Colloids Interfaces, Volume 7, Issue 1 (March 2023) – 24 articles

The microalgae-induced membrane system applied in wastewater treatment has attracted attention due to microalgae’s outstanding nutrient fixation capacity and biomass harvesting. However, the fundamental understanding of the interaction of microalgae and membrane surfaces is still limited. This study presents experimental and numerical methods to analyze the attachment of microalgae to the membrane. An atomic force microscope (AFM) analysis confirmed that a polydimethylsiloxane (PDMS) sensor, as a simulated membrane surface, exhibited a rougher surface morphology than a polyurethane (PU) sensor did. The contact angle and adsorption analysis using a quartz crystal microbalance confirmed that the PDMS surface, representing the membrane surface, provided a better attachment affinity than the PU surface for microalgae because of the lower surface tension and stronger hydrophobicity of PDMS. The simulation studies of this work involved the construction of roughly circular-shaped particles to represent microalgae, rough flat surfaces to represent membrane surfaces, and the interaction energy between particles and surfaces based on XDLVO theory. The modeling results of the microalgae adsorption trend are consistent and verified with the experimental results. It was observed that the interfacial energy increased with increasing the size of particles and asperity width of the membrane surface. Contrarily, the predicted interaction energy dropped with elevating the number of asperities and asperity height of the microalgae and membrane. The most influential parameter for controlling interfacial interaction between the simulated microalgae and membrane surface was the asperity height of the membrane; changing the height from 50 nm to 250 nm led to alteration in the primary minimum from −18 kT to −3 kT. Overall, this study predicted that the microalgae attachment depends on the size of the asperities to a great extent and on the number of asperities to a lesser extent. These results provide an insight into the interaction of microalgae and membrane surface, which would provide information on how the performance of microalgae-based membrane systems can be improved. Full article

Background: Non-invasive and patient-friendly nose-to-brain pathway is the best-suited route for brain delivery of therapeutics as it bypasses the blood–brain barrier. The intranasal pathway (olfactory and trigeminal nerves) allows the entry of various bioactive agents, delivers a wide array of hydrophilic and hydrophobic drugs, and circumvents the hepatic first-pass effect, thus targeting neurological diseases in both humans and animals. The olfactory and trigeminal nerves make a bridge between the highly vascularised nasal cavity and brain tissues for the permeation and distribution, thus presenting a direct pathway for the entry of therapeutics into the brain. Materials: This review portrays insight into recent research reports (spanning the last five years) on the nanoemulsions developed for nose-to-brain delivery of actives for the management of a myriad of neurological disorders, namely, Parkinson’s disease, Alzheimer’s, epilepsy, depression, schizophrenia, cerebral ischemia and brain tumours. The information and data are collected and compiled from more than one hundred Scopus- and PubMed-indexed articles. Conclusions: The olfactory and trigeminal pathways facilitate better biodistribution and bypass BBB issues and, thus, pose as a possible alternative route for the delivery of hydrophobic, poor absorption and enzyme degradative therapeutics. Exploring these virtues, intranasal nanoemulsions have proven to be active, non-invasiveand safe brain-targeting cargos for the alleviation of the brain and other neurodegenerative disorders. Full article

Many applications for crystalline triglyceride-in-water dispersions exist in the life sciences and pharmaceutical industries. The main dispersion structures influencing product properties are the particle morphology and size distribution. These can be set by the formulation and process parameters, but temperature fluctuations may alter them afterwards. As the dispersed phase often consists of complex fats, there are many formulation variables influencing these product properties. In this study, we aimed to gain a better understanding of the influence of the dispersed-phase composition on the crystallization and melting behavior of these systems. We found that different particle morphologies can be obtained by varying the dispersed-phase composition. Droplets smaller than 1 µm were obtained after melting due to self-emulsification (SE), but these changes and coalescence events were only partly influenced by the melting range of the fat. With increasing surfactant concentration, the SE tendency increased. The smallest x_50,3 of 3 µm was obtained with a surfactant concentration of 0.5 wt%. We attributed this to different mechanisms leading to the droplets’ breakup during melting, which we observed via thermo-optical microscopy. In addition, SE and coalescence are a function of the cooling and heating profiles. With slow heating (0.5 K/min), both phenomena are more pronounced, as the particles have more time to undergo the required mechanisms. Full article

The main objective of this study was to establish the relative importance of the main operating parameters impacting the formation of food-grade oil-in-water nanoemulsions by high-pressure homogenization. The goal of this unit operation was to create uniform and stable emulsified products with small mean particle diameters and narrow polydispersity indices. In this study, we examined the performance of a new commercial high-pressure valve homogenizer, which has several features that provide good control over the particle size distribution of nanoemulsions, including variable homogenization pressures (up to 45,000 psi), nozzle dimensions (0.13/0.22 mm), flow patterns (parallel/reverse), and back pressures. The impact of homogenization pressure, number of passes, flow pattern, nozzle dimensions, back pressure, oil concentration, emulsifier concentration, and emulsifier type on the particle size distribution of corn oil-in-water emulsions was systematically examined. The droplet size decreased with increasing homogenization pressure, number of passes, back pressure, and emulsifier-to-oil ratio. Moreover, it was slightly smaller when a reverse rather than parallel flow profile was used. The emulsifying performance of plant, animal, and synthetic emulsifiers was compared because there is increasing interest in replacing animal and synthetic emulsifiers with plant-based ones in the food industry. Under fixed homogenization conditions, the mean particle diameter decreased in the following order: gum arabic (0.66 µm) > soy protein (0.18 µm) > whey protein (0.14 µm) ≈ Tween 20 (0.14 µm). The information reported in this study is useful for the optimization of the production of food-grade nanoemulsions using high-pressure homogenization. Full article

The work is dedicated to study of thin V₂O₅ film formation by pen plotter printing using vanadyl alkoxyacetylacetonate as hydrolytically active precursor. Solution of the prepared vanadyl butoxyacetylacetonate complex with 87% of butoxyl groups was used as functional ink for pen plotter printing of thin V₂O₅ film on surface of specialized chip. According to atomic force microscopy (AFM) and scanning electron microscopy (SEM), oxide film consists of nanorods 35–75 nm in thickness and 120–285 nm in length, with crystallite size of 54 ± 4 nm. Data from Rietveld refinement of the X-ray powder diffraction results and work function value (4.54 eV) indicate high content of defects (such as oxygen vacancies) in the material. Electrophysical properties study suggests that correlated barrier hopping of the charge carriers is the main conductivity mechanism. Conductivity activation energy E_a was found to be 0.24 eV. Full article

The importance of electrospinning to produce biomimicking micro- and nano-fibrous matrices is realized by many who work in the area of fibers. Based on the solubility of the materials to be spun, organic solvents are typically utilized. The toxicity of the utilized organic solvent could be extremely important for various applications, including tissue engineering, biomedical, agricultural, etc. In addition, the high viscosities of such polymer solutions limit the use of high polymer concentrations and lower down productivity along with the limitations of obtaining desired fiber morphology. This emphasizes the need for a method that would allay worries about safety, toxicity, and environmental issues along with the limitations of using concentrated polymer solutions. To mitigate these issues, the use of emulsions as precursors for electrospinning has recently gained significant attention. Presence of dispersed and continuous phase in emulsion provides an easy route to incorporate sensitive bioactive functional moieties within the core-sheath fibers which otherwise could only be hardly achieved using cumbersome coaxial electrospinning process in solution or melt based approaches. This review presents a detailed understanding of emulsion behavior during electrospinning along with the role of various constituents and process parameters during fiber formation. Though many polymers have been studied for emulsion electrospinning, poly(ε-caprolactone) (PCL) is one of the most studied polymers for this technique. Therefore, electrospinning of PCL based emulsions is highlighted as unique case-study, to provide a detailed theoretical understanding, discussion of experimental results along with their suitable biomedical applications. Full article

The creeping flow of a viscous fluid around a soft colloidal sphere rotating about a diameter normal to two planar walls at an arbitrary position between them is theoretically investigated in the steady limit of small Reynolds numbers. The fluid velocity outside the particle consists of the general solutions of the Stokes equation in circular cylindrical and spherical coordinates, while the fluid velocity inside the porous surface layer of the particle is expressed by the general solution of the Brinkman equation in spherical coordinates. The boundary conditions are implemented first on the planar walls by means of the Hankel transforms and then at the particle and hard-core surfaces by a collocation technique. The torque exerted on the particle by the fluid is calculated as a function of the ratio of the core-to-particle radii, ratio of the particle radius to the flow penetration length of the porous layer, and relative particle-to-wall spacings over the entire range. The wall effect on the rotating soft particle can be significant. The hydrodynamic torque exerted on the confined soft sphere increases as the relative particle-to-wall spacings decrease and stays finite even when the soft sphere contacts the plane walls. It is smaller than the torque on a hard sphere (or soft one with a reduced thickness or penetration length of the porous layer), holding the other parameters constant. For a given relative wall-to-wall spacing, this torque is minimal when the particle is situated midway between the walls and rises as it locates closer to either wall. Full article

The objective of this research work is to propose a phase diagram that can be used to find a proper operating condition for generating droplets of different types. It is found that the phase diagram of Q_R versus Ca_D can effectively classify the droplet generation into three vivid regimes: dripping, jetting and tubing. For the dripping regime, its operating condition is in the range of either Ca_D < 10⁻⁴ and Q_R < 50 or 10⁻³ < Ca_D < 10⁻⁴ and Q_R < 1. For the jetting regime, its operating condition is in the range of either Ca_D < 1.35 × 10⁻² and Q_R > 100 or Ca_D > 1.35 × 10⁻² and Q_R > 1. For the tubing regime, its operating condition is in the range of Ca_D > 1.35 × 10⁻² and Q_R < 1. Full article

Formulations based on emulsions for enhancing hydrophobic and lipophilic drug delivery and its bioavailability have attracted a lot of interest. As potential therapeutic agents, they are integrated with inert oils, emulsions, surfactant solubility, liposomes, etc.; drug delivering systems that use emulsion formations have emerged as a unique and commercially achievable accession to override the issue of less oral bioavailability in connection with hydrophobic and lipophilic drugs. As an ideal isotropic oil mixture of surfactants and co-solvents, it self-emulsifies and forms fine oil in water emulsions when acquainted with aqueous material. As droplets rapidly pass through the stomach, fine oil promotes the vast spread of the drug all over the GI (gastrointestinal tract) and conquers the slow disintegration commonly seen in solid drug forms. The current status of advancement in technologies for drug carrying has promulgated the expansion of innovative drug carriers for the controlled release of self-emulsifying pellets, tablets, capsules, microspheres, etc., which got a boost for drug delivery usage with self-emulsification. The present review article includes various kinds of formulations based on the size of particles and excipients utilized in emulsion formation for drug delivery mechanisms and the increase in the bioavailability of lipophilic/hydrophobic drugs in the present time. Full article

Due to surface effects and quantum size effects, nanomaterials have properties that are vastly different from those of bulk materials due to surface effects. The particle size distribution plays an important role in chemical and physical properties. The measurement and control of this parameter are crucial for nanomaterial synthesis. Dynamic light scattering (DLS) is a fast and non-invasive tool used to measure particle size, size distribution and stability in solutions or suspensions during nanomaterial preparation. In this review, we focus on the in situ sizing of nanomaterial preparation in the form of colloids, especially for metal oxide nanoparticles (MONs). The measuring principle, including an overview of sizing techniques, advantages and limitations and theories of DLS were first discussed. The instrument design was then investigated. Ex-situ and in situ configuration of DLS, sample preparations, measurement conditions and reaction cell design for in situ configuration were studied. The MONs preparation monitored by DLS was presented, taking into consideration both ex situ and in situ configuration. Full article

The development of electrocatalysts for oxygen evolution reactions (OERs) is of great significance for hydrogen production. Defect engineering is an effective strategy to improve the OER performance of electrocatalyst by regulating the local electronic and atomic structures of electrocatalysts. Here, we successfully synthesized defective Prussian blue analogues (PBAs) with rich CN vacancies (D-NiFe PBA) as efficient OER electrocatalysts. The optimized D-NiFe PBA exhibited an overpotential of 280 mV at 10 mA cm⁻² and a superior stability for over 100 h in KOH electrolytes. The formation of CN vacancies in the NiFe PBA could effectively inhibit the loss of Fe active sites, promote the reconstruction of the NiFe oxygen (hydroxide) active layer in the OER process, and further improve the electrocatalytic activity and stability of the V_CN-NiFe PBA. This work presents a feasible approach for the wide application of vacancy defects in PBA electrocatalysts. Full article

The effect of wax molecular weight distribution on the efficacy of two alpha olefin-maleic anhydride paraffin inhibitors (PIs) having different densities of alkyl side-chains were examined in light West Texas crude in the absence and presence of asphaltenes. Interpretation of the data was aided by cross-polarization microscopy. Primary differences in wax crystal morphology appear to be driven by the composition of the wax, with secondary differences being associated with the choice of PI. In the absence of asphaltenes, the effect of wax composition on PI performance (i.e., reducing oil viscosity and wax appearance temperature) is greater for the PI having the higher chain density, with the one having the lower chain density being generally more effective regardless of the wax composition. These differences are diminished in the presence of asphaltenes such that the PI having the higher chain density is somewhat more effective. Trends in both morphology and viscosity suggest a steric effect associated with wax composition that is lessened on interaction of the PIs with asphaltenes. Full article

Emulsions with crystalline dispersed phase fractions are becoming increasingly important in the pharmaceutical, chemical, and life science industries. They can be produced by using two-stage melt emulsification processes. The completeness of the crystallization step is of particular importance as it influences the properties, quality, and shelf life of the products. Subcooled, liquid droplets in agitated vessels may contact an already crystallized particle, leading to so-called contact-mediated nucleation (CMN). Energetically, CMN is a more favorable mechanism than spontaneous nucleation. The CMN happens regularly because melt emulsions are stirred during production and storage. It is assumed that three main factors influence the efficiency of CNM, those being collision frequency, contact time, and contact force. Not all contacts lead to successful nucleation of the liquid droplet, therefore, we used microfluidic experiments with inline measurements of the differential pressure to investigate the minimum contact force needed for successful nucleation. Numerical simulations were performed to support the experimental data obtained. We were able to show that the minimum contact force needed for CMN increases with increasing surfactant concentration in the aqueous phase. Full article

Periodical oil spills and massive production of industrial oil wastewater have impacted the aquatic environment and has put the sustainability of the ecosystem at risk. Oil–water separation has emerged as one of the hot areas of research due to its high environmental and societal significance. Special wettable membranes have received significant attention due to their outstanding selectivity, excellent separation efficiency, and high permeation flux. This review briefly discusses the fouling behavior of membranes and various basic wettability models. According to the special wettability, two major classes of membranes are discussed. One is superhydrophobic and superoleophilic; these membranes are selective for oil and reject water and are highly suitable for separating the water-in-oil emulsions. The second class of membranes is superhydrophilic and underwater superoleophobic; these membranes are highly selective for water, reject the oil, and are suitable for separating the oil-in-water emulsions. The properties and recent progress of the special wettable membranes are concisely discussed in each section. Finally, the review is closed with conclusive remarks and future directions. Full article

The possibility of obtaining porous films through solutions of polylaurolactam (PA12) in benzyl alcohol (BA) was considered. The theoretical calculation of the phase diagram showed the presence of the upper critical solution temperature (UCST) for the PA12/BA system at 157 °C. The PA12 completely dissolved in BA at higher temperatures, but the resulting solutions underwent phase separation upon cooling down to 120–140 °C because of the PA12’s crystallization. The viscosity of the 10–40% PA12 solutions increased according to a power law but remained low and did not exceed 5 Pa·s at 160 °C. Regardless of the concentration, PA12 formed a dispersed phase when its solutions were cooled, which did not allow for the obtention of strong films. On the contrary, the phase separation of the 20–30% PA12 solutions under the action of a non-solvent (isopropanol) leads to the formation of flexible microporous films. The measurement of the porosity, wettability, strength, permeability, and rejection of submicron particles showed the best results for a porous film produced from a 30% solution by non-solvent-induced phase separation. This process makes it possible to obtain a membrane material with a 240 nm particle rejection of 99.6% and a permeate flow of 1.5 kg/m²hbar for contaminated water and 69.9 kg/m²hbar for pure water. Full article

Here, we prepared hydrophobic cryogel particles with monolithic supermacropores based on poly-trimethylolpropane trimethacrylate (pTrim) by combining the inverse Leidenfrost effect and cryo-polymerization technique. The hydrophobic cryogel particles prepared by adopting this method demonstrated the separation of the stabilized O/W emulsion with surfactant. The prepared cryogel particles were characterized in terms of macroscopic shape and porous structure. It was found that the cryogel particles had a narrow size distribution and a monolithic supermacroporous structure. The hydrophobicity of the cryogel particles was confirmed by placing aqueous and organic droplets on the particles. Where the organic droplet was immediately adsorbed into the particles, the aqueous droplet remained on the surface of the particle due to repelling force. In addition, after it adsorbed the organic droplet the particle was observed, and the organic solvent was diffused into the entire particle. It was indicated that monolithic pores were distributed from the surface to the interior. Regarding the application of the hydrophobic cryogel particles, we demonstrated the separation of a stabilized oil-in-water emulsion, resulting in the successful removal of the organic solvent from the emulsion. Full article

Magnetic resonance imaging is one of the most widely used diagnostic techniques, since it is non-invasive and provides high spatial resolution. Contrast agents (CAs) are usually required to improve the contrast capability. CAs can be classified as T1 (or positive) or T2 (or negative) contrast agents. Nowadays, gadolinium chelates (which generate T1 contrast) are the most used in clinical settings. However, the use of these chelates presents some drawbacks associated with their toxicity. Iron oxide magnetic nanoparticles (MNPs) have been extensively investigated as CA for MRI, especially for their capacity to generate negative contrast. The need for more efficient and safer contrast agents has focused investigations on the development of dual CAs, i.e., CAs that can generate both positive and negative contrast with a single administration. In this sense, nanotechnology appears as an attractive tool to achieve this goal. Nanoparticles can be modified not only to improve the contrast ability of the current CAs but also to enhance their biocompatibility, resolving toxicity issues. With the aim of contributing to the field of development of dual T1/T2 contrast agents for MRI, here, we present the obtained results of the synthesis of hybrid nanoparticles composed of magnetite/maghemite and gadolinium hydroxide. Exhaustive characterization work was conducted in order to understand how the hybrid nanoparticles were formed. The nanoparticles were extensively characterized through FTIR and UV–Vis spectroscopy, TEM and SEM microscopy, X-ray diffraction (XRD) analysis, dynamic light scattering, zeta potential, thermogravimetric analysis, energy-dispersive X-ray and vibrating-sample magnetometry. Stabilization studies were carried out to get an idea of the behavior of nanohybrids in physiological media. Special interest was given to the evaluation of Gd³⁺ leaching. It was found that carbohydrate coating as well as the adsorption of proteins on the surface may improve the stabilization of hybrid nanoparticles. Full article

The hierarchically directed assembly of multiple types of colloidal nano-objects on surfaces is of interest for developing disruptive applications combining their original properties. We propose herein a versatile, electrostatically driven strategy to arrange various kinds of colloids vertically in the shape of 3D micropatterns by nanoxerography. We made the proof of concept of this vertical combinatorial nano-object patterning using two types of photoluminescent CdSe(S)/CdZnS core/shell nanoplatelets emitting in the red and green wavelengths as model colloidal nanoparticles. The key experimental parameters were investigated to tune the thickness of each independent level of nanoplatelets within the vertical stack. We finally applied such a concept to make dual-colored nanoplatelet patterns. Interestingly, we proved numerically that the relatively high index of the nanoplatelet level is responsible for the partially directed emissions observed in photoluminescence experiments. Full article

The physicochemical properties of ligand-coated nanoparticles make them superior adsorbents for heavy metals from water. In this study, we investigate the adsorption potential of novel polyacrylic-co-maleic-acid-coated magnetite nanoparticles (PAM@MNP) to remove Pb²⁺ and Cu²⁺ from an aqueous solution. We argue that modifying the surface of MNP with PAM enhances the physicochemical stability of MNP, improving its ability to remove heavy metals. The adsorption kinetics data show that PAM@MNP attained sorption equilibrium for Pb²⁺ and Cu²⁺ after 60 min. The kinetics data are fitted accurately by the pseudo-first-order kinetic model. The calculated Langmuir adsorption capacities are 518.68 mg g⁻¹ and 179.81 mg g⁻¹ for Pb²⁺ and Cu²⁺, respectively (2.50 mmol g⁻¹ and 2.82 mmol g⁻¹ for Pb²⁺ and Cu²⁺, respectively). The results indicate that PAM@MNP is a very attractive adsorbent for heavy metals and can be applied in water remediation technologies. Full article

Two-phase aqueous systems have replaced and simplified steps in extraction and purification processes, especially for biocompounds. Thus, this study evaluated the liquid-liquid equilibrium behavior of Pluronic L64 + water + sodium salts at pH 5.0, 7.5, and 10.0. Sodium sulfate demonstrated the greatest phase separation, followed by sodium citrate and sodium tartrate. Higher pH values resulted in larger biphasic regions. The polymer distribution coefficients increased with the addition of salt. As pH increased, there was a tendency for Pluronic L64 to migrate to the polymer-rich phase. The Gibbs energy of micellization between −11,000 and −25,000 kJ mol⁻¹ indicated the spontaneity of the process micellization for all systems, showing lower values for the systems with sodium sulfate. This parameter was related to the anion speciation at each pH. Besides, the effects of water structuring around ions and ion-polymer interaction influenced the phase separation. Full article

Bridging the gap between laboratory-scale experiments and actual oilfield operations is a complex task that requires a compromise between real (authentic) fluids and model systems. Commercial products (i.e., asphaltene inhibitors and dispersants) are often designed to target a wide range of operating conditions and compositions of crude oils, which means that the performance becomes almost case-specific. Through Atomic Force Microscopy (AFM) imaging and Transmission/Backscattering signals (T/BS), the morphology of asphaltene deposits and the mechanisms that eventually lead to precipitated material were evaluated. Two different models (starting solutions) with four different n-alkanes were used to induce variability in asphaltene agglomeration and subsequent precipitation paths. It was found that increasing the carbon number shifted the observed precipitation detection time (T/BS data suggested a shift in the order of $~1000 \mathrm{s}$ when comparing low and high carbon numbers) and influences the density of the precipitated material under static and a sufficiently high concentration of solvent conditions. Further analysis on the morphology of the resulting material after the addition of commonly used chemicals showed that asphaltene stability through inhibition (i.e., blockage or crowding of potential active sites) led to smaller complexes. One of the additives (PIBSA) reduced the average height in $~33\%$ and the mean square roughness in $~72\%$. On the other hand, stability through dispersion (i.e., hindering agglomeration) leads to a polymer-like network bigger in size, noting that in both cases the system remains soluble. The use of APR resulted in an increase of $~41\%$ and $~54\%$ for the same parameters. This insight sheds light on how to devise efficient chemical strategies to prevent flow assurance issues. Full article

Although nanoparticles (NPs) are known to increase foam stability, foam stabilisation is not observed in all surfactant/NP combinations. The present study evaluates the stability of CO₂ foams containing surfactant/NP mixtures with attractive or repulsive electrostatic interactions at the low pH imposed by CO₂ in the presence of a high-salinity brine. Three ionic surfactants and two oxide NPs (SiO₂ and Al₂O₃) were used in combinations of similar or opposite charges. Surface tension, viscosity, ζ-potential and hydrodynamic size experiments allowed the analysis of CO₂ foam stability based on the impact of surfactant–NP interactions on bulk and interfacial properties. All oppositely charged systems improved the foam half-life; however, a higher NP concentration was required to observe a significant effect when more efficient surfactants were present. Both bulk viscosity and rigidity of the interfacial films drastically increased in these systems, reducing foam drainage. The mixture of SiO₂ with a zwitterionic surfactant showed the greatest increase in CO₂ foam stability owing to the synergy of these effects, mediated by attractive interactions. This study showed that the use of NPs should be tailored to the surfactant of choice to achieve an interplay of interfacial and rheological properties able to reduce foam drainage in applications involving CO₂ foam in brine. Full article

Stable primary emulsion formation in which different parameters such as viscosity and droplet size come into prominence for their characterization is a key factor in W/O/W emulsions. In this study, different emulsifiers (Crill™ 1, Crill™ 4, AMP, and PGPR) were studied to produce a casein-hydrolysate-loaded stable primary emulsion with lower viscosity and droplet size. Viscosity, electrical conductivity, particle size distribution, and emulsion stability were determined for three different dispersed phase ratios and three emulsifier concentrations. In 31 of the 36 examined emulsion systems, no electrical conductivity could be measured, indicating that appropriate emulsions were formed. While AMP-based emulsions showed non-Newtonian flow behaviors with high consistency coefficients, all PGPR-based emulsions and most of the Crill™-1- and -4-based ones were Newtonian fluids with relatively low viscosities (65.7–274.7 cP). The PGPR-based emulsions were stable for at least 5 days and had D(90) values lower than 2 µm, whereas Crill™-1- and -4-based emulsions had phase separation after 24 h and had minimum D(90) values of 6.8 µm. PGPR-based emulsions were found suitable and within PGPR-based emulsions, and the best formulation was determined by TOPSIS. Using 5% PGPR with a 25% dispersed phase ratio resulted in the highest relative closeness value. The results of this study showed that PGPR is a very effective emulsifier for stable casein-hydrolysate-loaded emulsion formations with low droplet size and viscosity. Full article