WO2003099026A1

WO2003099026A1 - Processing fish

Info

Publication number: WO2003099026A1
Application number: PCT/NZ2003/000097
Authority: WO
Inventors: Trevor James Gould
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-05-28
Filing date: 2003-05-20
Publication date: 2003-12-04
Anticipated expiration: 2004-11-28
Also published as: GB2405570B; NZ519235A; DK200401937A; AU2003228175B2; AU2003228175A1; GB0427690D0; GB2405570A

Abstract

A method of removing blood from fish which involves killing the fish, removing its head and then inserting a jet of water into a vein or artery and circulating the water through the fish's circulatory system to flush the blood out of the fish.

Description

Title: Processing Fish

Technical Field

The present invention relates to a method of processing fish and apparatus therefor so as to ensure that blood is completely, Or almost completely, removed from the flesh.

The method and apparatus of the present invention have been developed especially for salmon, and will therefore be described with particular reference to that application. However, it will be appreciated that the method and apparatus of the present invention also would be suitable for use with other fish, especially fish which are to be sold raw or which are to be smoked.

Background Art Residual blood in the flesh of a fish gives an unpleasant appearance to the raw or smoked fish. For example, when fish is smoked, any residual blood in the veins turns black, leaving black spots visible on the surface of the fish. At present, blood is blown away from the surface of the fish using water hoses; this method is ineffective, wastes water, and tends to damage the flesh, without removing the blood from within the flesh.

Disclosure of Invention

It is therefore an object of the present invention to provide a method and apparatus for thoroughly removing blood from fish, without unduly increasing the cost of processing or damaging the fish.

According to one aspect, the present invention provides a method of removing blood from fish, including the steps of:- a) killing the fish; b) removing the head of the fish; c) inserting a jet of water into a vein or artery of the fish and circulating the water through the fish's circulatory system to flush substantially all of the blood from the fish.

Preferably, the jet of water is inserted into the caudal vein of the fish. However, it is believed that other veins or arteries could be used instead.

Preferably also, the jet of water is inserted into the vein or artery by means of a hollow needle (preferably stainless steel) one end of which is open and is inserted into the vein and the other end of which is connected to a supply of potable water.

According to another aspect of the present invention, there is provided apparatus for processing fish, including a source of pressurised water, a feed pipe for the pressurised water from the source to a hollow needle, the needle being adapted to be inserted into a vein or artery of the fish, whereby to flush out blood or other contaminants from the vein or artery.

Brief Description of the Drawings

By way of example only, a preferred embodiment of the present invention is described in detail with reference to the accompanying drawing and flow chart, in which :-

Figure 1 is a section in a vertical plane through fish processing apparatus, according to the invention, and Figure 2 is a flow chart.

Best Mode of Carrying Out the Invention

Referring to the flow chart, in step 1 the fish to be processed is killed. In step 2 the head of the fish is removed. Both of the steps may be carried out in any suitable known manner.

In step 3, a hollow stainless steel needle 10 with one tip 11 rounded is connected to a pressurised supply 12 of potable water. The water supply 12 is connected to the needle 10 through a hose 13 attached either to the other end of the needle 10 or to an inlet formed along the shaft of the needle 10.

Assuming that the fish to be processed is salmon, it has been found that the preferred dimensions of the stainless steel needle 10 are:-

extemal diameter 3-4 mm; internal diameter 1 -1.5 mm; length 50-75 mm.

Further, the water flow should be supplied by the needle 10 at a pressure sufficient to squirt a jet of water a maximum horizontal distance of 1.85 m from the rounded end 11 of the needle 10. Typically, the water pressure is 2-4 psi.

In steps 4 and 5, the rounded end 11 of the needle 10 is gently inserted into the caudal vein of the salmon, so that the water is circulated around the salmon's circulatory system, flushing out substantially all of the blood. This takes 10-60 seconds, generally about 30 seconds.

The above described method does not damage the flesh of the fish in any way and results in clean flesh of good appearance.

The water used in steps 4 and 5 may have additives in it, (e.g. salt or other preservatives, flavourings) if desired. In this case, it may be desirable to use a very low pressure, for a much longer period (e.g. up to 12 hours).

After this treatment, the fish can be smoked or stored or further processed in known manner.

It is believed that the method of this invention may also remove lactates, (lactic acid and its salts) and other metabolites from the flesh of the fish, and thus improve its quality.

In Figure 1 seven of the needles 10 are connected to a rigid or flexible manifold pipe 14 connected to the hose 13. The pressurised supply 12 includes a vessel 15, typically of 100 litres capacity having an air tight lid 16 and an openable drain 17 at the bottom thereof. The supply 12 is conveniently carried on wheels 18, mounted on an axle or frame 19 on which the supply 12 may be moved around the floor. The water from the vessel 15 passes through a filter 20 and a rigid pipe 21 to the hose 13. An electrically driven air pump 22 is used to pressurise the vessel 15 and the water therein to a pressure of 2 to 4 psi. A mixing device 23 driven by an air or electric motor is also mounted inside the vessel 15 to ensure that any additives to the potable water remain evenly in suspension. If preferred, the air pump 22 can be omitted and a water pump can be used to draw the water through the filter 20 and feed it to the pipe 21.

Although the invention has been described with seven needles 10, a single needle 10 or any other suitable number can be used.

Claims

1. A method of removing blood from fish, including the steps of:- a) killing the fish; b) removing the head of the fish; c) inserting a jet of water into a vein or artery of the fish and circulating the water through the fish's circulatory system to flush substantially all of the blood from the fish.

A method according to claim 1 in which the jet of water is inserted into a caudal vein of the fish.

3. A method according to claim 1 or 2 in which the jet of water is inserted into the vein or artery by means of a hollow needle one end of which is open and is inserted into the vein and the other end of which is connected to a supply of potable water.

4. Apparatus for processing fish, including a source of pressurised water, a feed pipe for the pressurised water from the source to a hollow needle, the needle being adapted to be inserted into a vein or artery of the fish, whereby to flush out blood or other contaminants from the vein or artery.

5. Apparatus, according to claim 4, in which the needle has a rounded end.

6. Apparatus according to claim 4 or 5 in which the source of pressurised water includes a closed container in which the water is pressurized by pressurised air fed into the closed container to displace water therefrom.

7. Apparatus according to claim 4 or 5 in which the source of pressurised water includes a container for the water and a pump connected to the container to draw water therefrom and to discharge it to the needle at raised pressure.