Valorization of the Invasive Fish Atherina boyeri (Risso, 1810) as a Source of Protein Hydrolysates with Functional and Bioactive Properties

The invasive fish <i>Atherina boyeri</i> constitutes an ecologically disruptive yet underexploited biomass with strong potential for transformation into value-added biofunctional ingredients. This study investigates the functional, antioxidant, and antimicrobial properties of protein hydrolysates that were produced from fish collected in the Hirfanlı and Yamula reservoirs using three commercial proteases (alcalase, bromelain, and flavourzyme). Bromelain produced the highest degree of hydrolysis, yielding higher proportions of low-molecular-weight peptides and greater radical-scavenging activity. Flavourzyme hydrolysates exhibited the most favorable emulsifying properties, Alcalase hydrolysates produced the highest foaming capacity and stability. All hydrolysates showed high absolute zeta-potential values across pH 3-9, demonstrating strong colloidal stability. Protein solubility remained above 80% across most pH levels, indicating extensive peptide release and improved compatibility with aqueous media. The Oil-binding capacity (2.78-3.75 mL/g) was consistent with reported values for marine hydrolysates. Antioxidant and antimicrobial evaluations revealed clear enzyme-dependent patterns, with Bromelain exhibiting the strongest DPPH activity and Alcalase and Flavourzyme showing the most pronounced inhibition of major foodborne pathogens. Additionally, all hydrolysates exhibited measurable ACE-inhibitory activity, with flavourzyme-derived peptides showing the highest inhibitory activity, underscoring their potential relevance for antihypertensive applications. These findings highlight the strategic valorization of <i>A. boyeri</i> through enzymatic hydrolysis, demonstrating its potential as a sustainable, clean-label functional ingredient source.