Process optimization and stability of d-limonene nanoemulsions prepared by catastrophic phase inversion method

The aim of this study was to optimize the process and stability of d-limonene nanoemulsions. The nanoemulsions were prepared by catastrophic phase inversion method using Tween 80 as surfactant. According to the results, the SOR value would considerably affect the turbidity and the mean particle diameter of emulsions. At a high concentration of surfactant (S/O = 1.5), d-limonene nanoemulsions could be obtained. In addition, the formation of nanoemulsions may be primarily related to the viscosity of oil phase. When the oil phase contained less than 15% (w/w) olive oil, the nanoemulsions could be prepared. The turbidities and the mean particle diameters of d-limonene nanoemulsions with adding the same concentration of different plant oils were similar. Furthermore, it can be found that adding olive oil could enhance the stability of d-limonene nanoemulsion system and decrease Ostwald ripening rate, and the Ostwald ripening rate of d-limonene nanoemulsion at 4 °C was higher than that at 28 °C.     

两种凝聚法橙油纳米胶囊的性质比较

探讨复凝聚法(complex coacervation,CC)和单凝聚法(simple coacervation,SC)制备的纳米胶囊(nanocapsule,Nano)的差异,本文以橙油为芯材,采用CC和SC两种凝聚法分别以明胶、海藻酸钠和壳聚糖为壁材对其包埋制备纳米胶囊,并通过包埋率、粒径分布、缓释性能、红外特征、热重稳定性(TGA)及乳液稳定性等对两种纳米胶囊进行了表征和比较。结果表明,两种橙油纳米胶囊的平均粒径均服从正态分布,大小比较均匀。SC-Nano粒径分布窄,平均粒径更小(76.51±8.04)nm,CC-Nano包埋率(82.97±1.49)%和得率(82.31±0.67)%更高。场发射电镜(FESEM)显示纳米胶囊形貌独立且均匀,表面光滑。FT-IR结果证实橙油成功被包埋。缓释性能、TGA和乳化性能分析表明两种纳米胶囊均具有良好的缓释性、热稳定性和乳化稳定性,且SC-Nano耐热性和乳化活性更强。因此,两种凝聚法制备的橙油纳米胶囊可依据其特性应用在不同食品。     

载体油对槲皮素纳米乳液理化稳定性和生物利用度的影响

研究载体油种类和体积分数对纳米乳液稳定性和槲皮素生物利用度的影响。以中链甘油三酯（medium-chain triglyceride,MCT）和长链甘油三酯（long-chain triglyceride,LCT）为油相,梨小豆蛋白为乳化剂制备槲皮素负载型纳米乳液。通过光散射粒径分析、Zeta电位、物理稳定性、游离脂肪酸释放率和槲皮素生物利用度探究乳液稳定性。结果表明,与LCT-纳米乳液相比,由MCT制得的槲皮素纳米乳液表现出更高的稳定性和更慢的槲皮素降解速率,油体积分数为5%时,MCT-纳米乳液粒径（（152.80±1.73）nm）小于LCT-纳米乳液（（180.42±1.98）nm）。通过模拟胃肠道模型测得槲皮素的生物保留率在MCT-纳米乳液体系中得到了极大改善。该信息可以促进设计更有效的槲皮素强化的递送系统。     

超高压均质制备大豆多肽纳米乳及其粒径和稳定性分析

大豆多肽是具有营养、呈味、抗氧化等生物活性的新型多功能天然乳化剂,为开发大豆多肽在食品乳液中的应用,本研究探索了超高压均质技术制备大豆多肽纳米乳液的影响因素和加工效果。以大豆分离蛋白为原料酶法制备大豆多肽（Soybean protein isolate hydrolysates,SPIH）,考察了多肽质量浓度、均质压力和循环次数对纳米乳平均粒径、粒度分布和物理稳定性的影响,在单因素实验基础上,以粒径和稳定性为指标,通过正交试验进行工艺优化,并应用粒度仪和原子力显微镜表征了其储存稳定性和和微观形貌。结果表明,各因素最佳水平为:20 mg/mL多肽质量浓度,140 MPa均质压力和5次循环,在此条件下制备得到粒径为178.8 nm,稳定性指数Ke=7.37%的纳米乳液。超高压均质法制备的大豆多肽纳米乳具有均匀的液滴分布并可稳定储存56 d以上,随多肽质量浓度增加纳米乳液滴聚集情况明显。研究为多肽乳化剂纳米乳液的制备和应用提供了参考。     

Effect of salt ions on an ultrasonically modified soybean lipophilic protein nanoemulsion

Soybean lipophilic proteins (LP) are promising emulsifiers for nanoemulsion delivery systems. We analysed the effect of common salt ions on the stability of nanoemulsion delivery systems that contained ultrasonically modified soybean LP. Moreover, explored the mechanism of influence. The LP nanoemulsions presented large absolute zeta (ζ) potentials at low salt ion concentrations, and their particle size distribution was relatively uniform. The emulsification, encapsulation efficiency and oxidation stability were superior to those of other nanoemulsions. The ultrasonically modified samples presented higher absolute ζ potentials and smaller droplet sizes than the pristine ones and formed uniform protein films at different salt ion concentrations. Therefore, ultrasonication improved the emulsification, encapsulation efficiency and oxidation stability of the emulsions, effectively improve the stability of nano-delivery systems in different salt ion environments and maximise delivery efficiency at low salt ion concentrations. These results are helpful for the development of LP nanoemulsion systems that are stable at different salt ion concentrations.     

均质工艺对制备鱼油微胶囊结构和理化性质的影响

本实验分别利用高压均质、空化射流和超声破碎3 种均质方式制备以大豆分离蛋白和磷脂酰胆碱包裹的鱼油纳米乳液和微胶囊,并对纳米乳液粒径、Zeta-电位、稳定性、黏度、乳化产率及微胶囊形貌、理化性质、稳定性进行比较分析,研究均质工艺对鱼油纳米乳液和微胶囊理化性质的影响。结果发现,空化射流工艺制备的纳米乳液平均粒径小,乳化产率和乳液稳定性较高,经过空化射流10 min制备的微胶囊包埋率达87.44%,溶解度较高,微胶囊颗粒表面形态饱满、致密、无裂纹和空隙,氧化稳定性和热稳定性较好。高压均质和超声破碎制得的纳米乳液平均粒径大,乳化产率和乳液稳定性较低,经过100 MPa高压均质和400 W超声破碎制得的微胶囊包埋率分别为80.36%和78.64%,溶解度相较于空化射流差,微胶囊颗粒表面分别出现微孔和较大的孔洞,氧化稳定性和热稳定性较差。傅里叶变换红外光谱分析结果表明3 种均质工艺均有较好的包埋效果。通过实验可以得出空化射流均质工艺制备的鱼油纳米乳液及微胶囊在产品性能上要优于其他两种均质工艺。本研究可为鱼油纳米乳液和微胶囊产品的均质工艺选择以及应用评价体系的构建提供理论依据。     

基于响应面法构建虾青素纳米乳液

为提高虾青素的稳定性,以生物大分子卵磷脂为乳化剂,采用高压均质法制备负载虾青素的纳米乳液,在单因素实验的基础上,以纳米乳液粒径和虾青素负载率为响应值,以乳化剂浓度、油水比、虾青素添加量3个因素为响应因子,利用响应面法建立二次回归方程模型,获得制备虾青素纳米乳液的最佳工艺条件为:乳化剂浓度1%(w/w),乳化温度55 ℃,乳化时间45 min,油水比1:8.5,虾青素添加质量分数为0.5%(w/w),按此工艺条件制备得到虾青素纳米乳液的粒径为238.84 nm,虾青素负载率可达到90.41%。     

Identification of an emulsifier and conditions for preparing stable nanoemulsions containing the antioxidant astaxanthin

In this study, oil-in-water nanoemulsions of astaxanthin were prepared by high-pressure homogenization. The influence of emulsifying conditions including emulsifier type, concentration, passing time, astaxanthin concentration and coantioxidants were optimized. The stabilities of nanoemulsions were measured using zetasizer, FF-SEM, TEM, colorimeter and particle size analyzer. The mean diameter of the dispersed particles containing astaxanthin ranged from 160 to 190 nm. The size distribution was unimodal and extended from 100 to 200 nm. The nanoemulsions prepared with glyceryl citrate/lactate/linoleate/oleate (glyceryl ester) had smaller particle size and narrower size distribution than the emulsion prepared with hydrogenated lecithin. Stable incorporation of astaxanthin in nanoemulsion was performed and checked using HPLC, FF-SEM and TEM. The nanoemulsion was not significantly affected during storage under light and thermal condition for one month indicating that the nanoemulsion had a zeta potential of less than -41 mV, indicating a stable colloid.     

基于凹凸棒稳定的姜精油纳米乳的性质表征和结肠靶向研究

为提高姜精油（Ginger essential oil, GEO）的稳定性和利用度,本实验室以酸改性凹凸棒为稳定剂、亚麻籽胶作为乳化剂、壳聚糖盐酸盐做壁材制备了姜精油纳米乳。本研究对姜精油纳米乳进行性质表征（包括形貌与形态、粒径分布、流变性、红外光谱、包埋率）并评价其结肠靶向和缓释性能。研究结果表明姜精油纳米乳粒径呈正态分布,液滴平均粒径为329.6 nm,PDI为0.259,包埋率为91.26%±0.03%;通过荧光显微镜和扫描电镜观察,表明所制备姜精油纳米乳分散度良好,呈表面光滑的球形;红外光谱结果表明,姜精油被包封进纳米乳中且化学组成未被破坏,纳米乳中各组分的结合方式为物理结合;姜精油纳米乳在4、25、40℃贮藏28 d稳定性良好;通过体外模拟消化试验及动力学分析结果表明,姜精油纳米乳具有结肠靶向和缓释的性能。本研究为食品功能因子结肠递送体系的建立、以及后期姜精油纳米乳作为食品功能因子改善肠道健康中的应用提供了理论依据。     

油相结构化对大豆蛋白藻油纳米乳液氧化稳定性的影响

利用蜂蜡结构化藻油结合大豆分离蛋白-甜菊糖（soy protein isolate-stevioside,SPI-STE）复合体系的乳化特性,制备高稳态的藻油纳米乳液体系。藻油凝胶的微观结构观察、热性质测试以及流变学分析表明,当藻油中蜂蜡添加量达到4%(m/m)时,大量晶体组装成稳固的网络结构,从而构筑出稳定的油凝胶。进一步以SPI-STE为稳定剂制备藻油纳米乳液,研究了藻油结构化对纳米乳液形成及稳定性的影响。结果表明,油相中添加蜂蜡对纳米乳液的形成没有显著影响。随着藻油中蜂蜡质量分数的增大（0%～6%）,乳液的物理稳定性逐渐提高;但在高蜂蜡添加量（8%）下,刚性较强的凝胶网络破坏了油滴界面层,乳液稳定性变差。热促氧化及光促氧化结果显示,蜂蜡油相结构化明显提高了纳米乳液的氧化稳定性,其中油相中含有6%蜂蜡的样品延缓氧化的效果最明显。本研究可为食品工业构建高稳态的藻油纳米乳液载体及产品提供一定技术支持。     

DHA藻油纳米乳液制备及稳定性的研究

为提高DHA藻油在食品应用中的稳定性,本研究制备了一种新型的藻油双层纳米乳液.基于层层自组装原理,选用乳清分离蛋白(WPI)和阿拉伯胶(GA)分别作为纳米乳液的内层和外层包材,通过高压均质制备了 DHA藻油双层纳米乳液.对制备纳米乳液工艺参数进行考察,并探究其理化稳定性.结果表明:WPI质量分数为1.5％,GA质量分数...     

紫苏籽油双层乳状液的制备及其物理化学稳定性评价

采用紫苏籽油为芯材,大豆多糖和壳聚糖为壁材,分别制备紫苏籽油单层与双层乳状液,并且对乳状液的粒径、Zeta电位、物理稳定性以及化学稳定性进行评价。结果显示,单层乳状液粒径随着芯壁比（质量比）的升高而增大,物理稳定性变差,最适的芯壁比（质量比）为2∶1;随着壳聚糖质量分数的增加,双层乳状液的Zeta电位逐渐增大,并且由负值变为正值,壳聚糖质量分数为0.2%时电位绝对值最小为3.6 mV,当壳聚糖质量分数为0.4%时电位为43 mV,电位增加速率变小;随着壳聚糖质量分数的增加,乳状液粒径呈先减小、再增大、再减小的变化,壳聚糖质量分数为0.2%时达到最大粒径为5.21 μm,0.4%时达到最小粒径为1.185 μm;随着壳聚糖质量分数的增加乳状液物理稳定逐渐增强。壳聚糖质量分数对乳状液化学稳定性影响显著（p＜0.05）,抗氧化效果依次为0.4%＞0.6%＞0.2%。     

Optimization of β-casein stabilized nanoemulsions using experimental mixture design

The objective of this study was to determine the effect of changing viscosity and glass transition temperature in the continuous phase of nanoemulsion systems on subsequent stability. Formulations comprising of β-casein (2.5%, 5%, 7.5%, and 10% w/w), lactose (0% to 20% w/w), and trehalose (0% to 20% w/w) were generated from Design of Experiments (DOE) software and tested for glass transition temperature and onset of ice-melting temperature in maximally freeze-concentrated state (T(g) ' & T(m) '), and viscosity (μ). Increasing β-casein content resulted in significant (P < 0.0001) increases in viscosity and T(m) ' (P= 0.0003), and significant (P < 0.0001) decreases in T(g) '. A mixture design was used to predict the optimum levels of lactose and trehalose required to attain the minimum and maximum T(g) ' and viscosity in solution at fixed protein contents. These mixtures were used to form the continuous phase of β-casein stabilized nanoemulsions (10% w/w sunflower oil) prepared by microfluidization at 70 MPa. Nanoemulsions were analyzed for T(g) ' & T(m) ', as well as viscosity, mean particle size, and stability. Increasing levels of β-casein (2.5% to 10% w/w) resulted in a significant (P < 0.0001) increase in viscosity (5 to 156 mPa.s), significant increase in particle size (P= 0.0115) from 186 to 199 nm, and significant decrease (P= 0.0001) in T(g) ' (-45 to -50 °C). Increasing the protein content resulted in a significant (P < 0.0001) increase in nanoemulsion stability. A mixture DOE was successfully used to predict glass transition and rheological properties for development of a continuous phase for use in nanoemulsions.     

Influence of non-ionic surfactant on electrostatic complexation of protein-coated oil droplets and ionic biopolymers (alginate and chitosan)

The purpose of this study was to examine the influence of a non-ionic cosurfactant (Tween 20) on the formation and properties of electrostatic complexes consisting of charged oil droplets and charged biopolymers. The mean droplet diameters in oil-in-water emulsions prepared using a membrane homogenizer were considerably larger when β-lactoglobulin (BLG) was used alone (≈8 μm), than when it was used in combination with Tween 20 (≈2 μm). The cationic oil droplets formed by membrane homogenization (4.0 μm pore size) were mixed with either alginate (anionic) solution (1% oil: 0–0.5% alginate: pH 3.5) or with alginate (anionic) and then chitosan (cationic) solutions (0.4% oil: 0.1% alginate; 0–0.2% chitosan: pH 4.5). The electrical characteristics, microstructure, and physical stability of the electrostatic complexes formed were determined. Under certain conditions multilayer emulsions consisting of oil droplets coated by alginate or alginate/chitosan layers were formed, whereas under other conditions microclusters consisting of aggregated oil droplets embedded within alginate or alginate/chitosan complexes were formed. The presence of the cosurfactant had a major impact on the electrical charge and dimensions of the electrostatic complexes formed. This study shows that various kinds of electrostatic complexes can be formed from charged oil droplets and charged biopolymers, and that their functional characteristics can be controlled using non-ionic cosurfactants.     

载姜黄素纳米乳液的制备及体外模拟消化特性研究

为提高姜黄素的水溶性和生物可利用度，本研究以选择性水解大豆蛋白为乳化剂，构建了稳定的姜黄素纳米乳液运载体系，对纳米乳液的制备过程中均质压力的影响进行研究，并对纳米乳液的粒径、Zeta-电位、浊度、微观结构以及胃肠消化特性进行表征。结果表明，姜黄素的溶解度与油相有显著关系（P<0.05），溶解度从大到小分别为中链甘油三酯（MCT）>菜籽油>玉米油>橄榄油>大豆油。以50 MPa为均质压力，制备得到的乳液平均粒径最小（265.00±4.14 nm）、Zeta-电位绝对值较大（-30.77±0.71 mV）、浊度最低。分别以菜籽油和MCT为油相制备得到载姜黄素纳米乳能抵抗胃蛋白酶的消化，在胃部保持一定的界面张力使乳液维持原有形态，而在小肠中消化，游离脂肪酸释放率达60%。将菜籽油和MCT以不同比例进行复配，发现随着菜籽油比例的增加，姜黄素的生物可利用度和保留率显著降低，其中，以菜籽油:MCT=3:7为油相的乳液具备与以纯MCT为油相的乳液几乎相同的姜黄素生物可利用度和保留率，接近70%。研究结果对封装和释放高亲脂性功能成分的传递系统的设计具有重要指导意义。     

Challenges associated in stability of food grade nanoemulsions

Food grade nanoemulsions are being increasingly used in the food sector for their physico-chemical properties towards efficient encapsulation, entrapment of bioactive compounds, solubilization, targeted delivery, and bioavailability. Nanoemulsions are considered as one of the important vehicles for the sustained release of food bioactive compounds due to their smaller size (nm), increased surface area, and unique morphological characteristics. Nanoemulsification is an ideal technique for fabricating the bioactive compounds in a nano form. Formation and stabilization of nanoemulsion depends on the physi-cochemical characteristics of its constituents including oil phase, aqueous phase, and emulsifiers. This review is mainly focused on the instability mechanisms of nanoemulsion such as flocculation, Ostwald ripening, creaming, phase separation, coalescence, and sedimentation. Further, the major factors associated with these instability mechanisms like ionic strength, temperature, solubilization, particle size distribution, particle charge, pH strength, acid stability, and heat treatment are also discussed. Finally, safety issues of food grade nanoemulsions are highlighted.     

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.     

甜橙精油纳米乳液的制备及其抑菌作用研究

采用相转变点法制备甜橙精油纳米乳液和D-柠檬烯纳米乳液,采用抑菌圈法和最低抑菌浓度法研究甜橙精油纳米乳液及其主要成分D-柠檬烯纳米乳液对大肠杆菌(Escherichia coli)、枯草芽孢杆菌(Bacillus subtilis)、金黄色葡萄球菌(Staphylococcus aureus)和桔霉菌(Penicillium citrinum)的抑菌作用。结果表明,甜橙精油纳米乳液和D-柠檬烯纳米乳液均有较好的抑菌效果,且同等浓度的D-柠檬烯纳米乳抑菌效果比甜橙精油的抑菌效果好,14%甜橙精油纳米乳液对大肠杆菌、枯草芽孢杆菌、金黄色葡萄球菌和桔青霉的抑菌圈直径直径分别为11.7、14.0、9.7和9.0 mm,而D-柠檬烯纳米乳液对大肠杆菌、枯草芽孢杆菌、金黄色葡萄球菌和桔青霉的抑菌圈直径直径分别为19.0、23.7、13.0和12.0 mm。甜橙精油纳米乳液对枯草芽孢杆菌的抑菌作用最强,其最低抑菌浓度(MIC)约为7.7%,对金黄色葡萄球菌和桔青霉的抑菌作用较弱,其对这两种微生物的MIC均约为11%,对大肠杆菌的MIC介于7.7%~11%之间。甜橙精油和D-柠檬烯制成纳米乳液后均具有良好的抑菌作用,为纳米乳液在食品中的抑菌应用提供了理论依据。     

纳米乳液改善多酚性能及在食品中的应用进展

国内外研究人员一直关注植物多酚促进人体健康的潜在作用,发现在实际应用中,多酚的稳定性差、溶解性差、生物利用率低等问题亟待解决。纳米乳液递送体系粒径小、稳定性佳,是极佳的多酚递送体系,应用前景广阔。经纳米乳液包埋后的多酚可改善稳定性,提高在体内的生物利用率,表现出更佳的生物可及性、抗氧化性及抗肿瘤活性,更适合应用于食品工业。该研究结合国内外研究者的成果综述了多酚的分类及作用;多酚纳米乳液制备新技术;纳米乳包载对多酚多种性能的改善效果与作用机制。基于多酚纳米乳液需解决的首要问题提出了乳液优化方案,并阐述了多酚纳米乳液在食品工业中的现状及潜在应用,对多酚纳米乳液未来的制备方向进行展望。     

紫苏油多层乳液的制备及乳液油脂体外消化特性

针对紫苏油在贮藏过程中极易氧化的特点,以大豆分离蛋白、壳聚糖和海藻酸钠为乳化剂,采用静电层层自组装技术对紫苏油进行包封,使紫苏油保持良好的物理稳定性,并能达到油脂缓释的目的。分别对紫苏油单层乳液、双层乳液和三层乳液微观形态和稳定性进行考察,建立体外模拟消化模型,通过气相色谱测定3 种乳液消化前后的脂肪酸组成。结果表明：壁材质量分数为大豆分离蛋白1.0%、壳聚糖2.0%、海藻酸钠1.5%时制备的3 种乳液粒径较小、电位较高,具有良好的理化稳定性。在酸性条件下的多层乳液能够更好保护多不饱和脂肪酸,随着包埋层数的增加,紫苏油的氧化速率越慢。体外模拟消化结果表明三层乳液较单层和双层乳液具有更好的缓释效果,多层乳液可以保证油脂中脂肪酸有效释放。本实验阐明不同界面层对紫苏油消化和脂肪酸释放特性的影响,为指导油脂缓释体系加工提供一定的参考。