Mean Aspects Controlling Supercritical CO₂ Precipitation Processes

The use of supercritical CO2 is an excellent alternative in extraction, particle precipitation, impregnation and reaction processes due to its special properties. Solubility of the compound in supercritical CO2 drives the precipitation process in different ways. In supercritical antisolvent process, mass and heat transfers, phase equilibria, nucleation, and growth of the compound to be precipitated are the main phenomena that should be taken into account. Mass transfer conditions the morphology and particle size of the final product. This transfer could be tuned altering operating conditions. Heat transfer in non-isothermal process influences on mixing step the size of generated microparticles. In rapid expansion of supercritical solution, phenomena as the phase change from supercritical to a CO2 gas flow, rapid mass transfer and crystallization of the compound, and expansion jet define the morphology and size of the final product. These phenomena a priori could be modulated tuning a large number of operating parameters through the experiments, but the correlations and modeling of these processes are necessary to clarify the relative importance of each one. Moreover, particle agglomeration in the expansion jet and CO2 condensation are determinant phenomena which should be avoided in order to conserve fine particles in the final product

High-Pressure fractionation of tropical fruits with potential antibacterial activity: M. indica L. and B. Guineensis

The great interest in the potential health benefits of tropical fruits is due to their high content of antioxidants and phytochemicals. Colombia ranks as the second country with the major biodiversity worldwide. B. guineensis (Arecaceae) is a palm that grows in Colombia and Central America. The purple-black fruits of this plant are rich in thermal-stable anthocyanins. M. indica L. (Anacardiaceae) is a great source of phenolic compounds. It has multiple functional properties including antioxidant, antimicrobial, antidiabetic and anticarcinogenic activities. In this work, high-pressure extraction techniques: supercritical fluid extraction (SFE) and enhanced solvent extraction (ESE), and two different fractionation techniques: i) cascade fractionation and ii) sequential fractionation were applied. Fractions were analyzed by means of their phenolic content, antioxidant activity, and antibacterial activity against different bacterial strains: E. coli, P. mirabilis, S. Aurerus, S. enteritidis, E. aerogenes and P. aeruginosa. The sequential fractionation of B. guineensis pulp consisted in three steps: 1) supercritical CO2, 2) CO2 + 50% ethanol, and 3) CO2/EtOH/H2O (50:25:25). A red fraction rich in phenolic compounds, high antioxidant and antibacterial capacity (inhibition zone ~ 10 mm) was obtained in the last step. A cascade fractionation of M. indica leaves using CO2 + 50% H2O and three separators (S1, S2 and S3) was evaluated. Fractions obtained in S1 and S2 presented antioxidant capacity and antibacterial activity against P. mirabilis, and S2 also against S. Aureus and Salmonella

Application of a Natural Antioxidant from Grape Pomace Extract in the Development of Bioactive Jute Fibers for Food Packaging

There is an increasing demand for the use of new food packaging materials. In this study, natural jute fibers impregnated with a Petit Verdot Red Grape Pomace Extract (RGPE) was proposed as a new active food packaging material. Pressurized Liquid Extraction (PLE) and Enhanced Solvent Extraction (ESE) techniques were employed to obtain the bioactive RGPE. Afterward the supercritical solvent impregnation conditions to obtain RGPE-natural jute fibers were studied, by varying pressure, modifier percentage and dried RGPE mass. PLE technique offered the highest bioactive extract at 20 MPa, 55 degrees C, 1 h residence time using C2H5OH:H2O (1:1 v/v), providing an EC50 of 3.35 +/- 0.25 and antibacterial capacity against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa (MIC of 12.0, 1.5 and 4.0 mg/mL RGPE respectively). The natural jute fibers impregnated with 3 mL of that RGPE (90 mg/mL) at 50 MPa and 55 degrees C generated the most efficient packing material with regards to its food preservation potential

Biobased films of nanocellulose and mango leaf extract for active food packaging: supercritical impregnation versus solvent casting

Antioxidant and antimicrobial free-standing films composed of nanofibrillated cellulose (NFC) and a polyphenolic-rich extract, viz. mango leaf extract (MLE), were produced via supercritical solvent impregnation (SSI) and conventional solvent casting film-processing methodologies. The CO2-assisted impregnation of NFC with MLE created robust films with thermal stability up to 250 °C, good mechanical performance (Young's modulus > 4.7 GPa), UV-light barrier properties, antioxidant capacity with maximum inhibition percentage of ca. 84%, and antimicrobial activity against Staphylococcus aureus (growth inhibition ≈ 37%) and Escherichia coli (growth inhibition ≈ 91%). The comparison of the NFC/MLE films prepared by SSI with those fabricated via solvent casting shows a clear advantage of the SSI methodology. Particularly, the antioxidant and antimicrobial activities are visibly higher in the films fabricated by the CO2-assisted impregnation of MLE into NFC. In fact, for the SSI films, the MLE components are mostly adsorbed at the surface and not in the bulk of the biopolymeric matrix, which translates into faster migrations and, hence, higher active properties. All these findings evinced the potential performance of the NFC/MLE films prepared by the eco-friendly SSI as UV-blocking, antioxidant, and antimicrobial bio-based materials for application as sustainable active food packaging.publishe

The evolution of the ventilatory ratio is a prognostic factor in mechanically ventilated COVID-19 ARDS patients

Background: Mortality due to COVID-19 is high, especially in patients requiring mechanical ventilation. The purpose of the study is to investigate associations between mortality and variables measured during the first three days of mechanical ventilation in patients with COVID-19 intubated at ICU admission. Methods: Multicenter, observational, cohort study includes consecutive patients with COVID-19 admitted to 44 Spanish ICUs between February 25 and July 31, 2020, who required intubation at ICU admission and mechanical ventilation for more than three days. We collected demographic and clinical data prior to admission; information about clinical evolution at days 1 and 3 of mechanical ventilation; and outcomes. Results: Of the 2,095 patients with COVID-19 admitted to the ICU, 1,118 (53.3%) were intubated at day 1 and remained under mechanical ventilation at day three. From days 1 to 3, PaO2/FiO2 increased from 115.6 [80.0-171.2] to 180.0 [135.4-227.9] mmHg and the ventilatory ratio from 1.73 [1.33-2.25] to 1.96 [1.61-2.40]. In-hospital mortality was 38.7%. A higher increase between ICU admission and day 3 in the ventilatory ratio (OR 1.04 [CI 1.01-1.07], p = 0.030) and creatinine levels (OR 1.05 [CI 1.01-1.09], p = 0.005) and a lower increase in platelet counts (OR 0.96 [CI 0.93-1.00], p = 0.037) were independently associated with a higher risk of death. No association between mortality and the PaO2/FiO2 variation was observed (OR 0.99 [CI 0.95 to 1.02], p = 0.47). Conclusions: Higher ventilatory ratio and its increase at day 3 is associated with mortality in patients with COVID-19 receiving mechanical ventilation at ICU admission. No association was found in the PaO2/FiO2 variation

Quality of Cosmetic Argan Oil Extracted by Supercritical Fluid Extraction from Argania spinosa L.

Argan oil has been extracted using supercritical CO2. The influence of the variables pressure (100, 200, 300, and 400 bar) and temperature (35, 45, 55°C) was investigated. The best extraction yields were achieved at a temperature of 45°C and a pressure of 400 bar. The argan oil extracts were characterized in terms of acid, peroxide and iodine values, total tocopherol, carotene, and fatty acids content. Significant compositional differences were not observed between the oil samples obtained using different pressures and temperatures. The antioxidant capacity of the argan oil samples was high in comparison to those of walnut, almond, hazelnut, and peanut oils and comparable to that of pistachio oil. The physicochemical parameters of the extracted oils obtained by SFE, Soxhlet, and traditional methods are comparable. The technique used for oil processing does not therefore markedly alter the quality of argan oil

Green Extraction of Antioxidants from Different Varieties of Red Grape Pomace

The extraction yield, phenolic content, anthocyanin content and antioxidant activity of extracts from different varieties of red grapes, Cabernet Sauvignon, Merlot, Petit Verdot, Syrah, Tempranillo and Tintilla, using pressurized green solvents have been analyzed. Two techniques were studied and compared: supercritical fluid extraction (SFE) with CO2 + 20% ethanol and pressurized liquid extraction (PLE) with either ethanol, water or an ethanol/water mixture as the extraction solvents. The Petit Verdot variety allowed the highest global and phenolic yield, and antioxidant activity. The best conditios for PLE obtained from the experimental design and kinetic study were 50% ethanol/water as the pressurized solvent at 90 bar, 120 °C, a flow rate of 5 g/min and, an extraction time of 90 min. A statistical analysis of variance has been performed and it was found that temperature is the only variable that has a statistical influence on the extraction yield. The antioxidant activity levels of the extracts are very promising and they are similar to those obtained with the antioxidant tocopherol

High Pressure Extraction of Antioxidants from Solanum stenotomun Peel

In the work described here, two techniques for the recovery of anthocyanins from potato peel were studied and compared. One of the techniques employed was supercritical fluid extraction (SFE) with pure CO2 or with CO2 and ethanol as cosolvent and the other technique was pressurized liquid extraction (PLE), where the solvent used was ethanol in water acidified to pH 2.6. The effects of pressure and temperature were studied and the anthocyanin contents obtained were statistically analyzed. In SFE the use of low pressure (100 bar) and high temperature (65 °C) was desirable for the anthocyanin extraction. With PLE the anthocyanin contents are increased considerably, and the best yields were obtained at 100 bar and 80 °C. This result is in correspondence with antioxidant activity index values (1.66) obtained in a DPPH antioxidant activity assay. In the extracts obtained with PLE the phenolic compounds were also determined, but the main compounds presented in the extract are anthocyanins