Phase Inversion Emulsification Research Articles

Physicochemical Properties and Functionalities of Food Emulsifiers

Purpose: This study sought to analyze the physiochemical properties and functionalities of food emulsifiers. Methodology: The study adopted a desktop research methodology. Desk research refers to secondary data or that which can be collected without fieldwork. Desk research is basically involved in collecting data from existing resources hence it is often considered a low cost technique as compared to field research, as the main cost is involved in executive’s time, telephone charges and directories. Thus, the study relied on already published studies, reports and statistics. This secondary data was easily accessed through the online journals and library. Findings: The findings reveal that there exists a contextual and methodological gap relating to the physiochemical properties and functionalities of food emulsifiers. Preliminary empirical review revealed that the importance of considering emulsifier properties in food product development. The findings underscored the significance of optimizing emulsifier selection and formulation to meet consumer demands for healthier, more sustainable, and better-performing food products. Continued research in this area promises to drive further innovation and advancements in food technology. Unique Contribution to Theory, Practice and Policy: The Interfacial Tension theory, HLB (Hydrophilic- Lipophilic Balance) theory and Emulsion Phase Inversion theory may be used to anchor future studies on the physiochemical properties and functionalities of food emulsifiers. The study made significant contributions to theoretical understanding, practical application, and policy considerations in the field of food science and technology. It advanced theoretical knowledge by exploring molecular mechanisms and integrating principles from colloid and interface science. In practice, the study recommended systematic approaches for emulsifier selection and process optimization to enhance product quality and consistency. From a policy perspective, it emphasized the importance of regulatory guidelines and transparency in emulsifier usage. Additionally, the study advocated for sustainability, innovation, and consumer-centric approaches to promote environmental responsibility, drive technological advancements, and prioritize consumer well-being in emulsifier research and application.

Fabrication of Eco-Friendly Hydrolyzed Ethylene-Maleic Anhydride Copolymer-Avermectin Nanoemulsion with High Stability, Adhesion Property, pH, and Temperature-Responsive Releasing Behaviors.

In this study, novel amphiphilic polymer emulsifiers for avermectin (Avm) were synthesized facilely via the hydrolysis of ethylene-maleic anhydride copolymer (EMA) with different agents, and their structures were confirmed by various techniques. Then, water-based Avm-nanoemulsions were fabricated with the emulsifiers via phase inversion emulsification process, and superior emulsifier was selected via the emulsification effects. Using the superior emulsifier, an optimal Avm-nanoemulsion (defined as Avm@HEMA) with satisfying particle size of 156.8 ± 4.9 nm, encapsulation efficiency (EE) of 69.72 ± 4.01% and drug loading capacity (DLC) of 54.93 ± 1.12% was constructed based on response surface methodology (RSM). Owing to the emulsifier, the Avm@HEMA showed a series of advantages, including high stability, ultraviolet resistance, low surface tension, good spreading and high affinity to different leaves. Additionally, compared to pure Avm and Avm-emulsifiable concentrate (Avm-EC), Avm@HEMA displayed a controlled releasing feature. The encapsulated Avm was released quite slowly at normal conditions (pH 7.0, 25 °C or 15 °C) but could be released at an accelerated rate in weak acid (pH 5.5) or weak alkali (pH 8.5) media or at high temperature (40 °C). The drug releasing profiles of Avm@HEMA fit the Korsmeyer-Peppas model quite well at pH 7.0 and 25 °C (controlled by Fickian diffusion) and at pH 7.0 and 10 °C (controlled by non-Fickian diffusion), while it fits the logistic model under other conditions (pH 5.5 and 25 °C, pH 8.5 and 25 °C, pH 7.0 and 40 °C).

Synthesis and characterization of comb structure polyether acrylate silicone softener for cotton fabrics

In this study, a comb-like structured organosilicon softener, PEMMS, was synthesised and the optimum synthesis conditions were determined. The chemical structure and properties of PEMMS were characterized by 1H NMR, FT-IR and TG. The emulsion system based on PEMMS was prepared by a phase inversion emulsification method, and the optimum parameters with excellent stability were selected. The surface properties of the emulsion were investigated using the maximum bubble pressure method to determine the CMC (16.61 g/L). The application of the PEMMS-based emulsion on cotton fabrics was studied. The results show that the silicone-treated cotton fabrics have improved wettability, hydrophilicity and softness. In addition, their whiteness remains essentially unchanged, indicating a certain degree of resistance to yellowing. This simplified preparation of a high performance softener is crucial in lowering production costs and improving the safety of the production process.

The Phase Inversion Mechanism of the pH-Sensitive Reversible Invert Emulsion.

Reversible emulsification drilling fluids can achieve conversion between oil-based drilling fluids and water-based drilling fluids at different stages of drilling and completion, combining the advantages of both to achieve the desired drilling and completion effects. The foundation of reversible emulsion drilling fluids lies in reversible emulsions, and the core of a reversible emulsion is the reversible emulsifier. In this study, we prepared a reversible emulsifier, DMOB(N,N-dimethyl-N'-oleic acid-1,4-butanediamine), and investigated the reversible phase inversion process of reversible emulsions, including the changes in the reversible emulsifier (HLB) and its distribution at the oil-water interface (zeta potential). From the perspective of the acid-alkali response mechanism of reversible emulsifiers, we explored the reversible phase inversion mechanism of reversible emulsions and reversible emulsification drilling fluids. It was revealed that the reversible phase inversion of emulsions could be achieved by adjusting the pH of the emulsion system. Then the proportion of ionic surfactants changed in the oil-water interface and subsequently raised/lowered the HLB value of the composite emulsifier at the oil-water interface, leading to reversible phase inversion of the emulsion. The introduction of organic clays into reversible emulsification drilling fluid can affect the reversible conversion performance of the drilling fluids at the oil-water interface. Thus, we also investigated the influence of organic clays on reversible emulsions. It was demonstrated that a dosage of organic clay of ≤2.50 g/100 mL could maintain the reversible phase inversion performance of reversible emulsions. By analyzing the microstructure of the emulsion and the complex oil-water interface, we revealed the mechanism of the influence of organic clay on the reversible emulsion. Organic clay distributed at the oil-water interface not only formed a complex emulsifier with surfactants, but also affected the microstructure of the emulsion, resulting in a difficult acid-induced phase transition, an easy alkali-induced phase transition, and improved overall stability.

Four-Arm Polymer-Guided Formation of Curcumin-Loaded Flower-Like Porous Microspheres as Injectable Cell Carriers for Diabetic Wound Healing.

Stem cell injection is an effective approach for treating diabetic wounds; however, shear stress during injections can negatively affect their stemness and cell growth. Cell-laden porous microspheres canprovide shelter for bone mesenchymal stem cells (BMSC). Herein, curcumin-loaded flower-like porous microspheres (CFPM) are designed by combining phase inversion emulsification with thermally induced phase separation-guided four-arm poly (l-lactic acid) (B-PLLA). Notably, the CFPM shows a well-defined surface topography and inner structure, ensuring a high surface area to enable the incorporation and delivery of a large amount of -BMSC and curcumin. The BMSC-carrying CFPM (BMSC@CFPM) maintains the proliferation, retention, and stemness of -BMSCs, which, in combination with their sustainable curcumin release, facilitates the endogenous production of growth/proangiogenic factors and offers a local anti-inflammatory function. An in vivobioluminescence assay demonstrates that BMSC@CFPM cansignificantly increase the retention and survival of BMSC in wound sites. Accordingly, BMSC@CFPM, with no significant systemic toxicity, couldsignificantly accelerate diabetic wound healing by promoting angiogenesis, collagen reconstruction, and M2 macrophage polarization. RNA sequencing further unveils the mechanisms by which BMSC@CFPM promotes diabetic wound healing by increasing -growth factors and enhancing angiogenesis through the JAK/STAT pathway. Overall, BMSC@CFPM represents a potential therapeutic tool for diabetic wound healing.

Preparation of the EPDM/PBMA organic dispersion based on in-situ polymerization: Application in the protection of flexible electronic devices

Ethylene propylene diene monomer (EPDM) is difficult to demonstrate its excellent performance in the coatings due to its high entanglement between molecular chains. Inspired by the phase inversion of emulsions, the EPDM/PBMA organic dispersion was prepared through the penetration and in-situ polymerization of BMA. In this strategy, the increased solubility parameter of PBMA after polymerization led to the transition of EPDM from the continuous phase to the dispersed phase, and the disentangled chain of EPDM shrank back to the shape of rod or ball. The shape of the dispersed phase was related to the interfacial tension. Particularly, the main chains of PBMA were arranged at the interface rather than buried in EPDM to maintain the stability of the organic dispersion. The EPDM/PBMA organic dispersion had excellent elasticity, bending, dispersion stability, insulation, adhesion to the glass, and aging resistance. This study indicated that the EPDM/PBMA organic dispersion could be applied as the promising protective coating for flexible electronic devices.

Effect of nonionic surfactants on the synergistic interaction between asphaltene and resin: Emulsion phase inversion and stability

Interaction between surface active components in crude oils and nonionic surfactants plays an important role in phase inversion behavior of crude oil emulsion, while the interaction mechanism is not yet fully explored. Herein, the effects of nonionic surfactants on the synergistic interaction between asphaltene and resin, emulsion stability, and emulsion phase inversion were investigated. It is shown that the addition of Span 80 and Tween 80 promotes the reduction of phase inversion point of water in oil emulsion stabilized by asphaltene and resin, as well as increases the yield strain value of the emulsion. The addition of Tween 80 to the asphaltene and resin mixture reduces the inversion point from 70 % to 30 %. The decrease of phase inversion point is attributed to the difficulty in the formation of multiple emulsions after adding nonionic surfactants. The addition of nonionic surfactants can affect the hydrogen bonding between asphaltene and resin, thereby improving the emulsion stability. Span 80 coexists with asphaltene and resin at oil-water interface, reducing the Turbiscan Stability Index (TSI) of emulsion by 15 and improving the strength of the oil-water interface membrane. In comparison, Tween 80 with stronger hydrophilic ability dissolves asphaltene and resin into bulk phase, which leads to the oil-water interface occupied by a large amount of Tween 80. Its numerous EO groups result in the strong hydrogen bonding on the oil-water interface membrane, effectively increasing the strength of the oil-water interface membrane and reducing the TSI by 19. This work contributes to a better understanding of the phase inversion of crude oil emulsion and improves crude oil recovery.

Preparation of a Sunitinib loaded microemulsion for ocular delivery and evaluation for the treatment of corneal neovascularization in vitro and in vivo.

Background: Corneal neovascularization (CNV) is a pathological condition that can disrupt corneal transparency, thus harming visual acuity. However, there is no effective drug to treat CNV. Sunitinib (STB), a small-molecule multiple receptor tyrosine kinase inhibitor, was shown to have an effect on CNV. The purpose of this study was to develop an STB microemulsion (STB-ME) eye drop to inhibit CNV by topical application. Methods: We successfully prepared an STB-ME by the phase inversion emulsification method, and the physicochemical properties of STB-MEs were investigated. The short-term storage stability, cytotoxicity to human corneal epithelial cells, drug release, ocular irritation, ocular pharmacokinetics and the inhibitory effect on CNV were evaluated in vitro and in vivo. Results: The optimal formulation of STB-ME is composed of oleic acid, CRH 40, Transcutol P, water and sodium hyaluronate (SH). It is a uniform spherical particle with a mean droplet size of 18.74 ± 0.09nm and a polydispersity index of 0.196 ± 0.004. In the in vitro drug release results, STB-ME showed sustained release and was best fitted by a Korsmeyer-Peppas model (R 2 = 0.9960). The results of the ocular pharmacokinetics in rabbits showed that the formulation containing SH increased the bioavailability in the cornea (2.47-fold) and conjunctiva (2.14-fold). STB-ME (0.05% and 0.1%), administered topically, suppressed alkali burn-induced CNV in mice more effectively than saline, and high-dose (0.1%) STB-ME had similar efficacy to dexamethasone (0.025%). Conclusion: This study provides a promising formulation of STB-ME for the inhibition of CNV by topical administration, which has the excellent characteristics of effectiveness, sustained release and high ocular bioavailability.

Innovative Aqueous Nanoemulsion Prepared by Phase Inversion Emulsification with Exceptional Homogeneity.

Formulating low-solubility or low-permeability drugs is a challenge, particularly with the low administration volumes required in intranasal drug delivery. Nanoemulsions (NE) can solve both issues, but their production and physical stability can be challenging, particularly when a high proportion of lipids is necessary. Hence, the aim of the present work was to develop a NE with good solubilization capacity for lipophilic drugs like simvastatin and able to promote the absorption of drugs with low permeability like fosphenytoin. Compositions with high proportion of two lipids were screened and characterized. Surprisingly, one of the compositions did not require high energy methods for high droplet size homogeneity. To better understand formulation factors important for this feature, several related compositions were evaluated, and their relative cytotoxicity was screened. Optimized compositions contained a high proportion of propylene glycol monocaprylate NF, formed very homogenous NE using a low-energy phase inversion method, solubilized simvastatin at high drug strength, and promoted a faster intranasal absorption of the hydrophilic prodrug fosphenytoin. Hence, a new highly homogeneous NE obtained by a simple low-energy method was successfully developed, which is a potential alternative for industrial application for the solubilization and protection of lipophilic actives, as well as (co-)administration of hydrophilic molecules.

Vitamin E encapsulated nano-emulsions formulation, rheological and antimicrobial analysis

Vitamin E is an important food ingredient that individuals ingest to help prevent numerous diseases. Nano-emulsions are frequently employed in pharmaceutical, food, and personal care applications as means of delivering a variety of lipophilic active substances, namely vitamins that are oil-soluble. Both high-energy and low-energy methods are used to create nano-emulsions. The latter, however, offers advantages including less cost, convenience of use, and increased energy efficiency. In this work, we used the emulsion phase inversion technique to create nano-emulsions containing vitamin E. We investigated the rheological and physical characteristics of nano-emulsions created at different stirring rates ranging from 30 to 110 minutes. The emulsion phase inversion approach mixes an organic phase made up of oil, vitamin E, and a surfactant with an aqueous phase. The droplet size, zeta potential, and rheology of all the nano-emulsions were measured. The size distribution of nano-emulsions was measured in the particle size examination method utilizing dynamic light scattering and average droplet diameter was observed to be within a range of 141 nm to 177 nm and to follow a sequence: 110 < 70 < 30 min. The lowest droplet size, 141 nm, with a polydispersity index of 0.234, was obtained at 110 minutes. The zeta potential of formulated nano-emulsions ranged from – 7.1 m to – 14.3 mV. The rheological properties of nano-emulsions revealed non-Newtonian flow behavior. The antimicrobial test of nano-emulsions was examined with Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), and the emulsions were resistant to S. aureus.

Phase Inversion of Pickering Emulsions Induced by Interfacial Electrostatic Attraction

Phase inversion of Pickering emulsions from water-in-oil (W/O) to oil-in-water (O/W) is achieved by the formation of an interfacial particle bilayer using negatively charged and positively charged particles dispersed in water and oil, respectively, before emulsification. A mechanism based on electrostatic attraction across the toluene-water interface is proposed and verified by systematic investigation of the parameters that affect the surface charge of negatively charged particles such as pH and salt concentration. Cationic silica-FITC particles (600 nm) can be dispersed in toluene and stabilize W/O emulsions alone; phase inversion of this emulsion can be induced by the addition of anionic silica-RB particles in the aqueous phase at a concentration of 1.0 wt % or above. It is revealed that silica-RB particles of a smaller size (100 nm) can induce emulsion phase inversion at a much lower concentration (0.4 wt %) and an interfacial particle bilayer is clearly revealed by CLSM and SEM images. By tuning the surface charge density of silica-RB particles, the electrostatic attraction mechanism leading to the formation of the interfacial particle bilayer is confirmed and emulsion stability can be tuned as demonstrated by osmotic pressure enhancement results obtained from centrifugation.

Pickering water in oil emulsions prepared from biocompatible gliadin/ethyl cellulose complex particles

Water-in-oil (W/O) emulsions have gained interest in many fields, including food, healthcare, pharmaceutical, and agriculture. However, research on Pickering W/O emulsions is limited due to the lack of available stabilizers. This study aimed to demonstrate the development of edible Pickering W/O emulsions using biocompatible and biodegradable gliadin/ethyl cellulose complex particles (GECPs) with neutral hydrophobicity as the stabilizer. The characterizations of GECPs indicated that the particle size, contact angle, and dynamic interfacial tension could be adjusted by varying the gliadin-to-ethyl cellulose (EC) ratio. The investigations of emulsions revealed that the most stable emulsions were obtained when the gliadin-to-EC ratio was 2:1. Moreover, stable emulsions could be prepared at particle concentrations higher than 1.5%. The phase inversion of emulsions from W/O to O/W occurred at 55 wt.% water. Confocal laser scanning microscopy and the theoretical calculations confirmed that GECPs formed multiple interfacial layers and acted as physical barriers against coalescence, thereby contributing to the stability of emulsions for at least 433 days; no reverse inversion occurred after 2.3 years of storage. This study provided a new approach to prepare stable Pickering W/O emulsions from GECPs. This strategy might open interesting avenues in solving the dilemma where Pickering stabilization using edible particles is required. Schematic illustration of preparation for stable Pickering W/O emulsions using biocompatible gliadin/ethyl cellulose complex particles as the particulate emulsifier. • Biocompatible gliadin/ethyl cellulose complex particles (GECPs) were fabricated using simple method. • GECPs were used to generate food-grade W/O Pickering emulsions with a stable period of at least 2.3 years. • The W/O emulsions can contain up to 50 wt.% water phase. • The type of emulsions shifted from W/O to O/W at water fraction higher than 55 wt.%. • Formation of multiple interfacial GECPs layers was confirmed.

Dual-responsive colloidosome-like microgels as the building blocks for phase inversion of Pickering emulsions.

The intelligent regulation of microgel-stabilized Pickering emulsions with multi-responsiveness is presently constrained to the processes of emulsification and destabilization. However, the expansion of multi-control over Pickering emulsions to involve phase inversion and the investigation of the accompanying processes and mechanisms present a great challenge. In this study, a microgel with dual responsiveness to both pH and temperature was synthesized using an emulsion template. The resulting microgel exhibited a robust colloidosome-like structure, distinguished by the presence of monolayer-adsorbed silica nanoparticles. The regulation of the packing of surface-covered silica nanoparticles was easily achieved through the swelling of the microgel matrix. Furthermore, the wettability of the microgel can be adjusted between hydrophilic and hydrophobic intervals, allowing for the effective and dual-responsive phase inversion of Pickering emulsions. Moreover, it has been observed that colloidosome-like microgels can lead to unique interfacial structures during the emulsification process, thereby elucidating the fundamental mechanism governing emulsion phase inversion.

Predicting the emulsion phase inversion point during self-emulsification using an improved free energy model and determining the model applicability

In-situ emulsification has recently shown promise for increasing oil production in water flooding reservoirs owing to its easy procedure and polymer and surfactant properties. The phase inversion point (PIP) plays a vital role in emulsification technology. However, the existing free energy models have limited accuracy in the calculation of the PIP, and the models’ areas of applicability are not specified. The free energy model was improved in this study by classifying crude oil to enhance the prediction accuracy and expand the free energy model’s range of calculation. The applicable range of the model was defined by analyzing and comparing the distribution characteristics of interfacial tension (IFT) and PIP. Firstly, the effects of temperature, shear rate, shear time, salinity, and pH on the PIP were discussed. The experimental results showed that, among these external factors, only the temperature could change the PIP. Generally, the PIP decreased with increasing temperature. Second, different parameters a and b were obtained using the differential aggregation characteristics of oil and water.Then, to further analyze and demonstrate the new model’s accuracy, the experimental data of three new oil samples (crude oil D, G, and J) were collected and compared with the results of other models. The results showed that the new model could successfully fit the data; its average absolute error was 4.47%, while that of the previous models was about 40%. The other models were particularly unsuitable for calculating the PIP of heavy oil, but the new model’s inaccuracy was only 1.48%. Finally, the IFT and PIP data were analyzed and compared. The results showed that, for conventional crude oil, the IFT and PIP decreased with the temperature increase. The applicable conditions of the model were also clarified. The model is suitable for crude oil whose IFT decreases with temperature increase. The results of this study can be used in the petroleum industry and other industries dealing with mixed immiscible fluid transport.

Pickering Emulsions Synergistically Stabilized by Aliphatic Primary Amines and Silica Nanoparticles.

Innovation in emulsion compositions is necessary to enrich emulsion formulations and applications. Herein, Pickering emulsions were prepared using silica nanoparticles and aliphatic primary amines with an oil-water ratio of 1:1 (v/v). Contact angle experiments revealed that the in situ hydrophobization of nanoparticles was caused by the surface adsorption of amine molecules. Notably, the interactions between amine compounds and the surface of silica nanoparticles were electrostatic attractions and mutual hydrogen bonding. The existence of hydrogen bonds was further confirmed by demulsification experiments using a chaotropic agent DMF and increasing temperatures. The hydrophobicity of silica nanoparticles can be effectively improved using most commercially available aliphatic primary amines such as n-hexylamine, n-octylamine, n-decylamine, dodecylamine, and tetradecylamine. The minimum concentrations of the aforementioned amines necessary for stabilizing the emulsions with 0.3 wt % silica nanoparticles are 3, 0.6, 0.3, 0.06, and 0.03 mM, respectively, decreasing significantly with increasing alkyl chain length. With the increase of the amine concentrations, the hydrophobicity of silica particles monotonically increased and finally resulted in the inversion of emulsions. The amine concentrations for emulsion phase inversion were 150, 40, 30, 20, and 20 mM, respectively, in the presence of 0.3 wt % silica nanoparticles. In this work, silica nanoparticles were hydrophobized using aliphatic primary amines. The composite stabilizers developed are useful for developing novel stimuli-responsive Pickering emulsions, while the synergistic effects introduced herein are also helpful in expanding the hydrophobization methods available for nanoparticles.

PH-responsive water-in-oil emulsions with reversible phase inversion behavior stabilized by a novel dynamic covalent surfactant

The dynamic covalent nature of imine bonds provides a facile avenue to develop stimuli-responsive emulsifiers and has attracted considerable interest. In petroleum engineering, the development of smart emulsifiers that can be switched on demand to achieve the reversible phase inversion of the invert emulsion drilling fluid (IEDF) can effectively aid in its removal during cleanup. To this end, a novel dynamic covalent surfactant (TA-CBA) that can precisely manipulate the emulsion type by responding to acid/base stimuli was synthesized through the Schiff base reaction between 1-tetradecylamine (TA) and 4-carboxybenzaldehyde (CBA). Evaluation of the surface tension and interfacial tension (IFT) showed that the imine-bonded product TA-CBA was a surfactant with strong IFT reduction ability. At pH 7.4, the prepared water-in-oil (W/O) emulsions were stable without any separated phases after storage for 48 h and even after high-temperature aging at 210 °C. As the pH decreased from 7.4 to 4, the emulsion inverted from a higher viscosity W/O emulsion to a lower viscosity oil-in-water (O/W) emulsion. Remarkably, after the pH was adjusted back to 7.4, the rheological parameters and stability of the emulsion could be triggered at the original W/O emulsion level. 1H NMR and IFT measurements revealed that the reversible formation and breakage of covalent imine bonds led to the production of CBA and cationic amine salt (TA+), establishing the pH reversibility of the emulsion type and its rheological properties. Finally, we successfully formulated a reversible IEDF using TA-CBA as the sole emulsifier, which not only has reasonable rheological properties, filtration performance, and emulsification stability but also allows for easy cleanup. The IEDF can be phase-inverted into a water-soluble O/W emulsion drilling fluid at pH 4 and achieved a removal efficiency of 98.13 %.

Phase inversion emulsification of paraffin oil/polyethylene wax blend in water: A comparison between mixed monomeric and monomeric/gemini surfactant systems

• Natural-based gemini surfactant (GS) reduced water surface tension more than Tween80. • Using GS reduced water phase volume fraction at phase inversion point (f w,inv ). • Change in f w,inv with polyethylene was alike change in phases interfacial tension. • Rheological properties of emulsions highly depended on crystallinity of oil phase. • Higher stability of emulsions was achieved by GS due to their higher zeta potential. Despite the environmental attractiveness of phase inversion emulsification, polyethylene wax-based emulsions are prepared by high-energy emulsification methods. In this research, phase inversion emulsification of paraffin oil/high density polyethylene wax (PEW) blend in water was conducted using mixed surfactants systems. Sorbitan monooleate (Span 80) was used as the oil-soluble surfactant, while either polysorbate 80 (Tween 80) or a synthesized sunflower oil-based gemini surfactant (SF6) was utilized as the water-soluble surfactant. In order to conduct phase inversion emulsification, the 85 °C water phase containing 5 wt% Tween 80 or SF6 was added to the melted oil phase containing 30 to 60 wt% PEW in the blend and 5 wt% Span 80 at 120 °C with the addition rate of 5 mL/min. Phase inversion point was detected by monitoring the dissolution of the emulsion in water during emulsification and proved by electrical conductivity measurements. A lower effectiveness was found for the mixed monomeric surfactant system compared to the gemini surfactant-containing system. For each surfactant system, the trend of change in water phase volume fraction at phase inversion point upon increase in the PEW content in the oil phase was in accordance with the trend of change in the interfacial tension between the water phase and the oil phase. Using the mixed monomeric/gemini surfactant system resulted in emulsions with larger values of absolute zeta potential and drop sizes comparable to their monomeric surfactant-containing counterparts. The absolute zeta potential of the emulsions containing 30, 50, and 60 wt% PEW in the blend was about 70, 54, and 13 mV higher in case of using the mixed monomeric/gemini surfactant system. The gemini surfactant-containing emulsions demonstrated less shear-thinning behavior and the general trend of change in their viscosity and storage modulus with formulation was in agreement with that in the enthalpy of melting of the dried emulsions. Usage of the mixed monomeric/gemini surfactant system led to higher long-term stability of the emulsions, revealed by lower rate of water evaporation from the emulsions. The results of the current study can be applied for preparation of non-polar polyethylene wax-based emulsions using phase inversion emulsification technique. This investigation also opens up the opportunity to use efficient gemini surfactants in low-energy phase inversion emulsification.

Preparation and characterization of patauá and pracaxi Brazilian vegetable oil emulsions

In this work, the stability of oil-in-water emulsions (O/W) of patauá (Oenocarpus bataua) and pracaxi (Pentaclethra macroloba) oils, both from Amazon rainforest, was investigated. Low-energy emulsification methods were used, such as Emulsion Inversion Point (EIP) and Phase Inversion Temperature (PIT), both based on the minimal interfacial surface, combined with optimized Hydrophilic-Lipophilic Balance (HLB). Phase inversion was determined by electrical conductivity measurements. The surfactants used were Span® 80, Tween® 20, Tween® 60, and Tween® 80. Surfactant mixtures of Span® 80 + Tween® 80 were the best samples prepared. The composition of the most stable samples was 80.00 wt% aqueous phase, 15.00 wt% nonionic surfactants, and 5.00 wt% oil phase (patauá or pracaxi oil). The samples with the best kinetic results were those prepared with the required HLB and PIT values of 12.86 and 84.05 °C, for patauá oil, and of 9.61 and 79.50 °C for pracaxi oil. The kinetic stability of the oil emulsions was characterized by creaming index (CI), by evolution over time of the droplet size, viscosity, and electric conductivity. The results showed that: (1) the droplet size distribution influenced electric conductivity; (2) the relative amount of surfactants Tween® and Span® used is more important to determine the physicochemical and interfacial properties of the emulsion than the oil identity itself; (3) it is crucial to pay attention to the influence of air bubbles—involuntarily inserted into the mixture during the emulsification process—in the physicochemical properties of the system. These conclusions can be extended to other oil-in-water emulsions.

Development and in vitro cytotoxicity assessment of nanoemulsified lawsone

Lawsone is a biomolecule that belongs to the naphthoquinone class found in henna leaves. This quinone is widely used in cosmetic products being considered the oldest coloring agent applied for dyeing hair. Moreover, biological activities have been attributed to lawsone such as antibacterial, antifungal, and anticancer. However, these activities are mostly limited due to its low aqueous solubility and chemical instability. In this context, this study aimed to develop nanoemulsion containing lawsone (NE-law) and assess its in vitro cytotoxicity against cervical carcinoma cells. Emulsion phase inversion method was used to prepare nanoemulsion formulations (NE1, NE2, NE3, NE4, and NE-law). Following the formulation development, NE1 formulation was chosen to incorporate lawsone, presenting average droplet size about 45 nm with narrow size distribution (PdI < 0.1) and negative zeta potential (≈ − 13 mV). In TEM analyses, droplets were visualized with irregular spherical shapes, high homogeneity, and without aggregation. The incorporation efficiency of lawsone into NE was higher than 90%, and in vitro release profile of this naphthoquinone from formulation was gradual and regular throughout the experiment. Nanoemulsified lawsone improved in vitro cytotoxicity on cervical carcinoma cells compared to free lawsone. Therefore, we prepared a stable lawsone-loaded NE using a reproducible emulsification method.

Antibacterial Activity of Black Pepper Essential Oil Nanoemulsion Formulated by Emulsion Phase Inversion Method

Black pepper essential oil has been proved to inhibit the growth of microorganisms in many recent studies. However, free essential oils are often lipophilic and difficult to use in food products. The nanoemulsion has some advantages such as good dispersion, long-term stability, and transparency. In our study, the Emulsion Phase Inversion method was utilized to formulate black pepper essential oil nanoemulsion. After 6 months, the nanoemulsion retained the droplet size about 18 nm and there was a rise in polydispersity index from 0.087 to 0.608. Besides, concentrations of important components (α-pinene, β-pinene, D-limonene, 3-carene, and β-caryophyllene) in the BPEO phase of nanoemulsion were similar to pure essential oil. This study was also showed that Escherichia coli and Salmonella enterica were sensitive to black pepper essential oil nanoemulsion than free essential oil. Minimal Inhibitory Concentrations of nanoemulsion for E. coli and S. enterica (137 and 273 µg/mL, respectively) were higher than those of free essential oil (547 µg/mL). In addition, nanoemulsion inhibited these bacterial growth on pork samples. When utilizing nanoemulsion as a meat preservative, meat samples, which contained nanoemulsions, observed significantly lower aerobic microbial counts than control samples.