FR3138146A1 - DEVICE AND METHOD FOR MICROBIOLOGICAL STABILIZATION OF A LIQUID - Google Patents

Abstract

The present invention relates to a device for the microbiological stabilization of a liquid, comprising: - a transparent tube (1) with an internal diameter (di) of between 0.2 and 20 mm, of helical shape, in which the ratio between the internal diameter (di) of the tube (1) and the helical diameter (dc) is between 0.0025 and 0.6, and - at least one source (2) emitting UV-C radiation of wavelengths included between 100 and 280 nm. The present invention further relates to a use of a device according to the invention, for the microbiological stabilization of a liquid, in particular a liquid absorbing UV-C radiation. The present invention also relates to a process for microbiological stabilization of a liquid, comprising the following steps: - flow, in a tube (1) of a device according to the invention, of a liquid, - treatment, during the flow, of the liquid by UV-C radiation of wavelengths between 100 to 280 nm emitted by at least one source (2) of a device according to the invention. Figure 2

Description

DEVICE AND METHOD FOR MICROBIOLOGICAL STABILIZATION OF A LIQUID

The present invention relates to a device for the microbiological stabilization of a liquid, to a use of this device as well as to a method for the microbiological stabilization of a liquid.

The present invention finds applications in particular in the field of the food industry, and in particular in the field of oenology.

In the description below, references in square brackets ([ ]) refer to the list of references presented at the end of the text.

State of the art

From the grape, the qualities of the wine integrate all the microbial developments caused or suffered during its production. Some of these metabolisms are necessary. This is the case of alcoholic fermentation by the yeast Saccharomyces cerevisiae and of malolactic fermentation by the lactic acid bacteria Œnococcus Œni . Other activities also help to enrich the aromatic potential of the grapes. However, not all microbial interventions are beneficial. Indeed, some lead to harmful physical and/or aromatic modifications. This is why microbiological stabilization of wines is necessary during their production.

Filtration is the physical process most currently used in oenology for microbiological stabilization. This is a process for separating the constituents of a mixture which has a liquid phase and a solid phase through a porous medium. Thus, it is possible to retain yeasts and bacteria present in wines by using filters with a pore size of less than 0.4 μm. The main problem with this technology is the clogging of the membrane by suspended solids, such as polysaccharides, polyphenols and proteins contained in wines. This phenomenon leads to a drop in membrane permeability and therefore reductions in productivity and additional maintenance costs (El Rayess et al., 2011 ([1])). Consequently, this process is used before bottling, when the wine contains few suspended particles following racking.

Thermal stabilization consists of bringing the must or wine to a sufficient temperature to eliminate all the microorganisms it contains. The heating speed and the duration during which the set temperature is maintained are the two main parameters which will determine the effectiveness of the treatment. Generally, the wines are brought to 72°C for 15 to 30 seconds and cooled quickly afterwards: this is flash pasteurization, also called thermoflash. However, this treatment alters the organoleptic qualities of the wines.

Other physical processes exist, using high pressures or pulsed electric fields, but they have such drawbacks that it is difficult to imagine their application to the wine industry.

UV-C radiation (100 to 280 nm) is known for its germicidal effect and is already applied in the treatment of water, cider (Koutchma et al., 2004 ([2])), milk (Bandla, 2010 ; Bandla et al., 2012 ([3])), fruit juices (Baysal et al., 2013 ([4]); Franz et al., 2009 ([5]); Guerrero-Beltran et al., 2009 ([6]); Keyser et al., 2008 ([7]); Müller et al., 2011 ([8]); Murakami et al., 2006 ([9]) or even liquid eggs (de Souza et al., 2014 ([10])). In all these cases, UV-C treatment is interesting because it does not require chemicals and does not produce effluents.

However, due to the low penetration capacity of UV-C radiation in certain food liquids, the role of this process has often been limited to the disinfection of surfaces and packaging (Koutchma, 2009 ([11])). Indeed, absorbing liquids, such as wine, strongly limit the depth of penetration of the radiation and therefore the effectiveness of the process. The development of new reactors with optimized hydrodynamic parameters does not currently allow the treatment of liquids with high absorbance of UV light. Indeed, the sine qua non condition for the process to be effective is the exposure of microorganisms to UV-C photons (Bintsis et al., 2000 ([12])). Microorganisms located far from the light source in an absorbent liquid can be protected from it by the thickness of liquid between them.

Recent studies have focused on UV-C treatment of fruit juices (Islam et al., 2016 ([13])) or beer (Mezui & Swart, 2010 ([14])). Until now, only a few studies have dealt with grape must or wine processing (Fredericks et al., 2011 ([15]); Rizzotti, Levav, Fracchetti, Felis and Torriani, 2015 ([16]), Junqua et al, 2020 ([17]), Diesler et al, 2019 ([18])). These studies show (i) the microbiological stabilization capabilities of UV-C on different microorganisms with the associated doses for each case and (ii) that the taste of light does not appear following these treatments.

Thus, UV-C treatments are recognized but no pilot allows the treatment of wines on an industrial scale.

There is therefore a real need to provide a technical solution to effectively treat liquids, particularly liquids absorbing UV-C radiation such as wine or must, for all microorganisms, on an industrial scale.

Description of the invention

The present invention aims precisely to meet these needs and disadvantages of the prior art.

The inventors have in fact developed a device and a process making it possible to stabilize liquids, in particular liquids absorbing UV-C radiation such as wines and musts, without impacting their organoleptic characteristics.

Advantageously, the invention makes it possible to reduce the concentrations of inputs, such as sulfur dioxide, in oenology, particularly on an industrial scale.

The inventors have notably succeeded, after significant work, in developing a helical UV-C reactor, based on the hydrodynamic properties of Dean vortices, to improve the efficiency and homogeneity of microbiological treatments of liquids, in particular wines and musts.

Advantageously, the process of the invention is athermal, compact, does not require a large investment, can operate continuously and has a particularly interesting energy balance, notably lower than that of the physical stabilization treatments of the prior art.

Thus, a first object of the invention relates to a device for the microbiological stabilization of a liquid, comprising:
- a transparent tube with an internal diameter (di) of between 0.2 and 20 mm, of helical shape, in which the ratio between the internal diameter (di) of the tube and the helical diameter (dc) is between 0.0025 and 0.6, and
- at least one source emitting UV-C radiation with wavelengths between 100 and 280 nm.

The term “microbiological stabilization”, within the meaning of the present invention, means the elimination of all or part of the yeasts and/or bacteria likely to alter the balance or the visual, olfactory or taste properties of the liquid. For example, it may be at least one yeast chosen from Saccharomyces cerevisiae , Candida vini , Pichia membranaefaciens , Brettanomyces bruxellensis , Zygosaccharomyces bailii and Saccharomycodes ludwigii , and/or at least one bacterium chosen from A.aceti , Lactobacillus hilgardii , Lactobacillus diolivorans , Pediococcus parvulus and Pediococcus damnosus . Advantageously, the elimination can concern a reduction in population, for example by going from 10 ⁷ CFU/ml to less than 10 CFU/ml.

The term “liquid”, within the meaning of the present invention, means any liquid, and in particular liquids absorbing UV-C radiation. These may include, for example, alcoholic beverages, fruit juices and must, as well as their mixtures. Among alcoholic drinks, we can cite in particular wine, for example white, rosé, red or sweet, as well as beer. It can also be water, cider or milk.

Advantageously, the transparent tube can be made of any transparent material, that is to say which allows light to pass through and the liquid which is in the tube to appear clearly. This may be, for example, glass, polyethylene (PET) or fluorinated ethylene propylene (FEP). The transparency of the tube avoids limiting the depth of penetration of UV-C radiation into the liquid.

Advantageously, the internal diameter (di), the shape and the ratio between the internal diameter (di) of the tube and the helical diameter (dc) of the transparent tube make it possible to control the dynamics of the fluids around the UV-C source and to treat liquids evenly. In particular, a specific ratio between the internal diameter (di) and the helical diameter (dc) (corresponding to the winding diameter of the tube around the UV-C lamp) allows the creation of Dean vortices (counter-rotating vortex cells) in the tube, improving the efficiency and homogeneity of the treatment. Knowing that the penetration depth of UV-C radiation in absorbent liquids, notably wines, is very low (from 0.2 to 2 mm depending on the wines), these vortices allow the liquid to rotate in the tube and thus promoting liquid/lamp contact.

The internal diameter (di) corresponds to the diameter between the internal walls of the tube, and is between 0.2 and 20 mm, for example 0.5 and 18 mm, or between 1.0 and 15 mm, or between 2.0 and 12 mm, or between 4.0 and 10.0 mm.

Advantageously, the ratio between the internal diameter (di) of the tube and the helical diameter (dc) is adjusted to facilitate the flow of the liquid through the tube. It is between 0.0025 and 0.6, for example between 0.15.

Advantageously, the tube being of helical shape, the distance between the turns thereof can be between 0 and 80 mm.

The source emitting UV-C radiation with wavelengths between 100 and 280 nm can be any commercially available lamp. For example, it may be a low-pressure amalgam UV-C lamp. Advantageously, it may be a lamp emitting at a wavelength of 254 nm.

Advantageously, the source emitting UV-C radiation can be close to the transparent tube, so that the microorganisms are sufficiently exposed to UV-C photons. In addition, as explained previously, the proximity between the UV-C radiation source and the tube is also ensured thanks to the control of the fluid dynamics around the UV-C source, which makes it possible to treat liquids homogeneously. , especially absorbent liquids.

Advantageously, the transparent tube can be wound around the UV-C source, which can itself have the shape of a tube. The helical shape of the tube advantageously allows this winding, and optimized proximity between the UV-C source and the liquid to be treated.

According to the invention, the device may further comprise a support, around which the transparent tube is wound. In this case, the source emitting UV-C radiation can be supported or integrated into this support. For example, the support can be a quartz sheath, in particular containing the UV-C radiation source.

Advantageously, the device of the invention can comprise a number of sources emitting UV-C radiation allowing the desired effect to be obtained. This number may depend on the UV-C dose emitted by each source, and can be determined by those skilled in the art based on their general knowledge. The UV-C fluence level can further be adjusted for each individual product based on their characteristics, for example viscosity, and microbial reduction requirements. These sources can be arranged in series or in parallel. For example, the device may further comprise from 1 to 200 source units emitting UV-C radiation, in particular 3 to 170 units, or 10 to 150 units, or 20 to 120 units, or 50 to 150 units. Each unit can deliver for example between 50 and 20000 J/L, for example between 100 and 15000 J/L or between 100 and 6000 J/L.

Advantageously, the device of the invention may further comprise a means of controlling the flow rate and/or a means of controlling the temperature of the liquid in the device. These parameters can be adjusted by those skilled in the art according to the characteristics of each liquid to be treated. The flow rate can be controlled by a flow meter and the temperature by a thermometer. Sensors can be placed on all or part of the device. Advantageously, a suitable flow rate can result in a high radial speed in the tube and thus guarantee homogeneous treatment of the liquid. Advantageously, a flow rate greater than 200 L/h allows treatment on an industrial scale, while limiting pressure losses and energy consumption. Controlling the temperature can advantageously prevent alteration of the organoleptic qualities of the liquid.

The device of the invention can also contain any element necessary for controlling the parameters mentioned above such as a power supply and control panel, a pump, a tank as well as control valves.

Another object of the invention relates to the use of the device of the invention for the microbiological stabilization of a liquid as defined above, in particular a liquid absorbing UV-C radiation.

Another object of the invention relates to a process for microbiological stabilization of a liquid, comprising the following steps:
- flow, in a tube of a device of the invention, of a liquid as defined above,
- treatment, during the flow, of the liquid with UV-C radiation of wavelengths between 100 to 280 nm emitted by at least one source of the device.

The flow rate of the liquid can be between 0 and 1000 hL/h, preferably greater than 200 L/h.

Other advantages may still appear to those skilled in the art on reading the examples below, illustrated by the appended figures, given for illustrative purposes.

There represents Dean vortices in a helical tube (1), with internal diameter (di), diameter of the helix (dc) and distance between the turns (b).

There shows a helically shaped FEP tube (1), wound around a source (2) (a UV-C lamp), having a liquid inlet and a liquid outlet as indicated. An enlargement shows the Dean vortices forming in the tube (1) schematically.

Example

Example 1: treatment of a liquid using a device of the invention

• enroulé autour d’un support, consistant en une gaine en quartz de 42 mm de diamètre externe,
  - une source (2), consistant en une lampe UVC à basse pression à amalgame d’une puissance de 45, 75 ou 100W (contenue dans la gaine en quartz), émettant un rayonnement UV-C de longueurs d’onde de 254 nm.

Devices for the microbiological stabilization of a liquid are manufactured, each composed of 1 to 50 identical units, arranged in series or in parallel, each unit comprising:
- a transparent tube (1) made of fluorinated ethylene propylene (FEP), with an internal diameter (di) of between 4 mm and 8 mm, of helical shape, in which the ratio between the internal diameter (di) of the tube (1) and the helical diameter (dc) is between 0.0025 and 0.6,

• wrapped around a support, consisting of a quartz sheath with an external diameter of 42 mm,
  - a source (2), consisting of a low-pressure amalgam UVC lamp with a power of 45, 75 or 100W (contained in the quartz sheath), emitting UV-C radiation with wavelengths of 254 nm .

Each unit further consists of the following: power and control board, pump, tank, flow meter, UV-C lamp chamber, sensors and process control valves.

The commercial UV-C unit delivers light photons to the entire sample volume when pumped (flow rate between 200 and 5000 Lh ^-1 ). The flow rates, the power of the lamps and their number are adjusted for each liquid to be treated. A flow through the tube (1) thanks to the Dean vortex is produced and allows the UV-C light to interact with the liquid. The di/dc ratio has been adjusted to facilitate flow and is between 0.01 and 0.5. The UV-C fluence level can be adjusted for each liquid based on its characteristics and microbial reduction requirements. Treatment levels varying from 100 JL ^-1 to 6000 JL ^-1 of energy were tested in the study. Two temperature sensors monitor the temperature of the air and wine in the UV-C chamber, while two UV-C sensors monitor the incident intensity of UV-C light that is delivered to the processed product. The viscosity of the different liquids was taken into consideration

For each matrix, the driver is optimized to ensure microbiological stabilization while limiting associated pressure losses and energy consumption. The diameter of the tube, the circulation speed, the winding characteristics and the number of lamps are adapted for each type of wine (white, red, rosé and sweet) and must.

Microbiological stabilization tests were carried out in the laboratory and in real conditions (non-sulfited wines and musts with native yeast and bacterial populations). Microbiological stabilization for yeasts (Saccharomyces Cerevisae) in red wines was obtained, in particular with a UV-C dose of 4500-6000 JL ^-1 , with a dose of 500-1000 JL ^-1 for white and rosé wines, and of 2500 JL ^-1 for sweet wines. The UV-C doses necessary for the total inactivation of B.bruxellensis and A.aceti are determined to be 25 and 60% lower than Saccharomyces Cerevisae . The stabilization performances were validated as an alternative to SO ₂ mating of sweet musts and before bottling of finished wines. In addition, chemical and sensory analyzes carried out on the treated wines show no impact on the quality of the wines after two years of storage. Treatments on more than 15 different liquids were carried out and the analyzes showed that the treatment of the invention had no impact from a physicochemical and sensory point of view on the wines.

Claims (10)

Device for the microbiological stabilization of a liquid, comprising:
- a transparent tube (1) with an internal diameter (di) of between 0.2 and 20 mm, of helical shape, in which the ratio between the internal diameter (di) of the tube (1) and the helical diameter (dc) is between 0.0025 and 0.6, and
- at least one source (2) emitting UV-C radiation with wavelengths between 100 and 280 nm. Device according to claim 1, further comprising a support around which the tube (1) is wound. Device according to claim 2, wherein said at least one source (2) is supported or integrated into said support. Device according to any one of the preceding claims, wherein said tube (1) is made of glass, polyethylene (PET) or fluorinated ethylene propylene (FEP). Device according to any one of the preceding claims, further comprising from 1 to 200 units of the at least one source (2), arranged in series or in parallel, and capable of delivering between 50 and 20,000 J/L. Device according to any one of the preceding claims, further comprising means for controlling the flow rate and means for controlling the temperature of the liquid in said device. Use of a device according to any one of claims 1 to 6, for the microbiological stabilization of a liquid, in particular a liquid absorbing UV-C radiation. Use according to claim 7, in which said liquid is chosen from alcoholic beverages, in particular wine and beer, fruit juices and must. Process for microbiological stabilization of a liquid, comprising the following steps:
- flow, in a tube (1) of a device as defined in any one of claims 1 to 6, of a liquid,
- treatment, during the flow, of the liquid with UV-C radiation of wavelengths between 100 to 280 nm emitted by at least one source (2) of a device as defined in any one of the claims 1 to 6. Method according to claim 9, wherein the flow rate is between 0 and 1000 hL/h.