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. This paper 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 protein·kg-1 as natural emulsifiers. Our 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 DH 5%, especially those from sunflower seed meal, provided higher physical stability, regardless of the enzymatic treatment. For instance, the average D[3,2] 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. CONCLUSIONS: These results 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.