A green separation process for recovery of healthy oil from pumpkin seed

In this study, pumpkin seeds, called as “Ürgüp Sivrisi” and grown in Cappadocia region, were used as plant materials because of high aroma contents. In the supercritical fluid extraction of pumpkin seed oil, the effect of main process parameters as the particle size (250-2360 μm), the volumetric flow rate of supercritical solvent (0.06-0.30 L/h), the operating pressure (20-50 MPa), the operating temperature (40-70 °C), the type of entrainer (ethanol and n-hexane) and those concentrations (0-10 vol.%) on the extraction yield, the oil solubility and the initial extraction rate were investigated. A cross-over effect for the extraction of pumpkin seed oil using supercritical CO₂ was determined at the operating pressure of 20-30 MPa. The maximum extraction yield obtained with entrainer free was reached 0.50 g oil/g dry seed at 600-1180 μm, 0.12 L/h, 50 MPa and 70 °C for the operation time of 5 h. The maximum extraction yield obtained with ethanol as an entrainer in the experiments was reached 0.54 g oil/g dry seed at the conditions of 600-1180 μm, 0.12 L/h, 30 MPa, 40 °C and 8 vol.% for the operating time of 2 h. The oil compositions were determined by gas chromatography analysis and the results showed that the compositions of pumpkin seed oil which were obtained by means of organic solvent extraction and supercritical fluid extraction were similar. The average oil compositions determined as 9.3 (±0.43)% palmitic acid, 7.5 (±0.6)% stearic acid, 32.3 (±0.6)% oleic acid, 48.1 (±0.6)% linoleic acid and 0.7 (±0.3)% linolenic acid. The morphological changes in the seeds were determined by the scanning electron microscopy analysis.     

Optimization of process variables for essential oil components from Satureja hortensis by supercritical fluid extraction using Box-Behnken experimental design

The oil and extracts of Satureja hortensis cultivated in Iran were extracted using supercritical carbon dioxide and hydrodistillation method. The oil and extracts were analyzed by GC-FID and GC/MS. The compounds were identified according to their retention indices and mass spectra (EI, 70 eV). The effects of various parameters such as pressure, temperature, percent of modifier (methanol) and extraction time, were investigated by a fractional factorial design (2^4-1) to determine the significant parameters and their interactions. The results showed that the pressure, temperature and percent of modifier are significant (p < 0.05), but the extraction time was found to be insignificant. The response surface methodology (RSM), based on Box-Behnken design was employed to obtain the optimum conditions of the significant parameters (pressure, temperature and percent of modifier). The optimal conditions could be obtained at a pressure of 35.0 MPa, temperature of 72.6 °C, and 8.6% (v/v) for methanol. The main extracted components using SFE were γ-Terpinene (35.5%), Thymol (18.2%) and Carvacrol (29.7%).     

Production of biodiesel by ultrasound assisted esterification of Oreochromis niloticus oil

This paper evaluates the production of methyl esters from Oreochromis niloticus (Nile tilapia) oil and methanol. The reaction was carried out applying low-frequency high-intensity ultrasound (40 kHz) under atmospheric pressure and ambient temperature. Response surface methodology (RSM) was used to evaluate the influence of alcohol to oil molar ratio, catalyst concentration (sulfuric acid) and temperature on the yield of O. niloticus oil into methyl esters. Analysis of the operating conditions by RSM showed that the most important operating condition affecting the reaction was the alcohol to FFA molar ratio. The highest yield observed was of 98.2% after 90 min of reaction. The optimal operating condition was obtained applying an alcohol to oil molar ratio of 9.0 and a catalyst concentration of 2.0% w/w and temperature of 30 °C.     

Supercritical fluid extraction of flavonoids from Maydis stigma and its nitrite-scavenging ability

Supercritical fluid carbon dioxide (SF-CO₂) extraction (SFE) of flavonoids from Maydis stigma and its nitrite-scavenging ability were investigated. The effects of extraction time, particle size and co-solvent composition in terms of water content in ethanol were first optimized. Then, a Box-Behnken design combined with response surface methodology (RSM) was employed to study the effects of three independent variables (temperature, pressure and co-solvent amount) on the extraction yield of flavonoids. A maximal extraction yield of flavonoids of approximately 4.24 mg/g of M. stigma by SFE was obtained under optimal conditions (a temperature of 50.88 °C, a pressure of 41.80 MPa, a co-solvent amount of 2.488 mL/g and an extraction time of 120 min with 0.4-mm particle sizes and 20% aqueous ethanol as the co-solvent). Furthermore, the nitrite-scavenging ability of the flavonoid-enriched SFE extracts was assessed using the Griess reagent. The flavonoid-enriched SFE extracts exhibited the highest scavenging ability on nitrite (88.1 ± 3.04%) at the concentration of 500 μg/mL and at pH 3.0. The nitrite-scavenging ability of the extracts appeared to be concentration dependent but negatively correlated with the pH.     

Thermal stability of biodiesel in supercritical methanol

Non-catalytic biodiesel production technologies from oils/fats in plants and animals have been developed in our laboratory employing supercritical methanol. Due to conditions in high temperature and high pressure of the supercritical fluid, thermal stability of fatty acid methyl esters and actual biodiesel prepared from various plant oils was studied in supercritical methanol over a range of its condition between 270 °C/17 MPa and 380 °C/56 MPa. In addition, the effect of thermal degradation on cold flow properties was studied. As a result, it was found that all fatty acid methyl esters including poly-unsaturated ones were stable at 270 °C/17 MPa, but at 350 °C/43 MPa, they were partly decomposed to reduce the yield with isomerization from cis-type to trans-type. These behaviors were also observed for actual biodiesel prepared from linseed oil, safflower oil, which are high in poly-unsaturated fatty acids. Cold flow properties of actual biodiesel, however, remained almost unchanged after supercritical methanol exposure at 270 °C/17 MPa and 350 °C/43 MPa. For the latter condition, however, poly-unsaturated fatty acids were sacrificed to be decomposed and reduced in yield. From these results, it was clarified that reaction temperature in supercritical methanol process should be lower than 300 °C, preferably 270 °C with a supercritical pressure higher than 8.09 MPa, in terms of thermal stabilization for high-quality biodiesel production.     

Supercritical CO2 extraction of Helichrysum italicum: Influence of CO2 density and moisture content of plant material

Kinetics and selectivity of supercritical carbon dioxide (SC CO₂) extraction of Helichrysum italicum flowers were analyzed at pressures in the range of 10-20 MPa and temperatures of 40 °C and 60 °C (density of SC CO₂ from 290 to 841 kg/m³) and also at 10 MPa and 40 °C using flowers with different moisture contents (10.5% and 28.4%). Increased moisture content of H. italicum flowers resulted in enchased solubility of solute enabling decrease of SC CO₂ consumption necessary for achieving desired extraction yield. The most abundant compounds in the supercritical extracts are sesquiterpenes and waxes while monoterpenes and sesquiterpenes are the main constituents of essential oil obtained by hydrodistillation. The optimal set of working parameters with respect to extraction yield, SC CO₂ consumption and chemical composition of extract were defined related to moisture content of raw material and SC CO₂ density.     

Reactive extraction and in situ esterification of Jatropha curcas L. seeds for the production of biodiesel

Jatropha curcas L. has recently been hailed as the promising feedstock for biodiesel production as it does not compete with food sources. Conventional production of biodiesel from J. curcas L. seeds involve two main processing steps; extraction of oil and subsequent esterification/transesterification to fatty acid methyl esters (FAME). In this study, the feasibility of in situ extraction, esterification and transesterification of J. curcas L. seeds to biodiesel was investigated. It was found that the size of the seed and reaction period effect the yield of FAME and amount of oil extracted significantly. Using seed with size less than 0.355 mm and n-hexane as co-solvent with the following reaction conditions; reaction temperature of 60 °C, reaction period of 24 h, methanol to seed ratio of 7.5 ml/g and 15 wt% of H₂SO₄, the oil extraction efficiency and FAME yield can reached 91.2% and 99.8%, respectively. This single step of reactive extraction process therefore can be a potential route for biodiesel production that reduces processing steps and cost.     

Guava (Psidium guajava L.) seed oil obtained with a homemade supercritical fluid extraction system using supercritical CO2 and co-solvent

In this work we designed and built a homemade supercritical fluid extraction (HM-SFE) system, in which pure CO₂ and CO₂ with co-solvents were used. The HM-SFE was made by means of thermal dilatation-contraction (TDC). This HM-SFE system was used for obtaining guava (Psidium guajava L.) seed oil, using supercritical CO₂ adding ethanol as co-solvent (CO₂ SC/EtOH), extractions were performed at 313 K and different pressures (10, 20 and 30 MPa), each one in four stages of 30 min, the extract with higher yield was subjected to transesterification and high-resolution gas chromatography (HRGC) analysis. The highest extraction yield was obtained at 30 MPa (17.30% w/w), this yield was higher than one observed in a previous work using SC-CO₂, and near to the one obtained by Soxhlet extraction (20.2% w/w). HRGC enabled the identification of components of the derivatized extract as methyl esters of palmitic, oleic, linoleic, and stearic fatty acids. The results obtained with HM-SFE system was compared with a commercial SFE system, obtained very similar results. In this work was possible to construct a low cost and simple manner HM-SFE system which was employed for obtaining guava seed oil, using CO₂ SC/EtOH.     

Supercritical carbon dioxide extraction of oil from Mexican chia seed (Salvia hispanica L.): Characterization and process optimization

Supercritical carbon dioxide (SC-CO₂) was employed to extract oil rich in omega-3 fatty acids (FAs) from chia seeds, and the physicochemical properties of the oil were determined. A central composite rotatable design was used to analyze the impact of temperature (40 °C, 60 °C and 80 °C), pressure (250 bar, 350 bar and 450 bar) and time (60 min, 150 min and 240 min) on oil extraction yield, and a response surface methodology (RSM) was applied. The extraction time and pressure had the greatest effects on oil. The highest oil yield was 92.8% after 300 min of extraction time at 450 bar. The FA composition varied depending on operating conditions but had a high content of α-linolenic acid (44.4-63.4%) and linoleic acid (19.6-35.0%). The rheological evaluation of the oils indicated a Newtonian behavior. The viscosity of the oil decreased with the increase in temperature following an Arrhenius-type relationship.     

Extraction of sesame seed (Sesamun indicum L.) oil using compressed propane and supercritical carbon dioxide

This work is aimed to investigate the extraction of sesame seed (Sesamun indicum L.) oil using supercritical carbon dioxide and compressed propane as solvents. The extractions were performed in a laboratory scale unit in a temperature and pressure range of 313-333 K and 19-25 MPa for carbon dioxide and 303-333 K and 8-12 MPa for propane extractions, respectively. A 2² factorial experimental design with three replicates of the central point was adopted to organize the data collection for both solvents. The results indicated that solvent and density were important variables for the CO₂ extraction, while temperature is the most important variable for the extraction yield with propane. The extraction with propane was much faster than that with carbon dioxide due to the fact that propane is a better solvent for vegetable oils compared to carbon dioxide. On the other hand, characteristics of extracted oil, its oxidative stability determined by DSC and chemical profile of constituent fatty acids determined by gas chromatography, were similar to both solvents. The mathematical modeling of the extraction kinetics using a second order kinetic presented good results for the extraction with both solvents.     

Supercritical CO2 extraction of oil, carotenoids, squalene and sterols from lotus (Nelumbo nucifera Gaertn) bee pollen

The high-quality oil, abundant in carotenoids, squalene and sterols (mainly consisting of campesterol, stigmasterol, β-sitosterol and β-amyrin), was extracted by supercritical CO₂ from lotus bee pollen for its potential nutraceutical use. The effects of extraction pressure and temperature on the yields and the compositions of the extracts were investigated by using a two-factor central composite rotatable design experiment. ANOVA for response surface model demonstrated that the data were adequately fitted into four polynomial models. The yields of the oil, carotenoids, squalene and sterols were significantly influenced by the experimental variables. It was predicted that maximum oil yield obtained at the extraction pressure of 38.2 MPa and temperature of 49.7 °C contained the maximum amount of carotenoids, squalene and sterols. GC-FID analysis of the fatty acid composition of lotus bee pollen oil showed that polyunsaturated fatty acids accounted for approximately 22% of the total fatty acids.     

Extraction of sage (Salvia officinalis L.) by supercritical CO2: Kinetic data, chemical composition and selectivity of diterpenes

The supercritical carbon dioxide (SFE) extraction of Dalmatian sage (Salvia officinalis L.) was investigated and compared to extraction performed by Soxhlet ethanol-water (70:30) mixture extraction (SE) and hydrodistillation (HD). The supercritical extraction allowed isolation of wide spectrum of phytochemicals, while other applied methods were limited to either volatiles (HD) or high molecular compounds isolation (SE). The kinetics of the supercritical extraction and fractionation within the pressure range of 10-30 MPa at 50 °C were also analyzed as well as the chemical compositions of total extract and partial or differential fractions isolated at different CO₂ consumption. Volatile fraction could be isolated at low pressure and low CO₂ consumption, whereby the pressures between 10 and 15 MPa followed by increased CO₂ consumption were favourable for obtaining desired selectivity of diterpenes which contain compounds with expressed antioxidative characteristics.     

Continuous production of fatty acid methyl esters from corn oil in a supercritical carbon dioxide bioreactor

Continuous production of fatty acid methyl esters (FAMEs) from corn oil was studied in a supercritical carbon dioxide (SC-CO₂) bioreactor using immobilized lipase (Novozym 435) as catalyst. Response surface methodology (RSM) based on central composite rotatable design (CCRD) was employed to investigate and optimize the reaction conditions: pressure (11-35 MPa), temperature (35-63 °C), substrate mole ratio (methanol:corn oil 1-9) and CO₂ flow rate (0.4-3.6 L/min, measured at ambient conditions). Increasing the substrate mole ratio increased the FAME content, whereas increasing pressure decreased the FAME content. Higher conversions were obtained at higher and lower temperatures and CO₂ flow rates compared to moderate temperatures and CO₂ flow rates. The optimal reaction conditions generated from the predictive model for the maximum FAME content were 19.4 MPa, 62.9 °C, 7.03 substrate mole ratio and 0.72 L/min CO₂ flow rate. The optimum predicted FAME content was 98.9% compared to an actual value of 93.3 ± 1.1% (w/w). The SC-CO₂ bioreactor packed with immobilized lipase shows great potential for biodiesel production.     

Extraction of phenolic fraction from guava seeds (Psidium guajava L.) using supercritical carbon dioxide and co-solvents

In this work the supercritical fluid extraction (SFE) with carbon dioxide (CO₂) and with ethyl acetate (EtAc) and ethanol (EtOH) as co-solvents was applied to obtain the phenolic fraction from guava seeds (Psidium guajava L.). The extraction was explored at various operating conditions, using 10, 20 and 30 MPa and 40, 50 and 60 °C. The use of EtAc and EtOH as co-solvents in SFE was also studied. The supercritical process was compared with traditional techniques such as Soxhlet extraction using EtAc and EtOH as solvents. The quality of the different extracts, obtained using SFE and Soxhlet methods and different solvents, was evaluated through the antioxidant activity, obtained by the collection methods of scavenging DPPH and bleaching of β-carotene, and also through the total phenolic content (TPC) of the samples, by the Folin-Ciocalteu method. The antioxidant potential indicates the use of ethanol as co-solvent as the best modifier in SFE, used in concentration of 10% (w/w) at 50 °C and 30 MPa. The quality of the extracts obtained by SFE with EtOH varied with the operating conditions of temperature and pressure, with higher values obtained at 10 and 20 MPa for TPC results and also antioxidant methods. The process yield of the phenolic fraction was also evaluated for all the extraction procedures studied (SFE and Soxhlet), with results varying from 0.380 to 1.738% (w/w).     

Supercritical CO2 extraction of lipids and astaxanthin from Brazilian redspotted shrimp waste (Farfantepenaeus paulensis)

Brazilian redspotted shrimp (Farfantepenaeus paulensis) waste is an important source of carotenoids such as astaxanthin and lipids with a high ω−3 fatty acids content, mainly docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). In order to establish an efficient and environmental friendly recovery process, the lipids and astaxanthin were extracted from the freeze-dried redspotted shrimp waste (including head, tail and shell) using supercritical carbon dioxide. The effects of the extraction conditions of pressure (200-400 bar) and temperature (40-60 °C) on the global yield (X₀), astaxanthin extraction yield and astaxanthin concentration in the extract were evaluated. It was found that the pressure and temperature showed a very low significant effect on the lipid extraction yield using supercritical CO₂. In comparison with lipid extraction by solvents, maximum efficiency of supercritical fluid extraction achieved 64% of hexane extraction yield. On the other hand, temperature and pressure had significant effects on astaxanthin extraction yield. Thegreatest amount of extract was obtained at 43 °C and 370 bar, with 39% of recovery.     

Supercritical CO2 extraction of dittany oil: Experiments and modelling

The extraction of oil from dittany (Origanum dictamnus) using supercritical carbon dioxide was investigated. The experiments were performed in a bench scale apparatus at the pressures of 100 and 150 bar and at the temperatures of 40 and 60 °C. The effect of the solvent flow rate and the mean particle diameter of dittany on the extraction yield was also investigated at 100 bar and 40 °C. It is shown that the extraction yield increases with pressure, while the increase of temperature and mean particle diameter leads to the opposite effect. Different flow rates of SCCO₂ lead to similar extraction yields. Finally, the overall extraction curves are well correlated by a mass balance model of plug flow, in which the intraparticle diffusion resistance has the controlling role.     

Cleaner production of ephedrine from Ephedra sinica Stapf by membrane separation technology

A promising cleaner approach, including chemical extraction, separation and purification by membranes separation technology, for producing ephedrine from Ephedra sinica Stapf was introduced. The extraction yield of ephedrine reached 92.45 ± 0.46%, increased by 28.25 ± 0.13% than that of the traditional process, at solid-to-liquid ratio of 1/10, extraction temperature of 80 °C, total extraction time of 20 h and reextraction for 3 times. In microfiltration, the transmissivity for ephedrine was up to 97.88 ± 1.06% and the retention rate of impurities reached 78.56 ± 0.96% when the membranes with pore size of 0.45 μm were employed at inlet and outlet operating pressure of 0.26 MPa and 0.14 MPa, respectively. The surface velocity of membrane channel was 3.5 m s⁻¹ and membrane flux was 207 ± 3.71 l m⁻² h⁻¹. Nanofiltration membranes with 160 Da molecular weight cut-off (MWCO) were adopted to separate the ephedrine from microfiltration permeate at a transmembrane pressure of 0.6 MPa wherein the retention rate of ephedrine reached 99.88 ± 0.23% and the membrane flux was 19.88 ± 1.12 l m⁻² h⁻¹. For this improved approach, the COD of nanofiltration permeate was only 110 ± 12.56 mg l⁻¹ which could be recycled to the extraction process, causing a decrease by 59.38 ± 1.67% of water consumption and 75.76 ± 1.89% of wastewater generation in comparison with those of the traditional process.     

Solubility of Jatropha and Aquilaria oils in supercritical carbon dioxide at elevated pressures

This study investigated experimental equilibrium solubilities of Jatropha curcas and Aquiliaria crassna oils dissolved in supercritical carbon dioxide at temperatures of 318-338 K and pressures of 20, 25, 30, 35 MPa. The highest solubility of J. curcas and A. crassna oil were 29.8 and 28.4 mg L⁻¹, respectively, at 338 K and 35 MPa. The oil solubilities and the concentration of triglycerides both increased with increasing temperature and pressure. Triglyceride molecules surrounded by carbon dioxide molecules may be proposed since solubilities increased with the flux of supercritical carbon dioxide. The solubility of these two oils linearly increased with the density of supercritical carbon dioxide. Experimental data of the oil solubility were successfully correlated by the Chrastil equation.     

Antioxidant Activity and Total Polyphenols Content of Camellia Oil Extracted by Optimized Supercritical Carbon Dioxide

In this study, Camellia oil is co-extracted from Camellia oleifera seeds and green tea scraps by supercritical carbon dioxide (SC-CO₂), which is optimized on the extraction yield, ABTS-scavenging activity, and total polyphenols content (TPC) of oil by single-factor experiments combined with response surface methodology (RSM). The extraction temperature, pressure, dynamic time, carbon dioxide (CO₂) flow rate, and seed mass ratio were investigated with single-factor experiments. The results indicated the optimum CO₂ flow rate and dynamic extraction time were 15 L hour⁻¹ and 60 min (i.e., 2.382 kg CO₂/100 g sample). Furthermore, the complicated effects of extraction temperature (40–50 °C), pressure (20–30 MPa), and seed mass ratio (0.25–0.75) were optimized by RSM based on the Box–Behnken design (BBD). The models with high R-squared values were obtained and used to predict the optimum operating conditions of the process. Under the optimum operating conditions (i.e., temperature of 46 °C, pressure of 30 MPa, and seed mass ratio of 0.35), the extraction yield, ABTS-scavenging activity, and TPC of oil were 14.43 ± 0.17 g/100 g sample, 73.70 ± 0.34%, and 2.18 ± 0.05 mg GAE/g oil, which were in good agreement with the predicted values. In addition, the experiments indicated that the Camellia oil obtained was rich in polyphenols, resulting in better oxidation stability and antioxidant activity than the original oil.