The artificial sweetener, aspartame, is a dipeptide, consisting of a hydrophobic phenylalanine methyl ester entity and a hydrophilic aspartyl residue. In this work, its solubilization in five different types of water in oil (w/o) microemulsions (MEs) was investigated. The stabilizing surfactants and cosurfactants of the MEs were ME1, sodium di-2-ethylhexyl sulfosuccinate (ACT) and no cosurfactant; ME2, maleic anhydride alpha-olefin copolymer and dimethyl amino ethanol; ME 3, sucrose ester monostearate and n-butanol; ME 4, L-alpha-phosphatidylcholine and n-butanol; and ME 5, mono- and diglycerides of fatty acids and L-alpha-phosphatidylcholine. The maximum amount that could be dissolved (boundary concentration) was determined by adding powdered aspartame to a heated ME and cooling to a specified temperature under controlled conditions. The solutions that remained clear for at least 4 days were regarded as stable, and those of the stable solutions with the highest aspartame concentrations were taken as having the boundary concentrations. From the solubility data, the distribution of the aspartame molecules between the w/o interface and the water pools was calculated, and the results were correlated with the molecular structure and ionic state of the surfactant. The results show that aspartame can be solubilized in all the investigated MEs to an extent, exceeding by far its solubility in pure water, and that overall solubilization is most efficient in water/isooctane MEs stabilized with ACT (ME1). While the aspartame solubility in the water pools was comparable in all the investigated MEs, the aspartame/surfactant molar ratio at the w/o interface was found to decrease with decreasing polarity of the stabilizing surfactant at the interface. In addition to the solubilization studies, the effect of aspartame on some properties of ME1 was investigated. It was found that aspartame lowers the interfacial tension at the water/isooctane/AOT interface and, under certain conditions, stabilizes unstable mixtures of water, isooctane, and ACT. The results of small-angle X-ray scattering measurements show that the ME droplet sizes increase in the presence of aspartame molecules and their shapes change from near spherical to ellipsoidal. It was concluded that aspartame acts as a cosurfactant in water/isooctane MEs stabilized with ACT.

A review. Structured self-assembled liqs. have been considered as efficient microreactors for org. and enzymic reactions. Only recently scientists learned to use food-grade cosolvents and coemulsifiers together with hydrophilic non-ionic surfactants and to construct U-type phase diagrams with large isotropic regions ranging continuously from the oil-rich corner to the water-rich corner without any phase sepn. The U-type microemulsions facilitate triggering and control of certain reactions by changing water activities. Maillard thermal degrdn. between sugars and amino acids is the main, and almost the only, chem. reaction that was studied in food-grade microemulsions. Some examples of recent studies include: Maillard processes in binary structured fluids composed of monoglycerides of fatty acids and water forming microemulsions and lyotropic liq. cryst. structures; pseudoternary and pseudoquaternary W/O microemulsions; U-type microemulsions (W/O, O/W and bicontinuous microemulsions); enzymic reactions aimed to prep. other surfactants such as sugar esters, monoglycerides and lysolecithins or triglycerides. Reactions in microreactors lead to unique new products. The reaction products and rates are controlled by the hydrophilicity/lipophilicity of the reagents (guest mols.), their molar ratios, type of oil phase, nature of surfactants and oil/surfactant ratios, nature of curvature and its elasticity (adjusted by cosolvent and coemulsifier) and by the water activity. The field is in its infancy and will need work of many more model reactions before it will be used in industrial food applications. Enzymic reactions in non-food microemulsions are common practice but only few examples of food microemulsions as enzymic microreactors were extensively studied. [on SciFinder(R)]

Alcs. and polyols are essential components (in addn. to the surfactant, H2O, and oil) in the formation of U-type self-assembled nano-structures, (sometimes called L-phases or U-type microemulsions). These microemulsions are characterized by large isotropic regions ranging from the oil side of the phase diagram up to the aq. corner. The isotropic oily solns. of reverse micelles (the concs.) can be dild. along some diln. lines with aq. phase to the direct micelles corner via a bicontinuous mesophases (i.e., 2 structural transitions). This diln. takes place with no phase sepns. or occurrence of liq. cryst. phases. The structural transitions were detd. by viscosity, cond., and pulsed gradient spin echo NMR (PGSE NMR), and are not visible to the eye. Two guest nutraceutical mols. (lutein and phytosterols) were solubilized, at their max. solubilization capacity, in the reversed micellar solns. (L2 phase) and were further dild. with the aq. phase to the aq. micellar corner (L1 phase). Structural transitions (for the 2 types of mol.) from H2O-in-oil to bicontinuous microstructures were induced by the guest mols. The transitions occurred at an earlier stage of diln., at a lower H2O content (20% aq. phase), than in the empty (blank) microemulsions (transitions at 30% aq. phase). The transitions from the bicontinuous microstructure to the oil-in-H2O microemulsions were retarded by the solubilizates and occurred at later diln. stage at higher aq. phase contents (50% aq. region for empty microemulsion and \textgreater60% for solubilized microemulsion). As a result, the bicontinuous isotropic region, in the presence of the guest mols., becomes much broader. It seems that the main reason for such guest-induced structural transitions is related to a significant flattening and enhanced rigidity of the interface. The guest mols. of the high mol. vol. are occupying high vol. fraction of the interface (when the solubilization is maximal). [on SciFinder(R)]

A review. An outline is given on the use of microemulsions and other microcompartmentalized systems as media for chem. reactions. Examples are presented to illustrate the principles of different possible reactions and the used microheterogeneous media. Treated is the prepn. of nanosized inorg. particles from microemulsions, the prepn. of mesoporous inorg. materials from surfactant liq. crystals, and the use of solid foams prepd. from highly concd. emulsions to make meso/macroporous inorg. oxide materials. The use of microheterogeneous systems as media for the prepn. of org. polymers and of microemulsions for bioorg. synthesis is also described. [on SciFinder(R)]

Various industries including food and pharmaceuticals are sharing increasing interest in microemulsions. Also, one can demonstrate that solubilization of active materials within the core or interface of microemulsions may have environmental benefits. In this work, the authors report three examples of new microemulsion formulations specially designed to be capable of solubilizing active materials and protecting the environment from the emission of hazardous matter or protecting sensitive mols. from the detrimental effects of the environment. In the first example, fire-resistant ingredients were incorporated in hydraulic fluids based on water-in-oil (W/O) microemulsions and their typical characteristics were described. In the second example, five-component oil-in-water (O/W) microemulsions were designed to solubilize lycopene and protect it from exposure to light. In the third example, a friendly solvent (Bu lactate) was microemulsified to form nanosized liq. droplets capable of solubilizing bromine-based bactericide formulations of sophisticated wood preservatives. The new vehicles exhibit a very significant solubilization capacity and can be applied in aq. media. In the last example, the active matter may be triggered when demanded and the release will be followed by film formation. [on SciFinder(R)]

Anal. of the phenolic constituents of shea (Vitellaria paradoxa) kernels by LC-MS revealed 8 catechin compds.-gallic acid, catechin, epicatechin, epicatechin gallate, gallocatechin, epigallocatechin, gallocatechin gallate, and epigallocatechin gallate-as well as quercetin and trans-cinnamic acid. The mean kernel content of the 8 catechin compds. was 4000 ppm (0.4% of kernel dry wt.), with a 2100-9500 ppm range. Comparison of the profiles of the 6 major catechins from 40 Vitellaria provenances from 10 African countries showed that the relative proportions of these compds. varied from region to region. Gallic acid was the major phenolic compd., comprising an av. of 27% of the measured total phenols and exceeding 70% in some populations. Colorimetric anal. (101 samples) of total polyphenols extd. from shea butter into hexane gave an av. of 97 ppm, with the values for different provenances varying between 62 and 135 ppm of total polyphenols. [on SciFinder(R)]

Microemulsions are of growing interest to the food industry as vehicles for delivering and enhancing solubilization of natural food supplements with nutritional and health benefits. The incorporation of mol. phytosterols, cholesterol-lowering agents, in food products is of great interest to the food industry. The use is demonstrated of water-dilutable food-grade microemulsions consisting of ethoxylated sorbitan ester (Tween 60), water, R-(+)-limonene, ethanol, and propylene glycol as vehicles for enhancing the phytosterols solubilization. Phytosterols were solubilized up to 12 times more than the dissoln. capacity of the oil [R-(+)-limonene] for the same compds. The solubilization capacity of phytosterols and cholesterol along a diln. line in a pseudo-ternary phase diagram [wt. ratio of R-(+)-limonene/ethanol/Tween 60 const. at 1p1:3] was correlated to the microstructure transitions along the diln. line. Structural aspects were studied by self-diffusion NMR spectroscopy. The ability of phytosterols to compete with cholesterol for penetration into bile salt micelles in the gut may be limited to rich aq. systems (O/W microemulsion). [on SciFinder(R)]

The microstructure of an unusual Winsor IV isotropic region of five-component microemulsions based on nonionic surfactants was studied. The microemulsions are composed of R(+)-limonene, water, propylene glycol (PG), ethanol (EtOH), and polyoxyethylene sorbitan monostearate (Tween 60) with a 1:1:3 R(+)-limonene/ethanol/surfactant wt. ratio. The phase diagrams of the system are characterized by an extended single continuous isotropic region starting from an oil-rich soln. contg. no aq. phase (reverse micelles) to the water/propylene glycol (1/1) corner (swollen direct micelles). The microemulsions seem to be attractive for food applications. The microstructure changes gradually, smoothly, and continuously upon increasing the aq. phase content. The microemulsion transforms from a water-in-oil (W/O) microemulsion to a bicontinuous phase and to an oil-in-water (O/W) microemulsion. The microstructure of the microemulsion along a selected diln. line, is probed using pulsed gradient spin-echo NMR, cond., and viscosity. The results are compared with a corresponding non-food-grade system based on C18:1E10 (Brij 96v). The hydrodynamic radius (RH) of O/W microemulsion samples based on Brij 96v and Tween 60, at 90% aq. phase, was detd. to be 5.4 ± 0.2 and 5.2 ± 0.2 nm, resp., and the calcd. values of the area of the polar headgroup (a) are 87 for Brij 96v and 160 \AA2 for Tween 60-based microemulsions. The ratio of the water self-diffusion coeff., DW, to the PG self-diffusion coeff. (DPG) (termed the L ratio) was found to be sensitive to the aq. phase content. In the O/W microemulsions, the water/PG mixt. diffuses as hydrogen bonded entity (mol. diffusion controlled), while in the W/O microemulsions, the PG partitions, in part, at the interface and the dominant diffusion process is neither aggregate nor mol. controlled. [on SciFinder(R)]

Organo-inorgano nanocomposites with colloidal dimensions have interesting optical, catalytic, and mech. properties, particularly when such hybrids are reinforced with transition metal oxide nanoparticles. Nanoparticles with a mean size of 1.0-2.4 nm are obtained through hydrolysis of aluminum isopropoxide in the L2 phase of amphiphilic (PDMS-POE) polydimethylsiloxane-polyoxyethylene Silwet L-7607-octanol/acetylacetone-water mixts. The particle sizes are related weakly to the microemulsion compn.: 0.8-1.2 nm for 20 wt% Silwet L-7607 and 2.0-2.4 nm for 50 wt% Silwet L-7607. Protection of the particles against aggregation is ensured through their confinement in the intra-aggregate colloidal domains. Factors affecting the hydrolysis-condensation process of acetylacetone-complexed aluminum isopropoxide in copolymer-poor and copolymer-rich regions of PDMS-POE W/O microemulsions are studied by Fourier transform IR spectroscopy, small angle X-ray scattering, and transmission electron microscopy. Prepd. nanoparticulate dispersions possess long-term stability and form clear mixts. in different org. polar and nonpolar solvents. (c) 2002 Academic Press. [on SciFinder(R)]

A review on basic and applied knowledge on protein-polysaccharide interactions in aq. medium and at the oil-water interface in food emulsion systems. [on SciFinder(R)]

Water-in-oil-in-water (W/O/W) double emulsions with improved stability and less polydispersity in droplet size distribution were prepd. using polyglycerol polyricinoleate (PGPR) as emulsifier in the inner aq. phase and replacing the common nonionic hydrophilic monomeric emulsifiers by a "protein-polysaccharide hybrid" in the outer interface. Amphiphilic macromol. hybrids with specific interfacial recognition capabilities to be termed "biomacro-mol.-recognition hybrids" have been prepd. in aq. soln. by interacting whey protein isolate (WPI) with hydrocolloids (xanthan gum, galactomannans) at selected pH and wt. ratios. The binary aq. mixts. do not coacervate or ppt. but form stable mol. adducts. At pH lower than the isoelec. point of the protein (pH 4.6), the yield of encapsulation of glucose (a model marker) in the inner phase of the double emulsion is close to 95%. The emulsion droplets are stabilized by both steric and electrostatic contributions (zeta potential is close to +30 mV). Rheol. measurements indicate that, at low pH, such systems behave as viscous ones with G'' (loss modulus) greater than G' (storage modulus). When the pH is close or greater than the isoelec. point of the protein, the system exhibits a more pronounced elastic behavior (G' \textless G'') that can explain the redn. in emulsification capabilities of such mixts. In this case the yield of encapsulation is less than 10% and the double emulsion droplets are larger than 10 $μ$m. At pH ≤ 2, the adducts can efficiently stabilize double emulsions and serve as an efficient and thick barrier against the release of vitamin B1 entrapped in the core of the W/O/W double emulsions. The release of the vitamin was less than 18% after three weeks of storage at room temp. (against 100% of release at neutral pH). [on SciFinder(R)]

The hydration behavior of the system polyoxyethylene (10) oleyl alc. [C18:1(EO)10 or Brij 97]/water/dodecane/butanol (model system B) was investigated along a diln. line for which the resp. wt. ratio of dodecane:butanol:Brij 97 is 3:3:4. Two exptl. methods were applied: time domain dielec. spectroscopy (TDDS) and sub-zero temp. differential scanning calorimetry (SZT-DSC). Two types of bound water (with melting peaks at - 25 and - 11°C) were detected by SZT-DSC (using the endothermic mode), whereas TDDS revealed only one such type. Nevertheless, roughly the same total amt. of bound water was estd. from these two techniques. The av. no. of bound water mols. per ethylene oxide (EO) group, NW/EO, is 2.3 (TDDS data) or 2.5 (SZT-DSC data) in good agreement with the observation that 1-2 water layers are formed in the hydration of ethoxylated surfactants. We have also shown that butanol is involved in the formation of the bound water that melts at - 25°C. We suggest that butanol mols. occupy binding sites within the second hydration shell, thereby reducing the expected total bound water content. [on SciFinder(R)]

The interactions of two groups of hydrated model crystals, CaHPO4.2H2O (DCPD) vs. Ca4(HPO4)(PO4)2 (OCP) and Ca oxalate monohydrate (COM) vs. Ca oxalate dihydrate (COD) with different org. additives are considered. DCPD ppts. as platelet-like crystals with the dominant faces shielded by hydrated layers and charged lateral faces. In the 2nd system COM has charged surfaces, while all faces of COD are covered with layers contg. water mols. The org. mols. tested include neg. charged, flexible and rigid small and macromols. (glutamic and aspartic acid, citrate, hexaammonium polyphosphate, phytate, and polyaspartate) and anionic surfactants (sodium dodecyl sulfate, SDS, sodium diisooctyl sulfosuccinate, AOT, sodium cholate NaC, and disodium oleoamido PEG-2 sulfosuccinate, PEG). Two types of effects were demonstrated: (i) effect on crystal growth morphol.: flexible org. mols. with high charge d. and anionic surfactants affected the growth morphol. of DCPD and COM by selectively interacting with the charged lateral faces while rigid mols. (phytate, polyaspartate) specifically recognized the dominant (010) face of DCPD due to structural and stereochem. compatibility. (ii) effect on phase compn.: anionic surfactants at concns. above the crit. micelle concn. promoted growth of OCP and COD resp. by selectively adsorbing at, and inhibiting growth of nuclei of DCPD and/or COM, which were dominant in the resp. control systems. The effect was esp. pronounced in the Ca oxalate pptn. system, where in some cases complete reversal of the phase compn. occurred. The important role of the hydrated layer, as part of the structure of the investigated crystal hydrates, in the above crystal additive interactions is discussed. [on SciFinder(R)]

A review. Fenugreek gum is a unique galactomannan-type nonionic polysaccharide. This water-sol. hydrocolloid differs from most dietary fibers since it has only moderate viscosity and gelation properties, and yet the most pronounced health benefits. FenuPure is a purified fenugreek hydrocolloid product that is odor-free and fat-free. It has strong beneficial effects on diabetes mellitus since it acts as an excellent glucose level controller. It can also contribute to decreases of blood cholesterol levels and body wt. [on SciFinder(R)]

The improved water and oil solubilization in the presence of polyols (propylene glycol, PG, and glycerol, Gly) and short-chain alcohol (ethanol) in U-type nonionic W/O and O/W food microemulsions was investigated. The phase behavior of systems based on Tweens (ethoxylated sorbitan esters) was compared with non-food-grade systems based on C18:1E10 (Brij 96v). Short-chain alcohol (ethanol in food-grade systems) together with polyols (glycerol and propylene glycol) when added to a three component system (oil-surfactant-water) induce the formation of both water-in-oil (W/O) and oil-in-water (O/W) microemulsions. Alcohols and polyols destabilize the liquid crystalline phase and extend the isotropic region to higher surfactant concentrations. The total monophasic area, A(T), at R(+)-limonene/ethanol of 1/1 (w/w) and aqueous phase of water/PG of 1/1 (w/w), was 73 and 64% of the total area of the phase diagram for Brij 96v and Tween 60, respectively. The transition from a W/O microemulsion into an O/W microemulsion happens gradually, and continuously without any phase separation. The total monophasic area depends also on the type of the oil, on the composition of the polar and apolar phases, and on the nature of the polyol. The results are discussed in terms of BSO equation, spontaneous curvature, H-0, film flexibility, K and (K) over bar, surfactant oil and surfactant cosolvent compatibility and the participation of the polyol at the interface. The difference in temperature sensitivity of PG-based microemulsions vs. temperature sensitivity of Gly-based is demonstrated and explained. (C) 2002 Elsevier Science B.V. All rights reserved.