Bromelain-Assisted Hydrolysis of Swordfish (Xiphias Gladius) Skin: Process Optimization and Hydrolysate Characterization

Substantial quantities of by-products are generated in the fish processing industry such as skin, bones, heads, and viscera, which are often underutilized and mainly destined for fishmeal or fertilizer production. Enzymatic hydrolysis represents a sustainable strategy to valorize these wastes by producing fish protein hydrolysates (FPHs), which are rich in bioactive peptides and amino acids. This process occurs under mild conditions and depends on enzyme-specific pH and temperature, making it suitable for food applications. Bromelain, a proteolytic enzyme extracted from pineapple, is widely used in the food industry due to its ability to efficiently break peptide bonds in proteins. The present study focused on optimizing the enzymatic hydrolysis of swordfish (Xiphias gladius) skin using bromelain to obtain FPHs with altered physicochemical and technological properties. Optimal hydrolysis conditions were identified as pH 5, a solid-to-liquid ratio of 1:1, and an incubation time of 15 minutes. Following optimization, the effects of different bromelain concentrations on functional properties such as emulsifying capacity, solubility, and fat-retaining capacity were evaluated. Overall, this approach supports waste valorization, sustainability, and the development of a circular bioeconomy in the fish processing sector.