PROCESS FOR TREATMENT OF FLUIDS BY PULSED ELECTRIC FIELDS AND IMPLEMENTATION DEVICE

Abstract

The present invention relates to the treatment of fluids containing unicellular or multicellular organisms such as bacteria, yeasts, fruits and vegetables, or pieces of fruits and vegetables, for the purpose of juice extraction and / or decontamination, and more particularly to grapes, juice apples, and cider apples, in order to improve not only juice extraction yields but also the extraction of solutes contained in plant cells by means of pulsed electric fields, characterized in that the duration of each pulse is controlled either by the temperature of the fluid at the module outlet so as not to exceed a predetermined maximum temperature or by the maximum intensity of the current received or emitted by the generator. Figure for the abstract: Fig.

Description

Title of the invention: METHOD FOR TREATING FLUIDS BY PULSED ELECTRIC FIELDS AND DEVICE FOR IMPLEMENTING SAME

[0001] The present invention relates to the field of solid-liquid extraction from plant raw material such as fruits or vegetables.

[0002] Food products resulting from the processing of fruits and vegetables are numerous and varied and the mechanical destruction of plant matrices constitutes a step that is often essential in the manufacturing process aimed at extracting a liquid or soluble compounds contained in plant cells; compounds that we seek, for example, to purify.

[0003] Whether it is classically a question of processes for manufacturing fruit juice or vegetable juice where the aim is to improve the juice extraction yield, whether it is a question of dried product from which the aim is to eliminate the water, or whether it is simply the search for the extraction of solutes (e.g. beet sugar), industrial food processes generally seek to improve the transfer of matter in order to obtain a given substance or to remove the water from a plant or even animal raw material.

[0004] In the particular context of winemaking, we will seek to maximize the solid-liquid extraction yield in general and more particularly the extraction of certain compounds and constituents of the grape.

[0005] The grape constituents that play a major role in the qualitative expression of wines are essentially contained in the skin cells of the grape berry. A high proportion of the aroma compounds and aromatic precursors are found in these skin tissues.

[0006] For several years, thermovinification has been used to improve the extraction of compounds from grape skin cells during red maceration. This technique consists of heating the harvest for a few minutes at 70°C, then leaving it to macerate at this temperature for 30 to 40 minutes. The grapes are then pressed. The resulting juices will then be cooled and fermented in the liquid phase. While thermovinification eliminates laccase, the enzyme responsible for oxidation phenomena, it also offers the advantage of promoting the extraction of skin compounds such as tannins, anthocyanins, primary aromas and polysaccharides.

[0007] This technique also makes it possible to improve the juice extraction yields from grape berries in addition to improving the extraction of soluble compounds contained in plant cells, whether sugars, pigments, or any other compound contributing to the taste, color or aroma of the wines obtained.

[0008] The results concerning the extraction of compounds such as anthocyanins, proanthocyanidins, catechins and flavonols consist of better extraction yields and higher contents, an improvement in the coloring intensities but however a significant loss of these advantages during the conservation of the wines. The limitation of the process concerns in particular the loss of color during the months following vinification.

[0009] In parallel with the gain observed for polyphenols, an evolution of the sensory characteristics of wines resulting from heat treatment of the harvest has been highlighted.

[0010] This technology is presented as making it possible to erase vegetal notes and bitterness on certain grape varieties harvested at low maturity or to promote fat or balance and reduce the sensation of acidity on others.

[0011] These various advantages also have their disadvantages. In fact, heating leads to an inactivation of certain grape enzymes as well as an increase in the extraction of certain polysaccharides (i.e. pectins) which are not extracted during conventional vinification. This leads to difficulties in clarifying wines produced by heat treatment. It will then be necessary to add enzymes to facilitate clarification, but the result will not always be ideal.

[0012] Furthermore, temperature control is an important parameter that cannot always be perfectly controlled and thermal inertia can lead to overheating of the treated mixture.

[0013] Finally, the heat treatment will necessarily impact the yeasts and bacteria present on the grapes and the subsequent fermentation will be prolonged or will require an addition of microorganisms.

[0014] Numerous extraction intensification techniques have also been developed, such as pulsed electric fields. These intensification techniques act on the membranes and / or cell walls of the cells constituting the solid plant matrix to facilitate solid / liquid extraction and more particularly of molecules of interest contained in the plant cells.

[0015] These techniques use electrical pulses to concentrate, in very short times, electrical energy previously stored in a capacitor. This electrical energy is then injected into a treatment chamber comprising the solid plant matrix. This very sudden injection of electrical energy into the chamber makes it possible to unbalance the physical, biological and / or chemical properties of the biomembrane of the cells of the solid plant matrix which can present very interesting characteristics for the extraction of biological molecules.

[0016] The pulsed electric field can also act on the intracellular contents of the cell (for example, detach the cell membrane from the wall as well as disorganize its intracellular contents).

[0017] The electroporation technique, which consists of applying an electric field to cells, makes it possible to permeabilize their membrane and, under certain conditions, to extract all or part of the cellular content, in particular molecules of interest for fruits and vegetables. This electric field induces changes in the potential difference of the plasma membrane and leads to its transient destabilization (Teissié et al, 2005). This phenomenon allows the entry and exit of the cell of non-permeant molecules, i.e. molecules which cannot diffuse through the membrane or the cell wall spontaneously.

[0018] Document FR3025216 describes a method for extracting lipids from microalgae cells suspended in a buffered liquid medium.

[0019] However, pulsed electric field technologies induce additional processing costs, implementation complexity, and the nutritional, technological (clarification) and taste qualities of the juices may be affected.

[0020] In addition to optimizing the characteristics of the applied pulsed electric fields (voltage, duration, frequency, etc.), various complementary techniques have been used to complement or assist pulsed electric field technology in order to further maximize the extraction of solutes from cells. The use of organic solvents, enzymes such as pectinases, or prior grinding steps can further improve the extraction yield. However, these co-treatments have their limits both in terms of cost and environmental impact or on the product itself.

[0021] There therefore arises a need to provide a method for treating fluid containing plant cells and / or microbial cells, in particular plant products such as fruits and vegetables for the purpose of extracting juice and more particularly harvest grapes, juice and cider apples, for example, in order to improve not only the extraction yields in juice but also in solutes contained in the plant cells (simple complex sugars, enzymes, pigments and other aromatic molecules, etc.) and / or decontaminate said fluid while not having the disadvantages of the known thermal treatment techniques, by solvents or by pulsed electric fields.

[0022] It is thus a first object of the present invention to provide a method for the continuous treatment of a fluid comprising an aqueous liquid phase and organisms, said method comprising the following steps: - reception of said fluid, - circulation of the fluid in homogeneous flow through at least one module of treatment comprising a pipe abutting a pulsed electric field chamber connected to an electric pulse generator, - optionally, maceration of the treated fluid, - recovery of the treated fluid, the duration of each pulse being controlled by at least one parameter chosen from: - the temperature of the fluid at the module outlet, in particular so as not to exceed a predetermined maximum temperature, - the maximum intensity of the current received or emitted by the generator.

[0023] In a particular embodiment of the method according to the invention, the control of the duration of each pulse to the temperature of the fluid at the module outlet or to the maximum intensity of the current received or emitted by the generator is carried out by a proportional-integral-derivative regulator.

[0024] The regulation measures continuously by means of temperature and / or intensity sensors. The information is sent to a regulator which compares these measurements to the set value(s) and then, following an algorithm, will transmit its orders, in this case, to an H-bridge in order to vary the duration of the pulses and therefore correct the disturbances and prevent the fluid from overheating or the system from tripping.

[0025] Being able to regulate the temperature via the duration of the electrical pulses - all of whose energy is converted into heat by the Joule effect - makes it possible to preserve the organoleptic properties of food and even avoid any start of fermentation in the case of juice production.

[0026] The thermal increment of a homogeneous liquid volume subjected to pulsed electric fields is governed by the following equation: AT=E2 * o * t * N / C * p with: - AT: temperature rise of the liquid per pattern, in °K, - E: electric field, in V / m, - o: conductivity of the liquid, in S / m, -1: duration of a pulse, in seconds, - N: number of pulses received by the volume, - C: specific heat capacity of the liquid, in J / (kg*K) - p: density of the fluid, in kg / m3.

[0027] In the context of the present invention, the term "organism" or "organisms" is understood as referring to a biological system consisting of one or more cells, thus we speak of a unicellular or multicellular organism. By multicellular organism, we mean here a set of differentiated or non-differentiated cells, in contact, representing all or part of an organism. Thus by multicellular organism, the present description refers to clusters of plant cells, fractions or pieces of fruit or vegetables, plant tissues, fruit pulp or vegetables, whole fruits or vegetables made up of a plurality of plant cells.

[0028] By unicellular organism, reference is made in the present application to cells of bacteria or yeasts or even unicellular algae.

[0029] Thus, in one embodiment of the present method, the organisms are chosen from the group comprising unicellular organisms and multicellular organisms.

[0030] In another embodiment the unicellular organisms are selected from the group consisting of bacteria, yeasts and algae.

[0031] In one embodiment, the multicellular organisms are selected from the group consisting of plant fragments, plant tissues, clusters of plant cells, fruit or vegetable pulp, whole fruits or vegetables consisting of a plurality of plant cells.

[0032] In a particular embodiment, the method according to the invention is characterized in that the flow is turbulent.

[0033] Indeed, it has been observed that in the case of a laminar flow of the fluid, the organisms at the center of the flow - faster than those at the edges - receive fewer electrical impulses. This is even more the case when several modules are arranged in series. In such a case, it is the same cells of organisms which are the least exposed to the electric field in the successive chambers. Corollary, it is the same cells at the edges which are more exposed and which undergo a greater number of electrical impulses. By achieving a circulation in turbulent flow, the cells of organisms are subjected to turbulence allowing a better distribution of the speeds of the cells of organisms within the flow of matter, and generating movements exposing all the faces of the cells of the organisms.This allows the matter of organisms to be treated in a more homogeneous manner, both for permeabilization by pulsed electric fields but also for a more homogeneous distribution of temperature increase by Joule effect, thus minimizing the deterioration of heat-sensitive compounds.

[0034] In a particular embodiment, the method according to the invention is characterized in that the number of processing modules is between 2 and 10, preferably between 3 and 6.

[0035] The succession of processing modules makes it possible to multiply the application of electric fields to the matter of the organisms moving in the fluid.

[0036] In a particular embodiment, the method according to the invention is characterized in that the modules are arranged in series or in parallel or a series / parallel combination, preferably in series.

[0037] In a particular embodiment, the method according to the invention is characterized in that the flow rate of the fluid in at least one module is between 1 and 200 tonnes / hour, particularly between 5 and 60 tonnes / hour.

[0038] In a particular embodiment, the method according to the invention is characterized in that the multicellular organisms are chosen from the group consisting of whole fruits or vegetables, crushed fruits or vegetables, crushed fruits or vegetables, fruits or vegetables cut into pieces, grated fruits or vegetables, crushed fruits, vegetables or algae, or a mixture.

[0039] The whole fruits or vegetables that can be treated according to the method according to the invention can be grapes, potatoes or tomatoes for example. The grapes resulting from destemming can be whole or slightly crushed. The treatment of these organisms allows an alteration of the cell walls and membranes which become porous with altered mechanical properties. This will allow a better extraction of juice and solutes in the case of grapes or tomatoes. This will allow an easier peeling of tomatoes if we seek to keep them intact. The potatoes will, for their part, undergo a softening, which will facilitate their cutting or slicing during the manufacture of processed products such as chips or fries for example.

[0040] The method according to the invention is also applicable to fruits and vegetables from which one seeks to extract the juice and to maximize the extraction yield, such as apples or carrots which will be cut, grated or crushed before being subjected to the method according to the invention.

[0041] In a particular embodiment, the method according to the invention is characterized in that the aqueous liquid phase is chosen from the group consisting of juice, in particular plant juice, from organisms, in particular plant organisms such as plant cells, pieces of plant, an aqueous solvent, a hydroalcoholic solvent, or a mixture.

[0042] The liquid phase may in fact come from external water acting as a vector for the organisms. It may also be vegetation water released following mechanical actions applied (crushing, destemming, slicing, grinding, grating, etc.) on organisms such as fruits, vegetables, cells, fractions and pieces of vegetables or fruits, or algae. It may also be a combination of the two.

[0043] Depending on the nature and quantity of the organisms included in the treated fluid, it will resemble a juice, a pulp or a more or less fluid paste. In all cases, however, it is a more or less pasty pumpable fluid in which the organisms constitute a phase dispersed in a liquid phase (water and / or juice).

[0044] In a particular embodiment, the method according to the invention is characterized in that the electric field within the pulsed electric field chamber is between 50 and 8000 V / cm, particularly between 100 and 1000 V / cm, more particularly mainly between 300 and 500 V / cm.

[0045] The advantage of such moderate electric fields is to promote the multiplication of membrane defects (reversible electroporation), rather than membrane destruction by more intense electric fields (irreversible electroporation).

[0046] In a particular embodiment, the method according to the invention is characterized in that the duration of each electrical pulse emitted by the generator is between 100 ps and 100 ms, preferably between 1 ms and 10 ms. As indicated above, the duration of each pulse will be controlled by the set temperature not to be exceeded or by the intensity not to be exceeded.

[0047] In fact, when an electric field is applied, a Joule effect occurs which tends to heat the medium and increase the temperature of the fluid.

[0048] In a particular embodiment, the method according to the invention is characterized in that the frequency of the electrical pulses emitted by the generator is between 1 and 10,000 Hz, preferably between 40 and 1,000 Hz.

[0049] In a particular embodiment, the method according to the invention is characterized in that the number of electrical pulses received per organism cell is between 1 and 1000, particularly between 5 and 500 and more particularly between 6 and 60.

[0050] In a particular embodiment, the method according to the invention is characterized in that the electrical pulses emitted by the generator are alternately positive and negative.

[0051] In a particular embodiment, the method according to the invention is characterized in that the polarity inversion is carried out between each electrical pulse or between each group of electrical pulses within the same period.

[0052] In a particular embodiment, the method according to the invention is characterized in that the polarity inversion is carried out by an H-bridge with power switching transistors.

[0053] In a particular embodiment, the method according to the invention is characterized in that the positive and negative electrical pulses of the same period are of the same duration.

[0054] In a particular embodiment, the method according to the invention is characterized in that the duration between two electrical pulses is less than 10 ms, particularly less than 500 ps and greater than 1 ps, more particularly still less than 500 ps and greater than 50 ps.

[0055] In a particular embodiment, the method according to the invention is characterized in that the waveforms of the electrical pulses are square, trapezoidal, triangular, sinusoidal, rectified sinusoidal.

[0056] In a particular embodiment, the method according to the invention is characterized in that the pulses are unipolar, symmetrical bipolar or asymmetrical.

[0057] In a particular embodiment, the method according to the invention is characterized in that the electrical pulses of the generator are sinusoidal, bipolar and symmetrical rectified, in particular via a three-phase full-wave rectifier bridge followed by an H-bridge.

[0058] In a particular embodiment, the method according to the invention is characterized in that the optional step of maceration of the treated fluid is carried out for a period of between 10 minutes and 30 days, more particularly between 30 minutes and 48 hours, in particular at a temperature corresponding to the temperature used for controlling the duration of the electrical pulses.

[0059] In a particular embodiment, the method according to the invention is characterized in that the optional maceration step is carried out at a temperature corresponding to the temperature used for controlling the duration of the electrical pulses.

[0060] This optional maceration step allows diffusion of the solutes present in the cells, in particular the skin cells of plant organisms, in particular grapes. These solutes belonging to the family of polyphenols such as for example anthocyanins, proanthocyanidins, catechins, flavonols and other solutes such as polysaccharides are released into the liquid phase in an increased manner while avoiding accentuated heating which is detrimental to the quality of the wines which will be produced from them.

[0061] In a particular embodiment, the method according to the invention may comprise a solid / liquid separation step when the treated fluid is loaded with organisms and it is desired to recover a solid phase freed from said organisms. Such a solid / liquid separation may be carried out by a technique chosen from pressing, decantation, filtration, centrifugation, used alone or in combination.

[0062] In a particular embodiment, the method according to the invention is characterized in that the passage of the fluid in homogeneous flow through at least one treatment module is carried out by a pump, an endless screw or a belt conveyor.

[0063] The fluid can circulate, pushed by a pump or a screw without wine, within a conduit abutting the chamber containing the electrodes; in another alternative embodiment, the fluid can also be in circulation on a conveyor belt with an electrode flush with the level of said belt.

[0064] In a particular embodiment, the method according to the invention is characterized in that the organisms are chosen from the group consisting of fruits and vegetables. The fruits and vegetables are chosen from the group consisting of grapes, apples, tomatoes, potatoes, beets, carrots and olives.

[0065] The invention also relates to a device for implementing a method according to one of previous embodiments characterized in that it comprises a means of bringing the fluid, at least one treatment module in which the fluid circulates, said module consisting of a pipe abutting a chamber with pulsed electric fields, said chamber being connected to an electric pulse generator, characterized in that the generator comprises: - optionally, an RFI filter limiting high-frequency disturbances to and from the electricity supplier, - a three-phase transformer, - a three-phase full-wave rectifier bridge, - an H-bridge to which one or more pulsed electric field chamber modules are connected, enabling bipolar pulses to be produced, the duration of which can be controlled by at least one parameter chosen from: i) the temperature of the fluid at the module outlet so as not to exceed a predetermined maximum temperature and ii) the maximum intensity of the current received or emitted by the generator, - a temperature sensor at the module output and / or a current sensor located upstream of the transformer or between the transformer and the processing modules, - a proportional-integrator-derivative (PID) control system for controlling the power switches of the H-bridge in order to vary the pulse duration. The PID control system can be implemented via a microcontroller or microprocessor with a suitable algorithm.

[0066] In a particular embodiment, the device according to the invention is characterized in that the pulsed electric field chamber comprises two flat and parallel electrodes whose spacing is between 0.3 and 10 cm.

[0067] In a particular embodiment, the device according to the invention is characterized in that the spacing of the pulsed electric field chambers is between 5 and 10 times, particularly 7 times, the spacing of the electrodes of the pulsed electric field chamber and is between 30 cm and 1 m.

[0068] In a particular embodiment, the device according to the invention is characterized in that all or part of the pipe of each module has a conformation such that it generates a turbulent flow.

[0069] In a particular embodiment, the device according to the invention is characterized in that all or part of the pipe comprises at least one constriction with a square, rectangular or rounded section in a helix or ring on its internal face.

[0070] Thus, all or part of the pipe may have corrugation or twisting.

[0071] A corrugated tube has the advantage of breaking the film layer near the tube wall and breaking the laminar flow and introducing turbulence.

[0072] In a particular embodiment, the device according to the invention is characterized in that the output voltage of the generator is raised by a three-phase transformer in a transformation ratio between 2 and 10.

[0073] In a particular embodiment, the device according to the invention is characterized in that the transformer is of the triangle-triangle type.

[0074] In a particular embodiment, the method is characterized in that the fluid comprises organisms chosen from bacteria and / or yeasts, said method allowing the deactivation of said organisms by their irreversible electroporation by limiting the temperature rise of the fluid from 30°C to 40°C.

[0075] The process is thus suitable for the decontamination of the treated fluid. For such microbial deactivation, an increase in temperature, for example 30°C is followed by rapid cooling so as not to degrade the juices, far from pasteurization which goes from 0 - 5°C to more than 70°C, also with rapid cooling to limit degradation. The advantage of the process is that it does not require specific parameters per type of juice. The maximum outlet temperature is specified and the pulses are controlled in duration and not in pulse frequency. In doing so, single-celled organisms, i.e. microorganisms, are systematically reached and destroyed from the moment the frequency is not varied for a given flow rate. Brief description of the drawings

[0076] The invention will be better understood on reading the following description of exemplary embodiments, with reference to the appended drawings in which:

[0077] [Fig. 1] represents an installation for extracting and pressing grape or apple juice assisted by pulsed electric fields.

[0078] [Fig.2] represents a type of pulses produced using the generator according to the present invention.

[0079] [Fig.3] represents an impulse chamber (top view and bottom view) to which a supply pipe and an outlet pipe are joined. EXAMPLE

[0080] The juice extraction installation assisted by pulsed electric fields shown in [Fig.l] comprises, at the start of the chain, means for recovering the material containing organisms, whole grape grains or pieces, which is then conveyed - for example by an endless screw - into the pulse chambers before being poured into a buffer tank or directly into a press or any other juice extraction system (decantation, filtration or centrifugation).

[0081] The pulse chambers are connected to one or more pulsed electric field generators. Preferably, only one.

[0082] The pulsed electric field generator used for the economical method of the present invention consists in particular of: - an RFI filter limiting high-frequency disturbances to and from the electricity supplier, - a three-phase transformer, preferably delta-delta, with a transformation ratio of between 2 and 10, preferably between 3 and 5, in particular 3.15 - a three-phase full-wave rectifier bridge, whose output voltage oscillates between 1.5 and ^3 times the maximum voltage per phase rectified at the transformer output, with a bank of capacitors to absorb voltage peaks linked to the transformer's counter-electromotive force. - an H-bridge within which the impulse chambers are connected, as well as its control system allowing the generator to be controlled.

[0083] The H-bridge consists of 4 power switching transistors - arranged schematically in the form of H - in order to enable bipolar pulses to be produced, the duration of which can be controlled by the power constraints of the installation (current control) or by the needs of the process (control based on the temperature at the output of the pulse chambers).

[0084] The control is represented in [Fig.2] by the variation of the duration of the variables Tp and Tn (duration of the positive and negative pulses) whose sum is between 0 and 95% of the variable P. The latter corresponds to the unit period of the electrical signal whose pattern is repeated throughout the treatment of the fluid.

[0085] An integrated circuit, of the microcontroller or FPGA type, recovers the information: - from the temperature sensor at the output of the last pulse chamber and / or, - from a current intensity sensor located on a phase upstream of the transformer or downstream between the transformer and the pulse chambers, and carries out closed-loop control of the process by means of a proportional-integrator-derivative (PID) regulator, by controlling the power switches of the H-bridge to vary the durations of the positive and negative pulses of each period.

[0086] A pulse chamber as shown in [Fig.3] may be combined in series with another identical chamber. The chambers in series may be connected to one or more generators.

[0087] The tube connecting the worm screw to the impulse chambers, the tube connecting the impulse chambers to each other as well as the tube connecting them to the buffer tank or to the press can be cylindrical, preferably corrugated, or of any other cross-sectional shape allowing for a flow, preferably turbulent, of plant material. The cross-section shown is square with a rotation of the cross-section of half a turn between two impulse chambers.

[0088] Turbulence is useful for limiting the difference in material velocity between the center and the edges of the pulse chamber. This allows the material to be treated plant material in a more homogeneous manner, both for permeabilization by pulsed electric fields but also for a more homogeneous distribution of temperature increase by Joule effect, thus minimizing the deterioration of heat-sensitive compounds such as aromas.

[0089] The impulse chambers here have a spacing between electrodes of 4 to 10 cm, with an electrode length preferably at least equal to the spacing in order to have theoretical electric field lines of an intensity closest to the voltage difference between the electrodes divided by their spacing.

[0090] The distance between two pulse chambers is preferably at least equal to 5 times the spacing of the electrodes of the same pulse chamber, to limit the crossed field lines between chambers which permeabilize the cells little, but also to increase the duration between the passages in each chamber, in order to increase the permeabilization of the cells of the plant organisms.

[0091] For grape harvest treatment processes, the increase in temperature by Joule effect is decisive for improving the extraction of polyphenols, polysaccharides and aroma precursors during the maceration and pressing phases, and is more effective and less expensive than heating the walls of an exchanger or an external heat transfer fluid.

Claims

Claims

1. Method for the continuous treatment of a fluid comprising an aqueous liquid phase and organisms, said method comprising the following steps: - reception of said fluid, - circulation of the fluid in homogeneous flow through at least one treatment module comprising a pipe abutting a pulsed electric field chamber connected to an electric pulse generator, - optionally, maceration of the treated fluid, - recovery of the treated fluid, characterized in that the pulsed electric field chamber comprises two flat and parallel electrodes whose spacing is between 0.3 and 10 cm and all or part of the pipe comprises at least one constriction with a square, rectangular or rounded section in a helix or ring on its internal face, and in that the duration of each pulse is controlled by at least one parameter chosen from: - the temperature of the fluid at the module outlet,- the maximum current intensity received or emitted by the generator.,

2. Method according to claim 1, characterized in that the duration of each pulse of the electrical pulse generator is between 100 ps and 100 ms, preferably between 1 ms and 10 ms.

3. Device for implementing a method according to one of the preceding claims, characterized in that it comprises a means for supplying the fluid, at least one treatment module in which the fluid circulates, in that said module consists of a pipe abutting a pulsed electric field chamber, said chamber being connected to an electric pulse generator, in that the pulsed electric field chamber comprises two flat and parallel electrodes whose spacing is between 0.3 and 10 cm, in that all or part of the pipe comprises at least one constriction with a square, rectangular or rounded section in a helix or ring on its internal face and in that the generator comprises: - optionally, an RFI filter limiting high-frequency disturbances to and from the electricity supplier, - a three-phase transformer with a transformation ratio of between 2 and 10 to increase the voltage at the generator output, - a three-phase full-wave rectifier bridge, - an H-bridge to which one or more pulsed electric field chamber modules are connected for producing bipolar pulses whose duration can be controlled by at least one parameter chosen from: i) the temperature of the fluid at the module outlet so as not to exceed a predetermined maximum temperature and ii) the maximum intensity of the current received or emitted by the generator, - a temperature sensor at the module outlet and / or an intensity sensor located upstream of the transformer or between the transformer and the processing modules, - a proportional-integrator-derivative (PID) control system for controlling the power switches of the H-bridge in order to vary the duration of the pulses.

4. Device according to claim 3, characterized in that the spacing of the pulsed electric field chambers is between 5 and 10 times, particularly 7 times, the spacing of the electrodes of the pulsed electric field chamber and is between 30 cm and 1 m.

5. Device according to one of claims 3 or 4, characterized in that all or part of the pipe may represent a corrugation or a twist.

6. Device according to one of claims 3 to 5, characterized in that the transformer is of the triangle-triangle type.

7. Device according to one of claims 3 to 6, characterized in that the duration of each pulse of the electrical pulse generator is between 100 ps and 100 ms, preferably between 1 ms and 10 ms.

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