Physical Stability Of Emulsions Research Articles

Fabrication and characterization of Zanthoxylum schinifolium essential oil Pickering emulsion stabilized by bacterial cellulose nanofibrils/whey protein isolate complexes and fortified with cinnamaldehyde

The inherent hydrophobicity, high volatility, instability and pungent flavor of Zanthoxylum schinifolium essential oil (ZSEO) are important issues to restrict its preservation and practical applications. To overcome these drawbacks, the ZSEO-loaded Pickering emulsions stabilized by bacterial cellulose nanofibrils/whey protein isolate (BCNFs/WPI) complexes and fortified with cinnamaldehyde (CA) were fabricated, and their physical property and functionality were characterized. When the concentration of BCNFs/WPI complexes was 0.7 wt%, the emulsions had the smallest and uniform droplet size (<150 nm) and showed good stability over 30 d storage. Moreover, the emulsions with different CA contents (0–1.0 wt%) maintained a long-term stability with no significant droplet size change during 30 d storage. All Pickering emulsions showed a shear-thinning behavior, and their apparent viscosity and viscoelastic moduli gradually increased with the increase of BCNFs/WPI complexes contents. The presence of CA enhanced the physical stability of emulsions against environmental stresses such as acid, heat and salinity. Compared to free ZSEO, the ZSEO-loaded Pickering emulsions fortified with CA not only improved the stability of ZSEO, but also maintained or even enhanced its antioxidant and antimicrobial activity. This study would provide a promising strategy for ZSEO encapsulation and improve its stability and functionality in food applications.

The physicochemical properties and emulsion performance of different fractions from rice glutelin fibrils

Herein, oil in water emulsion was prepared by the different fractions from rice glutelin fibrils after centrifugal filtration. The morphology and physicochemical properties of retentates (RGFs), filtrates (FGFs), and total heated samples of amyloid fibrils from rice glutelin (TGFs) were characterized. As the oil fraction increased, the viscosity of TGFs-, RGFs- and FGFs-prepared emulsions increased, and the emulsions at φ = 0.7 exhibited the best stability. Compared to others, the RGFs stabilized emulsion showed a self-standing behavior, highest modulus (G′ of 1185 Pa and G″ of 211 Pa) and viscosity (6873 Pa s), due to the formation of dense interfaced layer. However, the hydrophilic FGFs particles cannot bind strongly to the interface after adsorption, resulting in a lower physical stability of emulsion. The TGFs-stabilized emulsion exhibited better centrifugation stability than other samples. These findings will provide further information into the tunable applications of different fractions from rice glutelin fibrils in food systems.

Combination of legume proteins and arabinoxylans are efficient emulsifiers to promote vitamin E bioaccessibility during digestion

The emulsification potential of plant-based emulsifiers, that is, pea (PPI) and lentil (LPI) proteins (4%), corn arabinoxylans (CAX, 1%), and legume protein-arabinoxylan mixtures (4% proteins + 0.15 or 0.9% CAX), was evaluated by assessing: the surface tension and potential of emulsifiers, emulsifier antinutritional contents, emulsion droplet size, emulsion physical stability, and vitamin E bioaccessibility from 10% oil-in-water emulsions. Tween 80 (2%) was used as a control. All emulsions presented small droplet sizes, both fresh and upon storage, except 4% LPI + 0.9% CAX emulsion that exhibited bigger droplet sizes (d(4,3) of approximately 18.76 μm vs 0.59 μm for the control) because of droplet bridging. Vitamin E bioaccessibility from emulsions stabilized with the combination of 4% PPI and either 0.15% or 0.9% CAX (28 ± 4.48% and 28.42 ± 3.87%, respectively) was not significantly different from that of emulsions stabilized with Tween 80 (43.56 ± 3.71%), whereas vitamin E bioaccessibility from emulsions stabilized with individual emulsifiers was significantly lower.

Combined effects of high-intensity ultrasound treatment and hydrogen peroxide addition on the thermal stabilities of myofibrillar protein emulsions at low ionic strengths

In this study, the effects of high-intensity ultrasound (HIU) treatment combined with hydrogen peroxide (H2O2) addition on the thermal stability of myofibrillar protein (MP)–stabilized emulsions in low-salt conditions were investigated. Results showed that compared to using either HIU or H2O2 treatment alone, HIU treatment combined with H2O2 was most effective in enhancing the physical stability of emulsions. Moreover, the emulsion stabilized by MPs co-treated with HIU and H2O2 exhibited the most uniform distribution, highest absolute zeta potential, and optimal rheological properties upon heating. This combination effect during heating was caused by the inhibition of disulfide bond cross-linking of myosin heads by H2O2 and the dissociation of filamentous myosin structures using the HIU treatment. In addition, the results of oxidative stability analysis indicated that the addition of H2O2 increased the content of oxidation products; however, the overall influence on the oxidative stability of emulsions was not significant. In conclusion, the combination of HIU and H2O2 treatment is a promising approach to suppress heat-induced MP aggregation and improve the thermal stability of corresponding emulsions.

Possible application of green algae as emulsifiers in foods and nutritional supplements

The high protein content (43.4 %) and the ability of dietary fiber in Spirulina (Arthrospira platensis) to retain water or vegetable oil make the alga suitable for use as an emulsifier in colloidal or emulsion systems. This study aimed to investigate the influence of Spirulina (Arthrospira platensis) (4%, 8%, 12%) as emulsifier on the physical and thermodynamic stability of model emulsions by determining parameters such as Gibbs energy, enthalpy, and entropy. Thermodynamic stability was estimated spectrophotometrically, and physical stability was determined by the Kozin method. It was shown that increasing the Spirulina concentration leads to a decrease in Gibbs free energy and an increase in the physical stability of all emulsions (20%, 40%, 60% oil phases) that are finely dispersed and microscopically determined. The highest percentage of retained emulsion (100 %) was at 12 % Spirulina with an oil phase content of 40 % or 60 %. From a rheological point of view, emulsions with Spirulina at 20 % oil phase showed plastic body behavior, and those with 40 % and 60 % oil phase showed pseudo-plastic behavior.

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.

A novel strategy for improving the stability of myofibrillar protein emulsions at low ionic strength using high-intensity ultrasound combined with non-enzymatic glycation

Poor emulsification of myofibrillar proteins (MPs) limits the production of meat protein emulsion-type products, and it is related to the myosin self-assembles in low-salt settings. The effect of high-intensity ultrasound (HIU) pretreatment combined with non-enzymatic glycation on MP-stabilized emulsions in low-salt settings was investigated in this study, and the potential mechanism was revealed. The results indicated that, compared to using either HIU or glycation treatment alone, HIU pretreatment in combination with glycation significantly improves the physical stability of emulsions while increasing the distribution uniformity and reducing the droplet particle size from 18.05 μm to 2.54 μm (P < 0.05). Correspondingly, the emulsion prepared using this approach exhibited a relatively high absolute zeta potential (−23.58 mV) and a high interfacial protein content (38.78 %) (P < 0.05), promoting molecular rearrangement and forming a continuous and stable interfacial layer. HIU pretreatment combined with glycation could offer reinforced electrostatic repulsion and steric hindrance to depolymerize self-assembled filamentous polymers, thus enhancing the stability of droplets. Additionally, the thermal sensitivity of the glycated MPs pretreated by HIU was remarkably reduced, thus improving the thermal stability of the corresponding emulsions.

FLUID PROPERTIES OF COMPONENTS FOR DEVELOPMENT OF EUDRAGIT RS-BASED IN SITU-FORMING GEL AND MICROPARTICLE AND THEIR PHASE INVERSIONS

Solvent exchange-induced in situ-forming gel (isg) and in situ-forming microparticles (ism) have been currently applied as drug delivery approaches for periodontitis treatment. Doxycycline hyclate-loaded Eudragit RS-based isg and ism were prepared in this study. The basic properties such as density, pH, surface/interfacial tension of their solvents including dimethyl sulfoxide (DMSO), N-methyl pyrrolidone (NMP), and 2-pyrrolidone (PYR) in Eudragit RS solution and oils (olive oil and camellia oil) were assessed. This research also tested for apparent viscosity of solvent and drug-free and doxycycline hyclate-loaded ERS-based isg and ism, and their phase transformation rates. Density of PYR was higher than that of DMSO whereas these solvents exhibited the less wettability than oils on glass slide. All fabricated doxycycline hyclate-loaded Eudragit RS-based ism formulations showed good emulsion physical stability with no phase separation for 1 hour. The apparent viscosity of ism was significantly less than that of isg. DMSO-based isg and ism exhibited a significantly less viscosity than that of PYR-based formulations. Rapid phase inversion was evident after isg and ism exposure to agarose gel indicating fast solvent exchange. The loose barrier of camellia oil from its less viscosity facilitated a water diffusion inward Eudragit RS-based ism easier than using viscous olive oil. Solvent exchange-induced doxycycline hyclate-loaded Eudragit RS-based ism using DMSO as the solvent and camellia oil as the continuous phase exhibited various appropriate physicochemical characteristics for applying as drug delivery system for periodontitis treatment.

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 5days 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.

Enhanced O/W emulsion stability and betanin protection using yeast protein and chitooligosaccharide: Comparative insights from complex coacervation and layer-by-layer methods

Emulsions play a pivotal role in food and related industries, yet oil-in-water (O/W) emulsions, a staple emulsion, are plagued by instability issues like aggregation, flocculation, and gravitational separation during storage. Stabilizing these emulsions has often involved the use of proteins or polysaccharides. Within this context, this research delves into comparing two distinctive stabilization strategies for emulsions. The yeast protein (YP), chitooligosaccharide (COS), and betanin were employed to formulate a complexation emulsion (CE) using a complex coacervation method, and a bilayer emulsion (BE) through a layer-by-layer method. The effects of these divergent methods on the emulsion's physicochemical properties, microscopic structure, and the stability of betanin was assessed. The findings indicate that the yeast protein-chitooligosaccharide-betanin (YCB) emulsion prepared using the layer-by-layer method demonstrated the smallest droplet size and the greatest absolute ζ-potential. After a storage period of seven days, this emulsion showed the lowest emulsification index, indicating excellent storage stability. In tandem, an increase in apparent viscosity was observed, with the emulsion exhibiting weak gel-like behavior. The incorporation of betanin has improved the physical stability of emulsions, and concurrently, the emulsion presented an improved storage stability of betanin. These results provide insightful perspectives for the development of emulsions based on bilayer interfaces, contributing to the expansion of novel fungal protein applications in the fields of emulsion technology, food processing, and the stabilization of bioactive molecules.

Effect of composition of emulsifier blends on aerated emulsions: Stability, thermodynamic, interfacial behavior and aeration properties

In this study, we investigated the effect of emulsifier blends with different structures and lipophilic-hydrophilic balance (HLB) on the interfacial composition and crystallization behavior, as well as on the aeration properties of emulsions. The droplet size, physical stability, rheological properties, and partial aggregation rate of the quiescent emulsions were determined. Further, the interfacial protein content, interfacial tension, interfacial rheological properties, and thermodynamic properties were analyzed, and the aeration and texture of the foams were recorded. First, there was a significant difference in emulsion droplet size after compounding with glyceryl monostearate (GM) even though sucrose ester S-1570 (SE) and polysorbate 80 (TW) had the same HLB (p < 0.05), but sorbitan monooleate 80 (SP)-TW performed consistently with GM-TW, having the smallest particle size. Secondly, the addition of GM-SE changed the thermodynamic properties and significantly increased the crystallization temperature of fat (15.79 °C), but had no significant effect on the aeration process. In addition, although GM-SE resulted in emulsions with the lowest interfacial tension, the fat globule surface exhibited viscous behavior (E' < E″) and the worst physical stability of the emulsion, while triglycerol monostearate (TMS)-TW balanced the interfacial tension and strength giving good performance in both emulsion stability and aeration characteristics. In general, the design of compounding emulsifiers should pay more attention to the structural of the emulsifier. These results provide an interesting point of departure for further development of compounding emulsifiers for different needs.

Underlying mechanisms and effects of EGCG on the interfacial composition and protein-lipid co-oxidation of whey protein isolate-stabilised O/W emulsions

Addition of different (−)-epigallocatechin-3-gallate (EGCG) (0, 100, 200, 500 or 1000 mg/L emulsion) on the interfacial composition and protein-lipid co-oxidation of whey protein isolate (WPI)-stabilised oil-in-water (O/W) emulsions were studied, and underlying mechanisms were also explored. The results indicated that the physical stability of emulsions gradually decreased with the increasing level of EGCG during storage, which clearly verified by decreasing ζ-potential absolute values and increasing droplet size. Moreover, the combination between WPI and EGCG by covalent/non-covalent binding for either adsorbed proteins (AP) or unadsorbed proteins (UAP) led to aggregation and conformational changes in WPI, which confirmed and characterised by electrophoresis, fluorescence quenching, and molecular docking simulation. Meanwhile, the concentration of AP slightly decreased as a function of EGCG level and storage time, however, the UAP showed the opposite change tendency, indicating that EGCG could effectively modulate the interfacial adsorption property of WPI in O/W emulsions. In addition, the incorporation of EGCG efficiently suppressed protein-lipid co-oxidation of O/W emulsions during storage, which was illustrated by hierarchical cluster and correlation analysis between protein and lipid oxidation products. Our results clearly revealed the viability of the EGCG to modulate the interfacial composition and retard the co-oxidation of O/W emulsions with enhanced storability.

Molecular mechanisms affecting the stability of high internal phase emulsions of zein-soy isoflavone complexes fabricated with ultrasound-assisted dynamic high-pressure microfluidization

In this study, zein-soy isoflavone complex (ZSI) emulsifiers were fabricated using ultrasound-assisted dynamic high-pressure micro fluidization to stabilise highinternal phase pickering emulsions. Ultrasound-assisted dynamic high-pressure micro-fluidization enhanced surface hydrophobicity, zeta potential, and soy isoflavone binding capacity, while it decreased particle size, especially during ultrasound and subsequent microfluidization. The treated ZSI could produce small droplet clusters and gel-like structures, with excellent viscoelasticity, thixotropy and creaming stability owing to their neutral contact angles. Ultrasound and subsequent micro fluidization treatment of the ZSI complexes were highly effective in preventing droplet flocculation and coalescence after long-term storage or centrifugation due to their higher surface load, thicker multi-layer interfacial structure, and stronger electronic repulsion between the oil droplets. This study provides insights and extends our current knowledge of how non-thermal technology affects the interfacial distribution of plant based particles and the physical stability of emulsions.

Binary complexes of whey protein fibers/isolates and fish gelatins for emulsion stabilization

In this work, fish gelatins (FG) were mixed with whey protein fibers (WPF) and native whey protein isolates (WPI) under acidic and neutral pH conditions, respectively. The objective of this study was to explore how binary protein FG and WPI/WPF cooperated to stabilize oil-in-water emulsion systems. The emulsion, stabilized solely by WPI, flocculated and coalesced easily at both pH values. Fibrillation could increase surface hydrophobicity and interfacial activity at pH 7, resulting in improved creaming stability of emulsions compared to natural WPI. However, the improvement in creaming stability was limited. When FG cooperated with WPI and WPF, FG could contribute to the formation of a 3D network to enhance the physical stability of emulsions. In addition, WPI and WPF could contribute to surface activity in binary proteins. FG-WPF exhibited better compatibility than FG-WPI and a faster gelation rate, superior viscoelastic properties, and greater deformation resistance. In addition, WPF may help to improve the gelation behavior of FG-WPF at pH 3. This research introduced a new binary protein system consisting of whey protein fibers and fish gelatins that might be used as promising emulsifiers and stabilizers in emulsion systems.

Pectin emulsions and emulgels: Bridging the correlation between rheology and microstructure

Pectin stabilized emulgel was fabricated following an emulsion guided approach. Properties of emulgel strongly depend on the properties of the emulsion which in turn is affected by the emulsifier (gelator). Fabrication of emulsion (20–40% oil v/v) using pectin isolated from passion fruit rind (2.0–4.0% w/v) was investigated to understand the changes in structural and rheological features on transformation from emulsion to emulgel. Passion fruit rind pectin demonstrated excellent emulsifying capacity by lowering the interfacial tension to 6 mN/m (for 4% w/v of pectin) of water and oil from an initial value of 12 mN/m. Concentration of pectin and the proportion of oil phase with respect to the water phase have a direct and inverse effect, respectively, on the physical stability of emulsion. Rheological evaluation showed yield stress for both emulsion and emulgel. Emulsion with 4% w/v of pectin and 20% v/v of oil was the most stable. Yield stress, yield strain and elastic modulus were found to increase on converting the emulsion to emulgel. Microstructure has given evidences of droplet aggregate formation and droplet entrapment inside the biopolymer matrix on emulgel formation. This study paves way towards understanding design, macroscopic properties and structure of sustainable fat substitutes for commercial purposes.

Physical and Oxidative Stabilization of Oil-In-Water Emulsions by Roasted Coffee Fractions: Interface- and Continuous Phase-Related Effects.

Emulsions fortified with polyunsaturated fatty acids are highly relevant from a nutritional perspective; however, such products are prone to lipid oxidation. In the current work, this is mitigated by the use of natural antioxidants occurring in coffee. Coffee fractions with different molecular weights were extracted from roasted coffee beans. These components were positioned either at the interface or in the continuous phase of emulsions where they contributed to emulsion stability via different pathways. Coffee brew as a whole, and its high-molecular-weight fraction (HMWF), was able to form emulsions with good physical stability and excellent oxidative stability. When added post-homogenization to the continuous phase of dairy protein-stabilized emulsions, all coffee fractions were able to slow down lipid oxidation considerably without altering the physical stability of emulsions, though HMWF was more effective in retarding lipid oxidation than whole coffee brew or low-molecular-weight fraction. This is caused by various effects, such as the antioxidant properties of coffee extracts, the partitioning of components in the emulsions, and the nature of the phenolic compounds. Our research shows that coffee extracts can be used effectively as multifunctional stabilizers in dispersed systems leading to emulsion products with high chemical and physical stability.

Pickering emulsion co‐stabilised by cellulose nanocrystals and astragalin/tangeretin: effect of environmental factors

SummaryThis study aims to reveal the stability of cellulose nanocrystals (CNCs) and astragalin/tangeretin co‐stabilised Pickering emulsion under different environmental factors such as ionic strengths, pH values, thermal treatment, freeze–thaw treatment, sodium ascorbate, and storage condition. Results showed that the astragalin and CNCs co‐stabilised Pickering emulsion (AST‐CPE) could maintain a stable appearance, typical spherical morphology droplets, and steady physical stability under various conditions, including ionic strength at low 20 mm, pH values 2–8, thermal treatment (65, 85, and 135 °C), the addition of sodium ascorbate, and storage at 4 °C for 35 days. It is noteworthy that AST‐CPE showed higher emulsion physical stability at pH 2 (56.67%) and pH 8 (53.33%). The co‐stabilised Pickering emulsion structure has a firm and physically stable system. Moreover, it could effectively protect the bioactive substance by expanding its application in food delivery vehicles.

Effects of high pressure processing on structure and emulsifying properties of lactoferrin-xanthan gum complex

The influence of high pressure processing (HPP) and polysaccharides on the structure and emulsifying properties of lactoferrin (LF) has been investigated by fluorescence, circular dichroism, FTIR, dynamic light scattering, physical stability, confocal laser scanning microscopy, and microrheology measurements. Compared with LF alone, the presence of xanthan gum (XG) inhibited the exposure of hydrophobic core in LF caused by HPP to a certain extent. HPP slightly changed the secondary structure of LF, while the addition of XG expanded the effect. 200 MPa treatment was favorable for LF-XG complexes to form ordered structure, while higher pressure decreased the content of α-helix. HPP treatment or XG addition both led LF molecules to unfold, while the combination of them caused LF to fold under certain conditions. Droplet sizes of LF-XG stabilized emulsions were smallest under 400 MPa. HPP increased the charges on the surface of droplets. HPP caused the oil droplets closer to spherical, more evenly distributed and reduced the flocculation among droplets. The Addition of 0.3 wt% XG or combination of 0.2 wt% XG and HPP could maximize the physical stability of emulsions. By altering the molecular structure of LF or LF-XG, HPP, and XG increased the viscoelasticity of emulsions.

Effect of salt treatment on the stabilization of Pickering emulsions prepared with rice bran protein

In this study, salt addition (NaCl and CaCl2) was utilized to improve the stability of emulsions formed by rice bran protein (RBP). The result showed that salt addition improved the adsorption of protein on the oil–water interface and enhanced the physical stability of emulsions. Compared to NaCl condition, emulsions with CaCl2 (especially 200 mM) addition exhibited more significant storage stability, as microscopy images showed emulsion structure unchanged and droplet size increasing slightly from 12.02 µm to 16.04 µm in 7 days. It was attributed to the strengthened particle complexation with CaCl2 and the increased hydrophobic interactions, which is explained by the improved particle size (260.93 nm), surface hydrophobicity (1890.10) and fluorescence intensity, thus inducing dense and hardly destroyed interfacial layers. Rheological behavior analyses suggested that salt-induced emulsions had higher viscoelasticity and maintained a stable gel-like structure. The result of study explored the mechanism of salt treated protein particles, developed a further understanding of Pickering emulsion, and was beneficial to the application of RBP.

Effect of enzyme types on emulsifying properties of walnut emulsion

In order to explore the efficient investigate and utilization of emulsion produced by enzyme-assisted aqueous extraction of walnut oil, the effects of different enzyme treatment (including Alcalase 2.4L, Ban 480L α-amylase, Neutrase 0.8L, Pectinex SP-L, Celluclast 1.5L) on the characteristics of emulsion were studied to characterize its emulsifying characteristics The emulsion composition, particle size distribution, Zeta potential, rheological properties and protein surface hydrophobicity of emulsion were determined to characterize its emulsifying properties. The results showed that the particle size of the emulsion obtained from enzymatic hydrolysis showed a smaller trend and the absolute value of Zeta potential showed a larger trend in the presence of enzymes. On emulsion protein, hydrophobicity of emulsion protein was obtained by hydrolysis with different enzymes showed that the trend followed the order: Celluclast 1.5L> Ban 480L >Neutrase 0.8L >Pectinex SP-L >control> Alcalase 2.4L. The particle size, zeta potential, ability to increase emulsion viscosity and interfacial hydrophobicity of emulsion proteins affected the emulsion physical stability and the effect of demulsification. The results of rheological analysis show that emulsions from Ban 480L α-amylase, Neutrase 0.8L and Celluclast 1.5L hydrolysate still maintained their elastic structure damaged by shear rate and were more stable, and the emulsions obtained by Alcalase 2.4L and Pectinex SP-L were unstable which was easy to be broken.