Determination of volatile compounds of precooked prawn (Penaeus vannamei) and cultured gilthead sea bream (Sparus aurata) stored in ice as possible spoilage markers using solid phase microextraction and gas chromatography/mass spectrometry

BACKGROUND: Solid phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) have been reported as useful techniques for analysing volatile compounds to monitor fish freshness. In this study, SPME/GC/MS was applied to cultured gilthead sea bream and precooked prawn stored in ice for 6 days in order to find possible markers of spoilage. Total volatile basic nitrogen (TVB-N) was also determined as a common index of spoilage. RESULTS: The TVB-N value at the end of the storage period for cultured gilthead sea bream (302.40 +/- 8.50 mg kg(-1)) was within the range of acceptability for edible fish (300-400 mg kg(-1)) but could be considered at the beginning of spoilage. For precooked prawn the TVB-N value at day 6 (863.04 +/- 7.84 mg kg(-1)) was not acceptable for human consumption. SPME/GC/MS identified 30 compounds in cultured gilthead sea bream and 49 compounds in precooked prawn. In particular, 3-methyl-1-butanol, 2-methylbutanal, 3-methylbutanal and 3-hydroxy-2-butanone increased during refrigerated storage both in the two species investigated here and in other species reported elsewhere and could be considered as markers of spoilage. CONCLUSION: This study confirmed that SPME/GC/MS can be considered an efficient method suitable for analysing the volatile compounds of both raw fish and fishery products in order to monitor loss of freshness. (C) 2008 Society of Chemical Industry