super critical fluids and the food industry

Vol. 1, 2002—COMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY 33© 2002 Institute of Food Technologists

SupercriticalFluids and theFood Industry

N.L. Rozzi and R.K. SinghDept. of Food Science and Technology

University of GeorgiaAthens,GA 30602-7610

Direct inquiries to author Singh(E-mail: [email protected])

Abstract: This paper reviews the use of supercritical fluids in various aspects of the food industry, and is divided into sixdifferent areas: modeling of supercritical fluids, separation of extracted material, supercritical carbon dioxide as a solventfor extraction, supercritical fluids and analytical uses, and supercritical fluids and novel methods of food processing. Anassortment of solutes are covered in the extraction section of the paper, including antineoplastic agents and lipids. Theanalytical methods section covers supercritical fluid chromatography, pesticide detection, and lipid analysis. The novelmethods section discusses supercritical fluid extrusion and a new method of eliminating hexane from soybean oil.

Keywords: Supercritical Fluid, Carbon Dioxide, Review

1. Supercritical fluids have a higher diffusion coefficient andlower viscosity than liquids.

2. Absence of surface tension allows for their rapid penetrationinto the pores of heterogeneous matrices, which helps enhanceextraction efficiencies.

3. Selectivity during extraction may be manipulated by varyingthe conditions of temperature and pressure affecting the solubilityof the various components in the supercritical fluid.

4. Supercritical fluid extraction does not leave a chemical resi-due.

5. Supercritical fluid extractions can use carbon dioxide gas,which can be recycled and used again as part of the unit opera-tion (Rizvi and others 1994).

Supercritical carbon dioxide has been researched for potentialapplications in many different fields including Food/ Agriculture,Analytical/Supercritical Fluid Chromatography, and the Petro-chemical/Chemical Industries. Figure 1, presents the breakdownof research areas of recent research articles (1999-2000). Thesearticles were determined by performing a search on Current Con-tents for articles that contain the terms carbon dioxide and super-critical fluid, and resulted in 264 articles being obtained. FromFigure 1 it can be seen that 32% of the research articles were fromthe Food and Agriculture research areas and an additional 4% ofthe research articles were in Pesticide research. Combined, this is12% greater than the next largest area (Petrochemical). To furtherexpand on this literature search, a second search was performedon Food Science and Technology Abstracts using the same termsas the previous search. In addition, the timeframe for the searchwas increased from 1999-2000, to 1995 to 2000. This search re-sulted in 105 articles being produced. The results of this searchare displayed in Figures 2 and 2a. Figure 2a is a breakdown oftopics found in the Analysis section of Figure 2. Based on thesesearches, this paper discusses Modeling of Supercritical Fluids,Separation of Extracted Materials, Extraction from Botanical Sam-ples, Extraction of Lipids, Supercritical Fluids and Analytical Uses,and Supercritical Fluids and Novel Methods of Food Processing.

IntroductionSupercritical fluid extraction utilizes the ability of certain chemi-

cals to become excellent solvents for certain solutes under a com-bination of temperature and pressure. The solvent becomes super-critical when it is raised above its critical point for both tempera-ture and pressure (Table 1). In the case of carbon dioxide, the crit-ical point is at 31.06 °C and 7.386 MPa. CO2 is the solvent ofchoice for use in supercritical fluid extraction because it is,“GRAS, nonflammable, noncorrosive and inexpensive (Rizvi andothers 1994)”. In addition, CO2 has a low critical temperature,which can help prevent thermal degradation of food componentswhen they are being extracted. The problem with most of the flu-ids listed (Table 1) besides CO2 is that they are either difficult tohandle and/or obtain in a pure form. The advantages of supercriti-cal fluid extractions are:

Table 1—Critical points of selected gasses

Critical CriticalFluid Temperature (K) Pressure (MPa)

Hydrogen 33.25 1.297Neon 44.40 2.6545Nitrogen 126.24 3.398Argon 150.66 4.860Oxygen 154.58 5.043Methane 190.55 4.595Krypton 209.46 5.49Carbon Tetrafluoride 227.6 3.74Ethylene 282.35 5.040Xenon 289.7 5.87Carbon Dioxide 304.17 7.386Ethane 305.34 4.871Acetylene 308.70 6.247Nitrous Oxide 309.15 7.285Chlorodifluoromethane 369.27 4.967Propane 369.85 4.247

Rizvi and others 1994

34 COMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY—Vol. 1, 2002

CRFSFS: Comprehensive Reviews in Food Science and Food Safety

Modeling of Supercritical FluidsThe solubility of substances in supercritical fluids has been de-

scribed by many different methods. Two examples of these meth-ods will be included in this paper. One method utilizes: solubilityparameters and the other is based on process modeling. Each ofthese methods has their benefits and drawbacks. Solubility pa-rameters describe the solubility of the substance in supercriticalCO2 under “laboratory conditions” and not during conventionalextraction processes. In addition, the solubility parameter is alsoinfluenced by the equation of state, which is used to calculatesome variables needed for the solubility parameter. Two equationsof state which can be used are the Peng-Robinson Equation ofState and the Sanchez-Lacombe Model. The other approach to

modeling supercritical fluid extractions is to model the process it-self. Sovova (1994) developed a model based on a mass balanceof the process to describe the extraction of natural products withsupercritical fluids. This model takes into account the porosity ofthe raw material from which the target compound is being extract-ed, the density of the solid phase and the length of time used toextract the target compound. Although each method is vastly dif-ferent from each other, both provide important information aboutthe extraction process.

Solubility ParameterThe solubility parameter is the solvating capability of a com-

pressed gas as described by the Hildebrand Solubility Parameter.The Hildebrand Solubility Parameter is a rough measure of theability of a solvent to dissolve a solute. Equation 1 relates the solu-bility parameter to the density of both the gas and the liquid by:

(1)

where d is the solubility parameter, Pc is the critical pressure, r isthe gas density and rliq is the density of the liquid (Rizvi and oth-ers 1994). From this equation, the effect of pressure on the solu-bility parameter can be seen. When the pressure is at atmosphericpressure, the solubility parameter is zero. As the pressure increas-es the solubility parameter increases, with great changes takingplace as the critical pressure is reached (Rizvi and others 1994).

Although this equation can be used with some success to de-scribe the solubility of some solutes in supercritical fluids, it doesnot work in all cases and must be used with careful attention be-ing paid to the original work of Hildebrand and the warnings giv-en there. Some of these warnings are that it is dangerous to em-ploy the solubility parameters for esters, ketones, alcohols andother polar liquids. This should warn people against using theHildebrand solubility parameter as the final word and any as-sumptions made using the solubility parameters should be

Figure 1—Results of Current Contents search using “super-critical fluids” and “carbon dioxide” as search terms (1999-2000)

Figure 2(a)—Distribution of target analytes from analysis sec-tion of figure 2

Figure 2—Results of Food Science and Technology Abstractssearch using “supercritical fluids” and “carbon dioxide” assearch terms (1995-2000)

Vol. 1, 2002—COMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY 35

Supercritical fluids and the food industry . . .

backed up with experimental evidence (McHugh 1994).Allada (1984) proposed a new equation to define the solubility

parameter (Equation 2). This equation uses the, “internal energy ofthe gas relative to isothermally expanded ideal gas state as the co-hesive energy of the gas”, (Allada 1984).

(2)

In Equation (2) dr is the reduced solubility parameter, R is theuniversal gas constant, C1 is a conversion factor to make the unitscancel, E is the internal energy of the gas at temperature T andpressure P. Pr and Tr are the reduced pressure and reduced tem-perature respectively. The reduced pressure and reduced temper-ature are related to (P/Pc) and (T/Tc) where P and T are the currentpressure and temperature, and Pc and Tc are the critical pressureand temperatures respectively. Z is the compressibility factor andE* is the internal energy of the gas, “isothermally expanded to‘zero’ pressure where intermolecular separation is infinite and in-termolecular cohesive force is zero,” (Allada 1984).

The values for the compressibility factor and the (E* - E)/TC andZ can be calculated by using equations (3 to 6)

(3)

(4)

(5)

(6)

where H is the enthalpy of the supercritical fluid and H* is the en-thalpy of the ideal gas at the same temperature (Allada 1984). Thevalues for the (H* – H)/Tc and Z data are obtained from the book,Chemical Process Principles, Part Two, Thermodynamics, by Hou-gen and Watson (1947). This equation works well for predictionof the solubility of a substance in different supercritical fluids atdifferent pressures. This equation (Equation 2) does not, however,work well for changes in temperature. To account for temperatureeffects, it would be necessary to include a solvent-solute interac-tion represented by a cross-virial coefficient (Allada 1984).

Peng-Robinson Equations of StateEquations of state can be used to describe the behavior of sol-

utes being dissolved in supercritical fluids. A favored equation todescribe this action is the Peng-Robinson equation (Smith 1996):

(7)

where Z is the compressibility factor, P is the pressure, T is thetemperature and R is the Universal Gas Constant. This equation isused to describe the behavior of pure species. It can be modifiedto describe the behavior of mixtures which results in Equation 8,where a and b are mixing values which are related to aI and bI by

mixing rules. In addition, « and s are equation specific constants.The values for the Peng-Robinson equation of state are –0.414214 and 2.414214, respectively (Smith 1996).

(8)

Equation 8 can be displayed as:

(9)

where

(10)

(11)

am is the attraction parameter of the mixture, bm is the mixture’svan der Waals co-volume, X is the mole fraction in the liquid orsupercritical fluid phase, and i and j represent the different com-ponents of the mixture. aij comes from the mixing rules presentedby van der Waals, which utilizes only one interaction parameter(Rizvi and others 1994). Care should be taken when using thesemixing rules though (Equations 10 and 11) since the mixing rulesare for cubic equations of state. Cubic equations of state only ac-count for dispersion forces and not for hydrogen bonding, whichcould be occurring during the extraction. This possible hydrogenbonding will prevent random distribution of the solute in the sol-vent, thus causing the need for a different set of mixing rules(McHugh 1994).

One different set of mixing rule equations which can be usedare equations (12) and (13). These equations incorporate two newparameters into the mixing rule. These parameters are dij and hijwhich represent the interaction and size parameters respectively.These data parameters are obtained by regressing the P-x dataand fitting it to the equation of state.

(12)

(13)

The addition of these two parameters greatly improve the fit ofthe data for some solutes, but they still need to be investigated foruse with other solvent-solute combinations (McHugh 1994).

Sanchez-Lacombe ModelAnother equation of state is the Sanchez-Lacombe equation of

state (14), which is based on the lattice-fluid theory, which as-sumes that the polymer has a flexible liquid structure. This limitsthe use of this equation to polymers which are noncrystalline, notcross-linked or slightly crosslinked, and above their glass transi-tion temperature. This equation has been used to model the solu-bility of supercritical CO2 in solid, amorphous polymers or moltenpolymers. In addition, it also describes the subsequent swelling ofthe polymer as the supercritical fluid dissolves in the polymer.Three assumptions need to be made to use the Sanchez-Lacombe



equation. These assumptions are:(1) The solubility of the gas in the polymer represents equilibri-

um data.(2) The solubility of the polymer in the high-pressure gas phase

is essentially zero.(3) The amorphous polymer above its glass transition tempera-

ture can be modeled as a liquid.

(14)

where rr, Pr, and Tr, are the reduced density, pressure and temper-ature. r represents the number of lattice sites represented by amolecule. As compared with the Peng-Robinson equation of state,which has only two mixing rules, the Sanchez-Lacombe equationhas three adjustable characteristics (Kriszka 1988). The variablesin this equation are:

(15)

(16)

(17)

(18)

(19)

(20)

(21)

(22)

where:ÿε = Internal energy per mer

R = Universal gas constantÿÿ = Closed-packed volume of a mer

V* = Closed pack volume of the mixtureM = Molecular weight

The values for CO2 of r*, T*, and P* are 1.510 (g/cm3), 305 (K),and 5670 (atm) respectively (Kiszka 1988).

Process ModelingThe process of extracting natural products by supercritical fluid

extraction can be modeled using the model developed by Sovova(1994). This model is based on the following assumptions:

(1) The solvent flows axially through a bed of raw material in acylindrical extractor.

(2) The solvent is solute-free upon entering the extractor.(3) The solute is partially exposed to the solvent due to previous

milling (Sovova 1994).The mass balance for the process is described by Equations

(23) and (24) below, where r is the solvent density, « is the porosi-ty, y is the solvent-phase concentration related to the solute-freesolvent, x is the concentration related to solute-free solid phase, Uis the superficial velocity of the solvent, h is the axial coordinate,rs is the density of the solid phase, t is time, and J(x,y) is the masstransfer rate.

(23)

(24)

Using the values for x and y solved in the mass balances, thecurves describing the extraction process can be determined bythe following:

(25)

where e(t) is the mass extracted relative to the mass of the solute-free solid phase, xo is the concentration related to the solute-freesolid phase, H is the height of the bed, and x(t,h) is the concentra-tion related to the solute-free solid phase as a function of time (t)and height (h). This modeling system can be used to describe theextraction of natural products using supercritical CO2 (Sovova1994). This model has been successfully applied by Mira and oth-ers (1996), Perrut and others (1997), Coelho and others (1997),and King and others (1997) in modeling the extraction of naturalproducts from plant sources.

Separation of Extracted MaterialExtraction is the most common use for supercritical fluids. The

process is simple, with the major process parameters being tem-perature, pressure and flow rate of the supercritical fluid. Figure 3presents a basic flow diagram for supercritical fluid extraction,and Figure 4 illustrates a similar system that is designed for frac-tionation experiments. The most important aspect of this flow dia-gram is the separation of the extracted material from the supercrit-ical fluid. This section discusses multiple methods for the separa-tion of extracted material from supercritical fluids.

Figure 3—Flow diagram of a supercritical fluid extractionsystem

Figure 4—Flow diagram of a supercritical fluid fractionationsystem



There are multiple methods that can be utilized to separate thesolute from the supercritical fluid, which is acting as the solvent.There are three basic concepts that can be used to accomplishthis. The first is to change the temperature or pressure so that thesolvent capability of the supercritical fluid changes. The other is to“wash” the solute out of the supercritical fluid using a solvent thatcan strip the solute from the supercritical fluid. In addition to theseparation of the solute from the supercritical fluid, it is possibleto separate multiple solutes within the supercritical fluid using apacked column.

The simplest method to remove the solute from a supercriticalfluid is to change the pressure of the supercritical fluid so that ei-ther the fluid is no longer supercritical or that the solute is nolonger soluble in the supercritical fluid. Snow and others (1997),Barth and others (1995), and Sugiyama and Saito (1988), all uti-lized this method to remove their respective solutes from the su-percritical fluid. In all three cases the individuals performing thestudy routed the solute/solvent combination through a restrictionvalve and into a collection vessel. Inside the collection vessel, thepressure was reduced to room pressure, causing the supercriticalfluid to return to its gas state, and the solvent to be released intothe collection vessel. Inside the collection vessel, there can be asolvent to receive the solute, so that further analysis can be per-formed. Other times the vessel may be left empty so that the solutecan crystallize upon leaving the supercritical fluid.

Another variation of the previous method to remove the solutefrom the supercritical fluid is to change the temperature of the su-percritical fluid. This may cause the fluid to leave the supercriticalregion, but it allows for the pressure of the fluid to be maintained.This could save money by allowing for the pressurized fluid to berecirculated, without having to repressurize it. This means that lessmoney would have to be spent on the energy to pressurize thefluid. Lancas and others. (1990) and Vilegas and others (1994)both utilized this method to remove their respective solutes fromthe supercritical fluid. This method simply involves the removal ofthe solute by dropping the temperature of the solvent until the sol-ute is no longer soluble and precipitates from the supercritical flu-id. This is also referred to as a cryogenic trap. Once the extractionhas been completed, the system can be depressurized and the ex-tract can be removed from the sample chamber.

The solute can also be removed from the supercritical fluid by“washing” it from the solvent. This allows for the process to bemaintained at a constant pressure much as the cryogen trap did,but it also allows for the removal of the solute from the processwithout having to shut the process down. An example of this typeof removal is used in the decaffeination of green coffee beans toremove the caffeine from the supercritical CO2 (McHugh 1994).

If more than one chemical is extracted by the supercritical fluid,column chromatography can be used, utilizing the supercriticalfluid as the mobile phase. As with HPLC, both normal and re-versed phase chromatography can be utilized to separate the sol-utes depending on their polarity. The retention times on these col-umns can be correlated to the solubility of the solute in the super-critical fluid (Sakaki 1994). McHugh and Krukonis (1994) andSakaki and others (1994) used column chromatography to sepa-rate multiple solutes from supercritical fluids.

Supercritical Carbon Dioxide as a Solvent for Extraction

Supercritical Fluid Extraction of Botanical SamplesSupercritical fluids have been used to extract a wide range of

analytes from botanical samples. These analytes range from essen-tial oils to phytochemicals, and can include lipid extraction. Theseextracts have been used for analytical purposes, supplementation

purposes, and flavor and fragrance purposes. Some companieshave even begun to market botanical extracts obtained by super-critical CO2 extraction. One company in particular, Flavex Natur-extrackte, Rehlingen, Germany, specializes exclusively in SFE pro-duced products and markets them internationally. Table 2 in-cludes a brief list of different botanicals, which have been investi-gated since 1997.

Separation of Antineoplastic Agents: Antineoplastic agents canbe extracted from plant materials in addition to flavors and essen-tial oils. Krukonis and others (1979) performed a brief extractionstudy on plants which were confirmed by the National Cancer In-stitute (NCI) to contain antineoplastic agents. One example ofthese species is maytansine which is contained in materialsB628318, B628259, and B628201. The materials that were usedin the study are listed in Table 3 (McHugh and Krukonis 1994).

In this experiment approximately 20 grams of plant materialwas extracted using 200 L of supercritical CO2. This was com-pared with the NCI protocol that utilized a Soxhlet extraction with95% ethanol. The samples were then analyzed in vitro for bioac-tivity using 9KB leukemia cells. The results of this comparison aredisplayed in Table 4 and are expressed in terms of the ED50 value.This value is defined as the extract concentration in which 50% ofthe cell growth is inhibited, and is expressed in mg/l. The lowerthe ED50 value, the more cytotoxic the extract. From the results inTable 4, it can be seen that all of the extracts exhibited cytotoxicresults. In addition, 2 samples exhibited an ED50 value less thanthat of the Soxhlet extraction (McHugh and Krukonis 1994). Dueto the small amount of raw material provided and the lack of anypure material that could be used for solubility testing, this studyserves mainly as a screening study though, that indicates the po-tential for using supercritical fluids to isolate antineoplastic agents.If more materials were provided for in this study, determination of“ideal” extraction conditions, or a method to fractionate the ex-tracts could have been developed. To prove this point, a secondextraction of sample B638318 was performed. This time the ex-tract was split into 2 fractions, fraction 1 consisted of the materialswhich were extracted by the first 20 L of CO2 and fraction 2 usedthe remaining 180 L of CO2. After analysis of both these samples,it was found that the second fraction yielded a much lower ED50value (0.03 vs 0.19 obtained in fraction 1) (McHugh and Krukonis1994).

Annato: Bixin, a pigment used for food coloring obtained fromthe seeds of annatto (Bixa orellana L.) was extracted using super-critical carbon dioxide. A range of pressures (40.41 MPa to 60.62MPa) and temperatures (40 and 80 °C) were tested. In addition, 5% chloroform, 10% chloroform, 5 % methanol, 10 % methanol,and 4% acetonitrile containing 0.05% trifluoroacetic acid wereused as co-solvents in the extraction process. After analysis byHPLC, it was found that the optimum conditions for extraction ofbixin was 60.62 MPa and 40 °C with 4% acetonitrile containing0.05% trifluoroacetic acid as the co-solvent (Anderson and others1997).

Cloudberry Seed: Cloudberry seeds produce oil that is low insaturated fats, and contains relatively high amounts of toco-pherols and carotenoids. The extraction of Cloudberry seed oil bysupercritical fluid extraction was compared to that of a Soxhlet ex-traction using diethyl ether as the solvent. The range of extractionconditions consisted of 9 to 30 MPa at either 40 °C or 60 °C. Theextracts were analyzed by GC-FID and HPLC for their fatty acidand carotenoid/ tocopherol content respectively. There was nosignificant difference in the fatty acid composition of any of theextracts; the carotenoid content did not increase at pressures over15 MPa, and the amount of tocopherols extracted decreased withincreasing pressure (Manninen and others 1997).

Grape Seeds: Phenolic compounds and lipids were extracted



from white grape seeds and analyzed for phenolics (Palma andTaylor 1999) and for the extracts antimicrobial activity (Palma andothers 1999). The optimum extraction conditions for phenolicswas determined to be CO2 at a density of 0.95 g/ml and 55 °Cwith a co-solvent of 10% methanol with the most influential vari-able on the extraction being the CO2 density, followed by the na-ture of the co-solvent, percentage of co-solvent, and extractiontemperature (Palma and Taylor 1999). In addition, it was foundthat the extract could be split into two fractions; those compoundsobtained by pure CO2 and those compounds obtained with CO2and a co-solvent. The first fraction contained mainly fatty acidsand sterols, while the second fraction contained phenolic com-pounds. The first fraction was found to have a high degree of anti-

microbial activity while the second fraction tested positive for anti-fungal activity (Palma and others 1999)

Paprika: Lipids, carotenoids and tocopherols were extractedfrom paprika and analyzed by HPLC. Vesper and Nitz (1997)compared the use of supercritical CO2 at 35 MPa and 50 °C to theuse of hexane and found that hexane had slightly higher caro-tenoid content while the extracts obtained by SFE had a higherwater content (Vesper and Nitz 1997a). After storage studies ofthese extracts at 40 °C, it was found that the samples extracted bySFE had reduced fatty acid stability compared to the samples ob-tained by hexane extraction (Vesper and Nitz 1997b). Jaren-Galanand others (1999) and Skerget and others (1998) analyzed the ef-fects of temperature and pressure on the composition of the pa-

Table 2—Summary of publications on extraction methods from plant and botanical samples using supercritical fluid extrac-tion (Pub. Year >1994)

Pressure AnalyticalSample Analyte(s) (MP a)/ T (°C) Instrument Reference

Annato trans-Bixin 40 to 60/40 HPLC Anderson and others 1997

Black Pepper Essential Oil 20 to 32/45-65 GC-FID Tipsrisukond and others 1998Ferreira and others 1999

Buriti Carotenoids 20-30/40-55 GC-FID De Franca and others 1999Lipids Spectrophotometry

Caraway Seeds Carvone 7.5-300/32-75 GC-FID Baysal and Starmans 1999Limonene

Carrot Carotenes 60.6/40 HPLC Chandra and Nair 1997

Chamomile Flavinoids 20.2/40 GC-MS Scalia, Giuffreda and Pallado 1999

Cloudberry Seed Lipids, b-carotene, 9-30/40-60 GC-FID, HPLC Manninen and Kallio 1997Tocopherols Manninen and Laakso 1997a

Manninen and Laakso 1997bManninen and others 1997

Clove Bud Essential Oil 8-20/50-50 GC-MS Della Porta and others 1998

Coriander Seed Essential Oil 20-30/35 GC-FID Illes and others 2000

Fennel Seeds Fennel Oil 8.1/40 GC-MS Simandi and others 1999

Grapefruit Limonene and Terpines 8-25/40 GC-FID Poiana, Sicari and Mincione 1998

Grape Seeds Polyphenolic compounds 45.6/35 GC-FID, HPLC Palma and others 1999Palma and Taylor 1999Palma and others 2000

Lavender Essential Oil 9/ 48 GC-MS Reverchon and Della Porta 1995

Lovage Essential Oil 8-30/10-50 GC-FID Dauksas and others 1998

Onion Essential Oil 10-30/45-65 GC-FID Sass-Kiss and others 1998Sass-Kiss and others 1998a

Paprika Lipids, carotenoids, 35/50 HPLC, GC-FID Skerget and others 1998and tocopherols 15/40 Jaren, Nienaber and Schwartz 1999

13.7-41.3/40 Vesper and Nitz 1997bVesper and Nitz 1997aIlles and others 1999

Peppermint Essential Oil 6.5-10/25-40 GC-MS Ammann and others 1999Aleksovski and others 1999

Olive Products Tocopherols 35/50 SFC-FID Ibanez and others 2000Phenol Compounds 33.4/100 Electrospray-MS Le Floch and others 1998

Oregano Essential Oil 8-30/40 GC-FID Simandi and others 1998

Rosemary Antioxidants 10-16/37-47 GC-MS Ibanez and others 1999Essential Oils 10-40/60 Senorans and others 2000

Lopez-Sebastian and others 1998Coelho-Luiz and others 1997Bauman and others 1999Tena and others 1997

Sage Essential Oils 10-40/60 GC_MS Ronyai and others 1999Antioxidants Bauman and others 1999

Spearmint Leaf Essential Oil 27.6/60 GC-MS Pino, Garcia and Martinez 1999

Star Anise Essential Oil 8-20/50 GC-MS Della and others 1998



prika extract. It was found that the selectivity of CO2 is higher atlower temperatures (40 °C) and that the optimum pressure for ex-tracting aromatic compounds is 15 MPa and coloring com-pounds is 40 MPa (Skerget and others 1998). After further analy-sis, it was determined that the pigments isolated at lower pressuresconsisted mainly of b-carotene. Extracts obtained at higher pres-sures contained a greater proportion of capsorubin, capsanthin,zeaxanthin, and b-cryptoxanthin and little b-carotene. It was fur-ther determined that a two stage extraction could be used to ex-tract a majority of the compounds present (200% compared toreference). This extraction first consisted of an extraction at 40 °Cand 13.8 MPa followed by an extraction at 40 °C and 41.3 MPa(Manuel and others 1999).

Rosemary: Antioxidants from rosemary were extracted anddearomatized by supercritical CO2 for use in natural supple-ments. The extraction of rosemary oil was initially modeled by Co-elho, and others (1997) using the model developed by Sovova(1994). Ibanez and others (1999) continued this work by utilizingfractionation to further separate the essential oil extracted from therosemary plants into two different fractions. These fractions haddifferent compositions and antioxidant activities (Ibanez and oth-ers 1999). Lopez-Sebastian and others (1998) utilized supercriti-cal CO2 remove the rosemary aroma from the extracts obtainedby solvent extraction. This produces an extract which is more suit-able for use in food products. In addition, this process also re-moves almost 100% of the residual solvent left from the extractionprocess (Lopez-Sebastian 1998).

Supercritical Fluid Extraction of LipidsSupercritical carbon dioxide has been utilized to extract lipids

from an assortment of matrices. Some of these extractions havebeen used to analyze the fat content of different food products.Other extractions have been used to obtain pure lipid extracts orto produce products that contain a reduced amount of certain lip-ids or other compounds such as cholesterol. Table 5 presents alist of some current articles in the field.

Dairy Products: Dairy products have been subjected to super-critical fluid extraction to fractionate lipids and isolate vitamins forquantification. Berg and others (2000), and Turner and Mathias-son (2000) utilized supercritical CO2 to remove vitamin A and Efrom powdered milk, fluid milk and meat. The extraction condi-tions for both studies were 80 °C and 37 MPa. Berg and others(2000) furthered this research by using Hydromatrix as a waterabsorbent to reduce the adverse effects of the water component ofmilk on the extraction process. This allowed all of the vitamin Aand E to be extracted from a 0.5 gram sample in 80 minutes,shorter than conventional methods. In addition to vitamins, thedistribution of polychlorinated biphenyls (PCB’s) in the differentmilk fat fractions was studied using supercritical fluid extraction.Ramos and others (2000) utilized supercritical CO2 to fractionate

the milk fat into 4 different fractions. These factions were short-chain triglycerides (SCT), medium-chain triglycerides (MCT), long-chain triglycerides (LCT) and cholesterol. From this research it wasfound that PCB’s can be found predominately in the SCT, MCTand cholesterol fractions of the milk fat (Ramos and others 2000).

Professor S.S.H. Rizvi has been a virtual front runner in the useof supercritical fluids to fractionate milk fats. In 1992 he pub-lished an article on the fluid liquid equilibria of anhydrous milkfatwith supercritical CO2 (Yu and others 1992). Following this re-search, Shukla and others (1994) studied the effect of using milkfat obtained by supercritical fluid extraction on the physicochemi-cal and rheological properties of butter. This research demonstrat-ed the ability to use supercritical CO2 to produce butter with spe-cific properties such as reduced moisture content, elevated melt-ing points, and lower cholesterol. This research was expandedfrom butter to milk fat which can be used in other products byBhaskar and others (1998).

Meats: Supercritical fluid extraction has been utilized to extractlipids from a variety of meats, including pork and beef. Thesemethods have been developed for analytical purposes, and arediscussed in detail in analytical section of this paper.

Nuts and Seeds: Lipids have been extracted from a series of dif-ferent types of nuts and oil seeds. Some examples of these are pe-cans and rice bran. A reduction in the lipid content of pecans canincrease their storage life (Alexander, Brusewitz and Maness1997). From this study it was determined that the optimum extrac-tion conditions for pecan oil was 66.8 MPa and 75 °C. The kinet-ics of this extraction was also determined to be limited by the sol-ubility of pecan oil in supercritical CO2 for the initial part of theextraction, while it was diffusion limited for the second half of theextraction (Alexander and others 1997). During SFE the possibilityof breakage of the pecan kernels increases with increased mois-ture content of the kernels (Bellmer and Brusewitz 1999). This ef-fect was increased when a short depressurization time was used.A reduction in the moisture content of the pecans to a final mois-ture content range of 3.5% to 11.0% before lipid extraction canreduce the amount of kernel breakage (Bellmer and Brusewitz1999).

Rice bran is a by-product of rice milling that contains 15 to20% oil by weight which could be of value to the food and phar-maceutical industry (Shen and others 1996). This oil has been ex-tracted by SFE. Shen and others (1996) reported that rice bran oilwas extracted with subcritical and supercritical CO2 at a tempera-ture range of 0 to 60 °C and pressures of 17 to 31 MPa. This re-search was furthered by Shen and others. (1997) by the additionof fractionation to separate water and free fatty acids from the ex-tract. Kuk and Dowd (1998) continued this research by compar-ing the quality of oil extracted by supercritical fluid extraction ascompared to that of hexane extraction. It was found that at tem-peratures of 80 °C the quality of oil extracted by supercritical fluid

Table 4—Cytoxicity of extracts as measured by ED50 values(mg extract/l C2H5OH)

Supercritical Carbon Ambient TemperaturePlant Material Dioxide Extraction Ethanol Extraction

B628259 30.0 11.0B628318 0.25 0.11B634635 24.0 43.0B638786 4.0 >100.0B805592 21.0 126.0B806512 14.0 6.2

Reprinted with permission from McHugh and Krukonis 1994.

Table 3—Plant materials analyzed for anticancer agents

NCIDesignation Specific Name Variety Origin

B628201 Maytenus senegalensis Celastraceae TanzaniaB628259 Maytenus senegalensis Celastraceae KenyaB628318 Maytenus senegalensis Celastraceae IndiaB634635 Gypsophilia Caryophyllaceae MichiganB638786 Citharexylum caudatum Verbenaceae PanamaB805592 Maquire calophylla Moraceae PeruB806512 Rollinia papilliionela Annonaceae Peru

Reprinted with permission from McHugh and Krukonis 1994.



extraction was far superior to that of oil obtained by hexane ex-traction (Kuk and Dowd 1998).

Seaweed and Fungi. v-3 fatty acids were extracted from brownseaweed, Sargassum hemiphyllum (Turn.) C., and fungi, Cunning-hamella echinulata and Pythium irregulare, by SFE for potentialuse in functional foods and nutraceuticals. Chung, and others(1998) reported that they were able to obtain yields of total andindividual v-3 fatty acids that were significantly greater than thoseobtained by Soxhlet extraction by using extraction conditions of37.9 MPa and 50 °C. They also found that the concentration of to-tal polyunsaturated fatty acids increased significantly and total sat-urated fatty acids decreased significantly with increasing pressureand solvent density as measured by the ratio of saturated to unsat-urated fatty acids. Supercritical CO2 was used to extract fungal oilcontaining g-linolenic acid from Cunninghamella echinulata withsimilar results (Certik and Horenitzky 1999). It was found that su-percritical CO2 extraction at 30 MPa and 50 °C yielded greaterthan 110% of the g-linolenic acid that was obtained by chemicalextraction. Walker and others (1999) also extracted v-3 fatty acids

using SFE, but they had the aid of surfactants which will be dis-cussed later in this article.

Supercritical Fluids and Analytical UsesSupercritical carbon dioxide has been utilized in multiple meth-

ods of analysis. Supercritical carbon dioxide is used as either anextraction medium, as in rapid analyses for fat content, or as amobile phase, as in supercritical fluid chromatography. This sec-tion covers the use of supercritical fluids in the detection of fatcontent, pesticide residues, and supercritical fluid chromatogra-phy.

Rapid Analysis for Fat Content: Supercritical fluids have beenused to determine the fat content of numerous products rangingfrom beef to oil seeds and vegetables. Taylor and others (1997)compared traditional methods of analysis for fat content to newermethods developed with supercritical fluid extraction. For theanalysis of fats content in soybeans, sunflower, safflower, cotton-seed, rapeseed and ground beef, it was found that supercriticalfluid extraction yielded higher recoveries than those obtained by

Table 5—Summary of Publications on Lipid Extraction Studies Using Supercritical Fluid Extraction (Pub. Year >1995)

Pressure AnalyticalSample Analyte(s) (MP a)/ T (°C) Instrument Reference

Brown Seaweed Fatty Acid Composition 24.1-37.9/40-50 GC-FID Cheung, Leung and Ang 1998

Butter Oil Cholesterol 10-27.6/40-70 GC-FID Mohamed, Neves, andKieckbusch 1998

Corn Bran Ferulate phytosterol 13.8-69/40-80 SFC Taylor and King 2000esters

Cotton Seed Fatty Acid Composition 51.7-62/100 GC-FID Taylor, Eller and King 1997Gravametric

Cunninghamella echinulata Fatty Acid Composition 20-35/40-70 GC-FID Certik and Horenitzky 1999

Ground Beef Fatty Acid Composition 38/80 GC-FID King and others 1996Taylor, Eller and King 1997

Milk Fat Lipid Profile 6.9-17.2/40-60 GC-FID Bhaskar and others 1998Vitamins HPLC Ramos, HernandezSolid Fat content, PCBs Pulsed NMR and Gonzalez 2000

DSC Turner and Mathiasson 2000Berg and others 2000Manganiello, Rios, and Valcarcel 2000

Oat Bran Digalactosyldi- 40/50-70 SFC Andersson, Demirbuker andacylglycerols Blomberg 1997

Pecan Fatty acid composition 41.3-66.8/45-75 GC-FID Alexander, Brusewitz andand product breakage Maness 1997

Li, Bellmer and Brusewitz 1999

Pistachio Texture and Sensory 20.7-34.5/50-70 Instron Universal Palazoglu and Balaban 1998Attributes Testing Machine

and Sensory Panel

Pork Cholesterol/Fat Content 7.3-34/50-150 HPLC Lin and others 1999Texture and Sensory TLC Berg and others 1997Attributes Sensory Panel

Hunter Colorimeter

Pythium irregulare Fatty Acid Composition 13.7-27.5/40-60 GC-FID Walker, Cochran and Hulbert 1999

Rapeseed Fatty Acid Composition 51.7/100 HPLC Bruhl and Matthaus 1999Tocopherol Content GC-FID

Rice Bran Fatty Acid Composition 17-31/0-60 GC-MS Shen and others 1996a-tocopherol sterols 48.2-62/70-100 HPLC Shen and others 1997Moisture Kuk and Dowd 1998

Safflower Fatty Acid Composition 51.7-62/100 GC-FID Taylor, Eller and King 1997

Soybean Fatty Acid Composition 51.7-62/100 GC-FID Taylor, Eller and King 1997Bruhl and Matthaus 1999

Sunflower Fatty Acid Composition 51.7-62/100 GC-FID Taylor, Eller and King 1997Bruhl and Matthaus 1999



the AOCS approved methods (Taylor and others 1997). Analysisof the lipid content of dairy products has also seen some advanc-es in the past year. Dioniosi and others (1999) compared super-critical fluid extraction to Röse-Gottlieb solvent extraction. Theirresearch demonstrated a similarity between the two extractionmethods while the supercritical fluid extraction method was fasterand free of organic solvents. Manganiello and others (2000) ap-plied the use of piezoelectric detection to supercritical fluid ex-traction. The use of an in-line piezoelectric detector is able tomeasure the change in weight of the sample during the extractionprocess. This allows for more accurate determination of the finalweight of the sample after all of the fat has been extracted (totalfat). In addition, it can allow for more rapid determination of thetotal fat by determining the point when the steady state mass hasbeen reached without having to re-extract the sample multipletimes to confirm that the steady state mass has been reached(Manganiello and others 2000).

Rapid Analysis for Pesticides in Foods: Pesticide residues are aconcern among consumers throughout the United States and oth-er countries. Currently the methods of analyzing food productsand other substances such as contaminated soil and water in-volve the use of organic solvents such as hexane and dichlo-romethane to extract the pesticides from the sample matrix. Oncethe pesticides have been extracted from the sample matrix, thesamples must be “cleaned” to remove any unwanted com-pounds, such as lipids, which may interfere GC analysis of thesample for any pesticides present. The most common method forcleaning is solid phase extraction (van der Hoff and van Zoonen1999). Supercritical fluid extraction provides an alternative to us-ing organic solvents for the extraction of pesticides from theirsample matrix. Some of the advantages which supercritical fluidextraction provides over the traditional methods of pesticide ex-traction are that the extraction can be performed in less time, andutilizes less solvent volume. In addition, supercritical fluid extrac-tion can be tailored to the solute of interest by changing the tem-perature and pressure of the extraction process. Supercritical fluidextraction can also be tailored for pesticides that contain morepolar groups by the addition of polar modifiers to the CO2 suchas methanol (Camel 1998). The use of supercritical CO2 for theextraction of pesticide residues has been reviewed extensively inother articles and so it will be only covered briefly in this article.Three reviews, which stand out in the recent years are: Lehotay(1997), Camel (1998), and van der Hoff and van Zoonen (1999).These articles cover the analysis of pesticides in food, water, soiland animal tissue in depth along with the benefits and drawbacksof supercritical fluid extraction in the analysis of pesticide resides.Since the release of the previously mentioned review articles,more contributions to the body of scientific knowledge have beenpublished. These articles range from the determination of fenpy-roximate in apples (Halvorsen and others 2000) to the extraction/analysis of atrazine and other triazine herbicides from eggs (Pens-abene 2000).

Solvents for Chromatography: Supercritical CO2 has been uti-lized as a mobile phase in supercritical fluid chromatographysince the early 1980s when it was developed for use as a replace-ment/ complement to gas chromatography (Poole 2000). Usingsupercritical fluids as a mobile phase for chromatography pro-vides some advantages over conventional GC or HPLC. The sol-vent power of the supercritical fluid can be manipulated bychanging the temperature and/ or the pressure (density) of the mo-bile phase. In the case of carbon dioxide, when it is at lower den-sities, it is similar to that of n-hexane and at higher densities it issimilar to that of dichloromethane (Brunner 1994). In fact, just asthe composition of the mobile phase can be varied during theseparation of compounds during HPLC, the density of the mobile

phase can be varied in supercritical fluid chromatography. Byvarying the density, the user is in fact varying the degree to whichthe mobile phase is a nonpolar solvent. A polar co-solvent canalso be added to the mobile phase which can allow for the sepa-ration of more polar compounds as compared to those which canbe separated by carbon dioxide alone (Brunner 1994).

A supercritical fluid chromatograph consists of the same basiccomponents as HPLC and GC. Both HPLC and supercritical fluidchromatography systems have a minimum of one pump with thepossibility to upgrade to a system that can handle gradients, an in-jection apparatus, a column for separation, a detector and possi-bly a part for collection of different analyte fractions (Figure 5). Thekey differences between the two systems are the fact that thepump on the supercritical fluid chromatography system on aver-age could handle increased pressures, and the column on the su-percritical fluid chromatography system has to be heated to ele-vate the temperature of the mobile phase above its critical point(Brunner 1994). Much like the similarities between supercriticalfluid chromatography and HPLC, supercritical fluid chromatogra-phy and GC also have many similarities. Both systems can utilizecapillary columns and FID detectors. In fact, this represents twodifferent approaches to supercritical fluid chromatography,packed column and capillary column. Packed column chroma-tography is similar to HPLC while capillary column is similar toGC. In packed column chromatography, it is usually necessary toutilize co-solvents to elute polar compounds from the column,whereas capillary column chromatography usually uses pureCO2. The reason for using pure CO2 is that most polar modifiersare not compatible with FID’s, eliminating the method of detection(Pyo 2000). In addition, packed column supercritical fluid chro-matography has advantages over tradition normal phase HPLC inthat it offers faster separations and column re-equilibration, andhigher column efficiencies. Packed column supercritical fluidchromatography also offers advantages over normal phase HPLCin that it has more variables which can be manipulated so that theanalysis can be better tailored to the analyte of interest (Poole2000).

Supercritical Fluids and Novel Methods of FoodProcessing

Supercritical fluids have been utilized in different novel meth-ods of food processing. Two of these new methods will be dis-cussed in this paper. These methods are the use of supercriticalCO2 to control puffing in extrusion, and the use of supercritical

Figure 5—Flow diagram of a supercritical fluid chromagraphysystem



CO2 to remove excess hexane from soybean oil produced byconventional extraction techniques.

Controlled Puffing in ExtrusionRizvi and Mulvaney (1992) patented a new method to produce

extruded products using supercritical CO2 to reduce the tempera-ture and shear needed for conventional thermoplastic extrusion.Currently, the high temperatures (130 to 170 °C) and shear pre-vents the use of thermally liable ingredients such as some flavors,colors and whey proteins (Alavi and others 1999). This method ofextrusion uses supercritical CO2 as a blowing agent to facilitatethe formation of the cellular structure in extrudates in place of theexpansion of water upon exit of the extruder barrel in convention-al extrusion. The use of supercritical fluids in the extrusion pro-cess is based on a four-step process described by Rizvi and others(1995). The steps in this process include: 1) development of adough with gas-holding properties by mixing alone; 2) injectionof supercritical CO2; 3) creation of a controlled thermodynamicinstability by manipulation of the pressure and/ or temperature inthe extruder; and, 4) control of the degree of cell growth duringthe setting of the product through appropriate die selection andpost-extrusion drying and cooling processes (Rizvi and others1995). The use of supercritical fluid extrusion was further studiedby Alavi and others (1999) and Gogoi and others (2000) whenthe use of whey protein concentrate and egg whites in productionof extruded products was studied. The results from the study byAlavi and others demonstrated that the extrudates produced bysupercritical fluid extrusion had a similar bulk density and expan-sion ratio to steam extrudates, while the products obtained fromsupercritical fluid extrusion had a unique composition and uni-form microcellular composition (Alavi and others 1999). Gogoiand others then determined that the addition of egg white to thefeed produced a softer skin and fragile, well formed cellular struc-ture (Gogoi and others 2000). This research can lead to the addi-tion of heat-sensitive flavorings to extruded products after theproduct has been heated or while the product is being expandedby the previously mentioned method.

Removal of Hexane from Soybean OilSupercritical CO2 has been utilized by Reverchon and others

(2000) to eliminate hexane from soybean oil during its prepara-tion for food use. The justification for this research is that hexaneelimination is the step that uses the largest amount of energy dur-ing the soybean oil extraction process. In addition to the costs as-sociated with hexane elimination, tradition methods can leave ahexane residue of up to 1000 ppm. Reverchon and others (2000)developed a method to eliminate hexane from soybean oil bypassing it countercurrent to supercritical CO2 through a packedtower. These experiments were performed with soybean oil con-taining 10% hexane to simulate the soybean oil/ hexane mixturefound after the second stage of traditional hexane elimination. Itwas found that the best results for this experiment were obtainedat a CO2 density of 716 kg m-3. At this density the hexane residueleft in the soybean oil was only 20 ppm (Reverchon and others2000). This publication also raises some questions, which couldbe addressed in future research. The authors determined therange of temperature and pressures to begin the extraction pro-cess using binary phase diagrams for the solubility of hexane insupercritical CO2 and soybean oil in supercritical CO2, but not asa ternary system taking the interaction of supercritical CO2, hex-ane and lipids into account. The hexane could act as a nonpolarco-solvent with the CO2 to increase the solubility of some of theshorter chain fatty acids present in the soybean oil. This couldcause changes in the fatty acid composition of the soybean oil,and thus alter its nutritional value or its cooking characteristics.

ConclusionsBased on the information presented in this paper, it can be seen

that supercritical fluids have been used for developing an ever-ex-panding niche in the food industry. Whether it is used as a solventfor extraction in analytical methods such as gravimetric determi-nation of fat content or in large-scale extractions such as decaf-feinating coffee, supercritical CO2 has proven its usefulness as areplacement for organic solvents. With increasing concerns aboutthe use of organic solvents and their disposal, supercritical fluidextraction is gaining in popularity faster than ever before. The fu-ture looks promising for the use of supercritical fluids, with newmethods of extraction constantly being developed, as with othernovel uses for the food processing industry.

Primary References for Supercritical Fluid ExtractionAllada SR. 1984. Solubility Parameters of Supercritical Fluids. Ind J Chem Process

Development 23:344-348.Brunner G. 1994. Gas Extraction, An Introduction to Fundamentals of Supercritical

Fluids and the Application to the Separation Processes. Springer, New York, NY.Dionisi F, Hug B, Aeschlimann JM, Houllemar A. 1999. Supercritical CO2 extraction

for total fat analysis of food products. 1999. J Food Sci 64(4):612-615.Kiszka MB, Meilchen MA, McHugh MA. 1988. Modeling High-Pressure Gas-Poly-

mer Mixtures Using the Sanchez-Lacombe Equation of State. J Applied PolymerSci 36:583-597.

Lehotay SJ. 1997. Supercritical fluid extraction of pesticidies in foods. J Chroma-toraphy A 785:289-312.

McHugh M, Krukonis V. 1994. Supercritical Fluid Extraction, Second Edition. But-terworth-Heinemann, Boston.

Reverchon E, Della Porta G. 1995. Supercritical CO2 Extraction and Fractionationof Lavender Essential Oil and Waxes. J Agri and Food Chem 43:1654-1658.

Rizvi SSH, Mulvaney SJ. 1992. Extrusion processing with supercritical fluids. U.S.Patent 5120559.

Rizvi SSH, Yu ZR, Bhaskar AR, Chidambara Raj CB. 1994. Fundamentals of Processingwith Supercritical Fluids. Ch 1 in Supercritical Fluid Processing of Food and Bio-materials. Rizvi, S.S.H. p. 1-26. Bishopbriggs, Glasgow: Chapman & Hall.

Sovova H. 1994. Rate of the vegetable oil extraction with supercritical CO2- I.Modeling of extraction curves. Chem Eng Sci 49(3):409-414.

Valcarcel M, Tena MT. 1997. Applications of supercritical fluid extraction in foodanalysis. Fresenius J Anal Chem 358:561-573.

ReferencesAlavi SH, Gogoi BK, Khan M, Bowman BJ, Rizvi SSH 1999. Structural properties of

protein-stabilized starch-based supercritical fluid extrudates. Food Res Int32:107-118.

Aleksovski S, Sovova H, Poposka FA, Kulevanova S, Ristic M. 1999. Comparisonof essential oils obtained from Mentha piperita L. using supercritical carbon di-oxide extraction and hydrodistillation. Acta Pharm 49:51-57.

Alexander WS, Brusewitz GH, Maness NO. 1997. Pecan oil recovery and compo-sition as affected by temperature, pressure and supercritical CO2 flow rate. JFood Sci 62(4):762-766.

Allada SR. 1984. Solubility Parameters of Supercritical Fluids. Ind J Chem ProcessDevelopment 23:344-348.

Ammann A, Hinz DC, Addleman RS, Wai CM, Wenclawiak BW. 1999. Superheatedwater extraction, steam distillation and SFE of peppermint oil. Fresenius’ J AnalChem 364:650-653.

Anderson SG, Nair MG, Chandra A, Morrison E. 1997. Supercritical Fluid CarbonDioxide Extraction of Annatto Seeds and Quantification of trans-Bixin by HighPressure Liquid Chromatography. Phytochemical Anal 8:247-249.

Andersson MBO, Demirbuker M, Blomberg LG. 1997. J Chromatography A 785:337-343.

Anklam E, Berg H, Mathiasson L, Sharman M, Ulberth F. 1998. Supercritical fluidextraction (SFE) in food analysis: a review. Food Additives and Contaminants15(6):729-750.

Baysal T, Starmans DAJ. 1999. Supercritical carbon dioxide extraction of carvoneand limonene from caraway seed. J Supercritical Fluids 14:225-234.

Bauman D, Hadolin M, Rizner-Hras A, Knez Z. 1999. Supercritical Fluid Extractionof Rosemary and Sage Antioxidants. Acta Alimentaria 28(1):15-28.

Berg H, Magard M, Johansson G, Mathiasson L. 1997. Development of a supercrit-ical fluid extraction method for determination of lipid classes and total fat inmeats and its comparison with conventional methods. J Chromatography A785:345-352.

Berg, H, Turner C, Dahlberg L, Mathiassson L. 2000. Determination of food constit-uents based on SFE: applications to vitamins A and E in meat and milk. J Biochem-ical and Biophysical Methods 43(1-3):391-401.

Bhaskar AR, Rizvi SSH, Bertoli C, Fay LB, Hug B. 1998. A comparison of physicaland chemical properties of milk fat fractions obtained by two processing technol-ogies. J Am Oil Chemists Soc 75(10):1249-1264.

Brachet A, Mateus L, Cherkaoui S, Christen P, Gauvrit JY, Lanteri P, Veuthey JL.1999. Application of central composite designs in the supercritical fluid extrac-tion of tropane alkaloids in plant extracts. Analusis 27:772-778.

Bruhl L, Matthaus B. 1999. Extraction of oilseeds by SFE- a comparison with other



methods for the determination of the oil content. Fresenius’ J Anal Chem364:631-634.

Brunner G. 1994. Gas Extraction, An Introduction to Fundamentals of SupercriticalFluids and the Application to the Separation Processes. New York, NY: Springer.

Camel V. 1998. Supercritical fluid extraction as a useful method for pesticidesdetermination. Analusis 26(6):99-111.

Certik M, Horenitzky R. 1999. Supercritical CO2 extraction of fungal oil contain-ing g-linolenic acid. Biotech Techniques 13(11):11-15.

Chandra A, Nair MG. 1997. Supercritical Fluid Carbon Dioxide Extraction of a- andb-Carotene from Carrot (Daucus carota L.). Phytochemical Anal 8:244-246.

Cheung PCK, Leung AYH, Ang PO. 1998. Comparison of supercritical carbon dioxideand Soxhlet extraction of lipids from a brown seaweed, Sargassum hemiphyllum(Turn.) C. J Agri and Food Chem 46:4228-4232.

Chuang JC, Pollard MA, Misita M, Van Emon JM. 1999. Evaluation of analyticalmethods for determining pesticides in baby food. Analytica Chimica Acta399:135-142.

Coelho LAF, Oliveira JV, d’Avilia SG, Vilegas JHY, Lancas FM. 1997. SFE of Rose-mary Oil: Assessment of the Influence of Process Variables and Extract Charac-terization. J High Resolution Chromatography 20:431-436.

Dauksas E, Venskutonis PR, Sivik B. 1998. Extraction of lovage (Levisticum offici-nale Koch.) roots by carbon dioxide. 1. Effect of CO2 parameters on the yield ofthe extract. J Agri and Food Chem 46:4347-4351.

de Franca LF, Reber G, Meireles MAA, Machado NT, Brunner G. 1999. Supercriti-cal extraction of carotenoids and lipids from buriti (Mauritia flexuosa), a fruitfrom the Amazon region. J Supercritical Fluids 14:247-256.

Della PG, Taddeo R, D’ Urso E, Reverchon E. 1998. Isolation of clove bud and staranise essential oil by supercritical C02 extraction. Lebens Wissen and Technol.31:454-460.

Dhalewadikar SV, Seckner AJ, McMugh MA, Guckes TL. 1987. Separation of dode-cane biphenyl mixtures using supercritical ethane, carbon dioxide and ammonia.Ind Eng Chem Res. 26:976-982.

Dionisi F, Hug B, Aeschlimann JM, Houllemar A. 1999. Supercritical CO2 extractionfor total fat analysis of food products. 1999. J Food Sci 64(4):612-615.

Ferreira SRS, Nikolov ZL, Doraiswamy LK, Meireles MAA, Petenate AJ. 1999. Su-percritical fluid extraction of black pepper (Piper nigrum L.) essential oil. J Su-percritical Fluids 14:235-245.

Gabaldon JA, Maquieria A, Puchades R. 1999. Current trends in immunoassay-basedkits for pesticide analysis. Critical Reviews in Food Sci and Nutrition 39(6):519-538.

Gogoi BK, Alavi SH, Rizvi SSH. 2000. Mechanical properties of protein-stabilizedstarch-based supercritical fluid extrudates. Int J Food Properties 3(1):37-58.

Halvorsen BL, Thomsen C, Greibrokk T, Lundanes E. 2000. Determination of fenpy-roximate in apples by supercritical fluid extraction and packed capillary liquidchromatography with UV detection. J Chromatography 880(1-2):121-128.

Hopper ML. 1999 Automated one-step supercritical fluid extraction and clean-upsystem for the analysis of pesticide residues in fatty matrices. J Chromatography840(1):93-105.

Hougen OA, Watson KM. 1947. Chemical Process Principles, Part Two, Thermody-namics. John Wiley and Sons, INC., New York.

Ibanez E, Oca A, de Murga G, Lopez-Sebastion S, Tabera J, Reglero G. 1999. Super-critical Fluid Extraction and Fractionation of Different Preprocessed RosemaryPlants. J Agri and Food Chem 47:1400-1404.

Ibanez E, Palacios J, Senorans FJ, Santa-Maria G, Tabera J, Reglero G. 2000. Isola-tion and separation of tocopherols from olive by-products with supercritical flu-ids. J Am Oil Chem Soc 77:187-190.

Illes V, Daood HD, Biacs PA, Gnayfeed MH, Meszaros B. 1999. Supercritical CO2and Subcritical Propane Extraction of Spice Red Pepper Oil with Special Regardto Carotenoid and Tocopherol Content. J Chromatographic Sci 37:345-352.

Illes V, Daood HG, Perneczki S, Szokonya L, Then M. 2000. Extraction of corianderseed oil by CO2 and propane at super- and subcritical conditions. J SupercriticalFluids 17(2):177-186.

Jaren-Galan M, Nienaber U, Schwartz SJ. 1999. Paprika (Capsicum annuum) Ole-oresin Extraction with Supercritical Carbon Dioxide. J Agri and Food Chem47:3558-3564.

Jaremo M, Bjorklund E, Mathiasson L, Karlsson L, Torstensson A, Torkelson P. 1998.Supercritical Fluid Extraction of Clevidipine from a water based vegetable oilemulsion. J Liquid Chromatography and Related Technologies, 21(3):391-406.

King JW, Cygnarowicz PM, Favati F. 1997. Supercritical fluid extraction of eveningprimrose oil kinetic and mass transfer effects. Italian J Food Sci 9(3):193-204.

King JW, Eller FJ, Snyder JM, Johnson JH, McKeith FK, Stites CR. 1996. Extractionof fat from ground beef for nutrient analysis using analytical supercritical fluidextraction. J Agri and Food Chem 44:2700-2704.

Kiszka MB, Meilchen MA, McHugh MA. 1988. Modeling High-Pressure Gas-Poly-mer Mixtures Using the Sanchez-Lacombe Equation of State. J Applied PolymerSci 36:583-597.

Kuk MS, Dowd MK. 1998. Supercritical CO2 extraction of rice bran. J Am Oil ChemSoc 75(5):623-628.

Lancas FM, Rissaato SR, Galhiane MS. 1999. Determination of 2,4-D and dicambain food crops by MEKC. Chromatographia 50(1-2):35-40.

Le Floch F, Tena MT, Rios A, Valcarcel M. 1998. Supercritical fluid extraction ofphenol compounds from olive leaves. Talanta Int J of Pure and Appl Anal Chem46:1123-1130.

Lehotay SJ. 1997. Supercritical fluid extraction of pesticidies in foods. J Chroma-tography A 785:289-312.

Li M, Bellmer DD, Brusewitz GH. 1999. Pecan kernel breakage and oil extractedby supercritical CO2 as affected by moisture content. J Food Sci 64(6):1084-1088.

Lin TY, Wang YJ, Lai PY, Lee FJ, Cheng JT-S. 1999. Cholesterol content of fried-shredded pork extracted by supercritical carbon dioxide. Food Chem 67:89-92.

Lopez-Sebastian S, Ramoas E, Ibanez E, Bueno JM, Ballester L, Reglero G. 1998.Dearomatization of antioxidant rosemary extracts by treatment with supercriticalcarbon dioxide. J Agri and Food Chem 46:13-19.

Manganiello L, Rios A, Valcarcel M. 2000. Automatic microgravimetric determina-tion of fats in milk products by use of supercritical fluid extraction with on-linepiezoelectric detection. J Chromatography A 874:265-274.

Manninen P, Kallio H. 1997. Supercritical fluid chromatography-gas chromatogra-phy of volatiles in cloudberry (Rubus chamaemorus) oil extracted with supercrit-ical carbon dioxide. J Chromatography 787:276-282.

Manninen P, Laakso P. 1997a. Capillary supercritical fluid chromatography-atmo-spheric pressure chemical ionization mass spectrometry of triacylglycerols inberry oils. J Am Oil Chemists Soc 74:1089-1098.

Manninen P, Laakso P. 1997b. Capillary supercritical fluid chromatography-atmo-spheric pressure chemical ionization mass spectrometry of gamma- and alpha-linolenic acid containing triacylglycerols in berry oils. Lipids 32:825-831.

Manninen P, Pakarinen J, Kallio H. 1997. Large-scale supercritical carbon dioxideextraction and supercritical carbon dioxide countercurrent extraction of cloud-berry seed oil. J Agri and Food Chem 45:2533-2538.

McHugh M, Krukonis V. 1994. Supercritical Fluid Extraction, Second Edition. But-terworth-Heinemann, Boston.

Medvedovici A, David F, David V, Sandra P. 2000. Analysis of xanthines in bever-ages using a fully automated SPE-SFC-DAD hyphenated system. Annali di Chim-ica 90(7-8):455-465.

Mira B, Blasco M, Subirats S, Berna A. 1996. Supercritical CO2 extraction of essen-tial oils from orange peel. J Supercritical Fluids 9 (4) 238-243.

Mohamed RS, Neves GBM, Kieckbusch TG. 1998. Reduction in cholesterol and frac-tionation of butter oil using supercritical CO2 with adsorption on alumina. Int JFood Sci and Technol 33:445-454.

Moraes MLL, Vilegas JHY, Lancas FM. 1997. Supercritical Fluid Extraction of Gly-cosylated Flavonoids from Passiflora leaves. Phytochemical Anal 8:257-260.

Motohashi N, Nagashima H, Parkanyi C. 2000. Supercritical fluid extraction for theanalysis of pesticide residues in miscellaneous samples. J Biochemical and Bio-physical Methods 43:313-328.

Page SH, Yun H, Lee ML, Gaotes SL. 1993. Rapid Method for the Determination ofPhase Behavior of Fluid Mixtures Employed in Supercritical Fluid Experiments.Anal Chem 65:1493-1495.

Page SH, Morrison JF, Christensen RG, Choquette SJ. 1994. Instrument for EvaluatingPhase Behavior of Mixtures for Supercritical Fluid Experiments. Anal Chem66:3553-3557.

Palazoglu TK, Balaban MO. 1998. Supercritical CO2 extraction of lipids from roast-ed pistachio nuts. Transactions of the ASAE 41(3):679-684.

Palma M, Taylor LT. 1999. Extraction of polyphenolic compounds from grape seedswith near critical carbon dioxide. J Chromatography A. 16:117-124.

Palma M, Taylor LT, Varela RM, Cutler SJ, Cutler HG. 1999. Fractional extraction ofcompounds from grape seeds by supercritical fluid extraction and analysis forantimicrobial and agrochemical activities. J Agri and Food Chem 47:5044-5048.

Palma M, Taylor LT, Zoecklein BW, Douglas LS. 2000. Supercritical fluid extractionof grape glycosides. J Agri and Food Chem 48:775-779.

Pensabene JW, Fiddler W, Donoghue DJ. 2000. Supercritical fluid extraction ofatrazine and other triazine herbicides from fortified and incurred eggs. J Agri andFood Chem 48(5):1668-1672.

Pino JA, Garcia J, Martinez MA. 1999. Comparison of solvent extract and supercrit-ical carbon dioxide extract of spearmint leaf. J Essential Oil Res 11:191-193.

Poiana M, Sicari V, Mincione B. 1998. Supercritical carbon dioxide (SC-CO2) ex-traction of grapefruit flavedo. Flavour-and-Fragrance-Journal 13:125-130.

Poole CF. 2000. Progress in packed column supercritical fluid chromatography:materials and methods. J Biochemical and Biophysical Methods 43:3-23.

Porta GD, Taddeo R, D’Urso E, Reverchon E. 1998. Isolation of Clove Bud and StarAnise Essential Oil by Supercritical CO2 Extraction. Lebensmittel-Wissenschaft-Technologie 31(5):454-460.

Perrut M, Clavier JY, Poletto M, Reverchon E. 1997. Mathmatical modeling of sun-flower seed extraction by supercritical CO2. Ind and Eng Chem Res 36 (2):430-435.

Pyo D. 2000. Separation of vitamins by supercritical fluid chromatography withwater-modified carbon dioxide as the mobile phase. J Biochemical and Biophys-ical Methods 43:113-123.

Ramos L, Hernandez LM, Gonzalez MJ. 2000. Study of the distribution of the poly-chlorinated biphenyls in the milk fat globule by supercritical fluid extraction.Chemosphere 41:881-888.

Reverchon E, Della Porta G. 1995. Supercritical CO2 Extraction and Fractionationof Lavender Essential Oil and Waxes. J Agri and Food Chem 43:1654-1658.

Reverchon E, Poletto M, Sesto Osseo L, Somma M. 2000. Hexane elimination fromsoybean oil by continuous packed tower processing with supercritical CO2. J AmOil Chemists’ Soc 77(1):9-14.

Rezaei K, Temilli F. 2000. Lipase-catalyzed hydrolysis of canola oil in supercriti-cal carbon dioxide. J Am Oil Chemists Soc 77(8):903-909.

Rizvi SSH, Mulvaney SJ. 1992. Extrusion processing with supercritical fluids. USPatent 5120559.

Rizvi SSH, Mulvaney SJ, Sokhey AS. 1995. The combined application of supercrit-ical fluid and extrusion technology. Trends in Food Sci and Technology 6:232-240.

Rizvi SSH, Yu ZR, Bhaskar AR, Chidambara Raj CB. 1994. Fundamentals of Processingwith Supercritical Fluids. Ch 1 in Supercritical Fluid Processing of Food and Bio-materials. Rizvi, S.S.H. p. 1-26. Chapman & Hall, Bishopbriggs, Glasgow.

Ronyai E, Simandi B, Lemberkovics E, VeressT, Patiaka D. 1999. Comparison of thevolatile composition of clary sage oil obtained by hydrodistillation and supercrit-ical fluid extraction. J Essential Oil Res 11:69-71.

Sass-Kiss A, Czukor B, Gao Y, Stefanovits P, Boross F. 1998. Supercritical carbondioxide extraction of onion oleoresin. J Sci of Food and Agriculture 76:189-194.

Sass-Kiss A, Simandi B, Gao Y, Boross F, Vamos FZ. 1998a. Study on the pilot-scaleextraction of onion oleoresin using supercritical CO2. J Sci of Food and Agricul-ture 76:320-326.

Scalia S, Giuffreda L, Pallado P. 1999. Analytical and preparative supercriticalfluid extraction of Chamomile flowers and its comparison with conventionalmethods. J Pharmaceutical and Biomedica Anal 21:549-558.



Senorans FJ, Ibanez E, Cavero S, Tabera J, Reglero G. 2000. Liquid chromatograph-ic-mass spectrometric analysis of supercritical-fluid extracts of rosemary plants.J Chromatography 870:491-499.

Shen Z, Palmer MV, Ting SST, Fairclough RJ. 1997. Pilot scale extraction and frac-tionation of rice bran oil with dense carbon dioxide. J Agri and Food Chem45:4540-4544.

Shen Z, Palmer MV, Ting SST, Fairclough RJ. 1996. Pilot scale extraction of ricebran oil with dense carbon dioxide. J Agri and Food Chem 44:3033-3039.

Shukla A, Bhaskar AR, Rizvi SSH, Mulvaney SJ. 1994. Physicochemical and rheo-logical properties of butter made from supercritically fractionated milk-fat. JDairy Sci 77(1):45-54.

Simandi B, Deak A, Ronyai E, Yanxiang G, Veress T. 1999. Supercritical CarbonDioxide Extraction and Fractionation of Fennel Oil. J Agri and Food Chem47:1635-1640.

Simandi B, Oszagyan M, Lemberkovics E, Kery A, Kaszacs J, Thyrion F, Matyas T.1998. Supercritical carbon dioxide extraction and fractionation of oregano ole-oresin. Food Res Int 31(10):723-728.

Skerget M, Knez Z, Novak Z, Bauman D. 1998. Separation of Paprika ComponentsUsing Dense CO2. Acta Alimentaria 27(2):149-160.

Sovova H. 1994. Rate of the vegetable oil extraction with supercritical CO2- I.Modeling of extraction curves. Chem Eng Sci 49(3):409-414.

Smith JM, Van Ness HC, Abbott MM. 1996. Introduction to Chemical EngineeringThermodynamics, Fifth Edition. McGraw-Hill Companies, Inc., New York. P 179-213.

Taylor SL, Eller FJ, King JW. 1997. A comparison of oil and fat content in oilseedsand ground beef- using supercritical fluid extraction and related analytical tech-niques. Food Res Int 30 (5):365-370.

Taylor SL, King JW. 2000. Optimization of the extraction and fractionation of cornbran oil using analytical supercritical fluid chromatography. J ChromatographicSci 38:91-94.

Taylor SL, King JW, Montanari L, Fantozzi P, Blanco MA. 2000. Enrichment andfractionation of phospholipid concentrates by supercritical fluid extraction andchromatography. Italian J Food Sci 12(1):65-76.

Tena MT, Valcarcel M, Hidalgo PJ, Ubera JL. 1997. Supercritical fluid extractionof natural antioxidants from rosemary: comparison with liquid solvent sonication.Anal Chem 69:523-526.

Tipsrisukond N, Fernando LN, Clarke AD. 1998. Antioxidant effects of essential oiland oleoresin of black pepper from supercritical carbon dioxide extractions inground pork. J Agri and Food Chem 46:4329-4333.

Turner C, Mathiasson L. 2000. Determination of vitamins A and E in milk powderusing supercritical fluid extraction for sample clean-up. J Chromatography A874:275-283.

Valcarcel M, Tena MT. 1997. Applications of supercritical fluid extraction in foodanalysis. Fresenius J Anal Chem 358:561-573.

van der Hoff GR, van Zoonen P. 1999. Trace analysis of pesticides by gas chroma-tography. J Chromatography 843(1-2):301-322.

Vesper H. Nitz S. 1997. Composition of Extracts from Paprika (Capsicum Annum L.)Obtained by Conventional and Supercritical Fluid Extraction. Advances in FoodSci 19(5-6):172-177.

Vesper H, Nitz S. 1997b. Changes of SFE and hexane extracts from paprika (Cap-sicum annuum L.) during storage. Advances in Food Sci 19:178-183.

Walker TH, Cochran HD, Hulbert GJ. 1999. Supercritical carbon dioxide extractionof lipids from Pythium irregulare. J Am Oil Chemists Soc 76(5):595-602.

Wilkes JG, Conte ED, Kim Y, Holcomb M, Sutherland JB, Miller DW. 2000. Samplepreparation for the analysis of flavors and off-flavors in foods. J ChromatographyA 880:3-33.

Yu ZR, Rizvi SSH, Zollweg JA. 1992. Fluid liquid equilibria of anhydrous milk-fatwith supercritical carbon dioxide. J Supercritical Fliuids 5(2):123-129.

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super critical fluids and the food industry

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