Evaluation of Plant Protein Hydrolysates as Natural Antioxidants in Fish Oil-In-Water Emulsions

Abstract

In this work, we evaluated the physical and oxidative stabilities of 5% w/w fish oil-in-water emulsions stabilized with 1%wt Tween20 and containing 2 mg/mL of protein hydrolysates from olive seed (OSM–H), sunflower (SFSM–H), rapeseed (RSM–H) and lupin (LUM–H) meals. To this end, the plant-based substrates were hydrolyzed at a 20% degree of hydrolysis (DH) employing a mixture 1:1 of subtilisin: trypsin. The hydrolysates were characterized in terms of molecular weight profile and in vitro antioxidant activities (i.e., DPPH scavenging and ferrous ion chelation). After incorporation of the plant protein hydrolysates as water-soluble antioxidants in the emulsions, a 14-day storage study was conducted to evaluate both the physical (i.e., ζ-potential, droplet size and emulsion stability index) and oxidative (e.g., peroxide and anisidine value) stabilities. The highest in vitro DPPH scavenging and iron (II)-chelating activities were exhibited by SFSM–H (IC50 = 0.05 ± 0.01 mg/mL) and RSM–H (IC50 = 0.41 ± 0.06 mg/mL). All the emulsions were physically stable within the storage period, with ζ-potential values below −35 mV and an average mean diameter D[4,3] of 0.411 ± 0.010 μm. Although LUM–H did not prevent lipid oxidation in emulsions, OSM–H and SFSM–H exhibited a remarkable ability to retard the formation of primary and secondary lipid oxidation products during storage when compared with the control emulsion without antioxidants. Overall, our findings show that plant-based enzymatic hydrolysates are an interesting alternative to be employed as natural antioxidants to retard lipid oxidation in food emulsions.

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

“…Previous studies have tested the antioxidant properties of protein hydrolysates from both plant substrates when incorporated as ingredients (20 g kg −1 ) in 5% fish O/W emulsions. 14 Plant meals were analyzed for their protein content, presenting average values of 209 g kg −1 and 246 g kg −1 , respectively. As for their lipid content, it ranged between 80 and 140 g kg −1 for the olive meal and was less than 40 g kg −1 for the sunflower meal.…”

“…Protein hydrolysates at degree DH 20% were obtained from the plant meal substrates, following the protocol described by Ospina-Quiroga. 14 To this end, a solution containing 25 g kg −1 protein was prepared by mixing the different plant meals with distilled water at 50 °C. The solution was then transferred to a jacketed glass reactor of 1 L capacity.…”

“…The solids retained after vacuum filtration of the plant meal hydrolysates were dried at 105 °C for 2 h, defining the percentage solubilization as described in a previous study: 14…”

“…13 To overcome this, some successful techniques have been developed to encapsulate fish oils into colloidal systems like oil-in-water (O/W) emulsions, providing better dispersibility, stability and bioavailability. 14 Simple emulsion systems generally are formed by high shear mixing of oil and water, adding synthetic surfactants or animal protein-derived compounds as emulsifiers. 11 Emulsions are thermodynamically unstable systems where oily and aqueous phases tend to separate, being necessary to incorporate an emulsifier/ surfactant to provide kinetic stability.…”

“…skin allergies, gastrointestinal disorders, or even cancer risk associated with long-term intake). 10,14 This drawback, as well as the clean-label trend in the food industry, has increased the interest in searching novel emulsifiers and antioxidants of natural origin 15 such as peptides with bioactivity and technofunctional characteristics. The last exerts multiple advantages such as biodegradability, sustainable production and suitable performance in extreme media conditions of pH, temperature and salinity.…”