Ultrasound-assisted water-in-palm oil nano-emulsion: Influence of polyglycerol polyricinoleate and NaCl on its stability

A novel pH-responsive emulsion system stabilized by nanocelluloses modified with a rosin-based charge-reversible surfactant

Nanocelluloses as a natural polysaccharide nanoparticle are widely used in preparing Pickering emulsions, but less involved in stimuli-responsive Pickering emulsions, due to complicated covalent modification. In this study, a novel pH-responsive emulsion system was prepared using nanocellulose hydrophobized in situ with a unique pH-responsive surfactant (MPAA) derived from rosin. The headgroup charge of MPAA could be reversibly switched between a cationic form (MPAAH) and an anionic form (MPAANa) via adjusting pH, both of which had excellent water solubility. In acidic condition (pH 4.0), the negatively charged nanocellulose could be hydrophobized in situ by absorbing the cationic MPAAH, and stable and high-viscosity Pickering emulsion gels were obtained. In alkaline condition (pH 10.0), the nanocellulose dispersed in aqueous phase and formed thick aqueous lamellae with negative charge, preventing the flocculation and coalescence of the negatively charged droplets, and oil-in-dispersion emulsions with smaller droplet size and low viscosity were formed. The corresponding properties, such as droplet size, stability, and viscosity could be easily controlled by changing pH. Importantly, MPAA and nanocellulose could be separated and reused multiple times. The work proposed an effective method to achieve multiple recycling and reuse of emulsifiers, showing good economic benefits and potential sustainable applications.

Effect of polysaccharide on structures and gel properties of microgel particle reconstructed soybean protein isolate/polysaccharide complex emulsion gels as solid fat mimetic

In this work, a soybean protein isolate (SPI)/polysaccharide microgel particle reconstructed emulsion gels (MPEG) were fabricated through heat-induced gel (HG)-microgel particle-transglutaminase (TG) induced gel process in the presence of four polysaccharides (κ-carrageenan, κC; konjac glucomannan, KGM; high-acyl gellan, HA and xanthan gum, XG). HG exhibited a higher springiness than that of pig back fat (PBF) regardless of polysaccharide type and concentration. After forming MPEG, the springiness was significantly lowered at ≥0.6 % κC, which made MPEG exhibit similar springiness of PBF; while SPI/KGM, SPI/XG and SPI/HA systems failed to regulate the springiness property. Rheological behavior revealed the loss in elasticity, the increase in the plastic deformation of SPI/κC MPEG, while KGM, XG and HA systems still exhibited elasticity dominated rheological properties. Compared with KGM, XG, the presence of excess κC and HA disturbed the continuous protein network structure, resulting to the aggregation of microgel particles and oil droplets. Disulfide bonds and hydrophobic interactions mainly contributed to the formation of MPEG, while the addition of κC weakened the contribution of them, which was not conducive to the formation of gel network. This study provides a guidance on the development of solid fat mimetic based on the microgel particle emulsion gels.

Fabrication and characterization of oxidized starch-xanthan gum composite nanoparticles with efficient emulsifying properties

This study involved the preparation of nanoparticles by combining oxidized starch (OS) with xanthan gum (XG), and emulsions were prepared from this nanoparticle. The physical and chemical characteristics, as well as the emulsification properties of oxidized starch-xanthan gum composite nanoparticles (OGNP), were analyzed. The findings revealed that the OGNP retained spherical shape after the addition of XG, although their diameter increased from approximately 50-150 to 200-400 nm. Zeta potential decreased with XG content. Moreover, emulsions prepared from OGNP exhibited outstanding thermal stability, also showing enhanced storage stability. In addition, emulsions had different rheological properties at different pH values. The apparent viscosity and shear stress of emulsions under alkaline conditions were lower than that of neutral conditions. NaCl increased the apparent viscosity of OGNP-stabilized emulsions while reducing their thermal stability. The nanoparticles prepared in this study have efficient emulsification properties and can extend the application of OS.

Polyglycerol polyricinoleate and lecithin stabilized water in oil nanoemulsions for sugaring Beijing roast duck: Preparation, stability mechanisms and color improvement

Traditional Beijing roast duck often suffers from uneven color and high sugar content after roasting. Water-in-oil (W/O) nanoemulsion is a promising alternative to replace high concentration of sugar solution used in sugaring process according to similarity-intermiscibility theory. Herein, 3% of xylose was embedded in the aqueous phase of W/O emulsion to replace 15% maltose solution. W/O emulsions with different ratios of lecithin (LEC) and polyglycerol polyricinoleate (PGPR) were constructed by high-speed homogenization and high-pressure homogenization. Distribution and penetration extent of solutions and emulsions through the duck skin, as well as the color uniformity of Beijing roast duck were analyzed. Emulsions with LEC:PGPR ratios of 1:3 and 2:2 had better stability. Stable interfacial film and spatial structure were important factors influencing emulsion stabilization. The stable W/O emulsions could more uniformly distribute onto the surface of duck skin and longitudinally penetrate through the skin than solutions.

Fabrication and Stability Improvement of Monoglyceride Oleogel/Polyglycerol Polyricinoleate-Stabilized W/O High Internal Phase Pickering Emulsions

To decrease the lipid content in water-in-oil (W/O) emulsions, high internal phase Pickering W/O emulsions (HIPPE) were fabricated using magnetic stirring using a combination of monoglyceride (MAG) oleogel and polyglycerol polyacrylate oleate (PGPR) as stabilizers. Effects of MAGs (glyceryl monostearate-GMS, glycerol monolaurate-GML and glycerol monocaprylate-GMC) and internal phase components on the formation and properties of HIPPEs were investigated. The results showed that milky-white stabilized W/O HIPPE with up to 85 wt% aqueous phase content was successfully prepared, and the droplet interfaces presented a network of MAG crystals, independent of the MAG type. All HIPPEs exhibited great stability under freeze-thaw cycles but were less plastic. Meanwhile, GML-oleogel-based HIPPEs had larger particle size and were less thermal stable than GMS and GMC-based HIPPEs. Compared to guar gum, the internal phase components of sodium chloride and sucrose were more effective in reducing the particle size of HIPPEs, improving their stability and plasticity, and stabilizing them during 100-day storage. HIPPEs presented great spreadability, ductility and plasticity after whipping treatment. This knowledge provides a new perspective on the use of oleogels as co-stabilizers for the formation of W/O HIPPEs, which can be used as a potential substitute for creams.

Enhanced fabrication of size-controllable chitosan-genipin nanoparticles using orifice-induced hydrodynamic cavitation: Process optimization and performance evaluation

Chitosan nanoparticles (NPs) possess great potential in biomedical fields. Orifice-induced hydrodynamic cavitation (HC) has been used for the enhancement of fabrication of size-controllable genipin-crosslinked chitosan (chitosan-genipin) NPs based on the emulsion cross-linking (ECLK). Experiments have been performed using various plate geometries, chitosan molecular weight and under different operational parameters such as inlet pressure (1-3.5 bar), outlet pressure (0-1.5 bar) and cross-linking temperature (40-70 °C). Orifice plate geometry was a crucial factor affecting the properties of NPs, and the optimized geometry of orifice plate was with single hole of 3.0 mm diameter. The size of NPs with polydispersity index of 0.359 was 312.6 nm at an optimized inlet pressure of 3.0 bar, and the maximum production yield reached 84.82 %. Chitosan with too high or too low initial molecular weight (e.g., chitosan oligosaccharide) was not applicable for producing ultra-fine and narrow-distributed NPs. There existed a non-linear monotonically-increasing relationship between cavitation number (Cv) and chitosan NP size. Scanning electron microscopy (SEM) test indicated that the prepared NPs were discrete with spherical shape. The study demonstrated the superiority of HC in reducing particle size and size distribution of NPs, and the energy efficiency of orifice type HC-processed ECLK was two orders of magnitude than that of ultrasonic horn or high shear homogenization-processed ECLK. In vitro drug-release studies showed that the fabricated NPs had great potential as a drug delivery system. The observations of this study can offer strong support for HC to enhance the fabrication of size-controllable chitosan-genipin NPs.

Analytics and applications of polyglycerol polyricinoleate (PGPR)-Current research progress

Polyglycerol polyricinoleate (PGPR) is a synthetic food additive containing a complex mixture of various esters. In recent years, there has been a growing trend to use PGPR-stabilized water-in-oil (W/O) emulsions to replace fat in order to produce low-calorie food products. In this respect, it is essential to comprehensively characterize the PGPR molecular species composition, which might enable to reduce its required amount in emulsions and foods based on a better understanding of the structure-activity relationship. This review presents the recent research progress on the characterization and quantitative analysis of PGPR. The influencing factors of the emulsifying ability of PGPR in W/O emulsions are further illustrated to provide new insights on the total or partial replacement of PGPR. Moreover, the latest progress on applications of PGPR in food products is described. Current studies have revealed the complex structure of PGPR. Besides, recent research has focused on the quantitative determination of the composition of PGPR and the quantification of the PGPR concentration in foods. However, research on the quantitative determination of the (poly)glycerol composition of PGPR and of the individual molecular species present in PGPR is still limited. Some natural water- or oil-soluble surfactants (e.g., proteins or lecithin) have been proven to enable the partial replacement of PGPR in W/O emulsions. Additionally, water-dispersible phytosterol particles and lecithin have been successfully used as a substitute of PGPR to create stable W/O emulsions.

Extraction and Emulsification of Carotenoids from Carrot Pomaces Using Oleic Acid

This study aimed to use oleic acid-based ultrasonic-assisted extraction (UAE) to recover carotenoids from carrot pomace and emulsify the enriched-carotenoid oleic acid using spontaneous and ultrasonic-assisted emulsification. The extraction performance of oleic acid was compared with traditional organic solvents, including hexane, acetone, and ethyl acetate. The one-factor experiments were employed to examine the impact of UAE conditions, including liquid-to-solid ratios, temperature, ultrasonic power, and time, on the extraction yield of carotenoids and to find the conditional ranges for the optimization process. The response surface methodology was employed to optimize the UAE process. The second-order extraction kinetic model was used to find the mechanism of oleic acid-based UAE. After that, the enriched-carotenoid oleic acid obtained at the optimal conditions of UAE was used to fabricate nanoemulsions using spontaneous emulsification (SE), ultrasonic-assisted emulsification (UE), and SE-UE. The effect of SE and UE conditions on the turbidity of nanoemulsion was determined. Then, the physiochemical attributes of the nanoemulsion from SE, UE, and spontaneous ultrasonic-assisted emulsification (SE-UE) were determined using the dynamic light scattering method. The extraction yield of carotenoids from carrot pomace by using sonication was the highest. The adjusted optimal conditions were 39 mL/g of LSR, 50 °C, 12.5 min, and 350 W of ultrasonic power. Under optimal conditions, the carotenoid content attained was approximately 163.43 ± 1.83 μg/g, with the anticipated value (166 μg/g). The particle sizes of nanoemulsion fabricated at the proper conditions of SE, UE, and SE-UE were 31.2 ± 0.83, 33.8 ± 0.52, and 109.7 ± 8.24 nm, respectively. The results showed that SE and UE are suitable methods for fabricating nanoemulsions. The research provided a green approach for extracting and emulsifying carotenoids from carrot pomace.

Baru oil (Dipteryx alata vog.) applied in the formation of O/W nanoemulsions: A study of physical-chemical, rheological and interfacial properties

The oil extracted from baru (Dipteryx alata Vog.) seeds is in bioactive compounds and it presents potential to be used in food and cosmetic industries. Therefore, this study aims to provide insights into the stability of baru oil-in-water (O/W) nanoemulsions. For this purpose, the effects of the ionic strength (0, 100 and 200 mM), pH (6, 7 and 8), and storage time (28 days) on the kinetic stability of these colloidal dispersions were evaluated. The nanoemulsions were characterized in terms of interfacial properties, rheology, zeta potential (ζ), average droplet diameter, polydispersity index (PDI), microstructure, and creaming index. In general, for samples, the equilibrium interfacial tension ranged from 1.21 to 3.4 mN.m^-1, and the interfacial layer presented an elastic behavior with low dilatational viscoelasticity. Results show that the nanoemulsions present a Newtonian flow behavior, with a viscosity ranging from 1.99 to 2.39 mPa.s. The nanoemulsions presented an average diameter of 237-315 nm with a low polydispersity index (<0.39), and a ζ-potential ranging from 39.4 to 50.3 mV after 28 days of storage at 25 °C. The results obtained for the ζ-potential suggest strong electrostatic repulsions between the droplets, which is an indicative of relative kinetic stability. In fact, macroscopically, all the nanoemulsions were relatively stable after 28 days of storage, except the nanoemulsions added with NaCl. Nanoemulsions produced with baru oil present a great potential to be used in the food, cosmetic, and pharmaceutical industries.

Mechanisms of lipid oxidation in water-in-oil emulsions and oxidomics-guided discovery of targeted protective approaches

Lipid oxidation is an inevitable event during the processing, storage, and even consumption of lipid-containing food, which may cause adverse effects on both food quality and human health. Water-in-oil (W/O) food emulsions contain a high content of lipids and small water droplets, which renders them vulnerable to lipid oxidation. The present review provides comprehensive insights into the lipid oxidation of W/O food emulsions. The key influential factors of lipid oxidation in W/O food emulsions are presented systematically. To better interpret the specific mechanisms of lipid oxidation in W/O food emulsions, a comprehensive detection method, oxidative lipidomics (oxidomics), is proposed to identify novel markers, which not only tracks the chemical molecules but also considers the changes in supramolecular properties, sensory properties, and nutritional value. The microstructure of emulsions, components from both phases, emulsifiers, pH, temperature, and light should be taken into account to identify specific oxidation markers. A correlation of these novel oxidation markers with the shelf life, the organoleptic properties, and the nutritional value of W/O food emulsions should be applied to develop targeted protective approaches for limiting lipid oxidation. Accordingly, the processing parameters, the application of antioxidants and emulsifiers, as well as packing and storage conditions can be optimized to develop W/O emulsions with improved oxidative stability. This review may help in emphasizing the future research priorities of investigating the mechanisms of lipid oxidation in W/O emulsion by oxidomics, leading to practical solutions for the food industry to prevent oxidative rancidity in W/O food emulsions.

Effects of W/O Nanoemulsion on Improving the Color Tone of Beijing Roast Duck

Traditional Beijing roast duck is often brushed with a high concentration of maltose solution (15% w/v) and shows ununiform color after roasting. A novel W/O nanoemulsion was applied to improve the color tone of Beijing roast ducks and, meanwhile, reduced the amount of sugar. For the W/O emulsion, 3% (w/v) xylose solution as the aqueous phase, soybean oil as the oil phase, and polyglycerol polyricinoleate (PGPR) and whey protein isolate (WPI) as co-emulsifiers were fabricated by high-pressure homogenization. Particle size measurement by Zetasizer and stability analysis by Turbiscan stability analyzer showed that WPI as co-emulsifier and internal aqueous phase at pH 9 decreased the droplet size and improved the emulsion stability. In addition, by color difference evaluation, the W/O nanoemulsion improved the Maillard reaction degree and color tone of Beijing roast duck. The molecular structure and key composition of pigments on the surface of Beijing roast duck skins were also identified and characterized by UV-vis spectroscopy and UHPLC-MS. This study creatively offers theoretical guidance for increasing applications of W/O-nanoemulsion-based Maillard reaction in the roast food industry, especially for the development of reduced-sugar Beijing roast duck with uniform and desired color satisfying consumers' acceptance and marketability.

Sonochemistry: An emerging approach to fabricate biopolymer cross-linked emulsions for the delivery of bioactive compounds

Sonochemistry shows remarkable potential in the synthesis or modification of new micro/nanomaterials, particularly the cross-linked emulsions for drug delivery. However, the trend of utilizing sonochemical emulsions for delivery of food-derived bioactive compounds has been just started. The extension of sonochemistry as a tool for engineering bioactive delivery systems will make the approach more universal and greatly increase its applications in the food industry. This review summarizes different types of biopolymeric cross-linked emulsions (CLEs) synthesized via sonochemical approach, including CLEs, surface-modified CLEs, cross-linked high internal phase emulsions, and some novel systems templated on CLEs. Special emphasis is directed toward the cross-linking mechanisms of biopolymers at the oil-water interfaces under acoustic cavitation and the physicochemical principles underlying sonochemical fabrication. We also highlight the advantages and challenges associated with the delivery performance of each system for bioactive compounds. The potential in delivering bioactives using sonochemical emulsions has not been fully reached. There are still a number of issues that need to be overcome, including low cross-linking degree of biopolymers, degradation of bioactives in sonochemical process, and unclear biological fate of encapsulated bioactive compounds. This review may guide future trends in exploring efficient sonochemical strategies and multifunctional delivery systems for food applications.

Structure and stability characterization of pea protein isolate-xylan conjugate-stabilized nanoemulsions prepared using ultrasound homogenization

Preparation of pea protein isolate-xylan (PPI-X) conjugate-stabilized nanoemulsions using ultrasonic homogenization and the corresponding structure and environmental stability were investigated in this study. Conditions used to prepare nanoemulsions were optimized using a response surface methodology as follows: protein concentration 8.86 mg/mL, ultrasound amplitudes 57 % (370.5 W), and ultrasound time 16 min. PPI-X conjugate-stabilized nanoemulsions formed under these conditions exhibited less mean droplet size (189.4 ± 0.45 nm), more uniform droplet distribution, greater absolute value of zeta-potential (44.8 ± 0.22 mV), and higher protein adsorption content compared with PPI-stabilized nanoemulsions. PPI-X conjugate-stabilized nanoemulsions also exhibited even particle distribution and dense network structure, which might be reasons for the observed high interfacial protein adsorption content of conjugate-stabilized nanoemulsions. Moreover, better stability against environmental stresses, such as thermal treatment, freeze-thaw treatment, ionic strength and type, and storage time was also observed for the conjugate-stabilized nanoemulsions, indicating that this type of nanoemulsions possess a potential to endure harsh food processing conditions. Therefore, results provide a novel approach for the preparation of protein-polysaccharide conjugate-stabilized nanoemulsions to be applied as novel ingredients to meet special requirements of processed foods.

Encapsulation of amino acids in water-in-oil-in-water emulsions stabilized by gum arabic and xanthan gum

In this study, several kinds of amino acids were successfully encapsulated in a W₁/O/W₂ emulsion produced using a two-step emulsification process. Polyglycerol polyricinoleate (PGPR) was used as a hydrophobic emulsifier in the oil phase, while gum arabic (GA) and xanthan gum (XA) were used as an emulsifier and stabilizer in the outer water (W₂) phase, respectively. The stability and encapsulation efficiency of the W₁/O/W₂ emulsions depended on the ratio of W₁/O emulsion to W₂ phase, as well as the concentration of GA and XA within the outer W₂ phase. A W₁/O/W₂ emulsion prepared using 2 % (w/w) GA and 0.3 % (w/w) XA in the W₂ phase exhibited good stability and a high encapsulation efficiency (>80 %) for several amino acids. As the hydrophobicity of amino acids and storage temperature increased, the leakage from the W₁ to W₂ phases increased, which can be attributed to increasing solubility in the oil phase. The encapsulation efficiency of lysine encapsulated in GA-XA-stabilized W₁/O/W₂ double emulsion was over 84 % after 28 days storage at 4 °C. These results indicate that double emulsions may be useful for the encapsulation of amino acids, which may be useful to protect them from their environment and mask bitter flavors.

A Cosmeceutical Topical Water-in-Oil Nanoemulsion of Natural Bioactives: Design of Experiment, in vitro Characterization, and in vivo Skin Performance Against UVB Irradiation-Induced Skin Damages

Introduction

Damage to human skin occurs either chronologically or through repetitive exposure to ultraviolet (UV) radiation, where collagen photodegradation leads to the formation of wrinkles and skin imperfections. Consequently, cosmeceutical products containing natural bioactives to restore or regenerate collagen have gained a remarkable attention as an ameliorative remedy.

Methods

This study aimed to develop and optimize collagen-loaded water-in-oil nanoemulsion (W/O NE) through a D-optimal mixture design to achieve an ideal multifunctional nanosystem containing active constituents. Vit E was included as a constituent of the formulation for its antioxidant properties to minimize the destructive impact of UV radiation. The formulated systems were characterized in terms of their globule size, optical clarity, and viscosity. An optimized system was selected and evaluated for its physical stability, in vitro wound healing properties, and in vivo permeation and protection against UV radiation. In addition, the effect of collagen-loaded NE was compared to Vit C-loaded NE and collagen-/Vit C-loaded NEs mixture as Vit C is known to enhance collagen production within the skin.

Results

The optimized NE was formulated with 25% oils (Vit E: safflower oil, 1:3), 54.635% surfactant/cosurfactant (Span 80: Kolliphor EL: Arlasolve, 1:1:1), and 20.365% water. The optimized NE loaded with either collagen or Vit C exhibited a skin-friendly appearance with boosted permeability, and improved cell viability and wound healing properties on fibroblast cell lines. Moreover, the in vivo study and histopathological investigations confirmed the efficacy of the developed system to protect the skin against UV damage. The results revealed that the effect of collagen-/Vit C-loaded NEs mixture was more pronounced, as both drugs reduced the skin damage to an extent that it was free from any detectable alterations.

Conclusion

NE formulated using Vit E and containing collagen and/or Vit C could be a promising ameliorative remedy for skin protection against UVB irradiation.

Ultrasonic enhanced emulsification process in 3D printed microfluidic device to encapsulate active pharmaceutical ingredients

A new method to prepare polymer encapsulated repaglinide nanoparticles through ultrasonic enhanced microchannel emulsification technique was explored. Using the concept of 3D printing, three different shaped micromixers (T-type, Y-type, and F-type) followed by a serpentine microchannel was fabricated using SS-316. Parametric study was performed on all three fabricated micromixers. The best results were obtained for the Y-microchannel in a microfluidic system alone, which showed a minimum particle size of 513.6 nm with 75.4% encapsulation efficiency (EE). In the selected microchannel, to further reduce the drug particle size and to increase% EE, convective mixing between immiscible fluids was enhanced by implementing ultrasound. Compared to the microfluidic system, particle size and EE were significantly improved in the ultrasonic microfluidic system. The experimental results revealed that the minimum particle size of 75.4 ± 1.3 nm with 82.9 ± 0.2% EE was achieved using an ultrasonic enhanced microfluidic system. The zeta potential of + 29.5 mV was obtained for emulsion prepared using the ultrasonic microfluidic system, whereas + 22 mV was prepared using a microfluidic system. Moreover, a backscattering measurement was performed to predict the stability of prepared emulsions. Integrating the ultrasound with a microfluidic system has proven beneficial for drug encapsulation.

Novel Water-in-Oil Emulsions for Co-Loading Sialic Acid and Chitosan: Formulation, Characterization, and Stability Evaluation

This study was designed to co-load sialic acid (SA) and chitosan in a water-in-oil (W/O) emulsion and investigated its characterization and stability. Emulsions were prepared using two different oils (olive oil and maize oil) and polyglycerol polyricinoleate (PGPR) alone or in combination with lecithin (LE) as emulsifiers. The results revealed that the aqueous phase of 5% (w/v) SA and 2% (w/v) chitosan could form a stable complex and make the aqueous phase into a transparent colloidal state. Increasing the concentration of PGPR and LE presented different effects on emulsion formation between olive oil-base and maize oil-base. Two stable W/O emulsions that were olive oil-based with 1.5% (w/v) PGPR+ 0.5% (w/v) LE and maize oil-based with 2% (w/v) PGPR+ 0% (w/v) LE were obtained. Initial droplet size distribution curves of the two stable emulsions displayed unimodal distribution, and the rheological curves displayed the characteristics of shear thinning and low static shear viscosity. Moreover, the storage stability showed that there was no significant change in droplet size distribution and Sauter mean diameter of the emulsions at room temperature (25 °C) for 30 days. These results indicated that the W/O emulsions could effectively co-load and protect sialic acid and chitosan and thus could be a novel method for increasing the stability of these water-soluble bioactive compounds.

W/O high internal phase emulsion featuring by interfacial crystallization of diacylglycerol and different internal compositions

High internal phase emulsions (HIPEs) show promising application in food and cosmetic industries. In this work, diacylglycerol (DAG) was applied to fabricate water-in-oil (W/O) HIPEs. DAG-based emulsion can hold 60% water and the emulsion rigidity increased with water content, indicating the water droplets acted as "active fillers". Stable HIPE with 80% water fraction was formed through the combination of 6 wt% DAG with 1 wt% polyglycerol polyricinoleate (PGPR). The addition of 1 w% kappa (κ)-carrageenan and 0.5 M NaCl greatly reduced the droplet size and enhanced emulsion rigidity, and the interfacial tension of the internal phase was reduced. Benefiting from the Pickering crystals-stabilized interface by DAG as revealed by the microscopy and enhanced elastic modulus of emulsions with the gelation agents, the HIPEs demonstrated good retaining ability for anthocyanin and β-carotene. This study provides insights for the development of W/O HIPEs to fabricate low-calories margarines, spread or cosmetic creams.

Continuous production of nanoemulsion for skincare product using a 3D-printed rotor-stator hydrodynamic cavitation reactor

In this study, nanoemulsions for skincare products were continuously produced using a hydrodynamic cavitation reactor (HCR) designed with a rotor and stator. The key component of this research is the utilization of a 3D-printed rotor in a HCR for the production of an oil-in-water nanoemulsion. Response surface methodology was used to determine the process conditions, such as speed of the rotor, flow rate, as well as, Span60, Tween60, and mineral oil concentrations, for generating the optimal droplet size in the nanoemulsion. The results showed that a droplet size of 366.4 nm was achieved under the recommended conditions of rotor speed of 3500 rpm, flow rate of 3.3 L/h, Span60 concentration of 2.36 wt%, Tween60 concentration of 3.00 wt%, and mineral oil concentration of 1.76 wt%. Moreover, the important characteristics for consideration in skincare products, such as polydispersity index, pH, zeta potential, viscosity, stability, and niacin released from formulations, were also assessed. For the niacin release profile of emulsion and nanoemulsion formulations, different methods, such as magnetic stirring, ultrasound, and hydrodynamic cavitation, were compared. The nanoemulsion formulations provided a greater cumulative release from the formulation than the emulsion. Particularly, the nanoemulsion generated using the HCR provided the largest cumulative release from the formulation after 12 h. Therefore, the present study suggests that nanoemulsions can be created by means of hydrodynamic cavitation, which reduces the droplet size, as compared to that generated using other techniques. The satisfactory results of this study indicate that the rotor-stator-type HCR is a potentially cost-effective technology for nanoemulsion production.

Water-Dispersible Phytosterol Nanoparticles: Preparation, Characterization, and in vitro Digestion

For improving solubility and bioaccessibility of phytosterols (PS), phytosterol nanoparticles (PNPs) were prepared by emulsification–evaporation combined high-pressure homogenization method. The organic phase was formed with the dissolved PS and soybean lecithin (SL) in anhydrous ethanol, then mixed with soy protein isolate (SPI) solution, and homogenized into nanoparticles, followed by the evaporation of ethanol. The optimum fabrication conditions were determined as PS (1%, w/v): SL of 1:4, SPI content of 0.75% (w/v), and ethanol volume of 16 ml. PNPs were characterized to have average particle size 93.35 nm, polydispersity index (PDI) 0.179, zeta potential −29.3 mV, and encapsulation efficiency (EE) 97.3%. The impact of temperature, pH, and ionic strength on the stability of fabricated PNPs was determined. After 3-h in vitro digestion, the bioaccessibility of PS in nanoparticles reached 70.8%, significantly higher than the 18.2% of raw PS. Upon freeze-drying, the particle size of PNPs increased to 199.1 nm, resulting in a bimodal distribution. The solubility of PS in water could reach up to 2.122 mg/ml, ~155 times higher than that of raw PS. Therefore, this study contributes to the development of functional PS-food ingredients.

Mechanism of Propofol-Lidocaine Hydrochloride Nano-Emulsion on Retinal Ganglion Cytopathic Effect in Diabetic Rats

The study drew attention to the influence mechanism of propofol and lidocaine hydrochloride nanoemulsion (NE) in the retinal ganglion cell pathology in diabetic rats. Specifically, the propofollidocaine hydrochloride NE was prepared using the emulsification method. The microscope and laser particle size analyser were used to observe the morphology and particle size of NE, respectively. Also, the viscosity of the NE and the recovery rate of the main ingredient were explored. 45 adult male Wistar rats were randomly divided into control group (PBS control), model group (diabetes model), and test group (diabetes model+propofol-lidocaine hydrochloride NE), with 15 rats in each group. The three groups were compared for the blood glucose, body weight, TNF-α and IL-1β mRNA levels in retinal tissue, and the number and apoptosis rate of ganglion cells. It was found that the average particle size of the NE was 89.76 nm, the maximum absorption wavelength was 280.0 nm, and the viscosity was 106.49 N/m/s. The average recovery rate of propofol in NE was 99.91%, and that of lidocaine hydrochloride was 99.80%. At 12th week after modeling, the blood glucose of the test group was lower versus the model group (P < 0.05); the blood glucose and body weight of rats in the control group were lower than those in the other two groups (P < 0.001). The test group exhibited lower mRNA levels of TNF-α and IL-1β and apoptosis index of retinal ganglion cells versus the model group (P < 0.05). The model group showed a lower number of retinal ganglion cells versus the other two groups (P < 0.05). It was inferred that propofol-lidocaine hydrochloride NE of a small particle size and good syringeability can notably reduce blood glucose, TNF-α and IL-1β mRNA levels, and retinal ganglion cell apoptosis index, and at the same time increase the number of retinal ganglion cells.

Ultrasonic-assisted preparation of eucalyptus oil nanoemulsion: Process optimization, in vitro digestive stability, and anti-Escherichia coli activity

Eucalyptus oil (EO) is a natural and effective antimicrobial agent; however, it has disadvantages such as poor water solubility and instability. The aim of this study was to investigate the effect of process vessels and preparation process parameters on the particle size of the emulsion droplets using ultrasonic technique and response surface methodology to prepare eucalyptus oil nanoemulsion (EONE). The optimal sonication process parameters in conical centrifuge tubes were confirmed: sonication distance of 0.9 cm, sonication amplitude of 18%, and sonication time of 2 min. Under these conditions, the particle size of EONE was 18.96 ± 4.66 nm, the polydispersity index was 0.39 ± 0.09, and the zeta potential was -31.17 ± 2.15 mV. In addition, the changes in particle size, potential, micromorphology, and anti-Escherichia coli activity of EONE during digestion were investigated by in vitro simulated digestion. The emulsion was stable in simulated salivary fluid, tended to aggregate in simulated gastric fluid, and increased in particle size and potential value in simulated intestinal fluid. EONE showed higher anti-E. coli activity than EO by simulated digestion. These results provide a useful reference for the in vivo antimicrobial application of the essential oil.

Recent advances on food-grade water-in-oil emulsions: Instability mechanism, fabrication, characterization, application, and research trends

Owing to their promising application prospects, water-in-oil (W/O) emulsions have aroused continuous attention in recent years. However, long-term stability of W/O emulsions remains a particularly challenging problem in colloid science. With the increasing demand of consumers for natural, green, and healthy foods, the heavy reliance on chemically synthesized surfactants to achieve long-term stability has become the key technical defect restricting the application of W/O emulsions in food. To design and manufacture W/O emulsions with long-term stability and clean label, a comprehensive understanding of the fundamentals of the W/O emulsion system is required. This review aims to demystify the field of W/O emulsions and update its current research progress. We first provide a summary on the essential basic knowledge regarding the instability mechanisms, including physical and chemical instability in W/O emulsions. Then, the formulation of the W/O emulsion system is introduced, particularly focusing on the use of natural stabilizers. Besides, the characterization and application of W/O emulsions are also discussed. Finally, we propose promising research trends, including (1) developing W/O high internal phase emulsions (HIPEs) as fat mimetic and substitute, (2) promising formulation routine for long-term stable double emulsions, and (3) searching for novel plant-derived stabilizers of W/O emulsions.

Comparison of Water-Removal Efficiency of Molecular Sieves Vibrating by Rotary Shaking and Electromagnetic Stirring from Feedstock Oil for Biofuel Production

Adequate water-removal techniques are requisite to remain superior biofuel quality. The effects of vibrating types and operating time on the water-removal efficiency of molecular sieves were experimentally studied. Molecular sieves of 3 Å pore size own excellent hydrophilic characteristics and hardly absorb molecules other than water. Molecular sieves of 3 Å accompanied by two different vibrating types, rotary shaking and electromagnetic stirring, were used to remove initial water from the reactant mixture of feedstock oil in order to prevent excessive growth or breeding of microorganisms in the biofuel product. The physical structure of about 66% molecular sieves was significantly damaged due to shattered collision between the magnetic bar and molecular sieves during electromagnetic stirring for 1 h. The molecular sieves vibrated by the rotary shaker appeared to have relatively higher water-removal efficiency than those by the electromagnetic stirrer and by keeping the reactant mixture motionless by 6 and 5 wt.%, respectively. The structure of the molecular sieves vibrated by an electromagnetic stirrer and thereafter being dehydrated appeared much more irregular and damaged, and the weight loss accounted for as high as 19 wt.%. In contrast, the structure of the molecular sieves vibrated by a rotary shaker almost remained original ball-shaped, and the weight loss was much less after regenerative treatment for those molecular sieves. As a consequence, the water-removal process using molecular sieves vibrated by the rotary shaker is considered a competitive method during the biofuel production reaction to achieve a superior quality of biofuels.

Hydrodynamic cavitation: A feasible approach to intensify the emulsion cross-linking process for chitosan nanoparticle synthesis

Chitosan nanoparticles (NPs) exhibit great potential in drug-controlled release systems. A controlled hydrodynamic cavitation (HC) technique was developed to intensify the emulsion crosslinking process for the synthesis of chitosan NPs. Experiments were performed using a circular venturi and under varying operating conditions, i.e., types of oil, addition mode of glutaraldehyde (Glu) solution, inlet pressure (P_in), and rheological properties of chitosan solution. Palm oil was more appropriate for use as the oil phase for the HC-intensified process than the other oil types. The addition mode of water-in-oil (W/O) emulsion containing Glu (with Span 80) was more favorable than the other modes for obtaining a narrow distribution of chitosan NPs. The minimum size of NPs with polydispersity index of 0.342 was 286.5 nm, and the maximum production yield (P_y) could reach 47.26%. A positive correlation was found between the size of NPs and the droplet size of W/O emulsion containing chitosan at increasing P_in. Particle size, size distribution, and the formation of NPs were greatly dependent on the rheological properties of the chitosan solution. Fourier transform infrared spectroscopy (FTIR) analysis indicated that the molecular structure of palm oil was unaffected by HC-induced effects. Compared with ultrasonic horn, stirring-based, and conventional drop-by-drop processes, the application of HC to intensify the emulsion crosslinking process allowed the preparation of a finer and a narrower distribution of chitosan NPs in a more energy-efficient manner. The novel route developed in this work is a viable option for chitosan NP synthesis.

Co-encapsulation of L-ascorbic acid and quercetin by gelatin/sodium carboxymethyl cellulose coacervates using different interlayer oils

A two-step emulsification prior to complex coacervation was employed to develop a co-encapsulation technology of hydrophilic and hydrophobic components for nutrition enhancement. Processing parameters of mononuclear ellipse-like microcapsules using gelatin and sodium carboxymethyl cellulose as wall materials were evaluated. The particle size and morphology of microcapsules and the encapsulation efficiency of L-ascorbic acid were significantly affected by the water-oil phase ratio and total biopolymer concentration. The L-ascorbic acid and quercetin co-encapsulated microcapsules with an average size of 65.26 µm showed good physical and chemical stability. The encapsulation efficiencies of L-ascorbic acid and quercetin were 69.91% and 88.21%, respectively. To predict the potential of functional lipids as hydrophobic carriers, microcapsules using soybean oil, olive oil, fish oil, and conjugated linoleic acid as interlayer oils were developed. The encapsulation efficiencies of hydrophobic compounds carried by different oils were similarly high (88.21-93.08%), whereas, hydrophilic ones carried by conjugated linoleic acid had the lowest encapsulation efficiency (32.54%). The interface tension results indicated that the interfacial stability was impaired by a competitive relation between conjugated linoleic acid and hydrophobic emulsifier at the interface, due to their structural similarity. These results provided the guidance for improving the quality of interlayer oils from microcapsules.

Green sonochemical synthesis of BaDy2NiO5/Dy2O3 and BaDy2NiO5/NiO nanocomposites in the presence of core almond as a capping agent and their application as photocatalysts for the removal of organic dyes in water

The present work reports the sonochemical synthesis of DBNO NC (dysprosium nickelate nanocomposite) using metal nitrates and core almond as a capping agent. In addition, the effects of the power of ultrasound irradiation were investigated. The BaDy2NiO5/Dy2O3 and BaDy2NiO5/NiO nanocomposites were synthesized with sonication powers of 50 and 30 W, respectively. The agglomerated nanoparticles were obtained using different sonication powers, including 15, 30, and 50 W. The results showed that upon increasing the sonication power, the particle size decreased. After characterization, the optical, electrical, magnetic, and photocatalytic properties of the NC were studied. The nanocomposites showed an antiferromagnetic behavior. In this study, the photocatalytic degradations of two dyes, AR14 and AB92, were investigated in the presence of DBNO NC. Furthermore, the effects of the amount of photocatalyst, the concentration of the dye solution, the type of organic dye, and light irradiation on the photocatalytic activity of the nanocomposite were studied. The results showed that with an increasing amount of catalyst and decreasing concentration of dye, the photocatalytic activity of the nanocomposite was increased. This activity for the degradation of AR14 is higher than that of AB92. Both AR14 and AB92 dyes show higher photocatalytic degradation under UV irradiation than under Vis irradiation.

Stabilization of water-in-oil emulsion of Pulicaria jaubertii extract by ultrasonication: Fabrication, characterization, and storage stability

This study investigated the effect of ultrasonic treatments on the properties and stability of the water-in-oil (W/O) emulsion of Pulicaria jaubertii (PJ) extract. The study used different ultrasound powers (0, 100, 200, 400, and 600 W) at two storage degrees (4 and 25 °C) for 28 days. The findings showed that the emulsifying properties were improved to different extents after ultrasonic treatments. The treatment at 600 W showed optimum particle size, polydispersity index, emulsifying property, viscosity properties, and release of total phenolic content than the other powers. However, the ultrasonic power of 400 W gave positive effects on creaming index and antioxidant release compared to 600 W. The emulsion stored at 4 °C presented higher stability than that stored at 25 °C during the 28 days of storage. Microscopically, the increase in sonication power up to 600 W reduced particle size and decreased flocculation, thus resulted in stable emulsions, which is desirable for its applications in food systems.

Preparation and drying of water-in-oil-in-water (W/O/W) double emulsion to encapsulate soy peptides

Soy peptide solution (40%, w/w) was successfully encapsulated in a W₁/O/W₂ double emulsion produced by a two-step emulsification process. Polyglycerol polyricinoleate (PGPR) was found to be an effective inner emulsifier compared to Span 60 and lecithin to produce stable W₁/O primary emulsion. The primary emulsion was subsequently emulsified into an outer aqueous phase (W₂) containing octenyl succinic anhydride (OSA) starch and maltodextrin. The droplet size and encapsulation efficiency of the peptide solution in W₁/O/W₂ emulsion were found to depend on the W₁:O ratio, peptide concentration in the inner W₁ phase and homogenization condition of the secondary emulsification step. The double emulsion with the highest encapsulation efficiency (>80%) was prepared by: (i) using 40% (w/w) soy peptide solution as W₁ phase; (ii) controlling W₁:O ratio at 3:7 (w/w) and (iii) homogenizing the emulsion at 10,000 rpm for 3 min. The freeze-dried microcapsule powder of W₁/O/W₂ emulsion showed higher encapsulation efficiency (>70%) compared to spray-dried one. The freeze-dried microcapsule of W₁/O/W₂ double emulsion developed in this study is a promising delivery matrix to encapsulate hydrophilic ingredients including peptides. Fourier-transform infrared spectroscopy (FTIR) spectra of the microcapsule powder indicated good compatibility between peptide and encapsulants.

Stable W/O/W multiple nanoemulsion encapsulating natural tocotrienols and caffeic acid with cisplatin synergistically treated cancer cell lines (A549 and HEP G2) and reduced toxicity on normal cell line (HEK 293)

This work aimed to evaluate the effects of encapsulated tocotrienols (TRF) and caffeic acid (CA) in water-in-oil-in-water (W/O/W) multiple nanoemulsion with cisplatin towards cancer cells. This work is important considering the limited efficacy of cisplatin due to tumour resistance, as well as its severe side effects. A549 and HEP G2 cancer cell lines were utilised for evaluating the efficacy of the encapsulated W/O/W while HEK 293 normal cell line was used for evaluating the toxicity. TRF, CA and CIS synergistically improved apoptosis in the late apoptotic phase in A549 and HEP G2 by 23.1% and 24.9%, respectively. The generation of ROS was enhanced using TRF:CA:CIS by 16.9% and 30.2% for A549 and HEP G2, respectively. Cell cycle analysis showed an enhanced cell arrest in the G0/G1 phase for both A549 and HEP G2. TRF, CA and CIS led to cell death in A549 and HEP G2. For HEK 293, ~33% cell viability was found when only CIS was used while >95% cell viability was observed when TRF, CA and CIS were used. This study demonstrates that the encapsulated TRF and CA in W/O/W with CIS synergistically improved therapeutic efficacy towards cancer cells, as well as lowered the toxicity effects towards normal cells.

Ultrasonic assisted water-in-oil emulsions encapsulating macro-molecular polysaccharide chitosan: Influence of molecular properties, emulsion viscosity and their stability

An ultrasonic technique was applied to formulation of two-phase water-in-paraffin oil emulsions loading a high-molecular polysaccharide chitosan (CS) and stabilized by an oil-soluble surfactant (Span80) at different operational conditions. The influence of chitosan molecular properties, phase volume ratio (φ_w), Span80 volume fraction (φ_s) and ultrasonic processing parameters were systemically investigated on the basis of mean droplet diameter (MDD) and polydispersity index (PDI) of emulsions. It was observed that the molecular weight (M_w) of CS was an important influential factor to MDD due to the non-Newtonian properties of CS solution varying with M_w. The minimum MDD of 198.5 nm with PDI of 0.326 was obtained with ultrasonic amplitude of 32% for 15 min at an optimum φ_w of 35%, φ_s of 8%, probe position of 2.2 cm to the top of emulsion, while CS with M_w of 400 kDa and deacetylation degree of 84.6% was used. The rise of emulsion viscosity and the reduction of negative zeta potential at φ_w increasing from 5% to 35% were beneficial to obtain finer droplets and more uniform distribution of emulsions, and emulsion viscosity could be represented as a monotonically-decreasing power function of MDD at the same φ_w. FTIR analysis indicated that the molecular structure of paraffin oil was unaffected during ultrasonication. Moreover, the emulsions exhibited a good stability at 4 °C with a slight phase separation at 25 °C after 24 h of storage. By analyzing the evolution of MDD, PDI and sedimentation index (SI) with time, coalescence model showed better fitting results as comparison to Ostwald ripening model, which demonstrated that the coalescence or flocculation was the dominant destabilizing mechanism for such W/O emulsions encapsulating CS. This study may provide a valuable contribution for the application of a non-Newtonian macromolecule solution as dispersed phase to generate nano-size W/O emulsions via ultrasound, and widen knowledge and interest of such emulsions in the functional biomaterial field.

Ultrasound-assisted production of palm oil-based isotonic W/O/W multiple nanoemulsion encapsulating both hydrophobic tocotrienols and hydrophilic caffeic acid with enhanced stability using oil-based Sucragel

In this work, the effects of thickeners and tonicity towards producing stable palm oil-based water-in-oil-in-water (W/O/W) multiple nanoemulsion using ultrasound and microfluidizer were investigated. Palm oil, Sucragel, polyglycerol polyricinoleate, Tween 80, Xanthan gum, and NaCl were used. W/O/W was formed under the optimized conditions of ultrasound at 40% amplitude and for 180 s of irradiation time, whereas for the microfluidizer, the optimized conditions were 350 bar and 8 cycles. This is the first work that successfully utilized Sucragel (oil-based thickener) in imparting enhanced stability in W/O/W. W/O/W with isotonic stabilization produced the lowest change in the mean droplet diameter (MDD), NaCl concentration, and water content by 1.5%, 2.6%, and 0.4%, respectively, due to reduced water movement. The final optimized W/O/W possessed MDD and dispersity index of 175.5 ± 9.8 and 0.232 ± 0.012, respectively. The future direction of formulating stable W/O/W would be by employing oil phase thickeners and isotonicity. The observed ~12 times lesser energy consumed by ultrasound than microfluidizer to generate a comparable droplet size of ~235 nm, further confirms its potential in generating the droplets energy-efficiently.