Low-Temperature Production of Urocanic Acid by Spoilage Bacteria Isolated from Mahimahi (Coryphaena hippurus)

Urocanic acid production was studied in 166 bacterial cultures isolated from mahimahi which had been stored for 14 days on ice in seawater. After 4 days of incubation at 10 degrees C in histidine-supplemented Trypticase soy broth (BBL Microbiology Systems, Cockeysville, Md.), urocanic acid was measured by thin-layer chromatography. Fifty-eight of the cultures were positive for urocanic acid, with the eight most active isolates producing ca. 10 mg/100 ml. These observations, coupled with a report that urocanic acid may be the predominant histidine metabolite in fish held at low temperatures, all suggest that urocanic acid may be a useful alternative to histamine as a spoilage index in scombroid and other fish that are rich in endogenous histidine.