Deacidification of olive oils by supercritical carbon dioxide

An investigation of the application of supercritical carbon dioxide (SC-CO₂) extraction to the deacidification of olive oils has been made to verify that the nutritional properties of the oil remain unchanged when this technique is applied. Preliminary runs at 20 and 30 MPa in the temperature range of 35–60°C were performed on fatty acids and triglycerides as pure compounds or mixtures, to determine their solubility in SC-CO₂. The solubility data obtained show that CO₂ extracts fatty acids more selectively than triglycerides under specific conditions of temperature and pressure (60°C and 20 MPa). It has been noted that the physical state of the solutes plays an important role in determining the solubility trends as a function of temperature and pressure. Extraction of free fatty acids from olive oil was performed on samples with different free fatty acid (FFA) contents at 20 and 30 MPa and at 40 and 60°C. Experimental data suggest that the selectivity factor for fatty acids is higher than 5 and increases significantly as the fatty acid concentration of the oil decreases. For a FFA content of 2.62%, the selectivity reaches a value of 16. In order to evaluate any variations in the composition, several SC-CO₂ extractions of husk oil with high FFA content (29.3%) were made. The results show that selectivity is still significant (≈5) and the composition in the minor component of the deacidified oil has not changed. On the basis of the experimental results and preliminary process evaluations, the authors conclude that SC-CO₂ extraction could be a suitable technique for the deacidification of olive oils, especially for oils with relatively high FFA (<10%).     

Flavour compounds of Lavandula angustifolia L. to use in food manufacturing: Comparison of three different extraction methods

Sixty compounds of Lavandula angustifolia L. cultivated in Friuli Venezia Giulia (North-East Italy) were identified and quantified by GC-MS and GC-FID from essential oils obtained by means of hydrodistillation, and from extracts obtained by supercritical CO₂ extraction (SFE) and ultrasound-assisted extraction (US). Using absolute calibration, a true quantification of 1-8 cineol, camphor, linalool, linalyl acetate and β-caryophyllene was carried out. The best extracts, in terms of amount of isolated compounds, flavour quality and stability were those obtained with SFE. Sonication performed at low amplitude for 5 min offered respect to high amplitude a promising alternative to hydrodistillation as a source of lavender flavouring ready to use for alcoholic beverages or/and confectionery products.     

Influence of operating parameters on selectivity in a separation process by liquid membrane permeation for the system styrene-ethylbenzene

An experimental comparative analysis of various factors involved in the separation of styrene-ethylbenzene mixtures by liquid membrane permeation was performed. The choice of the proper surfactant and the influence of the ratio surfactant/solvent/feed and of the operating parameters were investigated. An attempt is made to interpret the experimentally determined characteristics of the system on the basis of a diffusive model adapted to this kind of separation.     

UNIFAC and infinite dilution activity coefficients

This paper deals with the possibility of estimating UNIFAC parameters from infinite dilution activity coefficients. Such activity coefficients can be obtained from gas chromatographic measurements (GLC). In some cases the original UNIFAC equations do not represent very well the variations of the activity coefficients with the concentration in the very dilute regions. It is then not possible to estimate reliable parameters from infinite dilution activity coefficients alone. It is shown that a recent modification of the combinatorial part of the UNIFAC equations allows for the estimation of UNIFAC parameters from infinite dilution activity coefficients for alkane—-ketone, alkane—-alcohol, and other mixtures.     

The liquid—liquid equilibrium for activity coefficient determination

A method based on liquid—liquid equilibrium is proposed for the determination of activity coefficients. The reliability of this procedure is tested on the systems cyclohexane—benzene, cyclohexane—toluene, n-hexane—benzene, n-heptane—toluene.     

Preparation of Theophylline-Hydroxypropylmethylcellulose Matrices Using Supercritical Antisolvent Precipitation: A Preliminary Study

ABSTRACT

Several controlled release systems of drugs have been elaborated using a supercritical fluid process. Indeed, recent techniques using a supercritical fluid as a solvent or as an antisolvent are considered to be useful alternatives to produce fine powders. In this preliminary study, the effect of Supercritical Anti Solvent process (SAS) on the release of theophylline from matrices manufactured with hydroxypropylmethylcellulose (HPMC) was investigated. Two grades of HPMC (HPMC E5 and K100) as carriers were considered in order to prepare a sustained delivery system for theophylline which was used as a model drug. The characterization of the drug before and after SAS treatment, and the coprecipitates with carriers, was performed by X-ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC). The dissolution rate of theophylline, theophylline-coprecipitates, and matricial tablets prepared with coprecipitates were determined. The physical characterizations revealed a substantial correspondence of the drug solid state before and after supercritical fluid treatment while drug-polymer interactions in the SAS-coprecipitates were attested. The dissolution studies of the matrices prepared compressing the coprecipitated systems showed that the matrices based on HPMC K100 were able to promote a sustained release of the drug. Further, this advantageous dissolution performance was found to be substantially independent of the pH of the medium. The comparison with the matrices prepared with untreated substances demonstrated that matrices obtained with SAS technique can provide a slower theophylline release rate. A new mathematical model describing the in vitro dissolution kinetics was proposed and successfully tested on these systems.     

Plasticization of polymers with supercritical carbon dioxide: Experimental determination of glass‐transition temperatures

High‐pressure partition chromatography, a modification of the inverse gas chromatography technique, is presented as suitable technique for the study of the plasticization effect of carbon dioxide on the following polymers: poly(methyl methacrylate), polystyrene, and bisphenol A–polycarbonate. Polymers in the presence of a compressed gas or a supercritical fluid become plasticized; this means that their glass‐transition temperatures (T_g's) can be lowered by 10s of degrees, which causes changes in their mechanical and physical properties. CO₂‐induced plasticization has an important impact on many polymer processing operations in which the T_g depressions of the polymers can be evaluated. The experimental results are discussed and compared with data available from literature for each polymer we considered. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2189–2193, 2003     

Liquid-liquid equilibrium for the activity coefficient determination: Effect of mutual solubility between binary systems and auxiliary solvents

The method proposed earlier by the authors for the determination of activity coefficients by liquid-liquid equilibrium using water as auxiliary solvent is extended by making use of other solvents. The effect of mutual solubility on the determination of activity coefficients is discussed. A correction to be applied to the experimental data is proposed, and the activity coefficients so obtained are thermodynamically consistent. The method can be applied not only to hydrocarbon mixtures, but also to solute-polar solvent mixtures.