A review with 57 refs. Multiple emulsions are complex systems of emulsion within an emulsion, where the droplets of the dispersed phase themselves contain even smaller dispersed droplets. The two major types are water-in-oil-in-water (W/O/W) and oil-in-water-in-oil (O/W/O) double emulsions. Double emulsions are unstable thermodn. systems, which tend to cream, flocculate and coalesce. Much effort has been made to develop methods of 'better sealing' in the inner and outer interfaces and to reduce the droplet size of the emulsions. Dissolved or dispersed compds. in the inner phase of double emulsions tend to be released to the outer phase primarily via a reverse micellar transport (which is diffusion-controlled) or through the thin lamellae of a surfactant phase migrating to the outer phase via the outer interface. It is difficult to control the release of the solutes unless macromols. are used to improve lamellar stabilization (steric stabilization) forming a rigid surfactant-polymer complex at the interfaces. The review describes recent achievements in the use of BSA, casein, gelatin and other naturally occurring macromols. together with monomeric-amphiphilic mols. for possible future applications in food systems. [on SciFinder(R)]

Multiple emulsions are complex systems, termed "emulsions of emulsions", i.e. the droplets of the dispersed phase contain even smaller dispersed droplets themselves. Each dispersed globule in the double emulsion is sepd. from the aq. phase by a layer of oil-phase compartments. Double emulsions have significant potential in many applications since, at least in theory, they can serve as an entrapping reservoir for active ingredients that can be released from the inner phase to the outer phase by a controlled and a sustained mechanism. Many of the potential applications are in pharmaceuticals. In practice, double emulsions are thermodynamically unstable systems with a strong tendency for coalescence, flocculation and creaming. Most double emulsions consist of relatively large droplets, cannot withstand storage regimes and have a strong tendency to release the entrapped matter in an uncontrolled manner. Much work has been devoted in the last decade in order to the improve the stability of the multiple emulsions and the control of the release rates of the addenda. The most recent achievements are: Use of polymeric emulsifiers to improve interface coverage and to better anchor into the dispersed phases; Reduce droplets size by improving methods of formation: improved understanding of the release mechanisms and use of various additives to control the release via the reverse micellar mechanism. 35 Refs. [on SciFinder(R)]

Glutamic acid can crystallize in two polymorphic structures depending on the crystn. regime. The study demonstrates an efficient method to preferentially crystallize the nonstable polymorphic structure (the $\alpha$-form) in the presence of surface active agents. The rate of transformation depends on the rate of growth of $\beta$ and not on the rate of dissoln. of $\alpha$. The growth rate of $\beta$ was a function of the supersatn. of the solute in soln. The transformation could be inhibited by the addn. of surfactants. The surfactants are capable of adsorbing preferentially to the $\alpha$-growing crystals and soln. mediating (retarding) the transformation of the $\alpha$- to the $\beta$-form. Probably the surfactant nature and steric considerations were important for the inhibition of both nucleation and growth of the $\beta$-polymorph. A Langmuir approach indicated that the kinetic parameter was related to the vol. of surfactant adsorbed at the crystal surface. No changes in crystal morphol. were obsd., indicating that adsorption was not specific to any crystal face. Different mechanisms of surfactant adsorption were suggested: adsorption of single mols. at low concns. of surfactant and formation of hemimicelles at higher concns. [on SciFinder(R)]

The effects of free and bound water on the dielec. properties of microemulsions prepd. with the non-ionic surfactant Brij 97 were investigated. For the calcn. of the relative amts. of free and bound water, a simple multi-layered dielec. model was applied. The model considers the microemulsion as a sum of three sep. layers consisting of a "dry" microemulsion, free water and bound water, resp. The method is based on dielec. measurements of microemulsions at a frequency for which the dielec. permittivity and the dielec. losses for bound and free water have significantly different magnitudes. The dielec. contribution of free water to the relaxation spectrum of the microemulsion can be obtained, allowing both fractions to be calcd. In contrast to the traditional procedures used for calcn. of bound water from the relaxation spectrum, this method does not involve analyses of overlapping relaxation processes. [on SciFinder(R)]

Proton NMR measurements were conducted on a U-type model quaternary nonionic microemulsion contg. varying amts. of water and having a fixed wt. ratio of surfactant [octaethylene glycol mono-n-dodecyl ether; C12(EO)8], cosurfactant (pentanol), and oil (dodecane). Chem. shift and T1 relaxation time data were used to obtain information about the microemulsion properties and structure. A slow exchange was obsd. between the hydroxyls of water, C12(EO)8, and pentanol in microemulsions contg. up to 10 wt% water. This is precedence of the hydroxyl-water interaction over hydration of the ethylene oxide (EO) groups of the surfactant. The fraction of bound water was calcd. from the chem. shift and T1 data. For the model system, chem. shift measurements indicated an inversion from W/O to O/W microemulsion at about 55-60 wt% water, in agreement with the microviscosity values evaluated from T1 data: 1.1 cP (55 wt% water) compared to 4.7 cP (30 wt% water) and 12.7 cP (10.7 wt% water). The irregularities in the monotonic dependence of the chem. shifts on water content in the microemulsion at 18 and 55 wt% water were interpreted to possibly reflect structural changes that took place in soln. [on SciFinder(R)]

The transport properties near the percolation temp. threshold in the ternary H2O-in-oil microemulsion stabilized by ionic surfactant was studied by measuring the self-diffusion coeffs. of all the constituents of the microemulsion, and the cond. at 10-40°. It can be conjectured that 2 different transition mechanisms of the charge carriers in this temp. region may take place. These may be attributed to either the transfer of counterions from 1 droplet to another through H2O channels or hopping of surfactant ions from droplets within clusters. The cond. and dielec. polarization below the percolation threshold is mainly due to the motion of counterions via H2O channels within the droplet clusters and not a charge-hopping mechanism at the surfactant interface. Above the percolation threshold the latter mechanism appears, connected with migration of surfactant mols. from droplet to droplet within a percolation cluster. The 1st mechanism still dominates. [on SciFinder(R)]

Subzero temp. DSC was applied to a model nonionic microemulsion system (water/pentanol/dodecane/C12(EO)8) to det. the relative concns. of bound and free H2O. Conclusions are drawn concerning the low-temp. behavior of the system, the surfactant hydration, and the role of pentanol. The surfactant becomes satd. with H2O at a ratio of 3 mols. of "interphase" H2O per ethylene oxide group. Free H2O can only be detected by DSC at higher water/surfactant ratios. Apparently nonfreezing H2O is not formed in the model system (at least not before the inversion from W/O to O/W microemulsion has occurred). The thickness of the bound H2O layer in the nonionic model system evaluated by several methods is ∼ 5 \AA (i.e., 2 monolayers of interphase H2O are closely assocd. with the surfactant). Although pentanol enhances H2O solubilization and is present at the interface, its interaction with H2O or surfactant is not revealed by DSC. [on SciFinder(R)]

A review with 170 refs. on micelles, microemulsions, emulsions, and other emulsion systems and their applications in the food industry. [on SciFinder(R)]

A review with 430 refs. Interfacial phenomena, emulsion formation, stability, characterization, etc., are discussed. [on SciFinder(R)]

A review with 49 refs. on w/o/w emulsions stabilized by polymeric surfactants. [on SciFinder(R)]

A dough conditioner is described wherein the dough conditioner is soybean peroxidase or an aq. ext. of soybean hulls. [on SciFinder(R)]

The study of the relaxation properties near the percolation threshold in ternary water-in-oil microemulsion stabilized by ionic surfactant are presented as an example of the dynamics in self-assembled complex fluids. The data treatment for dynamic behavior of the microemulsions was carried out in the time domain in terms of dipole correlation functions. The correlation functions exhibit complex non-exponential relaxation behavior and must be de-convoluted into normal modes and represented as the sum of non-exponential terms; exp[-(t/$\tau$)$\beta$]. The temp. dependence of the stretched parameters shows the existence of spatial, temporal, and energetic disorder assocd. with anomalous diffusion of charge carriers in the percolation clusters. [on SciFinder(R)]

One recently reported application of microemulsions is as a fire-resistant hydraulic fluid where efficacy and stability depend among other factors upon the water-solubilizing capacity of the microemulsion and on the relative concn. of the surfactant. A model for such a microemulsion system has been studied using cryo-transmission electron microscopy (cryo-TEM), 1H NMR self-diffusion, and small angle X-ray (SAXS) and neutron scattering (SANS). The phase behavior of the system contg. a 1p1:2 oil:alc.:surfactant wt. ratio is characterized by a single continuous microemulsion region starting from a soln. contg. no water and approaching the water corner. Along this diln. line, a structural transition sequence: oil drops → short range, noncontinuous lamellar microstructure → weakly hydrated aggregates is inferred as the water concn. is decreased. The local lamellar microstructure, i.e., stacks of surfactant sheets, oil, and water, randomly oriented in space without the long range correlations that characterize a lamellar liq. crystal is imaged for the first time. [on SciFinder(R)]

Jojoba oil is a mixt. of long chain esters comprising C18, C20, C22 and C24 monounsatd. acids and alcs., but in particular two ester mols. contg. 40 and 42 carbon atoms which make up to 80% of the oil. Five quality parameters of jojoba oil were compared with cotton oil in time-temp. conditions simulating abusive industrial deep-fat frying. In four out of five quality criteria, namely, color index, oxidn. index, peroxide value and viscosity, jojoba oil was found to be superior to cotton oil, while free fatty acids showed comparable low values, within the range expected, in industrial frying operations. Oil uptake of a deep-fried restructured potato product was significantly higher in jojoba oil as compared to cotton oil. The enhanced stability during deep-fat frying of jojoba oil could play a part in improving the shelf-life of fried foods. [on SciFinder(R)]

Ca oxalate was crystd. in the presence of the anionic surfactant diisooctyl sulfosuccinate, AOT, and the phase compn. of the ppts. (by x-ray diffraction powder patterns and thermal anal.) and their crystal growth morphol. (by SEM and electron diffraction) were detd. In the control systems and in the presence of low concns. of AOT (below the crit. micellar concn., CMC) Ca oxalate monohydrate (CaC2O4·H2O, COM) was the dominant crystal phase. Crystals grown in the presence of C(AOT)\textgreater0.75 CMC were thinner and more elongated than in the controls, indicating preferential adsorption of the surfactant at the 1̅01 and \010\ crystal faces. When the AOT concn. exceeded the crit. micellar concn., the morphol. changes in COM crystals became more intense and the compn. of the ppts. abruptly changed to mixts. of COM and Ca oxalate dihydrate (CaC2O4·(2+x)H2O, x\textless0.5; COD) with a COM/COD ratio up to 50%. The morphol. of the COD crystals was mostly unaffected. The phase change was attributed to preferential adsorption of AOT - as surface aggregates - at the crystal faces of COM with the consequence of strong inhibition of nucleation and crystal growth of this crystal type and growth of the kinetically less favored COD crystals. [on SciFinder(R)]