Preparation Of Stable Emulsions Research Articles

Rheological Characterization and Quality of Emulsions Based on Fats Produced during the Reaction Catalyzed by Immobilized Lipase from Rhizomucor Miehei

It has been shown that structured lipids, formed in the process of enzymatic modification of natural hard fat with walnut oil, are capable of stabilizing emulsion systems without the need to add additional emulsifiers. This is especially true for emulsions containing fat formed during enzymatic modification when the amount of added water to the reaction catalyst was in the range of 12–16 wt%. Physicochemical evaluations, i.e., the average particle size, its growth, distribution, and dispersity coefficient, were comparable with the reference emulsion where the emulsifier was lecithin, well-known for its emulsifying properties. Microstructure studies also confirmed the above observations. Rheological studies performed on a set of emulsions containing structured lipids of variable composition confirmed that interesterified lipid blends can be directly utilized as a fat base in the preparation of stable emulsions. The consistency, thixotropic behavior, long-term shelf life, and thermal stability of these emulsions were found to be comparable to systems stabilized with conventional emulsifiers, i.e., sunflower lecithine. Our approach offers the opportunity for the preparation of stable emulsion systems, free from additional emulsifiers, for the food or cosmetics industry, which is extremely important from the point of view of the preparation of products free from allergens.

Assessment of the applicability of HLB values for natural phospholipid emulsifiers for preparation of stable emulsions.

Natural phospholipid (PL) excipients are native, biocompatible and relatively inexpensive alternatives to synthetic emulsifiers. A well-known PL excipient is lecithin, which primarily contains phosphatidylcholine (PC) and (depending on the purity grade) also contains a well-defined mixture of other PLs with a fatty acid composition, which reflects their natural source. Since all of these lipid species are emulsifiers, natural PLs can be considered as a mixture of (co-) emulsifiers. Many different HLB values for lecithins are given in the literature, which is why this needs to be clarified. To assess this, HLB values of thirteen different plant derived PLs differing in PC content were determined using a centrifugation stress method to determine the relative stability of an emulsion with the respective emulsifier and different oil phases. It could be shown that the studied PLs can be characterized by a broad HLB range, which may be linked to the composition of the PLs and the oil used. In order to emphasize the results of the HLB determination, it could be demonstrated that stable emulsions could be prepared with a wide range of oils using the plant-based PLs and that the preparation method of the emulsions is important in order to obtain stable emulsions. Therefore, assigning a specific exact HLB value to natural PLs instead of a wider range is inappropriate. The broad HLB ranges indicate the suitability of the studied PL emulsifiers for the preparation of oil-in-water emulsions for a wide range of oils: It is recommended to experimentally evaluate the suitability of these natural emulsifiers for the preparation of stable emulsions and to benefit from the wide range of HLB values of these emulsifiers instead of relying on inaccurate and confusing HLB values in the literature.

Improving the emulsion stability by regulation of dilational rheology properties

Considering the importance of interfacial film in determining emulsion stability, it is of great significance to reveal the relationship between the emulsion stability and rheology properties. Herein, we first investigated the dilational rheology properties of the imidazolium Gemini surfactants ([Cn+2-3-Cn+2im]Cl2) by the oscillating drop method, and the [C14-3-C14im]Cl2 was selected as the emulsifier due to its excellent rheology properties. Based on the rheology results, [C14-3-C14im]Cl2 was further complexed with Brij®S10 in the decane to prepare a series of O/W emulsions through the inversed phase emulsification method. Subsequently, the stabilities of these emulsions were systemically characterized, including the droplet diameter, polydispersity index, demulsification test and long term stability. After careful evaluation of the rheology properties and the emulsion stability, the relationship between them was revealed, which was the larger the dilational modulus is, the better the emulsion stability will be. This phenomenon was further explained by the variation trend of droplet radius with time. Moreover, a thick interfacial film with large dilational modulus would lead to the decrease of the Ostwald ripening rate, coalescence rate, and creaming rate, finally resulting in the increase of the emulsion stability. These findings will further provide guidelines for the selection of surfactants and the preparation of stable emulsions.

Preparation of stable emulsion using sodium surfactin in D phase emulsification method

Preparation of stable emulsion using sodium surfactin in D phase emulsification method

Chitosan-coated alginate-polyvinyl alcohol beads for encapsulation of silicone oil containing pyrene: a novel method for biodegradation of polycyclic aromatic hydrocarbons

BACKGROUND: Polycyclic aromatic hydrocarbons (PAHs) are potential hazards in the environment owing to their toxic, carcinogenic and recalcitrant nature. Biodegradation of these compounds, although effective compared with other treatment techniques, is problematic owing to its low aqueous solubility and negligible bioavailability. The present study reports a novel method for biodegradation of PAHs using an encapsulated form of the pollutant in chitosan-coated alginate–polyvinyl alcohol (PVA) beads. RESULTS: A suitable combination of 3% (w/v) PVA, 100 g L−1 non-ionic surfactant Brij 30 and 0.3 silicone oil fraction in the formulation was found to be optimal in the preparation of stable emulsion. The emulsion obtained was admixed with alginate (3% w/v) to prepare suitably sized microspheres by an emulsion gelation technique, which were later coated with chitosan to yield a maximum pyrene encapsulation efficiency of 90.7%. Pyrene in silicone oil at concentration as high as 2 g L−1, when delivered through the chitosan coated alginate–PVA beads, was completely degraded by Mycobacterium frederiksbergense within 10 days without any significant lag phase. CONCLUSION: Using chitosan-coated alginate–PVA beads sustained release of pyrene and subsequent biodegradation by M. frederiksbergense were achieved. Using the present system, complete degradation of pyrene was attained even at its very high initial concentration and within a short time period. Further advantage offered by this system seems to be negligible toxic effect of pyrene and solvents on the degrading microorganisms since these were in an encapsulated form and were not in direct contact with the organism. Copyright © 2010 Society of Chemical Industry

Nanoparticle silica-stabilised oil-in-water emulsions: improving emulsion stability

The rapid phase separation of oil-in-water (o/w) emulsions prepared from non-polar oil and alkaline dispersions of hydrophilic silica nanoparticles alone is described. A study of the roles of the surface chemistry of the particles and the type and composition of the oil and aqueous phases in improving the stability of these emulsions is then reported. Alteration of the particle charge and flocculation by control of pH and addition of divalent electrolyte causes temporary improvements in emulsion stability, while the addition of cationic surfactant results in the preparation of stable emulsions. Increasing the oil phase polarity is found to improve emulsion stability and this is attributed to adsorption of polar solvent molecules to the silica surface changing the particle wettability. Attempts to reduce the affinity of the particles for the aqueous phase by adding non-aqueous solvents to that phase are unsuccessful, perhaps due to the extreme hydrophilicity of the particles. For the stable emulsions, the effect of silica particle size on the emulsion drop size is also investigated.