All Publications

Axel Benichou, Abraham Aserin, and Nissim. Garti. 2001. “Polyols, high pressure, and refractive indices equalization for improved stability of W/O emulsions for food applications.” Journal of Dispersion Science and Technology, 22, 2 & 3, Pp. 269–280. Abstract
Mixts. of polyols (glycerol, propylene glycol, glucose) and water were emulsified in oil (iso-Pr myristate (IPM), medium chain triglycerides (MCT), long chain triglycerides (LCT), and d-limonene) under elevated pressures and homogenization, in the presence of polyglycerol polyricinoleate (PGPR), glycerol monooleate (GMO), and their mixt. as emulsifiers to form water-in-oil emulsions. High pressures was applied to: (a) the emulsion, (b) the aq. phase and (c) the oil phase in the presence of the emulsifiers (PGPR and GMO). Under optimal pressure (2000 atms) applied to the ready-made emulsion or to the aq. phase prior to its emulsification, and with optimal compn. (30wt% polyol in the aq. phase and MCT as the oil phase), the aq. droplets were stable for months and submicron in size (0.1 $μ$m). Moreover, due to equalization of the oil and the aq. phases refractive indexes, the emulsions were almost transparent. Pressure and polyols have synergistic effects on the emulsions stability. During prepn., surface tensions and interfacial tensions were dramatically reduced until an optimal water/polyols ratio was achieved, which allows rupturing of the droplets to submicronal size (0.1 $μ$m) without recoalescence and fast diffusion to the interface. These unique W/O emulsions are suitable for prepg. W/O/W double emulsions for sustained release of active materials for food applications. [on SciFinder(R)]
M Bujan, M Sikiric, N Filipovic-Vincekovic, N Vdovic, N Garti, and H Fueredi-Milhofer. 2001. “Effect of Anionic Surfactants on Crystal Growth of Calcium Hydrogen Phosphate Dihydrate.” Langmuir, 17, 21, Pp. 6461–6470. Abstract
The effect of anionic surfactants (single-chained Na n-dodecyl sulfate (SDS), asym. double-chained Na bis(2-ethylhexyl) sulfosuccinate (AOT), and two-headed disodium oleoamido PEG-2 sulfosuccinate) on the crystn. process of Ca H phosphate dihydrate (DCPD) was studied. All surfactants, depending on the type and actual concn., showed inhibitory effects on the overall crystn. process. Below the crit. micelle concn. (cmc), electrostatic adsorption of surfactant anions on lateral crystal faces inhibited crystal growth and changed crystal morphol. Above the cmc, SDS and AOT caused phase changes; i.e., a mixt. of DCPD and octacalcium phosphate was formed. [on SciFinder(R)]
Heike Bunjes and Kirsten. Westesen. 2001. “Influences of colloidal state on physical properties of solid fats.” In Cryst. Processes Fats Lipid Syst., Pp. 457–483. Marcel Dekker, Inc. Abstract
A review discusses the resulting phenomena from the disintegration of solid, cryst. lipids into particles of colloidal size, which is related to the colloidal state of the matrix lipids. Topics discussed include supercooling and formation of dispersions of supercooled melts; phase sepn. within colloidal triacylglycerol particles; polymorphic transitions and other aging phenomena; effect of particle size of triacylglycerols in further alterations of their physicochem. properties; and the gel formation. Several examples are presented to illustrate that it is very risky and often impossible to conclude from the behavior of bulk materials to that in the colloidal state. [on SciFinder(R)]
Shmaryahu Ezrahi, Abraham Aserin, Monzer Fanun, and Nissim. Garti. 2001. “Subzero temperature behavior of water in microemulsions.” Surfactant Science Series, 93, Thermal Behavior of Dispersed Systems, Pp. 59–120. Abstract
A review. Results of studies are summarized dealing with the surfactant/water interactions in microemulsions, which are investigated by subzero-temp. differential-scanning calorimetry (SZT-DSC). Several states of water are defined in terms of their thermal behavior. The exothermic and endothermic modes of SZT-DSC are compared with each other, and the question is discussed how the relative amts. of free and bound water in a microemulsion sample can be detd. The distribution of free and bound water is analyzed as a function of the total water content in the microemulsion systems. The case of non-freezable water is discussed and the thickness of the bound water layer is evaluated. The interaction of alcs. with other components of microemulsion systems is also addressed. Special emphasis was laid on the phase sepn. during the cooling and freezing of microemulsion samples. [on SciFinder(R)]
M Fanun, E Wachtel, B Antalek, A Aserin, and N Garti. 2001. “A study of the microstructure of four-component sucrose ester microemulsions by SAXS and NMR.” Colloids and Surfaces, A: Physicochemical and Engineering Aspects, 180, 1-2, Pp. 173–186. Abstract
Sucrose esters form a class of surfactants with the important properties of being biodegradable, non-toxic and capable of forming temp.-insensitive microemulsions. Such microemulsions would be expected to suit a variety of food-based and pharmaceutical applications; however to date little is known about their structure and stability. In this study, the Winsor IV microemulsion systems composed of sucrose esters (SE)/1-butanol/water and oils such as n-dodecane, n-hexadecane and medium chain triglyceride (MCT), have been investigated using small angle X-ray scattering (SAXS), pulsed gradient spin echo (PGSE) NMR and viscosity measurements. The SAXS results for the sucrose monostearate (S1570) system at SE/MCT/1-butanol=1.5:1.1 clearly indicate that the periodicity d increases with increase in water content and is not sensitive to the nature of the oil. From the amphiphilicity factor, fa, and the correlation length, $\xi$, one can conclude that the n-dodecane-based microemulsion system is the most ordered. Microstructure investigation by PGSE NMR gives evidence of structural changes as the water content in the system increases. The oil self-diffusion remains unchanged when MCT serves as the oil phase. However, when the oil is paraffinic in nature (n-dodecane and n-hexadecane) the self-diffusion coeff. indicates participation of the oil mols. at the interface. Surfactant self-diffusion is only weakly affected by the water content. The shorter chain oils (n-dodecane and MCT) solubilize a max. of 40 and 47 wt. % Of water and cannot invert, while the long chain paraffinic (n-hexadecane-based system) inverts into an O/W microemulsion. The viscosity of these microemulsions decreases with increasing water content. The absence of a yield stress in any of the samples studied, together with the linearity of the flow curves, is evidence that there are no relaxation processes in these microemulsions which show a non-Newtonian flow behavior. [on SciFinder(R)]
M Fanun, M Leser, A Aserin, and N Garti. 2001. “Sucrose ester microemulsions as microreactors for model Maillard reaction.” Colloids and Surfaces, A: Physicochemical and Engineering Aspects, 194, 1-3, Pp. 175–187. Abstract
Thermal reactions of cysteine/furfural mixt. were studied as a model system to gain more insight into the influence of structured fluids such as water-in-oil nonionic microemulsions on the generation of aroma compds. The microemulsion systems were composed of: sucrose ester/water/dodecane+alc.(1/1), where the sucrose esters are sucrose stearate (S1570) and sucrose laurate (L1695), and the alcs. are medium-chain alcs. (C2OH to C6OH). Formation of predominately 2-furfurylthiol (FFT) is obtained in the aq. cysteine/furfural system. The formation of FFT was enhanced under similar reaction conditions in water-in-oil microemulsions and led to the formation of two new sulfur compds. that were identified as 2-(2-furyl)-thiazolidine and tentatively N-(2-mercaptovinyl)-2-(2-furanyl)-thiazolidine. The reaction rates (furfural conversion or consumption) decrease with the decrease in the water content and the increase in alc. chain length (C2 to C6 were used as cosurfactant) and with the increase of pH from 4 to 8 in the system contg. butanol as the alc. The rates of reaction increase also with the increase of temp. in the range of temps. studied from 30 to 60°. The kinetic consts. (k) and energy of activation (Ea) were calcd. Microemulsions of W/O are excellent reaction media for the Maillard reaction providing a high selectivity, high conversion rates and specificity. [on SciFinder(R)]
N Garti. 2001. “Food emulsifiers and stabilizers.” In Food Shelf Life Stab., edited by M. Eskin D.S. and Robinson, Pp. 211–263. CRC Press LLC. Abstract
A review with refs. on food systems and food emulsions from the food emulsifier perspective using natural and synthetic emulsifiers. [on SciFinder(R)]
N Garti, A Aserin, E Wachtel, O Gans, and Y Shaul. 2001. “Water Solubilization in Nonionic Microemulsions Stabilized by Grafted Siliconic Emulsifiers.” Journal of Colloid and Interface Science, 233, 2, Pp. 286–294. Abstract
Microemulsions contg. octanol, decanol, or dodecanol as the oil phase and oligomeric, grafted nonionic amphiphiles based on ethoxylated polymethylsiloxanes (Silwets) have been studied. It was demonstrated that significant amts. of water can be solubilized only when the hydrophobic siliconic backbone is very short (trimers). The water solubilization was evaluated using SAXS, DSC, and cond. measurements. It was found that up to 40 wt% of water can be solubilized in dodecanol and Silwet L-7607 (MW 1000 and 75 wt% ethylene oxide (EO)). Surprisingly, no free water was detected in the aggregate core. All the solubilized water was confined in the vicinity of the interphasal region and froze at -10°C and below. Up to three mols. of water can be assocd. with each EO headgroup. Based on SAXS measurements, the structural units of the microemulsions were interpreted to be lamellar-like, a form previously found for the related monomeric microemulsions. (c) 2001 Academic Press. [on SciFinder(R)]
Nissim Garti and Martin E Leser. 2001. “Emulsification properties of hydrocolloids.” Polymers for Advanced Technologies, 12, 1-2, Pp. 123–135. Abstract
A review with 49 refs. is presented, demonstrating that certain hydrophilic (anionic or non-ionic) polysaccharides purified to a level of being almost protein-free can exhibit surface and emulsification properties, in spite of their rigid and hydrophilic nature. The adsorption isotherms of the surface-active biopolymers are similar to other macromol. amphiphiles. The main gums discussed are those of the galactomannan family, i.e, locust bean gum, guar gum, and fenugreek. Other gums from less known sources, i.e., Portulaca Oleracea and Opuntia Ficus, also exhibit surface properties. Statements previously made by several authors, claiming that hydrocolloids cannot be considered as emulsifiers, were inaccurate. The requirements for built-in hydrophobic moieties on the hydrocolloids' backbone internal structure are not obligatory for active adsorption. Adsorption can be induced by a salting-out effect, resulting in semi-solid interfacial layers. Hydrocolloids can form thick birefringent gel-like mech. barriers at the oil-water interface of emulsion oil droplets. This new category of naturally occurring hydrocolloid emulsifiers should be reconsidered by food technologists and by other emulsion technologists for other industrial applications. [on SciFinder(R)]
Nissim Garti and Junko. Yano. 2001. “The role of emulsifiers in fat crystallization.” In Cryst. Processes Fats Lipid Syst., edited by N. Garti K and Sato, Pp. 211–250. Marcel Dekker, Inc. Abstract
A review discusses the effect of emulsifiers on crystn. processes of fats, including nucleation, growth, and phase transitions. Surfactants affect rheol. properties of fats by changing the network formation of fat crystals affecting various phenomena, such as bloom, gloss, and cracking of fat coatings in chocolate or other fat-rich solid products. The emulsifiers affect the fat crystn. and the wetting and adhesion properties of the fats in dispersed systems based in dispersed fat. The behavior of fats could be better predicted using amphiphiles, which allows better control of the phys. properties. [on SciFinder(R)]
Otto Glatter, Doris Orthaber, Anna Stradner, Gunther Scherf, Monzer Fanun, Nissim Garti, Veronique Clement, and Martin E Leser. 2001. “Sugar-Ester Nonionic Microemulsion: Structural Characterization.” Journal of Colloid and Interface Science, 241, 1, Pp. 215–225. Abstract
Surfactants contg. sugar components and fatty acids satisfy the quality stds. for food application. The food grade sugar ester in this study is a com. sucrose monoester of stearic acid (abbreviated SES), the oil phase consists of a 1:1 mixt. of n-tetradecane and l-butanol. The originally planned food grade oil, a medium chain triglyceride, is substituted by tetradecane because tetradecane is available as a fully deuterated product, which is necessary for some structural investigations. The investigated system is solid at room temp., but liquefies and structures into a homogeneous microemulsion when heated to above 37°C. The structural characterization of the microemulsions was studied. The established methods for this purpose are scattering methods, such as small-angle scattering of X-rays and neutrons and dynamic light scattering. These scattering techniques can be used to obtain valuable information on the size, shape, and internal structure of colloids and complex fluids. The authors started the investigation with the pseudobinary system SES, tetradecane and l-butanol, varying the SES content. The scattering results show that the sugar ester forms inverse globular micelles in the oil phase. The size of these micelles is about 6 nm. While the size is nearly const. in a wide SES concn. regime (5 up to 40% surfactant), the vol. or aggregation no. increases significantly with SES. This is explained by an increasing replacement of l-butanol mols. by sugar-ester mols. in the micelles formed. Moreover, it can be shown that these micelles strongly overlap. Their center-to-center distance is about 3.8 nm at 40% SES at a micellar diam. of 6 nm. The micellar overlap leads to a highly reduced diffusion of the micelles as was found with dynamic light scattering. When incorporating water in the micellar core, the micelles swell up to about 10 nm and the shape of the aggregates becomes more and more elongated with higher water content. (c) 2001 Academic Press. [on SciFinder(R)]