Preferential solubilization behaviours and stability of some phenolic-bearing essential oils formulated in different microemulsion systems

The solubilization behaviour of a number of essential oils (EOs) containing volatile phenolic constituents was investigated in five different micellar solutions. These oils include clove bud (Eugenia caryophyllata), thyme (Thymus serpyllum) and oregano (Thymus capitatus). Ternary and pseudo‐ternary phase diagrams were constructed to assess the ability for microemulsion formation and dilutability of each system using non‐ionic surfactants. Results showed that Tween 20 (T20) was more suitable to solubilize these oils compared with Tween 80 (T80). Clove EO was found to be easily microemulsifiable compared with the other EOs, whereas oregano showed the least tendency to form a microemulsion. Particle sizes measured at different dilution lines ranged between 5.9 and 16.9 nm. The chemical composition of each EO was revealed by gas chromatography and was correlated with the observed solubilization behaviour. The presence of solubilization enhancers like poly‐ols and short‐chain alcohols improved solubilization of all EOs; however, establishment of new dilution lines was controlled by EO type. Physical stability assessment showed that all microemulsions were stable against alternate freeze/thaw cycles which extended for 1 week. On the contrary, each system showed different temperature sensitivity in the thermal stress assessment. The results of this investigation can be useful in fabrication of thermodynamically stable aqueous system carrying aromatic and bioactive phenolics for different applications in personal hygiene, cosmetic, fragrance and pharmaceutical products.     

Formulation of a cosurfactant-free O/W microemulsion using nonionic surfactant mixtures

ABSTRACT:  A cosurfactant-free O/W microemulsion composed of oil, a mixture of hydrophilic and hydrophobic surfactants, and water has been developed using food-grade components as a nutrient delivery system. We started our investigation to monitor the phase behavior of this system based on a hydrophilic surfactant (Tween 80). From a phase diagram, the weight ratio of 5.4:33.8:60.8 = oil:surfactant:water was selected as a combination ratio for the O/W microemulsion system. We also investigated the combination effect of different hydrophobic surfactants to Tween 80 on microemulsion formation. Use of hydrophobic surfactants with Tween 80 produced smaller droplets than Tween 80 alone. Rheological studies showed that all microemulsions followed shear-thinning behavior. The turbidity of microemulsions did not change after accelerated stability tests, indicating that this microemulsion system was stable under the given harsh conditions. When docosahexaenoic acid (DHA) oil was applied to this microemulsion system, the particle size and the turbidity were not significantly changed. Dilution with a different aqueous medium, either water or acidic fluid, did not significantly change the microemulsion turbidity. DHA oil incorporated in microemulsion showed higher oxidation stability than free DHA oil.     

Lemon oil solubilization in mixed surfactant solutions: Rationalizing microemulsion & nanoemulsion formation

Lipophilic functional ingredients are usually incorporated into aqueous-based foods and beverages in the form of colloidal dispersions. In this study, we investigated the rate and extent of solubilization of emulsified lemon oil in mixed non-ionic surfactant solutions (buffer: propylene glycol = 2:1): sucrose monopalmitate (SMP) and/or Tween 80 (T80). The influence of surfactant concentration, type, and mixing ratio on lemon oil solubilization was investigated, with the aim of identifying suitable conditions for preparing stable microemulsions and nanoemulsions. Solubilization was monitored by measuring changes in light scattering by lemon oil droplets after they were dispersed in surfactant solutions (pH 7). The solubilization process was rapid (<few minutes), with the rate increasing with increasing surfactant concentration. For a particular surfactant type and concentration, lemon oil was transferred from nanoemulsion droplets into microemulsion droplets until a critical lemon oil concentration (C_sat) was reached, after which it remained as nanoemulsion droplets. The value of C_sat increased with increasing surfactant concentration and was higher for SMP than Tween 80. The impact of storage at pH 3.5 on the physical stability of microemulsions and nanoemulsions was examined. Acid stable colloidal dispersions could not be formed using SMP alone. However, relatively stable nanoemulsions and microemulsions could be formed when ≥75 or 50 wt% Tween 80 was incorporated into the surfactant phase, respectively. This study provides important information for the rational design of food-grade colloidal delivery systems for encapsulating and delivering functional lipids for food and beverage applications.     

共轭亚油酸多重乳状液的制备及稳定性研究

以多重乳状液相对体积为衡量标准,借助显微镜直接观察,探讨油水相质量比、亲油亲水乳化剂质量比、乳化剂的HLB值、乳化剂的含量等因素对共轭亚油酸多重乳状液体系稳定性的影响.结果表明,单一乳化剂体系中,以Tween80作亲水乳化剂制备的多重乳状液稳定性较好.当m(内水相):m(油相):m(外水相)=1:5:1.3,m(Span80):m(Tween80)=9,乳化剂的含量为9.7%时,多重乳液相对体积达到93%.复合乳化剂体系中,在第一相的HLB值为7.4,m(复合乳化剂):m(Tween80)=9,乳化剂质量分数为6.67%时,稳定性最好.     

Stability and characterisation of phospholipid-based curcumin-encapsulated microemulsions

The ternary phase diagram of a curcumin-encapsulated O/W microemulsion system using food-acceptable components, lecithin and Tween 80 as the surfactants and ethyl oleate as the oil phase, was constructed. The stability and characterisation of curcumin in microemulsion were investigated. The results indicated that a composition of curcumin microemulsion (DI water: surfactants (the mole ratio of lecithin/Tween 80 was 0.3): EO = 10:1.7:0.4 in wt ratio) was stable for 2 months with an average diameter of 71.8 ± 2.45 nm, as detected by UV–Vis spectra and diameter distributions. The microemulsion possesses an ability to be diluted with aqueous buffer without destroying its structure for 48 h. A skin permeation study for testing the penetration effect of various curcumin loading in the microemulsions with different particle diameters was also performed and discussed in this contribution.     

鱼油微乳液的制备与特性研究

目的制备鱼油微乳液并研究其特性。方法采用食用大豆油和丙三醇作为鱼油的油相溶剂,失水山梨醇油酸酯聚氧乙烯醚(Tween 80)和乳糖(9:1,w/w)为表面活性剂相,制备了O/W型鱼油微乳液。拟三元相图法考察了盐度和pH对微乳液区的影响,测定了鱼油微乳的电导率变化和粒径大小,研究了微乳液的流变特性。结果该鱼油微乳液具有较好的耐酸性和耐盐性,平均粒径在10～100 nm之间,稳定性良好。流变特性研究表明表面活性剂相和油相质量比为9∶1,含水量80%(w/w)的鱼油微乳液具有剪切变稀的流变行为,属于拟塑性流体。结论鱼油微乳液制备简便,稳定性良好,是包封鱼油的新方法。     

聚甘油单月桂酸酯-油酸微乳体系的构建及其性能

为构建安全高效的微乳体系,提高姜黄素的溶解度,拓展微乳液及姜黄素在食品中的应用,制备具有较高姜黄素溶解度、可无限稀释的食品级微乳液。以油酸和不同聚合度的聚甘油单月桂酸酯、不同碳链长的醇为原料,通过对拟三元相图的分析,筛选表面活性剂和助表面活性剂,研究表面活性剂与助表面活性剂质量比（Km）、水相pH值和NaCl浓度对微乳体系相行为的影响,用电导率法分析微乳液的结构,用激光粒度仪和透射电镜测定观察微乳液滴的粒径、微观形貌。结果表明,以质量比为2∶1的六聚和十聚甘油单月桂酸酯复配为表面活性剂,以乙醇为助表面活性剂,Km=1/2,制备的微乳液效果最好,微乳区域面积占比最大,微乳液滴呈均一球形,粒径在10～100?nm之间。非中性的水相、NaCl的加入均会导致微乳区域面积占比的减小和最小可稀释比的增大。当表面活性剂与油相质量比为9∶1时,能够形成可无限稀释微乳体系,该体系结构在含水量小于45%时为W/O型,继续增加含水量,体系结构逐渐转变为双连续型,含水量超过60%时为O/W型。姜黄素微乳化不影响姜黄素生物活性,且姜黄素的溶解度可达4.87?mg/mL,可有效地解决姜黄素溶解性差、稀释性差的问题,说明微乳液是姜黄素的优良载体。     

Alginate‐Based Emulsion Template Containing High Oil Loading Stabilized by Nonionic Surfactants

Oil‐in‐water (O/W) emulsion‐gel systems containing high oil payloads are of increasing interest for food applications because of the reduction in encapsulation cost, consumption frequency or volume of food products. This study shows a facile approach to prepare stable alginate‐based O/W emulsions at high oil loading using a mixture of nonionic surfactants (Tween 80 and Span 20) as a template to form gelled‐emulsions. The synergistic effects of alginate and surfactants on the O/W emulsion properties were evaluated in terms of oil droplet size and emulsion stability. At 2% (w/v) of alginate and 1% (w/v) of surfactants, the size distribution of oil droplets was narrow and monomodal, even at an oil loading of 70% (v/v). The emulsions formed were stable against phase separation. The oil droplet size could be further reduced to below 1 μm using a high‐shear homogenizer. The emulsions formed could be easily molded and gelled into solids of different shapes via ionic gelation. The findings of this study create possible avenues for applications in food industries.     

Solubilisation of soybean oil in microemulsions using various surfactants

Microemulsions are transparent, isotropic solutions of oil, water and surfactant (and possibly cosurfactant) which are thermodynamically stable, and have been much studied in terms of pharmaceutical and cosmetic applications. However, the application of microemulsions in foods has been limited both due to toxic or irritant nature of ionic surfactants and the difficulty of solubilising large triglycerides. Three surfactants, food-grade ethoxylated mono- and diglycerides (EMD) and phospholipids, and non-food-grade polyoxyethylene oleyl ether (POE) were examined for their ability to form microemulsions using soybean oil, and their areas of formation expressed on phase diagrams. Microemulsions prepared with EMD and phospholipids required the presence of a short-chain alcohol for formation. Both oil/water (o/w) and water/oil (w/o) microemulsions could be formed using EMD, and the microemulsion area of the phase diagram increased on addition of sucrose and increase in temperature. Depending on sucrose and ethanol concentrations, microemulsions formed with EMD were found to retain their integrity at temperatures below which they formed. Microemulsions could be formed using phospholipids, but only at high surfactant concentration and in the presence of a short-chain alcohol. O/w microemulsions containing 10% oil (w/w) were prepared with POE at surfactant concentrations of >20% (w/w). Dynamic light scattering of microemulsion samples diluted with water indicated particle radii of 6.5 nm. Freeze-fracture SEM showed the structures to be of a droplet type, however, this was more evident at higher surfactant/oil concentrations. The results indicated that it is possible to formulate microemulsions at low EMD and POE surfactant concentration. These microemulsions systems may potentially be used for encapsulation of oil-soluble bioactives, e.g. α-tocopherol, in food systems.     

Catastrophic inversion and rheological behavior in soy lecithin and Tween 80 based food emulsions

Emulsions inversion occurs in many industrial processes and may be influenced by the formulation conditions, composition and emulsification protocols. In this work, the influence of emulsifiers and stirring on catastrophic inversion (O/W to W/O) was evaluated. Emulsions were prepared with different stirring rates, using soy lecithin and Tween 80, at 2 and 5 wt%. The aqueous phase was distilled water with 1 wt% NaCl and the oil phase was soy oil. These emulsions were analyzed by conductivity, stability, microscopy and rheology assays. The most stable emulsions presented inversion with a smaller amount of the external phase. Rheological analysis showed that, with a higher concentration of emulsifier, it is better to use Tween 80 when lower viscosity is desired, while soy lecithin is more appropriate for higher viscosity products. The oscillatory tests showed that while the emulsions prepared using Tween 80 exhibited concentrated solution behavior, those prepared with soy lecithin exhibited strong gel behavior.     

In vitro and in vivo antifungal activity of a water-dilutable cassia oil microemulsion against Geotrichum citri-aurantii

BACKGROUND: Recently, food‐grade microemulsions have been of increasing interest to researchers and have shown great potential in industrial applications. In this study a food‐grade water‐dilutable microemulsion system with cassia oil as oil, ethanol as cosurfactant, Tween 20 as surfactant and water was developed and its antifungal activity in vitro and in vivo against Geotrichum citri‐aurantii was assessed. RESULTS: The phase diagram results confirmed the feasibility of forming a water‐dilutable microemulsion based on cassia oil. One microemulsion formulation, cassia oil/ethanol/Tween 20 = 1:3:6 (w/w/w), was selected with the capability to undergo full dilution with water. The average particle size was 6.3 nm. The in vitro antifungal experiments showed that the microemulsion inhibited fungal growth on solid medium and prevented arthroconidium germination in liquid medium and that cassia oil had stronger activity when encapsulated in the microemulsion. The in vivo antifungal experiments indicated that the water‐dilutable microemulsion was effective in preventing postharvest diseases of citrus fruits caused by G. citri‐aurantii. CONCLUSION: The results of this study suggest a promising utilisation of water‐dilutable microemulsions based on essential oils for the control of postharvest diseases. Copyright © 2012 Society of Chemical Industry     

Antibacterial Effects of Allspice, Garlic, and Oregano Essential Oils in Tomato Films Determined by Overlay and Vapor-Phase Methods

ABSTRACT:  Physical properties as well as antimicrobial activities against  Escherichia coli  O157:H7,  Salmonella enterica , and  Listeria monocytogenes  of allspice, garlic, and oregano essential oils (EOs) in tomato puree film-forming solutions (TPFFS) formulated into edible films at 0.5% to 3% (w/w) concentrations were investigated in this study. Antimicrobial activities were determined by 2 independent methods: overlay of the film on top of the bacteria and vapor-phase diffusion of the antimicrobial from the film to the bacteria. The results indicate that the antimicrobial activities against the 3 pathogens were in the following order: oregano oil > allspice oil > garlic oil.  Listeria monocytogenes  was less resistant to EO vapors, while  E. coli  O157:H7 was more resistant to EOs as determined by both overlay and vapor-phase diffusion tests. The presence of plant EO antimicrobials reduced the viscosity of TPFFS at the higher shear rates, but did not affect water vapor permeability of films. EOs increased elongation and darkened the color of films. The results of the present study show that the 3 plant-derived EOs can be used to prepare tomato-based antimicrobial edible films with good physical properties for food applications by both direct contact and indirectly by vapors emanating from the films.     

Construction of a water-in-oil-in-water (W/O/W) double emulsion system based on oyster peptides and characterisation of freeze-dried products

In order to broaden the range of applications for oyster peptides in the food field, the amino acid composition of oyster peptide was analysed, after which the peptide sequence was identified using liquid-mass spectrometry technology. A W₁/O/W₂ double emulsion was prepared by the two-step shear emulsification method. The W₁/O/W₂ double emulsion was further freeze-dried after addition of alginate to obtain the final product, and the characteristics of the related product were analysed. The results show that oyster peptides are mainly composed of short peptides with molecular weights between 459.3 Da and 2716.3 Da. Polyglycerol polyrinoleate (PGPR) was selected as the emulsifier and added at 5% of the mass of the oil phase. The mass ratio of the oil phase to the water phase was O:W = 6:4, and optimal stability of the W₁/O emulsion was obtained by shearing and emulsifying for 2 min at 12 000 rpm. A superior W₁/O/W₂ double emulsion can be obtained by secondary emulsification in which the hydrophilic emulsifier Tween 80 was added at 0.8% (w/w) of the mass of the external water phase (W₂). The mass ratio of the emulsion to the external water phase was 5:5. The lyophilised product has good re-solubility, with the reconstituted emulsion maintaining the double-emulsion structure. Electronic nose results showed that the peculiar smell of the reconstituted emulsion was significantly lower than that of the oyster peptide solution. The results of this research provide a reference for the development and application of oyster peptides in the field of functional health foods.     

Enhancement of the oxidative stability of some vegetable oils by blending with Moringa oleifera oil

Blends (20%, 40%, 60%, 80% w/w) of Moringa oleifera oil (MOO) with sunflower oil (SFO) and soybean oil (SBO) were prepared to evaluate the changes in fatty acid (FA) composition, oxidative and thermal stability of SFO and SBO. The blending of MOO with SFO and SBO in proportions of 0–80% resulted in the reduction of linoleic acid (C_18:2) content of SFO and SBO from 67.0% to 17.2% and 56.2% to 14.6% and increase in the contents of oleic acid (C_18:1) from 26.2% to 68.3% and 21.4% to 65.9%, factors of 0.72, 0.72 and 1.27, 1.33, respectively. A storage ability test (180 days; ambient conditions) showed an appreciable improvement in the oxidative stability of substrate oils with increase of MOO concentration, as depicted by the least oxidative alterations in PV, IV and highest increase in induction period, IP, of the MOO:SBO (80: 20 w/w) blend. Each 20% addition of MOO resulted in decreases of PV and IV by factors of 0.84, 0.85 and 0.89, 0.88, respectively, and increases in IP by factors of 1.45 and 1.37 of SFO and SBO, respectively.     

Preparation Methods for Monodispersed Garlic Oil Microspheres in Water Using the Microemulsion Technique and Their Potential as Antimicrobials

Garlic oil is considered as a natural broad‐spectrum antibiotic because of its well‐known antimicrobial activity. However, the characteristics of easy volatility and poor aqueous solubility limit the application of garlic oil in industry. The purpose of the present work is to develop and evaluate an oil‐free microemulsion by loading garlic oil in microemulsion system. Microemulsions were prepared with ethoxylated hydrogenated castor (Cremophor RH40) as surfactant, n‐butanol (or ethanol) as cosurfactant, oleic acid‐containing garlic oil as oil phase, and ultrapure water as water phase. The effects of the ratio of surfactant to cosurfactant and different oil concentration on the area of oil‐in‐water (O/W) microemulsion region in pseudoternary phase diagrams were investigated. The particle size and garlic oil encapsulation efficiency of the formed microemulsions with different formulations were also investigated. In addition, the antimicrobial activity in vitro against Escherichia coli and Staphylococcus aureus was assessed. The experimental results show that a stable microemulsion region can be obtained when the mass ratio of surfactant to cosurfactant is, respectively, 1:1, 2:1, and 3:1. Especially, when the mixture surfactants of RH40/n‐butanol 2/1 (w/w) is used in the microemulsion formulation, the area of O/W microemulsion region is 0.089 with the particle size 13.29 to 13.85 nm and garlic oil encapsulation efficiency 99.5%. The prepared microemulsion solution exhibits remarkable antibacterial activity against S. aureus.     

Consumers' acceptance and quality stability of olive oil flavoured with essential oils of different oregano species

The objective of this study was to evaluate chemical and physical stability and consumers' acceptance of olive oil flavoured with oregano essential oils (EOs; Compacto, Cordobes, Criollo and Mendocino). Samples of olive oil were added with 0.05% EO and stored in dark (D) and light (L) conditions for 126 days. Samples with oregano EO had lower lipid oxidation indicator values [K232, K269, peroxide value (PV) and anisidine value], especially in darkness. Olive oil with Cordobes EO in D had the lowest PV (18.71 meqO₂ kg^?1). Using prediction equations, 20 meqO₂ kg^?1 PV in olive oil should be reached in 34 days in L control sample and in 126 days in the Cordobes EO sample in darkness. Samples with Cordobes and Criollo EOs in darkness had the highest chlorophyll content after 126 days (2.91 and 2.88 mg kg^?1, respectively). Sensory analysis showed that oregano EO addition in olive oil was detected by panellists in discriminative test and affected consumer acceptance.     

Synergistic effects of polyglycerol ester of polyricinoleic acid and sodium caseinate on the stabilisation of water–oil–water emulsions

The inherent thermodynamic instability of water–oil–water (W/O/W) emulsions has restrictions for their application in food systems. The objective of this study was to develop a food grade W/O/W emulsions with high yield and stability using minimal concentrations of surfactants. Emulsions were prepared using soybean oil, polyglycerol ester of polyricinoleic acid (PGPR) alone or in combination with sodium caseinate (NaCN) as emulsifier(s) for primary water-in-oil (W/O) emulsions and NaCN as the sole emulsifier for secondary W/O/W emulsions. Increasing the concentration of PGPR (0.5–8%w/v) had no effect on the droplet sizes of the resulting W/O/W emulsions. However, significant increases in droplet sizes of W/O/W emulsions were observed when the concentration of NaCN in external phase was reduced from 0.5 to 0.03% (w/v) (p<0.05). Percentage yields of emulsions (using a water-soluble dye) improved when PGPR concentration in the inner phase was increased from 0.5 to 8% (w/v). A stable W/O/W emulsion with a yield >90% could be prepared with 4% (w/v) PGPR alone as primary hydrophobic emulsifier and 0.5% (w/v) NaCN as external hydrophilic emulsifier. The concentration of PGPR in the inner phase could be reduced to 2% (w/v) without affecting the yield and stability of the W/O/W emulsion by partially replacing PGPR with 0.5% (w/v) NaCN, which was added to the aqueous phase of the primary W/O emulsion. The results indicate that a possible synergistic effect may exist between PGPR and NaCN, thus allowing formulation of double emulsions with reduced surfactant concentration.     

In vitro release of propranolol from oil/water microemuisions

Oil/water (o/w) microemulsions containing propranolol were studied. Isopropylmyristate was used as the oil, Tween 60 as a surfactant, butanol as a co-surfactant and a buffer of pH 6.5 for the continuous phase. The lipophilicity of propranolol was enhanced by formation of lipophilic ion-pairs to obtain a disperse phase that could act as a reservoir; octanoic acid was used as counter-ion. The diffusion rates of propranolol from microemulsions through a hydrophilic membrane decreased as the concentration of octanoic acid increased. The apparent permeability constant, determined at the beginning of the experiment, was 2.9 × 10⁻⁹ cm s⁻¹ for propranolol alone and diminished until 3.5 × 10⁻¹⁰ cm s⁻¹ in the presence of octanoic acid, at a concentration of 16.4 times that of propranolol.     

Encapsulation of functional lipophilic components in surfactant-based colloidal delivery systems: Vitamin E,vitamin D,and lemon oil

The fabrication and stability of surfactant-based colloidal delivery systems (microemulsions and emulsions) suitable for encapsulation of lipophilic active agents (vitamins and flavours) was investigated. An emulsion titration method was used to study the influence of surfactant type (Tween 20, 60 and 80) and oil type (Vitamin E, vitamin D₃ and lemon oil) on the incorporation of lipophilic components into surfactant micelles. Oil-in-water emulsions were formed and then different amounts were titrated into surfactant micelle solutions. The influence of surfactant-to-oil ratio (SOR) and oil type on the formation of colloidal dispersions was examined using dynamic light scattering and turbidity measurements. SOR, oil type, and surfactant type had a pronounced influence on the nature of the colloidal dispersions formed. Microemulsions could not be formed using vitamin D or E in 1% Tween solutions, due to the relatively large size of the lipophilic molecules relative to the hydrophobic interior of the surfactant micelles. On the other hand, microemulsions could be formed from lemon oil at relatively high SORs. There was not a major impact of non-ionic surfactant type (Tween 20, 60 or 80) on the formation and properties of the colloidal dispersions. However, Tween 20 micelles did appear to be able to solubilise less lemon oil than Tween 60 or 80 micelles, presumably due to their smaller dimensions. This study provides useful information for the rational design of food grade colloidal delivery systems for encapsulating flavour oils, oil-soluble vitamins, and other functional lipids for application in foods and beverages.     

Fabrication of chia (Salvia hispanica L.) seed oil nanoemulsions using different emulsifiers

In this study, the quality of spiral cold press chia seed oil was evaluated and four types of O/W chia seed oil nanoemlusion systems were prepared, including chia seed oil nanoemulsion stabilized with Tween 80 and Span 80 by spontaneous emulsification and microfluidization, sodium caseinate by microfluidization, and sucrose monopalmitate by microfluidization. All these optimized samples exhibited good storage stability for at least two weeks when stored at 4 °C or ambient temperature. The nanoemulsion stabilized with sodium caseinate was labeling friendly, and enough energy‐input facilitated the achievement of small particle size around 160 nm. The chia seed oil nanoemulsion fabricated with sucrose monopalmitate could get best transparency with smallest droplet diameter (around 47 nm). Chia seed oil nanoemulsion stabilized with Tween 80 and Span 80, as one model case diluted 500× into water system, had constant transparency after fortnight's storage.

Practical applications

Consumers are increasingly aware of nutrition as well as sensory properties of food products. Chia seed oil is a good source of n‐3 polyunsaturated fatty acids, yet difficult to be added directly into water‐based liquid food or beverages. The information given in this work might be useful for designing O/W chia seed oil nanoemulsion delivery system, facilitating the further application of chia seed oil in beverages and functional food industry which required only slightly turbid or even transparent appearance.