Biogenic amines formation and its relation to microbiological and sensory attributes in ice-stored whole, gutted and filleted Mediterranean Sea bass (Dicentrarchus labrax)

The effect of gutting and filleting on the formation of biogenic amines and its relation to microbiological and sensory attributes in ice-stored sea bass (Dicentrarchus labrax) was studied. Pseudomonads, H2S-producing bacteria, Brochothrix thermosphacta and to a lesser extent Enterobacteriaceae were the dominant micro-organisms in whole, gutted and filleted sea bass. Higher populations (P<0.05) of these micro-organisms were present in filleted sea bass as compared to gutted and whole fish samples. Seven biogenic amines namely: putrescine, cadaverine, spermidine, tyramine, tryptamine, spermine and histamine were determined in fish samples. Putrescine was the main biogenic amine formed. Its highest value (23.86 mg/kg) was recorded in filleted sea bass on day 16 of storage. Respective putrescine values for gutted and whole sea bass were 12.64 and 3.12 mg/kg (day 16). Putrescine levels of whole, gutted and filleted sea bass showed a steep increase between days 11 and 16 of storage when respective population of Pseudomonads reached approximately 10⁶-10⁷ (whole), 10⁷-10⁸ (gutted) and 10⁸-10⁹ (filleted) cfu/g. Cadaverine was not detected before day 9 in whole and gutted sea bass samples and before day 11 in filleted samples. Surprisingly, for whole sea bass a maximum value of cadaverine (6.47 mg/kg) was recorded on the final day of storage (day 16), whereas respective levels for gutted and filleted samples levels were lower (1.19 and 0.58 mg/kg). Almost simultaneous production of tryptamine and tyramine was observed in whole, gutted and filleted sea bass samples throughout the entire storage period in ice. Spermine and spermidine showed a decreasing pattern with increasing storage and were undetectable in whole and gutted sea bass samples between day 13 and 16 of storage. Finally, no histamine was present in both whole and gutted sea bass, whereas interestingly, for filleted sea bass samples, levels of histamine increased after day 9 of storage but remained low (<3 mg/kg) throughout the entire storage period. During this period Enterobacteriaceae counts remained below or in the vicinity of 10⁶ cfu/g. Based on sensory data, after 8-9 days for both the gutted and the filleted sea bass samples (time for development of initial off-flavors), putrescine values between 3.63 and 4.05 mg/kg were recorded. This range of values may possibly be proposed as the upper limit for spoilage initiation for the gutted and filleted sea bass. This does not hold for whole sea bass which became sensorily unacceptable after 15-16 days of storage at a putrsecine content of 3.12 mg/kg. Development of initial off-flavors occurred when total viable counts were between 10⁷ and 10⁸ cfu/g.