Most sea creatures contain a molecule called trimethylamine oxide (TMAO) in their flesh. The molecule helps balance their internal salt levels against the high concentration of salt in the water. It also helps with stabilizing proteins.
TMAO will break down (oxidize) when in contact with oxygen in the air. The oxidized chemicals produce the fishy smell for seafood that has been left out for too long and has spoiled.
Note that freshwater fish have much lower concentrations of TMAO so they don’t smell as strongly when left out.
Most sea creatures contain a molecule called trimethylamine oxide (TMAO) in their flesh. The molecule helps balance their internal salt levels against the high concentration of salt in the water. It also helps with stabilizing proteins.
TMAO will break down (oxidize) when in contact with oxygen in the air. The oxidized chemicals produce the fishy smell for seafood that has been left out for too long and has spoiled.
Note that freshwater fish have much lower concentrations of TMAO so they don’t smell as strongly when left out.
Adding: a lot of the time, seafood have been killed by suffocating due to being out of water. Suffocating fish panic and flop around, which causes a buildup of stress chemicals that, combined with the blood not being drained, make the fish spoil faster.
The ike jime method of killing fish kills them instantly and drains their blood, meaning they dont flop around and cause the stress chemicals to build up, causing then to stay fresh far longer, and even allows for aging to build up a nice umami flavour. It’s not used often for fish caught en masse because it involves a lot of manual work, so ike jime slaughtered fish tends to be quite expensive.
Adding: a lot of the time, seafood have been killed by suffocating due to being out of water. Suffocating fish panic and flop around, which causes a buildup of stress chemicals that, combined with the blood not being drained, make the fish spoil faster.
The ike jime method of killing fish kills them instantly and drains their blood, meaning they dont flop around and cause the stress chemicals to build up, causing then to stay fresh far longer, and even allows for aging to build up a nice umami flavour. It’s not used often for fish caught en masse because it involves a lot of manual work, so ike jime slaughtered fish tends to be quite expensive.
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