Thierry Serot

Sensory characteristics of spoilage and volatile compounds associated with bacteria isolated from cooked and peeled tropical shrimps using SPME-GC-MS analysis

The spoilage potential of six bacterial species isolated from cooked and peeled tropical shrimps (Brochothrix thermosphacta, Serratia liquefaciens-like, Carnobacterium maltaromaticum, Carnobacterium divergens, Carnobacterium alterfunditum-like and Vagococcus penaei sp. nov.) was evaluated. The bacteria were inoculated into shrimps, packaged in a modified atmosphere and stored for 27 days at 8 °C. Twice a week, microbial growth, as well as chemical and sensory changes, were monitored during the storage period. The bacteria mainly involved in shrimp spoilage were B. thermosphacta, S. liquefaciens-like and C. maltaromaticum whose main characteristic odours were cheese-sour, cabbage-amine and cheese-sour-butter, respectively. The volatile fraction of the inoculated shrimp samples was analysed by solid-phase microextraction (SPME) and gas chromatography coupled to mass spectrometry (GC-MS). This method showed that the characteristic odours were most likely induced by the production of volatile compounds such as 3-methyl-1-butanal, 2,3-butanedione, 2-methyl-1-butanal, 2,3-heptanedione and trimethylamine.

Determination of PAH profiles by GC–MS/MS in salmon processed by four cold-smoking techniques

An analytical method based on gas chromatography/tandem mass spectrometry (GC–MS/MS) (triple quadrupole device) has been developed for quantification of polycyclic aromatic hydrocarbons (PAHs) in smoked salmon. This method was applied to determine PAH concentrations in smoked fish and assess the impact of four industrial smoking processes on their profiles. Two smokehouse temperatures and three smoke-exposure times were applied. All the smoking techniques used lead to acceptable PAH levels: the quantities recovered are 100 times lower than the legal limit (5 µg kg−1) concerning the principal PAH, i.e. benzo[a]pyrene. To compare different smoking processes, the toxic equivalent quantity (TEQ) approach was chosen. Smouldering leads to the highest TEQ, while liquid smoke leads to the lowest TEQ.