PROCESS FOR THE ABATEMENT OF UNDESIRED VOLATILE COMPOUNDS FROM MANUFACTURED AND SEMI-MANUFACTURED CORK PRODUCTS

DESCRIPTION

FIELD OF THE INVENTION

The present invention relates to a process for the abatement of undesired volatile compounds from manufactured and semi-manufactured cork products. In particular, said process is highly reproducible and economically advantageous, as well as enabling a practically quantitative reduction of said undesired volatile compounds.

STATE OF THE ART

Starting from its gathering and during all the stages of storage and processing thereof, cork may be exposed to contamination by molecules mainly deriving from the metabolism of micro-organisms that can proliferate on the cork itself. Most of these molecules is organoleptically active, and hence their presence is particularly undesirable since it implies one of the main factors of risk in the employ of cork products used for closing bottles and for conservation of wines, as explained hereinafter.

In the scientific literature of the field, all the studies identify as main cause of the defect known as "taste of cork" the compound 2,4,6-trichloroanisole (TCA), which is hence commonly used as indicator of the state of organoleptic cleanliness of the cork. Other compounds of the same family, i.e. chloroanisoles or chlorophenols, can contribute to the organoleptic deviation of wines, as likewise other compounds, such as guaiacol, geosmin, 2-methyl isoborneol, 1-octen-3-one, and

1-octen-3-ol. However, TCA, either owing to its very low level of organoleptic perceptibility (1-10 ng/L) or owing to the relative easiness with which it can be analytically detected, is considered as reference compound and for this reason investigated as indicator of organoleptic cleanliness in this context.

From the European patent No. 1444075, a process is known for the extraction, from gaseous phase, of organoleptic contaminants, such as TCA, present in cork caps, wherein a gaseous mixture is used comprising steam and vapour of organic solvent, preferably ethanol, in the presence of air. In the discussion of the known art of this patent, it is indeed reported that all the processes that involve the extraction from liquid phase have proven to be unsatisfactory in removing said undesired compounds. In the examples provided, the corks treated according to the patent are subsequently immersed in wine for 24 hours and then subjected to olfactive evaluation by three expert persons. There is deduced a large reduction of

TCA, even though the olfactive evaluation referred to is actually entrusted to the qualitative perceptive capacity alone of said experts.

Since said compounds are extremely undesirable in so far as they compromise the use of cork, it is still felt the need to reduce these compounds in an effective, quantitative, and advantageous way under the economic standpoint as well as the standpoint of implementation.

It is therefore an object of the present invention to provide a process that will enable the abatement of said undesired compounds, while overcoming the disadvantages of the known art.

SUMMARY

The above object has been achieved by a process for the abatement of volatile compounds present in manufactured or semi-manufactured cork products comprising the following steps: a) introducing manufactured or semi-manufactured cork products into a suitable container; b) subjecting the manufactured or semi-manufactured cork products to at least one cycle of water absorption at a temperature of 30 ⁰ C to 90 ⁰ C for a time not higher than 180 minutes; c) taking said manufactured or semi-manufactured cork products of step b) out of said container and subjecting them to at least one conditioning step not exceeding 10 days until a percentage of minimum internal humidity not lower than 20% is achieved; and d) introducing the manufactured or semi-manufactured cork products of step c) into a drum and subjecting them to at least one cycle of a first thermal treatment whilst said drum turns at a speed of 2 to 30 rpm, wherein d1) an aqueous solution comprising 10% to 40% of H ₂ O ₂ (130 v/v) and up to 5% of at least one basic compound is sprayed on said manufactured or semi-manufactured cork products of step c); and subsequently d2) air is flown for a period of 90 to 210 minutes, being progressively heated from an initial temperature of at least 50°C up to a final temperature of at most 160 ⁰ C.

The term "volatile compounds" according to the present invention is meant to include all those volatile compounds that can contribute to the organoleptic deviation of wines, such as chloroanisoles, amongst which TCA, chlorophenols and other compounds, such as guaiacol, geosmin, 2-methyl isobomeol, 1-octen-3- one, 1-octen-3-ol.

In the present invention, by "manufactured or semi-manufactured cork products" are meant granulated cork (openings of 1 to 30 mm, volume of granule 0.5 — 14,000 mm ³ ), cylinders of natural cork, multipiece and/or agglomerate (diameter 16-60 mm, height 22-80 mm), natural horizontal- or vertical-pored cork rounds or multipiece rounds (diameter 16-60 mm, height 3-22 mm), and any other cork piece that, irrespective of the geometry, has a volume not exceeding 250,000 mm ³ and has no dimensions less than 3 mm.

The term "basic compound" according to the present invention, is meant to include any organic or inorganic compound that in aqueous solution has a basic pH and that is chemically and organoleptically inert towards cork and its components, in no way adversely affecting the organic tissue nor altering to a significant extent the chemical-physical properties of the same.

According to the preferred embodiment, said process further comprises a step e) wherein the manufactured or semi-manufactured cork products of step d) are subjected to at least one cycle of a second thermal treatment in the drum, which turns at a speed of 1 to 15 rpm, wherein e1) an aqueous solution comprising 5% to 20% of H ₂ O ₂ (130 v/v) and up to 3% of at least one basic compound is sprayed on said manufactured or semi-manufactured cork products of step d); and subsequently e2) air is flown for a period of 130 to 190 minutes, being progressively heated from an initial temperature of at least 30 ⁰ C up to a final temperature of at most 150°C. As will be evident from the following detailed description, the selected combination of the above steps allows the abatement of these compounds in an effective, quantitative, and advantageous way under the economic standpoint as well as the standpoint of implementation. DESCRIPTION OF THE FIGURES

The characteristics and advantages of the present invention will be evident from the following detailed description, from the implementing examples, which are provided for illustrative non-limiting purposes, and with reference to the annexed figures, wherein:

Figure 1 shows the content of TCA in cork caps both before and after implementation of the process according to the present invention and the process according to the preferred embodiment of the present invention as per Example 1 ;

Figure 2 shows the content of TCA in cork caps both before and after implementation of the process according to the present invention and the process according to the preferred embodiment of the present invention as per Example 2;

Figure 3 shows the content of TCA in cork caps both before and after implementation of the process according to the present invention and the process according to the preferred embodiment of the present invention as per Example 3;

Figure 4 shows the content of TCA in vertical-pored cork rounds both before and after implementation of the process according to the present invention as per Example 4;

Figure 5 shows the content of TCA in horizontal-pore cork rounds both before and after implementation of the process according to the present invention as per Example 5; and

Figure 6 shows the content of TCA in cork granulates of various average grain sizes both before and after implementation of the process according to the present invention as per Example 6. DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a process for the abatement of volatile compounds present in manufactured or semi-manufactured cork products comprising the following steps: a) introducing manufactured or semi-manufactured cork products into a suitable container; b) subjecting the manufactured or semi-manufactured cork products to at least one cycle of water absorption at a temperature of 30 ⁰ C to 90 ⁰ C for a time not higher than 180 minutes; c) taking said manufactured or semi-manufactured cork products of step b) out of said container and subjecting them to at least one conditioning step not exceeding 10 days until a percentage of minimum internal humidity not lower than 20% is achieved; and d) introducing the manufactured or semi-manufactured cork products of step c) into a drum and subjecting them to at least one cycle of a first thermal treatment whilst said drum turns at a speed of 2 to 30 rpm, wherein d1) an aqueous solution comprising 10% to 40% of H ₂ O ₂ (130 v/v) and up to 5% of at least one basic compound is sprayed on said manufactured or semi-manufactured cork products of step c); and subsequently d2) air is flown for a period of 90 to 210 minutes, being progressively heated from an initial temperature of at least 50°C up to a final temperature of at most 160°C.

The process according to the present invention is implemented discontinuously; consequently in step a) discrete amounts of manufactured or semi-manufactured cork products are provided.

In step b), said manufactured or semi-manufactured cork products are subjected to at least one cycle of absorption of water at a temperature of 30 ⁰ C to 90 ⁰ C for a time not higher than 180 minutes.

Preferably, the water used for step b) is changed after 2 to 6 cycles.

In step c) said manufactured or semi-manufactured cork products of step b) are taken out of the container and subjected to at least one conditioning step not exceeding 10 days until a percentage of minimum internal humidity not lower than

20% is achieved.

In step d) the manufactured or semi-manufactured cork products of step c) are introduced into a drum and subjected to at least one cycle of a first thermal treatment whilst said drum turns at a speed of 2 to 30 rpm, wherein d1) an aqueous solution comprising 10% to 40% of H ₂ O ₂ (130 v/v) and up to 5% of at least one basic compound is sprayed on said manufactured or semi-manufactured cork products of step c); and subsequently d2) air is flown for a period of 90 to 210 minutes, being progressively heated from an initial temperature of at least 50°C up to a final temperature of at most 160 ⁰ C.

In fact, in step d1), while the drum is turning, the manufactured or semimanufactured cork products are moved in such a way as to be uniformly exposed to spraying of the solution. Next, in step d2), once spraying has terminated, hot air is flown within the rotating drum so as to uniformly dry the manufactured or semimanufactured cork products. Said air is progressively heated so as to increase the temperature from a minimum of 50°C to a maximum of 160 ⁰ C in the interval of time indicated.

In step d), said drum turns at a speed of 2 to 30 rpm. Preferably, the speed of rotation of the drum in step d1) is different from the speed of rotation in step d2). More preferably, the speed of rotation of the drum in step d1) is higher than the speed of rotation in step d2).

Suitable basic compounds for the purposes of the present invention are inorganic salts, such as NH ₄ HCO ₃ , hydroxides, such as NaOH, or e!se ammonia. Said compounds associate to the disinfectant effect of H ₂ O ₂ , advantageously also an effect of bleaching of the manufactured or semi-manufactured cork products to be treated.

In order to eliminate the gaseous efflux, the drum is equipped with a suction device that enables a change of air of 300 and 1000 times the volume of the drum itself per hour.

Preferably, step d1) is repeated 1 to 5 times. This enables an even more significant abatement of TCA to be obtained, as will be clearly evident from the examples provided below.

Preferably, said drum turns at a speed of 5 to 20 rpm. Even though the choice of the speed of rotation depends on the dimensions of the manufactured or semimanufactured cork products to be treated, it has, however, been observed that said range enables movement thereof in an optima! way, while guaranteeing a time of exposure to spraying that is particularly suitable for the purposes of the present invention.

According to the most preferred embodiment, the process according to the present invention further comprises a step e), wherein the manufactured or semimanufactured cork products of step d) are subjected to at least one cycle of a second thermal treatment in the drum, which turns at a speed of 1 to 15 rpm, wherein e1) an aqueous solution comprising 5% to 20% of H ₂ O2 (130 v/v) and up to 3% of at least one basic compound is sprayed on said manufactured or semi-manufactured cork products of step d); and subsequently e2) air is flown for a period of 130 to 190 minutes, being progressively heated from an initial temperature of at least 30 ⁰ C up to a final temperature of at most 150 ⁰ C.

In fact, after step d), the manufactured or semi-manufactured cork products are subjected to dimensional rectification, i.e. the final shape is given thereto, and subsequently the products are further subjected to step e).

In step e1), whilst the drum turns, the manufactured or semi-manufactured cork products are moved in such a way as to be uniformly exposed to spraying of the solution. Next, in step e2), once spraying has terminated, hot air is flown within the rotating drum so as to uniformly dry the manufactured or semi-manufactured cork products. Said air is progressively heated so as to increase the temperature from a minimum of 30 ⁰ C up to a maximum of 150 ⁰ C in the range of time indicated. In step e), said drum turns at a speed of 1 to 15 rpm. Preferably, the speed of rotation of the drum in step e1) is different from the speed of rotation of step e2). More preferably, the speed of rotation of the drum in step e1) is higher than the speed of rotation of step e2).

Preferably, step e1) is repeated 1 to 3 times. This enables an even more quantitative abatement of TCA to be obtained than in step d) alone, in effect a practically total abatement, as will be clearly evident from the examples provided below. Preferably, said drum turns at a speed of 5 to 10 rpm. Even though the choice of the speed of rotation depends on the dimensions of the manufactured or semimanufactured cork products to be treated, it has, however, been observed that said range enables movement thereof in an optimal way, while guaranteeing a time of exposure to spraying that is particularly suitable for the purposes of the present invention.

In a further aspect, the present invention concerns manufactured or semimanufactured cork products that can be obtained by the process according to what above described and comprise a residue of volatile compounds quantifiable as an average yieldable residue of 2,4,6-trichloroanisol not higher than 0.5 ng/L. It has thus advantageously and surprisingly been possible to obtain manufactured or semi-manufactured cork products wherein the average yieldable TCA is in an amount less than the minimum of the threshold of organoleptic perceptibility. According to the purposes of the present invention, the expression "average yieldable residue" is meant to be the quantity of yieldable TCA obtained from the average of the individual values of the pieces analysed by carrying out a sampling for the purposes of testing by attributes according to the level of quality acceptable for a batch-to-batch test, as expressly defined, for example, in ISO 2859-1 :1999 (former Military Standard 105E).

The process according to the present invention thus enables a reduction of these compounds in an effective, quantitative, and advantageous way under the economic standpoint as well as the standpoint of implementation. Furthermore, the process according to the present invention uses water as the only treatment solvent wherein H2O2 and a basic compound are present and does not require any variation of pressure for favouring extraction of the undesired compounds, consequently advantageously enabling a significant energy saving to be achieved, as well as a considerable simplification in terms of implementation and equipment required. Furthermore, it should be pointed out that the surprising results obtained show that the process according to the invention in effect overcomes the technical prejudice expressed in the prior art document No. EP 1444075 mentioned above, which states that all the processes that envisage liquid-phase extraction have proven unsatisfactory in removing said undesired compounds. Examples of the present invention are herein below provided for illustrative non- limiting purposes, wherein the tests for evaluation of the content of TCA have been carried out according to the standard ISO 20752:2007.

EXAMPLES

Example 1

Process according to the invention used for the treatment of cork caps

A batch of approximately 40,000 cork caps was introduced into a tank of suitable dimensions to be subjected to the process according to the present invention.

Said batch was subjected to a first step of absorption of water at a temperature of

80 ⁰ C for approximately 180 minutes. The cork caps were then taken out of the tank and conditioned for 9 days, during which the humidity outside and inside them was monitored and was found on average to be as follows:

The cork caps were then introduced into a drum, which was then made to turn at

21 rpm, whilst sprayed on the cork caps was a solution comprising 26.4 L of water,

2.76 L of H ₂ O ₂ (130 v/v), and 5.24 L of NH ₄ HCO ₃ (10% aq. sol.). In this way, a homogeneous spraying was obtained on aii the cork caps being treated. The spray cycle was repeated a further two times.

The cork caps were then subjected to a first thermal treatment from a temperature of 50°C to a temperature of 140 ⁰ C in a time range of 205 minutes, through a hot air flow within the rotating drum at 3 rpm, and a suction of the gaseous effluents.

After a step of dimensional rectification, the cork caps were re-introduced into the drum.

Subsequently, the drum was made to turn at 15 rpm and on the cork caps thus treated a solution comprising 26.4 L of water and 2.76 L of H ₂ O ₂ (130 v/v) was sprayed.

The cork caps were then subjected to a second thermal treatment from a temperature of 50 ⁰ C to a temperature of 120 ⁰ C in a time range of 160 minutes, through a hot air flow within the rotating drum at 3 rpm, and a suction of the gaseous effluents.

For the cork caps treated according to the present example, the abatement of TCA was evaluated by comparing the starting content of TCA, measuring the content of

TCA after the first thermal treatment and, finally, at the end also of the second thermal treatment. The results of said evaluations are given in Figure 1 , where the

50 contaminated cork caps of the statistical sample each revealed a significant reduction of TCA already after the first thermal treatment, whilst after the second, in numerous cases, there was surprisingly observed a practically total abatement of said substance.

Example 2

Process according to the invention used for the treatment of cork caps

A batch of approximately 20,000 cork caps was introduced into a tank of suitable dimensions to be subjected to the process according to the present invention.

Said batch was subjected to a first step of absorption of water at a temperature of

80 ⁰ C for approximately 150 minutes. The cork caps were then taken out of the tank and conditioned for 9 days, during which the humidity outside and inside them was monitored and was found on average to be as follows:

The cork caps were then introduced into a drum, which was then made to turn at

15 rpm, whilst sprayed on the cork caps was a solution comprising 13.2 L of water and 1.38 L of H ₂ O ₂ (130 v/v). In this way, a homogeneous spraying was obtained on all the cork caps being treated.

The cork caps were then subjected to a first thermal treatment from a temperature of 50 ⁰ C to a temperature of 120 ⁰ C in a time range of 160 minutes, through a hot air flow within the rotating drum at 4 rpm, and a suction of the gaseous effluents.

After a step of dimensional rectification, the cork caps were re-introduced into the drum.

Subsequently, the drum was made to turn at 15 rpm, and on the cork caps thus treated a solution comprising 13.2 L of water, 1.38 L of H ₂ O ₂ (130 v/v), and 2.10 L of NH ₄ HCO ₃ (10% aq. sol.) was sprayed.

The cork caps were then subjected to a second thermal treatment from a temperature of 40 ⁰ C to a temperature of 140 ⁰ C in a time range of 180 minutes, through a hot air flow within the rotating drum at 4 rpm, and a suction of the gaseous effluents.

For the cork caps treated according to the present example, the abatement of TCA was evaluated by comparing the starting content of TCA, measuring the content of

TCA after the first thermal treatment and, finally, at the end also of the second thermal treatment. The results of said evaluations are given in Figure 2, where the

20 contaminated cork caps of the statistical sample each revealed a significant reduction of TCA already after the first thermal treatment, whilst after the second, in numerous cases, there was surprisingly observed a practically total abatement of said substance.

Example 3

Process according to the invention used for the treatment of cork caps

A batch of approximately 35,000 cork caps was introduced into a tank of suitable dimensions to be subjected to the process according to the present invention.

Said batch was subjected to a first step of absorption of water at a temperature of

80 ⁰ C for approximately 120 minutes. The cork caps were then taken out of the tank and conditioned for 9 days, during which the humidity outside and inside them was monitored and was found on average to be as follows:

The drum was then made to turn at 3 rpm, whilst sprayed on the cork caps was a solution comprising 23.1 L of water, 2.42 L of H ₂ O ₂ (130 v/v), and 4.58 L of NH ₄ HCO ₃ (10% aq. sol.). In this way, a homogeneous spraying was obtained on all the cork caps being treated. The spray cycle was then repeated a second time. The cork caps were then subjected to a first thermal treatment from a temperature of 50°C to a temperature of 14O ⁰ C in a time range of 205 minutes, through a hot air flow within the rotating drum at 2 rpm, and a suction of the gaseous effluents.

After a step of dimensional rectification, the cork caps were re-introduced into the drum.

Subsequently, the drum was made to turn at 12 rpm, and on the cork caps thus treated a solution comprising 23.1 L of water, 2.42 L of H ₂ O ₂ (130 v/v), and 3.68 L of NH ₄ HCO ₃ (10% aq. sol.) was sprayed.

The cork caps were then subjected to a second thermal treatment from a temperature of 40 ⁰ C to a temperature of 140 ⁰ C in a time range of 180 minutes, through a hot air flow within the rotating drum at 2 rpm, and a suction of the gaseous effluents.

For the corks treated according to the present example, the abatement of TCA was evaluated by comparing the starting content of TCA, measuring the content of

TCA after the first thermal treatment, and, finally, at the end also of the second thermal treatment. The results of said evaluations are given in Figure 3, where the

27 contaminated cork caps of the statistical sample each revealed a significant reduction of TCA already after the first thermal treatment, whilst after the second, in numerous cases, there was surprisingly observed a practically total abatement of said substance.

Example 4

Process according to the invention used for the treatment of cork rounds

A batch of approximately 200,000 vertical-pored cork rounds was introduced into a tank of suitable dimensions to be subjected to the process according to the present invention.

Said batch was subjected to a first step of absorption of water at a temperature of

65°C for approximately 70 minutes. The rounds were then taken out of the tank and conditioned for 5 days, during which the humidity therein was monitored and was found on average to be as follows:

The cork rounds were then introduced into a drum, which was then made to turn at

24 rpm, whilst on the cork rounds a solution comprising 13.2 L of water, 2.8 L of

H ₂ O ₂ (130 v/v), and 5.2 L of NH ₄ HCO ₃ (10% aq. sol.) was sprayed. In this way, a homogeneous spraying was obtained on all the rounds being treated.

The cork rounds were then subjected to a thermal treatment from a temperature of

50 ⁰ C to a temperature of 140 ⁰ C in a time range of 205 minutes, through a hot air flow within the rotating drum at 3 rpm, and a suction of the gaseous effluents.

For the cork rounds treated according to the present example, there was evaluated the abatement of TCA by comparing the starting content of TCA and the content at the end of the thermal treatment. The results of said evaluations are given in Figure 4, where 50 contaminated cork rounds each revealed surprisingly a practically total abatement of said substance.

Example 5

Process according to the invention used for the treatment of cork rounds

A batch of approximately 150,000 horizontal-pored cork rounds was introduced into a tank of suitable dimensions to be subjected to the process according to the present invention.

Said batch was subjected to a first step of absorption of water at a temperature of

60°C for approximately 80 minutes. The cork rounds were then taken out of the tank and conditioned for 5 days, during which the humidity therein was monitored and was found on average to be as follows:

The cork rounds were then introduced into a drum, which was then made to turn at 22 rpm, whilst on the cork rounds a solution comprising 9.9 L of water and 2.55 L of H ₂ O ₂ (130 v/v) was sprayed. In this way, a homogeneous spraying was obtained on all the cork rounds being treated.

The cork rounds were then subjected to a thermal treatment from a temperature of 50 ⁰ C to a temperature of 130°C in a time range of 155 minutes, through a hot air flow within the rotating drum at 4 rpm, and a suction of the gaseous effluents. For the cork rounds treated according to the present example, the abatement of

TCA was evaluated by comparing the starting content of TCA and the content at the end of the thermal treatment. The results of said evaluations are given in

Figure 5, where 50 contaminated cork rounds each surprisingly revealed an in effect total abatement of said substance.

Example 6

Process according to the invention used for the treatment of cork granulate

A batch of approximately 500 kg of cork granulate was introduced into a tank of suitable dimensions to be subjected to the process according to the present invention.

Said batch was subjected to a first step of absorption of water at a temperature of

50 ⁰ C for approximately 20 minutes. The cork granulate was then taken out of the tank and conditioned for 3 days, during which the humidity therein was monitored and was found on average to be as follows:

The cork granulate was then introduced into a drum, which was then made to turn at 4 rpm, whilst on the cork granulate a solution comprising 2 L of water and 0.5 L of H ₂ O ₂ was sprayed. In this way, a homogeneous spraying was obtained on all the cork granulate being treated.

The cork granulate was then subjected to a thermal treatment from a temperature of 50 ⁰ C to a temperature of 150 ⁰ C in a time range of 90 minutes, through a hot air flow within the rotating drum at 4 rpm, and a suction of the gaseous effluents. For the cork granulate treated according to the present example, the abatement of TCA was evaluated on the basis of the grain size selected, by comparing the starting content of TCA and the content at the end of the thermal treatment. The results of said evaluations are given in Figure 6, where there is surprisingly observed a total abatement of said substance for all the grain sizes observed.

_** * _{**** ***}

From the detailed description and the examples given above, the advantages achieved by the process according to the present invention are clearly evident. In particular, said process thus enables the abatement of these compounds in an effective, quantitative, and advantageous way under the economic standpoint as well as the standpoint of implementation. Furthermore, the process according to the present invention uses water as the only treatment solvent wherein H ₂ O ₂ and a basic compound are present and does not require any variation of pressure for favouring extraction of the undesired compounds, consequently advantageously enabling a significant energy saving to be achieved, as well as a considerable simplification in terms of implementation and equipment required.