Use of olive and sunflower protein hydrolysates for the physical and oxidative stabilization of fish oil‐in‐water emulsions

Abstract BACKGROUND Olive and sunflower seeds are by‐products generated in large amounts by the plant oil industry. The technological and biological properties of plant‐based substrates, especially protein hydrolysates, have increased their use as functional ingredients for food matrices. The present study evaluates the physical and oxidative stabilities of 50 g kg −1 fish oil‐in‐water emulsions where protein hydrolysates from olive and sunflower seeds were incorporated at 20 g kg −1 protein as natural emulsifiers. The goal was to investigate the effect of protein source (i.e. olive and sunflower seeds), enzyme (i.e. subtilisin and trypsin) and degree of hydrolysis (5%, 8% and 11%) on the ability of the hydrolysate to stabilize the emulsion and retard lipid oxidation over a 7‐day storage period. RESULTS The plant protein hydrolysates displayed different emulsifying and antioxidant capacities when incorporated into the fish oil‐in‐water emulsions. The hydrolysates with degrees of hydrolysis (DH) of 5%, especially those from sunflower seed meal, provided higher physical stability, regardless of the enzymatic treatment. For example, the average D [2, 3] values for the emulsions containing sunflower subtilisin hydrolysates at DH 5% only slightly increased from 1.21 ± 0.02 μm (day 0) to 2.01 ± 0.04 μm (day 7). Moreover, the emulsions stabilized with sunflower or olive seed hydrolysates at DH 5% were stable against lipid oxidation throughout the storage experiment, with no significant variation in the oxidation indices between days 0 and 4. CONCLUSION The results of the present study support the use of sunflower seed hydrolysates at DH 5% as natural emulsifiers for fish oil‐in‐water emulsions, providing both physical and chemical stability against lipid oxidation. © 2024 Society of Chemical Industry.