{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

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)]

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.

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)]

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)]

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)]

We prepd. stable oil-in-water emulsions of argan oil with two different types of mixts. of nonionic emulsifiers. Three different types of oil (Israeli argon oil, Moroccan argan oil, and soybean oil) were emulsified with mixts. of Span 80 and Tween 80. The optimum HLB value for argan oil was 11.0 (±1.0). The argan oil-in-water emulsions were stable for more than 5 mo at 25°C. Synergistic effects were found in enhancing stability of emulsions prepd. with sucrose monostearate. The origin of the oil and the internal content of natural emulsifiers, such as monoglycerides and phospholipids, have a profound influence on its interfacial properties and on the stability of the argan oil-in-water emulsions. [on SciFinder(R)]

A new water-sol. anionic low-mol. wt. polysaccharide (gum) with surface, interfacial and emulsification properties was extd. from leaves of the legume Portulaca oleracea (POG). Vegetable oil-in-water emulsions with small droplets (2-5 $μ$m), stable to flocculation and coalescence (for a few months) can be formed in the presence of 0.1-0.8 wt% POG. The gum adsorbs onto the oil-water interface. The nature of this adsorption was tested by evaluating the competitive adsorption of Tweens (ethoxylated sorbitan esters) and the POG in oil-in-water emulsions. It was demonstrated that Tweens form weak assocs. with the POG at the interface at certain emulsifier/gum binary mixts., but any excess concns. of the Tween will cause a gradual displacement of the gum from the interface. The POG and/or the gum-Tween assocs. (complex) have weak anchoring capabilities at the interface. [on SciFinder(R)]

Solubilization and crystn. of the artificial sweetener aspartame (APM) in water/isooctane microemulsions stabilized with sodium diisooctyl sulfosuccinate (AOT) was investigated. The amt. of aspartame that could be solubilized depended primarily on the amt. of surfactant and on the temp. The max. AOT/aspartame molar ratio at the w/o interface is shown to be 6.2 at 25°C. It was concluded that the dipeptide is located at the w/o interface interspersed between surfactant mols. and that it acts as a cosurfactant. A new crystal form, APM III, was obtained by cooling of hot w/isooctane/AOT microemulsions contg. solubilized aspartame. The new crystal form exhibits a distinct x-ray diffraction powder pattern, as well as changes in the FTIR spectra, thermogravimetric and DSC patterns. H-NMR spectra of APM III dissolved in D2O were identical to the spectrum of com. aspartame recorded under the same conditions. The new crystal form has greatly improved dissoln. kinetics. [on SciFinder(R)]

Double emulsions are commonly stabilized by monomeric and/or polymeric emulsifiers. Pickering stabilization by solid particles such as colloidal microcrystalline cellulose has been mentioned only once as a possible technique to stabilize the external interface of the water-in-oil-in-water emulsion. No further work was carried out exploring this option. The present study shows that solid microcrystalline fat particles of alpha-form are capable of adsorbing at the water-oil interface and, together with other hydrophobic emulsifiers, can stabilize water-in-oil (W/O) emulsions. The crystals must be submicron in size in order to effectively adsorb and arrange at the interface. Large crystals do not fit and were found to flocculate as free crystals in the continuous oil phase. The alpha-form crystals can be obtained by flash-cooling saturated triglycerides in vegetable oils in the presence of emulsifiers, such as polyglycerol polyricinoleate (PGPR), that stabilize the dispersion and serve as alpha-tending crystal structure modifiers. It was assumed that PGPR also serves as a cross-linker or bridge between the crystalline fat particles and the water, and facilitates the anchoring of the fat particles in the oil phase in one direction while dangling itself in the water phase. The double emulsion droplets prepared with these W/O emulsions are relatively large in size (6-18 mu m), but stable to coalescence. The marker (NaCl) does not seem to release with time, suggesting that the fat particles form microcapsules on the water interface, totally sealing the water from releasing its addenda. The systems seem to have a significant potential for food emulsions.

A review with 42 refs. discussing the drawbacks and prospects of hydrocolloids as food emulsifying agents, as native hydrocolloids and as modified (chem., enzymically) macrobiopolymeric amphiphiles. [on SciFinder(R)]

Nanoparticles (1-6 nm) of transition metals (e.g., Pt, Pd), alloys, metal oxides (e.g., FeOOH, SiO2), and ceramics are prepd. by chem. reaction under mild conditions using precursor solns. of complex liqs. (e.g., microemulsions, liq. crystals) contg. surfactants and alkoxides. The resulting nanoparticles are dispersed in polymer solns. as fine colloids, and used to form transparent nanoparticle-contg. plastic films. The water is non freezing, the mild conditions are atm. pressure and a temp. range of room temp. to 70°C, and the reaction is selected among a hydrolysis, redn. and exchange process. In an example, a Pd colloidal dispersion was prepd. from a soln. contg. K2PdCl4, Aliquat 336, dichloroethane and water, which was reacted with NaHCO2 under Ar at 75°C for 1 h. The solvent was evapd. off, leaving a waxy residue which was washed and dried. The Pd nanoparticles were redispersed in polyvinylalc., and used for forming a transparent film coating on a glass plate. [on SciFinder(R)]

A review with 66 refs. Prepn. of multiple emulsions, evaluation of yield of prepn. and formulations are discussed. [on SciFinder(R)]