Why do fish eyes go milky white in ice slurry

[Anne-T-Dote]

Sorry if this thread has done the rounds before, but I was wondering:

I've seen on the weekend TV fishing shows when the TV Seafood Chefs are in the fish markets showing the viewers how to pick the difference between a "fresh" fish and one that is a bit old. The tell-tale signs being that the older fish will have milky white eyes, where as the fresh fish will have clear eyes.

Well, I bleed ALL fish that I keep and put them straight into a salt water ice slurry. I've always thought that there's no better way to look after fish for the few hours between the time they're caught and the time they reach the filleting table (the same day as being caught). But maybe I'm wrong as I've noticed that 9 times out of 10 the eyes of my fish have already started to turn a bit milky white when I start filleting. Are milky eyes a sign that the fish has been frozen or partially frozen? Maybe the ice slurry is actually TOO cold (since it is below zero with the salt water 'n all)??

Does anyone experience the same thing or does anyone have any suggestions??

[Cruiser]

Yes, I have had the same experience. And I don't think it's from freezing or getting them too cold as we usually just have frozen water in soft drink bottles in the kill tank.

I see it in some fish species more than others. For example Red Emporer seem to be the worst in this regard. Pity, cause it spoils the photos having that milky white eye showing through.

Chris.

[finga64]

might be the same reason that our skin goes white after it's been in the water for too long. :-?
Anybody know why???

[Anne-T-Dote]

Yeah Chris - I know what you mean about spoiling the photos.

It's also a bummer when you go to the effort to scale and gut some for friends / family / neighbours to bake whole and they say something like "Hmmm, doesn't look too fresh, just look at the eyes.." You feel you have done your very best to keep them in prime condition and they go and deflate you by saying something like that.

Also makes me wonder whether the fish in the markets with CLEAR eyes actually haven't been looked after that well at all - maybe IT IS the cold brine that turns the eyes milky white and the fish with CLEAR eyes have just been thrown into a dry nally bin and not chilled??

I dunno... ::) #:-?

Any scientists out there??

[Volvo]

No scientist but here's my two bobs worth :)..Once upon a time ago i used to gill n gut all my fish shortly after capture n then straight on or should i say covered in ice.
Nowadays they go straight into an ice slurry emediatly upon capture and soon as the fish have set and have a few in the slurry they get transfered to the main ice box again under ice .
Cant sayz ive ever had the eyes on my fish go milky or white after bein on the ice??, even after getting home and filletting the fish still looks like they dont need contacts ey :)..
What i have experienced though if the fish aint covered in ice especially under our type of climate up here is that the fillets kinda go flakey sometimes and dont quite know whether the cause of this is due to the lack of ice contact or something to do with the fish??..
Maybe if the fish has stayed out of the ice slurry and only in a kill bin for too long a time that may cause the milkiness in the eyes??..
Sorry if i aint been too much help but just thought ide pass on how i handle me fish..
Cheers

[Volvo]

PS, when i say ice slurry i mean ice slurry ;), ie 8-10kg's of cured ice in an ice box,just enough sea water to have an actual slurry and lid back on the ice box.
Brine or slurry gets so cold you cant place the mits in fer too long i can assure ya :)..
Spend so much on Boat, Fuel, bait n asscociated expences i do want my fish in top nik when i get em home ey, what a few more bob spent here n there?? :)..
Temp of slurry drops out then time to make another batch up if staying out that long..
Cheers

[revs57]

G'day Macca,

Well I'm no scientist but I know from experience that when you mix a slurry of salt water and ice it will lower the temperature enough to freeze water and bring fillets to the chill too, cant be a bad thing when you're out fishing to have fresh fish bled off then chilled in a salt slurry to keep the flesh nice and firm. Milky eyes???? Never really taken much notice...may make a difference for fish bought at the co-op or supermarket but I reacon pulling fresh fish down in a salt slurry is the only way to go

Can't comment on the reporters info....

Cheers

Rhys

[1810B]

fresh water ice with salt added and sea water will get below zero. My left leg still has the scars of the ice slurrey blister burn from when I overdid it with the salt and had to get into the slurrey, Cold burnt within seconds above the divers shoue and no wet suit on. Tuna boats that installed sea water ice machines experienced freezing of tuna flesh through extra low temperature of that ice then sea water added. Is better to just add sea water to the fresh water ice. About 18 years ago did a lot of work with Japenses fish buyer for better productand result was fish caught, spiked or relevant kill method, sraight into ice slurrey ensuring the fish is straight and preferably on its back. some ice into gill area. After that no fish were cleaned on capture but sometimes 5 days later for snapper,red throat,trout,etc and all mackeral and bar cod. Cleaned at end of the trip. Easier cleaning and colour still as the day they were caught and eyes as bright as buttons. Note fish left in slurrey for up to 12 hours then iced.

[DICER]

Have you ever wondered why eggs turn white after being cooked? I believe it is the same mechanism acting to turn the fishes eyes to a white haze. It is to do with proteins becoming denatured (unfolded, misfolded or scrambled).

Think of a protein as being a string of amino acid molecules, then being wrapped and folded into the correct shape to perform a special function. What happens when the protein is heated or the temperature lowered is that the protein becomes unstable and unable to be correctly folded. Protein shapes are very important for function.

Albumin which is the main protein in eggs goes from being in a clear transparent form to going into a white cross-linked mass upon heating. Similarly proteins in the eyes of fish will either precipitate or unfold cause a similar reaction to that seen in eggs, when either treated in the cold or cooked in a pan.

Water logged tissue is another completely different issue and is not related to protein denaturing (incorrect folding or unfolding).