Method and device for delaying rigor mortis in fish
A method and an apparatus for bringing fish to an under-cooled state by a sub-chilling process before processing, which prolongs rigor and allows processing of the fish in rigor providing better quality fish products.
1. A method for delaying rigor mortis in slaughtered fish, the method comprising:
a) receiving slaughtered fish;
b) bringing the slaughtered fish to an under-cooled state in at least one container comprising
placing the slaughtered fish in a first solution having a salt concentration in the range from 0.1 to 10% and a temperature in the range from +1 to −3° C. wherein the salt concentration and the temperature of the first solution is based on the fish species; and
transferring the slaughtered fish to a second solution having a salt concentration in the range from 1% to 20% and a temperature in the range from −1 to −12° C.;
wherein:
i) the salt concentration of the first and second solution is set and a temperature of the first and second solution is maintained such that the temperature is higher than the freezing point of the first and second solution,
ii) providing substantially continuous movement of the slaughtered fish in the first and the second solution,
iii) maintaining the ratio of the first and the second solution and slaughtered fish such that the volume of the first solution is greater than 50% of the total volume of the fish and the first solution and the volume of the second solution is greater than 50% of the total volume of the fish and the second solution,
c) transferring the slaughtered fish to a transport or storage container, where the temperature in the transport container, the storage container, or both is maintained below 0° C.; and
d) increasing the transportation or storage time and/or the shelf-life of the slaughtered fish by delaying rigor mortis in the slaughtered fish.
2. The method according to claim 1 , wherein in step (b)(i) the temperature of the first solution and the second solution is at least about 0.5° C. higher than the freezing point of the respective first solution and the second solution.
3. The method according to claim 1 , wherein in step (b)(i) the temperature of the first solution and the second solution is at least about 1.0° C. higher than the freezing point of the respective first solution and the second solution.
4. The method according to claim 1 , wherein the fish is pre-cooled to a temperature of below about 6° C., gutted and/or bled before step b).
5. The method according to claim 1 , wherein the salt concentration and the temperature of the second solution is based on the fish species.
6. The method according to claim 1 , wherein the time period of bringing the fish to an under-cooled state is based at least in part on the size and the quantity of the fish being cooled.
7. The method according to claim 1 , wherein the at least one container is an elongated cylindrical or semi-cylindrical tank and comprises a spiral shaped blade mounted on a rotation axis to convey the objects along the length of the tank.
8. The method according to claim 7 , wherein the rotation of the spiral shaped blade provides the movement of the fish in the at least one container.
9. The method according to claim 1 , wherein the volume of the first solution and the second solution in step (b) (iii) is between 55% and 75% of the total volume of fish and the respective first solution and second solution.
10. The method according to claim 1 , wherein the fish is maintained at between −0.5 and −2° C. during step c).
11. The method according to claim 10 , wherein the fish is maintained at −1° C. in step c).
12. The method according to claim 1 , wherein in step (b)(i) the temperature of the first solution and the second solution is at least about 1.5° C. higher than the freezing point of the respective first and the second solution.
13. The method according to claim 1 , wherein the fish is pre-cooled to a temperature of below about 4° C., gutted and/or bled before step b).
14. The method of according to claim 1 , wherein the salt concentration and the temperature of the first solution, the second solution or both is based on the fat content of the fish.