Interfacial Properties and Emulsification of Biocompatible Liquid-Liquid Systems

Katarzyna Dziza,Francesca Ravera,Ewelina Jarek,Libero Liggieri,Eva Santini,Thilo Fischer,Marcel Krzan

doi:10.3390/coatings10040397

Abstract

A comparative study is reported on the interfacial properties of a set of surfactants and is discussed in terms of the effects on the features of the corresponding oil-water emulsions. The surfactants are saponin, Tween 80 and citronellol glucoside (CG), while the oil is Miglyol 812N—A Medium Chain Triglyceride (MCT) oil. Due to their high biocompatibility, all these compounds are variously utilized in food, cosmetic or pharmaceutical products. Among the surfactants, which are all soluble in water, CG presents also an important solubility in oil, as shown by the measured partition coefficient. For these systems, dynamic and equilibrium interfacial tensions and dilational viscoelasticity are measured as a function of the surfactant concentration and analyzed according to available adsorption models. In order to compare these results with the time evolution of the corresponding emulsions, the actual surfactant concentration in the matrix phase of the emulsion is accounted for. This may differ significantly from the nominal concentration of the solutions before dispersing them, because of the huge area of droplets available for surfactant adsorption in the emulsion. Using this approach allows the derivation of the correlations between the observed emulsion behavior and the actual surfactant coverage of the droplet interface.

Highlights

Emulsions in cosmetic, pharmaceutical and food industry rely on biocompatible formulations.Among the various ingredients, surfactants are needed to provide long term stability and suitable features to the emulsified products.Aiming at these applications and, more generally, to pursue the objectives related to green and sustainable development, surfactants derived from plant products are more and more utilized, in substitution of synthetic and even biocompatible molecules.The present paper addresses the interfacial properties and emulsification of water-oil system for two surfactants derived from vegetable sources, namely saponin and citronellol glucoside (CG) as compared to the classical biocompatible synthetic surfactant Tween 80.As the biocompatible oil phase the Medium Chain Triglyceride (MCT) oil is used
TheInterfacial interfacial tension of surfactant solutions against the MCT oil has been measured at various concentrations in water according to the method described in the previous section
We have investigated the properties of adsorption layers of different water-soluble biocompatible surfactants, namely Tween 80, saponin and citronellol glucoside at the interface between water and a Medium Chain Triglyceride oil, correlating them to the aging of corresponding emulsions

Summary

Introduction

Pharmaceutical and food industry rely on biocompatible formulations.Among the various ingredients, surfactants are needed to provide long term stability and suitable features (drop size and distribution, tactile and sensorial attributes, etc.) to the emulsified products.Aiming at these applications and, more generally, to pursue the objectives related to green and sustainable development, surfactants derived from plant products are more and more utilized, in substitution of synthetic and even biocompatible molecules.The present paper addresses the interfacial properties and emulsification of water-oil system for two surfactants derived from vegetable sources, namely saponin and citronellol glucoside (CG) as compared to the classical biocompatible synthetic surfactant Tween 80.As the biocompatible oil phase the Medium Chain Triglyceride (MCT) oil is used. The aging of emulsions is governed by various processes influenced by the bulk and adsorption properties of surfactants, both at equilibrium and in dynamic conditions These are creaming or sedimentation, which is the gravity-driven phase separation due to the density difference between the two liquids, Ostwald ripening and droplet coalescence [21]. The interfacial coverage is the relative area of the interface occupied by the surfactant High values of this parameter represent another stabilizing factor against coalescence due to the short range interactions of the surfactant molecules adsorbed at the two sides of the film between droplets. Steric effects are especially concerned with composite surface layers, such as surfactant-nanoparticle mixtures or surfactant aggregates and with large surfactant molecules at high adsorption coverage

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Discussion

Conclusion