Peer Review Publications

Anan Yaghmur, Abraham Aserin, and Nissim. Garti. 2002. “Furfural-Cysteine Model Reaction in Food Grade Nonionic Oil/Water Microemulsions for Selective Flavor Formation.” Journal of Agricultural and Food Chemistry, 50, 10, Pp. 2878–2883. Abstract
The thermal reaction between cysteine and furfural was investigated at 65° C in 5-component food grade oil/water (O/W) microemulsions of R-(+)-limonene/ethanol, EtOH/water/propylene glycol, PG/Tween 60 as apart of a systematic study on the generation of aroma compds. by utilizing structured W/O and O/W fluids. The furfural-cysteine reaction led to the formation of unique aroma compds. such as 2-furfurylthiol, 2-(2-furanyl)thiazolidine (main reaction product), 2-(2-furanyl)thiazoline, and N-(2-mercaptovinyl)-2-(2-furanyl)thiazolidine. These products were detd. and characterized by GC-MS. Enhancement in flavor formation is termed "microemulsion catalysis". The chem. reaction occurs preferably at the interfacial film, and therefore a pseudophase model was assumed to explain the enhanced flavor formation. The product internal compn. is dictated by process conditions such as temp., time, pH, and mainly the nature of the interface. Increasing water/PG ratio leads to a dramatic increase in the initial reaction rate (V0). V0 increased linearly as a function of the aq. phase content, which could be due to the increase in the interfacial concn. of furfural. Microemulsions offer a new reaction medium to produce selective aroma compds. and to optimize their formation. [on SciFinder(R)]
Aviram Spernath, Anan Yaghmur, Abraham Aserin, Roy E Hoffman, and Nissim. Garti. 2002. “Food-Grade Microemulsions Based on Nonionic Emulsifiers: Media To Enhance Lycopene Solubilization.” Journal of Agricultural and Food Chemistry, 50, 23, Pp. 6917–6922. Abstract
Water-dilutable food-grade microemulsions consisting of ethoxylated sorbitan esters, and in some cases blended with other emulsifiers, water, (R)-(+)-limonene, ethanol, and propylene glycol, have been prepd. These 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. Lycopene, an active natural lipophilic antioxidant from tomato, has solubilized in water-in-oil, bicontinuous, and oil-in-water types of microemulsions up to 10 times the oil [(R)-(+)-limonene] dissoln. capacity. The effects of aq.-phase diln., nature of surfactant (hydrophilic-lipophilic balance), and mixed surfactant on solubilization capacity and solubilization efficiency were studied. Structural aspects studied by self-diffusion NMR were correlated to the solubilization capacity, and transformational structural changes were identified. [on SciFinder(R)]
A Yaghmur, A Aserin, and N Garti. 2002. “Phase behavior of microemulsions based on food-grade nonionic surfactants: effect of polyols and short-chairs alcohols.” COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 209, 1, Pp. 71–81. Abstract
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.
Anan Yaghmur, Abraham Aserin, and Nissim. Garti. 2002. “Phase behavior of microemulsions based on food-grade nonionic surfactants: effect of polyols and short-chain alcohols.” Colloids and Surfaces, A: Physicochemical and Engineering Aspects, 209, 1, Pp. 71–81. Abstract
The improved water and oil solubilization in the presence of polyols (propylene glycol, PG, and glycerol, Gly) and short-chain alc. (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 alc. (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. Alcs. and polyols destabilize the liq. cryst. phase and extend the isotropic region to higher surfactant concns. The total monophasic area, AT, at R(+)-limonene/ethanol of 1/1 (wt./wt.) and aq. phase of water/PG of 1/1 (wt./wt.), was 73 and 64% of the total area of the phase diagram for Brij 96v and Tween 60, resp. The transition from a W/O microemulsion into an O/W microemulsion happens gradually, and continuously without any phase sepn. The total monophasic area depends also on the type of the oil, on the compn. of the polar and apolar phases, and on the nature of the polyol. Solubilization properties are explained n terms of spontaneous curvature, film flexibility, etc. Deviations from the BSO equation are explained in terms of the nature of the oil and surfactants. The difference in temp. sensitivity of PG-based microemulsions vs. temp. sensitivity of Gly-based is demonstrated and explained. [on SciFinder(R)]
R Adleman and RW Hartel. 2001. “Lipid crystallization and its effect on the physical structure of ice cream.” In Cryst. Processes Fats Lipid Syst., Pp. 329–355. Marcel Dekker, Inc. Abstract
A review discusses the role of lipid crystn. in the development of structure during the processing of ice cream. The rate and extent of lipid crystn. during processing of ice cream is dependent on the nature of the fat phase. Processing condition, lipid source, and emulsifier type and level, can all influence the crystn. behavior of ice cream and lead to differences in organoleptic properties, which contribute to its final structure, quality, and eating properties. [on SciFinder(R)]
Dino Aquilano and Giulio. Sgualdino. 2001. “Fundamental aspects of equilibrium and crystallization kinetics.” In Cryst. Processes Fats Lipid Syst., Pp. 1–51. Marcel Dekker, Inc. Abstract
A review. A theor. treatise is given on crystal growth. Among the topics treated are: the equil. between a crystal and its mother phase, the equil. form of a crystal, the adhesion energy (Dupre formula) and the wetting of a crystal, the thermodn. and kinetics of homogeneous and heterogeneous nucleation, the nucleation of polymorphs and the Ostwald ripening, elementary growth mechanisms of certain crystal faces, and the effect of impurities on the crystal morphol. and habit. [on SciFinder(R)]
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)]
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)]
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)]
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, 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)]
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)]
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)]