Lipid oxidation in corn oil-in-water emulsions stabilized by casein, whey protein isolate, and soy protein isolate

Stimuli-responsive antioxidant Pickering emulsions stabilized by functionalized cellulose nanocrystals

Stimuli-responsive antioxidant Pickering emulsions play crucial role in many industrial areas. This study demonstrated for the first time oil-in-water Pickering emulsions with outstanding antioxidation and responsive demulsification stabilized by functionalized cellulose nanocrystals (CNCs). Dialdehyde cellulose nanocrystals (DACs) were first prepared through the oxidation of CNCs with periodate, followed by the grafting of p-aminophenols (PAPs) onto their surfaces through Schiff base reaction, affording PAP grafted DACs (DAC-g-PAP) via dynamic covalent linkage. The degree of the oxidation (DO) of DACs had a significant effect on the yield of the targeting DAC-g-PAP nanoparticles. High DO (≥40 %) potentially led to the degradation of DACs during the grafting of PAP. The introduced PAP endowed DACs with excellent radical scavenging capability, thereby providing antioxidant properties while improving the hydrophobicity. DAC-g-PAP nanoparticles were then applied as Pickering emulsifiers to prepare oil-in-water Pickering emulsions. The resultant Pickering emulsions indicated exceptional antioxidant and pH-responsiveness together with good freezing-thaw stability. The structures of DAC-g-PAP nanoparticles were thoroughly characterized in this study.

Lipid oxidation in emulsions: New insights from the past two decades

Lipid oxidation constitutes the main source of degradation of lipid-rich foods, including food emulsions. The complexity of the reactions at play combined with the increased demand from consumers for less processed and more natural foods result in additional challenges in controlling this phenomenon. This review provides an overview of the insights acquired over the past two decades on the understanding of lipid oxidation in oil-in-water (O/W) emulsions. After introducing the general structure of O/W emulsions and the classical mechanisms of lipid oxidation, the contribution of less studied oxidation products and the spatiotemporal resolution of these reactions will be discussed. We then highlight the impact of emulsion formulation on the mechanisms, taking into consideration the new trends in terms of emulsifiers as well as their own sensitivity to oxidation. Finally, novel antioxidant strategies that have emerged to meet the recent consumer's demand will be detailed. In an era defined by the pursuit of healthier, more natural, and sustainable food choices, a comprehensive understanding of lipid oxidation in emulsions is not only an academic quest, but also a crucial step towards meeting the evolving expectations of consumers and ensuring the quality and stability of lipid-rich food products.

Enhancing the Thermal Stability of Zein Particle-Stabilized Aeratable Emulsions Through Genipin-Protein Cross-Linking and Its Possible Mechanism of Action

Protein particle-stabilized emulsions often lack thermal stability, impacting their industrial use. This study investigated the effects of genipin (GP)-zein cross-linked particles with varying GP-to-protein weight ratios (0/0.02/0.1:1) on emulsion thermal stability. Enhanced stability was observed at the GP level of 0.1. Heat treatment increased the covalent cross-linking in raw particles and emulsions. Isolated particles from heated emulsions grew in size (micrometer scale) with higher GP levels, unlike heated raw particles (nanoscale). GP-protein cross-linking reduced the droplet-droplet and particle-emulsifier interactions in the heated emulsion. Spectroscopic analysis and electrophoresis revealed that GP-zein cross-linking increased protein structural stability and inhibited nondisulfide and non-GP cross-linking reactions in heated emulsions. The GP-zein bridges between particles at the oil-water interface create strong connections in the particle layer (shell), referred to as "particle-shell locking", enhancing the thermal stability of emulsion significantly. This insight aids the future design of protein-particle-based emulsions, preserving properties like aeratability during thermal processing.

Conjugation of lesser mealworm (Alphitobius diaperinus) larvae protein with polyphenols for the development of innovative antioxidant emulsifiers

Lesser mealworm protein concentrate (LMPC) was conjugated with chlorogenic acid (CA) or tannic acid (TA) using an alkaline method. The impact of polyphenol type and concentration on the physicochemical and structural characteristics, antioxidant, interfacial, and emulsifying properties of the LMPC-polyphenol conjugates were investigated. Under the conditions tested, TA demonstrated higher affinity for LMPC compared to CA. The conjugation of LMPC induced conformational changes as showed by intrinsic fluorescence and FT-MIR raw spectra analysis. The surface hydrophobicity of the conjugates was reduced, leading to increased interfacial tension values for LMPC-TA conjugates without impairment of the emulsifying activity. The antioxidant properties were significantly improved by the conjugation. Flaxseed oil-in-water (O/W) emulsions stabilized by the conjugates and LMPC remained physically stable for 12 days at 50 °C with a notable reduction of secondary oxidation products when conjugates were used. LMPC-TA and LMPC-CA exhibited potential to be used as novel antioxidant emulsifiers in O/W emulsions.

Structural modification of oat protein by thermosonication combined with high pressure for O/W emulsion and model salad dressing production

Oat protein is becoming an important ingredient in beverages and formulated foods owing to its high nutritive value and bland flavor; yet, its functionality remains largely unexplored. This study sought to enhance the surface activity of oat protein isolate (OPI) through high-intensity ultrasound (HIU; at 20 or 60 °C) combined with high pressure homogenization (HP; 30 MPa) treatments. Sonication disturbed the protein conformation and significantly improved surface hydrophobicity (19.7%) and ζ-potential (15.7%), which were further augmented by subsequent HP (P < 0.05). Confocal microscopy revealed a uniform oil droplet distribution in emulsions prepared with HIU+HP combination treated OPI, and the oil droplet size decreased up to 35.6% when compared to that of non-treated OPI emulsion (d = 1718 nm). Emulsifying activity was greater for HIU+HP than for HIU, and the viscosity followed a similar trend. Moreover, while emulsions prepared with HIU or HP treated OPI were more stable than control, the 60 °C HIU+HP combination treatment yielded the maximum stability. In corroboration, a model salad dressing prepared from HIU+HP treated OPI displayed a homogenous oil droplet distribution and an improved viscosity. Therefore, thermosonication combined with high pressure homogenization may be suitable for salad dressings and other oil-imbedded food products.

Ultrasonic and homogenization: An overview of the preparation of an edible protein-polysaccharide complex emulsion

Emulsion systems are extensively utilized in the food industry, including dairy products, such as ice cream and salad dressing, as well as meat products, beverages, sauces, and mayonnaise. Meanwhile, diverse advanced technologies have been developed for emulsion preparation. Compared with other techniques, high-intensity ultrasound (HIUS) and high-pressure homogenization (HPH) are two emerging emulsification methods that are cost-effective, green, and environmentally friendly and have gained significant attention. HIUS-induced acoustic cavitation helps in efficiently disrupting the oil droplets, which effectively produces a stable emulsion. HPH-induced shear stress, turbulence, and cavitation lead to droplet disruption, altering protein structure and functional aspects of food. The key distinctions among emulsification devices are covered in this review, as are the mechanisms of the HIUS and HPH emulsification processes. Furthermore, the preparation of emulsions including natural polymers (e.g., proteins-polysaccharides, and their complexes), has also been discussed in this review. Moreover, the review put forward to the future HIUS and HPH emulsification trends and challenges. HIUS and HPH can prepare much emulsifier-stable food emulsions, (e.g., proteins, polysaccharides, and protein-polysaccharide complexes). Appropriate HIUS and HPH treatment can improve emulsions' rheological and emulsifying properties and reduce the emulsions droplets' size. HIUS and HPH are suitable methods for developing protein-polysaccharide forming stable emulsions. Despite the numerous studies conducted on ultrasonic and homogenization-induced emulsifying properties available in recent literature, this review specifically focuses on summarizing the significant progress made in utilizing biopolymer-based protein-polysaccharide complex particles, which can provide valuable insights for designing new, sustainable, clean-label, and improved eco-friendly colloidal systems for food emulsion. PRACTICAL APPLICATION: Utilizing complex particle-stabilized emulsions is a promising approach towards developing safer, healthier, and more sustainable food products that meet legal requirements and industrial standards. Moreover, the is an increasing need of concentrated emulsions stabilized by biopolymer complex particles, which have been increasingly recognized for their potential health benefits in protecting against lifestyle-related diseases by the scientific community, industries, and consumers.

A new approach to enhance quinoa protein nano-aggregates: Combined pH shifting - High pressure homogenization

The physicochemical characteristics of soluble nano-sized quinoa protein isolates prepared by combined pH shifting and high-pressure homogenization were studied. Commercial quinoa protein isolates were exposed to pH shifting at acidic (pH 2-6) or alkaline (pH 8-12) conditions followed by high-pressure homogenization earlier than neutralizing of pH to 7.0. The pH method under pH 12 followed by high-pressure homogenization was found as the most efficient treatment in the reduction of protein aggregate sizes and transparency, improving soluble protein content and surface hydrophobicity. Quinoa protein isolates treated with pH 12 and high-pressure homogenization increased the solubility from 7.85% to 78.97%, creating quinoa protein isolate nanoaggregates with an average size around 54 nm. The quinoa isolate aggregates were used to produce oil-in-water nanoemulsions, which demonstrated the good stability for 14 d at 4 °C. This new approach might present an effective technique for the modification of functional features of quinoa protein isolates.

Designing ultra-stable linseed oil-in-water Mickering emulsions using whey protein isolate cold-set microgels containing marjoram aqueous extract: Effect of pH and extract on rheological, physical, and chemical properties

In this study, whey protein isolate (WPI) cold-set microgels containing marjoram (Origanum majorana) aqueous extract (MAE) were prepared at different pHs (4.0, 5.0, and 6.0). After characterization, the microgel dispersion was used to stabilize linseed oil-in-water Mickering emulsions (MEs). The resultant MEs were then characterized in terms of physicochemical and rheological properties under the effect of pH and MAE addition. The morphology, particle size, zeta potential, and interfacial tension of microgels were affected by pH and MAE. XRD patterns showed the amorphous structure. Microgel-stabilized MEs did not reveal any significant sign of instability under gravity during 6 months of storage. All MEs had dominant elastic character. Despite the lowest zeta potential values, MEs prepared at pH 4 showed the highest physical stability against gravity but the lowest centrifugal stability against oiling off, which indicated that both viscous and elastic components are required for MEs stability. This sample had the highest apparent viscosity and the strongest viscoelastic properties. Rheological data were best fitted with Herschel-Bulkley and Power Law models. An increase in pH and presence of MAE improved the oxidative stability of MEs. The results of this study showed that WPI microgels are appropriate candidate for long-term stabilization of linseed oil-in-water MEs. The presence of MAE is useful in designing special emulsions in which the aqueous phase is partially replaced by the aqueous extract of medicinal plants.

Parameter control, characterization and stability of soy protein emulsion prepared by microfluidic technology

A flow-focusing microfluidic device driven by pressure was employed in soy protein emulsions with uniform droplet size and good morphology. The results suggested that pressure was an essential factor for droplet formation. The optimum parameter was at a continuous phase pressure of 140 mbar and dispersed phase pressure of 80 mbar. Under this condition, the droplet formation time was shortened to 0.20 s, with average sizes of 39-43 μm and coefficient of variation of about 2 %. Emulsion stability was improved with increasing soy protein isolate (SPI) concentrations. At SPI concentrations higher than 20 mg/mL, the emulsions exhibited improved stability against changes in temperature, pH and salt concentration. Emulsions prepared in this manner exhibited superior oxidative stability than those prepared by conventional methods utilizing homogenizers. This study showed that microfluidic technology can be applied to soy protein emulsions as an effective tool for preparing droplets with uniform size and enhanced stability.

Stability and Digestive Properties of a Dual-Protein Emulsion System Based on Soy Protein Isolate and Whey Protein Isolate

The stability and digestive properties of a dual-protein emulsion consisting of soy protein isolate (SPI) and whey protein isolate (WPI) have been systematically studied. The results showed that the particle size and viscosity of the dual-protein emulsion system decreased continuously with the increase in WPI, and this might be related to the large amount of electric charge on the surface of the emulsion droplets. Dual-protein emulsions with ratios of 3:7 and 5:5 showed the highest emulsion activity, while emulsion stability increased with the increase in WPI. The thicker adsorption layer formed at the interface might have contributed to this phenomenon. After in-vitro-simulated digestion, the emulsion droplet particle size increased substantially due to the weakened electrostatic repulsion on the droplet surface, especially for the intestinal digestion phase. Meanwhile, WPI accelerated the release of free fatty acids in the digestion process, which played a positive role in the nutritional value of the dual-protein emulsion. In accelerated oxidation experiments, WPI also improved the antioxidant properties of the dual-protein emulsion system. This study will provide a new insight and necessary theoretical basis for the preparation of dual-protein emulsions.

Emulsion-Templated Liquid Oil Structuring with Egg White Protein Microgel- Xanthan Gum

In this study, oleogels were prepared by the emulsion-template method using egg-white protein microgel as a gelator and xanthan gum (XG) as thickener. The physicochemical properties of the emulsion and oleogels were investigated. The adsorption of protein on the surface of the oil droplet reached saturation when the protein microgel concentration reached 2%. The excess protein combined with XG and accumulated on the outer layer of the oleogel, which prevented the emulsion from flocculation, enhanced the oil-holding capacity of the oleogel, and had a positive effect on preventing the oxidation of oil. When the concentration of XG was less than 0.4%, the EWP microgel, combined with the XG, stabilized the emulsion. As the concentration of XG was greater than 0.4%, excessive XG in the emulsion improved the viscosity and mechanical properties of the emulsion to prevent the aggregation of oil droplets. However, the change in XG concentration had no significant effect on the oxidation of the oil.

Targeting Interfacial Location of Phenolic Antioxidants in Emulsions: Strategies and Benefits

It is important to have larger proportions of health-beneficial polyunsaturated lipids in foods, but these nutrients are particularly sensitive to oxidation, and dedicated strategies must be developed to prevent this deleterious reaction. In food oil-in-water emulsions, the oil-water interface is a crucial area when it comes to the initiation of lipid oxidation. Unfortunately, most available natural antioxidants, such as phenolic antioxidants, do not spontaneously position at this specific locus. Achieving such a strategic positioning has therefore been an active research area, and various routes have been proposed: lipophilizing phenolic acids to confer them with an amphiphilic character; functionalizing biopolymer emulsifiers through covalent or noncovalent interactions with phenolics; or loading Pickering particles with natural phenolic compounds to yield interfacial antioxidant reservoirs. We herein review the principles and efficiency of these approaches to counteract lipid oxidation in emulsions as well as their advantages and limitations.

Preparation of human milk fat substitute and improvement of its oxidative stability

1,3-Dioleoyl-2-palmitoylglycerol (OPO) was synthesized by enzymatic interesterification using palm stearin rich in tripalmitin (PPP) and ethyl oleate. Enzymatic interesterification parameters such as temperature, water content, enzyme load, and substrate molar ratio were optimized. High contents of C52 (primarily OPO and its isomeric compounds) production (46.7%) and sn-2 palmitic acid (PA) content of 75.3% were detected. In addition, OPO-human milk fat substitute (HMFS) was blended with coconut, soybean, algal and microbial oils at a weight ratio of 0.70:0.18:0.11:0.004:0.007 to simulate fatty acids in human milk fat (HMF) according to the mathematical model. The main and important fatty acids in the Final-HMFS were within the ranges of those present in HMF. The Final-HMFS could promote the absorption of fats and minerals and the development of retina tissues in infants. The mixture of L-ascorbyl palmitate (L-AP) and vitamin E (VE) resulted in a synergistic antioxidant effect both in OPO-HMFS and OPO-HMFS emulsions. This finding has great significance in improving the quality and extending shelf-life of HMFS.

Improvement of Oxidative Stability of Fish Oil-in-Water Emulsions through Partitioning of Sesamol at the Interface

The susceptibility of polyunsaturated fatty acids to oxidation severely limits their application in functional emulsified foods. In this study, the effect of sesamol concentration on the physicochemical properties of WPI-stabilized fish oil emulsions was investigated, focusing on the relationship between sesamol-WPI interactions and interfacial behavior. The results relating to particle size, zeta-potential, microstructure, and appearance showed that 0.09% (w/v) sesamol promoted the formation of small oil droplets and inhibited oil droplet aggregation. Furthermore, the addition of sesamol significantly reduced the formation of hydrogen peroxide, generation of secondary reaction products during storage, and degree of protein oxidation in the emulsions. Molecular docking and isothermal titration calorimetry showed that the interaction between sesamol and β-LG was mainly mediated by hydrogen bonds and hydrophobic interactions. Our results show that sesamol binds to interfacial proteins mainly through hydrogen bonding, and increasing the interfacial sesamol content reduces the interfacial tension and improves the physical and oxidative stability of the emulsion.

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.

Pickering emulsion stabilized by modified pea protein-chitosan composite particles as a new fat substitute improves the quality of pork sausages

Pickering emulsion is a potential substitute for animal fat due to high stability and solid-like properties. Therefore, the effect of replacing 25%-100% pork backfat with Pickering emulsion (75% corn oil volume fraction) stabilized by modified pea protein-chitosan composite particles on the quality of sausages was studied. All meat pastes exhibited a strong gel-like rheological character (G' > G"). The incorporation of Pickering emulsion in sausages enhanced the textural properties (hardness, springiness, chewiness, cohesiveness and resilience) and the uniformity and compactness of micromorphology, as well as suppressed the cooking loss and TBARS content. In particular, the sausages with a backfat substitution ratio of 100%, showing a similar overall sensory acceptability to the backfat sausage, revealed the best rheological properties, texture properties and micromorphology and the lowest cooking loss and fat oxidation (P < 0.05). The results showed that Pickering emulsion stabilized by modified pea protein-chitosan composite particles is a potential fat substitute for meat products with the desirable characteristics.

Effect of the Emulsifier Used in Dunaliella salina-Based Nanoemulsions Formulation on the β-Carotene Absorption and Metabolism in Rats

SCOPE

Microalgae such as Dunaliella salina are a potential sustainable source of natural β-carotene due to their fast growth and high adaptability to environmental conditions. This work aims to evaluate the effect of the incorporation of β-carotene from this alga into different emulsifier-type nanoemulsions (soybean lecithin [SBL], whey protein isolate [WPI], sodium caseinate [SDC]) on its absorption, metabolization, and biodistribution in rats.

METHODS AND RESULTS

Nanoemulsions formulated with different emulsifiers at 8% concentration are obtained by five cycles of microfluidization at 130 mPa, then expose to an in vitro digestion or orally administer to rats. Feeding rats with nanoemulsions improves β-carotene uptake compared to control suspension, especially using SDC and WPI as emulsifiers. A greater presence of β-carotene and retinol in the intestine, plasma, and liver is observed, being the liver the tissue that shows the highest accumulation. This fact can be a consequence of the smaller droplets that protein-nanoemulsions present compared to that with SBL in the intestine of rats, which promote faster digestibility and higher β-carotene bioaccessibility (35%-50% more) according to the in vitro observations.

CONCLUSIONS

Nanoemulsions, especially those formulated with protein emulsifiers, are effective systems for increasing β-carotene absorption, as well as retinol concentration in different rat tissues.

Correlation between interfacial layer properties and physical stability of food emulsions: current trends, challenges, strategies, and further perspectives

Emulsions are thermodynamically unstable systems that tend to separate into two immiscible phases over time. The interfacial layer formed by the emulsifiers adsorbed at the oil-water interface plays an important role in the emulsion stability. The interfacial layer properties of emulsion droplets have been considered the cutting-in points that influence emulsion stability, a traditional motif of physical chemistry and colloid chemistry of particular significance in relation to the food science and technology sector. Although many attempts have shown that high interfacial viscoelasticity may contribute to long-term emulsion stability, a universal relationship for all cases between the interfacial layer features at the microscopic scale and the bulk physical stability of the emulsion at the macroscopic scale remains to be established. Not only that, but integrating the cognition from different scales of emulsions and establishing a unified single model to fill the gap in awareness between scales also remain challenging. In this review, we present a comprehensive overview of recent progress in the general science of emulsion stability with a peculiar focus on interfacial layer characteristics in relation to the formation and stabilization of food emulsions, where the natural origin and edible safety of emulsifiers and stabilizers are highly requested. This review begins with a general overview of the construction and destruction of interfacial layers in emulsions to highlight the most important physicochemical characteristics of interfacial layers (formation kinetics, surface load, interactions among adsorbed emulsifiers, thickness and structure, and shear and dilatational rheology), and their roles in controlling emulsion stability. Subsequently, the structural effects of a series of typically dietary emulsifiers (small-molecule surfactants,proteins, polysaccharides, protein-polysaccharide complexes, and particles) on oil-water interfaces in food emulsions are emphasized. Finally, the main protocols developed for modifying the structural characteristics of adsorbed emulsifiers at multiple scales and improving the stability of emulsions are highlighted. Overall, this paper aims to comprehensively study the literature findings in the past decade and find out the commonality of multi-scale structures of emulsifiers, so as to deeply understand the common characteristics and emulsification stability behaviour of adsorption emulsifiers with different interfacial layer structures. It is difficult to say that there has been significant progress in the underlying principles and technologies in the general science of emulsion stability over the last decade or two. However, the correlation between interfacial layer properties and physical stability of food emulsions promotes revealing the role of interfacial rheological properties in emulsion stability, providing guidance on controlling the bulk properties by tuning the interfacial layer functionality.

A functional spreadable canola and milk proteins oleogels as a healthy system for candy gummies

Recently, interest and demand for healthy and useful food products have become a global requirement. Thus, the production of functional foods with high polyunsaturated fatty acids and antioxidants is very challenging. In this study, four functional spreadable oleogels based on canola oil and milk proteins were developed. These spreadable oleogels were used as an innovative model for the preparation of candy gummies. The chemical composition, oxidative stability, and effects of storage conditions were studied. The results showed that the fat content in spreadable oleogels and gummies ranged from 35 to 47 and 2.40–4.15%, respectively. The protein content in spreadable doum and carrot was 7.41%, while it was 6.15% in the spreadable plain and ranged from 10.25 to 12.78% in gummies. The hardness of spreadable oleogels and gummies ranged from 0.3 to 0.9 and 6.22–16.30 N, respectively. Spreadable carrot and spreadable doum had peroxide values greater than 8 meqO₂/kg after storage, whereas spreadable plain and spreadable canola oleogel had better oxidative stability. The antioxidant activity of spreadable oleogels and gummies ranged from 66.98–46.83% to 51.44–40.37%, respectively. In addition, transmission electron microscopy and polarized light microscopy micrographs showed the presence of a coherent entangled network between oleogels and nutritional polymers. The oil binding capacity of spreadable carrot oleogel had a maximum value of 97.89%, while formed gummies were higher than 99%. This study showed a promising way to make functional spreadable oleogels as a model for food products that are good for health and nutrition.

Naphthalimide-Based Fluorescent Probe for Profiling of Aldehydes during Oxidation of Unsaturated Lipids

A lipophilic naphthalimide hydrazine fluorescent probe was successfully developed in this study for profiling aldehyde oxidation products. Dodecyl amine was applied to afford lipophilicity of the fluorescent probe for lipids. Investigation of fluorescence properties of the probe and condensation products with typical aldehydes including MDA and hexanal revealed significant enhancement of fluorescence intensity after condensation due to the inhibition of photo-induced electron transfer. MDA and hexanal could be differentiated by the probe through emission of different fluorescence colors (blue, MDA; green, hexanal). Eight major oxidation components including seven aldehydes were detected by the fluorescent probe coupled with high-performance liquid chromatography-mass spectrometry during aerobic oxidation of typical unsaturated lipids. Formation of these aldehyde oxidation products was rationalized through the radical oxidation mechanism. Detection of representative aldehyde products demonstrated the generality in the application of this fluorescent probe for profiling of aldehydes after lipid oxidation.

Stability of oil-in-water emulsions improved by ovalbumin-procyanidins mixture: A promising substrate with emulsifying and antioxidant activity

The aim of this study is to develop a dual-functional ingredient with antioxidant activity and emulsification. The emulsion stability of ovalbumin (OVA) was improved by procyanidins (PC). The interactions between OVA and PC were investigated using multi-spectroscopy and molecular docking. Furthermore, the effect of the addition of the OVA-PC mixture on emulsion stability was evaluated as well. The fluorescence results showed that the quenching mechanism of PC to OVA's endogenous fluorescence was static quenching, and the binding ratio of OVA and PC was 1:1. Circular dichroism (CD) and Fourier Transform Infrared Spectrometer (FT-IR) showed that the addition of PC promoted the unfolding of OVA, and transformed the secondary structure of OVA from α-helix to β-sheet. The main driving force of OVA and PC was hydrogen bonding, according to molecular docking analysis. Among all the samples, the stability of the emulsion of OVA-PC at a ratio of 1:30 exhibited extremely high stability and the smallest particle size. In comparison with individual OVA emulsions, the OVA-PC emulsions had excellent physical stabilities. Meanwhile, the oxidation degree of protein and oil for the OVA-PC emulsions was lower than that of the native OVA emulsion after 8-day storage. Our work provides important insights for understanding the interaction between OVA and expanding the application of OVA-PC.

Mixed Biopolymer Systems Based on Bovine and Caprine Caseins, Yeast β-Glucan, and Maltodextrin for Microencapsulating Lutein Dispersed in Emulsified Lipid Carriers

Lutein is an important antioxidant that quenches free radicals. The stability of lutein and hence compatibility for food fortification is a big challenge to the food industry. Encapsulation can be designed to protect lutein from the adverse environment (air, heat, light, pH). In this study, we determined the impact of mixed biopolymer systems based on bovine and caprine caseins, yeast β-glucan, and maltodextrin as wall systems for microencapsulating lutein dispersed in emulsified lipid carriers by spray drying. The performance of these wall systems at oil/water interfaces is a key factor affecting the encapsulation of lutein. The highest encapsulation efficiency (97.7%) was achieved from the lutein microcapsules prepared with the mixed biopolymer system of caprine αs1-II casein, yeast β-glucan, and maltodextrin. Casein type and storage time affected the stability of lutein. The stability of lutein was the highest (64.57%) in lutein microcapsules prepared with the mixed biopolymer system of caprine αs1-II casein, yeast β-glucan, and maltodextrin, whereas lutein microcapsules prepared with the biopolymer system of bovine casein, yeast β-glucan, and maltodextrin had the lowest (56.01%). The stability of lutein in the lutein microcapsules dramatically decreased during storage time. The antioxidant activity of lutein in the lutein microcapsules was closely associated with the lutein concentration.

Oxidative stability of Pickering emulsions

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Oxidative stability of O/W Pickering emulsions depends on their interfacial layer.

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Solid particles can reduce Pickering emulsion oxidation by creating a thick interface.

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Manipulating the charge of the interface can control Pickering emulsion oxidation.

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Adding antioxidants to solid particles can reduce oxidation in Pickering emulsions.

In recent years, Pickering emulsions have been the focus of growing interest because of their possible role as alternatives to conventional emulsions. Some reviews have investigated the physical stability of Pickering emulsions, but the oxidative stability of these emulsions remains largely unexplored. In this review, the oxidation mechanism and factors affecting lipid oxidation rates in Pickering emulsions are discussed. Then, different food-grade solid particles are evaluated for their ability to stabilize Pickering emulsions. Finally, several strategies are reviewed for improving the oxidative stability of Pickering emulsions. These strategies are based on efforts to manipulate the physical and chemical properties of the interfacial layer, increase the concentration of antioxidants at the interfacial layer through incorporating them into solid particles, cause oil droplets to crowd at high packing fractions, trap oil droplets in a gel network and increase the viscosity of the continuous phase.

Effect of pectin on the properties of nanoemulsions stabilized by sodium caseinate at neutral pH

The effect of different concentrations of low methoxyl pectin (LMP) on lipid oxidation and physical stability of sodium caseinate (CAS) stabilized nanoemulsions under neutral pH was investigated. The addition of pectin at low concentration (≤ 0.10 wt%) had no significant effect on the average size of nanoemulsions, but a slight size increase and phase separation were observed at higher concentrations of pectin (≥ 0.25 wt%). This result suggests that LMP can not adsorb at the oil/water interfacial CAS membrane at neutral pH. However, in the presence of LMP, the physical stability of nanoemulsions against high salt concentrations and freeze-thaw cycles was significantly enhanced. Moreover, nanoemulsions containing pectin have a better ability to inhibit lipid and protein oxidation than nanoemulsions without pectin after 3 weeks, and the lowest lipid hydroperoxide content was observed for nanoemulsions containing 0.25 wt% pectin.

Influence of β-glucan extracted from hull-less barley on droplet characterization, stability and rheological properties of soy protein isolate stabilized oil-in-water emulsions

In this study the effect of ultrasonically extracted β-glucan from hull-less barley (UBG, 0.25-0.75% w/w) on soy protein isolate (SPI, 4-12% w/w) stabilized oil-in-water emulsions was investigated. The results indicated that with increasing UBG concentration, zeta potential, droplets' specific surface area and emulsion stability increased; whereas, the surface and interfacial tensions, Sauter mean diameter (D_3,2) and the De Brouckere Mean Diameter (D_4,3), span value and creaming index decreased. Non-Newtonian shear-thinning (pseudoplastic) behavior was observed for oil-in-water emulsions stabilized by UBG. With increase in UBG and SPI concentrations, emulsion's flow behavior index (n) and consistency coefficient (k) increased and decreased; respectively. At all UBG and SPI concentrations, emulsions stored at 4 °C were more stable.

Limnophila aromatica Crude Extracts as Natural Emulsifiers for Formation and Stabilizing of Oil-in-Water (O/W) Emulsions

This study mainly focused on the emulsifying performance of Limnophila aromatica crude extracts obtained by using different ethanolic aqueous solutions (0, 25, 50, 75, and 99.5% (v/v)). All Limnophila aromatica extracts (LAEs) were able to produce emulsions with a volume mean droplet diameter (d4,3) ranging from 273 to 747 nm, except for LAE-99.5 (3269 nm). Only the emulsion prepared by LAE-75 was stable during seven days of storage, without significantly changing droplet size (479–495 nm). The result showed that all LAEs could reduce interfacial tension varied within 12.5 and 16.1 mN/m at the soybean oil/extracts (1% w/w) interface. Compared to other extracts, LAE-75 did not contain the highest protein, saponin, and phenol content (4.36%, 20.14%, and 11.68%, respectively), but it had the lowest ash content (14.74%). These results indicated that the emulsifying performance of LAEs did not rely only on interfacial tension and/or surface-active compounds. The residual demulsifiers, such as inorganic substances, were also significantly involved in the emulsions’ destabilization. Finally, the emulsion consisting of 0.5% (w/w) LAE-75 and 5% (w/w) soybean oil showed considerable stability during storage up to 30 days at different temperatures (5 or 25 °C). Therefore, Limnophila aromatica extract has a potential application as a new source of natural emulsifier.

Pickering emulsion stabilized by hydrolyzed starch: Effect of the molecular weight

HYPOTHESIS

The emulsifying ability of starch is influenced by its molecular weight. Reducing the molecular weight of starch is expected to influence interfacial adsorption and membrane elasticities, thereby affecting its emulsifying ability through Pickering effects. Hence, it should be possible to tailor the emulsifying ability of starch by adjusting its molecular weight.

EXPERIMENTS

Waxy corn starch (CS) and rice starch (RS) were hydrolyzed with pullulanase to obtain high (HM) and low molecular weight (LM) fractions. After the molecular weight was determined by size exclusion chromatography, the fractions were used to prepare model oil-in-water emulsions. The stability, microscopy, and particle size of the emulsions were characterized, and the underlying emulsification mechanism was subsequently studied through dynamic laser scattering, surface tension analysis, interfacial rheology, and Pearson's correlation calculations.

FINDINGS

In the molecular weight range obtained in this study, the smaller the molecular weight of starch, the stronger its emulsifying ability. The decrease in molecular weight resulted in considerable different adsorption and interfacial elasticities with smaller fractions occupying less area on the interface and forming interfaces with higher elasticities, resulting in higher stabilities through Pickering effects. Results thus suggest that the emulsifying ability of starch may be tailored by adjusting its molecular weight.

Proposed Methods for Testing and Comparing the Emulsifying Properties of Proteins from Animal, Plant, and Alternative Sources

The food industry is trying to reformulate many of its products to replace functional ingredients that are chemically synthesized or isolated from animal sources (such as meat, fish, eggs, or milk) with ingredients derived from plant or microbial sources. This effort is largely a result of the demand for foods that are better for the environment, human health, and animal welfare. Many new kinds of plant- or microbial-derived proteins are being isolated for potential utilization as functional ingredients by the food industry. A major challenge in this area is the lack of standardized methods to measure and compare the functional performance of proteins under conditions they might be used in food applications. This information is required to select the most appropriate protein for each application. In this article, we discuss the physicochemical principles of emulsifier functionality and then present a series of analytical tests that can be used to quantify the ability of proteins to form and stabilize emulsions. These tests include methods for characterizing the effectiveness of the proteins to promote the formation and stability of the small droplets generated during homogenization, as well as their ability to stabilize the droplets against aggregation under different conditions (e.g., pH, ionic composition, temperature, and shearing). This information should be useful to the food industry when it is trying to identify alternative proteins to replace existing emulsifiers in specific food applications.

Evaluation of the Physicochemical and Functional Properties of Aquasoya (Glycine max Merr.) Powder for Vegan Muffin Preparation

Recent concerns on health and sustainability have prompted the use of legumes as a source of plant-based proteins, resulting in the application of their cooking water as a substitute for egg whites. In this study, the cooking water of yellow soybeans was powdered, and, subsequently, the nutritional and functional characteristics of powders from yellow soybeans (YSP), chickpeas (CHP), and egg whites (EWP) were compared. The main components of these powders (total polyphenol, total carbohydrate, and protein), along with their hydration properties (hygroscopicity, water solubility index, and water/oil holding capacities), and emulsifying and foaming properties, were identified. The muffins prepared with YSP, CHP, and EWP were analyzed to determine their basic characteristics, such as volume, baking loss, and sensory attributes. The results of the powder analyses indicated that YSP was significantly superior to CHP and EWP, particularly in terms of holding capacities, and emulsion and foam stabilities. The sensory evaluation results showed that there was no statistically significant difference in overall acceptance among the muffin samples. Therefore, YSP can be used as an alternative to CHP or EWP, and applied as a novel ingredient in various vegan products.

Faba bean protein: A promising plant-based emulsifier for improving physical and oxidative stabilities of oil-in-water emulsions

Faba bean is a protein-rich, sustainable, but understudied legume. Faba bean protein isolates (FBPIs) can serve as promising emulsifiers. This review aims to summarize the research on FBPIs as emulsifiers and various modification methods to improve the emulsifying functionalities. The emulsifying activities of FBPIs depend on several physiochemical characteristics (e.g. solubility, surface hydrophobicity, surface charge, interfacial activity). Physical modifications, especially via linking FBPIs electrostatically to polysaccharides can effectively increase the interfacial layer thickness/compactness and maintain the interfacial protein adsorption. Chemical modifications of FBPIs (e.g. acetylation and Maillard reaction) could improve the interfacial activity and affect the droplet-size distribution. Enzymatic modifications, usually either via hydrolysis or cross-linking, help to optimize the molecular size, solubility, and surface hydrophobicity of FBPIs. It is critical to consider the lipid/protein oxidative stability and physical stability when optimizing the emulsifying functionality of FBPIs. With suitable modifications, FBPI can serve as a promising emulsifier in food production.

Innovative and Sustainable Technologies to Enhance the Oxidative Stability of Vegetable Oils

To meet consumers’ demand for natural foods, edible oil producers and food processing industries are searching for alternatives to synthetic antioxidants to protect oils against oxidation. Antioxidant compounds extracted from different plant parts (e.g., flowers, leaves, roots, and seeds) or sourced from agri-food industries, including residues left after food processing, attract consumers for their health properties and natural origins. This review, starting from a literature research analysis, highlights the role of natural antioxidants in the protection of edible oils against oxidation, with an emphasis on the emerging and sustainable strategies to preserve oils against oxidative damage. Sustainability and health are the main concerns of food processing industries. In this context, the aim of this review is to highlight the emerging strategies for the enrichment of edible oils with biomolecules or extracts recovered from plant sources. The use of extracts obtained from vegetable wastes and by-products and the blending with oils extracted from various oil-bearing seeds is also pointed out as a sustainable approach. The safety concerns linked to the use of natural antioxidants for human health are also discussed. This review, using a multidisciplinary approach, provides an updated overview of the chemical, technological, sustainability, and safety aspects linked to oil protection.

Physical and Oxidative Stability of Low-Fat Fish Oil-in-Water Emulsions Stabilized with Black Soldier Fly (Hermetia illucens) Larvae Protein Concentrate

The physical and oxidative stability of fish oil-in-water (O/W) emulsions were investigated using black soldier fly larvae (BSFL) (Hermetia illucens) protein concentrate as an emulsifier. To improve the protein extraction and the techno-functionality, defatted BSFL powder was treated with ohmic heating (BSFL-OH) and a combination of ohmic heating and ultrasound (BSFL-UOH). Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were performed in order to characterize the secondary structure and thermal stability of all protein concentrate samples. The interfacial properties were evaluated by the pendant drop technique. The lowest interfacial tension (12.95 mN/m) after 30 min was observed for BSFL-OH. Dynamic light scattering, ζ-potential and turbiscan stability index (TSI) were used to evaluate the physical stability of emulsions. BSFL-OH showed the smallest droplet size (0.68 μm) and the best emulsion stability (TSI = 8.89). The formation of primary and secondary volatile oxidation products and consumption of tocopherols were evaluated for all emulsions, revealing that OH and ultrasound treatment did not improve oxidative stability compared to the emulsion with untreated BSFL. The results revealed the promising application of BSFL proteins as emulsifiers and the ability of ohmic heating to improve the emulsifying properties of BSFL proteins.

Lipid oxidation in emulsions and bulk oils: a review of the importance of micelles

Lipid oxidation is a major cause of quality deterioration in food products. In these foods, lipids are often present in a bulk or in emulsified forms. In both systems, the rate, extent and pathway of oxidation are highly dependent on the presence of colloidal structures and interfaces because these are the locations where oxidation normally occurs. In bulk oils, reverse micelles (association colloids) are present and are believed to play a crucial role on lipid oxidation. Conversely, in emulsions, surfactant micelles are present that also play a major role in lipid oxidation pathways. After a brief description of lipid oxidation and antioxidants mechanisms, this review discusses the current understanding of the influence of micellar structures on lipid oxidation. In particular, is discussed the major impact of the presence of micelles in emulsions, or reverse micelles (association colloids) in bulk oil on the oxidative stability of both systems. Indeed, both micelles in emulsions and associate colloids in bulk oils are discussed in this review as nanoscale structures that can serve as reservoirs of antioxidants and pro-oxidants and are involved in their transport within the concerned system. Their role as nanoreactors where lipid oxidation reactions occur is also commented.

Antioxidant and prooxidant activities of tea polyphenols in oil-in-water emulsions depend on the level used and the location of proteins

We studied the impacts of protein location (interface or aqueous phase) on the antioxidant and prooxidant activities of tea polyphenols (TP) in model oil-in-water emulsions (pH 7) at a low (0.01% w/v) or high (0.04 % w/v) concentration. TP at 0.01% reduced the levels of both lipid and protein oxidation markers in emulsions, independent of the protein location. However, TP were more potent when proteins were located at the interface. At 0.04%, TP were only weakly antioxidant towards lipids but were prooxidant towards proteins in emulsions with proteins at the interface, whereas they were still somewhat antioxidant for aqueous phase proteins. These results indicate that TP may act as either antioxidants or prooxidants depending on their concentration and also on the location of the proteins in emulsions. The level of TP should be optimized for emulsion-based foods or beverages to achieve optimum antioxidant activity.

Characterization and stability of peppermint oil emulsions using polyglycerol esters of fatty acids and milk proteins as emulsifiers

Three peppermint oil emulsions using polyglycerol esters of fatty acids-casein (PGFE-CN), polyglycerol esters of fatty acids-sodium caseinate (PGFE-NaCN), and polyglycerol esters of fatty acids-whey protein isolate (PGFE-WPI) as emulsifiers were fabricated, and the droplet size, zeta potential, viscosity, and stability of emulsions were determined. The experimental results showed that the emulsion containing PGFE-CN has relatively smaller droplet size of 231.77 ± 0.49 nm. No significant changes were observed on the average particle size, polydispersity index and zeta potential during 4-week of storage, indicating that the emulsions kept stable against pH, salt ion, freeze-thaw, and storage. Fourier transform infrared spectrometer (FTIR) results showed that the electrostatic interaction occurs between CN and PGFE in the emulsion. The confocal laser scanning microscope (CLSM) was used to observe the microstructure of the emulsion, proving that droplets were evenly distributed throughout the aqueous phase by PGFE-CN emulsifier. The protein-stabilized emulsions can be used as potential carriers for the delivery of the lipophilic nutrients such as peppermint oil. PRACTICAL APPLICATION: PGFE-CN emulsifier can be directly added to the beverage systems containing oil or protein, such as coconut milk, peanut milk, and walnut milk. It can enhance the stability of beverage, prevent the precipitation, stratification, and oil floating, improve the homogeneity of the system and therefore extend the shelf life.

Electrical conductivity: A simple and sensitive method to determine emulsifying capacity of proteins

Emulsifying capacity (EC) of proteins is a benchmark standard widely used to evaluate the quality of protein ingredients in emulsion foods. EC (mL of oil emulsified per g of protein) is usually measured by a sudden drop in electrical resistance (phase transition) with the continuous addition of oil to a specific protein solution. However, little is known about electrochemical mechanisms behind this process because resistance, measured with an ohmmeter, is not sensitive enough to monitor changes in the concentration of protein electrolytes. Here, pea (PPI), myofibrillar (MPI), and whey (WPI) protein isolates were vigorously homogenized with oil at a series of oil/protein ratios to prepare emulsions with different final protein concentrations. The conductivity was closely monitored using a conductivity meter. A linear relationship was discovered between conductivity and the final protein concentrations. At higher oil fractions, the migration of proteins from the aqueous phase to the oil-water interface limited protein mobility, leading to a conductivity drop. EC was calculated from the regression lines; when the starting protein concentration was raised from 0.5% to 2.0%, the EC of PPI, MPI, and WPI decreased from 717, 782, 1339 to 219, 303, and 540 mL oil/g protein, respectively. The dependence of EC on the initial protein concentration and the sensitivity of conductivity to the depleting protein electrolytes suggest that protein concentration is an important factor to consider when determining EC for a given protein or comparing EC among different proteins. PRACTICAL APPLICATION: The simple and sensitive electrical conductivity test described in this paper allows for the accurate determination of emulsifying capacity of proteins. It may be adopted by the food industry to compare the emulsifying properties of different protein ingredients.