Emulsifying potential of Hypnea musciformis carrageenan: A natural alternative for oil-in-water emulsions

In food industries, many active compounds are lipophilic in nature. These compounds can be encapsulated to protect them from evaporation or oxidation, to control the release of the compounds and to facilitate the incorporation of the compounds in aqueous medium. Alginate, a hydrophilic polyanionic biopolymer derived from plant, can used as an encapsulant to entrap the oil under mild conditions. For certain food and beverages applications, the beads containing oil are stored in liquid medium before use or they are incorporated into a liquid product. This may cause oil leakage from the beads to the storage medium and thus, reducing the oil content or contaminating the quality of the liquid medium. This research aimed to encapsulate high oil-loaded alginate beads, coat them with chitosan and invesigate how well oil is retained within the chitosan-coated beads during storage in liquid medium. Preliminary research includes the preparation of a stable alginate-based O/W emulsion with monodisperse oil droplet size. Non-ionic surfactants (i.e., Tween 80 and Span 20) were incorporated in the alginate based O/W emulsion. The synergistic effects of alginate and surfactants showed improvement on the O/W emulsion properties which were evaluated in terms of oil droplet size and emulsion stability. The size distribution of oil droplets was narrow and monomodal at 2 %w/v of alginate and 1 %w/v of surfactants, even at an oil loading of 70 %v/v. The emulsions formed were also stable. Subsequently, the alginate based O/W emulsion was extruded into a gelation bath containing calcium ions forming encapsulated alginate beads containing oil and was coated with chitosan. The O/W emulsion formulation containing alginate and surfactants blend yielded beads with high encapsulation efficiencies (i.e., > 98%), with or without coating. The SEM images showed rough and porous surface on 50 %v/v beads suggesting less alginate-chitosan interaction compared to 10 %v/v beads which had smooth surface. From the confocal images, more chitosan was bound on the surface of alginate core containing lower oil loading and when 2-step coating process was used, thus resulting in a thicker and denser coating. This result was consistent with the mechanical strength data where thicker coating ruptured at higher applied force. Surprisingly, thicker coating resulted in higher oil leakage during storage. This result indicates that the increased chitosan-alginate binding generated higher internal pressure within the beads. Consequently, more oil were squeezed out from the beads during storage. Under the experimental conditions, the 1-step coating process gave the lowest oil leakage (< 0.1% at 22 days of storage) at both 10% v/v and 50 % v/v oil loading, compared to the beads without coating or beads coated using a 2-step process. In conclusion, an O/W emulsion formulation that allows high encapsulation efficiency has successfully been developed and the oil leakage during storage has effectively been minimized by chitosan coating.

The effect of emulsifiers, emulsion stabilizer (maltodextrin, MD), and β-cyclodextrin (BCD) on physical and oxidative properties of oil-in-water (O/W) emulsions (5%, 20%, 40% of oil, w/w) was investigated. Four different emulsifiers were selected based on their structure: two types of protein-based emulsifiers (sodium caseinate, SC; and whey protein isolate, WPI), and two types low molecular weight emulsifiers (LMEWs: lecithin, LEC; and Citrem, CITREM). Physical and oxidative stability of emulsions prepared with these emulsifiers together with MD were compared based on their creaming index (CI), viscosity, droplet size, zeta potential, peroxide and p-anisidine values. LMWE-stabilized emulsions (with LEC or CITREM) had better creaming stability with lower droplet sizes whereas protein-stabilized emulsions (with SC or WPI) had higher viscosities. Droplet size was the lowest when CITREM was used, which increased with increasing oil concentration for all emulsifiers. Formulation with the lowest CI value and droplet size was considered to be more prone to oxidation; therefore, a 1:1 (w/w) combination of CITREM with BCD was used to stabilize the emulsions to improve the oxidative as well as physical stability. Added BCD significantly increased the storage stability of emulsions by reducing CI and droplet size values with a simultaneous increase in the viscosity, both at room temperature and at storage conditions (at 4 and 55 o C). However, the oxidative as well as physical stability of BCD added emulsions were not improved, neither toward heat- nor light-induced lipid oxidation. PRACTICAL APPLICATION: This work investigated the effects of emulsifiers and dextrins on the stability of oil-in-water (O/W) emulsions. Both maltodextrin (MD) and β-cyclodextrin (BCD) addition resulted in enhanced physical stability, the latter being more effective. The findings can be applied to formulate emulsions with improved shelf life within the limits of allowed daily intake (ADI) level of BCD (5 mg/kg bw per day).

A combined treatment using both low-frequency (20 kHz) and high-frequency ultrasounds (1.63 MHz) is a promising new process to stabilize emulsions with minimalist formulation. In order to optimize process parameters, a Doehlert experimental design was performed with oil-in-water emulsions, presently used for cosmetic products, composed of water, caprylic/capric triglycerides and oleic acid. Effects of treatment time, oil content and oleic acid content were studied on emulsion properties (droplet size, polydispersity index, ζ-potential and yield of oil incorporation) and on emulsion stability after a 28-day storage (creaming index, Turbiscan stability index (TSI) and oil release). From experimental data, a model was established that allowed to study effects of each parameter and their interactions on emulsion formation and stability. Oleic acid content had a great impact on emulsion formation: It reduced droplet size, PDI and ζ-potential and increased yield of oil incorporation. However, a critical value could be highlighted, beyond which oleic acid effects reversed. Treatment time had an important beneficial effect on emulsion stability as it decreased creaming index, TSI and oil release after 28 days of storage. Oil content had a negative effect on emulsion formation and on emulsion stability. However, treatment time and oil content often had a beneficial synergistic effect. The optimized conditions for emulsion processing were obtained through a desirability approach. They were experimentally validated.

The correlation between interfacial properties and emulsion microstructure is a topic of special interest that has many industrial applications. This study deals with the comparison between the rheological properties of oil-water interfaces with adsorbed proteins from legumes (chickpea or faba bean) and the properties of the emulsions using them as the only emulsifier, both at microscopic (droplet size distribution) and macroscopic level (linear viscoelasticity). Two different pH values (2.5 and 7.5) were studied as a function of storage time. Interfaces were characterized by means of dilatational and interfacial shear rheology measurements. Subsequently, the microstructure of the final emulsions obtained was evaluated thorough droplet size distribution (DSD), light scattering and rheological measurements. Results obtained evidenced that pH value has a strong influence on interfacial properties and emulsion microstructure. The best interfacial results were obtained for the lower pH value using chickpea protein, which also corresponded to smaller droplet sizes, higher viscoelastic moduli, and higher emulsion stability. Thus, results put forward the relevance of the interfacial tension values, the adsorption kinetics, the viscoelastic properties of the interfacial film, and the electrostatic interactions among droplets, which depend on pH and the type of protein, on the microstructure, rheological properties, and stability of legume protein-stabilized emulsions.

Effects of regenerated cellulose on oil-in-water emulsions stabilized by sodium caseinate

In this study, the droplet size distribution, rheological properties, and stability of dairy cream-based emulsions homogenized with different sucrose fatty acid ester (SFAE, a non-ionic small-molecule emulsifier) concentrations (0.08%, 0.16%, and 0.24% w/w) at different homogenization pressures (10 MPa and 20 MPa) were examined. Homogenization at a high pressure resulted in a smaller droplet size and narrower droplet size distribution. The D[4,3] (volume-weighted mean) and D[3,2] (surface-weighted mean) values of the emulsions decreased with an increase in the SFAE concentration. The flow properties of the emulsions homogenized with SFAE showed shear-thinning (n=0.21–0.46) behavior. The apparent viscosity (ηa,10) and consistency index (K) of the homogenized emulsions were lower than those of the control sample that is non-homogenized and without SFAE, and decreased with an increase in SFAE concentration. The storage modulus (G') and loss modulus (G") of all emulsions homogenized with SFAE were also lower than those of the control sample. The stability of all emulsions with SFAE did not show any significant change for 30 d at 5°C. However, the emulsions stored at 40°C were unstable over the storage period. Therefore, the addition of SFAE enhanced the stability of dairy cream emulsions during storage at refrigeration temperature (5°C).

Introduction Clouds are composed of atmospheric aerosols, micrometer sized aqueous droplets that are suspended in the air. These atmospheric aerosols play a key role in weather patterns and planet warming/cooling, making the understanding of their formation and propagation mechanisms highly important.[1] Despite the critical role aerosols play, there is still a fundamental lack in understanding of the processes that drive their formation and growth because there is no direct way to measure the surface tension of aerosol droplets in the atmosphere. In Köhler theory, which governs the formation and growth of aerosols, aerosol formation activity is driven by size and surface tension of the droplet, making an accurate measurement of aerosol surface tension integral to fully understanding cloud formation and evolution properties. In this study we utilize a new laser-based technique to measure the surface tension of micrometer sized droplets through droplet-surface capillary resonance and their response to naturally occurring pinene and limonene molecules exposed to the droplet surface. QELS Approach Thermal fluctuation drives the formation of capillary waves at a liquid interface, which can be observed with the quasi-elastic light scattering (QELS) technique (Figure 1). In our previous reports, the spontaneous resonance of thermally-induced capillary waves has been demonstrated on liquid surfaces with spatial confinement by a microchannel[2] and by a circular aperture.[3] Characteristic peaks corresponding to the capillary resonance appear in the QELS power spectrum. From the peak frequencies and spatial restriction conditions, surface tension can then be calculated.[4] Experimental Method In this work, micrometer sized aqueous droplets were generated by an ink-jet printer system and were immobilized in the path of a focused laser. Humid air was flown over the droplet to maintain size and shape, and QELS spectra collection/surface tension monitoring was started. Next, pinene or limonene were introduced to the air stream, interacting directly with the confined droplets. Surface tension properties were immediately affected by the presence of the hydrophobic molecules, causing the QELS spectra shape to change. The QELS spectra were monitored until equilibrium was reached. Finally, the trend in the surface tension of the droplets was calculated for each sample at various points during exposure to the surfactant molecules. Results and Conclusions In this study, we used the QELS method to probe the surface properties of micrometer sized droplets under a controlled atmosphere containing naturally occurring surfactant molecules. The results show that the presence of these hydrophobic molecules causes a clear suppression of the surface tension, which greatly impacts the aerosol droplet formation and growth properties, in turn impacting cloud formation and other related phenomena. The understanding of the influence of these molecules on the surface tension of aerosol droplets is expected to lead to enhanced knowledge on aerosol droplet formation mechanisms, which play a key role in cloud formation and weather phenomena.

Double emulsions have been the focus of several studies due to their advantages such as trapping dispersed phase droplets, delaying the release, masking taste-odor, and providing protection against oxidation. In this study, double emulsions (w/o/w) were prepared by different emulsifying methods including one-step, two-steps and membrane methods to assess their emulsion yield and stability. Results showed that one-step method was preferable for zeta potential and polydispersity index but similar in droplet size as in membrane method. Due to its simplicity and ease of use, one step method was further studied in an optimization study to evaluate factors affecting droplet size and polydispersity index. Under optimum conditions (oil ratio: 35.1%, emulsifier ratio: 6.9%, homogenization speed: 15000 rpm and homogenization time: 5 min), droplet size and polydispersity index were 180.7±6.6 nm and 0.13±0.01, respectively. pH of the resultant emulsion was 2.89±0.01, conductivity was 9.65±0.05 mS/cm, emulsion stability was 8.02±0.66%, and zeta potential was -50.30±1.70 mV. This study demonstrated that nano-scale emulsion and highly stable emulsions can be obtained for various applications in the food industry under optimum conditions by a single-step method.

Effect of heating temperature of a novel wheat-derived surfactant on a mixture of thyme essential oil/surfactant and on the final emulsions

Encapsulation of citral in formulations containing sucrose or trehalose: Emulsions properties and stability

The physical and oxidative stabilities of Pickering emulsion stabilized by starch particle and small molecular surfactant

Production of more sustainable emulsions formulated with eco-friendly materials

Effect of polysaccharide emulsifiers on the fabrication of monodisperse oil-in-water emulsions using the microchannel emulsification method

Different cationic potato, maize, and waxy maize starches were evaluated for their emulsifying properties. Emulsions were prepared using 20% (w/w) arachidic oil and 80% (w/w) water. Emulsions with the cationic starches as emulsifier in a concentration ranging from 1% to 5% (w/w) were prepared and characterized by droplet size and viscosity measurements, and the stability was evaluated visually and by electrical conductance measurements. None of the cationic potato, waxy maize starches, and maize starches with a low degree of substitution (DS) showed adequate emulsifying properties. Emulsions prepared using non-pregelatinized (C ☆ bond 05914, 2% and 5% w/w; C ☆ bond 05907, 5% w/w) and pregelatinized (C ☆ bond 12504, 5% w/w) cationic maize starches with high-DS were visually stable. The initial mean droplet volume diameter of the emulsions prepared with these cationic starches in a 5% (w/w) concentration was similar and ranged from 2.40 to 2.84 μm however, there was an important difference in droplet size distribution. The droplet size distribution of the emulsions prepared using the non-pregelatinized high-DS cationic starches was markedly narrower than in the case of the emulsions prepared using the pregelatinized high-DS cationic starches. The droplet size of the emulsions remained almost constant during 120 days of storage. Visual inspection and electrical conductance measurements showed that these emulsions were stable for at least 120 days.

Although the use of oil-in-water (O/W) emulsions as metalworking fluids is widespread, the mechanisms of emulsion lubrication are not yet well understood. Several theories have been proposed but there is not a clear agreement about the effect of different operating conditions and emulsion properties on the lubricating performance of O/W emulsions. In the present study, the film forming ability of O/W emulsions as a function of emulsifier concentration is studied. The emulsifier content exerts a strong influence on all the emulsion properties, such as stability, droplet size distribution, surface and interfacial tension, wetting ability, etc., as well as on the lubricating behaviour, so it has been used to ascertain the relationship between all the properties involved. Three different emulsifiers—anionic, nonionic and cationic—were used at different concentrations in the design of lubricant O/W emulsions. Experimental results show that the work of adhesion of oil droplets on the metal surface is a valuable parameter to predict the ability of emulsions to form thick films in elastohydrodynamic (EHD) contacts. The influence of pH value of O/W emulsions on their lubricating behaviour is also verified. The overall conclusion is that the interactions between metal and oil droplets rule the mechanism of lubrication and that this interaction is primarily controlled by emulsifier concentration.