Can fish stock be left simmering for a long time without damaging the flavor?

I'm not sure about a glue flavor (I kicked the habit in kindergarten ), but I made a stock with king mackerel bits, including the head and tail fin and it made an amazing base for gumbo. Be prepared for the smell to linger a bit though.

I always try to simmer my stock for a long period of time and have never gotten a bad taste. I have never heard about the "glue" taste but the broth that is extracted from the bones is a very tasty broth just like bone broth from meat.

I am a European trained chef. This is a very interesting question and there are quite a few answers. In my opinion and experience, the simmer time of a good fish stock is 100% based on the type of fish bones that you are developing the stock with. I remember asking the question many times on my travels through Europe and North Africa. I will share my preferred methods for a few species of fish.

1. Turbot, 20 minutes after it comes to the boil, bay leaf only in the stock.
2. Dover Sole, a full mirapoix, simmer for 30 minutes.
3. Salmon, bring to boil and shut off, a full mirapoix is needed
4. Northern Hake, 45 minutes full mirapoix
5. John Dory, 45 minutes full mirapoix, white wine may be added if desired.

I hope that helps you out. Regards.

Michael

From experience I cannot say because I never simmer stock beyond 20 minutes.

I follow this rule because nearly every master chef(no not the television show) I've read says so. Michel Roux states that in his book Sauces. And James Peterson, a former chemist, states it in his book Sauces, and he teaches at the French Culinary Institute.

Michel Roux makes the statement that for certain bones, less time is better.

Jennifer McLagan, in her book Bones, only states that flat fish bones are preferable because of their higher level of gelatin. As regards to time, she only states that fish bones "yield their essence quickly."

One would think that James Peterson would have commented on the chemistry of this, but he doesn't, despite talking at length of the various chemicals released when making veal and beef broth.

If Jennifer's comment on the issue gives us any clue, it would lead us to hypothesize that because fish bones yield their essence rather quickly, they must be delicate and probably burn or change after those 30 to 40 minutes of continuous heat.

We do know that stocks expire, so we might conclude that fish stocks are more susceptible to time and also to heat.