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)]

A review on the mechanisms of sweating and blooming with respect to the sepn. of oils from wax and the crystn. of fatty acids. By understanding these mechanisms, the solid-liq. sepn. phenomena caused by sweating and blooming may be avoided during the storage of oleaginous solid cosmetic pencils such as lipsticks, eyeliners, and eyebrow pencils. Studies show that sweating is due to the expansion of oils in the wax matrix and/or shriveling of the wax matrix due to increased temp. and humidity. In contrast, blooming involves the soly. of higher fatty acids, a modulator the consistency and hardness of oleaginous cosmetics in oils, and is assocd. with a series of processes such as dissoln.-sepn.-transformation of crystals of higher fatty acids. [on SciFinder(R)]

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)]

in Thermal Behavior of Dispersed Systems

A review with refs. on food systems and food emulsions from the food emulsifier perspective using natural and synthetic emulsifiers. [on SciFinder(R)]

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)]

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)]

in Water Science for Food, Health, Agriculture and Environment

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)]

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)]

A review. Some general aspects of food constitution and of the most useful calorimetric techniques are described. The thermal behavior of the food constituents water, lipids, carbohydrates, proteins, and minor constituents is characterized. The thermal behavior of raw and reconstituted foods is considered. Self-heating, self-ignition, and safety aspects are included. Differential scanning calorimetry and DTA are emphasized. [on SciFinder(R)]

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)]

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)]