Effects of Modified DATEMs with Different Alkyl Chain Lengths on Improving Oxidative and Physical Stability of 70% Fish Oil-in-Water Emulsions

Evaluation of primary and secondary oxidation products in fish oil-in-water emulsions: Effect of metal-complexing peptides and protein hydrolysates

A novel approach consisting of preselection of peptides using bioinformatics tool followed by final selection using Surface Plasmon Resonance (SPR) - an efficient technique to investigate metal complexing properties of peptides/hydrolysates - was developed. Selected pea hydrolysates and synthetic metal chelating peptides potentially present in pea hydrolysates were investigated for their ability to inhibit the lipid oxidation in emulsions composed of 5 % w/w fish oil and stabilized with Tween® 20. Results indicated that addition of peptides/hydrolysates did not impact the physical stability of emulsions and led to lower level of lipid hydroperoxides. Moreover, peptide KGKSR inhibited the generation of 1-penten-3-ol and hexanal to the same level as ethylenediaminetetraacetic acid (EDTA) did and the formation of 2 ethyl-furan was lower than when EDTA was added. Peptide GRHRQKHS showed same concentration of hexanal as EDTA thus confirming efficacy of using SPR for selecting peptides/hydrolysates to use as antioxidants in emulsions.

Antioxidant peptides from alternative sources reduce lipid oxidation in 5% fish oil-in-water emulsions (pH 4) and fish oil-enriched mayonnaise

Bioinformatics tools were used to predict radical scavenging and metal chelating activities of peptides derived from abundant potato, seaweed, microbial, and spinach proteins. The antioxidant activity was evaluated in 5% oil-in-water emulsions (pH4) and best-performing peptides were tested in mayonnaise and compared with EDTA. Emulsion physical stability was intact. The peptide DDDNLVLPEVYDQD showed the highest protection against oxidation in both emulsions by retarding the formation of oxidation products and depletion of tocopherols during storage, but it was less efficient than EDTA when evaluated in mayonnaise. In low-fat emulsions, formation of hydroperoxides was reduced 4-folds after 5 days compared to control. The concentration effect of the peptide was confirmed in mayonnaise at the EDTA equimolar concentration. The second-best performing peptides were NNKWVPCLEFETEHGFVYREHH in emulsion and AGDWLIGDR in mayonnaise. In general, the peptide efficacy was higher in low-fat emulsions. Results demonstrated that peptide negative net charge was important for chelating activity.

Interfacial effects of gallate alkyl esters on physical and oxidative stability of high fat fish oil-in-water emulsions stabilized with sodium caseinate and OSA-modified starch

Effects of sodium caseinate (SC) and its combination with OSA-modified starch (SC-OS; 1:1) alone and with n-alkyl gallates (C0-C18) on the physical and oxidative stability of high-fat fish oil-in-water emulsion were evaluated. SC emulsion contained the smallest droplets and highest viscosity due to the fast adsorption at droplet surfaces. Both emulsions had non-Newtonian and shear-thinning behavior. A lower accumulation of lipid hydroperoxides and volatile compounds was found in SC emulsion due to its better Fe²⁺ chelating activity. The incorporated short-chain gallates (G1 > G0 ∼ G3) in SC emulsion had a strong synergistic effect against lipid oxidation compared to that of SC-OS emulsion. The better antioxidant efficiency of G1 can be related to its higher partition at the oil-water interface, while G0 and G3 had a higher partition into the aqueous phase. In contrast, G8, G12, and G16 added emulsions indicated higher lipid oxidation due to their internalization inside the oil droplets.

Recent Trends in Improving the Oxidative Stability of Oil-Based Food Products by Inhibiting Oxidation at the Interfacial Region

In recent years, new approaches have been developed to limit the oxidation of oil-based food products by inhibiting peroxidation at the interfacial region. This review article describes and discusses these particular approaches. In bulk oils, modifying the polarity of antioxidants by chemical methods (e.g., esterifying antioxidants with fatty alcohol or fatty acids) and combining antioxidants with surfactants with low hydrophilic–lipophilic balance value (e.g., lecithin and polyglycerol polyricinoleate) can be effective strategies for inhibiting peroxidation. Compared to monolayer emulsions, a thick interfacial layer in multilayer emulsions and Pickering emulsions can act as a physical barrier. Meanwhile, high viscosity of the water phase in emulsion gels tends to hinder the diffusion of pro-oxidants into the interfacial region. Furthermore, applying surface-active substances with antioxidant properties (such as proteins, peptides, polysaccharides, and complexes of protein-polysaccharide, protein-polyphenol, protein-saponin, and protein-polysaccharide-polyphenol) that adsorb at the interfacial area is another novel method for enhancing oil-in-water emulsion oxidative stability. Furthermore, localizing antioxidants at the interfacial region through lipophilization of hydrophilic antioxidants, conjugating antioxidants with surfactants, or entrapping antioxidants into Pickering particles can be considered new strategies for reducing the emulsion peroxidation.

Oxidation and oxidative stability in emulsions

Emulsions are implemented in the fabrication of a wide array of foods and therefore are of great importance in food science. However, the application of emulsions in food production is restricted by two main obstacles, that is, physical and oxidative stability. The former has been comprehensively reviewed somewhere else, but our literature review indicated that there is a prominent ground for reviewing the latter across all kinds of emulsions. Therefore, the present study was formulated in order to review oxidation and oxidative stability in emulsions. In doing so, different measures to render oxidative stability to emulsions are reviewed after introducing lipid oxidation reactions and methods to measure lipid oxidation. These strategies are scrutinized in four main categories, namely storage conditions, emulsifiers, optimization of production methods, and antioxidants. Afterward, oxidation in all types of emulsions, including conventional ones (oil-in-water and water-in-oil) and uncommon emulsions in food production (oil-in-oil), is reviewed. Furthermore, the oxidation and oxidative stability of multiple emulsions, nanoemulsions, and Pickering emulsions are taken into account. Finally, oxidative processes across different parent and food emulsions were explained taking a comparative approach.

Lipophilic antioxidant dodecyl caffeate preparation by the esterification of caffeic acid with dodecanol using ionic liquid [Hnmp]HSO4 as a catalyst

Caffeic acid (CA) is widely found in nature, and has a broad spectrum of biological activities. However, the low hydrophilicity and lipophilicity of CA limited its application. Dodecyl caffeate (DC) is the lipophilic ester of caffeic acid (CA), and also has high antioxidant activity. In this work, CA, used as a substrate, and three ionic liquids with different acidities and H2SO4 were used as economic catalysts for DC preparation. The effects of variables on DC yield were investigated and optimized by response surface methodology (RSM). And the kinetic and thermodynamic parameters of the esterification of CA and dodecanol were evaluated. Results showed that lipophilic DC was successfully synthesized using ionic liquid ([Hnmp]HSO4) as a catalyst. And the optimal conditions by RSM were substrate ratio of 10.2 : 1, IL dosage of 9.8% at 87 °C for 118 min. Under the optional conditions, the maximum DC yield was 94.67 ± 1.32%. The k 0, E a, ΔH, ΔS, and ΔG were 7.18 × 107 mol (L min)-1, 65.77 kJ mol-1, 63.10 kJ (mol K)-1, -103.80 J (mol K)-1, and 99.78 kJ mol-1 at 363 K, respectively. DC prepared in this work showed a good DPPH radical scavenging activity, which indicated that DC can be used as a potential antioxidant in food and cosmetics.

Influence of non-thermal microwaveradiationon emulsifying properties of sunflower protein

Sunflower protein isolate obtained from industrially de-oiled press cake was treated with non-thermal microwave, aiming to investigate how structure and emulsifying properties were affected. Our results indicated that the content of polar amino acids was decreased and solubility and surface hydrophobicity were altered upon exposure to non-thermal microwave. Higher solubility and surface hydrophobicity of the samples treated with defrost mode and also 350 W were accompanied by a smaller size and lower uniformity of the oil droplets compared to the control and other samples. Non-thermal microwave treatment improved the emulsion stability by 1.43 times and defrost mode treated sample had the lowest stability index after 120 min. Interfacial dilatational rheology measurements revealed that 70 and 350 W treated samples created higher elastic, less stretchable solid-like layer at the O/W interface in comparison with defrost mode treated and control samples. Consequently, non-thermal microwave treatment could be considered as a promising simple, fast, and "green" protein modification technique.

Rambutan (Nephelium lappaceum) kernel olein as a non-hydrogenated fat component for developing model non-dairy liquid creamer: effect of emulsifier concentration, sterilization, and pH

In this work, the effects of the emulsifier concentration, sterilization process, and pH on the properties and stability of the model liquid creamer were evaluated. Applying diacetyl tartaric acid ester of mono- and diglycerides or DATEM at a concentration of 0.3% (w/w) in the presence of 2% (w/w) sodium caseinate produced stable model liquid creamers (10% (w/w) rambutan kernel olein) with a small particle size (Z-average ≈ 200 nm) and a narrow size distribution range (PDI < 0.24). These creamers were stable regarding creaming and coalescence, having non-flocculated particles and a constant flow behavior index (n) after sterilization using autoclaving (121 °C, 1.1 bar for 15 min) and during storage for 150 days at 25 °C. The model liquid creamers were unstable at pH values near the isoelectric point of caseinate (pH 4-5). However, these were stable after mixing with hot coffee solutions based on no observed feathering or sedimentation. The whitening performance of the model liquid creamers compared well with commercial ones. Non-hydrogenated fat-based model non-dairy liquid creamer was successfully formulated using rambutan kernel olein as a fat component. The results obtained in this study are useful for the possible application of fractionated rambutan kernel fat in food products.

Protein derived emulsifiers with antioxidant activity for stabilization of omega-3 emulsions

The performance of a whey protein hydrolysate (WPH) for producing physically and chemically stable omega-3 emulsions was compared to hydrolysates obtained from other sustainable protein sources such as soy (SPH) and blue whiting (BPH). The oxidative stability of hydrolysate-stabilized emulsions was greatly influenced by their physical stability. Emulsion stabilized with BPH suffered a constant increase in droplet size and BPH was not able to prevent omega-3 oxidation, showing high concentration of volatiles. The peroxide value of SPH emulsion increased after the first day of storage, but it had a lower concentration of volatiles. In contrast, WPH-stabilized emulsion, which did not had any change in droplet size during storage, showed the highest oxidative stability. Therefore, our results confirmed that WPH is an interesting option for physical and oxidative stabilization of omega-3 emulsions, while SPH could be used in emulsions with shorter storage time such as pre-emulsions for microencapsulation of omega-3 oils.

Enrichment of mayonnaise with a high fat fish oil-in-water emulsion stabilized with modified DATEM C14 enhances oxidative stability

Enrichment of mayonnaise using delivery emulsions (DEs) containing 70% fish oil versus neat fish oil was investigated. DEs were produced with combined use of sodium caseinate, diacetyl tartaric acid esters of mono- and diglycerides (DATEM), and/or modified DATEMs with different length (C12 or C14) and covalently attached caffeic acid. Physical and oxidative stability of the mayonnaises were analyzed based on parameters including droplet size, viscosity, peroxide value, volatile compounds, and sensory properties. DEs addition to mayonnaise resulted in larger droplets and lower viscosity compared to neat fish oil. However, zeta potential was higher in mayonnaises with DEs containing DATEMs. Mayonnaise containing DATEM C14 had higher protein surface load leading to a thicker interfacial layer, lower formation of hexanal, (E)-2-hexenal, and (E)-2-heptenal as well as lower rancid odour intensity compared to mayonnaise containing DATEM and free caffeic acid, and thus benefitted from the location of the antioxidant at the interface.

Small-Angle Neutron Scattering Study of High Fat Fish Oil-In-Water Emulsion Stabilized with Sodium Caseinate and Phosphatidylcholine

We report on small-angle neutron scattering (SANS) investigations of separate phase domains in high fat (70%) oil-in-water emulsions emulsified with the combination of sodium caseinate (CAS) and phosphatidylcholine (PC). The emulsion as a whole was studied by contrast variation to identify scattering components dominated by individual emulsifiers. The emulsion was subsequently separated into the aqueous phase and the oil-rich droplet phase, which were characterized separately. Emulsions produced with 1.05% (w/w) CAS and PC fraction which varies between 1.75% (w/w) and 0.35% (w/w) provided droplets between 10 and 19 μm in surface weighted mean in 70% fish oil-in-water emulsions. At least two-third of the overall CAS is associated with the interface, while the rest remains with the aqueous phase. Six percent of PC formed a monolayer in the interface, while the rest of the PC remains in the droplet phase in the form of multilayers. When the separated components were resuspended, the resuspended emulsion showed similar characteristics compared to the original emulsion in terms of droplet size distribution and neutron scattering. Instead, CAS in the aqueous phase separated from the emulsion shows aggregation not present in the corresponding CAS-in-D₂O system.

Interfacial structure of 70% fish oil-in-water emulsions stabilized with combinations of sodium caseinate and phosphatidylcholine

We report on the structural evaluation of high fat fish oil-in-water emulsions emulsified with sodium caseinate (CAS) and phosphatidylcholine (PC). The microemulsions contained 70% (w/w) fish oil with 1.05-1.4% (w/w) CAS and 0.4-1.75% (w/w) PC and were studied by the combination of light scattering together with small-angle X-ray and neutron scattering (SAXS/SANS). Aqueous CAS forms aggregates having a denser core of about 100 kDa and less dense shell about 400 kDa with the hard sphere diameter of 20.4 nm. PC appears as multilayers whose coherence length spans from 40 to 100 nm. PC monolayer separates oil and water phases. Moreover, 80% CAS particles are loosely bound to the interface but are not forming continuous coverage. The distance between aggregated CAS particles in microemulsion is increased compared to CAS aggregates in pure CAS-in-water system. PC multilayers become larger in the presence of oil-water interface compared to the pure PC mixtures. Bilayers become larger with increasing PC concentration. This study forms a structural base for the combination of CAS and PC emulsifiers forming a well-defined thin and dense PC layer together with thick but less dense CAS layer, which is assumed to explain its better oxidative stability compared to single emulsifiers.