Influence of the emulsion components and preparation method on the laboratory‐scale preparation of o/w emulsions containing different types of dispersed phases and/or emulsifiers

Emulsification is a complex process, strongly influenced by emulsion composition as well as by preparation procedure, and the characterisation of emulsions with regard to their structure and stability can be carried out with many different methods. To evaluate the influences of emulsion composition and preparation procedure on the structure and properties, oil‐in‐water emulsions were prepared using the model dispersed phase dodecane and the surfactant Tween on the one hand and the real food components sunflower oil (dispersed phase) and casein (emulsifier) on the other hand. The emulsions were prepared in a small laboratory‐scale with a turbo‐mixer alone and in combination with ultrasonic treatment. The emulsion activity was measured by photometry, the emulsion stability was evaluated visually and the droplet size was determined by laser particle analysis. The results of the investigations made with the model substances agreed only partly with those made with the real food substances. For the model emulsions strong correlation were found between the emulsion activity and the particle sizer data because of the high purity and the defined structure of the model substances. On the contrary, for the emulsions made with the real food components sunflower oil and sodium caseinate the correlation were much weaker. Therefore, a proper characterisation of the structure and properties of food emulsions requires examinations with several methods which are independent from each other. Furthermore, for laboratory‐scale emulsification the combination of turbo‐mixer and ultrasonic treatment is suitable to obtain small droplets and a narrow droplet distribution also for very small emulsion volumes.     

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.     

超声预处理对花生分离蛋白微凝胶颗粒结构及其Pickering乳液特性的影响

为研究超声预处理对花生分离蛋白微凝胶颗粒（peanut protein isolate microgel particles,PPIMP）结构及其Pickering乳液特性的影响,选择超声功率为500 W,处理时间为10、20、30、40 min,通过粒径、Zeta电位、表面疏水性、红外光谱、乳化性等分析PPIMP的结构变化,并对其稳定的Pickering乳液的粒径分布、稳定性指数、流变特性进行系统表征。结果表明,超声时间为20 min时,PPIMP具有最小的粒径、最大的表面疏水性、乳化性和乳化稳定性,PPIMP的α-螺旋相对含量增加、β-折叠相对含量降低,蛋白质间的氢键被超声破坏,蛋白质分子展开。以PPIMP稳定的65%、70%、75%、80%油相体积分数的Pickering乳液,表现出典型非牛顿假塑性行为。油相体积分数为80%时,Pickering乳液最稳定。本研究结果证实了PPIMP可以作为一种有效的Pickering乳液稳定剂,有助于基于PPIMP高稳定性Pickering乳液的制备及在食品中的应用。     

The use of ultrasonics for nanoemulsion preparation

Oil-in-water emulsions are an important vehicles for the delivery of hydrophobic bioactive compounds into a range of food products. The preparation of very fine emulsions is of increasing interest to the beverage industry, as novel ingredients can be added with negligible impact to solution clarity. In the present study, both a batch and focused flow-through ultrasonic cell were utilized for emulsification with ultrasonic power generation at 20–24 kHz. Emulsions with a mean droplet size as low as 135 ± 5 nm were achieved using a mixture of flaxseed oil and water in the presence of Tween 40 surfactant. Results are comparable to those for emulsions prepared with a microfluidizer operated at 100 MPa. The key to efficient ultrasonic emulsification is to determine an optimum ultrasonic energy intensity input for these systems, as excess energy input may lead to an increase in droplet size.Industrial relevanceThe preparation of oil-in-water emulsions is a common feature of food processing operations. The use of ultrasound for this purpose can be competitive or even superior in terms of droplet size and energy efficiency when compared to classical rotor­stator dispersion. It may also be more practicable with respect to production cost, equipment contamination and aseptic processing than a microfluidisation approach. The present paper shows that ultrasound can be effective in producing nanoemulsions for use in a range of food ingredients.     

Droplet characterization and stability of soybean oil/palm kernel olein O/W emulsions with the presence of selected polysaccharides

Droplet characteristics, flow properties and stability of egg yolk-stabilized oil-in-water (O/W) emulsions as affected by the presence of xanthan gum (XG), carboxymethyl cellulose (CMC), guar gum (GG), locust bean gum (LBG) and gum Arabic (AG) were studied. The dispersed phase (40%) of the emulsions was based on soybean oil/palm kernel olein blend (70:30) that partially crystallized during extended storage at 5 °C. In freshly prepared emulsions, the presence of XG, CMC, GG and LBG had significantly decreased the droplet mean diameters. XG, LBG, GG and CMC emulsions exhibited a shear-thinning behavior but AG emulsion exhibited a Bingham plastic behavior and control (without gum) emulsion almost exhibited a Newtonian behavior. Both control and AG emulsions exhibited a severe phase separation after storage (30 days, 5 °C). The microstructure of stored XG emulsion showed the presence of partially coalesced droplets, explaining a large increase in its droplet mean diameters. Increases in droplet mean diameters and decreases in flow properties found for stored GG and LBG emulsions were attributed to droplet coalescence. Nevertheless, the occurrence of droplet coalescence in these emulsions was considered to be small as no free oil could be separated under centrifugation force. Increases in flow properties and excellent stability towards phase separation found for stored CMC emulsion suggested that CMC could retard partial coalescence. Thus, the results support the ability of CMC, GG and LBG in reducing partial coalescence either by providing a sufficiently thick continuous phase or by acting as a protective coating for oil droplets.     

椰子油纳米乳液制备工艺优化及其稳定性分析

为制备较为稳定的椰子油乳液,将酪蛋白酸钠(Sodium caseinate,SC)和黄原胶(Xanthan gum,XG)复合作为乳化剂,椰子油为油相,采用超声方法制备椰子油乳液。以平均粒径、Zeta-电位、离心稳定性及浊度等为考察指标,通过单因素实验筛选出超声功率、超声时间、油相质量分数和水相pH的合理研究范围。以平均粒径为响应值,用Box-Behnken响应面法对超声功率、超声时间和水相pH做进一步优化实验并对制备的乳液进行稳定性实验。结果表明,最佳制备工艺参数为:超声功率为480 W,超声时间为18 min,水相pH为7,所得椰子油纳米乳液的平均粒径为304.5±13.2 nm。所制备的椰子油纳米乳液在热处理温度40～90℃,pH6～8,离子浓度0～0.5 mol/L条件下具有良好的稳定性,且经3次冻融循环后乳液保持稳定,为构建用于食品加工的高稳定性椰子油乳液提供了理论支持。     

Viscosity change in oil/water food emulsions prepared using a membrane emulsification system

This paper reports viscosity measurements of oil/water (O/W) monodispersed emulsions of different droplet diameters obtained in a membrane emulsification system. Hydrophilic microporous glass membranes of different pore diameters were used to prepare O/W emulsions. The results showed that the droplet diameter of the emulsions varied with the average pore diameter of the membrane. The average droplet diameter was found to be about five times greater than the average membrane pore diameter. A correlation was found for the relationship between the average droplet diameter and the emulsion viscosity. As the dispersed droplet size became smaller, the total surface area of the droplets increased. Therefore, the emulsion viscosity and the relative viscosity increased. Few studies have reported the viscosity of O/W emulsions with droplet diameter of 5 μm or more and an oil phase concentration of 10 vol% or less. In the present study a correlation between the droplet diameter and the emulsion viscosity was statistically established. ©     

球磨-酯化复合改性槟榔芋淀粉对Pickering乳液形成的影响

为了提高淀粉颗粒的乳化能力,以球磨-酯化复合改性槟榔芋淀粉为颗粒乳化剂,大豆油为油相,制备水包油型Pickering乳液.采用激光粒度仪、研究级正置显微镜、流变仪等对Pickering乳液外观、液滴粒径、显微形态及动态流变特性进行表征,考察淀粉颗粒质量浓度(1、5、10、20、30 mg/mL)和油相体积分数(10％、...     

慢消化椰油乳液系列体系的构建及其微流变特性和体外消化特性对比

本文以椰子油为芯材,乳清分离蛋白(Whey protein isolate,WPI)为壁材制备单层椰油乳液,再以单层椰油乳液为芯材,分别以羧甲基纤维素钠(Carboxmethylcellulo sesodium,CMC)、纤维素纳米晶体(Cellulose nanocrystals,CNC)、壳聚糖(Chitosan,CNI)、微晶纤维素(Microcrystalline cellulose,MCC)为壁材制备四种双层椰油乳液,进而探究各乳液体系的微流变特性和体外消化特性。结果显示,WPI-CNC稳定的椰油乳液体系粘弹性最高(P<0.05),乳液中的粒子不能自由运动,乳液的固液平衡值最低(P<0.05),乳液中粒子运动的速率低;WPI-CNC稳定的椰油乳液有最低的肠释放率,且释放速率最为缓慢;除WPI-CNC稳定的椰油乳液外,各乳液体系经胃相消化后均出现明显聚集,小肠消化后聚集程度增加;WPI、WPI-CNC、WPI-CMC稳定的椰油乳液经过口腔、胃、肠消化后平均粒径依次增加,粒径分布出现多峰现象;肠消化后,各乳液表面负电位增大。综上,椰油乳液的流变学特性显著影响其体外消化率,WPI-CNC稳定的椰油乳液体外消化率最低且消化最慢。     

纳米SiO2改性4 种大分子材料的乳液制备及性质

为提高乳液稳定性,采用纳米SiO2改性明胶（gelatin,GE）、大豆分离蛋白、壳聚糖和阿拉伯胶（gum arabic,GA）制备茶油乳液。以乳化活性、乳化稳定性、离心稳定性、平均粒径、流变特性为考察指标,探究质量分数3.000%的纳米SiO2对4 种大分子材料复合乳液性质的影响,并对乳液的微观结构及油滴分布进行观察。结果表明,纳米SiO2能增强乳液稳定性,其中GE-纳米SiO2复合乳液综合性质最佳。添加纳米SiO2后乳化活性和乳化稳定性显著增加（P＜0.05）,离心稳定性降低68.444%。平均粒径为8.472 μm,乳液粒径最小且分布均匀,表面光滑呈球状。流变表现为典型的弱凝胶特性,稳定性良好。研究结果可为天然高分子和纳米SiO2乳液的制备和应用提供实践基础。     

Destabilization of protein-based emulsions by diglycerol esters of fatty acids – The importance of chain length similarity between dispersed oil molecules and fatty acid residues of the emulsifier

Destabilizing effects of diglycerol mono-esters of different saturated or one mono-unsaturated fatty acids (DF) on protein-based emulsions prepared with various types of oil were examined by visual observations and particle size analyses. By diglycerol esters of oleic acid (DO), a hexadecane-in-water emulsion was more obviously destabilized than an octadecane-in-water emulsion or food oil-in-water emulsions. Interfacial tension measurements indicated that the adsorbed protein on oil droplet surfaces of hydrocarbon emulsions can be more easily displaced by DO compared to the case of food oil emulsions. The degree of hydrocarbon emulsion destabilization by DO varied with the chain length of hydrocarbon molecules. From the results of combination tests of five hydrocarbons varying in chain length in oil phase and five DF having different mono-fatty acid residue, we described a possibility that DF could effectively destabilize the hydrocarbon emulsion when the chain length of fatty acid residue of DF was similar to that of hydrocarbon molecules.     

Wine lees: From waste to O/W emulsion stabilizer

Wine lees are the major waste from wine production, containing a noticeable amount of biomass (yeast, stalks, and peels), they could be used for the stabilization of dispersed systems such as emulsions. This work is focused on the determination of techno-functional properties of whine less produced from white grapes and industrial-grade blueberries. The interfacial characterisation was carried out by means of dilatational and interfacial shear rheology, whereas the characterisation of emulsion microstructure was assessed by droplet size distribution, rheological characterisation and backscattering measurements. The results obtained indicated that a high amount of polyphenols were present in wine less obtained from grape fermentation with industrial-grade blueberries as an additive, moreover, their presence also caused better interfacial properties (reducing the interfacial tension up to ca. 15 mN/m). However, the comparison of dilatational and interfacial-shear rheology determined that the interfacial response was caused by a densely packed structure. Fairly low droplet sizes (⁓ 320 nm) were obtained after ultraturrax® homogenization and further passing through the Microfluidizer® device, where the emulsions were stable only in presence of xanthan gum (0.06, 0.12 and 0.25 wt%). However, the suitable amount of XG gum was 0.06 and 0.12 wt% since no phase separation was observed in the emulsions generated over storage time, although flocculation phenomena took place. The results obtained exhibited emulsions with a suitable texture for the preparation of milk-shakes and brewages products, evidencing the potential of wine lees for these products.     

超细化豆渣作为皮克林乳液稳定剂的特性研究

将普通粉碎豆渣进行湿法超细化处理,研究超细化豆渣作为皮克林乳液稳定剂的特性,考察颗粒浓度、油相体积分数、pH及离子强度对乳液液滴尺寸、稳定性和流变学性质的影响。研究发现,超细化提升了豆渣颗粒的悬浮稳定性,且当油相分数φ=0.6,水相中豆渣颗粒质量分数≥0.4%时,形成皮克林乳液的粒径为80~140μm,在1~30 d存放期内乳析指数未发生显著变化。水相pH=7时乳液的粒径最大,pH降低时乳液的平均粒径呈单调递减,且乳液稳定性增强。水相中NaCl浓度在100~350 mmol/L对乳液粒径无显著影响。研究还表明,超细化豆渣稳定的皮克林乳液为剪切变稀型流体,其流变学特性受颗粒添加量及水相pH的影响。此研究表明,超细化豆渣具有良好稳定O/W型皮克林乳液的能力。     

大豆酸溶蛋白/大豆多糖纳米乳液的制备及表征

纳米乳液具有抗沉降和抗乳析动力学稳定性,是提高脂溶性物质的水溶性和生物利用度的有效手段。本论文探索了大豆酸溶蛋白(acid soluble soy protein,ASSP)/大豆多糖(soy soluble polysaccharides,SSP)纳米乳液的制备工艺,系统分析了p H条件、加油量、压力、质量比、热处理等因素对纳米乳液形成以及稳定性的影响。结果表明:在p H 3.0~4.0范围内,酸溶蛋白与大豆多糖质量比1:4,400 bar的压力下,可以很好地包埋5%~20%的油,此时制备的乳液粒径为269.33±2.26 nm,并且储存60天粒径无显著性变化(P0.05)。p H条件、高压以及热处理对乳液的稳定性具有显著影响(P0.05),ASSP/SSP纳米乳液适合食品工业中的酸性介质、高温以及高盐环境下的应用。通过果胶酶水解大豆多糖,对酸溶蛋白/大豆多糖纳米乳液的形态学进行了研究分析,结果表明酸溶蛋白/大豆多糖纳米乳液的微滴表面被多糖覆盖,大豆多糖能够很好地固定在微滴表面并使得纳米乳液微滴稳定和分散。     

Spray-dried whey protein/lactose/soybean oil emulsions. 2. Redispersability, wettability and particle structure

In the present paper redispersion and wettability experiments of spray-dried whey protein-stabilized emulsions are presented. Emulsion droplet size after redispersion gives information about eventual coalescence between emulsion droplets in the powder matrix during drying or storage, resulting in an increase in emulsion droplet size after redispersion. Results from redispersion experiments are combined with previously presented knowledge about powder surface composition and particle structure to elucidate internal processes in the powder matrix and external processes on the powder surface during drying and storage of whey protein powder. The results show that with addition of lactose to whey protein-stabilized emulsions, emulsion droplet structure remains intact in the powder matrix during drying since the emulsion droplet size in the redispersed spray dried emulsion is unchanged. In the absence of lactose there is a growth in emulsion droplet size after redispersion of the spray-dried whey protein-stabilized emulsion, showing that a coalescense of emulsion droplets occurs during the drying or redispersion process. Storage of the whey protein-stabilized powders in a humid atmosphere (relative humidity 75%, 4 days) induces changes in some powders. When the powder contains a critical amount of lactose there is a remarkable increase in emulsion droplet size after redispersion of humid stored powders compared with the emulsion before drying and with the redispersed dry stored powder. In addition, there is a release of encapsulated fat after humid storage of lactose-containing powders detected by electron spectroscopy for chemical analysis. For powders which do not contain any lactose there is no increase in emulsion droplet size after storage in a humid atmosphere compared with the redispersed dry stored emulsion. Addition of only a small amount of lactose prevents coalescence of emulsion droplets and the subsequent increase in droplet size during drying. If the lactose content is kept rather low neither an effect on the droplet size after storage under humid conditions nor a release of fat onto powder surfaces is detected. Furthermore, wettability of the spray-dried whey protein-stabilized emulsions by water is presented. It is concluded that it is beneficial to wettability in water to have as high a coverage of lactose on the powder surface as possible. In addition, a review of particle structure for powders of various composition is presented.     

Quinoa starch granules: a candidate for stabilising food-grade Pickering emulsions

BACKGROUND: Particle‐stabilised emulsions, so‐called Pickering emulsions, are known to possess many beneficial properties, including being extremely stable. Starch granules isolated from quinoa have been used as emulsion stabilising particles. The granules were intact, 1–3 µm in diameter and modified with octenyl succinic anhydride to increase their hydrophobicity. Starch granules, as opposed to most other particles used to generate Pickering emulsions, are edible, abundant and derived from natural sources. RESULTS: Emulsions produced by high shear homogenisation had droplet sizes of 9–70 µm depending on the starch‐to‐oil ratio. Droplet size decreased with increasing starch‐to‐oil ratio, but was unaffected by the oil phase volume over a range of 5–33% oil (v/v). Although the drops were large and subject to creaming, their size remained unchanged over a period of 7 days. By adjusting the starch‐to‐oil ratio drops could be made to be buoyancy neutral to prevent creaming. Rheological characterisation indicated a gel structure with an elastic modulus in the range 200–2000 Pa depending on droplet size. CONCLUSION: This work has demonstrated the successful use of starch granules to stabilise emulsions which may find applications beyond that of food, for example in cosmetics and pharmaceutical formulations. Copyright © 2012 Society of Chemical Industry     

超声辅助均质制备负载人参皂苷功能型Pickering乳液的工艺优化

目的 研制一种基于乳清分离蛋白和菊粉负载人参皂苷的Pickering乳液。方法 以乳清分离蛋白与菊粉复合溶液为水相,大豆油为油相,应用超声和均质处理方法制备负载人参皂苷的Pickering乳液。通过单因素试验考察乳清分离蛋白与菊粉的质量分数比、超声功率、超声时间、均质时间对人参皂苷乳液粒径的影响,利用Box-Behnken试验设计和响应面分析确定人参皂苷Pickering乳液的制备工艺。结果 对人参皂苷Pickering乳液粒径的影响程度从大到小依次为超声时间、均质时间、超声功率。优化的制备工艺参数:超声功率272.0 W、超声时间17.0 min、均质时间6.0 min,乳清分离蛋白与菊粉的质量分数比1:1.0。在优化条件下制备的人参皂苷Pickering乳液粒径最小为(318.73±1.24) nm。结论 应用超声辅助均质处理,制备基于乳清分离蛋白和菊粉负载人参皂苷的Pickering乳液工艺可行,为进一步构建人参皂苷纳米输送体系和功能食品研发奠定基础。     

Formulation and rheological characterization of reduced-calorie food emulsions

Water-in-oil-in-water (W/O/W) double emulsions are systems where a water-in-oil emulsion (W/O) is dispersed in a second aqueous phase. The W/O emulsion exists in the suspending aqueous medium as oil globules containing smaller water droplets.
In this work, a selection of both materials and procedures has been made in order to obtain an optimal formulation of a W/O/W food emulsion for both yield and rheologica] properties.
The rheological properties of W/O/W emulsions have been studied by means of both steady-shear and oscillatory measurements, and appeared to be similar to those of a simple O/W emulsion having the same volume fraction of dispersed phase, but lower oil content.
This is of great interest to the food industry, since producing double emulsions with the same texture as simple ones, but a lower oil content, helps to formulate reduced-calorie foods.     

Emulsion gels: The structuring of soft solids with protein-stabilized oil droplets

Many food products can be categorized as emulsion gels. This is especially the case for protein-based oil-in-water emulsions which can be converted into soft-solid-like materials by common food processing operations such as heating, acidification, and enzyme action. This review article outlines how the rheological and structural properties of protein-stabilized emulsion gels are influenced by the dispersed oil volume fraction, the oil–water interfacial composition, and the colloidal interactions of the constituent emulsion droplets. For model systems of variable oil content and containing different food proteins, some general trends of rheological behaviour at small and large deformations are identified. Experimental rigidity data are considered in relation to: (i) material science theories of the reinforcement of solid materials by active and inactive filler particles, and (ii) Brownian dynamics simulations of aggregated particle networks containing bonded and non-bonded particles. Influences of interfacial composition and particle–matrix interactions on microstructure and rheology are explained with particular reference to the role of small-molecule surfactants. Compositional and structural factors affecting the large-deformation rheology and fracture properties are described. Finally, the practical relevance of the model system studies to the behaviour of real food products is critically assessed.