###### Abstract  
High pressure is an industrially established food preservation process applied for the minimal processing or cold pasteurization of chilled, fresh, or ready-to-eat products. This study aimed to quantify the effectiveness of high pressure on the inactivation of spoilage microflora and the shelf life extension of European sea bass (_Dicentrarchus labrax_) fillets. Fish fillets were subjected to mild, high pressure conditions (100-400 MPa; 3-25 \({}^{\circ}\)C; 5-10 min) and then stored at 0.0 \(\pm\) 0.2 \({}^{\circ}\)C. Their shelf life was evaluated in terms of their microbiological, physicochemical, and sensorial quality. The results indicated that a shelf life extension of 1-5 d at 0 \({}^{\circ}\)C was achieved when pressures of 100 MPa were applied, whereas higher pressures resulted in an up to 5-fold increase in the shelf life of the fillets, depending on the applied pressure and temperature. A high pressure treatment combined with vacuum packaging showed an additional effect on the shelf life extension of the fillets, increasing the shelf life by 4-12 d when compared to aerocially stored products. Moreover, the high pressure treatment prevented lipid oxidation throughout the storage period, indicating no formation of secondary lipid oxidation products. The estimated shelf life of the fish fillets based on their sensorial quality was in accordance with the estimation based on the microbiological data. high pressure processing; low temperature; bacterial inactivation; shelf life; European sea bass +
Footnote †: journal: Applied Sciences  
Regarding raw fish, several studies have been conducted to report the efficacy of HP treatment on the inactivation of a variety of fish spoilage bacteria, mostly including Gram-negative bacteria, i.e., _Pseudomonas_ spp., H\({}_{2}\)S-producing bacteria, and _Enterobacteriaceae_ and _Vibrio_ spp. These studies also reported on the effect of HP on the quality characteristics of the fish products such as color, lipid oxidation, and texture. Recently, [PERSON] et al. [10] reviewed research conducted over the past six years (2016-2021) on the advantages of HP processing for the quality of fish and seafood, and [PERSON] et al. [11] reviewed the effects of HP processing on aquatic products, emphasizing the sensorial properties of the processed fish product. Both studies revealed that HP processing has mostly been studied in albacore, cod, and salmon [12; 13; 14; 15; 16], while few works have been published concerning the European sea bass [17; 18; 19]. HP processing is more favorable for fish with white flesh, e.g., white tuna and cod fish, due to its \"whitening\" effect on the fish flesh, which is induced by the denaturation of the proteins [20], especially when fish fillets are treated instead of whole fish. Taking into consideration the different effects resulting in fish fillets from the different HP processing parameters, further research is required to determine the optimal HP conditions in terms of pressure, temperature, and holding time required for the inactivation of spoilage microflora in view of the shelf life extension of each different fish matrix while having minimal effects on other quality parameters. The initially adopted industrial HP procedure, an alternative to thermal pasteurization, included processing at an ambient temperature and pressures of 550-600 MPa for a short processing time, i.e., 3-10 min. With a few exceptions, this was performed in the final package [21]. Under these conditions, HP is effective inactivating both pathogenic (_Listeria monocytogenes_ and _Escherichia coli_[22; 23]) and spoilage microflora in fish (total aerobic and mesophilic bacteria, including _Pediococcus_ spp. [24; 25; 26; 27]).