Why is cod rubbery?

Chef's answer
Even fresh cod is naturally pretty rubbery anyways but you can mitigate it by cooking it certain ways. Rubbery means it was overcooked. "Slow and low" is the way to go. Preferably covered if you're frying it up in a skillet (I'd cook it with butter, and some flour and salt and pepper)..
Frequently asked Questions 🎓
Pat scallops dry with paper towels. Season generously with Kosher salt and freshly ground black pepper. Place on a plate.
Scallops should be super easy to cook at home, but as many who have tried can attest, they often turn rubbery on the inside for no apparent reason. ... True to their name, wet scallops exude more moisture when they're cooking, messing up the searing process and leaving you with an icky, rubbery dinner.
Why does mutton turn elastic after cooking? ... Cooking mutton, or just about any other food containing proteins, causes the protein chains to 'unravel', a.k.a. denaturing. This causes the proteins, and hence the food, to become softer and suitable for chewing and digesting..
Lobster meat turns rubbery and tough when overcooked. Always keep a careful eye when cooking lobster tails, but make sure the meat reaches at least 135 degrees..
As far as it being rubbery and tough that sounds like the fish was overcooked. Try cooking it much less and you should be OK. I'd venture to say that the filets still had skin on them. The skin will shrink at a different rate than the flesh, causing curling.
Overcooking the Meat Most inexperienced cooks leave lobsters in the pot for far too long, resulting in dry, rubbery meat. Lobster meat is fully cooked when it reaches 140?..
Corned beef must be heated at above 250 degrees Fahrenheit, so that the tough, stringy meat will separate. Simmering it in this manner can revive its taste and texture. Let the corned beef simmer for about 30 minutes. This finishes the cooking process and makes it tender.
A few more cooking questions 📍