Am I still overcooking whitebait, how to prevent it?

I have had a problem where I am constantly overcooking whitebait.

In light of previous answers relating to the same issue, recently I have started to place the whitebait in the water, put a thermometer in the water and when the water reaches 45c, I just remove the pot from the stove. This way, the water may at most rise up to 50c and the fish will end up being around that immersed in water. Note I cant check the fish temperture(only the water) since the fish are too small and I believe most thermometers can't give an accurate read since they dont go deep enough into fish.

Unfortunately I notice that, despite my current method, saturated fat or liquid is relased from the fish into the water. Fish releases its fat/juices at 55-60c so since my water is not at that temperature(i.e. it's at 45-50c at most) this should not be happening and hence there should be no fat/juice release\overcooking.

Can anyone think why this might be happening and how I can fix it? My guess is that when cooking the temperature at the bottom of the pot is that hottest e.g. perhaps over 55c, this causes the bottom of the fish to overcook and go into the water.

What do you think and how can I prevent this which for me is overcooking since I want the fish to be 55 at most i.e. fat should not break down or juices shouldnt release.

Best Answer

Fat/juice release and overcooking are not the same thing. Release of liquid (including a bit of fat/oil) is not just a sign of overcooking. Sous vide fish, even down in the 110-125F (43-52C) range, releases liquid, and it's definitely not overcooked.

The overcooked fish smell is not just because of fat, and does not happen with short cooking at 50-55C. If you're smelling something at those temperatures, I suspect it's just fish, not overcooked fish. (It is possible that the bottom of your pot is perhaps 5-10C warmer, I suppose, but that'd be easily mitigated by stirring, and I don't think it'd cause instant overcooking even if there is a 5-10C gradient.)

If you don't actually care about overcooking, and it's just that you don't want anything to be released, then you don't want any sort of cooked fish. I guess you might have to eat sashimi.

As for your claims about what temperatures release what, I don't think that there is any absolute "fat breaks down" temperature. There are certainly kinds of fat which will break down at a temperature-dependent rate, which it sounds like is what you read about. Things generally aren't totally black and white: to totally make up numbers, the reaction rate might be nearly zero at 40C, slow at 45C, moderate at 50C, fast at 55C, and level off from there. That might get summarized as fat beving released at 50C, or 55C depending on perspective. There's also perhaps fat/oil that's just readily available, and could get "released" simply by putting the fish in room temperature water for a bit.

The same is even more true for water and water-soluble things. Liquid and flavors can be released quite easily.