Silicone oil emulsions: strategies to improve their stability and applications in hair care products

Silicone oils have wide range of applications in personal care products due to their unique properties of high lubricity, non‐toxicity, excessive spreading and film formation. They are usually employed in the form of emulsions due to their inert nature. Until now, different conventional emulsification techniques have been developed and applied to prepare silicone oil emulsions. The size and uniformity of emulsions showed important influence on stability of droplets, which further affect the application performance. Therefore, various strategies were developed to improve the stability as well as application performance of silicone oil emulsions. In this review, we highlight different factors influencing the stability of silicone oil emulsions and explain various strategies to overcome the stability problems. In addition, the silicone deposition on the surface of hair substrates and different approaches to increase their deposition are also discussed in detail.     

蛋白界面膜及其评价方法研究进展

食品中乳化类产品的稳定性决定了其价值和顾客满意度,天然蛋白的乳化特性多年来受到食品胶体和界面科学领域广泛关注。蛋白吸附到水油界面形成的黏弹性薄膜具有降低界面张力、维持乳液稳定的特性。研究蛋白界面膜的物化性质有助于了解蛋白大分子在水油界面的吸附规律,能够用于评价、表征和预测蛋白乳液稳定性,并为优化蛋白乳液稳定性提供理论基础。基于此,该文对水包油乳液蛋白界面膜结构和影响因素进行探讨,系统综述了目前用于评价蛋白质界面特性的手段和方法,包括微观成像技术、热力学技术、光谱技术和界面流变学技术等,以研究蛋白类乳化液性能在宏观和微观层面的联系,为蛋白质界面膜在乳化食品中的应用提供参考。     

Standardization of Nanoparticle Characterization: Methods for Testing Properties,Stability, and Functionality of Edible Nanoparticles

There has been a rapid increase in the fabrication of various kinds of edible nanoparticles for oral delivery of bioactive agents, such as those constructed from proteins, carbohydrates, lipids, and/or minerals. It is currently difficult to compare the relative advantages and disadvantages of different kinds of nanoparticle-based delivery systems because researchers use different analytical instruments and protocols to characterize them. In this paper, we briefly review the various analytical methods available for characterizing the properties of edible nanoparticles, such as composition, morphology, size, charge, physical state, and stability. This information is then used to propose a number of standardized protocols for characterizing nanoparticle properties, for evaluating their stability to environmental stresses, and for predicting their biological fate. Implementation of these protocols would facilitate comparison of the performance of nanoparticles under standardized conditions, which would facilitate the rational selection of nanoparticle-based delivery systems for different applications in the food, health care, and pharmaceutical industries.     

Surface activity, film formation, and emulsifying properties of milk proteins

This overview indicates that simple, reliable standardized methods for measuring emulsifying activity and for determining ES are not yet available. One of the major shortcomings of most of the current methods is the inability to detect very small fat globules (less than 0.5 micron), which may be very important in stable emulsions. Several of the methods are time consuming and destructive. To minimize the time required to evaluate emulsions, techniques that monitor instability under the influence of accelerated aging (increased temperature and gravitational field) have been used with varying degrees of success. These methods, e.g., centrifugation, are useful, but processes occurring during centrifugation or heating may not be characteristic of those occurring in a stored emulsion. Generally, there is no method that simultaneously determines changes in emulsions due to the aggregation coalescence, flocculation, creaming, of the droplets and/or oiling off. No single criterion of emulsion instability is sufficient to characterize all the changes occurring in the system. A nonintrusive technique that can monitor dynamic changes in emulsions is needed. Ideally, it should be simple, rapid, inexpensive, and applicable to both diluted and concentrated emulsions. Scientists must continue research to develop such a standard universal method for determining ES, because data from different laboratories cannot currently be validly compared. Reliable methods are also required to elucidate relationships between the physical properties of proteins as emulsifiers and their performance in food emulsions. There is a need for opportunities for systematic research to determine the interfacial behavior of food emulsifiers, particularly food proteins. Research to describe the kinetics and thermodynamics of adsorption at an interface, the extent of unfolding, the degree of packing and polypeptide interactions in an interface during film formation, and information concerning the physical and mechanical properties of interfacial films is needed to describe emulsifying behavior of different proteins. The effects of components in the continuous and discontinuous phase, parameters of manufacture, and interactions between different types of surface-active materials that occur in food need to be studied.     

大豆蛋白乳液的研究进展

食品乳液作为活性物质的传递体系一直是国内外的研究热点。大豆蛋白作为一种植物高分子蛋白质,具有独特的营养价值和良好的乳化性,在改善食品感官品质和提高乳液体系稳定性上具有显著的优势。由于双亲性和高表面活性,大豆蛋白乳液得到了迅速的发展,纳米乳液、微米乳液、多重乳液、Pickering乳液、多层乳液等新型乳液以及基于乳液的固体脂质颗粒、微胶囊化和水凝胶填充颗粒,在食品、保健品、化妆品等领域有着广泛的应用前景。本研究主要综述了大豆蛋白基本结构与功能特性的关系,阐明了大豆蛋白乳液的基本性质与制备方法,并对大豆蛋白乳液的应用以及未来的发展前景进行了展望,以期为大豆蛋白乳液的加工与应用提供参考。     

水包油型食品乳液中天然小分子乳化剂的功能性质及与其他乳化剂相互作用关系的研究进展

水包油型乳液是食品、保健品、药品等的重要成分,单一或复合乳化剂对水包油型乳液的形成、稳定性和功能性质有重要影响。如今消费者对健康和环境保护的关注促使食品生产者更倾向使用天然成分取代合成成分。本文综述在食品工业中具有潜在应用价值小分子天然乳化剂的理化性质,讨论其对乳液稳定性的影响以及在食品工业中的应用情况,并总结在乳液中使用复合乳化剂,尤其是磷脂与其他乳化剂相互作用的性质和机理;最后概括复合乳化剂对乳液功能性质的影响,包括抗氧化活性、抗菌活性和胃肠道消化特性。以期为开发乳液产品、选择乳化剂及其组合提供理论参考。     

水包油乳液中油脂氧化稳定性的研究进展

随着消费者对不饱和脂肪酸及其产品营养价值越来越重视,不饱和脂肪酸富集食品已经成为食品工业发展的趋势。水包油(oil-in-water,O/W)乳液是食品油脂最常见的存在形式,也是必需脂肪酸、脂溶性营养素和风味物质的有效载体。然而,富含不饱和脂肪酸的O/W乳液食品在加工和贮藏过程中极易氧化,引起风味恶化、营养损失,甚至形成威胁人类健康的有毒化合物。因此,如何提高乳液中油脂的氧化稳定性是食品工业中亟待解决的问题。然而,消费者对天然食品需求的提高,又限制了合成抗氧化剂和氢化等传统抗氧化方法的使用。本文综述了O/W乳液中油脂氧化的机制、影响因素和调控机制,重点概述了食品分散体中油-水界面的理化性质如何影响油脂氧化稳定性这一基础研究,为高稳定性乳液体系和新型功能食品的开发提供新思路和理论支持。     

Importance of bacterial surface properties to control the stability of emulsions

In colloidal media such as emulsions or food matrixes, the stability results from physicochemical interactions. The same type of interaction is involved in the attachment processes of microorganisms, through their surface properties, to interfaces. When bacteria are present in a food matrix, it is probable that their surface interacts with the other constituents. In this paper, the involvement of bacterial surface properties of Lactococcus lactis subsp lactis biovar diacetylactis (LLD) on the stability of model emulsions has been studied. The hydrophobic and electrostatic cell-surface properties were characterized by the MATH method and by microelectrophoresis, respectively. The oil-in-water emulsions were stabilized by various surface-active compounds, CTAB, SDS or Tween 20, giving differently charged droplets. Two strains with different surface characteristics were added to the emulsion. Contrasting with emulsions made with the non-ionic surfactant, for which the stability was not modified by the addition of bacteria, the emulsions made with ionic surface-active compounds were unstable in the presence of bacteria when the bacterial surface charge was opposite to the one of the emulsion droplets. Moreover, aggregation and flocculation phenomena were observed for emulsions stabilized with the cationic surfactant, particularly for more negatively charged bacteria. The effect of bacteria on the emulsion stability depended on the strain which shows the importance of the choice of the microorganism according to of the characteristics of the colloidal media to obtain a stable system. In addition, these results suggest that the interactions between bacteria and other food components can influence the position of bacteria in food matrixes.     

The choice of homogenisation equipment affects lipid oxidation in emulsions

Milk proteins are often used by the food industry because of their good emulsifying properties. In addition, they can also provide oxidative stability to foods. However, different milk proteins or protein components have been shown to differ in their antioxidative properties, and their localisation in emulsions has been shown to be affected by the emulsification conditions. The objective of this study was to investigate the influence of homogenisation equipment (microfluidizer vs. two-stage valve homogeniser) on lipid oxidation in 10% fish oil-in-water emulsions prepared with two different milk proteins. Emulsions were prepared at pH 7 with similar droplet sizes. Results showed that the oxidative stability of emulsions prepared with sodium caseinate was not influenced by the type of homogeniser used. In contrast, the type of homogenisation equipment significantly influenced lipid oxidation when whey protein was used as emulsifier, with the microfluidizer resulting in lower levels of oxidation.     

Encapsulation systems for lutein: A review

BackgroundThe increased demand by consumers for clean labels has encouraged industry to search for replacements of synthetic ingredients in food products, and in particular, colorants. Lutein, a xanthophyll found in marigolds and corn, can be used in food products as a natural colorant replacing yellow food dyes. Moreover, lutein is considered a nutraceutical due to its potentially beneficial health effects, such as prevention of macular degeneration, role in the development of the visual and nervous systems of fetuses, and its antioxidant properties. However, incorporation of lutein into foods is often limited because of its low-water solubility, chemical instability, and poor oral bioavailability. For this reason, colloidal encapsulation systems have been developed to facilitate the incorporation of lutein into aqueous food and beverage products.Scope and approachThis review focuses on exploring encapsulation options for lutein using various emulsion-based, nanoparticle- and microparticle-based and molecular inclusion encapsulation systems, as well as additives that can be used to increase its chemical stability in these systems. This review covers all aspects of lutein encapsulation, including both food-grade and pharmaceutical-grade encapsulation systems.Key findings and conclusionsThough lutein-loaded encapsulation systems are extensively explored in this review, emulsions are of the most interest in industry as they are cost efficient and can be designed to increase the stability of lutein by selecting the proper emulsifiers and emulsification techniques. Despite the extensive amount of research carried out on the encapsulation of hydrophobic bioactive molecules such as lutein, there are still opportunities to develop encapsulation systems that further protect these molecules during storage and also increase their bioavailability after ingestion.     

Nanoemulsions: Synthesis,Characterization, and Application in Bio‐Based Active Food Packaging

The increasing demands for foods with fresh‐like characteristics, lower synthetic additive and preservative contents, and low environmental footprint, but still safe to consume, have guided researchers and industries toward the development of milder processing technologies and more eco‐friendly packaging solutions. As sustainability acquires an increasingly critical relevance in food packaging, bio‐based and/or biodegradable materials stand out as suitable alternatives to their synthetic counterparts. In this context, the use of nanoemulsions has represented a step forward for improving the performance of sustainable food packaging devices, especially for the successful incorporation of new compounds and functionalities into conventional films and coatings. This class of emulsions, featuring unique optical stability and rheological properties, has been developed to protect, encapsulate, and deliver hydrophobic bioactive and functional compounds, including natural preservatives (such as essential oils from plants), nutraceuticals, vitamins, colors, and flavors. This article presents the surfactants (including naturally occurring proteins and carbohydrates), dispersants, and oil‐soluble functional compounds used for designing food‐grade nanoemulsions intended for packaging applications. The improved kinetic stability, bioavailability, and optical transparency of nanoemulsions over conventional emulsions are discussed considering theoretical concepts and real experiments. Bottom‐up and top‐down approaches of nanoemulsion fabrication are described, including high‐energy (such as high‐pressure homogenizers, microfluidics, ultrasound, and high‐speed devices) and low‐energy methods (for instance, phase inversion and spontaneous emulsification). Finally, incorporation of nanoemulsions in biopolymer matrixes intended for food packaging applications is also addressed, considering current characterization techniques as well as their potential antimicrobial activity against foodborne pathogens.     

Oxidation and oxidative stability in emulsions

Emulsions are implemented in the fabrication of a wide array of foods and therefore are of great importance in food science. However, the application of emulsions in food production is restricted by two main obstacles, that is, physical and oxidative stability. The former has been comprehensively reviewed somewhere else, but our literature review indicated that there is a prominent ground for reviewing the latter across all kinds of emulsions. Therefore, the present study was formulated in order to review oxidation and oxidative stability in emulsions. In doing so, different measures to render oxidative stability to emulsions are reviewed after introducing lipid oxidation reactions and methods to measure lipid oxidation. These strategies are scrutinized in four main categories, namely storage conditions, emulsifiers, optimization of production methods, and antioxidants. Afterward, oxidation in all types of emulsions, including conventional ones (oil-in-water and water-in-oil) and uncommon emulsions in food production (oil-in-oil), is reviewed. Furthermore, the oxidation and oxidative stability of multiple emulsions, nanoemulsions, and Pickering emulsions are taken into account. Finally, oxidative processes across different parent and food emulsions were explained taking a comparative approach.     

Phytic Acid as a Food Antioxidant

Phytic acid has been shown previously to form an iron chelate that inhibits iron-catalyzed hydroxyl radical formation and lipid peroxidation. To further characterize its antioxidant properties in model food systems, we investigated the effects of phytic acid on ascorbic acid degradation in aqueous solution and on stability of oil-in-water emulsions. In both systems 1 mM phytic acid provided significant protection against oxidative damage and increased emulsion shelf-life fourfold. To test antioxidant efficacy of phytic acid in a whole food system, its effect on development of warmed-over flavor was determined. Phytic acid substantially inhibited oxygen uptake, malondialdehyde formation and warmed-over flavor development in refrigerated chicken.     

纤维素稳定Pickering乳液的研究进展及在食品领域的应用

纤维素作为一种可再生资源,具有来源广泛、绿色环保、可生物降解性、生物相容性等优点。研究发现,由固体颗粒作为稳定剂制备的乳液较传统表面活性剂稳定的乳液具有更高的稳定性,而纤维素凭借其生物相容性、来源广、绿色环保等优点,成为一种良好的Pickering乳液稳定剂,同时纤维素作为一种天然的可食用膳食纤维,在食品领域中具有广阔的应用前景。本文综述不同种类纤维素稳定Pickering乳液的特点,介绍不同处理方式赋予纳米纤维素稳定Pickering乳液不同的性能,并对纳米纤维素基乳液在制备食品级高分子材料、制备新型低热量食品、输送生物活性物质及辅助消化等食品领域的应用进行叙述,为拓宽纤维素基Pickering乳液应用提供参考。     

An overview of analytical methods for determining the geographical origin of food products

There is an increasing interest by consumers for high quality food products with a clear geographical origin. These products are encouraged and suitable analytical techniques are needed for the quality control. This overview concerns an investigation of the current analytical techniques that are being used for the determination of the geographical origin of food products. The analytical approaches have been subdivided into four groups; mass spectrometry techniques, spectroscopic techniques, separation techniques, and other techniques. The principles of the techniques together with their advantages and drawbacks, and reported applications concerning geographical authenticity are discussed. A combination of methods analysing different types of food compounds seems to be the most promising approach to establish the geographical origin. Chemometric analysis of the data provided by the analytical instruments is needed for such a multifactorial approach.     

Protein‐stabilized foams and emulsions

This review is a survey of studies on protein‐stabilized foams and emulsions in relatively simple, well‐defined systems (rather than in food products per se). The emphasis is on the extent of basic understanding developed, particularly in terms of the physicochemical properties involved. The stability of the system, its formation, and its rheology are covered. Unfortunately, much work is of limited fundamental value because of poorly designed experimental approaches and the failure to measure key parameters. Reasonable generalizations can be made concerning the effects of a number of variables, particularly protein solubility, pH, protein structure and the presence of small molecule surfactants. However, several possible explanations of these effects in terms of surface properties remain tenable. A number of observations can fairly confidently be ascribed to the influence of rheology on flow processes within foams and emulsions.     

Effects of composition and processing variables on the oxidative stability of protein-based and oil-in-water food emulsions

Because many common foods are emulsions (mayonnaise, coffee creamers, salad dressing, etc.), a better understanding of lipid oxidation mechanisms in these systems is crucial for the formulation, production, and storage of the relevant consumer products. A research body has focused on the microstructural and oxidative stability of protein-stabilized oil-in-water emulsions that are structurally similar to innovative products that have been recently developed by the food industry (e.g., non-dairy creams, vegetable fat spreads, etc.) This review presents recent findings about the factors that determine the development of lipid oxidation in emulsions where proteins constitute the stabilizing interface. Emphasis is given to “endogenous” factors, such as those of compositional (e.g., protein/lipid phases, pH, presence of transition metals) or processing (e.g., temperature, droplet size) nature. Improved knowledge of the conditions that favor the oxidative protection of protein in emulsions can lead to their optimized use as food ingredients and thereby improve the organoleptic and nutritional value of the related products.     

Emulsion design for the delivery of β-carotene in complex food systems

β-Carotene has been widely investigated both in the industry and academia, due to its unique bioactive attributes as an antioxidant and pro-vitamin A. Many attempts were made to design delivery systems for β-carotene to improve its dispersant state and chemical stability, and finally to enhance the functionality. Different types of oil-in-water emulsions were proved to be effective delivery systems for lipophilic bioactive ingredients, and intensive studies were performed on β-carotene emulsions in the last decade. Emulsions are thermodynamically unstable, and emulsions with intact structures are preferable in delivering β-carotene during processing and storage. β-Carotene in emulsions with smaller particle size has poor stability, and protein-type emulsifiers and additional antioxidants are effective in protecting β-carotene from degradation. Recent development in the design of protein-polyphenol conjugates has provided a novel approach to improve the stability of β-carotene emulsions. When β-carotene is consumed, its bioaccessibility is highly influenced by the digestion of lipids, and β-carotene in smaller oil droplets containing long-chain fatty acids has a higher bioaccessibility. In order to better deliver β-carotene in complex food products, some novel emulsions with tailor-made structures have been developed, e.g., multilayer emulsions, solid lipid particles, Pickering emulsions. This review summarizes the updated understanding of emulsion-based delivery systems for β-carotene, and how emulsions can be better designed to fulfill the benefits of β-carotene in functional foods.     

Effect of processing conditions and composition on sodium caseinate emulsions stability

Many food products such as ice cream, yoghurt, and mayonnaise are some examples of emulsion-based food. The physicochemical properties of emulsions play an important role in food systems as they directly contribute to texture, sensory and nutritional properties of food. One of the main properties is stability which refers to the ability of an emulsion to resist physical changes over time. The aim of the present work was to analyze the effect of processing conditions and composition on sodium caseinate (NaCas) emulsions stability. The main destabilization mechanisms were identified and quantified. The relationship between them and the factors that influence them were also investigated. Emulsions stabilized with NaCas were prepared using an ultrasound liquid processor or a high pressure homogenizer. Stability of emulsions was followed by a Turbiscan (TMA 2000) which allows the optical characterization of any type of dispersion. The physical evolution of this process is followed without disturbing the original system and with good accuracy and reproducibility. To further describe systems, droplet size distribution was analyzed with light scattering equipment. The main mechanism of destabilization in a given formulation depended on different factors such as NaCas concentration, droplet size or processing conditions. The rate of destabilization was markedly lower with addition of sugar or a hydrocolloid to the aqueous phase. Xanthan (XG) and locust bean (LBG) gums produced an increase in viscosity of the continuous phase and structural changes in emulsions such as gelation. Sugars interacted with the protein decreasing particle size and increasing emulsion stability. The stability of caseinate emulsions was strongly affected not only by the oil-to-protein ratio but also by processing conditions and composition of aqueous phase. The structure of the protein and the interactions protein–sugar or the presence of a hydrocolloid played a key role in creaming and flocculation processes of these emulsions.     

Characterisation of emulsion properties and of interface composition in O/W emulsions prepared with hen egg yolk, plasma and granules

Comprehension of hen egg yolk emulsifying properties remains incomplete because competition between its various emulsifiers (proteins and lipoproteins containing phospholipids) has not been clearly elucidated and colloidal interactions between yolk-stabilised oil droplets have not been documented. Recent studies emphasised the interest of the fractionation of yolk into plasma and granules to improve this comprehension. In the present study, we characterised, concurrently, emulsion properties (oil droplet size and stability against creaming) and interface attributes (interfacial concentrations of proteins and phospholipids, SDS-PAGE profiles of adsorbed proteins and zeta potential) in oil-in-water (O/W) emulsions prepared with yolk, plasma and granules. We observed these features at four physicochemical conditions (pH 3.0 or 7.0 and at 0.15 or 0.55 M NaCl). Emulsion properties in emulsions made with yolk or plasma varied similarly as a function of pH and NaCl concentration whereas granules emulsions exhibited distinct properties. Therefore the main contributors to yolk emulsifying properties are to be sought for among plasma constituents (proteinaceous or phospholipids). Since, in plasma emulsions, variations of emulsion stability against creaming correlated exclusively to variations of protein interfacial concentration, a driving contribution of the proteinaceous part of plasma, namely apo-LDL, was hypothesised. In the pH and ionic strength ranges studied, zeta potentials of the interfaces were low, excluding extended electrostatic repulsion between oil droplets. We deduced that steric repulsion is the main interaction opposing to droplet aggregation in food emulsions made with yolk.