GB2464347A

GB2464347A - On-board processing method for fish

Info

Publication number: GB2464347A
Application number: GB0819006A
Authority: GB
Inventors: Indrajee James Weerawardena
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-10-16
Filing date: 2008-10-16
Publication date: 2010-04-21
Also published as: GB0819006D0

Abstract

A method for chilling fish, particularly tuna, on-board a fishing vessel comprises chilling the fish at a first temperature of -1.4°C to -2.0°C for less than four hours, then chilling at a second temperature of between -0.8°C and -1.5°C. The second temperature is higher than the first temperature. This helps the fish to be cooled as quickly as possible, but without freezing. The fish may be stored for up to 21 days at the second temperature. A recording system for recording information by marking each fish with a unique identifier and correlating the information recorded with the unique identifier is also provided. The information recorded may include the date of catching the fish, the estimated time of death and the core temperature of the fish before is enter the first chilling phase.

Description

On-board processing system The invention relates to an on-board system for processing and storing fish, in particular pelagic fish, especially tuna fish.

Fish which has been caught using a fishing vessel needs to be stored on-board the vessel until the vessel returns to land. To help preserve the fish during this time, it is conventional to provide an on-board system for chilling the fish.

Some large fishing vessels, which may be over 60 or 70 feet in length, use refrigerated water systems (RWS), which include tanks containing seawater at a temperature of below 0°C, for the on-board storage of fish. These vessels are primarily used to fish for large fish (e.g. large tuna fish, such as yellow fin and big eye tuna) The temperature of the refrigerated water system is not precisely controlled and fish are often stored for too long at loosely regulated temperatures. These systems tend to result in poor quality fish (usually between 20- 50% of fish are of poor quality), and a high level of rejection due to poor preservation. In particular, fish are usually crammed into the refrigerated water tanks until they are full, sometimes resulting in physical damage to the fish and some fish may be out of the water.

In addition, these large vessels generally use a long line system with 1500 to 2000 hooks being cast at any one time. This results in many fish dying on the line.

Smaller fishing vessels (i.e. those with a length of less than about 60 feet) tend to use hand lines to catch fish and normally preserve fish on-board on ice. However, the quality of fish that can be achieved using these methods is not consistently good, which leads to significant wastage. In particular, the majority of fish stored on ice deteriorate quickly. Fish stored in this way also tend to have high levels of histamine (which is a toxin and can lead to problems such as food poisoning in extreme cases) and significant spoilage.

Fish may also be frozen on-board the vessels, for example at temperatures ranging from -18°C to -40°C. However, the quality of the fish will deteriorate fairly rapidly upon de-frosting. The fish may also be super-frozen at -60°C, but when de-frosted the product will need to be consumed within 48 hours, otherwise the quality of the fish will start to deteriorate. For example, the colour of tuna fish will begin to deteriorate when de-frosted.

At its most general, the present proposals relate to an on-board system for processing fish that includes at least two chilling phases, each of which requires storage of fish at a particular temperature. This two-step chilling process is aimed at improving the quality of fish processed and stored on-board fishing vessels.

According to a first aspect of the invention, there may be provided a method for processing a fish on-board a fishing vessel, the method including an initial (i.e. first) chilling phase, in which the fish is stored at a temperature below 0°C, followed by a second chilling phase in which the fish is stored at a different temperature, also below 0°C. Preferably, the fish is stored at a higher temperature during the second chilling phase than during the initial (i.e. first) chilling phase.

During the first (i.e. initial) chilling phase, the fish is preferably stored at a temperature of between about -1.4 and about -2.0°C, between -1.5 and -1.9°C, between -1.6 and -1.8°C, between -1.65 and -1.75°C, or preferably at about -1.7°C. At temperatures above about -1.7°C, some deterioration in fish quality may start to be seen, while at temperatures above about -1.4°C, this deterioration may start to become unacceptable. This is because it may take too long to reduce the core temperature of the fish to the required standard, resulting in deterioration of quality. At temperatures below about -1.7°C, some reduction in fish quality may start to be seen, while at temperatures below about -2.0°C, this reduction in fish quality may start to become unacceptable due to localised freezing and/or prolonged exposure to low temperatures.

In some instances, localised freezing can produce "rainbow" colours in the flesh of the fish, which may be seen as an indicator of lower quality.

During the second chilling phase, the fish is preferably stored at a temperature of between about -0.8 and about -1.5°C, between -0.9 and -1.4°C, between -1.0 and -1.3°C, between -1.05 and -1.25°C, or preferably between about -1.1 and about -1.2°C. At temperatures above about -1.1°C, some deterioration in fish quality may start to be seen, while at temperatures above about -0.8°C, this deterioration may start to become unacceptable, with deterioration of the fish colour being seen. At temperatures below about -1.2°C, some reduction in fish quality may start to be seen, while at temperatures below about -1.5°C, this reduction in fish quality may start to become unacceptable due to localised freezing and/or prolonged exposure to low temperatures, and in some instances, "rainbow" colours may appear in the flesh, which as mentioned above may be seen as an indicator of lower quality.

The fish are stored in a storage medium, such as seawater or brine, maintained within the specified temperature ranges.

The method may include the step of monitoring the temperature of the storage medium (e.g. seawater) during each step and adjusting the temperature accordingly to ensure that it is maintained within the specified range.

During both chilling phases, the temperature of the storage medium may be monitored and controlled to maintain a reasonably constant temperature. For example, the temperature of the storage medium may be controlled to ensure that it does not fluctuate by more than about +/-1.0°C, more than about +1-0.5°C, more than about +1- 0.4°C, more than about +/-0.3°C, more than about +/-0.2°C or more than about +1-0.1°C. Especially in the second chilling phase, the temperature of the storage medium may be monitored to ensure that it does not fluctuate more than about +/-1.0°C, more than about +/-0.5°C, more than about +/-0.4°C, more than about +/-0.3°C, more than about +/-0.2°C or more than about +/-0.1°C.

The core temperature of the fish may be monitored during the first (i.e. initial) and/or second chilling phases.

During the first chilling phase, the core temperature of the fish may be reduced to between +1.5 and +2.5°C. If the core temperature of the fish is not reduced to within this temperature range within four hours, the fish may be separated from those which do have a core temperature of between +1.5 and +2.5°C and transferred to a separate container for the second chilling phase. These fish may be tagged so that they can be readily identified. The method may also include the step of discarding fish which do not attain a core temperature of between +1.5 and +2.5°C during the first (i.e. initial) chilling phase. If the fish takes longer than four hours to cool down to the desired temperature, the quality of the fish may deteriorate, particularly in terms of colour.

In preferred embodiments, the first chilling phase lasts for less than four hours, for less than three hours, or for between two and three hours.

During the second chilling phase, the core temperature of the fish is preferably reduced further to between -0.5°C and +1.5°C, and more preferably to between 0°C and +1°C.

In this second chilling phase, the fish may be stored within the specified temperature range for up to 21 days, or up to 14 days.

The method may also include the step of stopping the central nervous system of the fish, for example by inserting a wire into a hole in the top of its head, before it enters the first (i.e. initial) chilling phase.

If the fish is alive, its eyes may be covered when performing this operation.

Preferably, the fish are gilled and gutted before the first (i.e. initial) chilling phase. Therefore, the method may also include the steps of gutting and/or gilling the fish before the first (i.e. initial) chilling phase.

The method may include the step of washing the fish, for example in seawater, before the first (i.e. initial) chilling phase.

The method may also include the step of taking and optionally recording the temperature of the fish before the first (i.e. initial) chilling phase.

Each fish preferably enters the first (i.e. initial) chilling phase within 30 minutes, within 25 minutes, within 20 minutes, within 15 minutes, or within 10 minutes of being brought on board the vessel.

The above method may be used for the on-board processing of any type of fish. However, the fish are preferably pelagic fish, such as tuna fish, mahi mahi, mackerel and marlin. These fish are prone to developing high levels of the toxin histamine if their temperature is not tightly regulated during storage. In particular, the method is suitable for use with large pelagic fish, preferably tuna fish.

The above method may be used with any type of fishing vessel, but it is of particular use with small vessels, i.e. those which are less than 200 foot, less than 150 foot, less than 100 foot, less than 90 foot, less than 80 foot, less than 70 foot, less than 60 foot, or less than foot in length.

Following the on-board processing method described above, the fish may be unloaded from the fishing vessel and transferred to ice during transport. The ratio of ice to fish is preferably at least 1:3, at least 1:2 or most preferably at least 1:1.

Due to the careful control of the temperature of the fish (which is supplemented by the reduction in stress of the fish following catching), the on-board processing method described above results in the production of fish with a consistently high quality, especially in terms of their freshness. For example, good quality tuna fish is red, while poor quality tuna fish is brown and the method disclosed herein promotes the production of red tuna fish. This improvement in fish quality is important commercially, as it allows the fish to be sold for a higher price and reduces the number of customer complaints. In addition, due to the higher quality of the fish, the shelf-life of the fish is extended by at least 3 to 4 days. Therefore, fishermen can sell a greater proportion of their fish at higher prices. The method may also reduce the need for histamine testing and other microbiological test requirements, which can lead to a reduction in costs.

According to a second aspect of the invention, there may be provided a method of catching fish using a short multi hooks system. In preferred embodiment, about 100 to about 1000, about 200 to about 900, about 300 to about 800, about 400 to about 700, or about 500 to about 600 hooks are cast at any one time. Using short lines and relatively few hooks allows the line system to be retrieved from the sea quickly and decreases the length of time for which fish are left in the water. This helps to reduce the level of stress experienced by the fish (which in turn improves the quality of the fish caught) and decreases the level of mortality.

According to a third aspect of the invention, there may be provided a recording system for recording information about each individual fish caught using a fishing vessel, the method including the steps of: (i) recording one or more pieces of information about the fish; such as the date of catching the fish, where the fish has been caught, the time the line was put into the water, the time the line started to be pulled out of the water, whether the fish was dead or alive when caught, an estimation of the time of death of the fish, whether the fish has been stressed or damaged, the temperature of the fish before it enters the first (i.e. initial) chilling phase and/or the core temperature of the fish during the first and/or second chilling phases; (ii) assigning a unique identifier to each fish; (iii) marking each fish with said identifier; and (iv) correlating the information recorded in step (i) with the unique identifier. This allows an end user, such as a retailer, to obtain a complete history of what has happened to each fish from catching through to delivery to the end user.

Therefore, the end user will have an indication of the quality of the fish and this allows more accurate grading. For example, seafood factories can judge the quality of the fish more effectively.

The fish may be marked by attaching a tag, which includes the unique identifier, for example a traceability number.

If the information recorded for each individual fish also includes the unique identifier, information about each individual fish can be readily obtained. This can be used to provide an indication of the likely quality of each fish.

The method may include the step of identifying whether the fish is dead or alive when it is caught and optionally recording this information. The fish may then be marked appropriately, for example by attaching a tag to the fish. This tag may be coloured to indicate whether or not the fish was dead or alive when it was caught. The method described herein may include this step of marking the fish.

All the above aspects and embodiments of the invention described above may be combined with each other.

An embodiment of the invention will now be described in detail (but should not be interpreted as limiting the invention) Catching phase Fish are caught using a short multi hooks system with 500 to 600 hooks being cast at any one time. The fish are hauled on-board the fishing vessel and if the fish is alive, its eye is covered and a wire is inserted from its head (by creating a hole in the soft top part of the head) along its nervous system, which is situated along its spinal cord. The same process is carried out for fish which are dead when caught, but in this case, the eye does not need to be covered.

The gills and guts are removed from the fish (i.e. it is gilled and gutted) and it is washed with seawater. The temperature of the fish is then taken and the fish is tagged. If the fish was alive when coming on-board the fishing vessel, a green tag is attached to its tail. If, however, the fish was already dead, a red tag is attached to its tail. A second tag with a traceability number is also attached to the fish.

For each fish, the following information is recorded: the date of catching the fish, where the fish has been caught, the time the line was put into the water, the time the line started to be pulled out of the water, whether the fish was dead or alive when caught, an estimation of the time of death, whether the fish has been stressed or damaged, and the temperature of the fish after it has been gilled and gutted.

Initial (i.e. first) chilling phase The fish are transferred into a first chilling chamber.

This should be done within 10 minutes of the fish being brought on-board the fishing vessel. Therefore, all the preceding steps should be completed with 10 minutes of the fish being brought on-board the fishing vessel. This first chilling chamber contains seawater, which is maintained at a temperature of -1.7°C. The fish are stored in the first chilling chamber for a period of 2 to 3 hours, or until the core temperature of the fish is reduced to between 1.5°C and 2.5°C. The maximum length of time the fish should be stored at this temperature in the first chilling chamber is 4 hours.

The temperature of the fish is recorded before transferring it to the second chilling chamber. If the core temperature of the fish has not been reduced to between 1.5°C and 2.5°C during the first chilling phase, the fish is tagged with a tag indicating "Temperature failure" and is transferred to a separate chamber where the water temperature is between -1.1°C and -1.2°C. Thus, fish whose core temperature has not been reduced to between 1.5°C and 2.5°C are separated from the fish whose core temperature has been reduced to the required temperature.

Second chilling phase Once the core temperature of the fish has been reduced to between 1.5°C and 2.5°C, the fish is transferred to a second chilling chamber which contains seawater maintained at a temperature of between -1.1°C and -1.2°C.

The maximum temperature fluctuation of the seawater should not be more than +1-0.1°C. Fish can be stored in this second chilling tank for up to 14 days.

Unloading fish The fish are transferred immediately to a refrigerated lorry where they are transported on ice, with a ratio of at least 1:1 ice to fish. The temperature of random fish is recorded. The fish are then transferred to a factory where both the temperature and the quality of the fish are monitored and traceability information is kept. y

Claims

Claims 1. A method for processing a fish on-board a fishing vessel, the method including: (i) a first chilling phase, in which the fish is stored at a temperature below 0°C, followed by (ii) a second chilling phase in which the fish is stored at a different temperature, also below 0°C.
2. A method according to claim 1, wherein the fish is stored at a higher temperature during the second chilling phase than during the first chilling phase.
3. A method according to claim 1 or 2, wherein the fish is stored at a temperature of between about -1.4 and about -2.0 °C during the first chilling phase.
4. A method according to any one of the preceding claims, wherein the first chilling phase lasts for less than four hours.
5. A method according to any one of the preceding claims, wherein the fish is stored at a temperature of between about -0.8 and about -1.5°C during the second chilling . 25 phase.***.*. S *
6. A method according to any one of the preceding claims, wherein the fish is stored within the specified temperature range during the second chilling phase for up to 21. days.
7. A method according to any one of the preceding claims, wherein the fish is stored in seawater or brine, which is maintained within the specified temperature ranges.
8. A method according to any one of the preceding claims, wherein the core temperature of the fish is monitored during the first and/or second chilling phases.
9. A method according to claim 8, wherein the core temperature of the fish is reduced to between +1.5 and +2.5°C during the first chilling phase.
10. A method according to any one of the preceding claims, wherein the fish is discarded if it has not attained a core temperature of between +1.5 and +2.5°C during the first chilling phase.
11. A method according to any one of the preceding claims, wherein the core temperature of the fish is reduced to between -0.5°C and +1.5°C during the second chilling phase.
12. A method according to any one of the preceding claims, wherein the method includes the step of stopping 25 the central nervous system of the fish, and optionally **..gutting and/or gilling the fish, before it enters the first chilling phase. * ** * * * ***
13. A method according to any one of the preceding claims, wherein the fish enters the first chilling phase within 30 minutes of being brought on board the vessel.
14. A method according to any one of the preceding claims, wherein the fish is a pelagic fish.
15. A method according to claim 14, wherein the fish is a tuna fish.
16. A recording system for recording information about each individual fish caught by a fishing vessel, the method including the steps of: (i) recording one or more pieces of information about the fish; (ii) assigning a unique identifier to each fish; (iii) marking each fish with said identifier; and (iv) correlating the information recorded in step (i) with the unique identifier.
17. A recording system according to claim 39, wherein the one or more pieces of information recorded about the fish in step (i) include one of more of: the date of catching the fish; where the fish has been caught; the time the line was put into the water; the time the line started to be pulled out of the water; whether the fish was dead or alive when landed on the vessel; an estimation of the * *o. * *time of death of the fish; whether the fish has been *. 25 stressed or damaged; the core temperature of the fish **** before it entered the first chilling phase; and/or the core temperature of the fish during the first and/or second chilling phases. * *
18. A recording system according to claim 17, wherein the one or more pieces of information recorded about the fish in step (i) includes whether it was dead or alive when it was landed on the vesssel.
19. A recording system according to claim 43, wherein the fish is marked according to whether it was dead or alive when it was landed on the vesssel.
20. A method for processing a fish on-board a fishing vessel, the method comprising performing a method according to any one of claims 1 to 15, and also utilising a recording system according to any one of claims 16 to 19. * * * ** * *.*. * S I.,. * S *5SSS * S * S. Sc. S.. ,SS.....S