Oil Phase Composition Research Articles

Cinnamon oil nanoemulsions by spontaneous emulsification: Formulation, characterization and antimicrobial activity

The goal of this study was to formulate stable cinnamon oil nanoemulsions (NEs) exhibiting high antimicrobial activity by using the low-energy approach: spontaneous emulsification (SE) and compare it with two high-energy methods. To prepare the nanoemulsions by SE, oil phase containing cinnamon oil (CO) and carrier oil (coconut oil (CNO)) at different ratios (2:8–10:0) and surfactant (Tween 80) at 10% (w/w) was titrated into an aqueous phase (distilled water). For antimicrobial activity, agar disc diffusion method with E. coli as the model microorganism was used. NEs were characterized by Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM). Both DLS and TEM gave parallel results and mean particle size were found as ∼ 100 nm for 6:4 (CO: CNO) oil phase composition. These NEs also showed high physical stability during one-month storage. NEs were also prepared by using two high-energy homogenization methods: microfluidization and ultrasonication. Ultrasonication and SE showed similar trends for mean particle size and microbial activity. Microfluidization resulted in the smallest mean particle size (p < 0.05) and antimicrobial activity was not effected from cinnamon oil concentration (p > 0.05).

Fabrication of Transparent Lemon Oil Loaded Microemulsions by Phase Inversion Temperature (PIT) Method: Effect of Oil Phase Composition and Stability after Dilution

This research was addressed to develop transparent microemulsions as delivery system of lemon oil. To this aim, phase inversion temperature (PIT) method was employed. The effect of the surfactant Tween 80 content as well as lipid phase type and concentration (lemon oil, peanut oil and their mixtures) on microemulsion characteristics was studied. Transparent emulsions were obtained up to 1.3 and 7.5% (w/w) of lemon oil and peanut oil, respectively. Only by considering as lipid phase a mixture of lemon oil and peanut oil, it was possible to increase the delivering capacity of emulsions up to 15% of lemon oil (total oil phase 20%). Therefore, blending peanut oil rich in long chain fatty acids with lemon oil expanded the lipid phase loading capacity of microemulsions while maintaining particle size lower than 30 nm and thus system transparency. Microemulsions showed good dilutability in aqueous solutions simulating beverage formulations with different pH values.

Impact of oil composition on formation and stability of emulsions produced by spontaneous emulsification

ABSTRACTIn this study, triglycerides of different chain lengths were mixed with paraffin oil, and their effectiveness in forming emulsions produced by spontaneous emulsification upon the addition of water was investigated. The emulsion droplet size exhibited a similar trend as a function of the triglyceride/paraffin oil composition for medium-chain (MCTs) (C8–C10) and long-chain (C18) triglycerides (LCTs). However, emulsions formulated with MCTs and LCTs have a much smaller droplet size (about 50 nm) than emulsions based upon short-chain (C4) triglycerides (SCTs). The addition of SCTs resulted in droplet sizes around 800 nm and the emulsions formed were very unstable. The droplet size, polydispersity index, zeta potential, and emulsion stability of these systems will be described as a function of the oil phase composition.

Influence of pH and cinnamaldehyde on the physical stability and lipolysis of whey protein isolate-stabilized emulsions

Cinnamaldehyde (CA), a common hydrophobic flavor, was encapsulated in oil-in-water emulsions that were stabilized by whey protein isolate (WPI). The impact of CA content and pH on the physical stability and lipolysis of the emulsions was then investigated. The presence of CA gave the emulsions a creamy yellow color, which became darker during storage. Emulsions formed using only CA as the oil phase contained large droplets that were physically unstable to particle growth and phase separation. The addition of medium chain triglyceride oil (MCT) improved the stability of emulsions containing CA, which was attributed to inhibition of Ostwald ripening effects. Fluorescent microscopy indicated that the adsorption of the protein to the droplet surfaces led to a thicker adsorbed layer in the presence of CA. The stability of the emulsions to droplet flocculation and coalescence depended on the CA level in the oil phase and the pH of the aqueous phase. An in vitro model was used to assess the impact of oil phase composition and pH on lipid hydrolysis and emulsion microstructure under simulated gastrointestinal tract conditions. The rate of lipid hydrolysis was highly dependent on CA level and pH. These results may facilitate the fabrication of emulsions with controlled GIT fate that are suitable for use in functional foods and beverages.

Influence of surfactant type and thermal cycling on formation and stability of flavor oil emulsions fabricated by spontaneous emulsification

Food-grade emulsions can be fabricated using simple and inexpensive low-energy homogenization methods. In this study, we examined the influence of surfactant type (Tween 40, 60, and 80), oil phase composition (limonene-to-medium chain triglyceride ratio), and temperature (25 to 95°C) on the formation and stability of flavor oil-in-water emulsions (10wt% oil, 15wt% surfactant, pH3) fabricated using spontaneous emulsification. Transparent emulsion-based delivery systems containing ultrafine droplets (d<40nm) could be formed at room temperature at certain limonene contents for all three surfactants. When these emulsions were heated and then cooled, appreciable droplet growth occurred at lower limonene levels (<60% limonene) leading to cloudiness, but ultrafine droplets were still present at higher limonene concentrations (80% limonene) leading to optical clarity. These results were attributed to the influence of oil phase composition and surfactant type on the phase inversion behavior of the surfactant-oil-water systems.

Physical and antimicrobial properties of thyme oil emulsions stabilized by ovalbumin and gum arabic

Natural biopolymer stabilized oil-in-water emulsions were formulated using ovalbumin (OVA), gum arabic (GA) solutions and their complexes. The influence of interfacial structure of emulsion (OVA-GA bilayer and OVA/GA complexes emulsions) on the physical properties and antimicrobial activity of thyme oil (TO) emulsion against Escherichia coli (E. coli) was evaluated. The results revealed that the two types of emulsions with different oil phase compositions remained stable during a long storage period. The oil phase composition had an appreciable influence on the mean particle diameter and retention of the TO emulsions. The stable emulsion showed a higher minimum inhibitory concentration (MIC), and the TO emulsions showed an improved long-term antimicrobial activity compared to the pure thyme oil, especially complexes emulsion at pH 4.0. These results provided useful information for developing protection and delivery systems for essential oil using biopolymer.

Improved Stability of Emulsions in Preparation of Uniform Small-Sized Konjac Glucomanna (KGM) Microspheres with Epoxy-Based Polymer Membrane by Premix Membrane Emulsification.

Uniform small-sized (<10 μm) Konjac glucomanna (KGM) microspheres have great application prospects in bio-separation, drug delivery and controlled release. Premix membrane emulsification is an effective method to prepare uniform small-sized KGM microspheres. However, since KGM solution bears strong alkalinity, it requires the membrane to have a hydrophobic surface resistant to alkali. In this study, uniform small-sized KGM microspheres were prepared with epoxy-based polymer membrane (EP) we developed by premix membrane emulsification. It was found that emulsion coalescence and flocculation occurred frequently due to the high interface energy and sedimentation velocity of KGM emulsions. Emulsion stability had a significant influence on the uniformity and dispersity of the final KGM microspheres. To improve the stability of the emulsions, the effects of the concentration of the emulsifier, the viscosity of the KGM solution, the oil phase composition and the feeding method of epoxy chloropropane (EC) on the preparation results were studied. Under optimal preparation conditions (emulsifier 5 wt % PO-5s, KGM III (145.6 mPa·s), weight ratio of liquid paraffin (LP) to petroleum ether (PE) 11:1), uniform and stable KGM emulsions (d = 7.47 μm, CV = 15.35%) were obtained and crosslinked without emulsion-instable phenomena.

Controlled release of casein-derived peptides in the gastrointestinal environment by encapsulation in water-in-oil-in-water double emulsions

Dye-labeled peptides were produced by hydrolysis of azocasein and encapsulated in water-in-oil-in-water double emulsions. The effect of degree of hydrolysis (0%, 3.5%, or 7%) and oil phase composition (butter oil, linseed oil, or mineral oil) on the emulsion characteristics and peptide release kinetics during simulated gastrointestinal digestion was investigated. The double emulsions made from linseed oil and butter oil had smaller oil droplets, lower viscosity, and greater creaming stability than the double emulsion made from mineral oil did. The encapsulation efficiency was higher than 93%. The percentage of peptide release at the end of the gastric phase varied from 4% to 42%. Butter oil and linseed oil were attacked by the lipases during the intestinal phase of the digestion, and the peptide release increased progressively to more than 80%. The release of hydrolyzed azocasein was faster than the release of unhydrolyzed azocasein in both phases of digestion. Mineral oil was indigestible and strongly inhibited peptide release, which remained lower than 18%. The release behavior was strongly influenced by the composition as well as the hydrophobicity of the oil phase. Depending on peptide molecular weight, the kinetics of release can be controlled by adjusting oil phase composition.

Formation, optical property and stability of orange oil nanoemulsions stabilized by Quallija saponins

Nanoemulsions have the potential to deliver insoluble materials and yet provide a transparent appearance in clear beverage applications. The influence of oil phase composition, phase viscosity and homogenization conditions on the formation, stability and optical properties of orange oil-based nanoemulsions was investigated. The nanoemulsions were formed using Quillaja saponins (QS) and homogenization accomplished using Microfluidization®. The results indicated oil phase composition and viscosity ratio between phases are key parameters determining the mean droplet diameter (MDD) of the prepared nanoemulsions. Orange oil nanoemulsions stabilized by QS showed MDD as small as 67 nm corresponding to turbidity of 71 NTU at dispersed phase concentration of 0.5 mg/g. Lipid phase refractive index showed no effect on turbidity of orange oil nanoemulsions at MDD<150 nm, while MDD was linearly related to the turbidity with MDD ranging from 60 nm to 120 nm. Ostwald ripening was identified as main destabilization mechanism of orange oil nanoemulsions stabilized by QS at the early stage of storage. The rate of Ostwald ripening was reduced with increasing amounts of medium chain triglycerides (MCT) in the dispersed phase. An insoluble material, e.g., ester gum or MCT, was required to form stable orange oil-based nanoemulsions.

Development and Evaluation of Nanoemulsions Containing Phthalocyanines for Use in Photodynamic Cancer Therapy.

This work reports the development of oil in water (o/w) nanoemulsions containing poly(ethylene oxide)-poly(propylene oxide) block copolymer surfactant for the formulation of a delivery system for endovenous zinc and chloroaluminum phthalocyanines. A solubility study suggested clove oil and its combination with ethanol as the best candidates for the oil phase composition. The nanoemulsions were obtained using a high-pressure homogenizer and analyzed for droplet size to determine their short- and long-term stability. Formulations containing 7 and 10% oil phase and 12% surfactant presented higher stability and allowed the incorporation of a bigger amount of phthalocyanines in the formulation. Rheological analyses showed the prevailing Newtonian behavior of the nanoemulsions. Studies of toxicity and phototoxicity determined that the nanoemulsions produced were capable of inhibiting the growth of adenocarcinoma tumor cells. The nanoemulsions proved to be a good alternative for use in photodynamic therapy.

Formation of thermally reversible optically transparent emulsion-based delivery systems using spontaneous emulsification.

Transparent emulsion-based delivery systems suitable for encapsulating lipophilic bioactive agents can be fabricated using low-energy spontaneous emulsification methods. These emulsions are typically fabricated from non-ionic surfactants whose hydrophilic head groups are susceptible to dehydration upon heating. This phenomenon may promote emulsion instability due to enhanced droplet coalescence at elevated temperatures. Conversely, the same phenomenon can be used to fabricate optically transparent emulsions through the phase inversion temperature (PIT) method. The purpose of the current study was to examine the influence of oil phase composition and surfactant-to-oil ratio on the thermal behavior of surfactant-oil-water systems containing limonene, medium chain triglycerides (MCT), and Tween 60. Various types of thermal behavior (turbidity versus temperature profiles) were exhibited by these systems depending on their initial composition. For certain compositions, thermoreversible emulsions could be formed that were opaque at high temperatures but transparent at ambient temperatures. These systems may be particularly suitable for the encapsulation of bioactive agents in applications where optical clarity is important.

Microencapsulation of capsanthin by self-emulsifying nanoemulsions and stability evaluation

The application of natural colorants in food products has been gained more and more attention, not only due to their nutritional advantages, but also their functional properties. The purpose of this research was to encapsulate capsanthin from paprika by nanoemulsions (NEs), and the stability of resultant NEs was evaluated. The NE systems were first optimized by dropwise adding mixed organic phase [5 wt% medium-chain triglyceride (MCT) and 10 wt% surfactant containing span 20 and tween 80 with the weight ratio 1:3 and HLB 13.4] into water phase. Then capsanthin was mixed with MCT as the oil phase. With the presence of capsanthin, the oil phase composition had great impact on the particle size of NEs that the droplet size increased from 30 to 150 nm with increasing capsanthin content. Generally, higher temperature and stirring speed would decrease the particle size, which also depended on the surfactant-to-oil ratio. The stability results demonstrated that there was no obvious change on the capsanthin NE droplet size and entrapped capsanthin content after 1 month storage at ambient temperature. Our results are important for the design of food-grade delivery systems to encapsulate natural lipophilic pigments or ingredients.

Formation of vitamin D nanoemulsion-based delivery systems by spontaneous emulsification: Factors affecting particle size and stability

Oil-in-water nanoemulsions are particularly suitable for encapsulation of lipophilic nutraceuticals because of their ability to form stable and transparent delivery systems with high oral bioavailability. In this study, the influence of system composition and preparation conditions on the particle size and stability of vitamin D nanoemulsions prepared by spontaneous emulsification (SE) was investigated. SE relies on the formation of small oil droplets when an oil/surfactant mixture is titrated into an aqueous solution. The influence of oil phase composition (vitamin D and MCT), surfactant-to-oil ratio (SOR), surfactant type (Tween 20, 40, 60, 80 and 85), and stirring conditions on the initial particle size of vitamin D nanoemulsions was studied. Nanoemulsions with small droplet diameters (d<200nm) could be formed using Tween 80 at SOR⩾1 at high stirring speeds (800rpm). These systems were relatively stable to droplet growth at ambient temperatures (<10% in diameter after 1month storage), but unstable to heating (T>80°C). The thermal stability of the nanoemulsions could be improved by adding a cosurfactant (sodium dodecyl sulphate (SDS)). The spontaneous emulsification method is simple and inexpensive to carry out and therefore has great potential for forming nanoemulsion-based delivery systems for food, personal care, and pharmaceutical applications.

Optimization of Orange Oil Nanoemulsion Formation by Isothermal Low-Energy Methods: Influence of the Oil Phase, Surfactant, and Temperature

Nanoemulsions are particularly suitable as a platform in the development of delivery systems for lipophilic functional agents. This study shows that transparent orange oil nanoemulsions can be fabricated using an isothermal low-energy method (spontaneous emulsification), which offers the advantage of fabricating flavor oil delivery systems using rapid and simple processing operations. Orange oil nanoemulsions were formed spontaneously by titration of a mixture of orange oil, carrier oil [medium-chain triglyceride (MCT)], and non-ionic surfactant (Tween) into an aqueous solution (5 mM citrate buffer at pH 3.5) with continuous stirring. The oil/emulsion ratio content was kept constant (10 wt %), while the surfactant/emulsion ratio (SER) was varied (2.5-20 wt %). Oil-phase composition (orange oil/MCT ratio), SER, and surfactant type all had an appreciable effect on nanoemulsion formation and stability. Transparent nanoemulsions could be formed under certain conditions: 20% surfactant (Tween 40, 60, or 80) and 10% oil phase (4-6% orange oil + 6-4% MCT). Surfactant type and oil-phase composition also affected the thermal stability of the nanoemulsions. Most of the nanoemulsions broke down after thermal cycling (from 20 to 90 °C and back to 20 °C); however, one system remained transparent after thermal cycling: 20% Tween 80, 5% orange oil, and 5% MCT. The mean droplet size of these nanoemulsions increased over time, but the droplet growth rate was reduced appreciably after dilution. These results have important implications for the design and utilization of nanoemulsions as delivery systems in the food and other industries.

Nanoemulsions containing Vitamin E acetate prepared by PIC(phase inversion composition) methods: Factors affecting droplet sizes

We have investigated the influence of system composition and preparation conditions on the particle size of vitamin E acetate (VE)-loaded nanoemulsions prepared by PIC, phase inversion composition emulsification. This method relies on the formation of very fine oil droplets when water is added to oil/surfactant mixture. The oil-to-emulsion ratio content was kept constant (5 wt.%) while the surfactant-to-oil ratio (%SOR) was varied from 50 to 200 %. Oil phase composition (vitamin E to medium chain ester ratio, %VOR) had an effect on particle size, with the smallest droplets being formed below 60 % of VOR. Food-grade non-ionic surfactants (Tween 80 and Span 80) were used as an emulsifier. The effect of f on the droplet size distribution has been studied. In our system, the droplet volume fraction, given by the oil volume fraction plus the surfactant volume fraction, was varied from 0.1 to 0.3. The droplet diameter remains less than 350 nm when O/S is fixed at 1:1. The droplet size increases gradually as the increasing the volume fraction. Particle size could also be reduced by increasing the temperature when water was added to oil/ surfactant mixture. By optimizing system composition and homogenization conditions we were able to form VE-loaded nanoemulsions with small mean droplet diameters (d < 50 nm). The PIC emulsification method therefore has great potential for forming nanoemulsion-based delivery systems for food, personal care, and pharmaceutical applications.

Preparation of uniform and large sized agarose microspheres by an improved membrane emulsification technique

The SPG (Shirasu porous-glass) membrane emulsification technique has been subject to much attention for the preparation of uniform emulsions. However, so far primarily used for the production of droplets with sizes below approximately 60μm. A production bottleneck occurred if the desired size was further increased, especially when highly viscous dispersed phases were involved. To this end, an improved membrane emulsification technique was proposed and has been applied to the preparation of large agarose microspheres, with a size of around 90μm and with a narrow size distribution. The effects of important emulsification parameters, including the pore size of the SPG membrane, the operating pressure, the stirring rate of the continuous phase, the composition of the continuous oil phase, and the concentration of agarose in the dispersed water phase, have been extensively studied. Under optimum conditions, uniform-size agarose microspheres with an average diameter of 93μm and a size distribution index of 0.65 were successfully prepared. The average particle size of the home-made agarose microspheres was almost identical to that of the commercial product Sepharose 4 Fast Flow (4FF), which is produced by mechanical stirring and an additional sieving process. However, the size distribution of the former was much narrower than that of the latter. Therefore, the improved membrane emulsification technique presented here is promising for the application of high viscosity systems such as agarose solutions, and the production scale can be further enhanced by increasing the number of membrane units attached to the experimental apparatus.

Physicochemical Properties and Antimicrobial Efficacy of Carvacrol Nanoemulsions Formed by Spontaneous Emulsification

A simple cost-effective method (spontaneous emulsification) for fabricating physically stable antimicrobial nanoemulsions from essential oils is described. These nanoemulsions (10 wt % total oil phase) were formed by titration of a mixture of essential oil (carvacrol), carrier oil (medium chain triglyceride, MCT), and nonionic surfactant (Tween) into an aqueous solution with continuous stirring. Oil phase composition (carvacrol-to-MCT mass ratio) had a major impact on initial droplet diameter, with the smallest droplets (d ≈ 55 nm) being formed at 2.5 wt % carvacrol and 7.5 wt % MCT. Surfactant type also had an appreciable impact on mean droplet diameter, with Tween 80 giving the smallest droplets (d ≈ 55 nm) from a group of food-grade nonionic surfactants (Tween 20, 40, 60, 80, and 85). The droplet size also decreased (from >5000 to <25 nm) as the total surfactant concentration was increased (from 5 to 20 wt %). The long-term stability and antimicrobial efficacy of selected nanoemulsions was examined at ambient temperature. The stability of the nanoemulsions to droplet growth during storage decreased as the carvacrol concentration in the oil phase increased. Conversely, the antimicrobial efficacy of the nanoemulsions increased as the carvacrol concentration increased. These results have important implications for the design and utilization of nanoemulsions as antimicrobial delivery systems in the food and other industries. They suggest that the carrier oil concentration must be carefully controlled to obtain good physical stability and antimicrobial efficacy.

Effect of Fumed Silica Particles on Water-in-Crude Oil Emulsion: Emulsion Stability, Interfacial Properties, and Contribution of Crude Oil Fractions

The effect of fumed silica particles on water-in-crude oil emulsions was analyzed by stability tests, interfacial tension measurements, dilatational rheology of the interface, rheology of the particles dispersions, and Cryo-SEM analysis. The crude oil studied is a paraffinic one and was separated by distillation in three fractions containing mainly saturate, aromatic, and resin compounds. The stability of emulsions formed from these oil fractions was also studied with or without silica particles. Experiments without particles performed with oil or its fractions underline that the most stable emulsion is formed with the heavy fraction which corresponds to the highest elastic modulus of the interface. Different mechanisms of emulsion stability in the presence of particles were discussed according to the particle wettability. Whatever the oil phase composition, it is obviously noticed that hydrophilic particles destabilize water-in-oil emulsions, whereas hydrophobic particles stabilize them. For hydrophilic ...

Physical Properties and Antimicrobial Efficacy of Thyme Oil Nanoemulsions: Influence of Ripening Inhibitors

Thyme oil-in-water nanoemulsions (pH 3.5) were prepared as potential antimicrobial delivery systems. The nanoemulsions were highly unstable to droplet growth and phase separation, which was attributed to Ostwald ripening due to the relatively high water solubility of thyme oil. Ostwald ripening could be inhibited by mixing thyme oil with a water-insoluble ripening inhibitor (≥60 wt % corn oil or ≥50 wt % MCT in the lipid phase) before homogenization, yielding nanoemulsions with good physical stability. Physically stable thyme oil nanoemulsions were examined for their antimicrobial activities against an acid-resistant spoilage yeast, Zygosaccharomyces bailii (ZB). Oil phase composition (ripening inhibitor type and concentration) had an appreciable influence on the antimicrobial activity of the thyme oil nanoemulsions. In general, increasing the ripening inhibitor levels in the lipid phase reduced the antimicrobial efficacy of nanoemulsions. For example, for nanoemulsions containing 60 wt % corn oil in the lipid phase, the minimum inhibitory concentration (MIC) of thyme oil to inhibit ZB growth was 375 μg/mL, while for nanoemulsions containing 90 wt % corn oil in the lipid phase, even 6000 μg/mL thyme oil could not inhibit ZB growth. This effect is also dependent on ripening inhibitor types: at the same concentration in the lipid phase, MCT decreased the antimicrobial efficacy of thyme oil more than corn oil. For instance, when the level of ripening inhibitor in the lipid phase was 70 wt %, the MICs of thyme oil for nanoemulsions containing corn oil and MCT were 750 and 3000 μg/mL, respectively. The results of this study have important implications for the design and utilization of nanoemulsions as antimicrobial delivery systems in the food and other industries.

Fabrication of vitamin E-enriched nanoemulsions: Factors affecting particle size using spontaneous emulsification

Oil-in-water nanoemulsions are finding increasing use as delivery systems to encapsulate lipophilic bioactive components in functional food, personal care, and pharmaceutical products. We have investigated the influence of system composition and preparation conditions on the particle size of vitamin E acetate (VE)-loaded nanoemulsions prepared by spontaneous emulsification. This method relies on the formation of very fine oil droplets when an oil/surfactant mixture is added to water. The oil-to-emulsion ratio content was kept constant (10wt.%) while the surfactant-to-emulsion ratio (%SER) was varied (from 2.5 to 10wt.%). Oil phase composition (vitamin E to medium chain triglyceride ratio) had a major effect on particle size, with the smallest droplets being formed at 8wt.% VE and 2wt.% MCT. Surfactant type also had an appreciable impact on particle size, with TWEEN® 80 giving the smallest droplets from a group of food-grade non-ionic surfactants (TWEEN® 20, 40, 60, 80, and 85). Surfactant-to-emulsion ratio also had to be optimized to produce fine droplets, with the smallest droplets being formed at SER=10wt.%. Particle size could also be reduced by increasing the temperature and stirring speed used when the oil/surfactant mixture was added to water. By optimizing system composition and homogenization conditions we were able to form VE-loaded nanoemulsions with small mean droplet diameters (d<50nm) and low polydispersity indexes (PDI<0.13). The spontaneous emulsification method therefore has great potential for forming nanoemulsion-based delivery systems for food, personal care, and pharmaceutical applications.