Peer Review Publications

N Garti, A Aserin, I Tiunova, and M Fanun. 2000. “A DSC study of water behavior in water-in-oil microemulsions stabilized by sucrose esters and butanol.” Colloids and Surfaces, A: Physicochemical and Engineering Aspects, 170, 1, Pp. 1–18. Abstract
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)]
S Vauthey, Ch. Milo, Ph. Frossard, N Garti, ME Leser, and HJ Watzke. 2000. “Structured Fluids as Microreactors for Flavor Formation by the Maillard Reaction.” Journal of Agricultural and Food Chemistry, 48, 10, Pp. 4808–4816. Abstract
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)]
S Vauthey, P Visani, Ph. Frossard, N Garti, ME Leser, and HJ Watzke. 2000. “Release of volatiles from cubic phases: monitoring by gas sensors.” Journal of Dispersion Science and Technology, 21, 3, Pp. 263–278. Abstract
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)]
Junko Yano, Helga Fueredi-Milhofer, Ellen Wachtel, and Nissim. Garti. 2000. “Crystallization of organic compounds in reversed micelles. II. Crystallization of glycine and L-phenylalanine in water-isooctane-AOT microemulsions.” Langmuir, 16, 26, Pp. 10005–10014. Abstract
{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
Junko Yano, Helga Fueredi-Milhofer, Ellen Wachtel, and Nissim. Garti. 2000. “Crystallization of Organic Compounds in Reversed Micelles. I. Solubilization of Amino Acids in Water-Isooctane-AOT Microemulsions.” Langmuir, 16, 26, Pp. 9996–10004. Abstract
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)]
A Benichou, A Aserin, and N Garti. 1999. “Steroid saponins from fenugreek seeds: extraction, purification and surface properties.” Journal of Dispersion Science and Technology, 20, 1 & 2, Pp. 581–605. Abstract
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)]
Helga Furedi-Milhofer, N Garti, and A Kamyshny. 1999. “Crystallization from microemulsions - a novel method for the preparation of new crystal forms of aspartame.” Journal of Crystal Growth, 198/199, Pt. 2, Pp. 1365–1370. Abstract
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)]
N Garti. 1999. “What can nature offer from an emulsifier point of view: trends and progress?” Colloids and Surfaces, A: Physicochemical and Engineering Aspects, 152, 1-2, Pp. 125–146. Abstract
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)]
N Garti, A Aserin, and Y Slavin. 1999. “Competitive adsorption in O/W emulsions stabilized by the new Portulaca oleracea hydrocolloid and nonionic emulsifiers.” Food Hydrocolloids, 13, 2, Pp. 139–144. Abstract
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)]
N Garti, V Clement, M Leser, A Aserin, and M Fanun. 1999. “Sucrose ester microemulsions.” Journal of Molecular Liquids, 80, 2,3, Pp. 253–296. Abstract
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)]
N Garti, A Aserin, I Tiunova, and H Binyamin. 1999. “Double emulsions of water-in-oil-in-water stabilized by alpha-form fat microcrystals. Part 1: Selection of emulsifiers and fat microcrystalline particles.” Journal of the American Oil Chemists' Society, 76, 3, Pp. 383–389. Abstract
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.
N Garti, Y Slavin, and A Aserin. 1999. “Portulaca oleracea gum and casein interactions and emulsion stability.” Food Hydrocolloids, 13, 2, Pp. 127–138. Abstract
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)]
N Garti, D Lichtenberg, and T Silberstein. 1999. “The hydrolysis of phosphatidylcholine by phospholipase A2 in microemulsion as microreactor.” Journal of Dispersion Science and Technology, 20, 1 & 2, Pp. 357–374. Abstract
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)]
Nissim. Garti. 1999. “Hydrocolloids as emulsifying agents for oil-in-water emulsions.” Journal of Dispersion Science and Technology, 20, 1 & 2, Pp. 327–355. Abstract
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)]