"Odd" flavor in some white fish - how to predict?

I have had this problem and thought it was the taste of tin-foil that I used to rolled up and put into the belly of the fish to stand it up in the oven. So, I was very interested to hear an interviewer on the radio 3RRR in melbourne, talking to a chef who mentioned fish, like Snapper, are susceptible to that metalic taste if they are caught and die too slowly. The slower they take to die, the more stress the fish goes through and the stress hormone accumulates in the flesh particularly around the belly. I think they said a pinker snapper is better than a pale one for taste.

I've noticed the same taste in cod that I buy at Kroger (surprising since Kroger is fairly high quality when it comes to most of their food). Perhaps mine is an age issue as I buy it when it's marked down for quicker sale. It doesn't seem to matter how I prepare/cook the fish.

It is probably the process of cutting and cleaning the fish. It must be cut in such a way that the stomach part of the fish which needs to be cleaned must come out easily and completely without spilling over. I mean to say that the unwanted stuff inside the stomach must be cleaned without smashing it. Once it gets smashed the bitter tasting substance in the stomach spreads where ever it touches. And then it cannot be cleaned by any means. The same is reflected on to the flesh pieces after cooking the fish making it difficult to eat. My grandmother used to be always cautious about it when ever fish is cleaned and over the period I experienced that this is the cause of bitter taste in fish.

Phenylthiocarbamide would be my guess. Some people can taste it, and some people cannot, and that is genetical. It is extremely bitter if you can taste it. We used it in social conformity experiments in psychology: if you dont taste it, but everyone else, you conform or not etc...

Now, how that stuff gets into your fish... I remember something about it inhibiting pigmentation... so maybe it used to farm very white fish? test of this would be that you would never have this with wild fish or with coloured fish like salmon... assuming that colour comes from pigmentation, i am no biologist..

I had this problem about 25% of the time with Trader Joe's white fish. Also, certian beef at TJs. What I did was stop buying those particular pieces of meat from those vendors and try other stores. This method has reduced my finding bad tasting fish or meat to about 10% of the time. It also has led me to liking other meats and fishes.

I think you are looking for some technique that can be applied right then and there if you have the meat in hand. Unfortunately, this seems unlikely. Try other stores is my best answer...

My guess is this has something to do with the freshness of your fish. Read a little bit of McGee on the subject. I don't guess there is a way of predicting it.

Saltwater critters collect iodine in their flesh through the food they eat. Plankton and kelp contain iodine. So, anything that eats that or eats something that eats it can build up quite a taste in their flesh. Try soaking the filet in milk for about 30 minutes before you cook it. The fishy smell and iodine taste will be reduced quite a bit.

I find that too i liken it to an a disinfectant taste. I saw a show one time that talked about how they use disinfectant to clean tanks at fish farms. To keep algae from growing Thats what the taste rends me of and i find it in cheaper priced fish. The more expensive priced does not have that taste. Makes me want to puke. I also get wild caught for sure.

My guess is the fish is contaminated. I just had cod that was bitter as hell and I cooked it plain. Its not supposed to taste this way. Maybe they are adding another preservative. Most of the people who think they are allergic to shrimp are not. They are allergic to sulfites which they put on the shrimp when they catch it to preserve it. A large percentage of the population is allergic to sulfites.