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

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.