Influence of Phase Inversion on the Formation and Stability of One-Step Multiple Emulsions

Abstract

A novel method of preparation of water-in-oil-in-micelle-containing water (W/O/W(m)) multiple emulsions using the one-step emulsification method is reported. These multiple emulsions were normal (not temporary) and stable over a 60 day test period. Previously, reported multiple emulsion by the one-step method were abnormal systems that formed at the inversion point of simple emulsion (where there is an incompatibility in the Ostwald and Bancroft theories, and typically these are O/W/O systems). Pseudoternary phase diagrams and bidimensional process-composition (phase inversion) maps were constructed to assist in process and composition optimization. The surfactants used were PEG40 hydrogenated castor oil and sorbitan oleate, and mineral and vegetables oils were investigated. Physicochemical characterization studies showed experimentally, for the first time, the significance of the ultralow surface tension point on multiple emulsion formation by one-step via phase inversion processes. Although the significance of ultralow surface tension has been speculated previously, to the best of our knowledge, this is the first experimental confirmation. The multiple emulsion system reported here was dependent not only upon the emulsification temperature, but also upon the component ratios, therefore both the emulsion phase inversion and the phase inversion temperature were considered to fully explain their formation. Accordingly, it is hypothesized that the formation of these normal multiple emulsions is not a result of a temporary incompatibility (at the inversion point) during simple emulsion preparation, as previously reported. Rather, these normal W/O/W(m) emulsions are a result of the simultaneous occurrence of catastrophic and transitional phase inversion processes. The formation of the primary emulsions (W/O) is in accordance with the Ostwald theory ,and the formation of the multiple emulsions (W/O/W(m)) is in agreement with the Bancroft theory.

Preparation and evaluation of water-in-soybean oil–in-water emulsions by repeated premix membrane emulsification method using cellulose acetate membrane

“…Two-step emulsification methods are involved to prepare multiple emulsions. A simple emulsion (W/O or O/ W) is produced, and then re-emulsified to form W/O/W and O/W/O emulsions, respectively (Morais et al 2009). Typically, the primary emulsion is formed by exerting a high shear homogenization process to produce fine internal droplet.…”

Stability and rheology of W/Si/W multiple emulsions with polydimethylsiloxane

“…Multiple emulsions can be prepared by either a two-step procedure or a single-step procedure [12][13][14][15][16][17]. Two-step is a common method to prepare double emulsion, in the first step, a primary emulsion (O/W or W/O) is prepared, and in the second step, the primary emulsion (O/W or W/O) is re-emulsified in either an oil solution containing a low HLB surfactant to produce an O/W/O double emulsion or an aqueous solution with a high HLB surfactant to produce a W/O/W double emulsion [12,13].…”

Produção por método da temperatura de inversão de fases, estudo de estabilidade físico-química, digestabilidade in vitro e citotoxicidade de nanopartículas lipídicas sólidas encapsulando beta-caroteno

“…Nos métodos de baixa energia, as nanoemulsões podem ser formadas com a perturbação de uma dispersão líquido/líquido, em que a fase contínua se torna a fase dispersa e vice-versa, ou seja, há uma transição de fase no sistema (MORAIS et al, 2009;. A fase que se destina a ser a fase contínua é adicionada à fase dispersa, até que ocorra a inversão de fase e a formação do tipo de emulsão desejada (SAJJADI, 2006).…”

“…A fase que se destina a ser a fase contínua é adicionada à fase dispersa, até que ocorra a inversão de fase e a formação do tipo de emulsão desejada (SAJJADI, 2006). Esta transição de fase resulta da mudança da razão entre a área ocupada pela porção hidrofílica e pela porção hidrofóbica do tensoativo, ou das rupturas interfaciais que ocorrem quando dois líquidos parcialmente miscíveis são misturados e um dos componentes se movimenta de uma fase para outra SADTLER et al, 2010;MEI et al, 2011A;MEI et al, 2011b (IZQUIERDO et al, 2002;MORALES et al, 2006; SAULNIER, 2008;MORAIS et al, 2009;JAHANZAD et al, 2010).…”

“…Por exemplo, em uma adição sucessiva de água em óleo, as gotículas de água são inicialmente formadas na fase oleosa contínua. No entanto, uma vez atingido o valor crítico da fase aquosa, há a migração do tensoativo desta fase para a fase oleosa, e desta forma ocorre uma mudança espontânea na curvatura interfacial, que é conduzida pela formação de estruturas intermediárias, denominadas fase lamelar e/ou bicontinua (FERNANDEZ et al, 2004;MORAIS et al, 2009;MCCLEMETS;RAO 2011). Quanto maior a concentração de tensoativo, melhor será a formação de tais estruturas, e melhor também a formação das gotículas pequenas de óleo (FERNANDEZ et al, 2004).…”