pubs.acs.org/JAFC Published on Web 06/14/2010 © 2010 American Chemical Society 7762 J. Agric. Food Chem. 2010, 58, 7762–7769 DOI:10.1021/jf100917w Influence of Ionic Complexation on Release Rate Profiles from Multiple Water-in-Oil-in-Water (W/O/W) Emulsions MARIE BONNET, † MAUD CANSELL,* ,† FRE ´ DE ´ RIC PLACIN, † ELISABETH DAVID-BRIAND, § MARC ANTON, § AND FERNANDO LEAL-CALDERON † † Universite´ Bordeaux 1, TREFLE UMR CNRS 8508, ENSCBP, 16 avenue Pey Berland, 33607 Pessac, France, and § UR1268 Biopolym eres Interactions Assemblages, Equipe Interfaces et Syst emes Disperse´s, INRA, 44360 Nantes Cedex 3, France Water-in-oil-in-water (W/O/W) double emulsions were prepared, and the kinetics of release of magnesium ions from the internal to the external water phase was followed. Different chelating agents (phosvitin and gluconate) were used to bind magnesium within the prospect of improving the ion retention in the internal aqueous droplets. Magnesium release was monitored for 1 month of storage, for each formulation, with and without chelation, at two storage temperatures (4 and 25 °C). Leakage occurred without film rupturing (coalescence) and was mainly due to entropically driven diffusion/permeation phenomena. The experimental results revealed a clear correlation between the effectiveness of chelating agents to delay the delivery and their binding capacity characterized by the equilibrium affinity constant. The kinetic data (percent released versus time curves) were interpreted within the framework of a kinetic model based on diffusion and taking into account magnesium chelation. KEYWORDS: W/O/W emulsions; sustained release; chelating agent; release mechanisms; diffusion/ permeation INTRODUCTION Recently, there has been increasing interest in the development of multiple or double emulsions, for example, water-in-oil-in- water (W/O/W) and oil-in-water-in-oil (O/W/O). W/O/W emul- sions consist of small water droplets dispersed in larger oil globules, which are themselves dispersed in an aqueous contin- uous phase. Numerous studies have shown that W/O/W emul- sions provide a high capacity of entrapment and protection of the encapsulated species toward degradation. The compartmented structure allows the introduction of incompatible substances into the same system and subsequent sustained release ( 1 -8 ). Because of their encapsulation and protection efficiency, W/O/W emul- sions are potentially suitable materials for applications in various domains such as cosmetics, pharmaceutics, and foods. In this latter domain, double emulsions provide a number of potential benefits over conventional emulsions, such as reduction of fat content ( 9 ), taste masking, and protection of labile ingredients or sensitive probiotics ( 8 ). Double emulsions of the W/O/W type are generally stabilized by a couple of surface-active species following the empirical Bancroft rule: one is water-soluble to stabilize the oil globules in water and the other is oil-soluble to stabilize the internal aqueous droplets dispersed in oil. Nevertheless, there have been many difficulties associated with preparing this type of multiple emulsion with sufficient stability for commercial utiliza- tion, due to coalescence or due to diffusion of water molecules and of the whole set of hydrophilic solutes from the internal aqueous phase to the bulk aqueous phase or vice versa ( 10 ). During years of investigations to improve stability and to control sustained release of active species, short surfactant molecules have been progressively replaced by polymeric emulsifiers. Poly- meric amphiphilic molecules, synthetic or naturally occurring ones, are known to impart better emulsion stability, to ensure better encapsulation and controlled release of the encapsulated species than low molecular weight surfactants ( 11 -15 ). In this paper, we addressed a common issue that arises with potential uses of double emulsions: achieving sufficient stability for commercial applications. This issue is relevant in all of the sectors that may potentially use double emulsions (food industry, pharmacy, and cosmetics). The main objective of the present study was to develop a novel strategy based on the complexation (chelation) of ionic encapsulated species to improve retention in W/O/W emulsions. Magnesium (Mg 2þ ) was used not only as a model species to probe the release mechanism but also as a valuable compound for food supplementation. Indeed, magne- sium plays a role as a physiologic modulator affecting muscular contraction, cardiovascular function, and nerve impulse trans- mission. Due to a change in nutrition habits, the daily intake in magnesium is lower than the recommended value. Thus, magne- sium supplementation of food could be an alternative to prevent magnesium deficiency and its clinical disorders, for example, hypertension, cardiovascular diseases, muscular weakness, and diarrhea. However, magnesium addition in foods can induce chemical degradations and protein aggregation and generate an unpleasant taste. These drawbacks could be avoided or at least reduced by encapsulation. In recent studies, we have studied the *Author to whom correspondence should be addressed [phone 33 (0)5 40 00 38 19; fax 33 (0)5 56 37 03 36; e-mail mcansell@enscbp.fr].