Mixture Of Oleic Acid Research Articles

Phase behavior and properties of salt-free cationic/anionic surfactant mixtures of oleic acid and stearic acid

Cationic base surfactant, tetradecyltrimethylammonium hydroxide (TTAOH), can be obtained through anion exchange from tetradecyltrimethylammonium bromide (TTABr). Salt-free cationic and anionic (catanionic) surfactant mixtures were studied by mixing TTAOH with oleic acid (OA) or stearic acid (SA) in water. The phase behavior of TTAOH/OA/H2O is compared with that of TTAOH/SA/H2O. It was found that the phase behavior of TTAOH/OA/H2O and TTAOH/SA/H2O system differs from each other due to the existence of the unsaturated double carbon bond (C=C) in OA. At fixed total surfactant concentration (25 mg/mL) of TTAOH/OA/H2O system at 25°C, one can observe an isotropic L1 phase, and a L1/Lα two-phase region with increasing OA content. The volume of top turbid Lα phase increases while the bottom phase changes gradually from transparently clear to a bit turbid until a single Lα-phase is reached. Finally at high OA concentration, excess OA is separated from the bulk aqueous solutions. TTAOH/SA/H2O system usually forms white precipitating at 25°C due to the high chain melting temperature of SA. When heated to 60°C, however, the state of samples changes. At fixed total surfactant concentration of 25 mg/mL, an isotropic L1 phase and a milk-white or bluish Lα-phase are observed with increasing SA concentration. Transparent thin layers which are strongly birefringent form at the tops of some samples within the Lα-phase region. Finally, at high SA concentration, excess SA is separated from the bulk aqueous solutions. In addition to phase behavior study, we also measured the conductivity of TTAOH/OA/H2O system at 25°C and TTAOH/SA/H2O system at 60°C, respectively. Surface tension and rheological measurements were also performed on typical samples.

The influence of oleic acid-propylene glycol mixture and iontophoresis to propranolol transdermal transport

Propranolol has an intensive first pass metabolism, resulted in a low oral bioavailability. One alternative to circumvent such problem is the delivery by transdermal route. The objective of this study was to evaluate the effect of oleic acid 10 % (in propylene glycol 20 %) as enhancer, with and without iontophoresis, on transdermal transport of propranolol. Propranolol delivery was examined based on the in vitro transport studies across the rat skin (after hair removal) in a vertical diffusion cells system. Skin was pretreated with the mixture of oleic acid 10 % (in propylene glycol 20 %) for 3 hours. Iontophoresis was performed at a current density of 0.25 mA/cm2 for 3 hours. Donor compartment was filled with propranolol solution (5 mg/mL in citric buffer pH 5), while the acceptor phase was filled with phosphate buffer saline at pH 7.4. The results indicate that the enhancement methods increase the transdermal penetration of propranolol (p<0.05). The flux without any enhancement methods was 13.16 ± 0.79 mg/cm2/hour. The flux with either oleic acid - propylene glycol pretreatment, iontophoresis or combination of both were 28.75 ± 3.04 mg/cm2/hour, 40.47 ± 5.78 mg/cm2/hour, and 85.42 ± 16.94 mg/cm2/hour respectively. Based on mathematics calculation, if an iontophoretic patch of 12 cm2 is used after skin pretreatment with oleic acid - propylene glycol mixture, the steady state plasma concentration of propranolol could reach 24.65 mg/mL. Therefore, therapeutic level might be achieved. This indicated a promising future of transdermal delivery of propranolol. Key words : propranolol, transdermal, enhancer

Experimental investigation on granite emplacement during shortening

We present analogue experiments performed to investigate the emplacement of granitic plutons in a shortening upper crust. The models were made of quartz–sand to simulate the brittle crust and a low-viscosity mixture of silicone and oleic acid to reproduce granitic magmas. Shortening of the models was obtained by a moving wall while a special injection apparatus allowed syn-kinematic magma intrusion from the base of the models. Experimental results show that: (1) space for intrusions is achieved during the movement along thrust faults and mostly coincides with low-pressure areas developed into the thrust–anticlines; (2) intrusion shapes are strictly dependent upon the competition between shortening rate (Sh) and injection rate (Inj). For high Sh/Inj values, plutons were elongated with the long axis parallel to the thrust surfaces; (3) magma migrates horizontally away from the injection point and towards the external sector in the direction of tectonic transport a longer distance for high Sh/Inj values; (4) syn-kinematic emplacement is also controlled by model thickness; an increase in this parameter results in an increase in the pluton plan-view aspect ratio. These results support that the final shape of orogenic plutons emplaced at shallow crustal levels may be strongly controlled by deformational features.

Consecutive reactions in an oleic acid and acetic anhydride reaction medium

AbstractWhen mixing acetic anhydride and oleic acid, two consecutive reactions take place. The first one yields acetic‐oleic anhydride (AOA) and acetic acid. In the second one, oleic acid reacts with AOA to form oleic anhydride at 5% in a mixture when the initial molar ratio is 1:1. Therefore, at equilibrium, the global reaction yields a mixture of AOA, acetic anhydride, oleic acid, acetic acid and oleic anhydride. Based on a new HPLC protocol, all the species of the reaction medium could be separated and quantified. This permitted for the first time to study the kinetics and thermodynamics of the reaction. In the 30–70 °C range, reactions were of order 2 with partial orders of 1 for each reactant. Equilibrium constants were determined for both reactions. Enthalpy, entropy and activation energies were calculated for the main reaction. The influence of molar ratio on the composition at equilibrium was also investigated. The synthesis of AOA could thus be understood and new data were obtained for this singular molecule scarcely cited in the CAS database.

Binary, ternary and quaternary liquid–liquid equilibria in 1-butanol, oleic acid, water and n-heptane mixtures

This work reports on liquid–liquid equilibria in the system 1-butanol, oleic acid, water and n-heptane used for biphasic, lipase catalysed esterifications. The literature was studied on the mutual solubility in binary systems of water and each of the organic components. Experimental results were obtained on the composition of the coexisting phases of a series of ternary and quaternary mixtures of the components at 301, 308 and 313 K. The data were correlated successfully with the UNIQUAC model that was extended with ternary interaction parameters.

Synthesis of CuInSe2 and CuGaSe2 hexagonal microplates in oleic acid and oleylamine mixture

The compounds of I-II-VI2 family are the leading materials in the second-generation thin film solar cells. In this paper, we reported the synthesis of CuGaSe2 and CuInSe2 hexagonal microplates in the mixture of oleylamine and oleic acid. Regular copper, indium, and gallium salts as well as selenium powder were used as the precursors with stoichiometric ratio. X-ray diffraction patterns and selected area electron diffraction characterization confirmed their high crystalline quality. Furthermore, control experiments indicated two possible mechanisms of morphology transformation. The synthetic method is simple and reproducible and the as-prepared nanomaterials might find their application in solar cells.

Microwave Synthesis of Bimetallic Nanoalloys and CO Oxidation on Ceria-Supported Nanoalloys

A facile and fast microwave irradiation (MWI) method has been developed to prepare a wide variety of pure metallic and bimetallic alloy nanoparticles with controlled size and shape. The important advantage of microwave dielectric heating over convective heating is that the reactants can be added at room temperature (or slightly higher temperatures) without the need for high-temperature injection. The method allows the passivation of the nanocrystals by using a mixture of olyel amine and oleic acid as a solvent, a reducing agent, and a capping material. We investigate the controlled synthesis of nanoalloys among the nanocrystals of Au, Ag, Pt, Pd, Ru, Rh, Cu, and Ni by studying the changes in the structural and optical properties of the resulting nanoalloys with respect to the individual metals. Using the same method, we also report the synthesis of selected nanoalloys supported on ceria nanoparticles as nanocatalysts for CO oxidation. The catalytic activities for CO oxidation are presented and discussed. ...

Size- and shape-controlled synthesis of monodisperse Co nanoparticles from cobalt acetate by thermal decomposition

Monodisperse cobalt nanoparticles with relatively high coercivities were synthesized by thermal decomposition of cobalt acetate for the application of ultra-high density magnetic recording media. Without using any reducing agents, Co nanoparticles of 13.9–21.3 nm in size were prepared using various protecting agents and a high boiling point solvent trioctylamine. The Co nanoparticles prepared with the mixture of oleic acid, oleylamine, and polyvinylpyrrolidone (PVP) showed clear crystalline structure of face centered cubic, and their coercivity was measured to be 27.2 kA/m. PVP was effective in controlling particle growth while hindering agglomeration between the particles. The as-prepared Co nanoparticles with a moderate coercivity can be applicable to patterned media.

Oleic acid‐added embedding medium for histological analysis of hard tissue

For the histological analysis of hard tissue such as bone, various acrylate-based materials have been used as an embedding medium. However, commercial embedding media are expensive, and cutting the embedded block takes a long time. In this study, mixtures of methyl methacrylate (MMA), di-butyl-phthalate (DBP), and oleic acid (OA) were tested for possible application as an embedding medium for large and small undecalcified bone specimens. Mechanical properties were tested in a compressive mode. We investigated the change of hydrophilicity in the sectioned surface by measuring the contact angle depending on the OA. Crystallinity was analyzed using a X-ray diffractometer (XRD). Surface analysis was performed using a confocal laser scanning microscope. To determine the staining efficiency of staining dyes, hamatoxylin-eosin (H&E) and Masson's trichrome (MT) staining methods were performed for the histological analysis of bone-implant complex. We confirmed that the investigated embedding media showed good properties such as optimal mechanical strength appropriate for cutting the embedded block and proper staining efficiency for histological analysis. Therefore, the MMA/DBP/OA mixtures can be used as an embedding media appropriate for various hard tissues and bone-implant complex.

Facile synthesis of CeO2 nanoplates and nanorods by [1 0 0] oriented growth

This study demonstrated a facile method for the synthesis of CeO2 nanoplates and nanorods via the thermal decomposition of a mixture of cerium acetate, oleic acid, oleyamine and 1-octadecene under controlled atmospheres. Morphologies of the produced cerium oxides were controlled by the adding procedures of activators. Activators added at room temperature and heated with the reaction mixture result in the formation of nanoplates. Injection of activators at high temperature leads to the formation of nanorods. Both the nanoplates and nanorods are achieved via the [100] oriented assembly of smaller particles. A blue-shifting of the UV absorption threshold edge are observed for the cerium oxide nanoplates and nanorods, contrasting with the bulk commercial powders.

Chloroform- and Water-Soluble Sol–Gel Derived $\hbox{Eu}^{+++}/\hbox{Y}_{{\rm 2}}\hbox{O}_{{\rm 3}}$ (Red) and $\hbox{Tb}^{+++}/\hbox{Y}_{{\rm 2}}\hbox{O}_{{\rm 3}}$ (Green) Nanophosphors: Synthesis, Characterization, and Surface Modification

Eu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+++</sup> and Tb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+++</sup> ions have been incorporated into nanodimensional yttrium oxide host matrices via a sol-gel process using Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> O(OPr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sup> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sub> as precursor (OPr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sup> = isopropoxy). The as-synthesized white powders have been annealed at different temperatures. Photoluminescence (PL) spectroscopy and X-ray diffraction (XRD) have been used as tools for documenting the characteristics of these powders. For Eu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+++</sup> -doped powders, a comparison of the Eu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+++</sup> , <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> rarr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> , and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> rarr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> peak intensities in the emission spectra reveals that the dopant ions are occupying unsymmetrical sites in the host yttrium oxide in all the samples. For Tb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+++</sup> -doped powders, the characteristic terbium <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> rarr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> Drarr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> = 2-6) transitions were visible only in the samples that had been annealed above 500degC. Samples of the doped particle powders were suspended in chloroform by fragmenting the powder with and without sonification under the presence of trioctylphosphine oxide, or a mixture of oleic acid and dioctyl ether. The resulting clear colorless (for Eu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+++</sup> ) and light green translucent (for Tb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+++</sup> ) solutions of the suspended particles showed red and green luminescence upon UV excitation, respectively. In addition, suspension in water has been achieved by fragmenting the powder in the presence of dichloroacetic acid. Transmission electron micrograph investigation of the soluble particles shows single dispersed particles along with agglomerates. The changes in the luminescence due to fragmentation of the particle powder and due the influence of the surfactant of the suspended colloidal particles are discussed.

Synthesis of tungsten nanoparticles by solvothermal decomposition of tungsten hexacarbonyl

Abstract Tungsten nanoparticles were prepared by thermal decomposition of tungsten hexacarbonyl [W(CO) 6 ] (2 mmol) at 160 °C in presence of a mixture of (1:1) surfactants, oleic acid (6 mmol) and trioctyl phosphine oxide (TOPO) (6 mmol) under a blanket of Ar gas. The synthesized tungsten nanoparticles without surfactant are flocculated. With increase in concentration of surfactant mixture to 12 mmol each, agglomeration of several tungsten nanoparticles are observed. Characterization of surfactant coated tungsten nanoparticles were carried out using Fourier transform infrared spectroscopy (FTIR). Chemical characterizations of synthesized tungsten nanoparticles were done using X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectrometry (ICP-OES) and LECO gas analyzers. XPS study shows the W 0 oxidation state of tungsten nanopowders. Structural characterization of synthesized tungsten nanoparticles were conducted by X-ray diffraction (XRD), which shows that the as-synthesized tungsten nanoparticles are amorphous in nature and they become body centered cubic crystalline after annealing. Particle size, shape and distribution were characterized using small-angle X-ray scattering (SAXS), environmental scanning electron microscopy (ESEM) and transmission electron microscopy (TEM).

Influence of interactions on water and aroma permeabilities of ι-carrageenan–oleic acid–beeswax films used for flavour encapsulation

The objective of this work is to investigate the water and aroma barrier properties of films obtained from ι-carrageenan containing glycerol and lipids mixtures of oleic acid (OA) and beeswax (BW) used for encapsulation of active compounds. Water vapor permeability (WVP) is greatly influenced by lipid composition, encapsulated aroma compound and also relative humidity. WVP decreases when films contain encapsulated aroma compound but increases when the moisture content in the films increases. When oleic acid was the main compound of lipid phase, the plasticizing effect of water revealed through water permeability is less marked. The results of ethyl acetate, ethyl butyrate, ethyl hexanoate, 2-hexanone, 1-hexanol and cis-3-hexenol permeabilities reveal that physicochemical interactions between aroma compounds-hydrocolloid and aroma compound-lipid induce structural changes and modify their permeability. This work gives evidence of the ability of ι-carrageenan–OA–BW films to protect encapsulated aroma compound and its influence in barrier properties.

Systematic Study of the Properties of CdSe Quantum Dots Synthesized in Paraffin Liquid with Potential Application in Multiplexed Bioassays

High-quality CdSe quantum dots (QDs) were synthesized in a mixture of paraffin liquid and oleic acid (OA), and the effects of the synthetic conditions, including the growth temperature, precursor concentration, and initial OA:Cd molar ratio, on the optical properties of the as-prepared CdSe QDs were systematically investigated. The thermal stability and the effects of the nanocrystal (NC) purification on the optical properties of the as-prepared CdSe QDs were also studied for their further bioapplication. The results demonstrate that the CdSe QDs have good thermal stability and a high photoluminescence quantum yield (PLQY) after NC purification, which is very important for their bioapplication. Moreover, optically encoded microbeads have been successfully prepared by directly embedding the as-prepared oil soluble CdSe QDs into the carboxyl group-capped porous polystyrene (PS) beads through our route, which suggests their promising application in multiplexed bioassays.

Size- and shape-controlled synthesis and properties of colloidal PbSe nanocrystals

In this work, it has been demonstrated that the co-ordinating tri- n -octylphosphine and oleic acid mixture plays an essential role in the control of the growth, size distribution, colloidal stability, crystallinity and shape of the resulting PbSe nanocrystals. A systematic combination of the reaction and growth conditions allows the possibility to produce high quality PbSe nanocrystals over a broad range of diameters with narrow size distributions without any size selective precipitation techniques being applied. The capping agent/ligands helps to control the grain growth of the nanocrystals during its formation and increases the dispersibility of the nanocrystals, which can easily be manipulated and used for various applications in optoelectronics and microscopy.

Shape control of new FexO–Fe3O4and Fe1–yMnyO–Fe3–zMnzO4 nanostructures

AbstractNew nanoparticle shapes of iron oxide (FexOFe3O4, where 0.8 &lt; x &lt; 1) and iron‐manganese oxide (Fe1–yMnyOFe3–zMnzO4, where 0 &lt; y &lt; 1, and 0 &lt; z &lt; 3) were synthesized by decomposition of the corresponding metal formates in tri‐n‐octylamine/oleic acid mixtures at elevated temperatures (ca. 370 °C), under an inert atmosphere. Details of the syntheses leading to the various shapes of nanoparticles are provided as a function of the reactions parameters, that is, precursor type and concentration, surfactant concentration, water concentration, reaction time, and temperature. Different electron microscopy techniques were used to characterize the crystal phases and the novel shapes of these nanostructures. Nanoparticles of FexOFe3O4 were produced with different shapes, that is spheres, hexagons, and cubes, depending on the reaction conditions. By tuning the conditions, iron oxide nanocubes with concave faces were produced exclusively. Electron and X‐ray diffraction data reveal these nanocubes to be single‐crystal FexO (wüstite) with small amounts of Fe3O4 (magnetite). For the mixed metal system, solid solutions of Fe1–yMnyO with very small amounts of Fe3–zMnzO4 were observed, in which the produced oxide had a larger Fe:Mn ratio than present in the starting reagents. Adjusting the iron to manganese ratio in the mixed‐metal nanoparticles resulted in different shapes. Nanoparticles with ca. 1:1 (Fe:Mn) ratios displayed a ‘dog‐bone‐like’ morphology, which can be considered a shape in between a pure FexOFe3O4 nanocube and the rod‐like nanostructures previously reported for the manganese oxide system. In general, higher Fe:Mn ratios (e.g., 9:1) in the product resulted in nanostructures with cubic shapes, while lower Fe:Mn values (e.g., 2:8) resulted in long (ca. 200 nm) rod‐like nanostructures with flared ends. All of the nanostructures reported here exhibit internal structures that suggest a growth mechanism with etching on negatively curved rough crystal faces. Oxidation of the nanoparticles occurred with retention of their original shape.

Microstructure and optical properties of sodium caseinate films containing oleic acid–beeswax mixtures

The effect of internal and surface structure of films obtained from sodium caseinate (NaCas), containing glycerol and lipid mixtures of oleic acid (OA) and beeswax (BW) (1:0.3:0.5 protein:glycerol:lipid ratio) on optical properties (gloss and transparency) was studied. Gloss was measured at different angles of the incident light (20, 60 and 85°) using a gloss meter, and transparency was evaluated through Kubelka–Munt coefficients obtained from the film reflection spectra (400–700 nm). Film structure was analyzed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Control films (without lipid) exhibited the greatest transparency and gloss whereas lipid imparts opacity and loss of gloss to the film, especially as beeswax increased in the lipid mixture, due to the formation of greatest lipid aggregates in the internal and surface parts of the film. Good correlation was established among gloss, transparency and surface roughness parameters of the films.

Alpha-tocopheryl acetate is absorbed and hydrolyzed by Caco-2 cells: Comparative studies with alpha-tocopherol

Caco-2 cells were used as a model for investigating and comparing the absorption of alpha-tocopherol (Tol) and alpha-tocopheryl acetate (Tac) solubilized in micelles based on a mixture of sodium taurocholate (NaTC) and oleic acid. Surprisingly, the uptake of Tac was found to be similar to that of Tol, and in both cases, the dose-response plots suggest that protein-mediated transport processes were involved. Moreover Tol or Tac were also secreted into the basolateral medium of Caco-2 cells but Tac was mainly hydrolyzed either prior to absorption or intracellularly. The solubilization of Tol or Tac by NaTC on the apical side of the cell monolayer is a prerequisite for the uptake process, although larger amounts of the bile salt are necessary to solubilize Tac than Tol. Caco-2 cells showed hydrolytic activity on Tac, and additional cholesterol esterase may be taken up by the cells, thus increasing the rates of intracellular hydrolysis of Tac. Based on our findings, a scheme is suggested accounting for the absorption of alpha-tocopheryl acetate by enterocytes.

Characterization of novel cholesterol esterase from Trichoderma sp. AS59 with high ability to synthesize steryl esters

A novel cholesterol esterase with there and throughout to synthesisze steryl ester was obtained from the culture filtrate of a fungal strain Trichoderma sp. AS59 isolated from soil. The extracellular enzyme was a monomeric protein with a molecular mass of approximately 58 kDa and an isoelectric point of 4.3. The optimal temperature was between 35 degrees C and 40 degrees C, and the optimal pH was 7.0. The enzyme retained 75% of the initial activity after 18 h of incubation at 30 degrees C in the pH range of 3.5-7.5. Its relative hydrolytic activities on fatty acid cholesteryl esters were in the following order: butyrate (121%), linoleate (100%), caprylate (79%), myristate (42%), palmitate (38%), caproate (37%), and laurate (35%). Unlike mammalian pancreatic cholesterol esterase that is activated by primary cholates on hydrolysis of long-chain fatty acid cholesteryl esters, the enzyme from Trichoderma sp. AS59 displayed its basal activity and was not affected by cholate up to a concentration of 5 mM. At higher cholate concentrations the activity gradually decreased, but reincreased at about 40 mM to reach more than twice the basal activity at 100 mM. The enzyme exhibited a broad substrate specificity, being capable of hydrolyzing various fatty acid esters of not only cholesterol, but also methanol, glycerol, and p-nitrophenol. When incubated with a mixture of cholesterol and oleic acid of equal amounts, the enzyme achieved stoichiometrical esterification in 5 h, indicating its potential utility in food additives and liquid crystal devices.

Biocompatible Water-in-Oil Emulsion as a Model to Study Ascorbic Acid Effect on Lipid Oxidation

A biocompatible water-in-oil (W/O) emulsion has been used as a model to study the effect of ascorbic acid (AA) on the oxidation of the oil (glycerol trioleate, GTO) continuous phase. The model system consisted of 3 wt % water dispersed in GTO containing 0.5 wt % sodium oleate (NaO)/oleic acid (OA) mixture (NaO/OA = 20/80 mol/mol %) as a stabilizer. To study the ascorbic acid effect on GTO light-promoted oxidation, we added aqueous solutions of ascorbic acid to GTO in place of distilled water. Results obtained as peroxide values show that ascorbic acid activity depends on its concentration and it is affected by the characteristics of the W/O interface. In the presence of ascorbyl palmitate (AP) or sorbitan trioleate (Span 85) in the continuous phase, ascorbic acid activity increases in the first few hours of oxidation. The effect of ascorbic acid has been related to emulsion structure by calculating characteristic parameters of the droplet size distributions by means of optical microscopy.