Planning a fishing trip this summer? The Nofima researchers have some excellent advice for ensuring that your catch is of the best possible quality.
You should apply the same rules as the professionals if you want to preserve your catch as well as possible, whether you are planning a fishing trip in mountain lakes or rivers or a magical trip on the fjords during the summer holidays. Gently remove the fish from the water, bleed it quickly, keep it cold and avoid blood collecting around the fish.
Nofima seafood scientists have carried out a series of trials on fresh fish and documented what it takes to guarantee the highest quality. The work has been carried out on behalf of the fishing industry, in collaboration with the Norwegian Fishermen’s Sales Organisation and supported with funding from the Fishery and Aquaculture Industry Research Fund (FHF).
Here are some of the most important findings, which will also benefit amateur fishermen:
If you are on a longer fishing trip and the weather is warm, you should consider how to keep the fish as cool as possible. In boats it might be a good idea to bring a fish box or similar with cold water for storing fish.
Use a ladle to replace the water regularly in order to keep it cold.
A live fish on board a boat or on land will get stressed, and the longer it sits before being bled, the more blood will seep into the flesh. It is therefore important to bleed the fish; that is, to cut the blood vessels that go to the heart as quickly as possible. Researchers recommend bleeding the fish and cooling it down to four degrees immediately after it has been brought on board the boat or on land to ensure the best quality meat.
For reasons of fish welfare the fish should be anaesthetised or killed by a blow to the head before it is bled.
Following bleeding, the fish should be left to bleed out in cold water for at least 30 minutes before being further chilled down to zero degrees. It is best to lay the fish straight onto ice as soon as it has bled out. but this option is rarely available to the casual fisherman.
However, it is worth knowing that if the fish is lying in bloody water at temperatures of up to ten degrees for a long time after bleeding, it will have a detrimental effect on both smell and appearance. High temperatures will very quickly start the fish’s decomposition process.
Avoid processing the fish while it is experiencing rigor mortis, i.e. when it has stiffened up following death. Strong rigor mortis results in the fish becoming very hard and stiff and taking on an arched shape, making it easier to cut it up incorrectly, which in turn tears the muscle physically, leading to fillet gaping. In addition, the trimming of fillets from a fish in rigor mortis is challenging since the muscle is very hard and it is difficult to remove pin bones.
If you are intending to fillet the fish, it is recommended that you do so before rigor mortis sets in or after it has passed.
The period before the fish becomes stiff – the pre-rigor mortis period – can vary in duration from less than two hours to over a day after death. This is dependent on several factors such as how the fish is handled after it has been caught, fish meat temperature and species. Haddock, for example, is easily stressed, and strong rigor mortis can quickly set in.
The more gentle the handling of the fish before it is killed, and the quicker it is cooled down to four degrees – the longer it will take before rigor mortis sets in and will have less of an effect on the fish. Rigor mortis stops eventually, but it takes time. Cod may remain stiff for up to two or three days.
It can actually be difficult to taste the difference between fresh and frozen fish fillets from the same raw material if the fish has been handled optimally prior to freezing, bagged or packaged, quickly frozen and thawed correctly.
When you thaw fillets that have been frozen before the fish becomes stiff (pre-rigor), the phenomenon of “thawing rigor” may occur if the fish has been stored in the freezer (at approximately 18ºC) for less than a month.
Thawing rigor can be a problem if the fillet is thawed too quickly at a high temperature. This results in the fillet contracting and shedding water which makes the muscle less juicy. However, it can be very difficult to notice the difference between fillets that have been frozen pre-rigor mortis and fillets that have been frozen down while in full rigor mortis.
If you need to make a quick fish supper, you can remove the fillets from the freezer and thaw them under cold running water.
If you want to make saltfish from your catch, our scientists have the following advice: Do not salt the fish when freshly caught, wait until rigor mortis has passed. Pre-rigor mortis fillets rapidly experience an unusually strong state of rigor mortis when salted. The muscle becomes very hard and does not absorb salt as quickly as post-rigor mortis fillets. This means that it is difficult to achieve even salt distribution and the desired salt level for the fillet during light salting.
During full salting, pre-rigor salted cod fillets can develop a very hard texture, which can result in up to ten per cent less yield after rehydration than full or post-rigor mortis produced fillets. They may also develop a deeper yellow colour than fillets that have been salted post-rigor mortis.
If you wish to dry the fish, you should use the freshest possible raw material. The fish should be properly gutted and have its head removed with the backbone intact. Pre-rigor mortis raw material will give a better colour and consistency than post-rigor mortis fish.
With respect to stockfish without the backbone, be aware that any shrinkage can result in a ridged and cracked surface.
All that remains is to wish you a good haul for your fishing trip. If nothing else, have fun.
Have a great summer and good luck!
Did you know?
- Freshly caught cod which is kept at a temperature of ten degrees for a day before being chilled to zero degrees will have a shelf life that is four days shorter than if it had been chilled immediately.
- The reason why the fish fillet shrinks when you cook it just after it has been caught is that the fillet has not yet undergone rigor mortis and is not experiencing any mechanical resistance from the skeleton. The shape of the fillet therefore becomes shorter and wider when fresh.