Surface tension of ethanol in supercritical CO2

Mechanism of multicyclic β-carotene impregnation into corn starch aerogels via supercritical CO2 with mathematical modeling

β-carotene, a natural dye renowned for its antioxidant and provitamin A activities, is hindered from direct use in food and drug products due to its susceptibility to oxidation, easy isomerization under light, heat, or acidic conditions, as well as its low water solubility and oral bioavailability. In this study, we addressed these challenges by loading β-carotene into corn starch aerogels via supercritical carbon dioxide (sc-CO2) and assessed its loading contributions through adsorption during contact time and precipitation during depressurization. The loading process was studied under two cycles at pressure of 30 MPa, temperature of 40 °C, depressurization rate of 0.4 MPa/min, and co-solvent (ethanol) mass percentage of 1.2 %. Experiments found adsorption minimally contributed to impregnation, while precipitation became the primary loading mechanism. The subsequent work focused on a mathematical model describing β-carotene loading into corn starch aerogels via precipitation, using the law of conservation of mass and classical nucleation theory. The model shows that using pure CO2 results in a loading efficiency of 0.10 mg β-carotene/g aerogel, while with CO2 and 1.2 % ethanol as the co-solvent, the loading efficiency increases threefold to 0.30 mg β-carotene/g aerogel.

Fluid phase interface properties of acetone, oxygen, nitrogen and their binary mixtures by molecular simulation

Vapor–liquid equilibria (VLE) of the pure substances acetone, oxygen and nitrogen as well as their binary mixtures are studied by molecular dynamics (MD) simulation with a direct approach.

Reverse aqueous microemulsions in hydrofluoroalkane propellants and their aerosol characteristics

In this work we describe the structure and environment of reverse aqueous microemulsions formed in 1,1,1,2-tetrafluoroethane (HFA134a) propellant in the presence of a non-ionic ethoxylated copolymer, and the aerosol characteristics of the corresponding pressurized metered dose inhaler (pMDI) formulations. The activity of selected polypropylene oxide-polyethylene oxide-polypropylene oxide (PO(m)EO(n)PO(m)) amphiphiles at the HFA134a-water interface was studied using in situ high-pressure tensiometry, and those results were used as a guide in the selection of the most appropriate candidate surfactant for the formation of microemulsions in the compressed HFA134a. The environment and structure of the aggregates formed with the selected surfactant candidate, PO(22)EO(14)PO(22), was probed via UV-vis spectroscopy (molecular probe), and small angle neutron scattering (SANS), respectively. High water loading capacity in the core of the nanoaggregates was achieved in the presence of ethanol. At a water-to-surfactant molar ratio of 21 and 10% ethanol, cylindrical aggregates with a radius of 18Å, and length of 254Å were confirmed with SANS. Anderson Cascade Impactor (ACI) results reveal that the concentration of the excipients (C(exp), including surfactant, water and ethanol) has a strong effect on the aerosol characteristics of the formulations, including the respirable fraction, and the mass mean aerodynamic diameter (MMAD), and that the trend in MMAD can be predicted as a function of the C(exp) following similar correlations to those proposed to common non-volatile excipients, indicating that the nanodroplets of water dispersed in the propellant behave similarly to molecularly solubilized compounds. Cytotoxicity studies of PO(22)EO(14)PO(22) were performed in A549 cells, an alveolar type II epithelial cell line, and indicate that, within the concentration range of interest, the surfactant in question decreases cell viability only lightly. The relevance of this work stems from the fact that aqueous-based HFA-pMDIs are expected to be versatile formulations, with the ability to carry a range of medically relevant hydrophilic compounds within the nanocontainers, including high potency drugs, drug combinations and biomacromolecules.

Supercritical Fluid Pasteurization and Food Safety

Supercritical fluid pasteurization has been studied for over 20 years and the state of science and technology is such that it is now a viable and economical alternative to thermal pasteurization for a number of food products. The manufacture and distribution of food faces increasingly strict demands in terms of both safety and quality. Traditional thermal pasteurization is both effective and well-accepted by the public for milk and other products. However, thermal treatment is less effective and sometimes infeasible for certain products, such as fruit juices, seafoods and fresh vegetables. This is particularly true when the food products are packaged and shipped long distances. Supercritical fluid technology, a non-thermal, low temperature process, has been shown to reduce the viability of a number of pathogenic organisms important to the food industry. In addition, supercritical fluids, particularly CO2, have promise in deactivating subcellular pathogens such as prions and viruses. Numerous basic science investigations reveal the mechanism of supercritical fluid pasteurization and how it differs from thermal methods. Several commercial companies have issued patents and built demonstration plants based on the technology. In addition, certain supercritical fluids may provide additional benefits for food processors. This chapter provides a comprehensive review of both science and technology of supercritical fluid technology as applied to foods.

Supercritical antisolvent production of biodegradable micro- and nanoparticles for controlled delivery of paclitaxel

Paclitaxel and poly (L-Lactic acid) (PLA) were co-precipitated to form micro and submicron particles in a manner similar to that used in the supercritical antisolvent with enhanced mass transfer (SAS-EM) process. As compared with conventional processes, a major advantage of supercritical CO(2) as an antisolvent in the SAS-EM process is the effective removal of residual organic solvents. In this work, the organic phase was sprayed into supercritical CO(2) (for CO(2), Tc=31.1 degrees C, Pc=73.8 bar) from a 500 microm ID capillary nozzle. Ultrasonic vibration with an amplitude of 0 to 120 microm (from a 3/8'' tip diameter titanium probe) was employed in the high pressure vessel during the antisolvent process to provide enhanced mixing between the solvent and antisolvent phases. The role and effects of ultrasonication on the properties of the resulting particles were studied. When no ultrasonication was applied, micrometer-sized particles were obtained. When ultrasonication was applied, more uniform particles in the submicron size range were obtained. The size of the particles was found to vary with the ultrasonic vibration amplitude. Encapsulation efficiencies up to 83.5% and controlled release of paclitaxel for more than 30 days were achieved with the particles fabricated in this study.

Monte Carlo Simulation of Equilibrium Reactions at Vapor−Liquid Interfaces

Chemical reactions are known to behave differently, depending upon their local environment. While the interactions with neighboring molecules may alter both the kinetics of chemical reactions and the overall equilibrium conversion, we have performed simulations of the latter. The particular environment that we address is the vapor-liquid interface, since only a few, limited studies have explored the influence of an interface on equilibrium reaction behavior. Simple dimerization reactions are modeled, as well as more complex multicomponent reactions, using the reactive Monte Carlo (RxMC) simulation technique. We find that the conversion of a reaction can be markedly different at an interface as compared to the bulk vapor and liquid phases, and these trends are analyzed with respect to specific intermolecular interactions. In conjunction, we calculate the surface tension of the reacting fluids at the interface, which is found to have unusual scaling behavior, with respect to the system temperature.