EP0420999B1 - Process for treating cork stoppers - Google Patents

Abstract

The process disclosed is characterized by a first, cleaning, phase in which the corks are treated, particularly with stirring, at ambient temperature in an aqueous alkaline solution containing a mixture of sodium hydroxide, sodium silicate and hydrogen peroxide, by a second, drying, phase in which the corks are dried at a temperature of the order of 40 - 80 DEG C and by a third, disinfection, phase in which the corks are treated with an aqueous acidic solution containing a mixture of acetic and peracetic acid plus hydrogen peroxide in equilibrium, this third phase being followed by a further drying phase.

Description

The present invention relates to a method for treating cork stoppers.

The "cork taste" problem, well known to oenologists and bottlers, causes losses each year that can amount to more than 1% of the total wine production, which is significant.

This term "cork taste" means all taste errors of the wine, which can be of different origins. However, it was found that these problems were often due to the washing of the cork with chlorine-containing products on the one hand, and to the presence or formation of microorganisms in the cork material that were either already present in the cork or during the other later treatment phases occurred.

In order to eliminate the adverse influence of the microbial flora in the cork on the drink, especially on bottled wine, it has become common practice to subject the cork to disinfection before use; this traditionally consists in immersing the cork in a sodium hypochlorite solution. This treatment usually takes place directly at the manufacturer.

The above treatment allows for a satisfactory disinfection of the cork, considering the bactericidal and spore-killing spectrum of activity known from hypochlorites, but it has been shown that this resulted in the release of chlorine in the presence of those present in the cork Polyphenols and / or tannins led to the release of such compounds as trichloroanisole, wherein certain Experts see the essential factor responsible for the "cork taste".

For this reason, attempts have been made to replace the hypochlorites with other disinfectants with a similar effect, but non-toxic, which can be used for the treatment of the cork intended for bottling.

In parallel to the aforementioned problems, the industry wants to have corks that look as pleasant as possible and that are in any case stain-free; For this reason, the suppliers have made it a habit to decolorize the cork, which may then be recolored in accordance with the customs customary in each region. In view of the well-known decolorization properties of sodium hypochlorite, this treatment is currently taking place simultaneously with the disinfection.

These constraints make it very clear that in order to be able to replace sodium hypochlorite in the treatment of corks, a non-toxic product must be selected which not only has a very broad microbicidal spectrum, but also intensive oxidation properties in order to achieve the desired bleaching.

Of the products examined, only the use of hydrogen peroxide or peracetic acid was considered; However, the treatment methods proposed to date have not been satisfactory mainly because of the unpleasant appearance of the cork thus produced, and the classic hypochlorite method is therefore still largely in use today.

Incidentally, in order to improve the appearance of the cork offered to the industry, one had got used to the cork treated with sodium hypochlorite Allow oxalic acid based solution to run through; The main function of this treatment was to remove the stains on the surface of the cork (brick-red stains with high tannin and iron content) and thus improve the appearance of the cork.

However, such a treatment can no longer be used because oxalic acid is now classified among the toxic substances.

As a result, it is imperative to create a method for treating the cork which, due to its nature, can take the place of hypochlorites on the one hand and oxalic acid treatment on the other.

For this purpose, it has of course been considered to precede the bleaching and disinfection treatment with a surface delignification and to use an alkaline reagent for this purpose, in particular soda, which is a known lignin solvent, which has been used for many decades, particularly in the context of paper production. However, the tests that have been carried out for this purpose have not been satisfactory.

The present invention has the purpose of eliminating the aforementioned difficulties by proposing a method for treating cork stoppers without hypochlorite, whereby the formation of anisole compounds can be avoided and at the same time an almost complete destruction of all microbial germs takes place, so that products are obtained which cannot develop a "cork taste", and which due to their nature simultaneously bleach the cork and suppress brown spots on the Prevent surface and create a fine, even and handsome surface structure.

EP-A-0 322 650 relates to a process for bleaching and sterilizing cork articles, which comprises only two treatment stages. In the first stage of the process, the cork articles are treated with an aqueous alkaline hydrogen peroxide solution which preferably contains 30 to 150 g / l hydrogen peroxide, 2 to 20 g / l sodium hydroxide and 2 to 50 g / l sodium silicate. It follows immediately, i. H. without any intermediate rinsing with water, a drying stage in which the cork articles are exposed to UV radiation. The cork articles treated in this way, in particular cork stoppers, have an improved degree of bleaching compared to a conventional hydrogen peroxide treatment.

FR-A-2 569 369 describes a multi-stage process for sterilizing and bleaching cork stoppers. Here, the cork stoppers are also treated in the first process stage with an aqueous alkaline hydrogen peroxide solution which contains 4 to 15% by weight of hydrogen peroxide and preferably sodium hydroxide as the alkaline substance and sodium or potassium silicate as the stabilizer. The cork stoppers are then washed with water. In the third stage of the process, the cork stoppers are treated with an aqueous solution of an acidic substance which has a pH in the range from 0 to 4. Preferred acidic substances are: Al₂ (SO₄) ₃, NaHSO₄, KHSO₄, sodium or potassium metabisulfite, H₂SO₄, SO₂ or citric acid. Finally, the cork stoppers treated in this way are dried.

Finally, DE-A-25 36 617 relates to storage-stable concentrates for the production and supplementation of functional agents based on aliphatic monopercarboxylic acids. These concentrates have a content of 0.5 to 20 wt .-% peracid with 2 to 3 carbon atoms and / or corresponding aliphatic monocarboxylic acid, 25 to 40 wt .-% H₂O₂ and water. Preference is given to concentrates which contain 5 to 10% by weight of peracetic acid and / or acetic acid and a molar excess of H₂O₂ in a ratio of at least 2: 1. Such concentrates can easily be diluted to the application concentrations of 0.1 to 1% customary in food technology and in the medical sector.

• a) in einer ersten Phase oder Reinigungsphase insbesondere unter Umrühren die Korke bei Umgebungstemperatur in einer alkalischen, wäßrigen Lösung behandelt, die eine Mischung aus Natriumhydroxid, Natriumsilicat und Wasserstoffperoxid enthält,

welches dadurch gekennzeichnet ist, daß man

• b) in einer zweiten Phase oder Ruhepause die Korke bei einer Temperatur im Bereich von 40 bis 80 °C trocknet, anschließend spült und
• c) in einer dritten Phase oder Desinfektionsphase die Korke mittels einer im Gleichgewicht befindlichen sauren, wäßrigen Lösung behandelt, die eine Mischung aus Essig- und Peressigsäure sowie Wasserstoffperoxid enthält,
• d) wobei auf diese dritte Phase eine abschließende Trocknungsphase folgt.

In contrast, the present invention relates to a method for cleaning and disinfecting cork stoppers, wherein

• a) in a first phase or cleaning phase, in particular with stirring, the cork at ambient temperature in an alkaline, aqueous solution treated, which contains a mixture of sodium hydroxide, sodium silicate and hydrogen peroxide,

which is characterized in that one

• b) in a second phase or rest the cork dries at a temperature in the range of 40 to 80 ° C, then rinses and
• c) in a third phase or disinfection phase, the cork is treated with an acidic, aqueous solution which is in equilibrium and contains a mixture of acetic and peracetic acid and hydrogen peroxide,
• d) a final drying phase follows this third phase.

According to another feature of the invention, the third phase is applied at a temperature between 10 and 60 ° C.

When using the first phase of this procedure, the simultaneous treatment with the three components is essential: in fact there is a synergism between the action of the sodium hydroxide solution, which dissolves the lignin superficially and thus eliminates the aesthetic defects of the cork, and the simultaneous action of Sodium silicate and hydrogen peroxide; otherwise there is the possibility of varying the degree of bleaching of the cork as required, but also the properties of the cork material used, by influencing the NaOH / Na₂SiO₃ ratio.

The resting phase following this cleaning phase is also of great importance, and for two reasons in particular: In fact, the rise in temperature on the one hand activates the hydrogen peroxide, which initiates the disinfection the cork permits and, on the other hand, favors the degradation of the sodium silicate in the form of silicon oxide to support the decolorization of the cork and to bring about a surface structure which is similar to that of velor with a particularly pleasant handle.

As already mentioned, the relative proportions of the different components of the cleaning solution can change according to the desired degree of bleaching; However, it has been shown that particularly satisfactory results are achieved by using a solution which, expressed in a percentage by weight analysis, contains approximately 1 to 5% by weight sodium hydroxide (50%), 2 to 10% by weight sodium silicate (50%) and 15 to 25 wt .-% hydrogen peroxide (35%) contains.

For the last-mentioned component, one can use, for example, the compound which is sold commercially under the name "P3-OXONIA" (registered trademark).

Experience has shown, moreover, that the contact time between the cork and the cleaning solution with stirring must be of the order of 30 minutes and that this treatment must also take 30 minutes to rest at 80 ° C.

In addition, the particular choice of disinfectant for the third phase of the application of the method according to the invention is also of essential importance. In fact, experience to a large extent has shown that, under acceptable working conditions (temperature and concentration), the hydrogen peroxide alone was not capable of sufficiently destroying all microbial germs, whereas peracetic acid, due to its instability and its ability to release oxygen, is not used alone in unstabilized solution could.

For this reason, the aqueous disinfectant solution according to a preferred embodiment of the invention contains a weight analysis percentage of about 2 to 5% of an acidic, aqueous solution in equilibrium of a mixture of acetic and peracetic acid and hydrogen peroxide, which corresponds to the commercially available solution with the designation "P3 -OXONIA ACTIF "(registered trademark).

So that this solution can be used with the highest possible efficiency, it is of course essential to remove any trace of alkalinity from the cork after the cleaning treatment and therefore to rinse it for several minutes before using the disinfectant solution.

In order to achieve a maximum disinfectant effect, it was observed that the cork had to be brought into contact with the disinfectant solution for a period of about 15 to 30 minutes and at a temperature not exceeding 40 ° C.

This process may be followed by a coloration before the cork is dried in one or two stages at 80 ° C for about 30 minutes to 1 hour. These are then ready for use in bottling wines and other drinks.

The method described above can of course be used in any type of device without going beyond the scope of the invention. However, stainless steel containers are preferably chosen for the aqueous cleaning solution and for the aqueous disinfection solution in order to limit corrosion problems as much as possible.

Furthermore, in order to suppress "flying yeast" and to exclude their presence in the wine, it is particularly advantageous to insert the cork to be treated (generally in groups of 10 to 20,000 pieces) into cylindrical grid drums for horizontal rotation, before being brought into contact with the different treatment solutions one after the other; the use of such a device also allows the contact between the corks and the various solutions to be improved and strengthened.

The characteristic features of the method which is the subject of the invention are described in detail below with reference to the above application example:
A batch of 15,000 corks has been placed in a cylindrical lattice drum.

• 1,2 % 50 %ige Natronlauge,
• 19 % "P3-OXONIA" (eingetragenes Warenzeichen)
  (Wasserstoffperoxid 35 %ig,
• 2 % 50 %iges Natriummetasilikat.

These corks were immersed and rotated for 30 minutes at ambient temperature in a solution containing the following weight analysis percentages:

• 1.2% 50% sodium hydroxide solution,
• 19% "P3-OXONIA" (registered trademark)
  (35% hydrogen peroxide,
• 2% 50% sodium metasilicate.

The cork was then allowed to drain for 2 minutes, after which it was dried at 80 ° C for 30 minutes. Then they were rinsed for 2 minutes.

The drum was then rotated again and the cork was soaked for 15 minutes at ambient temperature in a 3% solution of "P3-OXONIA ACTIF" (registered trademark). This treatment was followed by a pre-drying at 80 ° C for 20 minutes and then a drying process at 80 ° C for 40 minutes.

In this way, cork was obtained, the appearance of which was completely satisfactory.

Claims (9)

1. A process for cleaning and disinfecting corks in which

   a) in a first phase or cleaning phase carried out in particular with stirring, the cork is treated at ambient temperature in an alkaline aqueous solution containing a mixture of sodium hydroxide, sodium silicate and hydrogen peroxide,

   characterized in that

   b) in a second phase or rest interval, the cork is dried at a temperature of 40 to 80°C and subsequently rinsed and

   c) in a third phase or disinfection phase, the cork is treated with an acidic aqueous equilibrium solution containing a mixture of acetic and peracetic acid and also hydrogen peroxide,

   d) this third phase being followed by a concluding drying phase.
2. A process as claimed in claim 1, characterized in that the third phase is carried out at a temperature of 10 to 60°C.
3. A process as claimed in claim 1 or 2, characterized in that the aqueous cleaning solution contains a gravimetric-analytical percentage of 1 to 5% by weight of 50% sodium hydroxide, 2 to 10% by weight of 50% sodium silicate and 15 to 25% by weight of 35% hydrogen peroxide.
4. A process as claimed in any of claims 1 to 3, characterized in that the cork is contacted with the aqueous cleaning solution for about 30 minutes with stirring.
5. A process as claimed in any of claims 1 to 4, characterized in that the cork is dried for about 30 minutes before the disinfection phase.
6. A process as claimed in any of claims 1 to 5, characterized in that the aqueous disinfecting solution contains a gravimetric-analytical percentage of about 2 to 5% of an acidic aqueous equilibrium solution of a mixture of acetic and peracetic acid and also hydrogen peroxide.
7. A process as claimed in any of claims 1 to 6, characterized in that the cork is contacted with the aqueous disinfecting solution for about 15 to 30 minutes with stirring.
8. A process as claimed in any of claims 1 to 7, characterized in that the aqueous cleaning solution and the aqueous disinfecting solution are introduced into stainless steel vessels.
9. A process as claimed in any of claims 1 to 8, characterized in that the cork to be treated is placed in horizontally rotating cylindrical wire drums and successively contacted with various treatment solutions.