Evaluation of Total Volatile Basic Nitrogen, Formaldehyde, and Formic Acid as Markers to Define the Acceptability of Farmed Sea Bass and Sea Bream Stored Under Vacuum (VP) or in Modified-Atmosphere Packaging (MAP) at 4 ± 2 °C

The aim of this work was to propose an objective parameter to define the acceptability of fresh sea bass and sea bream among concentrations of formaldehyde, formic acid, and TVB-N. As indicated, TVB-N appeared to be the most appropriate index. The formaldehyde value cannot be used because it increased until day 6 and then decreased because it was transformed into formic acid. The decrease was observed at all of the times tested. Nevertheless, formic acid also cannot be considered as a valid parameter because in both of the tested fish, it reached values of less than 7.2 mg/kg at 15 days of storage, even though the sensorial analysis indicated the loss of acceptability. In addition, this value is 4–7 times lower than the concentration present in other fresh fish. Consequently, TVB-N represents the only parameter of interest for defining acceptability for both fish species and it can be accepted as the freshness index. Considering the results of the microbial, physico-chemical, and sensory analysis, a level of TVB-N less or equal to 35 mg N/100 g of product was observed up to 12 days of storage. Then, at 15 days, TVB-N reached values over 40 mg N/100 g and both the fish were no longer acceptable, as demonstrated by sensory analysis. For this reason, this value can also be proposed as the limit of freshness for sea bass and sea bream, stored either in VP or in MAP at 4 ± 2 °C. Considering the microbial, physico-chemical, and sensorial analysis of both fish species, a shelf-life limit of 12 days was proposed.