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.     

Incorporation of soybean oil improves the dilutability of essential oil microemulsions

Plant essential oils (EOs) have strong antimicrobial and antioxidant activities. However, their water insolubility and volatility limit their practical application. Microemulsions are thermodynamically stable delivery systems for hydrophobic bioactive compounds but can be destabilized after dilution by the polar phase. In the present study, soybean oil (SBO) was studied for the impacts on formation and dilutability of EO microemulsions comprised of polysorbate 80 (Tween™ 80) as a surfactant and equal mass of water and propylene glycol as the polar phase. The oil phase contained EO (cinnamon bark oil, eugenol, or thymol) and SBO at 1:0, 2:1 or 4:1 mass ratios. Pseudo-ternary phase diagrams were constructed after titrating the polar phase into Tween™ 80–oil mixture at 1:1 to 9:1 mass ratios. Blending SBO with EO expanded the regimes of microemulsions and reduced the droplet dimensions that were stable over 90 days. Viscosity and electrical conductivity data indicated the transition from W/O to O/W microemulsions as the content of polar phase increased from 10% to 90% w/w. The enhanced dilutability of microemulsions after blending with SBO can broaden the application of EOs.     

Formulation of food-grade microemulsions with glycerol monolaurate: effects of short-chain alcohols,polyols, salts and nonionic surfactants

The formulation of food-grade microemulsions with glycerol monolaurate (GML) for antimicrobial applications has been studied. The compositions included water, GML, short-chain alcohols (such as ethanol), polyols (propylene glycol and glycerol), salts (organic, such as sodium benzoate, sodium lactate and sodium propionate, and inorganic, such as NaCl) and several nonionic surfactants [such as ethoxylated sorbitan esters, sucrose esters (SEs)]. The phase behavior of these systems is discussed with respect to the influence of composition on the degree of oil solubilization in the aqueous phase. The oil solubilization was dramatically improved in the presence of the short-chain alcohols and polyols, organic salts contributed to the improvement of oil solubilization as hydrotropes. Tween 20 being the most hydrophilic surfactant in Tweens solubilized the maximum oil, but in the presence of SEs it is hard to form oil-in-water microemulsions. Viscosity measurements along selected dilution lines indicate that at a certain composition the system inverts from a water-in-oil to an oil-in-water microemulsion.     

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。     

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.     

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.     

A novel water-repellent o/w emulsion using a new water-soluble amphiphilic polymer

A novel O/W (oil-in-water) emulsion cosmetic that has strong water repellency and a >>water-splash feel« was prepared using the amphiphilic polymer hydrophilic-hydrophobic modified polysaccharide (INCI/Sodium Stearoxy PG-Hydroxyethylcellulose Sulfonate). This emulsion is composed of a hydrophobic–hydrophilic modified polysaccharide/water/oil system with a small amount of lipophilic non-ionic surfactant (hydrophilic–lipophilic balance<5) added to obtain finely emulsified oil particles. Hydrophilic–hydrophobic modified polysaccharide was used as a thickener and polymer surfactant, and it produced a stable O/W emulsion without the addition of a hydrophilic surfactant. Several types of oil droplets decrease in size upon addition of various kinds of lipophilic surfactant due to the lowering of tension at the water/oil interface. Rheological measurements revealed that the strong network structure of hydrophilic–hydrophobic modified polysaccharide retained oil droplets without occurrence of phase inversion. Such an emulsion is very different from those made using conventional hydrophilic surfactants, and it is water repellent. This system was characterized by the presence of hydrophilic–hydrophobic modified polysaccharide, and the state of the emulsion could be controlled by the ratio of hydrophobic/hydrophilic moieties introduced into the polysaccharide.     

橄榄油微乳体系的相行为及影响因素研究

本文以大豆卵磷脂和司盘80(Span80)复配为表面活性剂,乙醇为助表面活性剂,构建橄榄油微乳体系。采用拟三元相图法,考察亲水亲油平衡值(HLB值)、表面活性剂与助表面活性剂的比值(Km值)、盐浓度等因素对微乳体系相行为的影响,并通过电导率、负染透射电镜等方法研究微乳体系的结构,以优化体系配方、考察微乳液的形成规律。结果表明:大豆卵磷脂与Span80以质量比为3:1复配为混合表面活性剂,并与助表面活性剂无水乙醇按质量比(Km值)为2:1混合,所形成的大豆卵磷脂/Span80/乙醇/橄榄油/水微乳区域面积最大;甘油或少量盐离子的加入,可以在一定程度上增大微乳单相区的面积,但当盐浓度(C_NaCl)大于4 mol/L时,微乳区域面积明显减小;在大豆卵磷脂/Span80/橄榄油/乙醇/甘油/水微乳体系中,当水相(w_水/w_甘油=1:1)含量大于22 wt%时,体系逐渐由W/O型转变为双连续型结构。当水相含量超过30 wt%,体系则发生相分离。此研究为橄榄油微乳液的制备及应用提供理论和技术支持。     

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。     

Surfactin作为表面活性剂对O/W型藻油DHA乳状液物理和氧化稳定性的影响

以Surfactin作为表面活性剂制备藻油二十二碳六烯酸(docosahexaenoic acid,DHA)乳状液并研究其稳定性。研究发现,水相为质量分数0.8%的Surfactin溶液,在不添加助表面活性剂和其他添加剂的条件下,制备水包油型藻油DHA乳状液,在4℃和37℃条件下保存相比其他表面活性剂具有良好的物理稳定性,在浊度、粒径、Zeta电位和流变学角度与Tween-80-丙三醇等表面活性剂制备的藻油DHA乳状液相比均有显著差异(P0.05),Surfactin藻油DHA乳状液在各方面均优于其他表面活性剂的藻油DHA乳状液。在高温处理和常温贮存过程中,Surfactin藻油DHA乳状液的氧化稳定性也十分优良,在37℃贮存60 d乳状液过氧化值始终处于较低水平,仅为(1.635±0.202)meq/kg。     

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.     

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.     

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.     

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     

Antimicrobial activity of a food-grade fully dilutable microemulsion against Escherichia coli and Staphylococcus aureus

Microemulsions are colloidal nanodispersions of oil and water stabilized by an interfacial film of surfactant molecules, typically in conjunction with a cosurfactant. There is a limited number of reports in the literature on microemulsion use for antimicrobial purposes. The physicochemical characterization of a food-grade fully dilutable microemulsion system with glycerol monolaurate (GML) as oil, organic acids as cosurfactant, Tween 80 as surfactant, and the antimicrobial activities against Escherichia coli and Staphylococcus aureus have been studied in this paper. The influence of organic acids on oil solubilization was clearly reflected in the phase behavior of these systems. Propionic acid demonstrated the greatest capability to improve the oil solubilization among the tested linear and nonlinear chain organic acids and contributed to the formation of U-type microemulsion systems. One microemulsion formulation with an average particle size of 8 nm was selected, the composition is GML/propionic acid/Tween 80/water = 3:9:8:12. The kinetics of killing experiments demonstrated that the undiluted microemulsion caused a complete loss of viability of E. coli or S. aureus cells in 1 min and still had effective bactericidal effects even when diluted, more than 99% viable E. coli cells were killed within 15 min and a complete loss of viability was achieved at 45 min while more than 99% viable S. aureus cells were killed within 30 min and a complete loss of viability was achieved at 60 min in the presence of the 10-fold diluted microemulsion. The fast killing kinetics of the ten-fold serial dilutions of microemulsions were in good agreement with the mode of action studies, indicating that the interaction between the antimicrobial microemulsions and bacterial membranes significantly decreased the bacterial cell surface hydrophobicity and induced the quick release of 260 nm absorbing materials. This work suggests the potential use of food-grade fully dilutable microemulsions for antimicrobial purposes in beverages or seafood products.     

棕榈仁油/甘油/吐温/水体系中的微乳化作用研究

分别以吐温-20、吐温-40、吐温-60、吐温-80和吐温-85为表面活性剂,甘油为助表面活性剂,在相同的条件下,制作了棕榈仁油/甘油/吐温/水四组分体系的拟三元相图.讨论了助表面活性剂(醇)与表面活性剂的质量比(Km)及不同表面活性剂对混合体系微乳化作用的影响.结果表明,所研究的各体系中,以吐温-60所形成的微乳状液区最大.     

吐温80/正构醇微乳体系形成过程的介观模拟

利用耗散粒子动力学(DPD)方法对吐温80/正构醇(C2~C8)/丁酸乙酯/水四组分微乳体系形成过程进行了模拟,研究了醇类浓度及烃链长度对微乳形成过程相行为及微观结构的影响。研究发现:正构醇浓度和烷烃链长度对体系自组装形态变化有显著影响,当醇类浓度较低时,微乳粒径随醇浓度的增大而增大,当浓度增加到一定程度后,继续增加醇浓度则导致微乳形态从球状依次变为管道状、网格状;通过比较不同烷烃链长的微乳体系发生形态变化时醇的浓度大小,发现醇烷烃链长的增加促使微乳体系在醇浓度较低时就发生形态转变,且体系界面张力较快趋于稳定。同时,研究发现醇链长的增加会使吐温80/正构醇/丁酸乙酯/水体系的W/O型和双连续型微乳区增大。该结果为微乳类型及形态尺寸的调控从而实现蛋白质的选择性萃取提供指导。     

Microemulsions: a potential delivery system for bioactives in food

Microemulsions are thermodynamically stable, transparent, low viscosity, and isotropic dispersions consisting of oil and water stabilized by an interfacial film of surfactant molecules, typically in conjunction with a cosurfactant. Microemulsions (so-called due to their small particle size; 5-100 nm) have found application in a wide variety of systems, such as pharmaceutical and oil recovery, but their application in food systems has been hindered by the types of surfactant permissible for use in food. The objective of this review is to provide an overview of the structures and phase behavior of microemulsions, methods of microemulsion formation, and techniques which may be used for characterization. A comprehensive review of previous work on both food-grade microemulsion systems, and non-food-grade systems of specific food interest is included. The application of microemulsions as reaction media, their ability to solubilize proteins and hence their use as a separation technique is also documented. In addition, attention is focused on the application of microemulsions as delivery systems for delivery of bioactive compounds, and the links between microemulsions and increased bioavailability. Future research, both applied and fundamental, should focus on surfactants which are not restricted for use in foods.     

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.     

Influence of surfactant hydrophobicity on the detachment of Escherichia coli O157:H7 from lettuce

The influence of surfactant hydrophobicity on detachment of Escherichia coli O157:H7 from lettuce was determined. Lettuce pieces inoculated with the pathogen were rinsed with Tween and Span surfactants of different hydrophobicity. Of the Tweens, only Tween 85, the Tween with the lowest hydrophile/lipophile balance (HLB), significantly detached the pathogen from lettuce surface. Span 85 (the surfactant with the lowest HLB studied) exhibited the greatest ability among surfactants tested to detach cells from lettuce. This surfactant removed cells attached to the leaf cuticle but not to the cut edge, and caused no detectable reduction in viability of cells remaining on the lettuce. Treatment with Span 85 did not detach cells when they were allowed to attach in the presence of calcium ions. The combination of NaCl/NaHCO3 (pH 10) and Span 85 did not detach cells possibly due to reduced hydrophobicity of the Span at this pH. This study suggests that surfactants of low HLB disrupt hydrophobic interactions between E. coli O157:H7 and the lettuce surface but cannot cause release of cells adhering to hydrophilic structures such as cut or damaged tissue.