Is Pulsed Electric Field (PEF) a Useful Tool for the Valorization of Solid and Liquid Sea Bass Side Streams?: Evaluation of Nutrients and Contaminants

In this study, fresh sea bass’s (Dicentrarchus labrax) heads, skin, viscera, and muscle were evaluated for their potential valorization as a source of nutrients and bioactive compounds. For this purpose, a pulsed electric field (PEF) treatment (1.0 kV/cm field strength and 220.5 kJ/kg specific energy for head, 3.0 kV/cm and 299.4 kJ/kg for skin, 3.0 kV/cm and 123.7 kJ/kg for viscera and muscle) was used. Subsequently, extraction processes were carried out using either 100% water or 50% ethanol. Protein assessment (protein content and bioactive peptides’ identification), as well as ICP-MS analysis of minerals and heavy metals, was conducted on both the solid matrices and liquid extracts. The findings indicate that the choice of solvent (100% water or 50% ethanol) and PEF treatment significantly (p < 0.05) affected protein recovery in the sea bass side streams liquid extracts, while a considerable protein amount was retained in the solid matrices. Furthermore, the ICP-MS analysis of minerals revealed that PEF treatment significantly (p < 0.05) improved mineral recovery in the head and muscle liquid extracts. However, a considerable amount of minerals remained in the solid matrices. Lower contents of heavy metals were found in the liquid extracts compared to the solid matrices, being anyway the quantities of the five heavy metals analyzed within edible and safe limits. Additionally, the total antioxidant capacity (TAC) of sea bass side stream extracts was assessed to measure the potential antioxidant bioactive compounds in the liquid extracts. PEF treatments significantly (p < 0.05) increased the TAC of the liquid extracts from sea bass viscera, as opposed to other side streams. Both 100% water and 50% ethanol were effective as extraction solvents, promoting the recovery of high-added-value compounds not only from the liquid extracts but also from solid matrices. Thus, PEF pre-treatment can be considered a valuable technique to enhance fish side stream valorization.