Supercritical CO2 and low-pressure solvent extraction of mango (Mangifera indica) leaves: Global yield,extraction kinetics,chemical composition and cost of manufacturing

Low-pressure solvent extraction (LPSE) and supercritical fluid extraction (SFE) were used to obtain extracts from mango (Mangifera indica) leaves. Kinetics curves were determined for both methodologies. The extracts chemical compositions and manufacturing costs were determined for both processes. Global yield isotherms for SFE process were determined at 10–40 MPa and 313–323 K. The highest yield was 2.24% at 30 MPa and 323 K; the LPSE yield (9.3%) was almost three times higher than that of SFE (3.6%). Thin layer chromatography showed that mango leaves extracts have several classes of compounds as alkaloids, flavonoids and terpenoids, recovered by both methods. The cost of manufacturing (COM) mango leaves extracts were US$ 32/kg and US$ 92/kg for LPSE and SFE, respectively.     

Supercritical fluid extracts from tamarillo (Solanum betaceum Sendtn) epicarp and its application as protectors against lipid oxidation of cooked beef meat

The possibility of using the tamarillo (Solanum betaceum (Cav.) Sendtn (syn. Cyphomandra betacea)) epicarp as source of compounds with antioxidant activity in cooked beef meat (CBM) was explored. Extracts from tamarillo by supercritical fluid extraction (SFE) and Soxhlet extraction (SE) were obtained. The SFE was performed using pure CO₂ at different temperatures and pressures (40 and 50 °C; 10, 20 and 30 MPa) and CO₂ added with ethanol (CO₂/EtOH) as co-solvent (2, 5 and 8%, w/w). The SFE kinetics and mathematical modeling of the overall extraction curves (OEC) were also investigated. EtOH and hexane were used in the SE. The antioxidant activity (AA) of extracts was evaluated in CBM as well as the protection against lipid oxidation was determined by measuring lipid hydroperoxides (LHP) and thiobarbituric acid reactive species (TBARS). The extract obtained by SFE with CO₂/EtOH (50 °C/30 MPa and 2% of EtOH) showed the highest AA. In SFE, the co-solvent addition improved considerably the AA and the extraction yield. The extracts obtained by SFE with CO₂/EtOH showed a better AA compared with the synthetic antioxidant TBHQ. The highest yield values were achieved by SE with ethanol (7.7 ± 0.4%) and by SFE with 5% EtOH (1.9 ± 0.1%). The results indicate that extracts of tamarillo epicarp are a potential source of antioxidant compounds.     

Enrichment of Nigella damascena extract with volatile compounds using supercritical fluid extraction

β-Elemene, germacrene A and damascenine were extracted from lady-in-a-mist (Nigella damascena L.) seeds with supercritical carbon dioxide at 10–30 MPa and 40–60 °C. The influence of supercritical fluid extraction (SFE) conditions on the yield and concentration of volatiles in the extract and the extraction kinetics were studied. The extraction yields and the apparent solubility of volatile compounds increased with increasing density of CO₂. The highest total yield was obtained at 30 MPa and 40 °C but the selectivity for volatiles was low under these conditions. With respect to both yield of volatiles and their concentration in extract, the best results were at 12 MPa and 40 °C, either with one separator or with additional separator maintained at 5 MPa and 25 °C. The yields of β-elemene, germacrene A and damascenine reached 0.72, 3.31 and 3.65 mg g⁻¹ and their concentration in the extract was 2.62, 12.04 and 13.28 wt.%, respectively. Though the yields of germacrene A and damascenine were by about 20% higher using Soxhlet extraction with hexane than using SFE, their concentration in the extract where fatty oil prevailed was only 1.19 and 1.20 wt.%, respectively. Under the conditions of hydrodistillation, partial conversion of germacrene A to β-elemene occurred and its yield was higher than using the other methods but the composition of volatiles in the SFE extracts better corresponds to the original raw material.     

Production of polyphenol extracts from grape bagasse using supercritical fluids: Yield,extract composition and economic evaluation

The objective of this work was to determine the economic feasibility of large-scale operations of supercritical fluid extraction (SFE) for the recovery of phenolics using grape bagasse from Pisco residues. Experimental data were used to estimate the extraction kinetic parameters, as well as the cost of manufacturing the extracts. Experimental data were obtained using supercritical CO₂ containing 10% ethanol (w/w) at 313 K and 20–35 MPa. The supercritical CO₂/ethanol extraction process produced extracts with higher concentrations of phenolics than extracts produced using conventional techniques. The compounds identified in the extracts were syringic, vanillic, gallic, p-hydroxybenzoic, protocatechuic and p-coumaric acids, as well as quercetin. An evaluation of the economics of the process indicated the feasibility of an industrial SFE plant with a capacity of 0.5 m³ for producing an extract with an expected phenolics concentration of approximately 23 g/kg of extract at an estimated cost of manufacturing of US$ 133.16/kg.     

Extraction of low-molar-mass phenolics and lipophilic compounds from Pinus pinaster wood with compressed CO2

Near-supercritical and supercritical CO₂ was used to extract low-molar-mass phenolics and lipophilic compounds from Pinus pinaster wood. Extraction of samples containing sapwood and knotwood was carried out at 10⿿25 MPa and 30⿿50 °C to assess the influence of the operational conditions on the yields of total extracts and phenolics, as well as on the radical scavenging capacity of extracts. The use of ethanol as a co-solvent increased both the extraction yields and the concentration of phenolics in extracts. Operating under selected conditions (25 MPa, 50 °C, 10% ethanol), the extraction yield accounted for 4.1 wt% of the oven-dry wood. The extracts contained up to 7.6 g of phenolic compounds (measured as gallic acid equivalents) per 100 g extract, and showed one third of the radical scavenging capacity of Trolox. Native resin acids accounted for about 24 g per 100 g extracts, whereas flavonoids, lignans, stilbenes and juvabiones were found at lower proportions.     

Supercritical carbon dioxide extraction of Capsicum peppers: Global yield and capsaicinoid content

The objective of this study was to select a variety of pepper with high concentration of capsaicin and subject it to supercritical fluid extraction (SFE), in order to determine the best conditions of temperature (40, 50 and 60 °C) and pressure (15, 25 and 35 MPa) in terms of global yield (X₀) and capsaicinoids content of the extracts. The influence of drying process (freeze and oven drying) on X₀, capsaicin (C) and dihydrocapsaicin (DHC) contents and total phenolics was also analyzed. Capsicum frutescens showed the highest levels of capsaicinoids (1516 μg/g fresh fruit). For the responses C and DHC, the extraction conditions of 15 MPa and 40 °C provided the highest concentrations (C ⿿ 42 mg/g extract and DHC ⿿ 18.5 mg/g extract). The freeze drying process resulted in extracts with the highest concentration of capsaicinoids (61 mg/g extract), but in contrast, the phenolics were less susceptible to different drying processes, with a mean concentration of 35 mg GAE/g extract. The kinetics experiments indicated that the extraction rate of oleoresin was slightly slower than that of capsaicinoids at the operation conditions (40 °C and 15 MPa).     

Extraction of essential oil from Cyperus articulatus L. var. articulatus (priprioca) with pressurized CO2

The main goal of this study was to assess the yield and the antimicrobial activity of extracts from Cyperus articulatus L. var. articulatus obtained by pressurized carbon dioxide based on their system phase diagram behavior. The extractions were carried out at 313, 323, 333 K temperatures and, 13 and 25 MPa pressures. The extracts were quantified and chemically characterized by using gas chromatography coupled to mass spectrometry technique. The extracts obtained at the following experimental conditions: 333 K and 13 MPa, showed antifungal activity against Cladosporium sphaerospermum ATCC 4464. At 323 K – 25 MPa, and 333 K – 25 MPa, the extracts showed antibacterial activity against Staphylococcus aureus ATCC 25923. To describe the kinetics of extraction with a packed bed, a mathematical model was employed highlighting the transference mechanisms for masses in the pseudo-binary system as follows (1) carbon dioxide and (2) priprioca extract, the monophasic and multiphasic regions.     

Supercritical CO2 extraction of Plumula nelumbinis oil: Experiments and modeling

Supercritical CO₂ extraction of Plumula nelumbinis oil was investigated at temperatures of 308–338 K and pressures of 15–45 MPa. The yield of the extracted oil was 0.128 g/g material at optimal conditions, in which gamma-sitosterol, unsaturated fatty acids and gamma-tocopherol had higher relative concentrations as determined by GC–MS. The broken and intact cell (BIC) model, with reduced adjustable parameters, was utilized to simulate the SFE process. The values of average absolute relative deviation (AARD) were in the range 2.34–10.9%, indicating that the improved method had a similar effect to the BIC model when three parameters were adjusted. The parameters obtained during the modeling had clear physical meanings and were used to gain an in-depth understanding of the SFE process theoretically.     

Water and ethanol as co-solvent in supercritical fluid extraction of proanthocyanidins from grape marc: A comparison and a proposal

Supercritical carbon dioxide (SC-CO₂) extraction of grape marc was studied using water (W) and ethanol (EtOH) as co-solvent at 15% (w/w), 100 and 200 MPa, and 313.15, 323.15 and 333.15 K to analyze their influence upon total phenols of the extracts. The overall extraction curves were determined and suggested 10 MPa and 313.15 K as the best operating conditions for SC-CO₂ + 15%W extraction, and 10 MPa and 333.15 K for SC-CO₂ + 15% EtOH. The phenolic yields obtained were 63.4 g/kg of extract for SC-CO₂ + 15% W and 38.8 g/kg of extract for SC-CO₂ + 15% EtOH. An alternative method combining Sc-CO₂ + 15% W extraction, followed by SC-CO₂ + 15% EtOH was tested. This procedure provided the best results allowing to obtain the highest phenolic yield (68.0 g/kg of extract), phenol content (733.6 mg GAE/100 g DM), proanthocyanidins concentration (572.8 mg catechin/100 g DM) and antioxidant activity (2649.6 mg α-tocopherol/100 g DM). SC-CO₂ methods were compared with methanol extraction.     

Extraction of phenolic compounds from pitanga (Eugenia uniflora L.) leaves by sequential extraction in fixed bed extractor using supercritical CO2, ethanol and water as solvents

With the goal of maximizing the extraction yield of phenolic compounds from pitanga leaves (Eugenia uniflora L.), a sequential extraction in fixed bed was carried out in three steps at 60 °C and 400 bar, using supercritical CO₂ (non-polar) as solvent in a first step, followed by ethanol (polarity: 5.2) and water (polarity: 9.0) in a second and third steps, respectively. All extracts were evaluated for global extraction yield, concentration and yield of both polyphenols and total flavonoids and antioxidant activity by DPPH method (in terms of EC₅₀). The nature of the solvent significantly influenced the process, since the extraction yield increased with solvent polarity. The aqueous extracts presented higher global extraction yield (22%), followed by ethanolic (16%) and supercritical extracts (5%). The study pointed out that the sequential extraction process is the most effective in terms of global extraction yield and yield of polyphenols and total flavonoids, because it produced the more concentrated extracts on phenolic compounds, since the supercritical ethanolic extract presented the highest phenolics content (240.5 mg GAE/g extract) and antioxidant capacity (EC₅₀ = 9.15 μg/mL). The most volatile fraction from the supercritical extract, which is similar to the essential oils obtained by steam distillation or hydrodistillation, presented as major compounds the germacrenos D and B + bicyclogermacrene (40.75%), selina-1,3,7(11)-trien-8-one + selina-1,3,7(11)-trien-8-one epoxide (27.7%) and trans-caryophyllene (14.18%).     

Mathematical modeling and mass transfer considerations in supercritical fluid extraction of Posidonia oceanica residues

Posidonia oceanica residues were extracted with supercritical CO₂ in order to isolate phenolic compounds. The process was optimized by developing a mathematical model based on mass transfer mechanism consisting of adsorption of supercritical fluid on the solid particles, desorption of solute and convective transfer of solute phase along the column. Henry relation between solute concentrations on the surface of the solid (Cs) and in the solid (q) was approximated in order to describe the adsorption/desorption equilibrium. The model parameters such as solid-liquid film mass transfer coefficient (kf), molecular diffusivity coefficient (D_AB) and axial dispersion (D_ax) were estimated using empirical methods. The linear driving force model was applied to improve the yield of total phenolic acid recovery. The optimum parameters were elicited as 25 MPa, 323.15 K and a co-solvent mass ratio of 20% yielding 34.97 μg per gram of dry feed and the model satisfactorily described the extraction yield which can be used for scale-up purposes.     

Argon as a potential processing media for natural and synthetic substances

Phase equilibrium data of caffeine, vanillin, o-ethyl vanillin and a natural rosemary extract (containing 73.9% carnosic acid and 14.7% carnosol) in argon have been determined in present work.Solubility data were determined at temperatures of 313.15 K, 333.15 K and 363.15 K and in the pressure range from 0.82 MPa up to 50.27 MPa using a static–analytic method and were compared to solubility data of the same substances in CO₂.Maximal solubility of vanillin in argon was obtained at a temperature of 313.15 K and a pressure of 43.8 MPa, approx. 0.015 g/g. Comparing the solubility data of pure vanillin in argon and in CO₂ higher solubility in argon is observed at lower temperatures and pressures. For o-ethyl vanillin the solubility in argon is higher in comparison to solubility in CO₂ in the entire range of pressure, especially at higher temperatures_.Maximal solubility of caffeine in argon was observed at a temperature of 363.15 K 0.001361 g caffeine/g argon at 38.9 MPa. With increasing pressure solubility increases, while temperature does not have a noticeable impact in the temperature range from 313.15 K to 333.15 K; the solubility increased with increasing temperature to 363.15 K. Similarly, solubility of carnosic acid extract increases with increasing pressure, from about 0.0097 × 10⁻² g substance/g gas at 2.08 MPa and at 313.15 K to 0.0338 × 10⁻² g substance/g gas at 50.27 MPa and at 363.15 K.Solubility of the investigated compounds in argon is a function of both, pressure and temperature. Generally, pressure significantly impacts solubility particularly up to a pressure of 20.0 MPa in case of vanillin and up to 30 MPa in case of o-ethyl vanillin and carnosic acid extract. An additional increase of pressure has only a slight impact on solubility. In the case of caffeine, the impact of pressure on the solubility becomes more evident at pressures higher than 20 MPa.     

Integrated supercritical fluid extraction and subcritical water hydrolysis for the recovery of bioactive compounds from pressed palm fiber

Pressed palm fiber (PPF), a residue obtained from palm oil industry, is a source of bioactive compounds, such as carotenoids, which are used as food additives. It also has cellulose and hemicellulose that can be used to yield fermentable sugars for the production of second generation ethanol. Supercritical fluid extraction (SFE) of pressed palm fiber provides an oil rich in carotenoids while subcritical water hydrolysis (SubWH) produces hydrolysates with high amounts of fermentable sugars. In this work, the effects of pressure (15–30 MPa) and temperature (318 and 328 K) on SFE of carotenoids were investigated. The SFE extract with highest carotenoid content was obtained at 318 K and 15 MPa (2.3% d.b., 0.81 mg β-carotene/g extract). After the extraction, the influence of process temperature (423–633 K), pressure (15 and 25 MPa), solvent:feed ratio (120 and 240), and residence time (1.25–5 min) on SubWH of the extraction residue was studied. At the temperature of 523 K, the highest total reducing sugar yield (11–23 g glucose/100 g carbohydrate) and the highest biomass conversion (40–97%) were obtained for any pressure and solvent:feed ratio. The highest selectivity for saccharide formation was found at 423 K (20–59 mol glucose/mol furfural equivalent). Optimal conditions for high saccharide formation and low sugar degradation product in subcritical hydrolysis were obtained at 523 K, 15 MPa, solvent:feed ratio of 120, residence time of 2.5 min with a total reducing sugar yield of 22.9 g glucose/100 g carbohydrate and a conversion of 84.9%.     

Extraction of phenolic compounds and anthocyanins from blueberry (Vaccinium myrtillus L.) residues using supercritical CO2 and pressurized liquids

This work explored the potential of subcritical liquids and supercritical carbon dioxide (CO₂) in the recovery of extracts containing phenolic compounds, antioxidants and anthocyanins from residues of blueberry (Vaccinium myrtillus L.) processing. Supercritical CO₂ and pressurized liquids are alternatives to the use of toxic organic solvents or extraction methods that apply high temperatures. Blueberry is the fruit with the highest antioxidant and polyphenol content, which is present in both peel and pulp. In the extraction with pressurized liquids (PLE), water, ethanol and acetone were used at different proportions, with temperature, pressure and solvent flow rate kept constant at 40 °C, 20 MPa and 10 ml/min, respectively. The extracts were analyzed and the highest antioxidant activities and phenolic contents were found in the extracts obtained with pure ethanol and ethanol + water. The highest concentrations of anthocyanins were recovered with acidified water as solvent. In supercritical fluid extraction (SFE) with CO₂, water, acidified water, and ethanol were used as modifiers, and the best condition for all functional components evaluated was SFE with 90% CO₂, 5% water, and 5% ethanol. Sixteen anthocyanins were identified and quantified by ultra performance liquid chromatography (UPLC).     

Extraction of bioactive compounds from peach palm pulp (Bactris gasipaes) using supercritical CO2

Natural compounds with biological activity have recently attracted special interest in the agro-industry as sources of additives in nutraceutical food production and pharmaceutical industries. Herein, we evaluated extracts obtained from peach palm fruit (Bactris gasipaes) using supercritical carbon dioxide, in terms of yield, total phenolic content, total flavonoids, total carotenoids, and antioxidant activity by β-carotene bleaching method. Extractions were performed at 40, 50, and 60 °C and 100, 200, and 300 bar; additionally, Soxhlet (with petroleum ether) and methanol extraction were conducted. The results showed that supercritical CO₂ allows obtaining extracts rich in carotenoids and, although it presents lower yield than conventional extraction (SOX), supercritical CO₂ represents a technique with greater advantages. The best operation condition for supercritical extraction was 300 bar–40 °C, given that the highest concentration of carotenoids was obtained, without the yield being significantly different from that obtained with 300 bar–60 °C, this extract had antioxidant activity comparable to that of commercial caffeic acid.     

Supercritical fluid extraction from Syzygium aromaticum buds: Phase equilibrium,mathematical modeling and antimicrobial activity

Clove essential oil is an important product to food industry because it presents a powerful antioxidant and antimicrobial potential enabling its use for the substitution of synthetic commercial products for food preservation. The objective of this paper is to study the extraction kinetics for predicting operational condition to obtain Syzygium aromaticum essential oil using CO₂ as solvent by means of the introduction of thermodynamic approach into the mathematical modeling of the process. Extractions were performed at 9000 kPa/313.15 K, 10,000 kPa/313.15 K, 9000 kPa/323.15 K, and 10,000 kPa/323.15 K and the essential oil yields obtained were 14.17%, 12.32%, 13.11%, and 14.02%, respectively. To calculate the extract solubility in CO₂ supercritical, the Peng–Robinson EoS coupled with three mixing rules (van der Waals 1, van der Waals 2 and Mathias–Klotz–Prausnitz) was used and a mass transfer model was employed to represent the relationship yield versus extraction time. The mathematical modeling of the process using the calculated solubility presented high concordance with experimental data. The volatile extracts were analyzed by GC/MS and the major compounds were eugenol and β-caryophyllene. Also, minimum inhibitory concentration (MIC) of supercritical extracts was determined with respect to Escherichia coli, Staphylococcus aureus and Enterococcus faecalis by microdilution method. All samples inhibited the bacterial growth, being the extract obtained at 313.15 K/9000 kPa the most effective.     

Extraction of protocatechuic acid from Scutellaria barbata D. Don using supercritical carbon dioxide

The use of supercritical carbon dioxide (SC⿿CO₂), with water as a modifier, was evaluated in this study as a method to extract protocatechuic acid (PA) from Scutellaria barbata D. Don. The highest extraction yield of PA, 64.094 ± 2.756 μg/g of dry plant, was achieved at 75 °C and 27.5 MPa, with the addition of 15.6% (v/v) water as a modifier. The mean particle size was 0.355 mm, the CO₂ flow rate was 2.2 mL/min (STP) and the dynamic extraction time was 100 min. At pressures of 16.2⿿30.0 MPa and temperatures of 45⿿75 °C, the mole fraction solubilities of PA in SC⿿CO₂ ranged from 2.829 ÿ 10^⿿7 to 9.631 ÿ 10^⿿7. The solubility data for PA fit well in the Chrastil model. It is evident that the SC⿿CO₂ extraction uses less solvent, saves both energy and time and is an environmentally friendly extract technology that can be used in the food, cosmetic and pharmaceutical industries.     

Extraction of bioactive enriched fractions from Eruca sativa leaves by supercritical CO2 technology using different co-solvents

Supercritical fluid extraction from freeze-dried Eruca sativa leaves is assessed with the aim of studying the feasibility to obtain bioactive enriched fractions containing different classes of valuable compounds. Total extraction yields and compositions using pure CO₂ and CO₂ + selected co-solvents are compared. Overall extraction curves, fitted by the model of broken and intact cells developed by Sovová, are reported and the influence of the main parameters that affect the extraction process is analysed. The extract with the highest content in glucosinolates and phenols was collected at 30 MPa and 75 °C using 8% (w/w) of water with respect to the CO₂ flow rate, whereas the fraction richest in lipids was obtained using 8% (w/w) of ethanol as co-solvent at 45 °C and 30 MPa. A process including a first step with supercritical CO₂ extraction using water as co-solvent followed by a second step, where a fraction rich in lipids is extracted using ethanol as co-solvent, is proposed. SCCO₂ results are compared with Soxhlet and other methods that combine organic solvents with ultrasounds.     

Supercritical CO2 extraction of bioactive Tyrian purple precursors from the hypobranchial gland of a marine gastropod

Supercritical CO₂ provides considerable advantages over traditional solvents for the extraction of bioactive compounds from organic matter. Here we demonstrate the use of supercritical CO₂ as an efficient and safe alternative to traditional solvent extraction for the recovery of bioactive Tyrian purple precursors tyrindoleninone, 6-bromoisatin and tyriverdin from the marine mollusc Dicathais orbita. The effect of pressure on the selective extraction of brominated indoles was tested at 15, 30 and 50 MPa CO₂, and was compared to traditional chloroform extract composition and yields. Extracts obtained from 15 MPa selectively concentrated 6-bromoisatin, at 78% of the extract composition, whereas increased pressures of 30 and 50 MPa increased the solvating power of supercritical CO₂ to include the more lipophilic tyrindoleninone at 35 and 29% respectively, and tyriverdin at 23 and 40% respectively. This extraction method was also effective in separating the brominated indoles from toxic choline esters in the mollusc extracts. Extract yields from supercritical CO₂ were comparable to solvent extraction relative to whole whelk weight. This provides a viable alternative for nutraceutical development that does not rely on the use of toxic solvents.     

Density and viscosity of the binary polyethylene glycol/CO2 systems

Density of CO₂ saturated solutions of polyethylene glycols (PEGs) of different molecular weight was measured in pressure range from 8.0 MPa up to 47.7 MPa at a temperature of 343 K by a volumetric method. To validate the method density of pure CO₂ was measured at different pressures and a temperature of 293 K. The results were compared to the literature data and the accuracy was better than 2%. The density was between 1.17 g/mL for PEG 1000/CO₂ at 14.5 MPa and 1.78 g/mL for the system PEG 4000/CO₂ at 35 MPa. Further, the data were compared to results, obtained by a gravimetric method using magnetic suspension balance (MSB).Viscosity of CO₂ saturated solutions of polyethylene glycols (PEGs) of different molecular weight at different pressures and at a temperature of 343 K was measured using a high pressure view cell. Also a temperature impact on the viscosity of pure PEGs was observed at ambient pressure. After saturating PEG 1500 with 10 MPa of CO₂ pressure its viscosity decreases from 76.6 mPa s to 2.24 mPa s at 333 K. Further addition of CO₂ and increasing the pressure results in even lower viscosity and the highest viscosity reduction was reached at the highest pressure; at 35 MPa viscosity of the system PEG 1500/CO₂ is only 0.665 mPa s.