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In the present study, the influence of perfumes on the interfacial curvature of microemulsions is investigated. The hydrophilic-lipophilic deviation (HLD) concept was applied to nonionic Winsor I type systems (O/W microemulsions in equilibrium with an oil excess phase) containing a mixture of oils with isopropyl myristate as supporting oil and a variety of liquid solutes as co-oil for which an Equivalent Alkane Carbon Number of the mixture (EACN mix ) was defined. Temperature was used as a formulation variable and the phase inversion temperature change, provoked by the solubilization of different solutes, was determined. The hydrodynamic radius of the droplet and the interfacial solubilization of fragrances were measured subsequently and correlated to the EACN mix . In a first step, selected perfumery raw materials (PRMs) were used as solutes and were studied separately. It was demonstrated that the PRMs can be classified in interfacial solubility according to their chemical functionalities and they follow the order alcohols [ aldehydes [ terpenes [ aromatics [ alkanes. Solutes that lead to low EACN mix values (\6) have preferential interfacial solubility and provoke strong curvature changes, whereas those leading to higher EACN values ([6) typically do not change the curvature significantly. The HLD method was also applied to complex fragrances and it was demonstrated that they can be considered as single, non-polar entities, and studied as such instead of investigating each raw material included in the composition separately. Determination of the dimensionless number EACN mix offers the possibility of classifying perfumes in an environment similar to surfactant formulations of typical consumer products and to predict the interaction with the surfactant base according to the rules established on the basis of the individual raw materials.

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Despite their intrinsic hydrolysable character, imine bonds can become remarkably stable in water when selfassembled in amphiphilic micellar structures. In this work, we systematically studied some of these structures and the influence of various parameters that can be used to take control of their hydrolysis, including pH, concentration, the position of the imine function in the amphiphilic structure, relative lengths of the linked hydrophilic and hydrophobic moieties. Thermodynamic and kinetic data led us to the rational design of stable imines in water, partly based on the location of the imine function within the hydrophobic part of the amphiphile and on a predictable quantitative term that we define as the total hydrophilic-lipophilic balance (HLB). In addition, we show that such stable systems are also stimuliresponsive and therefore, of potential interest in trapping and releasing micellar components on demand.

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Amphiphilic imines prepared by condensation of a hydrophobic fragrance aldehyde with a hydrophilic amine derived from a poly(propylene oxide) and poly(ethylene oxide) diblock copolymer were investigated as cleavable surfactant profragrances in applications of functional perfumery. In water, the cleavable surfactants assemble into micelles that allow solubilization of perfume molecules that are not covalently attached to the surfactant. Dynamic headspace analysis on a glass surface showed that solubilized perfume molecules evaporated in a similar manner in the presence of the cleavable surfactant as compared with a non-cleavable reference surfactant. Under application conditions, the cleavable surfactant imine hydrolysed to release the covalently linked fragrance aldehyde. The profragrances were stable during storage in aqueous media, and upon dilution showed a blooming effect for the hydrolytical fragrance release and a more balanced performance of a solubilized perfume by retaining the more volatile fragrances and boosting the evaporation of the less volatile fragrances.

Microemulsions stabilized by sucrose esters in combination with lecithin are interesting flavour delivery systems because they allow the solubilization of very high levels of oil into an aqueous phase with relatively small amounts of surfactants. The aim of this study was to investigate microemulsions stabilized by these surfactants in order to determine the microemulsion type and the solubilizing capacity of the structures. Based on these results a good control and easy handling of the delivery systems is feasible. Pulsed Field Gradient (PFG) diffusion nuclear magnetic resonance spectroscopy revealed that at some specific ratios between both surfactants the formation of bicontinuous microemulsions takes place. In such systems, between 20% and 60% of the oil phase can be solubilized. The solubilization of lecithin in the flavour oil and the insertion of this mixture into a system containing direct micelles of sucrose ester changes the curvature of structures and allows the continuous transition from direct oil/water to bicontinuous structures to inverse water/oil microemulsions. In such inverse microemulsions up to 80% of flavour oil can be solubilized. Our investigation demonstrates that the presence of lecithin leads to an increase of the flavour oil loading, decreasing significantly the total surfactant concentration. Therefore, lecithin can be used as a tuning parameter to control the different types of microemulsions without additional hydrotropes and they can be easily adapted to different industrial applications. Copyright © 2013 John Wiley & Sons, Ltd.

Cooling agents are small organic molecules known to evoke a sensation of cold by interaction with the transient receptor. In the present study, we demonstrate experimentally that some cooling agents could behave as hydrotropes in aqueous solutions in the absence of surfactants, and also as co‐surfactants/co‐solvents in aqueous solutions in the presence of a surfactant forming an interfacial film. The hydrotropy and co‐surfactancy/co‐solvency effect depends strongly on the type of perfumery ingredient. The hydrotrope concentration, the concentration at which the water solubility of the perfumery compound is enhanced, is surprisingly low, in the mmol/L range.