Preparation and Characterization of Water/Oil/Water Emulsions Stabilized by Polyglycerol Polyricinoleate and Whey Protein Isolate

ABSTRACT: In this study we tried to prepare stable water-in-oil-in-water (W/O/W) emulsions using polyglycerol polyricinoleate (PGPR) as a hydrophobic emulsifier and whey protein isolate (WPI) as a hydrophilic emulsifier. At first, water-in-oil (W/O) emulsions was prepared, and then 40 wt% of this W/O emulsion was homogenized with 60 wt% aqueous solution of different WPI contents (2, 4, and 6 wt% WPI) using a high-pressure homogenizer (14 and 22 MPa) to produce W/O/W emulsions. The mean size of final W/O/W droplets ranged from 3.3 to 9.9 μm in diameter depending on the concentrations of PGPR and WPI. It was shown that most of the W/O/W droplets were small (<5 μm) in size but a small population of large oil droplets (d > 20 μm) was also occasionally observed. W/O/W emulsions prepared at the homogenization pressure of 22 MPa had a larger mean droplet size than that prepared at 14 MPa, and showed a microstructure consisting of mainly approximately 6 to 7-μm droplets. When a water-soluble dye PTSA as a model ingredient was loaded in the inner water phase, all W/O/W emulsions showed a high encapsulation efficiency of the dye (>90%) in the inner water phase. Even after 2 wk of storage, >90% of the encapsulated dye still remained in the inner water phase; however, severe droplet aggregation was observed at relatively high PGPR and WPI concentrations.     

Release rate profiles of magnesium from multiple W/O/W emulsions

Water-in-oil-in-water (W/O/W) emulsions were formulated based on rapeseed oil, olive oil, olein and miglyol. Polyglycerol polyricinoleate and sodium caseinate were used as lipophilic and hydrophilic emulsifiers, respectively. Magnesium was encapsulated in the inner aqueous droplets. Emulsion stability was assayed through particle sizing and magnesium release at two storage temperatures (4 and 25 °C) over 1 month. Irrespective of the oil nature, both the primary W/O and W/O/W emulsions were quite stable regarding the size parameters, with 10-μm fat globules and 1-μm internal water droplets. Magnesium leakage from W/O/W emulsions was influenced by the oil type used in the formulation: the higher leakage values were obtained for the oils characterized by the lower viscosity and the higher proportion of saturated fatty acids. Magnesium release was not due to droplet–globule coalescence but rather to diffusion and/or permeation mechanisms with a characteristic rate that varied over time. In addition, W/O/W emulsions were resistant to various thermal treatments that mimicked that used in pasteurization processes. Finally, when W/O/W emulsions were placed in the presence of pancreatic lipase, the emulsion triglycerides were hydrolysed by the enzyme. These results indicated a possible use of W/O/W emulsions loaded with magnesium ions in food applications.     

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.     

米糠蛋白O/W及W/O/W乳液制备及界面稳定性

为对比不同米糠蛋白质量浓度下O/W及W/O/W乳液的稳定性,以米糠蛋白作为基料,采用双乳化法制备O/W及W/O/W乳液,考察不同米糠蛋白质量浓度下乳液的微观形态和稳定性并探究其界面稳定机理。结果表明：W/O/W乳液的贮存稳定性显著优于O/W乳液;与相同蛋白含量的O/W乳液相比,W/O/W乳液的黏度显著提高;当米糠蛋白质量浓度为0.4 g/100 mL时,W/O/W乳液的稳定性较O/W乳液提高了1 倍以上;乳液内部包裹更多的W/O液滴,W/O/W乳液的粒径较大;而此时静电斥力也较大,起到稳定乳液的目的。同时,米糠蛋白质量浓度不小于0.4 g/100 mL时,O/W及W/O/W乳液中蛋白质的吸附率较高,达到78%以上。本研究为天然米糠蛋白质在食品级乳液中的开发提供参考,为粮食副产物的综合利用提供了新思路。     

Effects of water-soluble soybean polysaccharide on rheological properties,stability and lipid digestibility of oil-in-water emulsion during in vitro gastrointestinal digestion

Water-soluble soybean polysaccharide (SSPS) is a naturally occurring emulsifier. SSPS was used as the sole emulsifier to stabilize an oil-in-water (O/W) emulsion. The effects were investigated of different SSPS concentrations (3–20% (w/w)) on the lipid digestibility, rheological properties and stability of O/W emulsions during in vitro digestion model. The droplet size of the emulsions tended to increase during the oral phase because the emulsions were unstable and droplets coalesced, except with a SSPS concentration of 20% (w/w). The presence of SSPS markedly reduced the free fatty acid (FFA) content after its stabilized O/W emulsion passed through in vitro gastrointestinal digestion. The amount of FFA significantly decreased as the concentration of SSPS increased due to SSPS stabilization film on oil droplet surface and high viscous system. SSPS may be an attractive alternative ingredient to control the lipid digestibility of emulsions for various food products.     

W/O/W多重乳状液的实验研究

研究了W/O/W多重乳状液的制备方法及影响其稳定性的因素。通过正交试验选出较佳的工艺参数,获得了较稳定的W/O/W多重乳状液。     

Enhancing anti-inflammation activity of curcumin through O/W nanoemulsions

High-speed and high-pressure homogenized O/W emulsions using medium chain triacylglycerols (MCT) as oil and Tween 20 as emulsifier, with mean droplet sizes ranging from 618.6 nm to 79.5 nm, have been successfully prepared. The enhanced anti-inflammation activity of curcumin encapsulated in O/W emulsions is evidenced by the mouse ear inflammation model. There is a 43% or 85% inhibition effect of 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced edema of mouse ear for 618.6 nm and 79.5 nm 1% curcumin O/W emulsions, respectively, but a negligible effect is found for 1% curcumin in 10% Tween 20 water solution.     

The effect of the type and the concentration of the lipophilic surfactant on the stability and release kinetics of the W/O/W multiple emulsions

Stable multiple emulsions that contain different lipophilic surfactants in the internal aqueous phase have been formulated. The multiple systems were assessed by evaluating several parameters such as macroscopic aspect, droplet size, percent release and accelerated stability under centrifugation or elevated temperature. The effect of polymeric and monomeric surfactants on the release mechanism and stability was examined. An excess of monomeric surfactant in the oil phase enhances the release rate and decreases stability. The release rate can be decreased by an increase of the lipophilic surfactant concentration. It appears that the more the oil globule swells, the less hydrosoluble drug is released. As a result a high swelling capacity is associated with better stability.     

O/W emulsion and W/O/W multiple emulsion: physical characterization and skin pharmacokinetic comparison in the delivery process of caffeine

The aim of this study was to compare the characteristics of an O/W emulsion and a W/O/W emulsion, formulated with similar ingredients. The physical properties of these two types of vehicles were characterized first. Using three types of in vitro models, human skin biopsies, nitrate acetate cellulose membranes and human reconstituted epidermis, the delivery potential of each vehicle for one hydrophilic drug, caffeine, was compared. The assessment of physical parameters, such as particle size, conductivity and rheological behavior enabled the nature of the test emulsions to be clearly identified. Clear differences were observed in the ability of each type of emulsion to deliver caffeine. Whatever the nature of the membrane used for the pharmacokinetic study, the absorption of caffeine was roughly two-fold lower (2.6 for human skin) when the W/O/W multiple emulsion was used as the vehicle. The concomitant determination of physical and kinetic properties of these two test emulsions allowed the W/O/W multiple emulsion and a simple O/W emulsion to be clearly differentiated.     

Preparation of Monodisperse Food-Grade Oleuropein-Loaded W/O/W Emulsions Using Microchannel Emulsification and Evaluation of Their Storage Stability

W/O/W emulsion is an emerging system in developing new functional and low-calorie food products. The aim of this study is to produce food-grade monodisperse water-in-oil-in-water (W/O/W) emulsions loaded with a hydrophilic bioactive oleuropein. W/O/W emulsions were prepared via high-pressure homogenization and subsequent microchannel (MC) emulsification. The internal aqueous phase was a 5-mM sodium phosphate buffer containing d(+)-glucose (5 wt.%) and oleuropein (0.1–0.7 wt.%). The oil phase consisted of soybean oil and tetraglycerin monolaurate condensed ricinoleic acid esters (TGCR; 3–8 wt.%). The external aqueous phase was a 5-mM sodium phosphate buffer containing d(+)-glucose (5 wt.%) and decaglycerol monolaurate (1 wt.%). Oleuropein-loaded submicron W/O emulsions with average droplet diameters as small as 0.15 μm and monomodal droplet size distributions were prepared by high-pressure homogenization when applying high TGCR concentrations of 5–8 wt.% and low oleuropein concentrations of 0.1–0.3 wt.%. Monodisperse oleuropein-loaded W/O/W emulsions with average W/O droplet diameters of around 27 μm and coefficients of variation of below 5 % were successfully prepared when using a silicon MC array plate with wide channels of 5-μm depth and 18-μm width. The monodisperse W/O/W emulsions prepared at high TGCR concentrations and low oleuropein concentrations were the most stable during 40 days of storage. The adsorption behavior of oleuropein at the internal aqueous–oil interface was relevant to W/O/W emulsions microstructure and stability. The results are believed to provide useful information for successfully preparing stable monodisperse W/O/W emulsions loaded with hydrophilic functional compounds. The surface activity of the loaded material seems to be a key parameter in optimizing the formulation of W/O/W food emulsion.     

壳聚糖W/O型乳状液的超声辅助制备及其稳定性

以非牛顿假塑性大分子壳聚糖溶液为水相,棕榈油为油相,Span-80为乳化剂,采用单因素试验及响应面试验优化超声协助制备W/O型乳液工艺,并考察优化条件下制备的乳液稳定性.结果表明:内水相含量是影响乳液粒度大小的关键因素,且超声功率对乳液的粒度及其分布存在过处理现象.优化工艺为超声功率300 W、超声时间15 min、内...     

Water/Oil Emulsions Prepared by the Membrane Emulsification Method and Their Stability

We developed and tested a simple method to measure dispersed droplet size of W/O emulsions. Then, using a microporous glass membrane treated with oil phase, we produced a W/O emulsion with high water content (40% w/w) at a high emulsification rate by the membrane emulsification method, and assessed its stability. In comparison with emulsions by the stirring methods, variations in dispersed droplet size and viscosity of emulsions by membrane method were small and the emulsions were more stable. Droplet size was not related to the stability of the W/O emulsion prepared by membrane emulsification.     

W/O/W型复乳的制备优化及包埋矢车菊素-3-葡萄糖苷效果分析

研究制备方法和乳化剂对W/O/W型复乳稳定性的影响,优化工艺参数,并研究体系包埋矢车菊素-3-葡萄糖苷（cyanidin-3-glucoside,C-3-G）的效果。得到优化条件：初乳搅拌速率15 500 r/min、复乳搅拌速率7 000 r/min、油相乳化剂聚甘油蓖麻醇酯添加量16%、亲水性乳化剂的亲水亲油平衡值10、亲水性乳化剂添加量10%,优化后离心保留率达到80.25%。利用优化得到的复乳体系包裹C-3-G,发现复乳对C-3-G有良好的包裹能力,复乳对C-3-G的载药量为1 500 mg/L,包封率为98.08%,且C-3-G的包埋提高内水相渗透压和复乳稳定性。     

Protection of Lactobacillus acidophilus from the low pH of a model gastric juice by incorporation in a W/O/W emulsion

The protective effect of a W/O/W emulsion for Lactobacillus acidophilus from a model gastric juice was investigated in order to develop a method for utilizing the advantages of the probiotics. The bacteria were included in the inner-phase solution of the W/O/W emulsion, and a method for counting the viable-bacteria included in the W/O/W emulsion was developed. The relative viability of the bacteria included in the W/O/W emulsion was 49% at 2 h in the model gastric juice, whereas the viability of the bacteria directly dispersed in the juice declined to 1.3% even at 0.67 h. The relative viabilities of the encapsulated bacteria in the model gastric juice at 2 h were 0.12 and 1.10 for the emulsions having the median diameters of 11.9 and 25.4 μm, prepared with inner-phase volume ratios at 0.03 and 0.45, respectively. The relative viabilities of the bacteria in the W/O/W emulsions with the median diameters of 11 and 27 μm, prepared at the homogenization speed of 2.2×10⁴ and 9.8×10³ rpm, were 0.4 and 0.8, respectively. These results suggested that both the inner-phase volume ratio and the median diameter of oil droplet affected the relative viability of the included bacteria.     

Characterisation of O/W emulsions encapsulating ergocalciferol using onion skin waste saponins: insights on formulation and release properties

The study was conducted to produce ergocalciferol (Vit-D₂) loaded oil-in-water (O/W) emulsions utilising the onion skin waste saponins (OSW) as a natural emulsifier and almond oil as carrier oil. The impact of different formulations upon the digestibility of lipids, LCT (long-chain triglycerides) or MCT (medium-chain triglycerides), and bioaccessibility of Vit-D₂ was analysed. The mean particle size diameter of almond oil-based O/W emulsions was decreased with increasing homogenisation pressure and emulsifier concentration. During 120 mins of digestion in small intestinal fluids (SIF), almond oil in high-lipid emulsions (5% w/w) was not fully digested, resulting in a lower bioaccessibility of ergocalciferol than low-lipid samples. Almond oil emulsions with larger particle size have a slower rate of lipid digestion than the smaller size particles, but the release rate of free fatty acids was constant throughout the digestion process. Moreover, almond oil emulsions showed similar Vit-D₂ bioaccessibility to the oil-based emulsions but were much higher than MCTs.     

A Novel Approach to Improving the Quality of Bittern-Solidified Tofu by W/O Controlled-Release Coagulant. 1: Preparation of W/O Bittern Coagulant and Its Controlled-Release Property

To explore the controlled-release capacity and potential application of water in oil (W/O) emulsions, W/O emulsions with bittern solution as the aqueous phase were prepared with polyglycerol polyricinoleate (PGPR) as the emulsifier. Several factors that influenced the preparation of W/O bittern coagulants were investigated. Optimized conditions were applied as follows: bittern solution/oil phase at 4:6 or 5:5 (w/w), processing temperature at 65 °C, emulsifier concentration higher than 0.6 wt% and high-pressure homogenization at 60 MPa; W/O emulsions that had a good particle size distribution, good rheological properties, good embedding ratio and high stability were prepared. The optimized W/O emulsions also exhibited the expected controlled-release ability, affected by the bath temperature, shear speed and emulsion characteristics. The preliminary results also showed that the application of W/O emulsions has the potential to improve tofu quality by delaying the solidification of soybean protein and creating a much smoother and finer gel structure.     

乳化体系中花生油氧化稳定性的研究

主要探讨花生油乳化体系中乳化剂类型、用量、pH值、EDTA、温度等对花生油氧化稳定性的影响,结果显示:乳化剂种类和pH对于乳状液体系的氧化稳定性有显著影响,阴离子乳化剂SDS稳定的乳化液,pH4.0的氧化速率最快;非离子乳化剂Tween20稳定的乳化液,pH的影响不是很显著;阳离子乳化剂CTAB稳定的乳化液,随着pH的升高,氧化速率变快。乳化液体系中微量金属离子对于体系也有相当大的影响,随着金属离子螯合剂EDTA浓度的增加,其乳化体系中花生油的氧化速率显著降低。乳化剂用量也会影响体系的氧化稳定性,随着乳化剂用量的增加,乳化乳化体系中花生油的氧化稳定性降低。     

A Novel Approach to Improving the Quality of Bittern-Solidified Tofu by W/O Controlled-Release Coagulant. 2: Using the Improved Coagulant in Tofu Processing and Product Evaluation

To improve the quality and yield of traditional firm tofu prepared with bittern as coagulant, water-in-oil (W/O) emulsions with bittern solution as the aqueous phase, where the ratio of the bittern solution to the oil phase was 1:1.5 or 1:1 (w/w), and an emulsifier at a concentration of 0.8 or 1.0 wt.% were prepared. The parameters water content, water-holding capacity, yield, texture, and microstructure of the tofu were tested. The results indicated that the bittern W/O emulsions provided satisfactory controlled-release application potential. The use of the W/O emulsions significantly improved tofu’s water content, and the product remained moist for at least 24 h. Moreover, emulsified bittern increased the yield and made the gel network more homogenous and compact compared with the control. As expected, emulsions with an emulsifier concentration of 1.0 wt.% showed slightly better controlled-release capacity than those with 0.8 wt.%.     

超声处理大豆分离蛋白与壳聚糖复合物对O/W型乳液稳定性的影响

为探究超声处理大豆分离蛋白-壳聚糖（soybean protein isolate-chitosan,SPI-CS）复合物对形成O/W型乳 液性质的影响,主要研究了复合物表面疏水性、乳化活性、乳化稳定性与油-水界面张力、乳液粒径、乳液稳定性 之间的关系。结果表明：未经超声处理的SPI-CS复合物表面疏水性、乳化活性、乳化稳定性和界面吸附性较低,形 成的O/W型乳液粒径相对较大,约100 μm,乳液Zeta电位较低,乳滴有发生聚集的倾向。乳液贮存7 d后乳层析指数 最高。经超声处理后SPI-CS复合物形成的乳状液性质发生明显变化,随着超声功率的增加,形成的O/W型乳液的稳 定性有所增加：超声功率为400 W时SPI-CS复合物形成的乳液最为稳定,乳层析指数最低;当超声功率超过400 W 时,乳液的光学显微镜观察显示其粒径有所增大,同时乳液的Zeta电位、乳化活性和乳化稳定性明显下降,界面张 力降低缓慢。超声处理暴露了蛋白质分子的内部结构,使部分结构展开、柔性增加,促进了其与壳聚糖之间的静电 相互作用,说明超声处理的大豆分离蛋白与壳聚糖形成的复合物影响了O/W型乳液的稳定性及相关性质。     

Impact of iron encapsulation within the interior aqueous phase of water-in-oil-in-water emulsions on lipid oxidation

Iron (Fe³⁺) was encapsulated within the internal aqueous phase of water-in-oil-in-water (W/O/W) emulsions, and then the impact of this iron on the oxidative stability of fish oil droplets was examined. There was no significant change in lipid droplet diameter in the W/O/W emulsions during 7 days storage, suggesting that the emulsions were stable to lipid droplet flocculation and coalescence, and internal water diffusion/expulsion. The initial iron encapsulation (4 mg/100 g emulsion) within the internal aqueous phase of the water-in-oil (W/O) emulsions was high (>99.75%), although, a small amount leaked out over 7 days storage (≈10 μg/100 g emulsion). When W/O/W emulsions were mixed with fish oil droplets the thiobarbituric acid-reactive substances (TBARS) formed decreased (compared to fish oil droplets alone) by an amount that depended on iron concentration and location, i.e., no added iron < iron in external aqueous phase < iron in internal aqueous phase. These differences were attributed to the impact of W/O droplets on the concentration and location of iron and lipid oxidation reaction products within the system.