FR2590589A1 - New process for the photochemical conversion of hop extracts and device for implementing this process - Google Patents

Abstract

The present invention relates to a process for the photochemical conversion of hop extracts. The process is characterised in that the hop extracts, comprising the alpha and beta acids in solution in liquid or supercritical carbon dioxide, are subjected to a photochemical irradiation procedure under pressure in order to bring about the practically quantitative conversion of the alpha acids to iso- alpha acids. Application to beer manufacturing processes.

Description

 The present invention relates to a new process for the processing of hop extracts and to a new device for carrying out this process.

 Beer is, as we know, made from germinated barley or malt, water and hops. The resins contained in hop cones, or groups of flowers of female plants, give the beer its bitterness.

 This property of hops resins is mainly due to acids a (see Table I) and to a lesser extent to ss acids. During the manufacture of beer, the acids are isomerized into iso-a acids which are the most potent amerizing products. However, under conventional manufacturing conditions, the yield of this isomerization of the acids is less than 40%, which results in a significant loss of the bittering potential of the hops.

TABLE I

<tb><SEP> OH <SEP> O <SEP> OO
<tb><SEP> I <SEP> Cooking <SEP> In
<tb><SEP> R <SEP> of <SEP> soft <SEP> t <SEP> R
<tb> HO <SEP> O <SEP> HO
<tb><SEP> HO
<tb><SEP> a <<SEP> W
<Tb>
Acids with iso-a acids

<tb><SEP> OH <SEP> O <SEP> OH <SEP> O <SEP> OH <SEP> o
<tb><SEP> I <SEP> N <SEP> I
<tb> N <SEP> R
<tb><SEP> a <SEP> R <SEP> N <SEP> R <SEP> I
<tb><SEP> H <SEP> N0 <SEP> HO <SEP> H <SEP> Oxidation <SEP> HO <SEP> HO
<tb><SEP> N <SEP> N <SEP> h <SEP> I, <SEP> N
<Tb>
Acids, desoxy acids, acyl acids
For this reason, there are several patents concerning the chemical isomerization of α-acids to iso-α acids leading to transformations that are profitable in principle, but which can not be used for the moment, because they involve chemical reagents, which do not are not currently accepted by the
Fraud Control Services which control the food industries.

 This is the reason why a different method has been proposed that does not involve chemical reagent: it has indeed been possible to show that the bittering potential of hops can be particularly improved by means of photochemical processes (French Patent No. 19902) according to which the transformation is carried out in sunlight, which corresponds to conditions closer to natural conditions, under these conditions, however, it is essential to work with very dilute solutions (of the order of 10-2 - 10'3 mol / l) which can pose technical and economic problems if the separation of the photoproducts of the solvent is absolutely necessary.

 Table II which follows reminds the different forms of use of hops in breweries. If an absorption spectrum is realized after dissolution in the alcohol of these different presentations, it is found that the hop extracts resulting from extraction by liquid or supercritical fluid (essentially CO2) have an absorption spectrum which is substantially the sum of the absorption spectra of the acids a and ss acids. Indeed, natural dyes are well removed by this separation technique.

TABLE II
Different forms of use of hops in breweries

<tb><SEP>%<SEP> of use
<tb> Form <SEP> of <SEP> *
<tb><SEP> hops <SEP> worldwide <SEP> and <SEP> Benefits <SEP> Disadvantages
<tb><SEP> trend
<tb> Cones <SEP> 30 <SEP> Product <SEP> Natural <SEP> Low <SEP> Density. Costs
<tb><SEP> in <SEP> regression <SEP> Flavors <SEP> retained <SEP> of <SEP> transport <SEP> and <SEP> 0011 <SEP>
<tb><SEP> high <SEP> servation.
<Tb>

<SEP> Irregularity <SEP> of the <SEP> pro
<tb><SEP> duit. <SEP> Bad <SEP> con
<tb><SEP> servation.Performance
<tb><SEP> of <SEP> hopping <SEP> low
<tb> Powders <SEP> 40 <SEP> Best <SEP> Yield <SEP><SEP> Irregularity <SEP>
<tb> Granules <SEP> in <SEP> progress <SEP> of <SEP> hopping. <SEP> duit <SEP>. <SEP> Bad <SEP> con
<tb><SEP> Automation <SEP> of the <SEP> servation.
<Tb>

<SEP> hopping. <SEP> Rate <SEP> of <SEP> polyphenols
<tb><SEP> high.
<Tb>

<SEP> Extract from <SEP> 30 <SEP><SEP><SEP> Enhancement ren <SEP> Product <SEP> No <SEP> Natural. <September>
<Tb>

hops <SEP> stable <SEP>. <SEP> Better <SEP> Automation <SEP> of
<tb> isomerized <SEP> regularity <SEP> of bitter- <SEP> hopping <SEP> diffi
<tb> or <SEP> no <SEP> tume. <SEP> Content <SEP> in <SEP> cile. <SEP> Presence <SEP> of
<tb><SEP> polyphenols <SEP> plus <SEP> residue <SEP> of <SEP> solvent
<tb><SEP> low. <SEP> Better <SEP> of extraction.
<Tb>

<SEP> conservation. <September>
<Tb>

* The main French breweries use hops,
either in the form of powder and granules, or in the form
non-isomerized extracts.

 The conversion of α-acids to iso-α acids has been studied under different operating conditions and in various solvents. The conditions most suited to the reaction are summarized in Table III which follows.

iso-a
Solvant : éthanol
Température : 60 C
Rendement quantique : 0,03
Domaine spectral d'excitation : 460-300 nm
Rendement chimique : 95%
Si les acides ss ne contribuent que pour une part infime à l'amertume, il est possible de les transformer photochimiquement en acides desoxy- a (cf. tableau I) facilement oxydables en acides a (cf. tableau IV ci-dessous).TABLE III
Optimal conditions of reaction to

iso-alpha
Solvent: ethanol
Temperature: 60 C
Quantum yield: 0.03
Spectral domain of excitation: 460-300 nm
Chemical yield: 95%
If ss acids contribute only a small part of the bitterness, it is possible to transform them photochemically into desoxy-a acids (see Table I) that are easily oxidized into α-acids (see Table IV below).

desoxy- a
Solvant : éthanol, pH acide
Température : -
Solution dégazée : oui
Rendement quantique : 2.10-3
Domaine spectral d'excitation : 400-300 nm
Rendement chimique : 70%
Il est par ailleurs connu d'utiliser le pouvoir de dissolution du C02 liquide vis-à-vis de certaines molécules organiques dans le domaine de l'industrie agro-alimentaire et notamment d'utiliser le C02 comme agent d'extraction de certaines molécules organiques intéressantes, l'utilisation du
C02 présentant des avantages importants représentés notamment par son innocuité, par sa faible viscosité, par son inertie chimique, par sa transparence et par la possibilité qu'il offre de travailler à des températures auxquelles les artefacts d'origine thermique ne sont pas à craindre.TABLE IV
Optimum conditions of reaction ss

desoxy- a
Solvent: ethanol, acidic pH
Temperature : -
Solution degassed: yes
Quantum yield: 2.10-3
Spectral domain of excitation: 400-300 nm
Chemical yield: 70%
It is also known to use the dissolution power of liquid CO 2 with respect to certain organic molecules in the field of the food industry and in particular to use CO 2 as an agent for extracting certain organic molecules. interesting, the use of
C02 having significant advantages represented in particular by its safety, by its low viscosity, by its chemical inertness, by its transparency and by the possibility that it offers to work at temperatures at which artifacts of thermal origin are not to be feared.

 Among the industrial applications of direct interest to the agri-food industry is the extraction of the active ingredients of hops.

 Hops extracts, which are commonly used by the brewery industry, are a concentrated source of a (humulone family) generators, by isomerization, of bitter substances characteristic of beer bitterness. These extracts, generally obtained by extraction with dichloromethane, contain only a small proportion of the essential oils initially present in hops, because of the losses that occur during the evaporation of the solvents.

The first mention of the use of liquid CO2 for extracting the active ingredients of hops dates back to 1965 in a patent filed in the USSR. It is mentioned that α-acids have a high solubility (8 g / kg, 2.2.102 mol / kg) at 7 ° C and that this solubility decreases with increasing temperature. It was also patented in 1972 (BF HAG AG 2,140,096 and 2,140,097), but it was not until 1979 that it was started in Australia (Carlton and United Breweries Ltd,
Melbourne) the first global industrial unit capable of handling 2500 t / year (liquid CO2). Since then, other units have been set up in England for STEINER and, more recently, by SKW TROSTBERG AG in Germany, with a capacity of 5000 t / year (supercritical CO2).

 Table V below makes it possible to compare the composition of the extracts obtained by different processes.

TABLE V - EXTRACTION OF ACTIVE HOPPING PRINCIPLES

<tb><SEP> COMPOSITION <SEP> PELLETS <SEP> EXTRACTIONCO <SEP> EXTRACTION <SEP> EXTRACT
<tb><SEP> SUPERCRITICAL <SEP> CO2 <SEP> LIQUID <SEP> SOLVENT <SEP> ORG.
<Tb>

H20 <SEP> (%) <SEP> 6 <SEP> 1-7 <SEP> 0-2 <SEP> 8
<tb> Resins <SEP> Total <SEP> 30.3 <SEP> 77-98 <SEP> 80-98 <SEP> 88.5
<tb><SEP> (%)
<tb> acids <SEP> (%) <SEP> 12.6 <SEP> 27-41 <SEP> 35-55 <SEP> 39.5
<tb> acids <SEP> (%) <SEP> 14.0 <SEQ> 43-53 <SEP> 25-55 <SEP> 42.5
<tb> Resins <SEP> hard <SEP> 3.7 <SEP> 5-11 <SEP> 0 <SEP> 6.5
<tb> Tannins <SEP> (%) <SEP> / <SEP><SEP> 0.1-5 <SEP> 0 <SEP><SEP> / <SEP>
<tb> Oil <SEP> essential <SEP><SEP> 1-5 <SEP> 3-10 <SEP> I <SEP>
<tb> tielle <SEP>(%><SEP>
<tb> Fat <SEP> and <SEP> wax <SEP> / <SEP><SEP> 4-13 <SEP> 0-8 <SEP><SEP> / <SEP>
<tb><SEP> (%)
<Tb>
The extraction yields by liquid CO 3 seem to be able to be improved thanks to the use of a cosolvent (German Patent Application GRANT 3,219,414). The addition of 2% of ethanol makes it possible to pass the extraction yield. of acids from 87.3 to 96.6%.

It is an object of the present invention to provide a novel process and novel hop extract processing devices which better meet the requirements of the practice than the methods and devices provided in the prior art, particularly they avoid the use of chemical reagents and also avoid the many successive solubilization and separation processes required by the process which is the subject of the patent
No. 2,490,238, in that it comprises a reduced number of stages, in that the duration of the conversion reaction of α-acids to iso-α acids is much faster than in the processes known to date, so that the irradiation times are shorter than in the latter, and therefore less energy consuming than these.

The subject of the present invention is a process for the photochemical transformation of hop extracts obtained by treating hops with liquid or supercritical carbon dioxide, and more particularly by phototransformation of the acids a contained in said extracts, with iso-a acids, which process is characterized in that said extracts comprising the acids a and ss, in solution in liquid or supercritical carbon dioxide, are subjected to a photochemical irradiation process under pressure, to cause the practically quantitative conversion of α-acids to acids iso-alpha
According to a preferred embodiment of the process according to the present invention, the irradiation of the humulone is carried out in the presence of liquid or supercritical CO 2, in a range of useful wavelengths between 250 nm and 450 nm, at a pressure of between 50 and 300 bar and at a temperature of between 00C and 75 ° C.

 According to another preferred embodiment of the process according to the present invention, the irradiation of the extract solution is carried out by irradiation of at least one photon emitter taken from the group which comprises lasers, discharge, incandescent lamps, the sun.

 According to an advantageous arrangement of this embodiment, the radiation is emitted by a source of photons external to the reactor in which the photochemical transformation of α-acids into iso-α acids is carried out, and this radiation is emitted in a spectral range included between 250 and 450 nm.

 According to another advantageous arrangement of this embodiment, the radiation is emitted by a source of non-stigmatic photons disposed inside the reactor, in the solution to be irradiated.

 According to an advantageous embodiment of this arrangement, the radiations are in the wavelength range which goes from 350 to 450 nm and the radiations below 350 nm are eliminated using at least one optical filter.

 According to an advantageous arrangement of this embodiment, the radiation (s) providing the maximum reaction output (s) is (are) selected (s) by a selective optical filtering system.

 According to another advantageous arrangement of this embodiment, the wavelengths successively providing the maximum reaction yields as the reaction progresses, are selected by a selective optical filtering system depending on the the progress of the reaction.

 According to yet another advantageous arrangement of this embodiment, the selection of the radiation (s) providing the optimum reaction yield (s) is carried out using a fluorescent relay consisting essentially of a fluorescent liquid. interposed between the radiation source and the chamber in which the reaction takes place.

 According to another advantageous arrangement of this embodiment, the radiation source is doped with a metal halide to modify the spectrum of the light lines emitted by the source.

 According to another preferred embodiment of the process according to the present invention, the humulone subjected to the photochemical irradiation process is present at a concentration of between 10 × 10 -3 and 10 × 10 -2 molar / liter.

 According to yet another embodiment of the process according to the present invention, the iso-transformed acids are recovered by expansion at atmospheric pressure.

 According to another embodiment of the process according to the present invention, the photochemical transformation of the hop extracts is carried out while said extracts are in solution in carbon dioxide, in the presence of a small amount of ethanol.

 The present invention also relates to a device for implementing the hop extract processing method defined in the foregoing.

 According to the invention, this device is characterized in that it comprises, in combination, a reactor made of material resistant to the pressures and temperatures used in the process, which reactor comprises at least one irradiation window and is associated pressurizing means and at least one photon emitter.

 According to one embodiment of this device, the photon emitter is disposed outside the reactor.

 According to an advantageous arrangement of this embodiment, in the case where the dimension of the window is smaller than the reactor section, the latter is provided with a diffuser bar disposed substantially in the axis of the window, which allows ensure the irradiation of the inside of the reactor.

 According to another embodiment of the device according to the invention, the photon emitter is a non-stigmatic emitter which dives inside the solution of hop extracts in liquid or supercritical CO 2 possibly containing a small amount of a co-solvent such as ethanol, for example.

 According to an advantageous arrangement of this embodiment, the photon emitter is constituted by a discharge lamp made of filtering material.

 According to another advantageous arrangement of this embodiment, the photon emitter is constituted by a discharge lamp associated with an optical filter.

 According to another advantageous arrangement of this embodiment, the device according to the invention comprises a plurality of reactors and, consequently, lamps, mounted in series.

 According to yet another advantageous arrangement of this embodiment, the device according to the present invention comprises a single reactor coupled to a plurality of optical filters each of which absorbs a wavelength or an appropriate wavelength range which corresponds to a specific phase of the reaction.

 According to another advantageous arrangement of this embodiment, the device according to the present invention comprises a plurality of reactors each of which is coupled to an optical filter associated with a source of photons.

 According to an advantageous embodiment of the device according to the invention, the reactor has an annular shape in the center of which is mounted a source of photons.

 According to another advantageous embodiment of the device according to the invention, the latter comprises a reactor of substantially cylindrical shape, inside which is mounted axially a source of photons which is surrounded by a fluorescent relay constituted by a solution of a fluorescent substance that substantially fills the space between the reactor wall and the photon source lamp such as lamp in particular.

 In addition to the foregoing, the invention also comprises other provisions, which will emerge from the description which follows.

The invention will be better understood with the aid of the additional description which follows, which refers to the appended drawings in which
FIGS. 1 and 2 diagrammatically represent embodiments of devices according to the invention comprising a photon emitter outside the reactor,
the device of FIG. 1 comprising an irradiation window of dimensions greater than the useful section of the reactor and
the device of FIG. 2 comprising an irradiation window of dimensions smaller than the useful section of the reactor
FIGS. 3 and 4 schematically represent embodiments of devices according to the invention comprising an internal photon emitter,
FIG. 3 represents a single reactor and
Figure 4 shows a device comprising a plurality of reactors.

FIG. 5 is a schematic representation of a device comprising a cylindrical reactor with an internal photon source, equipped with a fluorescent relay
FIG. 6 is a schematic view in axial section of a reactor equipped with a plurality of optical filters
FIG. 7 is a diagrammatic view in axial section of a device comprising a plurality of reactors each of which comprises an internal photon source and an associated filter;
FIG. 8 is a diagrammatic view in axial section of an annular reactor in the central space of which a source of photons is mounted and
FIG. 9 is a schematic view in axial section of a closed tubular reactor with an external photon source.

 It should be understood, however, that these drawings and the corresponding descriptive parts are given solely by way of illustration of the object of the invention, of which they in no way constitute a limitation.

iSO-a par voie photochimique en présence de C02 liquide ou supercritique.According to the invention, the device represented in FIG. 1 comprises a high-pressure cell 1 (50 to 300 bar) with a sapphire window 2. The excitation light coming from an external photon source constituted either by a Xenon lamp or by a mercury vapor lamp, enters this cell 1 after filtering harmful radiation (at <330 nm) in a range of lengths between 360 and 450 nm. The analyzes carried out by absorption spectroscopy and by high performance liquid chromatography (HPLC) clearly show that it is possible to carry out the transformation at

iSO-a photochemically in the presence of liquid or supercritical CO 2.

 Since the absorption spectra of the various starting materials or photoproducts depend little on the nature of the solvent, the excitation wavelengths most suitable for the reaction are the same as those defined in an alcoholic medium (see the French patent). 2,490,238).

 In addition, the existence of a less viscous medium leads to a higher quantum yield, allowing a faster reaction, as explained below.

 It may be advantageous to add a small amount (of the order of 2%, for example) of a co-solvent such as ethanol, for example, to the solution in liquid or supercritical CO2.

 As a non-limiting example of the operation of the device of Figure 1, a given amount of humulone is placed in the high pressure cell 1 of useful internal volume 3 ml. The valve is then fixed on the reactor; it makes it possible to eliminate by vacuum pumping a large part of the air present in the reactor. The valve is then connected to a CO 2 cylinder at room temperature while the cell is held in melting ice. After 10 minutes, the cell is considered to be filled with liquid CO 2 and after 30 minutes the humulone has been completely dissolved and the mixture to be photolyzed is substantially homogeneous.

The experiment is carried out in a thermostated bath and the light excitation, coming from a lamp
OSRAM 500 W high-pressure type mercury vapor, is focused after filtering the 405 nm line on the photoreactor input window 2. Since this is particularly narrow, the reactor should be placed in perfectly reproducible spatial conditions (better than 1/2 mm). In the presence of light, a clear disappearance of humulone in solution in liquid CO 2 is demonstrated, the disappearance of which the kinetics is much greater than that obtained under the same conditions when the solvent is ethanol. It is the same for the appearance of iso-a acids (iso-humulone in this case).

 From the kinetics of appearance of the photoproduct or disappearance of the starting material, it is possible, knowing the light intensity absorbed in the reactor cell, to calculate the quantum yield of the phototransformation.

 When the irradiation is conducted between 360 and 450 nm, the phototransformation of α-acids to iso-α is practically quantitative. The reactor is a system capable of withstanding pressure and at a reasonable temperature of less than 80 ° C, at which temperature the thermal degradation of the extracts can begin to be observed.The reactor 1 of FIG. FIG 2 may advantageously be of tubular shape, it may operate either continuously or in "batch." If the window has a dimension equal to that of the useful section of the reactor, as in Figure 1, the entire reactor may be accessible Figure 1 shows, by way of example, the case of a piston reactor operating continuously, the reagents exit at 3 in the vicinity of the entrance face of the light because the absorption of light by the remaining acids have a maximum conversion thereof.

 On the other hand, if the flow is reversed with respect to the irradiation window, the large amounts present at the entrance will absorb the light, limiting the phototransformation in the deep zones.

 The flow rate of the reagents is adapted so that the transformation is carried out under optimal conditions.

 If the window 5 has a smaller dimension than the useful section of the reactor 4, as shown in FIG. 2, a better use thereof can be obtained by placing inside the latter a bar of glass or glass. slightly diffusing quartz 6, for irradiating all or part of the reactor 4.

 The length and shape of the diffusing bar 6 depend on the nature of the operation of the reactor: closed (see FIG. 2) where the bar 6 is substantially the length of the reactor or open, piston, where the bar has restricted dimensions corresponding simply to to an artificial increase of the entrance section of the light.

 The establishment of such a bar avoids the presence of dead volumes.

 The sources used under these conditions and with this type of reactor may be arbitrary: laser, sun, conventional photon sources provided that they are capable of emitting radiation in the right spectral range and that they are focusable. These stigmatism conditions are essential for the greatest amount of photons emitted to enter through window 2 or 5.

 In the particular case where a solar source is used, it is necessary to have a sun tracking system and a careful focus. This type of device is now classic. The system only works in direct sunlight.

The external photon source system described above in connection with FIGS. 1 and 2 requires the use of stigmatic sources. However, the industrial photon emitters which are constituted by discharge lamps in different gases, are by nature imperfectly stigmatic. It is indeed discharges in one or tubes: mercury lamps, doped mercury lamps, Xenon lamps with continuous spectrum, etc.
Under these conditions, with these lamps with good light output, it is almost impossible to focus their radiation on an inlet face of the reactor (see Figures 1 and 2). Thus, it is necessary to provide a system using one or more plunging lamps. To eliminate harmful radiation, the lamp can be made of a filter material or can have an optical filter eliminating radiation considered harmful.

 Such a device is shown in Figure 3. By its cylindrical nature, the photon emitter 7 can withstand very well the pressure stress due to the liquid or supercritical medium. The system can operate either continuously or in batch mode. This photon emitter 7 is mounted dipping in a reactor 8.

 Under particular conditions, it may be useful to have several lamps and several reactors for the transformation (FIG. 4). In fact, the harmful reactions correspond to the phototransformation of the iso-a acids.

 These reactions take place at wavelengths below about 370 nm. However, for a reactor or reactors operating continuously and whose nature is of the piston type, at the beginning of the injection, the medium does not contain iso-a acids and virtually all wavelengths can be used.

 However, as soon as a certain threshold of iso-a acids is obtained, they begin to absorb light and are likely to degrade. It is then necessary to have one or more reactors in which the harmful reactions are eliminated by elimination of the radiations which give them birth (cf figure 4). In this embodiment, the reactor 9 comprises an unfiltered inner lamp 10, while the reactors 11 and 13 comprise lamps 12 and 14, respectively, provided with optical filters which absorb the wavelengths suitable for degrading the iso-acids. -a trained.

 The embodiment shown diagrammatically in FIG. 7 is a reactor-change device of which each reactor 15, 16, 17 is equipped with a lamp 18, 19, 20, coupled to an absorbing optical filter respectively, for example, the lengths 313, 366 and 405 nm, thus ensuring continuous filtering, due to the passage of the solution to be treated from one reactor to another.

 In a variant, in the system represented in FIG. 6, one is in the presence of a single, stirred, closed reactor 21 equipped with a lamp 22 and in which the continuous filtering is ensured by a multiplicity of filters 23, 24, 25 coupled to the lamp 22.

 Among the filters which proved to be particularly suitable, it is necessary to mention the filters constituted by copper sulphate (CuSO4) in NH40H medium, by potassium dichromate (K2Cr207), by nickel sulphate (NiSO4), by sodium nitrite (NaNO2), by uranyl nitrate, present at appropriate concentrations (in g / l) and whose optical density is such that they can select the wavelengths which become harmful with respect to iso-α acids formed as the concentration of these is increased in the reactor.

 Fig. 5 shows an embodiment provided with a fluorescent relay. The reactor 26 of substantially cylindrical shape, containing a dip lamp 2i, for example a Xenon lamp with a continuous spectrum, or a mercury vapor lamp, is filled with a fluorescent liquid 28 which is capable of effecting the selection of a radiation particular desired, by absorbing high energy radiation (short wavelengths) and emitting in the vicinity of the most suitable irradiation wavelength; to allow an accurate measurement of the useful wavelength, it is advantageous to equip the device with an arrangement comprising a photon counter (such as Rhodamine B, for example) making it possible to determine the emission spectrum of the source Among the preferred fluorescent emissive liquids, there may be mentioned as non-limiting examples substances which have good spectroscopic properties which absorb the radiation emitted by the lamp, are not very photodegradable and have an emission spectrum which does not practically does not overlap with the absorption spectrum, these substances being taken from the group which includes in particular the PBD

(or phenyl-2- (biphenylyl-4) -5-oxadiazole-1,3,4) in solution in ethanol, anthranilic acid or salicylic acid, dissolved in water.

 FIG. 8 represents an annular reactor 29 whose wall 30 which delimits the internal space 33 is made of a material resistant to pressure stress, such as sapphire, quartz, etc., which is transparent to UV, whereas the wall outer 31 of the reactor 29 is stainless steel.

The lamp 32 is disposed axially in the interior space 33 delimited by the wall 30. A sensor 34 which has the role of measuring in situ the concentration of reagents introduced by the valve 36, is mounted in a window 35 made of sapphire, quartz or similar.

 Figure 9 shows a tubular reactor 37 made of a U.V. transparent material such as sapphire, quartz or the like; it is a closed reactor in which seals 38 are securely fixed in place by means of the metal fixing rods 39. This reactor 37 is irradiated by an external photon source.

 Although the method and the photochemical transformation devices defined and described in the foregoing have specifically referred to the phototransformation of hop extracts and more particularly of α-acids to iso-α acids, it is nevertheless clear that they can also be applied to various photochemical reactions of oxidation, or isomerization, for example for the manufacture of vitamins, hormones, basic constituents of perfumes, and in general many pharmaceutical and cosmetic products, without that this enumeration should be considered as limiting.

 As is apparent from the above, the invention is not limited to those of its modes of implementation, implementation and application which have just been described more explicitly; it encompasses all the variants that may come to the mind of the technician in the field, without departing from the scope or scope of the present invention.

Claims (23)

 1. A process for the photochemical transformation of hops obtained by treating hops with liquid or supercritical carbon dioxide, and more particularly by phototransformation of the acids contained in said iso acid extracts, which process is characterized in that said extracts comprising acids a and ss, in solution in liquid or supercritical carbon dioxide, are subjected to a photochemical irradiation process under pressure, to cause substantially quantitative conversion of α-acids to iso-acids.  2. Method according to claim 1, characterized in that the irradiation of the extract solution is carried out in the presence of liquid or supercritical CO 2, in a range of useful wavelengths between 250 nd and 450 nm, in a pressure between 50 and 300 bar and at a temperature between 00C and 750C.  3. Method according to any one of claims 1 and 2, characterized in that the irradiation of the extract solution is carried out by radiation of at least one photon emitter taken from the group which comprises lasers, lamps for discharge, incandescent lamps, the sun.  4. Method according to claim 3, characterized in that the radiation is emitted by a source of photons external to the reactor in which the photochemical transformation of the acid a to iso-is is carried out, and this radiation is emitted in a spectral range included between 250 nm and 450 nm.  5. Method according to claim 3, characterized in that the radiation is emitted by a non-stigmatic photon source disposed inside the reactor, in the solution to be irradiated.  6. A method according to claim 5, characterized in that the radiation is in the wavelength range from 350 nm to 450 nm and the radiations lower than 330 nm and greater than 370 nm are removed at a minimum. using at least one optical filter.  7. Method according to any one of claims 3 to 6, characterized in that the radiation or radiations providing the maximum reaction (s) (s) is (are) selected (s) by a filtering system selective optics.  8. Method according to any one of claims 3 to 7, characterized in that the wavelengths successively providing the maximum reaction yields as the progress of the reaction, are selected by a system of selective optical filtering according to the progress of the reaction.  9. A method according to claim 5, characterized in that the selection of the radiation (s) providing the optimum reaction yield (s) is carried out using a fluorescent relay consisting essentially of a fluorescent liquid interposed between the source of radiation and the chamber in which the reaction takes place.  10. Method according to any one of claims 5 to 9, characterized in that the radiation source is doped with a metal halide to change the spectrum of light lines emitted by the source.  11. Method according to any one of claims 1 to 10, characterized in that the hop extract subjected to the photochemical irradiation process is present at a concentration between x.10-3 and x.10-2 molar / liter.  12. Process according to any one of Claims 1 to 11, characterized in that the photochemical transformation of the hop extracts is carried out while the said extracts are in solution in carbon dioxide, to which a small amount of a coconut has been added. solvent such as ethanol, in particular.  13. A device for carrying out the process for converting hop extracts according to any one of claims 1 to 12, characterized in that it comprises, in combination, a reactor which comprises at least one window of irradiation and is associated with pressurizing means and at least one photon emitter.  14. Device according to claim 13, characterized in that the photon emitter is disposed outside the reactor.  15. Device according to claim 14, characterized in that in the case where the size of the window (5) is smaller than the reactor section (4), the latter is provided with a bar (6) diffuser disposed substantially in the axis of the window which ensures the irradiation of the inside of the reactor.  Device according to claim 13, characterized in that the photon emitter is a non-stigmatic emitter which is immersed inside the hop extract solution in the liquid or supercritical CO 2, possibly containing a small amount of one. co-solvent which may advantageously be ethanol.  17. Device according to claim 16, characterized in that the photon emitter (7) is constituted by a discharge lamp made of filter material.  18. Device according to claim 16, characterized in that the photon emitter is constituted by a discharge lamp associated with an optical filter.  19. Device according to any one of claims 16 to 18, characterized in that it comprises a plurality of reactors (9,11,13 ...) with plunging lamps (10,12,14 ...), mounted in series, whose radiation filtering means vary from one reactor to another.  20. Device according to claim 16, characterized in that it comprises a single reactor (21) coupled to a plurality of optical filters (23,24,25 ...) each of which absorbs a wavelength or range of appropriate wavelength which corresponds to a specific phase of the reaction.  21. Device according to claim 16, characterized in that it comprises a plurality of reactors (15,16,17) each of which is coupled to an optical filter associated with a source of photons.  22. Device according to claim 13, characterized in that the reactor (31) has an annular shape in the center of which is mounted a source of photons (32).  23. Device according to claim 13, characterized in that it comprises a reactor (26) of substantially cylindrical shape inside which is mounted axially a photon source (27) which is surrounded by a fluorescent relay (28) constituted by a solution of a fluorescent substance which substantially fills the space between the reactor wall and the source of photons such as lamp in particular.