METHOD FOR THE MANUFACTURING OF CORKS FOR BOTTLING STILL WINES, AND CORRESPONDING CORKS

Description

technical field

[0001] The invention relates to a method for manufacturing corks, and a cork intended for bottling wine, according to the preamble of claim 11.

[0002] Document FR 600 134 A discloses the following process steps for manufacturing corks intended for bottling still wines: At least one parallelepiped is made, joining, by means of a binder, a plurality of cork strips as well as at least one lateral cork strip on each face of the plurality of cork strips, leaving all the cork strips visible. The polyurethane binder is polymerized by heating and under pressure, then at least one stopper is formed from the polymerized parallelepipeds so that the lateral cork blades are at the ends of the stoppers.

[0003] Document FR 600 134 A discloses A stopper according to the preamble of claim 11. Prior art

[0004] Cork is a natural, waterproof and lightweight material that comes from the bark of certain species of oak trees, such as cork oaks, which are typically found in countries around the Mediterranean, in Europe and North Africa.

[0005] Cork is notably used in the manufacture of stoppers, which serve to seal containers such as bottles containing liquids intended for consumption, particularly still or sparkling wine, spirits, or other beverages. Stoppers are produced either by tubing cork planks or by reconstitution using crushed and sieved cork mixed with polymers.

[0006] Cork is an elastic, resilient, compressible material that is impermeable to liquids and has a high coefficient of friction. Its structure allows for gas permeability, including oxygen exchange, which is beneficial for the maturation of the bottled product. However, the structure of cork stoppers produced from tubing, while highly valued for their aesthetic appeal, varies considerably, resulting in variability in this oxygen transmission.

[0007] Conversely, reconstituted corks produced from crushed cork granules, which are much more structurally homogeneous, have the major aesthetic drawback of deviating from the classic look of so-called "natural" corks inserted directly into the cork block. Finally, although the use of a polyurethane binder has been shown, supported by extensive technical documentation, to be entirely suitable, the complete absence of very low molecular weight oligomers that could migrate into the contents cannot be demonstrated. Consequently, some winemakers are expressing concerns about the increasing use of these reconstituted corks.

[0008] Several documents have been published attempting to address both the aesthetic challenge and the use of cork pieces whose size or appearance prevents the extraction of a natural cork stopper. Each document offers a technical solution for using a portion of the cork, striving to achieve a visual resemblance as close as possible to a traditional natural cork stopper.

[0009] The cork industry has long developed cork stoppers known as 1+1, whose ends are made of cork discs and whose central body is made of agglomerated cork granules. The industry has thus utilized what is called "thin cork," which is the harvested portion of the cork that is not thick enough to be used for lining natural corks. These discs are inserted into the thin cork in the "horizontal" direction, following the cork's thickness, as opposed to the "perpendicular" direction used for lining natural corks. It is worth noting that cork is the outermost layer of bark of a cork oak tree. The bark thickens as the tree grows and contains a series of pits and passages called lenticels for the supply of sap from the central trunk.

[0010] The consequence of using a "horizontal" orientation is that the lenticels, present within the thin cork layer, pass perpendicularly through the disc, creating numerous entry points for oxygen, which can lead to significant variations from one cork to another. These discs also represent potential entry points for oligomers from the binder. In the case of champagne corks, where two discs are overlapped on the side in contact with the wine, the risk of the passage of undesirable volatile compounds is reduced, but not eliminated, by this overlapping.

[0011] One publication thus raised doubts about the physical barrier to the migration of compounds from the binder due to the presence of these lenticels (Mechanism of migration from agglomerated cork stoppers. Part 2: Safety assessment criteria of agglomerated cork stoppers for champagne wine cork producers, for users and for control laboratories, November 2003 Food Additives and Contaminants 20(10):960-71)

[0012] One aim of the invention is to solve a problem identified in the prior art of non-microagglomerated cork stoppers, namely the significant heterogeneity of oxygen transmission from one stopper to another, this variation resulting in differences in wine aging. The goal is therefore to produce stoppers: being visually similar to traditional corks, being homogeneous, allowing control of oxygen passage with a reduced standard deviation from one cork to another avoiding contact of the wine with the polyurethane binder holding together the different parts, and guaranteeing an absence of contamination by anisoles from the cork. Description of the invention

[0013] One object of the invention is a method for manufacturing corks intended for bottling still wines, comprising the following steps: Cork blades and cork lateral blades are made from cork such that any lenticels present in the cork blades extend parallel to the thickness of the blades, while those in the cork lateral blades extend perpendicular to the thickness of the blades. The cork has been previously stripped from the tree and then boiled. At least one parallelepiped is made by joining, using a polyurethane binder, a plurality of cork blades and at least one cork lateral blade on each face of the plurality of cork blades, leaving all the cork blades visible. The polyurethane binder is polymerized by heating and under pressure. Then, at least one stopper is formed from the polymerized parallelepipeds so that the cork lateral blades are at the ends of the stoppers.

[0014] The cork strips and / or the lateral cork strips can be inspected by imaging technique before jointing in order to exclude those with holes, dry veins or yellow spots.

[0015] Between the preparation of the blades and the formation of the parallelepipeds, one can carry out a cleaning of the cork blades and the lateral cork blades with at least one compound chosen from boiling water, steam, a mixture of steam and alcohol, a mixture of steam and carbon dioxide, a mixture of steam and nitrogen, and supercritical carbon dioxide.

[0016] To clean cork blades and cork side blades by exposure to supercritical carbon dioxide, they can be placed in an autoclave capable of reaching a pressure of 100 bar and a temperature of 60°C for at least two hours, or until a residual level of 2,4,6-trichloroanisole is less than 0.3 ng / l.

[0017] During cleaning by exposure to supercritical carbon dioxide, at least one fine mesh cage may include activated carbon and is placed between two cages comprising cork strips and / or cork side strips so as to prevent recontamination.

[0018] The caps can be formed by stamping or machining the parallelepipeds.

[0019] To make a plurality of cork strips, cork strips are glued with a polyurethane binder, then the cork strips are arranged until a predetermined thickness is reached, then the glued cork strips are cut in a normal way to the length of the strips to obtain the plurality of cork strips.

[0020] The polyurethane binder may include thermoexpandable microspheres and / or wax microspheres.

[0021] To produce a plurality of cork strips, one can carry out steps in which: cork strips are glued with a wax emulsion, then the water contained in the wax emulsion is removed by drying, they are glued with a polyurethane binder, then the cork strips are arranged until a predetermined thickness is reached, then the glued cork strips are cut in a normal way to the length of the strips to obtain the plurality of cork strips.

[0022] The predetermined thickness of the plurality of cork strips can be between 6 and 30 strips per cork formed in a parallelepiped.

[0023] A side cork strip may have a different thickness than the cork strips.

[0024] Another object of the invention is a cork for bottling still wines, comprising cork strips joined laterally by a polyurethane binder to form a plurality of cork strips. The cork strips are arranged so that their thickness is perpendicular to the axis of the cork. At least one lateral cork strip is joined by a polyurethane binder to each face of the plurality of cork strips, thus exposing all the cork strips. Any lenticels present in the cork strips extend parallel to the thickness of the strips, while those in the lateral cork strips extend perpendicular to the thickness of the strips. Therefore, all the lenticels of the cork are arranged perpendicular to the axis of the cork, thereby limiting the variation in oxygen permeability from one cork to another encountered in traditional corks. Brief description of the drawings

[0025] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example and made with reference to the accompanying drawings in which: [ Fig 1 ] illustrates the main steps of the manufacturing process according to the invention, [ Fig 2 ] illustrates a plurality of cork strips, [ Fig 3 ] illustrates the parallelepiped resulting from the polymerization, [ Fig 4 ] illustrates the stamping of the polymerized parallelepiped, [ Fig 5 ] illustrates the corks obtained by the manufacturing process, [ Fig 6 ] illustrates the evolution of the partial pressure of oxygen in mg of O2 in the bottles as a function of time elapsed in days for stoppers prepared according to the manufacturing process [ Fig 7 ] illustrates the result of a comparative study between stoppers prepared according to the manufacturing process and natural cork stoppers produced classically. Detailed description

[0026] The manufacturing process according to the invention makes it possible to solve the technical problems identified in the prior art and is illustrated by the figure 1 .

[0027] In a first step 1, cork strips 11 and lateral cork strips 13 are produced from lifted and boiled cork.

[0028] The cork strips 11 have a thickness between 0.8mm and 2mm, and are cut so that any lenticels potentially present in these strips are implanted parallel to the thickness of the strips. The lenticels therefore potentially pass through the strips depending on their thickness.

[0029] Similarly, the lateral cork slats 13 are cut so that any lenticels potentially present in these slats are implanted perpendicular to the thickness of the slats. Therefore, no lenticel penetrates the thickness of these slats.

[0030] As will be seen later in this presentation, the cork strips 11 and the lateral cork strips 13 are assembled into parallelepipeds in which the corks are formed. The lateral cork strips 13 also help to limit contact between the wine and the polyurethane binder used, particularly in the absence of through lenticels.

[0031] In one particular embodiment, the cork strips 11 and / or the lateral cork strips 13 are subjected to imaging inspection, specifically optical observation and / or X-ray imaging, to identify cork strips containing dry veins, holes, or yellow spots. The presence of dry veins can make the affected cork strip brittle under compression. Yellow spots indicate localized cork rot where anisoles are highly concentrated. If not filled with polyurethane binder, the holes can become reservoirs of 2,4,6-trichloroanisole (TCA) or air, altering the permeability of the cork.If these gaps are filled with polyurethane binder, they can contribute to increasing the relative amount of polyurethane compared to the relative amount of cork, so the resulting stopper might not meet ISO 633, which specifies that the relative amount of polymer binder in a stopper must be less than 35% by weight. The affected strips are therefore discarded.

[0032] The lateral cork slats 13 are also chosen for their visual quality according to traditional state-of-the-art techniques.

[0033] In a second step 2, the cork blades 11 and the cork lateral blades 13 are cleaned. This can be done with several compounds, including at least one of the following: boiling water, steam, steam combined with alcohol, steam combined with CO2, steam combined with nitrogen, and supercritical CO2. It should be noted that a compound is said to be in a supercritical state when it is heated to a temperature above its critical temperature and / or to a pressure above its critical pressure. The critical temperature and pressure differ for each compound.

[0034] To clean the cork strips 11 and the cork side strips 13 before joining them, they are placed in stainless steel cages with fine mesh bottoms that allow supercritical CO2 to pass through. The cages are then placed in an autoclave where they are subjected to a pressure of 100 bar and a temperature of 60°C for several hours. For reference, CO2 becomes supercritical above 73.8 bar and 31.1°C.

[0035] Several cages can be stacked one on top of the other, and intermediate cages containing activated carbon can be used to prevent recontamination of the cork with volatile compounds extracted by supercritical CO2 and its co-solvent water towards cages located in the upper levels. Cycle times are defined, according to the initial contamination level, to achieve a residual level of 2,4,6-trichloroanisole (TCA) below 0.3 ng / l.

[0036] In a third step 3, pluralities 12 of cork strips are created by joining the cork strips 11, as illustrated by the figure 2 To join them together, they are glued with a polyurethane binder, possibly mixed with thermo-expandable microspheres or wax. Any method of applying the binder can be used, including with a gluing roller.

[0037] Such thermoexpandable microspheres are described in patent EP 0496687. The microspheres make it possible to reduce any risk of wine migration into the internal structure of the future cork which could weaken its mechanical properties of elasticity.

[0038] The cork strips 11 are arranged until the desired thickness is reached (generally between 6 and 30 strips per cork to be formed). The cork strips 11 are then cut normally across their surface to obtain a plurality 12 of cork strips.

[0039] In one particular embodiment, to reduce the corks' ability to absorb wine upon contact, step 3 begins by spraying a wax emulsion (in particular, natural wax or beeswax) onto the cork strips 11, followed by drying them to remove the water contained in the wax emulsion, notably in an oven. The resulting cork strips 11 are then glued with polyurethane adhesive.

[0040] As in the first embodiment, the cork strips 11 are then arranged until the desired thickness of the plurality 12 of cork strips is reached (generally between 6 and 30 strips per cork to be formed).

[0041] In a fourth step 4, the faces of each plurality 12 of cork strips are glued, revealing all the cork strips 11 in a manner similar to the gluing carried out in the fourth step 4.

[0042] Opposite each of these glued faces, a lateral strip of cork 13, preferably 2 mm thick, is placed to obtain a parallelepiped. figure 3 illustrates such a parallelepiped.

[0043] Therefore, gluing the faces of the 12 cork strips is preferred to gluing the lateral cork strips 13 to ensure that these strips, in contact with the bottle's contents, have not been exposed to the polyurethane binder. The lateral cork strips 13, whose lenticels do not penetrate through the material, thus act as a barrier to any potential migration of compounds from the binder.

[0044] The total height of the parallelepiped is made to correspond to a desired length of the cork which will be pressed into this parallelepiped, so that at the ends of the cork, called mirrors, one can see a surface of unreconstituted cork formed by the lateral strip of cork 13 which has been deposited.

[0045] In a fifth step, the shaped parallelepipeds are placed in a mold where they are compressed at a volume compression ratio of 1.5 to 3 volumes per volume, depending on the initial quality of the cork. The assembly is then heated to a temperature generally between 80 and 120°C for the time necessary to ensure proper polymerization and, if applicable, the desired expansion of the microspheres. Heating can be carried out in an autoclave or a continuous oven.

[0046] In a sixth step, the polymerized parallelepipeds are stamped or machined to obtain caps of the desired diameters. The caps are then machined by a few tenths of a millimeter to achieve a perfect conformation in the marketable format. figure 4illustrates the deep drawing of the polymerized parallelepiped, with shape 14 representing the boundary between the material retained and the material removed during the deep drawing process. figure 5 illustrates the 15 corks obtained.

[0047] Finally, in a seventh step, the resulting caps are washed to remove any machining or stamping residue, and then their quality is checked by optical sorting and weighing. Conforming caps can then be laser-marked or induction-marked and satin-finished.

[0048] These different steps included in step 7 are applied as needed in an order specific to the desired finished product.

[0049] Studies of the evolution of oxygen permeability of the plugs thus produced were carried out by chemiluminescence.

[0050] The equipment used is a Fibox 3 LCD Trace V6 from PreSens Precision Sensing GmbH. The system consists of a transmitter / receiver probe that emits a blue light beam. This beam is directed onto a sensor (also called a pellet) affixed to the inside of a transparent bottle. These sensors are made of fluorescent compounds that absorb the light energy emitted by the probe and then re-emit it as red light. The measurement is based on the fact that the time it takes for this light to re-emit is inversely proportional to the oxygen concentration in the bottle. The result is expressed as the partial pressure of oxygen inside the bottle (PO2).This method offers several advantages: it allows for monitoring the kinetics of oxygen ingress from corking to the end of bottle storage, it is non-destructive, and finally, the measurement is simple to perform and can be carried out under various conditions (temperature, humidity, oxygen pressure gradient) replicating those of a cellar or storage facility. This method is widely used in the industry and has already been the subject of numerous publications for better control of oxygen input before and during bottling (Ugliano et al., 2015).

[0051] The corks under study are first stabilized in a climate chamber for 48 hours at 20°C and 50% relative humidity. The bottles are transparent, with a CETIE ring, the profile of which has been checked for conformity before use.

[0052] Before capping, the bottles were fitted with Pst6 tablets, allowing oxygen pressure measurements up to 41 hPa (41 mbar) with a detection limit of 0.02 hPa. Bottles sealed with natural corks were also fitted with Pst3 tablets, enabling the measurement of much higher oxygen concentrations (up to 500 hPa). All bottles were nitrogen-purged before capping and then vacuum-sealed using a GAI 4040 capping machine, which allowed us to achieve residual oxygen levels below 0.1 mg / bottle (a value subsequently subtracted from the results).

[0053] There figure 6 illustrates the evolution of the partial pressure of oxygen in mg of O2 in the bottles as a function of the time elapsed in days for stoppers prepared according to the manufacturing process described above comprising a stack of about ten 3mm blades and 1.5mm blades at each end.

[0054] Ten bottle caps were measured for this study. They exhibited an average partial pressure of 0.82 mg of O2 after one month with a standard deviation of 0.56.

[0055] There figure 7 The result of a comparative study between batches of stoppers prepared according to the manufacturing process (graph key: Δ) and stoppers made of natural cork produced classically (graph key: ∘) will now be presented.

[0056] Natural cork stoppers produced using an ancestral manufacturing method were chosen for their high-end visual quality, implying a minimum level of surface defects in the stoppers.

[0057] Natural plugs have an average partial pressure of 4.7 mg of O2 after one month with a standard deviation of 10.8.

[0058] The stoppers prepared according to the manufacturing process described above correspond to the stoppers whose permeability measurements are illustrated by the figure 6 and therefore exhibit a partial pressure of 0.82 mg of O2 after one month with a standard deviation of 0.56.

[0059] It thus appears that the partial pressure of O2 after one month for bottles sealed with a cork produced according to the manufacturing process described here is significantly lower than that measured for bottles sealed with a classic solid cork stopper.

[0060] Furthermore, the dispersion of partial pressure of oxygen measurements is much more limited, so the corks produced in this way allow for control of the oxygen allowed, and therefore of the homogeneous aging of the contents from one bottle to another. In contrast, traditional solid cork stoppers expose the contents to very significant variability in oxygen allowed from one bottle to another, leading to considerable disparity in the aging of the same wine in these bottles.

[0061] These tests show that the stoppers produced by the manufacturing process thus effectively solve the state-of-the-art technical problem by exhibiting low average oxygen permeability, while also showing reduced permeability dispersion.

[0062] Furthermore, the manufacturing process ensures the reduction or absence of anisole contamination and avoids contact between the wine and the polyurethane binder both after manufacturing and during the aging of the bottle.

[0063] Finally, the structuring of the stopper with lateral cork strips, possibly chosen by visual inspection or X-ray, ensures a visual appearance during bottling or uncorking close to that of a solid cork stopper.

Claims

1. A method for manufacturing bottle corks for the bottling of still wines, comprising the following steps: - producing cork strips (11) and lateral cork strips (13) from cork such that the lenticels present in the cork strips (11) extend parallel to the thickness of the strips whereas those in the lateral cork strips (13) extend perpendicular to the thickness of the strips, the cork having been previously debarked from the tree then boiled, - producing at least one parallelepiped by joining, via a polyurethane binder, a plurality (12) of cork strips as well as at least one lateral cork strip (13) on each face of the plurality (12) of cork strips revealing the set of cork strips (11), the polyurethane binder being polymerised by heating and under pressure, then - forming at least one bottle cork from the polymerised parallelepipeds, such that the lateral cork strips (13) are located at the ends of the bottle corks.

2. The method for manufacturing bottle corks according to claim 1, wherein the cork strips (11) and / or the lateral cork strips (13) are inspected using imaging technology prior to assembly so as to reject those that have holes, dry veins or yellow stains.

3. The method for manufacturing bottle corks according to any of claims 1 or 2, wherein between producing the strips and forming the parallelepipeds, cleaning of the cork strips (11) and the lateral cork strips (13) is carried out with at least one compound chosen from boiling water, steam, a mixture of steam and alcohol, a mixture of steam and carbon dioxide, a mixture of steam and nitrogen, and supercritical carbon dioxide.

4. The method for manufacturing bottle corks according to claim 3, wherein to clean the cork strips (11) and the lateral cork strips (13) by exposure to supercritical carbon dioxide, they are placed in an autoclave capable of reaching a pressure of 100 bar and a temperature of 60°C either for at least two hours or until a residual content of 2,4,6-trichloroanisole of less than 0.3 ng / l is obtained.

5. The method for manufacturing bottle corks according to any of claims 1 to 4, wherein the bottle corks are formed by stamping or machining the parallelepipeds.

6. The method for manufacturing bottle corks according to any of claims 1 to 5, wherein, to produce a plurality (12) of cork strips, cork strips (11) are glued with a polyurethane binder, then the cork strips (11) are disposed until a predetermined thickness is reached, then the glued cork strips (11) are cut normal to the length of the strips to obtain the plurality (12) of cork strips.

7. The method for manufacturing bottle corks according to claim 6, wherein the polyurethane binder comprises thermoexpandable microspheres and / or wax microspheres.

8. The method for manufacturing bottle corks according to any of claims 1 to 5, wherein, to produce a plurality (12) of cork strips, cork strips (11) are glued with a wax emulsion, then the water comprised in the wax emulsion is removed by drying, they are glued with a polyurethane binder, then the cork strips (11) are disposed until a predetermined thickness is reached, then the glued cork strips (11) are cut normal to the length of the strips to obtain the plurality (12) of cork strips.

9. The method for manufacturing bottle corks according to any of claims 6 to 8, wherein the predetermined thickness of the plurality (12) of cork strips is between 6 and 30 strips per bottle cork formed in a parallelepiped.

10. The method for manufacturing bottle corks according to any of claims 1 to 9, wherein a lateral cork strip (13) has a different thickness from the thickness of the cork strips (11).

11. A bottle cork intended for the bottling of still wines, characterised in that it comprises cork strips (11) joined laterally by a binder so as to form a plurality (12) of cork strips, the cork strips (11) being disposed such that their thickness is perpendicular to the axis of the bottle cork, at least one lateral cork strip (13) joined by a binder to each face of the plurality (12) of cork strips revealing the set of cork strips (11), characterised in that: the binder is a polyurethane binder, the lenticels present in the cork strips (11) extend parallel to the thickness of the strips whereas those in the lateral cork strips (13) extend perpendicular to the thickness of the strips, such that all the cork warts of the bottle cork are disposed perpendicular to the axis of the bottle cork in order to limit the variation of oxygen permeability from one bottle cork to the other.