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(11) | EP 1 044 773 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Method to prepare cork for food purposes |
| (57) Method to prepare cork for food purposes comprising a step to condition the bark
or planks of cork, comprising a first stage wherein the planks of cork are boiled
at a limited pH value sufficient to salify the phenols and chlorophenols in order
to solubilize them. |
FIELD OF THE INVENTION
[0001] This invention concerns a method to prepare cork, taken directly from the relative trees, so that it can be used, without any contraindication and with the noxious substances and/or unpleasant taste and/or smell, such as are naturally present, having been eliminated.
[0002] To be more exact, the method allows to obtain corks able to be used in the bottling of wine or other beverages, without the corks giving to the liquid the unpleasant taste known as "corking".
BACKGROUND OF THE INVENTION
[0003] It is well-known that cork is a biological material, with limited natural defences against the attack of moulds and other micro-organisms.
[0004] Cork can therefore contain substances which are harmful or unpleasant to the taste and smell.
[0005] To prepare cork for use for food purposes, for example in the production of corks for bottles, particularly wine bottles, these substances must therefore be eliminated.
[0006] For it is not uncommon, where the cork has not been processed properly, that these substances give the liquid, even wine of the best quality, the bad taste or smell known as "corking".
[0007] With regard to the substances which cause this serious disadvantage, especially for the quality wine industry, various hypotheses have been made so far, and at least the following molecules have been identified: guaiacol (2 methoxyphenol), geosmin, methyl-isoborneol.
[0008] The scientific community does however agree on assigning a fundamental role to chloroanisoles and, in particular, to trichloroanisole.
[0010] As has been confirmed on several occasions by the results of recent research commissioned by the European Community, known as "Project Quercus", the genesis of the defect remains connected to the action of particular moulds on an appropriate substrate.
[0011] The trichloroanisole also functions as a tracing molecule, that is, it measures the activity of unwanted moulds.
[0012] In the framework of another project, financed by the European Community and known as MCI, the measurement of the overall biological activity of the cork was addressed, notwithstanding the capacity of the micro-organisms to produce unwanted molecules, evaluating the capacity of the microbes to reduce the dimethylsulfoxide to dimethylsulfide:
[0013] The results obtained, however, were not satisfactory, because a crucial point in the production of corks was not sufficiently clarified, that is, the boiling of the cork bark or planks and its consequences.
[0014] Boiling is carried out both to extract salts, powders and tannins from the planks of cork, and also to soak the cork so that it becomes plastic and therefore possible to work.
[0015] However, the extraction of the tannins from the cork - which is essential in the preparation of corks for bottles of wine, so that the tannins are not given up to the wine - deprives the bark of its residual natural defences and gives free rein to the multiplication of the moulds which propagate from plank to plank during the drying step, and from pile to pile during the boiling step.
[0016] The present Applicant has studied, designed and perfected the method to prepare cork for food purposes according to the invention in order to overcome these shortcomings and to obtain the advantages shown hereafter.
SUMMARY OF THE INVENTION
[0017] The method to prepare cork for food purposes according to the invention is set forth and characterized in the main claim, while the dependent claims describe other innovative features of the invention.
[0018] The method according to the invention comprises a step of conditioning the cork bark or planks.
[0019] One purpose of the invention is to achieve a method which will make the cork usable for food purposes and in particular in the production of corks, without noxious substances unpleasant to the taste and/or smell.
[0020] To be more exact, the purpose of the method according to the invention is to eliminate or drastically reduce, in a simple and systematic manner, the trichloroanisole contained in the cork.
[0021] If we consider that in wine the normal threshold of perception of trichloroanisole is 4 ppt and that the threshold of certain recognition is about 10 ppt, the purpose of the invention is to take the concentration of trichloroanisole in the cork, after processing, to values near or less than 1 ppb.
[0022] In accordance with this purpose, the method according to the invention provides to introduce a conditioning step comprising a first stage wherein the traditional boiling is replaced by a boiling step with a pH limited to a value sufficient to salify the phenols and the chlorophenols in order to solubilize them. Since the pKa of the chlorophenols is around 4, the pH field operated in is between 5 and 10, advantageously between 7 and 8, with a nitrogen-free and phosphate-free compound, so as not to feed the microorganisms.
[0024] According to another characteristic of the invention, the conditioning step comprises a second stage, subsequent to the first, during which the planks of cork are immersed in an acid solution, at ambient temperature, with the addition of an antiseptic.
[0025] The acid solution may consist for example of citric acid in a quantity sufficient to take the solution to a pH of about 3, while the antiseptic may consist for example of diethylepyrocarbonate
dimethylepyrocarbonate
peracetic acid
or oxygenated water (H2O2).
[0026] Mixable organic solvent, such as for example ethanol (CH3-CH2-OH) may be added to the acid solution.
[0027] According to another characteristic of the invention, each stage of the conditioning step is carried out in an independent tank.
[0028] According to another characteristic feature of the invention, after the conditioning step a drying step is provided during which the planks of cork are surface dried, while they are kept saturated with water inside, in a controlled temperature ambient of less than 10°C; dehumidifiers are included which keep the humidity controlled, for example at around 70%, and the atmosphere is inert, so as to prevent the development of moulds.
[0029] After the drying step, the planks of cork are processed to obtain the finished products, for example the corks themselves; but to be able to work the planks easily they must necessarily retain a certain humidity, which, however, encourages the growth of moulds and an increase in polluting molecules.
[0030] To overcome this shortcoming, according to another characteristic aspect of the invention, a microwave treatment is provided on the final products, under vacuum, to block the growth of moulds and to extract the trichloroanisole.
[0031] These and other characteristics of the invention will become clear from the following description of a preferred form of embodiment, given as a non-restrictive example.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
[0032] A method to prepare cork for food purposes, according to the invention, comprises a step to condition the planks of cork, carried out in two stages, preferably using two independent tanks.
[0033] In the first stage, using a first tank, the planks are boiled in water, to extract the salts, tannins and powders therefrom.
[0034] According to one characteristic of the invention, the planks are boiled with a limited pH of between 5 and 10, advantageously between 7 and 8, with a nitrogen-free and phosphate-free compound, consisting for example of carbonate and bicarbonate of soda.
[0035] The purpose of having this pH during the boiling stage is to take the phenates, precursors of the anisoles, into solution, thus eliminating the final trichloroanisole obtainable.
[0037] In the second stage, immediately after the boiling stage, the planks are immersed in a second tank containing a solution of citric acid, with a pH of about 3, with an antiseptic added, such as diethylpyrocarbonate, dimethylpyrocarbonate, each in a concentration of about 250 ppm, or peracetic acid, in a volume to volume concentration of 0.1%.
[0040] The purpose of this treatment is to keep the surface of the planks blandly acid and eliminate the total microbe load of the surface.
[0041] Using an antiseptic, such as the two indicated above, has the advantage that they act for a few hours without leaving either chemical or organoleptic traces later, given that the speed of hydrolysis of the two compounds with a pH of around 3 is in the region of hours, and the products of hydrolysis are commonly contained in wine and wood.
[0042] Then the surface of the cork planks is dried, in a controlled temperature ambient of less than 10°C, with dehumidifiers which keep the humidity controlled, for example at around 70%, and in an inert atmosphere, so as to prevent the development of moulds.
[0043] Subsequently, especially in the processing of cork for bottle corks, which usually occurs with a humidity rate still suitable to allow the growth of moulds and therefore subject to further pollution, a final step is recommended with a microwave treatment, so as to allow a final chemical-biological cleaning.
1. Method to prepare cork for food purposes, characterized in that it comprises a step
to condition the bark or planks of cork, comprising a first stage wherein the planks
of cork are boiled at a limited pH value sufficient to salify the phenols and chlorophenols
in order to solubilize them.
2. Method as in Claim 1, characterized in that said pH is limited to a value of between
5 and 10.
3. Method as in Claim 1, characterized in that said pH is limited to a value of between
7 and 8.
4. Method as in Claim 1, characterized in that for said boiling stage a nitrogen-free
and phosphate-free compound is used.
5. Method as in Claim 4, characterized in that said compound consists of carbonate and
bicarbonate of soda.
6. Method as in Claim 1, characterized in that the duration of said first stage is at
least one hour.
7. Method as in any claim hereinbefore, characterized in that said conditioning step
comprises a second stage, subsequent to the first, during which the planks of cork
are immersed in an acid solution to which antiseptic has been added.
8. Method as in Claim 7, characterized in that said acid solution is at ambient temperature.
9. Method as in Claim 7, characterized in that said acid solution comprises citric acid.
10. Method as in Claim 9, characterized in that said citric acid is sufficient in quantity
to take the pH of the solution to around 3.
11. Method as in Claim 7, characterized in that said antiseptic comprises diethylpyrocarbonate,
dimethylpyrocarbonate, peracetic acid, or oxygenated water.
12. Method as in Claim 7, characterized in that mixable organic solvent can be added to
said acid solution.
13. Method as in Claim 12, characterized in that said mixable organic solvent consists
of ethanol.
14. Method as in Claim 7, characterized in that the duration of said second stage is around
30 minutes.
15. Method as in Claim 7, characterized in that each of said first and second stages is
carried out in an independent tank.
16. Method as in any claim hereinbefore, characterized in that after said conditioning
step a drying step is provided during which said planks of cork are surface dried
in a controlled temperature ambient of less than 10°C, with dehumidifiers included
which keep the humidity controlled so as to impede the development of moulds.
17. Method as in Claim 16, characterized in that said drying step occurs in an inert atmosphere.
18. Method as in Claim 16, characterized in that said humidity is around 70%.
19. Method as in Claim 16, characterized in that after said drying step a final step is
provided with a microwave treatment under vacuum, so as to allow a final biological-chemical
cleaning.
20. Method as in Claim 19, characterized in that, in the event that said cork is whitened,
a treatment to limit the pH is provided with non-similar products.
21. Method to prepare cork for food purposes, comprising a step of boiling the cork bark
or planks and a step of drying at least the surface of said cork planks, characterized
in that after said drying step a final step is provided with a microwave treatment
under vacuum, so as to allow a final biological-chemical hardening.