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)]

The most complex emulsions are those of foods and, therefore, are difficult to stabilize. An infinite no. of microstructures of combinations of proteins, carbohydrates, fats and lipids are present in food systems. There is an increasing awareness of many investigators to the relevance of the principles of colloid and surface science to many of the technol. problems related to advanced foods. Amphiphilic mols. play a key role in the stabilization of many of the food colloids. It is, therefore, very important to understand the interfacial behavior of these mols. and to select the proper ones for the proper activity. Synthetic surfactants and emulsifiers are widely used in many of our foods, but, it becomes very important to replace them by natural mols. with good health records. The following review with 49 refs. discusses the main natural occurring mols. that are in use today and the future trends in this area. Monomeric emulsifiers such as mono- and diglycerides, lecithins and lysolecithins are still key players. Glycolipids are present only in very minor concns. in plants and animals and therefore are not com. available. Saponins are a very interesting group of materials with increasing potential. The polymeric amphiphilic compds. are "native" and enzymically modified proteins. However, in situ products chem. modified by a Maillard reaction can also be used as emulsifiers. The most interesting new emulsifiers are some selected hydrocolloids that exhibit surface properties and emulsification capabilities. Enzymically modified hydrocolloids show significant promise. Bio-surfactants have also been studied and considered as emulsifiers, but are not food grade products. New trends and progress will also be discussed. [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)]

A review with 95 refs. Sucrose esters are biodegradable surfactants that can be manufd. in various hydrophilic-lipophilic properties using different fatty acids varying in their lipophilic chain length. These surfactants are used in different industries including pharmaceutical, food processing, detergents, agricultural and others. Few no. of works had been done using sucrose esters in microemulsions. In this review we tried to introduce the relevant works that enlighten the behavior of sucrose esters in phase diagrams prepd. using different oils and medium chain alcs. We hope that this review article can be an aid to those researchers interested in microemulsions based on sucrose esters and their applications. [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.

It is well documented that weak or strong interactions between macromols. such as proteins or polysaccharides can synergistically improve the emulsifying capabilities of each of the biopolymers. A study was made to explore the nature of the adsorbed layer in emulsions formed in the presence of casein and a new anionic hydrocolloid extd. from Portulaca oleracea in several emulsification protocols. Electrophoretic mobility of medium chain triglyceride oil emulsion droplets and the corresponding adsorbing creamed phases were measured. The zeta potential magnitudes were calcd. in view of the possible pH dependent ionic-hydrogen bonding interactions between casein and a new ionic gum at the oil-water interfaces. Emulsions stability were detd. from the emulsification stability indexes and emulsification activity index. It was found that POG can adsorb by itself or together with casein onto the oil-water interface. Displacement of the POG from the interface by the casein will take place at pH values that will enhance repulsion forces between the biopolymers. However, complementary adsorption of a possible casein-POG complex will occur if the pH is enhancing the strong attraction interaction between the two biopolymers. The attraction forces between the two biopolymers will enhance the stability of oil-in-water emulsions formed in the presence of the two macromol. amphiphiles. [on SciFinder(R)]

Phospholipase A2 (PLA2) was used to hydrolyze phosphatidylcholine (PC) in microemulsions. Phase diagrams were constructed for mixts. of alcs. (C2-C6), medium chain triglycerides (tricaprylin, TC) or vegetable oils, PC and water, and areas corresponding to isotropic systems were identified. The PC hydrolysis was carried out with high yields at various PC/(TC+alc.) compns. within the areas of isotropic systems at increasing amts. of solubilized water. The initial reaction rates depended on the aggregation state of the PC (size and nature of microemulsion structures), as well as on temp. and mode of calcium addn. At low enzyme concns., hydrolysis was preceded by a "lag phase" followed by an abrupt increase in rate. By contrast, no latency was obsd. at higher PLA2 PC ratios and the rate was significantly higher. The easy access of the enzyme to the substrate in the curved phospholipid-contg. microemulsion particles facilitate activation of the enzyme and "pushes" the reaction to completion. Hence, these microemulsions can serve as microreactors for the enzymic high yield hydrolysis. [on SciFinder(R)]

The properties of a new gum extd. from the leaves of an edible herb (Portulaca oleracea) were studied. The biopolymer is a relatively small mol. wt. polysaccharide and exhibits significant charge d. at pH \textgreater 2. The extd. gum has surface and interfacial properties derived from its chem. compn. and structure. The Portulaca oleracea gum (POG) adsorbs onto the oil (n-tetradecane or soya) interfaces and stabilizes oil-in-water emulsions. Emulsions (5 wt% oil and 0.7 wt% gum) are stable to flocculation and coalescence at room temp. (for a year) but upon heating the gum desorbs and the emulsion coalesces. Mechanistic considerations regarding its adsorption isotherms, the role of the residual proteinaceous matter contaminating the polysaccharide and the charge are discussed. POG is a good example of a new gum that can be considered as a food emulsifier. [on SciFinder(R)]

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)]

A galactomannan isolated from fenugreek seed has ≥50 repeating units of mannose and galactose in a ratio of 0.5-1.0 and 1.8-1.0, a protein content of ≤20%, a saponin content of ≤5%, and a lipid content of ≤1%, and is useful as an active ingredient in nutraceutical and cosmetic products. [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 83 refs. is given. Research activities carried out on various gums as emulsifiers are discussed and questions related to adsorption at interfaces of certain gums are clarified. Gum arabic, galactomannans (guar, locust bean, and fenugreek gum), xanthan gum, Portulaca oleracea and Opitus ficus gums, tragacanth gum, and pectins are included. Adsorption isotherms and the role of proteins in galactomannans, mechanistic considerations, protein-polysaccharide interactions, the stabilization by solid particles (colloidal microcryst. cellulose as emulsifier), and biosurfactants are discussed. [on SciFinder(R)]

New crystal forms of aspartame were prepd. by using microemulsions comprising: (a) introducing aspartame into a microemulsion formed from an oil phase, an aq. phase and at least one emulsifier; (b) destabilizing the microemulsion to effect recrystn. of aspartame; (c) sepg. solid phase crystals from the liq. phase in which they are contained; and (d) cleaning the crystals to remove traces of the oil phase and surfactant. Thus, aspartame (22 g) was solubilized by mech. stirring in a microemulsion contg. 234 g (65%) of isooctane, 36 g (10%) of water and 90 g (25%) AOT at 65°. The microemulsion was then cooled at a rate of 1° per min with const. sirring to a final temp. of 5° and stirred at this temp. for an addnl. two hours to induce crystn. The crystal gave an X-ray pattern characteristic of form III aspartame. [on SciFinder(R)]

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