Mojca Škerget

Phase equilibrium (solid-liquid-gas) in polyethyleneglycol-carbon dioxide systems

Phase equilibria (solid-liquid-gas) for polyethyleneglycol (with molar masses 1500, 4000, 8000 and 35 000 g mol−1) and carbon dioxide mixtures were determined. It was found that the S-L-V lines in P-T projection for all polyethyleneglycols studied show a temperature minimum and a temperature maximum. These phenomena have not been reported previously in the literature. If a reduced temperature (obtained by dividing the temperature of the solid-liquid transition under pressure by the melting point of PEG at 1 bar) is introduced, the S-L transition of all binary systems are represented by one line. The solubility of CO2 in liquid polyethyleneglycols is influenced by pressure and temperature, and is almost independent of the molecular mass of polyethyleneglycol. In a P-T projection, the vapour-liquid equilibrium is represented by a straight line if isopleths are plotted as a function of the reduced temperature. By combining the P-Tred projections of the S-L and L-V transitions, one master diagram can obtained which is valid for all binary mixtures of polyethyleneglycol and CO2 in the pressure and temperature range investigated.

Solvent extraction study of antioxidants from Balm (Melissa officinalis L.) leaves

In the paper, the extraction of antioxidants from Balm (Melissa officinalis L.) leaves with ethanol is presented. Effects of particle size, amount of solvent and temperature on the extraction rates and concentrations of antioxidants in the extracts were studied and kinetics was determined. Individual antioxidants (carnosic, ursolic and oleanolic acids) were identified by high performance liquid chromatography. Results showed that the intraparticle diffusion was the rate-governing step of the extraction process. The extractions all proceeded in three stages: an initial washing stage, a fast stage and a slower stage. Experimental extraction curves were analysed with a mathematical model derived from Ficks second law, and diffusion coefficients of the antioxidants within the particles under different operating conditions in ethanol were determined.

Hydrothermal reactions of agricultural and food processing wastes in sub- and supercritical water: a review of fundamentals, mechanisms, and state of research.

Hydrothermal (HT) reactions of agricultural and food-processing waste have been proposed as an alternative to conventional waste treatment technologies due to allowing several improvements in terms of process performance and energy and economical advantages, especially due to their great ability to process high moisture content biomass waste without prior dewatering. Complex structures of wastes and unique properties of water at higher temperatures and pressures enable a variety of physical-chemical reactions and a wide spectra of products. This papers aim is to give extensive information about the fundamentals and mechanisms of HT reactions and provide state of the research of agri-food waste HT conversion.

HIGH PRESSURE EXTRACTION OF VITAMIN E-RICH OIL FROM SILYBUM MARIANUM

Abstract The efficiency of high pressure extraction in the production of oil with a high concentration of vitamin E, from seeds of Silybum marianum , was investigated. The solvents used in extraction were liquid or supercritical carbon dioxide and liquid propane. Operating parameters were 100, 200, 300 bar and 25, 40, 60 and 80°C for CO 2 and 60, 150, 200 bar and 40, 60 and 80°C for propane, respectively. The influence of process parameters on the total yield of extraction, vitamin E composition and acid value of the extracts was investigated. Results were compared with those obtained for conventional extraction with organic solvents (n-hexane, petroleum ether, dichloromethane, chloroform). The mathematical model based on the adsorption–desorption equilibrium of oil from solid tissue, the diffusion of oil to the surface and mass transfer through external film into the bulk, described the experimental extraction results well.

Polyphenols: Extraction Methods, Antioxidative Action, Bioavailability and Anticarcinogenic Effects

Being secondary plant metabolites, polyphenols represent a large and diverse group of substances abundantly present in a majority of fruits, herbs and vegetables. The current contribution is focused on their bioavailability, antioxidative and anticarcinogenic properties. An overview of extraction methods is also given, with supercritical fluid extraction highlighted as a promising eco-friendly alternative providing exceptional separation and protection from degradation of unstable polyphenols. The protective role of polyphenols against reactive oxygen and nitrogen species, UV light, plant pathogens, parasites and predators results in several beneficial biological activities giving rise to prophylaxis or possibly even to a cure for several prevailing human diseases, especially various cancer types. Omnipresence, specificity of the response and the absence of or low toxicity are crucial advantages of polyphenols as anticancer agents. The main problem represents their low bioavailability and rapid metabolism. One of the promising solutions lies in nanoformulation of polyphenols that prevents their degradation and thus enables significantly higher concentrations to reach the target cells. Another, more practiced, solution is the use of mixtures of various polyphenols that bring synergistic effects, resulting in lowering of the required therapeutic dose and in multitargeted action. The combination of polyphenols with existing drugs and therapies also shows promising results and significantly reduces their toxicity.

Simultaneous extraction of oil- and water-soluble phase from sunflower seeds with subcritical water.

In this study, the subcritical water extraction is proposed as an alternative and greener processing method for simultaneous removal of oil- and water-soluble phase from sunflower seeds. Extraction kinetics were studied at different temperatures and material/solvent ratios in a batch extractor. Degree of hydrothermal degradation of oils was observed by analysing amount of formed free fatty acids and their antioxidant capacities. Results were compared to oils obtained by conventional methods. Water soluble extracts were analysed for total proteins, carbohydrates and phenolics and some single products of hydrothermal degradation. Highest amount of oil was obtained at 130 °C at a material/solvent ratio of 1/20 g/mL after 30 min of extraction. For all obtained oils minimal degree of hydrothermal degradation could be identified. High antioxidant capacities of oil samples could be observed. Water soluble extracts were degraded at temperatures ≥100 °C, producing various products of hydrothermal degradation.

Phase equilibria of the vitamins D2, D3 and K3 in binary systems with CO2 and propane

Solubilities of the fat-soluble vitamins K3, D3 and D2 in CO2 and propane were measured at temperatures 30, 40, 60 and 80°C and over a pressure range of 80–300 bar for CO2 and 10–110 bar for propane using a static-analytic method. In order to verify weather, the solubility isotherm crosses the three-phase S–L–V line, solid–liquid (S–L) phase transitions of vitamins K3, D3 and D2 under the pressure of gas were determined with modified capillary method. For all vitamins under the pressure of CO2, propane and dimethylether, a negative dP/dT slope of the S–L–V curve was found. For K3 under the pressure of inert gas (argon and nitrogen), the S–L–V-curve had a positive dP/dT slope. The solubilities of vitamins D in dense CO2 under the conditions investigated were in the range 0.04×10−3–1.45×10−3 mole fraction. For vitamin K3 the solubility in CO2 was higher and was in the range 0.16×10−3–4.07×10−3 mole fraction. The solubilities of vitamins D in propane were approximately up to 10 times higher as in CO2 and in the range from 0.15×10−3 to 12.40×10−3 mole fraction. Opposite, the solubility of vitamin K3 in propane was lower than in CO2 and was in the range from 0.03×10−3 to 2.99×10−3 mole fraction. The experimental S–L–V data were correlated using Peng-Robinson equation of state and binary iteration parameters obtained from best fit were used for solubility calculation. The fit of S–L–V lines showed good results in the case of vitamin K3 and the order of magnitude of the solid solubilities were well represented.

Phase equilibria in systems containing α-tocopherol and dense gas

Abstract Solubility of α-tocopherol in CO 2 and propane was determined at temperatures 303, 313, 333 and 353 K and over a pressure range from 79 to 286 bar for CO 2 and 16 to 112 bar for propane. A static-analytic method was applied. The solubility of α-tocopherol in dense CO 2 under the conditions investigated was in the range of 0.2–17.0 mg/g CO 2 . The maximal solubilities of α-tocopherol in propane were approximately up to ten times higher than in CO 2 and were in the range from 38.9 to 171.9 mg/g propane. Phase equilibrium data for Milk Thistle seed oil in supercritical CO 2 were determined at temperatures 313, 333 and 353 K and pressures ranging from 100 to 300 bar. The oil was previously additionally vitaminized and contained 1.9 wt.% of α-tocopherol and 1.7 wt.% of free fatty acids (FFA). The solubility of oil in CO 2 was in the range from 1.3 to 17.9 mg/g CO 2 . The distribution coefficients of α-tocopherol and FFA between light and heavy phase were determined on a solvent free basis. The obtained separation factors increased with temperature and pressure to approximately 160–200 bar and decreased with a further increase of pressure.

Rosemary extracts improve flow-mediated dilatation of the brachial artery and plasma PAI-1 activity in healthy young volunteers.

Polyphenol antioxidants decrease the risk of atherosclerosis. The study aimed to evaluate prospectively in healthy young participants the effect of oral rosemary extracts (RE), consisting of diphenols, upon endothelial dysfunction (ED), preceding structural atherosclerosis. Nineteen healthy young volunteers were studied prospectively, who received oral RE (77.7 mg) for 21 days, consisting of active substances carnosol (0.97 mg), carnosic (8.60 mg) and rosmarinic acid (10.30 mg). Before and after RE treatment, the study evaluated fasting serum levels of plasminogen‐activator‐inhibitor‐1 (PAI‐1), vascular cell adhesion molecule 1 (VCAM‐1), inter‐cellular adhesion molecule 1 (ICAM‐1), superoxide dismutase (SOD), glutathione peroxidase (GPX), fibrinogen, high‐sensitivity capsular reactive protein (hs‐CRP), tumor‐necrosis factor α (TNF‐α), the lipid profile and ED, characterized as flow‐mediated dilatation (FMD) in the brachial artery of <4.5%, estimated by ultrasound measurements. After 21 days, any side effects were registered, the mean FMD increased nonsignificantly (6.51 ± 5.96% vs 7.78 ± 4.56%, p = 0.546) and ED decreased significantly (66.6% vs 16.6%, p = 0.040). Among the serum markers, only the mean PAI‐1 level decreased significantly (4.25 ± 1.46 U/mL vs 3.0 ± 0.61 U/mL, p = 0.012) after 21‐day RE supplementation. It is concluded that oral RE supplementation has the potential to improve serum PAI‐1 activity and ED in young and healthy individuals. Copyright

Particle Formation and Product Formulation Using Supercritical Fluids

Traditional methods for solids processing involve either high temperatures, necessary for melting or viscosity reduction, or hazardous organic solvents. Owing to the negative impact of the solvents on the environment, especially on living organisms, intensive research has focused on new, sustainable methods for the processing of these substances. Applying supercritical fluids for particle formation may produce powders and composites with special characteristics. Several processes for formation and design of solid particles using dense gases have been studied intensively. The unique thermodynamic and fluid-dynamic properties of supercritical fluids can be used also for impregnation of solid particles or for the formation of solid powderous emulsions and particle coating, e.g., for formation of solids with unique properties for use in different applications. We give an overview of the application of sub- and supercritical fluids as green processing media for particle formation processes and present recent advances and trends in development.