It is also indicated by elevated histamine levels in the muscle tissue. Histamine forms postmortem by bacterial action on the amino acid, L-histidine.
Histamine is heat-stable and survives thermal processing.
It is therefore a useful indicator of decomposition in scombroid and certain other fish because odors that normally signal decomposition to the organoleptic analyst may be modified, reduced, or eliminated by thermal processing. In addition to being an indicator of decomposition, when ingested at sufficiently high levels histamine causes scombroid poisoning. Cases of scombroid poisoning have been traced to the consumption of raw, frozen, and canned tuna and raw and frozen mahi-mahi. Scombridae and Scomberesocidae are implicated in instances of histamine poisoning derived from decomposition in these fish. Tuna and mackerel are most frequently involved in instances of histamine poisoning, but this fact may be partly the result of the rate of consumption of these species worldwide.