When fish die, stopping the supply of ATP (Adenosine Triphosphate), the source of muscle energy, the muscle fibers gradually harden. As time passes, it gently dissolves and the ATP breaks down, changing into umami components due to self-digestion.
ATP is broken down as follows, but in living fish, only the reaction up to AMP occurs. Once broken down to AMP, it is regenerated as ATP.
ATP→Adenosine diphosphate (ADP)→Adenosine monophosphate (AMP)→inosinic acid (IMP)→hypoxanthine riboside (HxR)→Hypoxanthine (Hx)
In fish after death, inosine monophosphate (IMP) is produced from AMP by an enzyme called adenosine deaminase (ADA). This is called maturing. Inosine monophosphate is not found in cells immediately after death. Maturation is required for the production of inosine monophosphate. If it goes further, it will go bad and HxR (inosine) and Hx (hypoxanthine) will be produced.
The umami created by self-digestion of ATP is “maturing (Jukusei)” and the process after that is “rotting.”
We hope this information will be helpful.
Revision date: March 17, 2025
Share this article