre132inside a package137, and another embodiment for placing a control centre133outside a package137. A fish fillet139is preferably positioned140in such a manner that gas surrounds it as much as possible from every side.

This type of modified atmosphere package (MAP) typically comprises only passive generated protective gas, such as carbon dioxide. However, other gases than just passive protective gases can be used, such as the reactive gases, such as ozone, already mentioned above, or a mixture of passive and reactive gases.

According to an idea, a MAP package is equipped with a valve136that lets gas out of the package, but not in the package. The valve136can also be placed in the control centre132,133in such a manner that used gas can be discharged from the package137.

According to an idea, the volume of the package137is 0.3 to 1 litres, but it may also be substantially larger than this, even up to 150 m3, in other words within the range of the cold storage space of the largest cold containers or cold storage vehicles.

With the valve in the package, a passive protective gas atmosphere can be replaced with a reactive gas atmosphere and vice versa. The supply of gases can be controlled by automatic control means known per se, which open and close the valves adjusting the gas flow from the containers to the package on the basis of signals provided by sensors monitoring the state of the package.

According to an idea, ozone is arranged in ice that is placed in a separate insulated package connected by a flow channel to the package. Ice is allowed to melt in a controlled manner, whereby ozone gas is released into the package. According to an idea, an MAP package using two or more gases contains at least 10 kg of fish product, preferably over 10 kg, such as 100 to 1000 kg fish product. According to an idea, this type of MAP package is one in which a pre-rigor fillet cures/is salted during transportation and in which process liquid is collected to prevent it from affecting the fillet. By using reactive gas in said package at least periodically, it is possible to reduce the growth of bacteria quite substantially.

An embodiment of the invention is presented inFIG. 21, where the salty and spicy liquid980formed during the dry-salting process is recovered for further processing.

Fish fillets990are under compression, causing liquid to be eliminated from the fish meat during the salt-curing process; this liquid comprises brine and possibly spices that have not been absorbed into the fillets but end up at the bottom of transport container960.

In a certain embodiment, the liquid in question is removed so that it can no longer come into contact with the fillets.

In another embodiment, the liquid in question is fed back into contact with the fillets, even being recirculated several times back into contact with the fillets. The benefit of this is that the absorption of salt and the spices into the fish meat can be enhanced. Said absorption is typically rather slow into meat that is in a pre-rigor state.

The utilisation of liquid used once can be implemented by, for example, by raising the liquid above fillets990and allowing it to flow back over the fillet surfaces to the bottom of transport container960. A pump pumping the liquid, for instance, can be used for this purpose, raising the liquid above the fillets via channel1000. In another embodiment, gas such as carbon dioxide or another gaseous substance1030is blown into the liquid at the bottom of the transport container, raising the liquid upwards in relation to the fillets. In both embodiments, fillets990sink towards the bottom of transport container960, because the saline solution no longer holds them up.

In an embodiment, used liquid is led away from the fillets by feeding it into enclosed space1040in transport container960; this space can be a bag arranged on top of or between the fillets, or in space1020outside transport container960.

Feeding the liquid into enclosed space1040does not change the total volume of the fillets and the liquid. This being the case, the increasing volume of the liquid collected in enclosed space1040and the resulting compression can be used to prevent the uncontrolled movement of fillets990inside transport container960. This embodiment of the method is still a dry salting method, because the fillets are under compression, and salt that removes liquid from the fish meat is applied. Another benefit is that the liquid keeps air away from the surface of the fish meat, resulting in non-existent oxidisation of the fish meat.

According to a certain idea, transport container960is of a drum type, whereby the fillets are arranged in a drum that can be closed. The drum can be rotated around its axis of rotation, rotating the bottommost fillet to the top, and vice versa.

The drum can be round, such as a clothes drying drum, for example, and preferably also perforated, allowing the liquid to flow out evenly.

Such a rotating fish curing drum can be encapsulated in such a manner that it becomes what is essentially a tight enclosure/package.

During transport, the drum rotates twice per day, for example.

The rotating force can be mechanical, for example implemented by a spring, or electrical.

The benefit is that the fillet compression force is nearly identical for all fillets, and its nearest equivalent is a traditional dry salting method from centuries ago in which the location of the fillets was changed twice per day. This original method is still used today, but only for expensive, high-quality products due to its being extremely labour-intensive.

The new application disclosed enables the performance of a curing procedure, such as dry salting, during transport.

In some cases, features disclosed in this application may be used as such, regardless of other features. On the other hand, when necessary, features disclosed in this application may be combined in order to provide different combinations.

The drawings and related disclosure are only intended to illustrate the inventive idea. It is apparent to a person skilled in the art that the invention is not restricted to the embodiments described above, in which the invention is disclosed through some examples, but various modifications and different applications of the invention are feasible within the inventive idea defined in the accompanying claims.