Enhancement of fish protein hydrolysates for salad dressing through high shear and sterilization pre-treatments

Thermal and mechanical treatments may affect the structure of hydrolyzed proteins, thus influencing the obtaining of peptides with improved bioactivity. In this work, tilapia muscle was treated by thermal sterilization or homogenization with ultra-turrax (UT) and hydrolyzed with alcalase to obtain FPHs with antioxidant properties in salad dressing. To evaluate the bioactive potential of FPHs, the acetylcholinesterase inhibition assay was applied, resulting in up to 45.87% inhibition for the UT sample (60 mg/mL). Also, no cytotoxicity was detected by Allium cepa model for all FPHs. The emulsifying activity index and emulsifying stability index of FPHs indicated better emulsifying capacity in basic pH. As a proof of concept, FPHs were used as an emulsifying/antioxidant agent to prepare a salad dressing. FPHs increased the formulation's protein content, pseudoplastic behavior, color, and texture. In addition, FPHs aided the oxidative stability of salad dressing (evaluated by oil's extinction coefficient), demonstrating potential application in emulsified foods by acting on the elimination of radicals generated in lipid oxidation.

Practical applications

Fish protein hydrolysates (FPHs) offer diverse bioactive properties such as antioxidant, antimicrobial, anticancer, antihypertensive, and acetylcholinesterase (associated with Alzheimer's disease) inhibitory effects. However, optimizing their technological properties poses a challenge, affecting applicability and bioactivity. Industrial processes such as thermal and mechanical treatments can alter protein structures, influencing peptide bioactivity post enzymatic hydrolysis. This study investigates the impact of substrate pre-treatments, sterilization via thermal heating, and homogenization using a rotor-stator system (ultra-turrax) on FPHs' technological properties after hydrolysis with alcalase, including emulsifying capacity and acetylcholinesterase inhibitory capacity. In addition, it explores the application of pre-treated FPHs in a real food system (French salad dressing), assessing rheological properties, texture, and oxidative stability. Such evaluations are crucial for ensuring the feasibility of industrial FPHs production and their application.