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.

Shrimp are among the most valuable seafood commodities worldwide, but are also highly perishable, making their quality preservation a critical issue for both food safety and supply chain sustainability. The rapid deterioration of fresh shrimp contributes to significant post-harvest losses, highlighting the need for reliable freshness indicators capable of supporting shelf-life assessment under commercial conditions. This study evaluated the evolution of microbiological, physicochemical, and sensory parameters in two commercially important Mediterranean shrimp species, Parapenaeus longirostris and Melicertus kerathurus, stored on ice for up to 15 days under retail-like conditions. Microbial load, pH, total volatile basic nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARS), formaldehyde, formic acid, and sensory attributes were monitored during storage. Microbial populations increased progressively over time but remained below commonly accepted spoilage thresholds, while physicochemical indicators showed significant changes associated with post-mortem biochemical processes. In particular, TVB-N, pH, and formic acid increased during storage, whereas formaldehyde levels decreased, suggesting the progressive transformation of trimethylamine-N-oxide degradation products. Sensory analysis indicated that shrimp maintained high quality up to approximately 12 days of iced storage, whereas samples stored for 15 days approached the limit of consumer acceptability. The combined behaviour of microbial, chemical, and sensory indicators highlights the importance of a multidimensional approach for evaluating shrimp freshness under commercial storage conditions. Based on the experimental dataset, practical reference ranges for key quality parameters are proposed (pH < 7.4; TVB-N ≤ 30 mg N/100 g; formaldehyde < 10 mg/kg; formic acid < 18 mg/kg). These results may support improved freshness evaluation, contribute to more accurate shelf-life estimation, and help reduce unnecessary seafood waste within the supply chain.