A study was made of the characteristics of microemulsions composed of sucrose monostearate (SMS), medium-chain triglycerides (MCT), or R-(+)-limonene, alcs., and water. The systems are homogeneous, soft, and waxy solids at room temp. but liquefy and structure into homogeneous microemulsions when heated to \textgreater40 °C. The amt. of solubilized water is enhanced as a function of the alc./oil ratio and is inversely proportional to the alc. chain length. Over 60 wt% water can be solubilized in systems consisting of propanol/MCT/SMS at a wt. ratio of 3:1:4 (initial wt. ratio). These microemulsions are unique and differ from nonionic ethoxylated-based microemulsions in that their viscosity is very low and is reduced with increasing amts. of solubilized water. The elec. cond. increases only slightly as a function of the water content and does not show typical bicontinuous or percolated behavior. The water in the core of the microemulsion strongly binds to the headgroups of the surfactant. Only at \textgreater15 wt% solubilization of water was free or bulk water detected in the core of the microemulsions. Such unique behavior of the core water might have a possible application in systems requiring monitoring of enzymic (lipase) reactions carried out in the microemulsions as microreactors. [on SciFinder(R)]

Factors affecting water solubilization in four-component nonionic microemulsion systems stabilized by polyol nonionic surfactants (sucrose esters) have been investigated. The effect of changing the chain length of alcohol (used as cosurfactant) and the lipophilic moiety of surfactant have been explored. The maximum water solubilization in the isotropic region (at oil/n-butanol ratio of 1) was 47, 23 and 55 wt.% for sucrose stearate (S-1570), sucrose laurate (L-1695) and sucrose palmitate (P-1570), respectively. Replacing the triglyceride oil (MCT) by dodecane caused a decrease in the water solubilization (40 wt.%) for sucrose stearate with an oil/n-butanol ratio of 1. The empirical BSO (Bansal, Shah, O'Connell) \[\1] equation which was derived as an empirical condition for maximum water solubilization in microemulsions stabilized by anionic surfactants, in relation to the cosurfactant (alcohol) and oil chain lengths, i.e. N-S = N-O + N-A, where N-S, N-O, N-A are the surfactant chain lengths, oil and alcohol, respectively, was re-examined for this type of surfactants. This study demonstrates that a maximum water solubilization is obtained when the N-S = (N-O +/- 3) + N-A for N-S is greater than 14; when N-S is less than 14, this equation cannot predict the maximum water solubilization. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.

Sub-zero temp. differential scanning calorimetry (SZT-DSC) was applied to a model nonionic water-in-oil microemulsion system based on: sucrose ester nonionic surfactants/water/1-butanol/n-alkanes (C12-C16). The max. water solubilization was 40, 56 and 80% for the systems contg. n-dodecane, n-tetradecane and n-hexadecane as the oil phase, resp. Two types of solubilized water were detected, the so-called bulk (free) water present in the core of the microemulsion and the interfacial (bound) water attached at the interface to the surfactant (and/or butanol). The internal distribution of water within the microemulsions was detd. along two diln. lines (with 32 and 43% of the initial surfactant). For the n-dodecane system the max. interfacial(bound) water is 12 and 14% along the two diln. lines, resp.; above this water content a core of bulk (free) water is formed. The type of the oil and the butanol interfacial participation strongly affect the water internal distribution. Both the temp. of fusion, Tf, of the bulk (free) water and of the interfacial (bound) water are strongly affected by butanol and oil. The nature of the surfactant, its fatty chain length and its HLB also affect the binding capability and capacity of water in microemulsion systems. For both n-dodecane and n-hexadecane, 11-13 mols. of water can be bound to the surfactant at the interface. [on SciFinder(R)]

Structured fluids such as emulsions and liq. cryst. mesophases can be used to control aroma release. This study shows that the use of a gas sensor array coupled with pattern recognition anal. can be particularly useful in studying volatile profiles. A mixt. of 8 carefully selected volatile, hydrophilic and hydrophobic compds. was entrapped in 4 different matrixes: water, liqs. (sunflower oil, unsatd. monoglycerides), emulsion (20% wt. water) and cubic phases (20 and 30% wt. water). A clear discrimination between the release pattern of the different matrixes has been measured by the sensor array system. It has been shown that the cubic phase release patterns is not only controlled by its compn. but also depended strongly on the lipid/water interfacial area. The combined use of structured fluids (structure-release relationship) and sensor arrays allows the release patterns of volatiles to be controlled and distinguished. [on SciFinder(R)]

The solubilization of 5 hydrophilic water-sol. aroma compds. in self-aggregating triblock amphiphilic copolymers of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO), with similar percentages of PEO and different mol. wts., was studied. The 5 hydrophilic compds. (diacetyl, 2-methylpyrazine, pyrrole, furfural, guaiacol) were carefully selected to represent hydrophilic mols. with a similar mol. wt. and mol. vol., but with different abilities to interact with the micellar core of PPO moieties and with the PEO palisade side chains. The solubilized solute mole fraction increased and the aggregate-water partition coeffs. of the solutes decreased with increasing free solute concn. in the aq. phase. The partition coeffs. were smaller than those obtained for hydrophobic compds. and equil. was reached at lower solubilization values. Guaiacol was the least hydrophilic mol. and had the highest partition coeff. Diacetyl was the most water-sol. compd. and exhibited the smallest partition coeff. The data reveal that the higher mol. wt. polymers solubilized more solute than the low-mol.-wt. polymers. Moreover it is supposed that at low solute concns., guaiacol (contg. a hydroxyl electron acceptor group) penetrates the core of the micelle and displaces water while at more elevated concns. it seems to be solubilized in the micelle corona. Diacetyl, the most hydrophilic solute investigated (consisting of electron donor groups), prefers mainly the corona since its affinity for the polymeric core is very weak. The solubilization occurs in the palisade layer and the partition coeff. is independent of the free solute concn. Selective site (palisade vs. core) solubilization of hydrophilic compds. in polymeric micelles can be a powerful tool to protect sensitive materials from reactants present in the continuous water phase and to conduct surface-sensitive org. reactions. Furthermore, selective release properties of reactants and products can be designed. (c) 2000 Academic Press. [on SciFinder(R)]

Thermal reactions of cysteine/furfural and cysteine/ribose mixts. were studied in model systems to gain more insight into the influence of structured fluids such as L2 microemulsions and cubic phases on the generation of aroma compds. Formation of 2-furfurylthiol from cysteine/furfural was particularly efficient in L2 microemulsions and cubic phases compared to aq. systems. The reaction led to the formation of two new sulfur compds., which were identified as 2-(2-furyl)thiazolidine and, tentatively, N-(2-mercaptovinyl)-2-(2-furyl)thiazolidine. Similarly, generation of 2-furfurylthiol and 2-methyl-3-furanthiol from cysteine/ribose mixts. was strongly enhanced in structured fluids. The cubic phase was shown to be even more efficient in flavor generation than the L2 microemulsion. It was denoted "cubic catalyst" or "cubic selective microreactor". The obtained results are interpreted in terms of a surface and curvature control of the reactions defined by the structural properties of the formed surfactant assocs. [on SciFinder(R)]

As a basis for crystn. studies, the solubilization of amino acids (glycine, l-histidine, and l-phenylalanine) in H2O-in-isooctane microemulsions stabilized by AOT (Na di-2-ethylhexyl sulfosuccinate) was studied. The max. amt. of amino acid that could be solubilized was detd. by the solid-liq. extn. method, and the effect of the guest mols. (amino acids) on the size and shape of the microemulsion droplets and their thermal properties were detd. using SAXS and DSC measurements, resp. The solubilization of glycine mols., which primarily dissolve in the H2O pool, was slightly lower than their soly. in pure H2O, decreasing with increasing concn. of AOT and increasing with increasing H2O content in the microemulsion. But the solubilization of phenylalanine, which is primarily located at the H2O/oil interface, exceeded several times the soly. in H2O, the solubilized amt. increasing with increasing AOT and/or H2O concns. Histidine had characteristics intermediate between these 2 extremes. Solubilization of those mols. effected an increase in droplet size. The thermal anal. showed that loading of the microemulsion droplets with glycine has a much stronger effect on the thermal behavior of the emulsified H2O than has loading with phenylalanine. The low solubilization of glycine as compared to its soly. in pure H2O can be explained by the state of H2O within the microemulsion droplets, i.e., part of it is present as free H2O and part as H2O bound to the AOT headgroups. The loading of phenylalanine changed the shape of the microemulsion droplets from spherical to ellipsoidal, and with increasing droplet sizes, the [phenylalanine]/[AOT] molar ratio at the interface increased. [on SciFinder(R)]

{The crystn. of glycine and L-phenylalanine from water-isooctane microemulsions stabilized by AOT (sodium di-2-ethylhexyl sulfosuccinate) has been investigated. Crystn. phenomena were strongly affected by the localization of the solubilized mols. within the microemulsion droplets. In the case of glycine, which is solubilized within the water pools, a significant redn. in crystal size was obsd. in the temp. range investigated (Ti = 35 °C

Two techniques for extn. and purifn. were used in order to obtain a purified saponins ext. from several sources (fenugreek, soybean, locust bean and sesame). The results indicate that fenugreek steroid saponins ext. has the best surface properties and reduces the surface tension to 33.3 mN/m and the tetradecane-water interfacial tension from 44 mN/m to 7.5 mN/m. The HLB value was 18. Three different types of oil (n-tetradecane, soybean oil, tricaprylin) were emulsified with a 6 wt% aq. soln. of saponins to give an av. droplet size of 0.7 $μ$m (stable after month). An effective synergism is seen when these emulsions were prepd. with sucrose fatty acid esters as co-surfactant. Foaming power was also evaluated. [on SciFinder(R)]