WO2004082800A1

WO2004082800A1 - Process for reducing the concentration of undesired compounds in a composition

Info

Publication number: WO2004082800A1
Application number: PCT/GB2004/001113
Authority: WO
Inventors: Stuart Corr
Original assignee: Ineos Fluor Holdings Limited
Priority date: 2003-03-20
Filing date: 2004-03-16
Publication date: 2004-09-30
Also published as: GB0306399D0

Abstract

A process for treating a composition comprising one or more undesired coumarin and/or furocoumarin compounds and one or more desired compounds so as to reduce the concentration of the one or more undesired coumarin and/or furocoumarin compounds is described. The process comprises the steps of (1) contacting the composition with a solid adsorbent, (2) eluting the solid adsorbent on which the composition is retained with an extraction solvent comprising a (hydro)fluorocarbon, and (3) collecting a solvent eluate containing a composition having a reduced concentration of the undesired coumarin and/or furocoumarin compound(s) from the solid adsorbent. The process is particularly suited to the removal of bergapten from citrus oils, especially bergamot and lime oils. Also claimed are new bergamot and lime oils.

Description

PROCESS FOR REDUCING THE CONCENTRATION OF UNDESIRED COMPOUNDS IN A COMPOSITION

The present invention relates to a process for reducing the concentration of undesired coumarin and/or furocoumarin compounds in a composition comprising those compounds and one or more desired compounds. More particularly, the present invention relates to a process for reducing the concentration of undesired coumarin and/or furocoumarin compounds in flavour and/or fragrance compositions comprising those compounds and one or more desired flavour and/or fragrance compounds (hereinafter referred to collectively as organoleptic compounds). In particular, the present invention relates to a process for reducing the concentration of undesired coumarin and/or furocoumarin compounds in citrus oils.

Citrus oils are typically extracted, i.e. by steam distillation or with a polar solvent, or expressed from plant materials and are used for flavouring, fragrance and medicinal purposes. These oils typically contain quantities of undesirable compounds as well as the desired compounds.

One class of compounds that are found in citrus oils, such as bergamot oil and lime oil, are the coumarins and furocoumarins. Certain coumarins and furocoumarins can be tolerated in the sense that they have no significant toxicity or other undesirable properties and some even have desirable properties. However, a number of coumarins and furocoumarins have undesirable properties and these need to be removed from the oil altogether or at least reduced in concentration. In particular, a number of furocoumarins exhibit phototoxic, photocarcinogenic and/or photosensitising properties (see W. A. Saffran, Psoralen DNA Photobiology, Vol. II, CRC Press, Boca Raton, 73-86, 1988). One undesirable furocoumarin found in bergamot oil is bergapten (5- methoxy psoralen). This compound is phototoxic resulting in UV A- induced phototoxic effects when applied to the skin upon exposure to sunlight. In addition, on ingestion bergapten can result in photosensitisation and can have a toxic effect on the liver resulting in a range of side effects, including blurred vision, muscle cramps and involuntary muscle twitching (see J.

Finsterer, Lancet: 359, 1484, 2002).

Lime oil is used commonly in a variety of- flavour and fragrance applications, but the crude material that is expressed from lime peel contains relatively high levels of various phototoxic coumarins and furocoumarins, including bergapten.

Bergapten is also found in the lemon oil that is expressed from lemon peel.

The presence of significant levels of toxic coumarin and/or furocoumarin compounds in citrus oils limits their use in perfumery and cosmetic products as well as in food and beverage applications.

Traditionally, bergapten has been removed from citrus oils, such as bergamot oil, by treating the crude oil with an alkaline aqueous solution to chemically destroy the furocoumarin structure. This method, however, typically results also in the degradation of other hydrolytically sensitive materials, such as esters, that contribute to the organoleptic quality of the oil.

Bergapten has also been removed by distillation of the crude citrus oil to leave the bergapten as a component of a heavy distillate residue. However, thermally labile species in the citrus oil that contribute to the organoleptic quality of the oil tend to degrade during the distillation process. For example, the removal of the phototoxic coumarins and furocoumarins found in lime oil by steam distillation results in an oil of radically different character to that of the expressed raw material. Most notably, the levels of alpha-terpineol are dramatically increased and the citral content is decreased in the distilled oil as a result of degradation. The resulting oil has the flavour and fragrance characteristics associated with a lime cordial whilst the original raw material is lime-zesty and slightly lemony in character. For perfumery and aromatherapy applications, the expressed oil is preferred, but the levels to which it can be incorporated in the formulation are strictly limited by the phototoxic coumarins and furocoumarins it contains.

Thus, the traditional methods for removing the toxic coumarins and furocoumarins found in citrus oils tend to result in products of inferior organoleptic quality compared to the original oil.

Furthermore, the known techniques that are used to remove the phototoxic coumarins and/or furocoumarins, such as bergapten, found in citrus oils tend to result in the collective removal of all the coumarins/furocoumarins and, in particular, the simultaneous removal of bergamottin (5- geranoxypsoralen). Bergamottin has a number of desirable properties. For example, it is believed to be responsible for much of the "Grapefruit Effect", i.e. the observed beneficial increase in oral availability of several anti-cancer drugs that are normally metabolised by the cytochrome P450 3A4 (see K. He et al, Chem. Res. Toxicol., 11(4), - 252-9, 1998). Furthermore, bergamottin has also been shown to be a potent inhibitor of skin tumour initiation by benzo[a]pyrene and to block DNA adduct formation and tumour initiation by polycyclic aromatic hydrocarbons such as benzo[a]pyrene and 7,12-dimethylbenz[a]anthracene (see Y. Cai., Carcinogenesis, 18(8), 1521-7, 1997). Thus, it would be desirable if a process used to remove the toxic coumarin and/or furocoumarin compounds from citrus oils removed those compounds preferentially leaving a significant quantity of the organoleptic compounds, that endow the oil with the desired flavour and fragrance characteristics, behind. It would be even more desirable if those processes also left a substantial proportion of the bergamottin behind.

There is, therefore, a need for a process that is able to reduce the level of undesirable coumarin and/or furocoumarin compounds in flavour and/or fragrance compositions while retaining the organoleptic properties of those compositions. In particular, there is a need for a process that is able to reduce the level of toxic coumarins and/or furocoumarins in citrus oils, especially bergamot oil and lime oil, while retaining the organoleptic characteristics of the expressed oils. Such a process would preferably maintain desirable furocoumarins, such as bergamottin.

The present invention provides a new process for reducing the concentration of undesired coumarin and/or furocoumarin compounds in a composition, e.g. a flavour and/or fragrance composition, containing those compounds and one or more desired compounds. The process can reduce the level of toxic coumarins and/or furocoumarins in citrus oils, such as bergamot oil and lime oil, and yet retain the desirable organoleptic properties of those oils. The process is also capable of retaining much of the bergamottin content of the original oil.

According to the present invention there is provided a process for treating a composition comprising one or more undesired coumarin and/or furocoumarin compounds and one or more desired compounds so as to reduce the concentration of the one or more undesired coumarin and or furocoumarin compounds, which process comprises the steps of (1) contacting the composition with a solid adsorbent, (2) eluting the solid adsorbent on which the composition is retained with an extraction solvent comprising a (hydro)fluorocarbon, and (3) collecting a solvent eluate containing a composition having a reduced concentration of the undesired coumarin and/or furocoumarin compound(s) from the solid adsorbent.

The undesired coumarin and/or furocoumarin compounds that are extracted in the process of the present invention are toxic for one reason or another. A particular example of a toxic furocoumarin that can be extracted using the process of the present invention is bergapten.

In a particular embodiment, the composition that is treated in the process of the present invention is a flavour and/or fragrance composition and more particularly is a citrus oil. Citrus oils that may be treated include lemon, lime, grapefruit and bergamot oils that have been expressed from the peels of the corresponding fruits by pressing. The citrus oil may be an unrefined material that is the direct product of extracting the plant material containing the oil. Alternatively, the citrus oil obtained from the plant material may be subjected to one or more pre-treatment or refining steps before being subjected to the process of the present invention.

A particular embodiment of the present process involves the treatment of bergamot oil to reduce the concentration of and preferably remove altogether the bergapten it contains.

Accordingly, in a further aspect of the present invention there is provided a process for reducing the bergapten content of bergamot oil, which process comprises the steps of (1) contacting the bergamot oil with a solid adsorbent, (2) eluting the solid adsorbent on which the bergamot oil is retained with an extraction solvent comprising a (hydro)fluorocarbon, and (3) collecting a solvent eluate containing a bergamot oil of reduced bergapten content from the solid adsorbent.

The bergamot oil that is treated in the above process will typically have been extracted from the peel of the bergamot fruit. Such an oil will usually contain from 0.1 to 0.5 % by weight of bergapten. When this crude oil is treated in accordance with the process of the present invention, a refined bergamot oil having a significantly reduced concentration of bergapten that retains the organoleptic properties of the original or untreated oil can be obtained.

Accordingly, the present invention also provides a bergamot oil obtainable by the process of the present invention that contains less than 0.1 % by weight of bergapten, preferably less than 0.05 % by weight and more preferably less than 0.01 % by weight.

In a particular embodiment, the bergamot oil that is produced in the process also contains bergamottin at a concentration that is similar to the concentration in the original or untreated oil.

Accordingly, a further aspect of the present invention provides a bergamot oil comprising less than 0.1 % by weight of bergapten, preferably less than 0.05 % by weight and more preferably less than 0.01 % by weight, and from 0.5 to 6.0 % by weight of bergamottin, preferably from 1.0 to 5.0 % by weight and more preferably from 1.5 to 5 % by weight.

A further particular embodiment of the present process involves the treatment of lime oil to reduce the concentration of and preferably remove altogether the bergapten it contains. Accordingly, in a further aspect of the present invention there is provided a process for reducing the bergapten content of lime oil, which process comprises the steps of (1) contacting the lime oil with a solid adsorbent, (2) eluting the solid adsorbent on which the lime oil is retained with an extraction solvent comprising a (hydro)fluorocarbon, and (3) collecting a solvent eluate containing a lime oil of reduced bergapten content from the solid adsorbent.

The lime oil that is treated in the above process will typically have been extracted from the peel of the lime fruit. Such an oil will usually contain from 0.1 to 0.4 % by weight of bergapten. When this crude oil is treated in accordance with the process of the present invention, a refined lime oil having a significantly reduced concentration of bergapten that retains the organoleptic properties of the original or untreated oil can be obtained.

Accordingly, the present invention also provides a lime oil obtainable by the process of the present invention that contains less than 0.1 % by weight of bergapten, preferably less than 0.05 % by weight and more preferably less than 0.01 % by weight.

In a particular embodiment, the lime oil that is produced in the process also contains α-terpineol and citral (which is a combination of neral and geranial) at concentrations that are similar to the concentration in the original or untreated oil.

Accordingly, a further aspect of the present invention provides a lime oil comprising less than 0.1 % by weight of bergapten, preferably less than 0.05 % by weight and more preferably less than 0.01 % by weight; less than 1.0 % by weight of α-terpineol, e.g. from 0.01 to 0.9 % by weight, and from 1.0 to 6.0 % by weight of citral, e.g. from 2.0 to 6.0 % by weight.

In yet another particular embodiment, the lime oil that is produced in the process contains bergamottin at a concentration that is similar to the concentration in the original or untreated oil.

Accordingly, a further aspect of the present invention provides a lime oil comprising less than 0.1 % by weight of bergapten, preferably less than 0.05 % by weight and more preferably less than 0.01 % by weight and from 0.5 to 3.0 % by weight of bergamottin, preferably from 0.5 to 2.5 % by weight and more preferably from 1.0 to 2.5 % by weight.

A particularly preferred lime oil comprises bergapten, bergamottin, α- terpineol and citral at the levels indicated above.

The composition to be treated in the process of the present invention may be dissolved or dispersed in a solvent before it is brought into contact with the adsorbent in order to facilitate the adsorption. Any conventional solvent may be used for this purpose, particularly those materials which boil below 100°C. If the composition to be treated is dissolved or dispersed in a solvent before being contacted with the adsorbent, then it is preferably dissolved or dispersed in the same (hydro) fluorocarbon containing solvent that is to be used to elute the adsorbent.

The solid adsorbent is usually a polar material and is preferably in particulate form. Typically, the adsorbent will have a mean particle size between lOOμm and 10mm in diameter. Larger particles tend to be used with larger extractions. In general, the particulate adsorbent is packed in a vessel or column to form a bed to which the composition to be treated, optionally dissolved in a suitable solvent, and then the (hydro) fluoro carbon containing eluting solvent are conveyed.

The solvent entrains or dissolves the composition to be treated and carries it through the adsorbent bed packing the column or vessel. As the (hydro)fluorocarbon solvent passes through the adsorbent, the different affinities that the desired compounds have for the adsorbent compared to the undesired, toxic coumarin and/or furocoumarin compounds, such as bergapten, allows for at least partial separation of these compounds.

In practise, the one or more toxic coumarin and/or furocoumarin compounds tend to adsorb more strongly or even preferentially onto the adsorbent as a result of their strongly polar character. This stronger or preferential adsorption of the toxic coumarin/furocoumarin compounds will allow the desired compounds to be more readily removed from the adsorbent with the (hydro) fluorocarbon solvent. Thus, by monitoring the composition of the eluate that emerges from the column or vessel, it is possible to collect selectively the eluate that contains a composition, such as a citrus oil, that is refined in the sense of having a reduced amount of and preferably no toxic coumarin and/or furocoumarin compounds. The coumarin and/or furocoumarin compounds, such as bergapten, that are removed from the starting composition can be left behind on the adsorbent and discarded with the adsorbent. Alternatively, they may be eluted from the adsorbent following the collection of the refined composition.

Although the solvent may be allowed to pass passively through the adsorbent bed under the action of gravity, it is preferred to forcibly drive the solvent through the bed using a pump or some other means to create a positive (super-atmospheric) pressure at the inlet end of the column or vessel. The flow of solvent through the adsorbent bed is continued at least until the desired product has been eluted from the bed.

Suitable polar adsorbents for use in the present process include, inter alia, activated alumina, aluminium hydroxide, silica gel, silicic acid and cellulose. The preferred adsorbent will depend, inter alia, on the nature of the composition that is being processed. However, silica gels and silicic acid and basic or weakly acidic activated aluminas have been found to be particularly effective adsorbents when treating citrus oils. In order to minimise the possibility of undesirable isomerisation and hydrolytic processes, the activated and partially-deactivated silica gel and silicic acid adsorbents are particularly useful.

The solvent which is used in the process of the present invention contains at least one (hydro)fiuorocarbon. By the term "(hydro)fluorocarbon" we mean a compound selected from the group consisting of the hydrofluorocarbons and the perfluorocarbons. By the term "hydrofluorocarbon" we mean a compound which contains only carbon, hydrogen and fluorine atoms. Hydrofluorocarbon solvents are preferred.

The solvent is usually in the liquid state, although we do not discount the use of supercritical fluids. Where the solvent comprises one or more low boiling compounds which are gases at room temperature, the desired liquid state may be attained by cooling the solvent to a suitably low temperature or by subjecting it to super-atmospheric pressures at some point before it is contacted with the adsorbent.

Suitable perfluorocarbons include hexafluoroethane (R-116) and octafluoropropane (R-218). Suitable hydrofluorocarbons include the hydrofiuoromethanes, the hydrofluoroethanes and the hydrofluoropropanes, such as trifiuoromethane (R-23), fluoromethane (R-41), difluoromethane (R-32), pentafluoroethane (R-125), 1,1,1-trifluoroemane (R-143a), 1,1,2,2-tetrafluoroethane (R-134), 1,1,1,2-tetrafluoroethane (R-134a), 1,1-difluoroethane (R-152a), 1,1,1,3,3- pentafluoropropane (R-245fa), 1,1,2,2,3-pentafluoropropane (R-245ca), 1,1,1,2,3-pentafluoropropane (R-245eb), 1,1,2,3,3-pentafluoropropane (R- 245ea), 1,1, 1,2,3, 3 -hexafluoropropane (R-236ea), 1,1,1,2,2,3- hexafluoropropane (R-236cb), 1,1,1,3,3,3-hexafluoropropane (R-236fa), 1,1,1,2,3,3,3-heptafluoroρroρane (R-227ea) and 1,1,1,2,2,3,3- heptafluoropropane (R-227ca). Particularly preferred hydrofluorocarbons include R-134a, R-245fa, R-236ea and R-227ea, especially R-134a.

Solvents containing mixtures of two or more (hydro)fluorocarbons may be used if desired.

The extraction solvent which is used in the process of the present invention may also comprise a co-solvent in addition to the (hydro)fluorocarbon.

Suitable co- solvents include, inter alia, fluorine free and more particularly halogen free compounds. Suitable halogen free co-solvents will typically have a boiling point of 100°C or below, for example in the range of from -85 to 100°C. The preferred co-solvents have a boiling point of 80°C or below, for example in the range of from -85 to 80°C, preferably 20°C or below, for example in the range of from -70 to 20°C, and more preferably 10°C or below, for example in the range of from -60 to 10°C. Mixtures of two or more co-solvents may be used if desired. Suitable co-solvents may be selected from the C_.-₆, particularly the C₂-₄ hydrocarbon compounds by which we mean compounds containing only carbon and hydrogen atoms. Suitable hydrocarbons include the alkanes and cycloalkanes, with alkanes such as ethane, n-propane, i-propane, n-butane and i-butane being preferred.

Other suitable co-solvents include the hydrocarbon ethers, by which we

. 9 » 1 mean compounds having the formula R -O-R in which R and R are independently hydrocarbyl groups containing only carbon and hydrogen atoms, such as C .₆ and particularly -₃ alkyl groups. Suitable dialkyl ethers include dimethyl ether, methyl ethyl ether and diethyl ether.

Still further suitable co-solvents may be selected from the amides, sulphoxides, alcohols, ketones, carboxylic acids, carboxylic acid derivatives, inorganic acids and nitro compounds.

Suitable amide co-solvents include the N.N'-dialkylamides and alkylamides, e.g. dimethylformamide and formamide.

Suitable sulphoxide co-solvents include the dialkylsulphoxides, e.g. dimethylsulphoxide.

Suitable alcohol co-solvents include the aliphatic alcohols, particularly the alkanols. Suitable alkanols may be selected from the C , particularly the Cι_₃ alkanols such as methanol, ethanol, 1-propanol and 2-propanol .

Suitable ketone co-solvents include the aliphatic ketones, particularly the dialkyl ketones such as acetone.

Suitable carboxylic acid co-solvents include formic acid and acetic acid. Suitable carboxylic acid derivatives for use as co-solvents include the anhydrides, e.g. acetic anhydride, and the -₆, particularly the C_1-3 alkyl esters of Cι-₆, particularly Cμ₃ alkanoic acids, e.g. ethyl acetate.

Suitable nitro compounds for use as co-solvents include the nitroalkanes and nitroaryl compounds, e.g. nitromethane and nitrobenzene.

The extraction solvent typically comprises from 50.0 to 100 % by weight of a (hydro)fiuorocarbon and from 0 to 50 % by weight of a co-solvent. Preferred extraction solvents comprise from 70.0 to 100.0 % by weight of the (hydro)fluorocarbon and from 0 to 30 % by weight of the co-solvent. Particularly preferred extraction solvents comprise from 80.0 to 100.0 % by weight of the (hydro) fluorocarbon and from 0 to 20.0 % by weight of the co-solvent.

Typically, a co-solvent will not be used.

In common with conventional chromatography practice, the composition of the solvent can be varied during the course of a run to enhance the resolution of the separation.

If the co-solvent is a flammable material, which will be the case with the hydrocarbon, hydrocarbon ether and alkanol co-solvents identified above, then the extraction solvent will preferably comprise sufficient of a nonflammable (hydro)fluorocarbon to render the solvent non-flammable overall. Where the extraction solvent is a blend of one or more compounds, the resulting blend may be zeotropic, azeotropic or azeotrope-like. The preferred extraction solvents comprise only low boiling compounds so that removal of the solvent from the eluate containing the desired composition tends to be relatively facile and can be accomplished by flash evaporation or distillation at relatively low temperatures, e.g. room temperature and below. This, in turn, reduces the risk of loosing desired product either through co-evaporation of the more volatile compounds with the extraction solvent or thermal degradation of the more thermally unstable compounds.

The weight ratio of the composition to be treated to the adsorbent in the process of the present invention is typically in the range of from 1:10 to 10: 1, preferably in the range of from 1 :2 to 5:1. The optimum ratio depends, inter alia, on the nature of the composition to be treated. For citrus oils, such as bergamot oil, containing bergapten, the optimum ratio depends particularly on the proportion of oxygenated organoleptic species in the oil, with higher levels of these compounds demanding higher amounts of adsorbent. The person skilled in the art is readily able to determine a suitable amount of adsorbent based on the weight and make-up of the composition to be treated.

The process of the present invention is usually conducted at a temperature in the range of from -10 to 80°C. This includes the initial adsorption step, in which the composition to be treated is charged to the adsorbent, as well as the elution step with the (hydro)fluorocarbon containing solvent. Operating temperatures at or below ambient, e.g. in the range of from -10 to 30°C, are particularly preferred.

The process of the present invention may be conducted at atmospheric, sub- atmospheric or super-atmospheric pressures. The precise operating pressure will depend, inter alia, on the extraction solvent that is used, particularly its boiling point. Preferred operating pressures are in the range of from

0.1 to 200 bar, more preferably in the range of from 0.5 to 30 bar and particularly in the range of from 1 to 15 bar. When the adsorbent is packed into a column or vessel, the process is preferably operated at a pressure higher than that of the solvent bubble pressure to drive the solvent through the adsorbent in the liquid state.

The eluate containing the desired composition, such as a citrus peel oil having a reduced content of toxic coumarin and/or furocoumarin compounds, which is obtained in the process of the present invention is preferably subjected to a filtration step in order to separate it from any adsorbent which becomes entrained in the solvent. The extraction solvent may be removed from the desired composition by distillation or by flash evaporation.

The composition which is finally obtained from the process of the present invention may be used as it is or, alternatively, it may be subjected to one or more further processes, for example to purify the composition further or to isolate a given constituent or constituents contained in the composition.

It should also be appreciated that if a composition having a suitably low concentration of the toxic coumarin and/or furocoumarin compounds is not obtained after a single pass through the process of the present invention, then the treated composition obtained in the first pass may be subjected to one or more subsequent passes through the process in order to obtain a suitably low concentration of the toxic coumarin and/or furocoumarin compounds. Normally, however, by ensuring that a sufficient quantity of adsorbent is used and by careful monitoring of the eluate that emerges from the adsorbent bed, it is possible to obtain a refined composition having a suitably low concentration of the toxic compounds in a single pass through the process.

The apparatus which is used to carry out the process of the present invention may employ a solvent recovery system which removes the solvent from the eluate recovered from the adsorbent by evaporation and then condenses the resulting solvent vapour for reuse.

A suitable recovery system for low boiling point solvents, by which we mean solvents having a boiling point of 25°C or below, e.g. 0°C or below, comprises an evaporator into which the eluate emerging from the process is passed, a compressor for compressing the vapour generated in the evaporator and a condenser for cooling the compressed vapour emerging from the compressor. The solvent is removed from the eluate in the evaporator by flash evaporation induced by suction from the compressor and the solvent vapour so generated then passes to the compressor, which may be a diaphragm compressor, where it is compressed. From the compressor, the solvent vapour passes to the condenser where it is cooled and returned to liquid form for recharging to the process or possibly to a solvent reservoir supplying solvent to the process. The condenser, which may take the form of a coiled tube, can be arranged inside the evaporator so that the latent heat of condensation provides at least some of the energy required to evaporate the solvent.

A further suitable recovery system for low boiling point solvents comprises a solvent recycling circuit comprising an evaporator into which the eluate emerging from the process is passed and in which the solvent is evaporated and a condenser in which the vapour emerging from the evaporator is cooled and returned to liquid form for recharging to the process or possibly to a solvent reservoir supplying solvent to the process. Heating of the evaporator and cooling of the condenser may be carried out independently, but in a preferred embodiment an external heat pump system is used to both heat the evaporator and to cool the condenser. The external heat pump system comprises an evaporator, a compressor, a condenser and an expansion valve which are sequentially arranged in a circuit through which a heat transfer fluid is caused to flow. The evaporator of the external heat pump system, which may take the form of a coiled tube, is arranged inside or around the outside of the condenser of the solvent recycling circuit so that evaporation of the heat transfer fluid in the evaporator cools the condenser and provides for the condensation of the solvent vapour passing through the solvent recycling circuit. The vapour generated in the evaporator of the external heat pump system is then compressed and passes to the condenser where it condenses and gives off heat. The condenser of the external heat pump system, which may also take the form of a coiled tube, is arranged inside or around the outside of the evaporator of the solvent recycling circuit so that the latent heat of condensation associated with the condensation of the heat transfer fluid provides the heat required to evaporate the solvent passing through the solvent recycling circuit. The condensed heat transfer fluid is then returned through an expansion valve to the evaporator so completing the cycle in the external heat pump system.

As an alternative to an external heat pump system, an external circulating heat-transfer fluid may be used to transfer the heat of solvent condensation to the evaporator vessel to provide heat for solvent evaporation.

The process of the present invention may be operated in a batch or a continuous fashion.

The adsorbent which is used in the present invention may be washed following use with a powerful solvent such as ethanol in order to remove adsorbed organic species and then regenerated. A typical regeneration process involves drying the adsorbent at an elevated temperature under a stream of air or nitrogen, followed by any desired activity control treatment such as exposure to a controlled humidity environment. The adsorbent may also be treated with water prior to the drying process. Suitable drying temperatures are in the range of from 80°C to 600°C, more preferably from

100°C to 500°C and most preferably from 100°C to 200°C. Methods of adsorbent regeneration are well-known to those skilled in the art.

The present invention is now illustrated but not limited by the following examples.

Example 1

A glass pressure chromatography column was packed with 20 g of silica gel (Ineos Silicas Silicasorb AQ; 100 to 400 micron particle size). 40 g of Italian bergamot oil was charged to the top of the column and allowed to pass onto the adsorbent packing the column under the action of gravity.

R-13 a (Ineos Fluor Zephex grade) was then passed through the column under the action of gravity and the liquid R-134a containing the eluted oil was collected in fractions over a period of 20 minutes. The R-134a was allowed to evaporate from each collected fraction to leave a residue of extracted oil which was analysed by HPLC with UN detection to determine the bergapten content of the oil (see I. Bonaccorsi et al, Ital. J. Food Sci., 4(12), 485-491 (2000)).

The HPLC machine used was a Varian Prostar 320 UN- Vis detector with two Varian Prostar solvent delivery pumps. A Chromsep Omnisphere 5 Cι₈ column (250 mm x 4.6 mm) was used with a water-acetonitrile gradient elution program with detection at 315 nm. HPLC-grade solvents were used throughout and samples for analysis were dissolved at the 1 % level in acetonitrile and filtered prior to injection. The elution program started at

30:70 acetonitrile: water, followed by a hold for 1 minute, a linear gradient to 60:40 over a period of 4 minutes, a hold for 1 minute, a linear gradient to

78:22 over a period of 7 minutes and a linear gradient to 30:70 over a period of 5 minutes.

The process was continued until the oil residue contained a bergapten content, which was typically after recovery of at least 90% by weight of the original oil.

The essentially bergapten-free initial residues were combined to produce the desired product in a yield of greater than 90%. The combined product was analysed by Gas Chromato graph-Mass Spectroscopy (GC-MS) to quantify the major organoleptic species in comparison to the original oil.

The GC-MS machine used was a Varian 3900 GC with a Varian Saturn 2100T mass spectrometer with a method adapted from R P Adams (see "Identification of Essential Oil Components by Gas Chromatography/Quadrupole Mass Spectroscopy", Allured Publishing Corporation, 2001). The machine was equipped with a Chrompack CIP-SIL 8 CB column of 30 m length, 0.25 mm internal diameter and 0.25 micron film thickness. During the analysis, the column temperature was increased from 60°C to 240°C at a 3°C/min ramp and then held at 250°C for 10 minutes.

The results of the GC-MS analysis are shown in Table 1. Table 1

Example 2

Example 1 was repeated using 11 g of the silica gel and 21.3 g of Italian bergamot oil. Four residues that were essentially free of bergapten, weighing 16.1 g, 1.7 g, 0.4 g and 0.1 g respectively, were collected and combined. The bergapten content of the resulting product was then determined by HPLC using the method described in Example 1.

HPLC traces for both the original bergamot oil, the treated oil obtained by the process of the present invention and a commercially available furocoumarin free (FCF) bergamot oil are shown in Figure 1. It is evident from Figure 1 that the concentration of bergapten in the bergamot oil has been reduced dramatically.

The original oil contained approximately 2000 ppm of bergapten while the treated oil contained approximately 15 ppm of bergapten. Thus, the level of bergapten in the oil was reduced by a factor of approximately 140 times.

The original and treated oils were also analysed by GC-MS using the method described in Example 1. GC-MS traces for both the original bergamot oil and the treated oil are shown in Figure 2 from which it is evident that the treated oil retains significant quantities of the important organoleptic species.

Example 3

Example 1 was repeated using 60g of Italian bergamot oil and 20 g of silica gel (3: 1 ratio). Various residues were collected and analysed as before and those that contained low levels of bergapten were combined. The combined extract was analysed by HPLC using the method described in Example 1 and contained approximately 260 ppm of bergapten.

HPLC traces for both the original bergamot oil and the treated oil obtained by the process of the present invention are shown in Figure 3. The significant reduction in the bergapten content is evident.

Example 4

The method of claim 1 was used to treat 26.8 g of a Mexican expressed lime oil. The chromatography column contained 13.7 g of the silica gel.

Various residues were collected and analysed as before and those that contained low levels of bergapten were combined to give 22.7 g of product.

The combined extract was analysed by GC-MS using the method described in Example 1. The results of the GC-MS analysis are shown in Table 2 from which it is evident that the treated oil retains significant quantities of the important organoleptic species. The treated oil had a combined neral and geranial content (i.e. citral) content of 3.7 weight % which was unchanged from that of the original oil. The treated oil also retained the character of the original oil.

The original and treated oils were also analysed by HPLC using the method described in Example 1. The HPLC traces are shown in Figure 4. The significant reduction in the bergapten content is evident.

Table 2

It is clear from the Examples that products of the process of the present invention include greatly reduced levels of bergapten compared to the original oils. Additionally, the HPLC traces obtained in Examples 2 to 4 (see Figures 1, 3 and 4) show that the treated products can retain much of the bergamottin content of the original oil.

Claims

Claims:

1. A process for treating a composition comprising one or more undesired coumarin and/or furocoumarin compounds and one or more desired compounds so as to reduce the concentration of the one or more undesired coumarin and/or furocoumarin compounds, which process comprises the steps of (1) contacting the composition with a solid adsorbent, (2) eluting the solid adsorbent on which the composition is retained with an extraction solvent comprising a (hydro)fluorocarbon, and (3) collecting a solvent eluate containing a composition having a reduced concentration of the undesired coumarin and/or furocoumarin comρound(s) from the solid adsorbent.

2. A process as claimed in claim 1, wherein the composition to be treated is a flavour and/or fragrance composition.

3. A process as claimed in claim 2, wherein the flavour and/or fragrance composition is a citrus oil.

4. A process as claimed in claim 3, wherein the citrus oil is obtained from the peel of the citrus fruit by pressing.

5. A process as claimed in claim 3 or claim 4, wherein the citrus oil is selected from the group consisting of bergamot oil, lime oil, lemon oil and grapefruit oil.

6. A process as claimed in claim 5, wherein the citrus oil is bergamot oil.

7. A process as claimed in claim 5, wherein the citrus oil is lime oil.

8. A process as claimed in any one of the preceding claims, wherein the one or more undesired coumarin and/or furocoumarin compounds comprises bergapten.

9. A process as claimed in any one of the preceding claims, wherein the adsorbent is polar.

10. A process as claimed in any one of the preceding claims, wherein the adsorbent is in particulars form.

11. A process as claimed in any one of the preceding claims, wherein the adsorbent is packed in a column or vessel forming a bed to which the composition to be treated is charged.

12. A process as claimed in any one of the preceding claims, wherein the adsorbent is selected from the group consisting of activated alumina, aluminium hydroxide, silica gel, silicic acid and cellulose.

13. A process as claimed in claim 12, wherein the adsorbent is a silica gel or silicic acid.

14. A process as claimed in any one of the preceding claims, wherein the extraction solvent comprises at least one (hydro)fluorocarbon selected from the hydrofluoromethanes, the hydrofluoroethanes and the hydrofluoropropanes .

15. A process as claimed in claim 14, wherein the extraction solvent comprises at least one (hydro)fluorocarbon selected from the group consisting of frifluoromethane (R-23), fluoromethane (R-41), difluoromethane (R-32), pentafluoroethane (R-125), 1,1,1- trifluoroethane (R-143a), 1,1,2,2-tetrafluoroethane (R-134), 1, 1,1,2- tetrafluoroethane (R-134a), 1,1-difluoroethane (R-152a), 1,1, 1,3,3- pentafluoropropane (R-245fa), 1,1,2,2,3-pentafluoropropane (R-245ca), 1,1,1,2,3-pentafluoropropane (R-245eb), 1, 1,2,3, 3-pentafluoropropane (R-

245ea), 1,1,1,2,3,3-hexafluoropropane (R-236ea), 1,1,1,2,2,3- hexafluoropropane (R-236cb), 1,1,1,3,3,3-hexafluoroproρane (R-236fa),

1,1,1,2,3,3,3-heptafluoropropane (R-227ea) and 1,1,1,2,2,3,3- heptafluoropropane (R-227ca).

16. A process as claimed in claim 15, wherein the extraction solvent comprises at least one compound selected from 1 , 1 , 1 ,2-tetrafluoroethane (R-134a), 1,1, 1,3, 3-pentafluoropropane (R-245fa), 1,1,1,2,3,3- hexafluoropropane (R-236ea) and 1,1,1,2,3,3,3-heptafluoropropane (R- 227ea).

17. A process as claimed in claim 16, wherein the extraction solvent comprises 1,1,1,2-tetrafluoroethane (R-134a).

18. A process as claimed in any one of the preceding claims, wherein the extraction solvent comprises a co-solvent in addition to the (hydro)fluorocarbon.

19. A process as claimed in claim 18, wherein the co-solvent is halogen free.

20. A process as claimed in any one of the preceding claims, wherein the ratio of the composition to be treated to the adsorbent is in the range of from 1:10 to 10:1.

21. A process as claimed in claim 20, wherein the ratio of the composition to be treated to the adsorbent is in the range of from 1:2 to 5: 1.

22. A process as claimed in any one of the preceding claims which is conducted at a temperature in the range of from -10 to 80°C.

23. A process as claimed in any one of the preceding claims which is conducted at a pressure in the range of from 0.1 to 200 bar.

24. A process as claimed in any one of the preceding claims, wherein the solvent is in the liquid state.

25. A process for reducing the bergapten content of bergamot oil, which process comprises the steps of (1) contacting the bergamot oil with a solid adsorbent, (2) eluting the solid adsorbent on which the bergamot oil is retained with an extraction solvent comprising a (hydro)fluorocarbon, and (3) collecting a solvent eluate containing a bergamot oil of reduced bergapten content from the solid adsorbent.

26. A process for reducing the bergapten content of lime oil, which process comprises the steps of (1) contacting the lime oil with a solid adsorbent, (2) eluting the solid adsorbent on which the lime oil is retained with an extraction solvent comprising a (hydro)fiuorocarbon, and (3) collecting a solvent eluate containing a lime oil of reduced bergapten content from the solid adsorbent.

27. A bergamot oil obtainable by the process of the present invention that contains less than 0.1 % by weight of bergapten.

28. A bergamot oil comprising less than 0.1 % by weight of bergapten and from 0.5 to 6.0 % by weight of bergamottin.

29. A bergamot oil as claimed in claim 27 or claim 28 that contains less than 0.05 % by weight of bergapten.

30. A bergamot oil as claimed in claim 27 or claim 28 that contains less than 0.01 % by weight of bergapten.

31. A bergamot oil as claimed in claim 27 or claim 28 that is bergapten- free.

32. A lime oil obtainable by the process of the present invention that contains less than 0.1 % by weight of bergapten.

33. A lime oil comprising less than 0.1 % by weight of bergapten, less than 1.0 % by weight of α-tβrpineol and from 1.0 to 6.0 % by weight of citral.

34. A lime oil as claimed in claim 33 that additionally comprises from 0.5 to 3.0 % by weight of bergamottin.

35. A lime oil comprising less than 0.1 % by weight of bergapten and from 0.5 to 3.0 % by weight of bergamottin.

36. A lime oil as claimed in any one of claims 32 to 35 that contains less than 0.05 % by weight of bergapten.

37. A lime oil as claimed in any one of claims 32 to 35 that contains less than 0.01 % by weight of bergapten.

38. A lime oil as claimed in any one of claims 32 to 35 that is bergapten- free.