THE SOURCE OF 2,6-DIBROMOPHENOL - CAUSE OF AN IODOFORM TAINT IN AUSTRALIAN PRAWNS

The presence of 2,6-dibromophenol in prawn meat in concentrations above 60 ng/kg produces a detectable iodoform-like flavour. This compound is usually accompanied by other bromophenols including 2- and 4-bromophenol, 2,4-dibromophenol and 2,4,6-tribromophenol. Previous studies have suggested that some marine algae and bryozoa from the Gutters region of Exmouth Gulf, Western Australia, were the possible sources of these compounds in the local endeavour prawn Metapenaeus endeavouri. Recently, a selection of eight marine algae, two bryozoa, a hydroid and eight sponges were collected from this region and were extracted by simultaneous distillation-solvent extraction. The extracts were analysed for bromophenols by high resolution gas chromatography-multiple ion detection-mass spectrometry. Quantitative data were obtained on individual compounds by the use of 3,5-dimethyl-2,4,6-trichloroanisole as an internal standard. 2-Bromophenol, 2,4- and 2,6-dibromophenol and 2,4,6-tribromophenol were shown to be present in all species and 4-bromophenol in all but two species of marine algae. The concentrations of these compounds varied from 0.1-mu-g/kg for 4-bromophenol in a marine algae to 240-mu-g/kg for 2,4,6-tribromophenol in a sponge. The highest concentration of 2,6-dibromophenol was found in a bryozoan (96-mu-g/kg) and the lowest in a marine algae (0.29-mu-g/kg). In general, there was about 30 times more of the latter compound in the bryozoa than in the algae. Sponges contained about one twelfth of that found in bryozoa. This paper discusses the significance of these results for the possible origin of 2,6-dibromophenol in endeavour prawns, taking into account the latest data available on the feeding habits of penaeid prawns.