表面活性剂在纳米材料研究中的应用(续)

微乳液通常是由表面活性剂、助表面活性剂(通常为醇类)、油(通常为碳氢化合物)和水(或电解质水溶液)组成的透明的、各向同性的热力学稳定体系。表面活性剂可以形成O／W及W／O两种类型的微乳液，但是应用纳米材料制备的主要是W／O型反相微乳液，平时常不加区分地统称为微乳液。微乳液用于纳米材料制备研究较早，是研究最多的表面活性剂体系。     

丁香油微乳的制备及抑菌活性研究

为了改善丁香油水相溶解性及储藏稳定性差的应用缺陷,以可稀释微乳包载丁香油。通过比较丁香油微乳拟三元相图中微乳区面积(S_(ME))和最小可稀释比(DR),选择聚氧乙烯蓖麻油(Cremophor)EL 30与无水乙醇以21(质量比)为混合表面活性剂,水相环境为中性制备丁香油微乳。进一步采用电导率法和流变法对微乳构型进行鉴定,并选择O/W中心区域微乳:混合表面活性剂/丁香油/水(质量比)=16/4/80,Km=2,进行抑菌活性评价。结果表明,微乳包埋体系并未改变丁香油的抑菌活性。同时,通过检测丁香油微乳在稀释和储藏过程中的粒径变化,发现此微乳能保持良好的稀释和储藏稳定性。因此,该微乳在有效改善丁香油的水溶性和储藏稳定性的同时,对其抑菌活性没有影响。     

O/W型微乳液对β-胡萝卜素增溶作用

考察吐温80/乙醇/丁酸乙酯/水微乳液体系对水难溶性物β-胡萝卜素的增溶作用,同时用黏度计和动态光散射仪研究了空白微乳和含β-胡萝卜素微乳液的微结构。结果表明,β-胡萝卜素在以丁酸乙酯为油相的微乳液中溶解度明显增大;β-胡萝卜素加入明显影响微乳液的微结构。加入β-胡萝卜素使微乳液的W/O区域变小,BC和O/W区域变大;同样的,含β-胡萝卜素微乳液的粒径较空白微乳大,含β-胡萝卜素微乳液的粒径同空白微乳液一样,在储藏初期逐渐减小,3d后,基本不变,且在一个月内稳定。     

共轭亚油酸的微乳及其性质研究

制备了共轭亚油酸/EL-35和EL-10/乙醇/水体系的O/W型微乳液.考察了温度、防腐剂和pH对微乳液区域的影响;动态光散射测定了微乳液的粒径;利用粘度计测定不同水含量的微乳液的粘度变化来观察微乳液流变性:对O/W、W/O、B.C.中的共轭亚油酸的微乳液和共轭亚油酸乙醇溶液进行了光稳定性研究,还分析了温度和pH对微乳液和乙醇溶液中共轭亚油酸稳定性的影响.结果表明,温度升高,防腐剂苯甲酸钠浓度变大和pH降低使微乳区稍有减小;微乳液粒径在制备三个月后仍保持在80～90nm之间;共轭亚油酸对光热和酸都比较敏感,但同环境条件下,O/W型微乳液中的共轭亚油酸比较稳定.     

调和油微乳液的制备及稳定性研究

选择甲醇作为水相,油酸作为乳化剂制备调和油微乳液。甲醇具有沸点低、易汽化、能源洁净、助表面活性剂作用的特点,更有利于形成稳定的微乳化液。在甲醇质量分数为0.3以上时,所形成的微乳液为水包油型(O/W);0.3以下时形成的乳液为油包水型(W/O)。调和油-甲醇微乳化液最高储存温度是65℃。4℃冷藏后,部分样品出现分层,但恢复室温后仍为透明的微乳液。     

“正丁醇-水-茶油-皂素”微乳液体系的温度特性研究

通过绘制拟三元相图、测定电导率等手段,探讨“正丁醇-水-茶油-皂素”微乳液体系的温度特性。考察“正丁醇-水-茶油-皂素”体系外观形态、粒径大小及分布,确定该体系具备形成微乳液的能力,其微乳体系液滴的平均粒径为57.00 nm,多分散指数PDI为0.200。分析不同温度条件下体系形成能力、稳定性、电导率的变化,确定“正丁醇-水-茶油-皂素”属于温敏型体系,极端温度条件不利于W/O型微乳液的形成,优化得到最优的操作温度为70 ℃。     

新开发乳化技术——膜乳化法

<正>二种互不相溶液体以微小液滴分散于另一方的体系称之乳液.不仅水与油,各种液状有机物质均可成乳液.对食品乳液而言,主要是水与食用油脂类乳化;当油与水成乳液时,油可作分散相,分散于连续相水内成O/W型乳液,如牛奶便是天然O/W型乳液.反之,水也可作分散相,分散于连续相油内成环W/O型乳液,如人造奶油便是W/O型乳液典型例子.而且,O/W或W/O型乳液本身可作内层即分散相分散于连续相水或油中成O/W/O型或     

不同极性抗氧化剂对油包水乳液氧化稳定性的影响

以富含多不饱和脂肪酸(UPFA)的核桃油为油相,采用超高压微射流均质机制备油包水(W/O)乳液,分别添加非极性抗氧化剂α-生育酚及其极性对应物—6-羟基-2,5,7,8-四甲基色烷-2-羧酸(Trolox)于乳液中,45℃避光保存,检测乳液初级氧化产物—脂质氢过氧化物与次级氧化产物-顶空己醛含量,探究抗氧化剂极性对W/O乳液稳定性影响。结果表明,10~1000μM,α-生育酚与Trolox对W/O乳液脂质氢过氧化物和己醛的形成都具有抑制作用,其中Trolox抗氧化性随浓度的增大而提升,而较高浓度的α-生育酚(500~1000μM)反而降低其对脂质氢过氧化物的抑制作用;α-生育酚分布于乳液油水界面浓度小于极性抗氧化剂Trolox,导致非极性抗氧化剂α-生育酚活性低于极性抗氧化剂Trolox;乳液水相pH 3.0时,Trolox抗氧化性高于水相pH 7.0,水相pH通过影响Trolox在W/O乳液各相分布,从而影响其抗氧化性。     

薰衣草精油微乳体系的相行为、微观结构转变和清除自由基活性

薰衣草精油具有镇静安神、抗氧化等特性,但其疏水性限制了其在食品行业中的应用。本研究通过微乳化技术构建薰衣草精油微乳液运载体系,研究其相行为及微观结构转变对其清除自由基活性的影响。通过三元相图发现,二丙二醇作为助表面活性剂可以把微乳单相区面积扩大至71.4%;通过染色法、电导率的测定,确定微乳体系微观结构转变,水分质量分数分别为0%～30%、40%～50%、60%～90%时,体系相应处于W/O、双连续和O/W的结构类型,且在双连续阶段体系黏度达到峰值。同时,微乳液对1,1-二苯基-2-三硝基苯肼自由基清除率随着水分体积分数增加而提高;2,2’-联氮-双-3-乙基苯并噻唑啉-6-磺酸阳离子自由基清除率在W/O和双连续型阶段先下降,转变为O/W型时回升,并在水分体积分数70%时达到最大值。该多元微乳体系有效实现了薰衣草精油的增溶,且其物理特征和抗氧化性的变化与微观结构密切相关。     

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。     

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.     

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.     

Formation and characterisation of mint oil/S and CS/water microemulsions

Preparation and characterisation of microemulsions (ME) with mint oil (MO) as the oil phase were conducted to find a system which could provide a controlled, sustained, and prolonged delivery of MO. The influence of surfactant type and processing parameters on the formation of MO-ME’s was studied by comparing the areas of the monophase ME regions in pseudoternary phase diagrams. A 1:1 mixture of the surfactants, AOT and CrEL, was found to be the most effective, and it produced a ME monophase area of about 70%. The monophase regions were analysed by conductivity measurements; the results suggested that O/W regions within the ME phases were formed when the water content was higher than 60–65%. As tested with dynamic light scattering (DLS) and head space (HS) GC analysis, the particle size of O/W ME, with 60% water and AOT/CrEL = 1:1 as surfactants, was 20.0 nm and the encapsulation efficiency was 78.4%. The results indicated that a ME of MO/AOT and CrEL/ethanol/water, may be a promising dispersion for the protection of MO in food products.     

负载葡萄皮粉花色苷提取物的W/O/W型复乳制备及其体外消化评价

以葡萄皮花色苷(ACNs)提取物为内水相(W1),玉米油为油相,乳清蛋白(WPI)溶液为外水相(W2)制备水包油包水(W/O/W)型复乳.复乳的包埋率高达(93.19±2.78)％,平均粒径为(287.90±3.12)nm.经口腔消化后,乳液未发现有明显变化;模拟胃部消化后,乳液液滴相互融合形成具有双层结构的较大微粒,...     

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.     

溶血磷脂制备含胆固醇微乳液的研究

溶血磷脂HLB较大，易形成O／W型乳化剂，可制备热力学稳定的微乳化体系。利用溶血磷脂作乳化剂，制备含胆固醇的微乳液，是以胆固醇为油相，溶血磷脂为乳化剂，正丙醇为共表面活性剂，制成微乳液。最终产物呈透明或半透明的均相混合物。     

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.