W/O emulsions: solvent phase separation for pH determination

The aim of this investigation was to find a measure for the phase separation by substances capable of rapidly demulsifying emulsions, which is necessary for the correct determination of the pH in cosmetic W/O emulsions. Results are reported for pH determination in the separated water phase of W/O emulsions containing metal soaps, micropigments and thermally unstable active agents. Of the substances investigated – solvents of different polarity and electrolytes – the best were mixtures of the polar butanol, which has a surfactant-like molecular structure and limited oil and water solubility, and the low polar trichloromethane which in particular has strong fat- and wax-dissolving properties. The combination achieved within 10 to 20 min at room temperature complete phase separations. Stable preparations, based on a polymer emulsifier (cetyl dimethicone copolyol), were demulsified as well as metal soap stabilized creams which characteristically contain a high amount of stabilizing waxes. The so-called solvent phase separation method was confirmed by using model preparations of known pH. During the investigation of model emulsions matching those used in practice, it was found, for example, that magnesium and aluminium stearate as well as various types of micronized zinc oxide which are dissolved or dispersed in the oil phase can shift the pH of the aqueous phase during manufacture from an initial acidic value through neutral to pH 8–10. Time-related and temperature-related changes in pH in formulations containing thermally unstable additives such as dihydroxyacetone or urea can be easily monitored.     

Gel‐like emulsions prepared with zein nanoparticles produced through phase separation from acetic acid solutions

In this article, we report the microstructure and rheological property of Pickering emulsions stabilised with zein nanoparticles prepared through phase separation from acetic acid solution. The fresh emulsions showed liquid‐like behaviour and reasonable small droplet size. Interestingly, after 3 days of storage at 25° C, the emulsions changed into solid‐like state. The viscosity remarkably increased, and the storage modulus was much larger than the loss modulus. These results indicate the formation of the gel‐like network in emulsions. The droplet size also showed an obvious increase, while the big droplets could be disrupted into small ones in the presence of sodium dodecyl sulphate. The particle network in the continuous phase was seen in the confocal laser scanning microscopy. Therefore, it is suggested that the gel‐like network is formed by the flocculation of oil droplets and particle network in continuous, mainly through the hydrophobic interactions between the particles.     

Phase separation in aqueous gelatin–κ-carrageenan systems

At low ionic strength (μ=0.002), pH=5.0 (close to the isoionic point (iip=4.8)) and total biopolymers' concentration (TBC) less than 0.2% w/w, gelatin is compatible with κ-carrageenan (κCG). When TBC is higher than 0.2% w/w, gelatin forms water-insoluble complexes with κCG and phase separation is observed independently of pH (3.0–9.0) and temperature, and is characterised by a relatively small degree of co-precipitation, which increases when TBC in the initial mixture increases. At pH=5.0, the yield of complex precipitated is maximal at a 3.0 molar ratio of gelatin and κCG in the initial mixture. The complexes are formed and stabilised via electrostatic interactions, rather than through hydrogen bonds or hydrophobic interactions and an “all or none” type complex formation mechanism takes place. At μ=0.1–0.2 (NaCl) pH≥iip, and 313 K, neither co-precipitation nor incompatibility were observed in an overwide range of total biopolymers' concentration (0.01–25% w/w). At μ=0.35, pH=5.0 and 313 K, gelatin exhibits incompatibility with κCG when the concentration of κCG in the initial mixture is higher than 0.65% w/w. The phase diagram of the system, in the above mentioned conditions, indicates a possible specific interaction of the two biopolymers even at a very high ionic strength.     

Optimization of emulsions

The optimization of three emulsions with predetermined components was performed by the aid of experimental design. Three different surfactants were compared: the salts of hexadecylhydrogenphosphate with diethanolamine, lysine and arginine respectively. Optimized microemulsions showed quite high stabilities towards centrifugation (30–60 min at 7000 rpm). The results showed that the counter-ion can affect the composition and stability of an emulsion.     

防透明聚酯纤维的结构与性能研究

应用SEM、IR、X-射线衍射及物理机械性能测试,分析了防透明聚酯纤维的结构与性能。结果表明：防透明聚酯纤维的横截面是不规则的,且在纤维表面分布有一些微粒;其红外谱图和X衍射谱图与普通聚酯纤维类似;较之普通聚酯纤维,防透明聚酯纤维断裂强度低,但摩擦系数大;所测试的防透明聚酯纤维的卷曲特性符合精梳毛纺要求。     

Modified pectins in whey protein emulsions

In the present work high methoxylic, low methoxylic and amidated pectins were tested for their actions in whey protein emulsions using a broad variation in the emulsion composition (content of protein, pectin, oil) and the solvent conditions (pH, ionic strength). Emulsifying activity index, long term stability and the particle size of the emulsions were determined, protein and galacturonan content of the serum were analysed after centrifugation. A strong relationship was found between emulsion stability and degree of esterification of the pectin, the influence of pectin amidation was relatively low. There were formed stable electrostatic complexes between the protein and the carboxylic groups of the pectin. They seemed to be much more important for emulsion stability than the hydrophobic or hydrogen bonds. The emulsion properties varied in dependence on the content of the single emulsion components and on the solution conditions. All pectins used stabilized the whey protein emulsions if their concentration was high enough. For any individual utilization it is necessary to choose the best suitable pectin.     

防透明纤维的开发及其在毛纺上的应用

主要研究了利用Mie散射理论优化防透明纤维开发中的添加微粒选择。基于Mie散射理论,通过Matlab编程计算,详细分析了添加微粒的相对折射率、尺度参数以及入射光波长对消光系数的影响。结果表明:在入射光波长和微粒折射率确定的条件下,单颗粒的消光系数强烈依赖于其尺寸大小,且存在唯一的对应最大消光系数的微粒尺寸;而随着微粒相对折射率的增加,消光系数增大;最后在不考虑色散的前提下,消光系数随着入射光波长的变化规律与微粒尺寸紧密相关。在防透明纤维开发中,应尽可能选择相对折射率大的微粒,同时微粒的尺寸大小和分布也应合理选择。最后举例说明了防透明纤维在毛纺产品开发中的应用。     

Aspects of milk-protein-stabilised emulsions

Milk proteins are widely used as ingredients in prepared foods, in which they perform a wide range of key functions, including emulsification, thickening, gelling and foaming. An important functionality of milk proteins in food colloids is their ability to facilitate the formation and stabilisation of oil droplets in emulsions. The ability of milk proteins to adsorb at the oil–water interface and to stabilise emulsions has been exploited by the food industry in the manufacture of nutritional products, specialised medical foods, dietary formulations, cream liqueurs and dairy desserts. This article provides an overview of the properties and functionalities of food emulsions formed with milk proteins, focusing on the structure and composition of adsorbed protein layers, competition between proteins and the physical and chemical stability of emulsion droplets. Of particular importance is the understanding of the behaviour of milk-protein-based emulsions under the conditions relevant to digestion in the human gastrointestinal tract. Recent relevant research in this area is reviewed and discussed.     

Phase separation in biopolymer gels: a low- to high-solid exploration of structural morphology and functionality

Phase separation in protein and polysaccharide gels remains one of the basic tools of achieving the required structural properties and textural profile in food product formulations. As ever, the industrialist is faced with the challenge of innovation in an increasingly competitive market in terms of ingredient cost, product added-value, and expectations of a healthy life-style to mention but a few. It appears, however, that a gap persists between the fundamental knowledge and a direct application to food related concepts with a growing need for scientific input. Furthermore, within the context of materials science, there is a tendency to examine research findings in either low- or high-solid systems without considering synergistic insights/benefits to contemporary needs, spanning the full range of relevant time-, length-, and concentration scales. This review highlights the latest attempts made to utilize and further develop fundamental protocols from the advanced synthetic polymer research as a source of inspiration for contemporary bio-related applications in low- and intermediate-solid composite gels. Then, it takes advantage of this school of thought to "force a passage" through the phase topology and molecular dynamics of binary biopolymer mixtures at high levels of co-solute. It is hoped that these phenomenological and fundamental tools should be able to bridge the divide in the analysis of the two "types" of composite materials (from low to high solids) thus dealing effectively with the specific and often intricate problems of their science and applications.     

饮料用乳化香精研究进展

综述了饮料用乳化香精的定义、特点、浊度和稳定性的原理和影响因素、主要原料、乳化工艺、分析方法及其进展。     

Emulsifying properties of lactose-amines in oil-in-water emulsions

Lactose-amines were synthesized with hexadecyl-amide and lactose via the Maillard reaction and their emulsion stabilization properties were investigated. Lactose-amines were synthesized using two different constant heating (4 and 8 h) and two different heating/cooling cycles (12 and 24 h). Each lactose-amine sample was used as an emulsifier in 20:80 ratio oil-in-water emulsions at four different concentrations (0.01%, 0.05%, 0.1%, and 1%). Emulsion stability was monitored by measuring the oil droplet sizes and the extent of destabilization via clarification over 5 days. At 1% concentrations, emulsions prepared with lactose-amines synthesized for 4, 12, and 24 h were as stable as the whey protein positive control emulsion. The 8 h lactose-amine sample resulted in a less stable emulsion. We assume the difference is related to the amount of heat this sample was exposed to during synthesis, with extensive heat leading to advanced Maillard products, which possessed reduced emulsification properties.     

Rheology of siloxane-stabilized water in silicone emulsions

Using silicone copolymers in personal care products can improve the aesthetic performance of formulations. During their manufacture, distribution and topical application they are subject to various mechanical stresses. In this study rheology was used to measure their effects. A number of water in silicone (w/Si) emulsions were prepared in which the oil phase consisted of cyclomethicone. The surfactant used was a branched type silicone copolymer. Both viscoelastic and viscometry measurement were performed on model systems and on commercial products. Experimental data were obtained using a Bohlin rheometer. The measurements were taken applying shear rates in the range of 0.46-58 l s-1 and for the strain sweep frequencies of 0.1 Hz, 1 Hz and 10 Hz were applied. Oscillation tests were performed in the 0.1 Hz to 10 Hz range. All measurements were taken at 35deg;C, representing the approximate temperature encountered during topical application. The effect of surfactant concentration on viscoelastic properties was examined. It was shown that with increasing surfactant concentration the elastic moduli G' and the viscous moduli G" increased. Furthermore, the emulsions showed a transition from a predominantly elastic to a predominantly viscous response as the surfactant concentration increased. The effect of varying the water phase volume fraction on viscometry and viscoelastic measurements was also examined. With increasing water phase volume fraction the viscosity of the emulsions, as well as the yield stress, increased. The Cross and Sisko models were applied. From the Dougherty and Krieger equation phieff was calculated. It was found the the data derived from the Sisko model gave more reliable results. Results obtained from commercial samples showed a high proportion of elasticity; oscillation tests and viscometry experiments suggested that tumbling had the biggest impact on the theological profiles; viscosity, eta, shear stress, sigma, elastic module, G', and dynamic viscosity, eta', dropped to a minimum in these samples. Results from the two commercial samples were compared and it was observed that, although both were w/o emulsions, different rheological behaviour could be observed.     

Micromixers to produce cosmetic emulsions

In the cosmetics industry, emulsions play a key-role in active solubilization and texture/efficacy optimization. However, depending on their physico-chemical properties, the active ingredients are often more stable in a single phase: for example, Vitamin A is more stable in an oily phase than in a water phase. We have developed a special mixing device which produces an emulsion in the body of the pump, immediately before application on the skin. The mixing unit consists of two silicon chips. Each chip has several Y-shaped microchannels and intersections etched on its upper surface. When the two etched surfaces are bonded together, they produce series of interconnecting micromixing elements which permit the repeat mixing of the two phases, thus producing an extremely homogenous emulsion. These micromixers require carefully designed formulae in which the physico-chemical properties of each raw material are essential to obtain a spontaneous emulsion. This device has been incorporated into a spray pack and optimized to deliver the spontaneous emulsion when finger pressure is applied.     

Innovative applications of food-related emulsions

Research on oxidative stability of multiple emulsions is very scarce. Given that this is a relevant topic that must be ascertained before the successful application of multiple emulsions in foods (especially when a combination of highly unsaturated oils is used as a lipid phase), this review mainly focuses on various aspects of the multiple emulsions.

Fat replacement in meat products using emulsions is critically discussed along with innovative applications of natural antioxidants in food-based emulsions and multiple emulsions based on bioactive compounds/encapsulation as well as confectionery products.     

Efficiency and usability of silicone surfactants in emulsions

The critical micelle contration (CMC) of silicone surfactants was determined to provide their optimal efficiency in emulsion systems. The lowest CMC value was found for the amphionic polysiloxane polyorganobetaine copolymer, which is undoubtedly the consequence of electrostatic repulsion preventing the aggregation of ionized molecules. Also the nonionic surfactants (polydimethyl siloxane polyethers) showed some differences: the surfactant with polyethylene oxide side chain is more effective compared to the polyethylene-polypropylene oxide side chain.
The results of miscibility testing of silicone surfactants with common components of emulsions and creams confirm that not only silicone oils, but also silicone surfactants, should be considered as both explicitly hydrophobic and non lipophilic.
The stability of emulsions containing silicone surfactants prepared by cold emulsification supported the incorporation of polyelectrolyte sodium carboxymethylcellulose, which increased viscosity of the continuous phase and prevented coalescence.
The physical stability testing of prepared emulsions confirms that the used methods - centrifugation, particle size analysis and the observation of ageing at room (20–25°C) and elevated temperature (40°C) - give comparable results.     

Lipid and water crystallization in protein-stabilised oil-in-water emulsions

Phase and state transitions occurring during freezing and thawing of oil-in-water emulsions with different water phase formulations, interfacial compositions and two lipid types were studied as crucial factors affecting emulsion stability. Emulsions containing 0–40% (w/w) sucrose in the water phase at pH 7, and 10, 20, 30, 40% (w/w) dispersed lipid phase (sunflower oil, SO or hydrogenated palm kernel oil, HPKO) with whey protein isolate, WPI, or sodium caseinate, NaCAS, (protein:lipid = 1:10 and 2:10) as emulsifier were prepared. Phase/state behaviour of the continuous and dispersed phases was determined by differential scanning calorimetry (DSC). Emulsion stability and morphology were derived from DSC data, gravitational separation and particle size analysis during 4 freeze-thaw cycles. Systems were stable when only lipid crystallization occurred. DSC data showed that lipid crystallization prior to water crystallization (i.e. emulsions containing HPKO) caused destabilisation at low sucrose concentrations (0, 2.5 and 5% w/w). Emulsions were stable if the dispersed oil phase crystallized after the dispersing water phase (i.e. emulsions containing SO). A concentration of sucrose ≥10% (w/w) in the aqueous phase gave stable emulsions. At 10:1 lipid to protein ratio, WPI showed better stabilising properties than NaCAS at 2.5 and 5% (w/w) sucrose. Double concentration of WPI (lipid:protein = 10:2) at 0% (w/w) sucrose significantly improved systems stability, whereas no positive effect was observed when the concentration of NaCAS was increased. From morphology study, in addition to lipid destabilisation, thickening and flocculation caused instability of the systems. These were extensive in systems containing WPI and were ascribed to interactions between whey proteins during thermal cycling.     

多糖对蛋白质乳浊液稳定性影响机理研究

蛋白质乳浊液体系是食品中最重要体系之一,其稳定性问题一直是食品界研究热点,影响蛋白乳浊液稳定性因素很多;该文主要重点阐述不同多糖影响蛋白质乳浊液体系稳定性机理及多糖与蛋白质之间相互作用对蛋白质乳浊液体系稳定性影响。     

Phytosterol oxidation in oil-in-water emulsions and bulk oil

Dietary plants sterols (phytosterols) have been shown to lower plasma cholesterol level in humans. Since phytosterols may protect against coronary heart diseases, they are being incorporated into functional foods. However, phytosterols are susceptible to oxidative degradation. The purpose of this study was to evaluate the formation of phytosterols oxidation products (POPs) in oil-in-water emulsions and bulk corn oil. The extent of lipid oxidation was monitored by measuring the lipid hydroperoxides and hexanal, whereas 7-keto derivatives of phytosterols were determined by gas chromatography to follow sterol oxidation. A higher POPs level and formation rate was found in the oil-in-water (o/w) emulsion than in the bulk oil. Interfacial tension measurements showed that phytosterols had a high degree of surface activity, which would allow them to migrate to the oil–water interface of the emulsion droplets where oxidative stress is high.     

Application of pork fat diacylglycerols in meat emulsions

The properties of fat are of major importance when meat products are produced. By enzymatic modification triacylglycerols (TAGs) can be converted to diacylglycerols (DAGs) resulting in changes of the physical and chemical properties of the fat. In this study the texture as well as the hydration and binding properties were investigated in meat emulsions prepared with lard substituted with different amounts of DAGs derived from the lard. In emulsions prepared with DAGs the percentage of total expressible fluid decreased from 28.2% in products prepared with lard to 11.8% in emulsions prepared with 100% DAGs. The fat separation decreased from 10.9% to 7.8% when 10% of DAGs were applied and no fat separation was observed for emulsions prepared with 50% and 100% DAGs. Emulsions containing DAGs were more elastic and solid reflected in a significant increase in Young's modulus and the maximum hardness. The results suggest future opportunities for the application of DAGs to improve the quality of meat products.