Improved Oil Solubilization in Oil/Water Food Grade Microemulsions in the Presence of Polyols and Ethanol

Abstract

Microemulsions based on five-component mixtures for food applications and improved oil solubilization have been studied. The compositions included water, oil phase [such as R(+)-limonene and medium-chain triglycerides (MCT)], short-chain alcohols (such as ethanol), polyols (propylene glycol and glycerol), and several surfactants and their corresponding mixtures (nonionic, such as ethoxylated sorbitan esters, polyglycerol esters, sugar ester, and anionic, such as phosphatidylcholine). The phase behavior of these systems is discussed with respect to the influence of polyols and short-chain alcohols on the degree of solubilization of oils in the aqueous phase. The alcohol and polyols modify the interfacial spontaneous curvature and the flexibility of the surfactant film, enhancing the oil solubilization capacity of the microemulsions. The solubilization of R(+)-limonene was dramatically improved in the presence of the alcohol and polyols, whereas the improvement of solubilization for triglycerides containing MCT was less pronounced. In some systems high oil solubilization was achieved, and some of them can be easily diluted to infinity both with the aqueous phase and with the oil phase. Viscosity measurements along selected dilution lines [characterized by a single continuous microemulsion region starting from a pseudo binary solution (surfactant/oil phase) to the microemulsion (water/polyol corner)] indicate that at a certain composition the system inverts from a W/O to an O/W microemulsion.

Factors Affecting the Phase Behavior and Antimicrobial Activity of Carvacrol Microemulsions

“…Fortunately, early investigators revealed that preparation of microemulsions using solubilization enhancers can lead to the formation of fully dilutable formula at low surfactant/ oil ratio 37 . Considering this concept in the current study, the authors formulated three other non-ionic carvacrol microemulsions containing the common solubilization enhancers namely PG, ethanol and isopropanol as shown in Table 1 systems 3-5 .…”

“…In more details, PG which is a diol -bearing molecule, can arrange itself at the carvacrol-water interfacial film along with the original surfactant leading to increase of its elasticity and decrease of the interfacial tension. That behavior can lead to enhancement of the spontaneous film curvature, making its value less than zero which in turn prevents formation of gel phases and facilitates formation of microemulsion 37,40 . The dilutable nature of carvacrol microemulsion formulated with water/PG typically fulfilled the aim of this study for selection to the antimicrobial evaluation.…”

“…Thus the short chain alcohols ethanol and isopropanol were introduced in the formulation of two other carvacrol microemulsions systems 4, 5, Table 1 . These excipients were found to be effective in formulating dilutable microemulsion with reduced surfactant/oil ratio 2.3:1.0 in clove essential oil microemulsion 32 or even 1.5:1.0 in limonenebased microemulsion 37 . Figures 1d, e showed the role of short chain alcohols in enhancing the capacity of formation of carvacrol microemulsion.…”

“…The percentage of the mono-phasic area relative to the total area of the triangle phase diagram was taken as a measure for the extent of carvacrol microemulsion formation and was denoted by A T . This term was previously used by other investigators for the same purpose 37 . A T represents the percentage of the total mono-phasic and isotropic microemulsion area that encompasses carvacrol-continuous, bi-continuous and water-continues structures.…”

“…This study can reveal some factors that may lead to the formulation of an effective aqueous-based antibacterial carvacrol microemulsion. 2.2 Formulation and phase behavior of non-ionic carvacrol microemulsions Five non-ionic carvacrol microemulsions were formulated using the aqueous phase titration method 37 . The composition of these systems was illustrated in Table 1.…”