Effects of supercritical carbon dioxide extraction parameters on virgin coconut oil yield and medium-chain triglyceride content

The extraction of coconut oil has been performed using supercritical carbon dioxide (SC-CO₂). The extractions were performed at pressure and temperature ranges of 20.7–34.5 MPa and 40–80 °C, respectively. It was observed that almost all (more than 99%) of the total oil could be extracted. Response surface methodology (RSM) was applied to evaluate the effects of the parameters (pressure, temperature and CO₂ consumption) on the extraction yield and medium-chain triglycerides (MCTs), in terms of the fatty acid content in the extracted oil. A correlation was established with p-values for both responses significant at the 95% confidence level.     

Application of response surface methodology to optimise supercritical carbon dioxide extraction of essential oil from Cyperus rotundus Linn.

Supercritical fluid extraction with carbon dioxide (SC-CO₂ extraction) was performed to isolate essential oils from the rhizomes of Cyperus rotundus Linn. Effects of temperature, pressure, extraction time, and CO₂ flow rate on the yield of essential oils were investigated by response surface methodology (RSM). The oil yield was represented by a second-order polynomial model using central composite rotatable design (CCRD). The oil yield increased significantly with pressure (p < 0.0001) and CO₂ flow rate (p < 0.01). The maximum oil yield from the response surface equation was predicted to be 1.82% using an extraction temperature of 37.6 °C, pressure of 294.4 bar, extraction time of 119.8 min, and CO₂ flow rate of 20.9 L/h.     

Extraction of α-tocopherol and γ-oryzanol from rice bran

The aim of this research was to study the effect of operating mode (continuous versus batch+continuous), temperature, pressure and solvent on α-tocopherol and γ-oryzanol extraction from rice bran (Oryza sativa Linn.) and compare the efficiency of three extraction methods: SC-CO₂ extraction, solvent extraction and soxhlet extraction. Three sets of experiments were performed. First, extraction using SC-CO₂ was performed over a range of temperatures and pressures (45-65 °C and at 38 and 48 MPa), and at a CO₂ flow rate of 0.45 mL/min. The results showed that the best conditions for α-tocopherol extraction were 55 °C, 48 MPa in the batch+continuous mode. For γ-oryzanol, the best conditions were 65 °C, 48 MPa and in the continuous mode. In the second set of experiments, solvent extraction using hexane and ethanol at 32 and 55-60 °C was studied. The results showed that none of the solvents could extract α-tocopherol; however, ethanol at 55-60 °C was suitable for γ-oryzanol extraction. Finally, soxhlet extraction experiments using hexane for α-tocopherol and ethanol for γ-oryzanol were also performed. In summary, SC-CO₂ was found to be the best solvent for extracting both α-tocopherol and γ-oryzanol from rice bran, because of its higher yields and extraction rate.     

Extraction of oil from tiger nut (Cyperus esculentus L.) with supercritical carbon dioxide (SC-CO2)

Supercritical carbon dioxide (SC-CO₂) was used to extract oil from tiger nuts and the physicochemical properties and the impact of extraction conditions [i.e., temperature (40 °C–80 °C), pressure (20–40 MPa) and time (60–360 min)] on the oil yield were studied. The response surface analysis results revealed that the oil yield was significantly (P < 0.05) influenced by the main effect of the extraction pressure, extraction time and their quadratic effects respectively. However, the interaction between the extraction temperature and time had no significant (P > 0.05) effect on the oil yield. The highest oil yield was 26.28 g/100 g sample after 210 min of extraction time at 30.25 MPa and 60 °C respectively. The fatty acid composition of oils obtained by SC-CO₂ and Soxhlet showed marked variation. Also, the fatty acid composition varied depending on the operating conditions. The viscosity of the oil decreased with the increase in temperature.     

Optimization of subcritical fluid extraction of seed oil from Nitraria tangutorum using response surface methodology

Subcritical fluid extraction (SFE) technology was used to extract oil from Nitraria tangutorum seed. The best possible combination of extraction parameters was found using response surface methodology (RSM) in a three-variable, three-level Box-Behnken experimental design (BBD). The optimum extraction parameters were an extraction time of 40 min, an extraction pressure of 0.60 MPa, an extraction temperature of 44 °C and a raw material particle size of 0.45 mm. Conventional solvent extraction and supercritical CO₂ fluid extraction were comparatively used. The yield of seed oil obtained using SFE was 12.92%, which was similar to or higher than the other methods. The chemical compositions of the seed oil, determined by GC–MS, indicate that its unsaturated fatty acids content was 97%. SFE proved to be an effective technique for extracting oil from N. tangutorum.     

Supercritical carbon dioxide extraction of seed oil from Opuntia dillenii Haw. and its antioxidant activity

Supercritical carbon dioxide extraction of seed oil from Opuntia dillenii Haw. and its antioxidant activity were investigated in this study. The effects of main operating parameters including extraction pressure, temperature, time and CO₂ flow rate on the extraction yield of seed oil were studied. The maximum extraction yield of 6.65% was achieved at a pressure of 46.96 MPa, a temperature of 46.51 °C, a time of 2.79 h and a CO₂ flow rate of 10 kg/h. The chemical composition of the seed oil was analysed by GC–MS. The main fatty acids were linolenic acid (66.56%), palmitic acid (19.78%), stearic acid (9.01%) and linoleic acid (2.65%). The antioxidant activity of seed oil was assessed by means of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging assay and β-carotene bleaching test. Both methods demonstrated notable antioxidant activity of seed oil, which is nearly comparable to the references ascorbic acid and butylated hydroxytoluene (BHT). The antioxidant activity of the seed oil was also found to be concentration-dependent.     

Extraction optimization of a hydrocolloid extract from cress seed (Lepidium sativum) using response surface methodology

Extraction conditions for maximum values of yield, viscosity and minimum protein content of hydrocolloid extract from Lepidium sativum seed were investigated using response surface methodology. A Central Composite Face Design (CCFD) with four independent variables: temperature (25–85 °C); pH (3–10); extraction time (10–25 min) and water to seed ratio (10:1–80:1) was used to study the response variables (yield, viscosity and protein content). Data analysis showed that all the variables significantly (p < 0.05) affected the extraction yield and viscosity, whereas the effect of water to seed ratio on protein content was not significant (p > 0.05). Applying a desirability function method the optimum parameters were: extraction temperature 35 °C, pH 10, water to seed ratio of 30:1 and an extraction time of 15 min. At this optimum point, apparent viscosity, yield and protein content were 0.2 Pa s, 6.46% and 0.57%, respectively. The experimental values were very close to the predicted values and were not statistically different (p > 0.05).     

Extraction of β-carotenes from palm oil mesocarp using sub-critical R134a

Sub-critical extraction of palm oil from palm mesocarp using R134a solvent was conducted via the dynamic mode to investigate the ability of R134a to extract β-carotene. The yield of palm oil and the solubility of β-carotene were investigated at 40, 60 and 80 °C and pressure range from 45–100 bar. The extracted oil was analysed for β-carotene content using UV–Vis spectrophotometry. The results showed that palm oil yield increased with pressure and temperature. The maximum solubility of β-carotene was obtained at 100 bar and 60 °C while the lowest solubility occurred at 80 bar and 40 °C. The higher concentration of extracted β-carotene ranging from 330–780 ppm as compared to that achieved through conventional palm oil processing indicates that extraction of β-carotene using R134a is viable.     

Effects of supercritical CO2 fluid parameters on chemical composition and yield of carotenoids extracted from pumpkin

Pumpkin is a traditional food that is grown extensively worldwide and is believed to be beneficial to human health due to its high contents of carotenoids. The carotenoids in pumpkin were extracted by organic solvents and by supercritical carbon dioxide (SC-CO₂), and then they were identified, quantified, and compared. β-carotene (31 to 40 g per 100 g of total carotenoids) was the predominate carotenoid in pumpkin. Lutein and lycopene contents were much higher in SC-CO₂ extracts than those in organic solvent extract. Cis-β-carotene increased by more than two times in the SC-CO₂ extracts, even at a relatively low temperature of 40 °C, over those in the solvent extracts, indicating both enhanced solubility and isomerization from trans- to cis-β-carotene. The influences of modifier (10 mL/100 mL), temperature (40-70 °C), and pressure (25-35 MPa) of SC-CO₂ extraction on the change of carotenoid yields were also investigated. The highest yield (109.6 μg/g) was obtained at 70 °C and 35 MPa, with a 73.7% recovery. Selective extraction could be achieved by adjusting the temperature and pressure. Higher proportions of all-trans-β-carotene extracts were achieved at 40 °C under both 25 MPa and 35 MPa conditions. In order to extract more cis-isomers, a higher temperature of 70 °C was preferred.     

Antifungal,antiaflatoxin and antioxidant potential of chemically characterized Boswellia carterii Birdw essential oil and its in vivo practical applicability in preservation of Piper nigrum L. fruits

The study explores the chemical profile, antimicrobial and antioxidant activity of Boswellia carterii essential oil (EO). The EO significantly inhibited growth and aflatoxin production by the food borne toxigenic strain of Aspergillus flavus at 1.75 μl/ml and 1.25 μl/ml respectively. It exhibited broad fungitoxic spectrum against 12 food borne moulds and also showed strong antioxidant activity, IC₅₀ value and % inhibition of linoleic acid peroxidation being 0.64 μl/ml and 51.68% respectively. The antifungal action of EO was observed in terms of reduction in ergosterol content of plasma membrane of A. flavus. As fumigant in food system in storage containers, the EO provided 65.38% protection against fungal deterioration of Piper nigrum. GC–MS results revealed 31 components of EO. The chemically characterized B. carterii EO may thus be recommended as plant based preservative in view of its antifungal, antiaflatoxigenic, antioxidant activity and efficacy in food system.     

Direct application of supercritical carbon dioxide for the reduction of Cronobacter spp. (Enterobacter sakazakii) in end products of dehydrated powdered infant formula

The objective of this study was to develop a viable new method for inactivation of Cronobacter spp. that could be applied directly to dehydrated powdered infant formula (PIF) using supercritical carbon dioxide (SC-CO₂). Samples inoculated with Cronobacter spp. were subjected to SC-CO₂ treatment under various conditions (temperature: 63, 68, and 73°C; pressure: 15, 20, and 25 MPa; time: 10, 20, and 30 min). The survival of Cronobacter spp. was assayed, as were any changes in the quality of the treated PIF. Inactivation of Cronobacter spp. by SC-CO₂ was enhanced as temperature and pressure conditions increased (>6.32 log₁₀ cfu/g). In a validation assay using low-level inoculation (3.21 log₁₀ cfu/g), treatment at 73°C and 15 MPa for 30 min, 20 MPa for 20 and 30 min, or 25 MPa for 20 and 30 min reduced Cronobacter spp. to undetectable levels, with no recovery of cell viability. There was no significant change in water activity, pH, and color of the treated PIF. Overall, the optimum conditions for elimination of Cronobacter spp. were determined to be 73°C and 20 MPa for 20 min. These parameters for effective SC-CO₂ treatment are feasibly applicable to end product of dehydrated PIF. The results of our study may contribute to the development of an efficient method for improving the microbiological safety of PIF.     

Characteristics of Prunus serotina seed oil

Oils from Prunus serotina raw and toasted seeds extracted with hexane and supercritical CO₂ were evaluated for their physicochemical characteristics. Supercritical CO₂ extracted the least oil (21.3%), with high absorbing carotenoid pigments. P. serotina oil had characteristically high refractive index and density with three typical absorbance peaks in the UVC (100–290 nm) range centred at 260, 270 and 280 nm. The oil was highly polyunsaturated and abundant in oleic (35%), α-elostearic (27%), linoleic (27%), palmitic (4%), stearic (4%) and β-elostearic (1%) acids. P. serotina seed oil exhibited at least three distinct thermal structural transitions between −35 and −13 °C with two reversing transitions between −19 and −12 °C. Thermal oxidation by differential scanning calorimetry (DSC) revealed a three step oxidation of P. serotina seed oil with the mean onset and oxidation temperatures at 121 and 130–273 °C, respectively, depending on processing. Supercritical CO₂ extraction and toasting significantly affected the thermal and oxidation characteristics, fluorescence, and fatty acids of oils.     

Effect of various salts and pH condition on rheological properties of Salvia macrosiphon hydrocolloid solutions

The extraction of Salvia macrosiphon seed hydrocolloid was performed successfully and the optimum hydration time and temperature were found to be 30 min and 25 °C for 12% extraction yield. The effect of solution pH (3–9) and addition of NaCl (0.5–3%), CaCl₂ (0.5–3%) and Na₂HPO₄ (0.2–0.6%) on rheological properties of the hydrocolloid solutions were investigated. Rheologcal data were fitted with the Power law model with regression coefficient of greater than 0.95. Strong shear thinning behavior with the n value of less than 0.53 was recorded. All variables had significant impacts on rheological parameters. The minimum and maximum consistencies were found at pH 3 and the 9, respectively. This was explained with the presence of carboxylic groups on the biopolymer backbone as indicated by FTIR. NaCl, CaCl₂ and Na₂HPO₄ had significant effects on rheological properties. Moreover, at similar salt concentration of 0.5%, Na₂HPO₄ had the greatest and NaCl had the lowest effect.     

Extraction of boldo (Peumus boldus M.) leaves with supercritical CO2 and hot pressurized water

High-activity fractions in boldo leaves were extracted with supercritical CO₂ (SC-CO₂) and hot pressurized water (HPW). Total yield after 3 h of extraction (0.6–3.5%) in low-pressure SC-CO₂ experiments increased with process pressure (60–150 bar) and decreased with temperature (30–60 °C), as expected. The extract obtained with SC-CO₂ at 50 °C and 90 bar contained approximately 50% of essential oil components. In higher pressure experiments with solvent mixtures, the yield increased with pressure (300–450 bar) and modifier concentration (2–10% ethanol), ranging 0.14–1.95 ppm for the alkaloid boldine and 1.8–4.8% for total solids following 1.5 h treatment at 50 °C. Boldine recovery was solubility-controlled, reaching 7.4 ppm after 7-h extraction at 450 bar and 50 °C using an ethanol–SC-CO₂ mixture (5% co-solvent). Boldine solubility and yield decreased when using pure CO₂ at higher pressure (600 bar, 50 °C). The extract yield after 3 h batch-wise HPW extraction increased from 36.9% at 100 °C to 53.2% at 125 °C, and then decreased as temperature was increased to 175 °C. Boldine yield decreased from 26.8 ppm at 100 °C to 0.7 ppm at 125 °C, and was negligible at ⩾150 °C. The essential oil yield increased to a maximum at 110 °C and was negligible at ⩾150 °C also. The ranking of antioxidant potency of various extracts was as follows: HPW at 110 °C > methanol (soxhlet extraction) ≫ high-pressure SC-CO₂ with or without polar co-solvent > low-pressure SC-CO₂.     

Supercritical fluid extraction of<Emphasis Type="Italic"> Cucurbita ficifolia</Emphasis> seed oil

Pumpkin, Cucurbita ficifolia, seed oil was extracted with supercritical carbon dioxide (SC-CO₂) in the temperature range of 308–318 K and in the pressure range of 18–20 MPa. In addition, the influence of the superficial velocity within a tubular extractor was studied. The oil content determined by a Soxhlet apparatus was 43.5%. Physical and chemical characteristics of the oil were obtained. The results in terms of free fatty acids contents were compared with those obtained when n-hexane was used as the solvent, and no significant differences between the oils extracted by both methods were found. The main fatty acid was 6-linoleic acid (about 60%), followed by palmitic acid (about 15%) and oleic acid (about 14%). Oxidative stability was studied by using the induction time determined by the Rancimat method. The oil obtained by supercritical fluid extraction (SFE) was less protected against oxidation (4.2 h for SFE-extracted oil and 8.3 h for the pumpkin seed oil extracted with n-hexane). The oil extracted by SC-CO₂ was clearer than that extracted by n-hexane, showing some refining. The acidity index was 5.5 for the n-hexane extracted oil. For the oils extracted by SC-CO₂, two analyses were made: for the oils obtained at 15 min of extraction time, for which the acidity indices varied from about 15 to 20, and for the remaining oils (extracted until 150 min), for which the acidity indices varied from about 2 to 2.6. The central composite nonfactorial design was used to optimise the extraction conditions, using the Statistica, version 5, software (Statsoft). The best results, in terms of oil recovered by SC-CO₂, were found at 19 MPa, 308 K and a superficial velocity of 6.0×10^–4 ms^–1.     

Effect of boldo (Peumus boldus M.) pretreatment on kinetics of supercritical CO2 extraction of essential oil

This work examined the effect of the solid matrix on supercritical carbon dioxide (SC CO₂) extraction of essentials oils from boldo leaves (Peumus boldus M.) subjected to rapid decompression of a CO₂-impregnated sample, conventional milling, and low-temperature milling. Low-temperature conditioning prior to milling decreased heat-driven losses of volatile compounds during milling, as attested by a higher extract yield for low-temperature (10.8 g extract/kg extract-free substrate) than conventionally (9.63 g/kg) milled sample. Extract yield was even larger for the rapidly decompressed sample (11.4 g/kg). Results of SC CO₂ extraction experiments carried out at 40 °C and 10 MPa were adjusted to a diffusional model using the effective diffusivity of the extract in the solid matrix (D_e) and a single partition of essential oils between solid substrate and SC CO₂ as best-fitting parameters. A microstructural factor (F_M), which was estimated as the ratio between the binary diffusion coefficient of the essential oil in SC-CO₂ under extraction conditions and D_e, was used to characterize the effect of sample pretreatment on extraction rates. Values of F_M for rapidly decompressed (202) and low-temperature milled (1740) samples were smaller than value for conventionally milled samples (2200), which revealed that the two first treatments disrupted secretory cavities in boldo leaves more effectively than the third. This was confirmed by light microscopy observations. The work included also measurements using oregano bracts (Origanum vulgare L.) as the substrate to confirm literature reports on the SC CO₂ extraction of pretreated bracts and to serve as a reference to our main results with boldo leaves. Trends with oregano coincided with those of boldo.     

Effects of supercritical fluid extraction parameters on lycopene yield and antioxidant activity

The effects of various parameters of supercritical carbon dioxide (SC-CO₂) fluid extractions of tomato skins on the extraction yields and antioxidant activities of lycopene-rich extracts were investigated. A Box–Behnken design was applied to study the effects of three independent variables (temperature ranging from 40 to 100 °C, pressure ranging from 20 to 40 MPa, and flow rate ranging from 1.0 to 2.0 mL/min) on lycopene yield. The model showed good agreement with the experimental results, by the coefficient of determination (r² = 0.9834). Temperature, pressure, and the quadratic term for the temperature of SC-CO₂ extraction were large significantly positive factors affecting lycopene yield (P < 0.05). The maximum total lycopene content of 31.25 μg/g of raw tomato was extracted at the highest temperature of 100 °C, 40 MPa and 1.5 mL/min. TEAC assay was applied to assess the antioxidant activity of lycopene-rich extracts from SC-CO₂ fluid extraction. The effects of SC-CO₂ fluid extraction parameters on the antioxidant activities of the extracts differed with the yield. For each unit of lycopene extract, the antioxidant activity level was constant below 70 °C, but then gradually decreased above 70 °C due to isomerization occurring as a result of the higher temperature. The ratio of all-trans-lycopene to the cis-isomers changed from 1.70 to 1.32 when the operating temperature was adjusted from 40 to 100 °C, indicating an increased bioavailability due to the generation of the cis-isomers. No significant effects of pressure or flow rate of SC-CO₂ fluid extraction on the antioxidant activity were observed.     

Supercritical carbon dioxide fluid extraction of Hibiscus cannabinus L. seed oil: A potential solvent-free and high antioxidative edible oil

The supercritical fluid extraction (SFE) trends and antioxidant activities of Hibiscus cannabinus seed oils were studied. SFE results indicate that extraction pressure is the major factor determining the oil yield. In comparison, classic Soxhlet extraction (SOX/L) yielded higher oil content than SFE (P < 0.05). However, no significant differences in oil content were observed in SFE at 600 bars/80 °C, rapid Soxhlet extraction (SOX/S) and conventional ultra-sonic assisted solvent extraction (SONIC) (P > 0.05). Antioxidant activities of H. cannabinus seed oils were compared with 7 types of commercial edible oils. DPPH scavenging activity test indicated that H. cannabinus seed oil extracted by SFE at 200 bars/80 °C possessed the highest antiradical activity whereas beta-carotene bleaching (BCB) assay revealed that all H. cannabinus seed oils (except for SFE at 400 bars/80 °C and 600 bars/80 °C) exhibited higher antioxidant activity than all commercial edible oils (P < 0.05). Thus, SFE – H. cannabinus seed oil may serve as an excellent source of solvent-free edible oil with high antioxidant properties.     

Supercritical CO2 cell breaking extraction of Lycium barbarum seed oil and determination of its chemical composition by HPLC/APCI/MS and antioxidant activity

The extraction parameters for oil extraction from Lycium barbarum seed including extraction pressure, temperature and time were optimized using an orthogonal test design. The optimum conditions for supercritical CO₂ extraction were as follows: extraction pressure, 30 MPa; extraction temperature, 45 °C; dynamic extraction time, 60 min; CO₂ flow, 25 kg/h. The oil yield under the conditions proposed was 19.28 g/100 g. The effect of cell wall breakage pretreatment was investigated by supercritical CO₂ rapid depressurization, and results indicated this pretreatment could result in a rapid and efficient extraction. A sensitive fluorescent reagent 2-(11H-benzo[a]carbazol-11-yl) ethyl 4-methylbenzenesulfonate (BCETS) was utilized as pre-column labeling regent to determine fatty acids (FA) from Lycium barbarum seed oils obtained by different extraction methods. The main FA were: C18:2, C18:1, C16, C20:6, C18:3, and C20. The oil from L. barbarum seed exhibited excellent antioxidant activity in 2,2-diphenyl-1-picrylhydrazyl（DPPH）radical scavenging assay and β-carotene bleaching test, and its antioxidant activity compared well with the references ascorbic acid and α- tocopherol.     

Comparison of essential oil compositions of Salvia mirzayanii obtained by supercritical carbon dioxide extraction and hydrodistillation methods

Essential oil of Salvia mirzayanii cultivated in Iran was obtained by hydrodistillation and supercritical (carbon dioxide) extraction methods. The oil was analysed by capillary gas chromatography using flame ionization and mass spectrometric detections. The compounds were identified according to their retention indices and mass spectra (EI, 70 eV). The effects of different parameters such as pressure, temperature, modifier volume and extraction times (dynamic and static) on the supercritical fluid extraction (SFE) of S. mirzayanii oil were investigated. The results showed that, under a pressure of 35.5 MPa, temperature of 35 °C, 6% methanol, dynamic extraction time of 50 min and static extraction time of 30 min, extraction was more selective for the linalyl acetate. Thirty four compounds were identified in the hydrodistilled oil. The major components of S. mirzayanii were linalyl acetate (7.6%), 1,8-cineole (8.0%), linalool (9.0%) and 8-acetoxy linalool (11.0%). However, by using supercritical carbon dioxide in optimum conditions, only three components contain more than 63% of the oil. The yield of the obtained oil based on hydrodistillation was 2.20% (v/w). Extraction yield based on the SFE varied in the range of 1.50–9.67% (w/w) under different conditions. The results revealed that, in Iranian S. mirzayanii oil, linalyl acetate is a major component.