WO2004054767A1

WO2004054767A1 - High pressure treatment of cork and oak chips

Info

Publication number: WO2004054767A1
Application number: PCT/AU2003/001663
Authority: WO
Inventors: Mike Burfield; Mark Henderson
Original assignee: Australian High Pressure Processors Pty Ltd
Priority date: 2002-12-13
Filing date: 2003-12-12
Publication date: 2004-07-01
Also published as: AU2002953512A0

Abstract

There is described a method of eliminating mould genera from cork and/or timber. The embodiments chosen involve the treatment of cork that is intended for use as a closure for a wine product while there is suggestion that the timber chosen, oak chips, would be suitable for use in the making of wine. Two examples of a cork treatment method are described. The first method treats cork surrounded by liquid under great pressure. Timber could be substituted for the cork in either method. The second method incorporates the use of a secondary container for the cork and or timber, which is also surrounded by liquid under great pressure. The liquid, in contact with the cork or timber, can contain an anti-oxidising and/or antibacterial liquid. The method can be used on raw or processed forms of cork and/or timber.

Description

HIGH PRESSURE TREATMENT OF CORK AND OAK CHIPS

This invention relates to a method for treating cork so as to eliminate or reduce cork taint.

BACKGROUND

Cork is a natural product (the bark of a tree Quercus Suber) and can sometimes contain mould.

When cork is used to create a long life stopper for a liquid in a bottle or container the mould can migrate to the liquid contents and manifests itself by creating a musty aroma that is detectable at the time the bottle is opened. In other instances the musty smell is less pronounced, the main effect being that the liquid in the container is robbed of its aroma and its flavour compromised and often described as being like the taste that mouldy paper or a wet cellar might have. A "corked" wine means that a mould has grown within the pores of the cork, has combined with traces of the bleach used to treat the cork, and has created a gaseous product that taints the wine. Many drinkers would not pick a slightly tainted wine and they will tend to incorrectly blame the wine quality; hence serving an injustice to what otherwise may have been an excellent wine when really the cork is at fault.

Cork taint is most apparent in wine bottles sealed with cork as a musty wet hessian aroma and an off palate. However, the mechanisms for spoiling wine in bottles can also be the result of inconsistent sealing and random oxidation.

According to wine industry figures in Australia, most likely valid internationally, the rate of cork taint varies between 3-8% of all corked wine bottles. This percentage leaves aside other cork-related faults such as leakage and crumbling. Cork taint is often due to mould development and growth in wine corks, but actinomycetes such as Streptomyces species may also be implicated, through the production of compounds such as geosmin, guiaicol and 2-methylisoborneol. The principal mould genera responsible for the production of compounds such as 2,4,6-trichloroanisole in wine corks are Penicillium, Aspergillus and Trichoderma species (typically referred to as TCA). Other genera are also capable of producing chloroanisoles from chlorophenols. Some of the species that have been identified from affected cork include Penicillium glabrum and P. granul tum. Other compounds that may contribute to cork taint are some of the higher alcohols such as 2-methylisoborneol and methyl ketones.

Chloroanisoles may be formed in other substrates such as fibreboard packing material. Moulds identified as capable of producing chloroanisoles in fibreboard include Aspergillus flavus, A. sydowii, A. υersicolor, Eurotium repens,

Paecilomyces variotii, Penicillium breυicompactum, P. corylophilum, P. crustosum, P. roqueforti, Trichoderma harzianum and T. pseudokoningii. These moulds could also be expected to occur on wine corks, so would have the potential to contribute to the problem.

Sulphur dioxide is a recognised anti-microbial compound. It has the advantage that it is already widely used in the wine industry, and so could be the most suitable compound for soaking corks to inactivate mould. S0₂ has been used to treat wine musts to inactivate wild yeasts and moulds. Concentrations of 4-8 mg/L molecular S0₂, achieved by the addition of metabisulphite corresponding to 500-800 mg/L S0₂ inactivated all yeasts and moulds in treated must.

Hydrogen peroxide (H₂θ2) has also been used in the treatment of wine corks to control cork taint. In 2001, about 26 billion corks were used to seal wine bottles worldwide and Australia and New Zealand used more than 150 million of those. Corks cost between 7 and 40 Australian cents each (depending on quality, length and so on). Tree bark cork primarily sourced from Portugal, Spain and North Africa is available in a variety of grade, typically A+, A, B, C and D or 1-5 (with A and 1 being the highest grade). The cheaper corks are agglomerate (fused together particles of cork) and colmated (or from low quality tree bark whose cracks and holes are filled with a combination of cork dust and adhesive). Both these types of cork product have a much higher rate of cork taint than single piece corks.

The use of oak and other timbers in the making of wine is also well known and unfortunately these timbers can also be carriers of TCA.

Some of the methods employed to-date to eliminate and reduce the incidence of cork taint include boiling the raw cork material, fumigation of the raw cork material as well as the formed cork stoppers. Dipping formed corks in one or more anti-oxidising and/or antibacterial solutions using various periods of submersion and various concentrations of active ingredients. Microwave and ultrasound energy has also been used in an attempt to rid the cork of the taint causing moulds. Synthetic covers for the corks are also being trialed.

With a 3 - 8 % spoilage rate due to cork taint in spite of current anti-cork taint processes the cost to the wine industry is considerable.

However, regardless of how much is known of the causes of cork taint and the use of various methods to rid those causes of cork taint from the cork material, it has heretofore been impossible to eliminate taint causing agents from cork. Particularly frustrating and ultimately expensive for wine merchants, restaurants and the reputation of users of cork in the wine industry has been the inability to eliminate cork taint from cork used in the bottling of wine and wine products.

The inconsistency of the remedies used thus far and the cork material itself has spawned new industries that produce synthetic cork and screw top wine bottle seals that now compete directly with the cork industry as a stopper material. The Stelvin screw cap closure is the most well-known non-cork alternative. Despite reluctance by wine drinkers and makers to diverge from tradition, more and more quality wine makers are endorsing and using the Stelvin screw cap closures. Stelvin screw cap closures are but one example of a Roll On Tamper Evident (ROTE) closure. Stelvin's as they have become known, completely avoid the cork taint problem. Stelvin's are purported to provide a reliable liquid and gaseous seal for the contents of a container and in doing so preserve the quality of the contents. It is however, suggested by some that there is less

"non-fruit derived" secondary development and that development takes longer in a wine capped with a Stelvin closure. At the end of the day, it is of primary importance to the wine maker that the wine drinker enjoys the untainted fruit of their labour and expertise.

BRIEF DESCRIPTION OF THE INVENTION

In a broad aspect of the invention, a method of treatment to eliminate mould genera from cork and timber includes the steps: placing cork and/or timber in a chamber containing a liquid; and raising the liquid pressure inside said chamber containing said cork and /or timber to a level within a range 30,000 to

87,000 psi.

In a yet further aspect of the invention, a method of treatment to eliminate mould genera from cork and timber includes the steps: placing cork or timber in a container containing a liquid and sealing said container; placing said container in a chamber containing a liquid; and raising the liquid pressure inside the chamber containing said container to a level within a range 30,000 to 87,000 psi.

In an aspect of the invention the container is liquid impermeable and the container may contain an anti-oxidising and /or antibacterial liquid.

Specific embodiments of the invention will now be described in some further detail with reference to and as illustrated in the accompanying figures. These embodiments are illustrative, and not meant to be restrictive of the scope of the invention. Suggestions and descriptions of other embodiments may be included within the scope of the invention but they may not be illustrated in the accompanying figures or alternatively features of the invention may be shown in the figures but not described in the specification.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 depicts a flow diagram of a first process involved in eliminating mould genera from cork to prevent cork taint:

Fig. 2 depicts a flow diagram of a second process involved in eliminating mould genera from cork to prevent cork taint: and

Fig. 3 depicts an apparatus suitable for creating an appropriate pressure in a chamber containing prepared corks.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

Fig's 1 and 2 depict a series of steps 1 to 5 and 10 to 22. The methods of eliminating mould genera from cork and/or timber that is described herein are merely embodiments. The embodiments chosen involve the treatment of cork. Two examples of a cork treatment method are described. The first method treats cork surrounded by liquid under great pressure. Timber could be substituted for the cork in the method. The second method incorporates the use of a secondary container for the cork and or timber, which is also surrounded by liquid under great pressure. Either method can be used on raw or processed forms of cork and/or timber.

It is more likely that cork formed into a shape suitable for its for final use will be treated in the manner to be described herein.

A method for the elimination of mould genera from cork is depicted in Fig. 1. The steps begin with the placement of a plurality of preformed corks into a chamber, step 1, an example of the chamber is depicted in Fig. 3. In this embodiment, the pressure chamber is designed to apply high hydrostatic pressure to its contents. Consequently, the pressure chamber is filled with water thus totally surrounding its contents. Since cork has a lower density than water, they will rise to the top regions of the water filled container. However, the chamber is sealed and the water completely fills the volume of the chamber apart from the cork.

It is believed that the application of pressure alone will eliminate the effects of any mould contained in the cork material.

However, it is an optional step to add anti-oxidising and /or antibacterial compound. This is pictorially represented in the Fig. 1 by the use of dotted lines about step 2. By way of example only, the solution may consist of distilled water; metabisulphite in the solution range of lOppm to 600ppm; hydrogen peroxide in the range of 5 to 15 %; or oxalic acid in the range 5 to 15 %. Pressure within the chamber is raised to a level within a range 30,000 to 87,000 psi as indicated in step 3. It is merely by way of example that this pressure range is suggested for this embodiment. It may be found that lower or higher pressures may be required to provide the desired outcome, which is to permeate the cork or timber with the solution or to leech out the potentially harmful mould genera.

It is thought to be of no consequence how fast that pressure level is reached. It is a characteristic of the distribution of the pressure that once a required pressure is reached, the various cork taint components distributed throughout the cork material will cease to act as a damaging agent in the cork material. It is also thought to be of no consequence how fast or slow the pressure is returned to atmospheric pressure so that the cork material can be retrieved. As indicated previously, the application of pressure alone will suffice to rid the cork of the damaging mould and bacteria described previously.

It is a preference though, that the pressure be maintained while there is anti- oxidising and /or antibacterial compounds in the chamber, as the pressure will ensure that those compounds are forced throughout the cork material. It is also a preference that the pressure is applied for a period as noted in step 4 that is in the range 30 seconds to three minutes (180 seconds). The period will be readily determined by experiment for the different corks and timbers to be treated. Again, this step is shown in dotted lines, as it is an optional step.

Finally, the corks have been pressure treated and /or impregnated with an anti- cork taint agent or agents as depicted in step 5.

The most likely embodiment of the method is illustrated in Fig. 2. The method steps begin with the placement of a plurality of preformed corks into a container, step 10. The container in this embodiment is preferably made of plastic of the thin walled PTFE type. The plastic is preferably liquid impermeable. The quantity of corks placed in to the container (in this embodiment) is preferably 100. A liquid quantity of 200ml of anti-taint agent

(for example, anti-oxidising and /or antibacterial liquid) is added to the container as indicated at step 12. The container is sealed preferably to exclude gases from the inside of the container before being sealed. Clearly not all gases can be excluded but the degree of evacuation required can be determined by experimentation. The aim being to ensure that all the corks in the sealed container are properly treated by the process, resulting ultimately in the elimination or marked reduction in cork taint causes.

Although the cork used is preferably that suitable for use in wine bottles the method described is applicable to all types of cork regardless of its final use.

It is however a favourable consequence of the use of the method described herein that the quality range of cork useable in wine bottles is increased. This is manifest by the ability to use cork quality or type that would otherwise be unsuitable because of its known susceptibility to cork taint such as lower grade and agglomerates and colmated cork.

Furthermore, various timbers such as oak used in wine making can also be treated in the manner described to eliminate or reduce mould genera.

It is also anticipated that the use of activated carbon in the container will adsorb the impurities that are leeched out of the material in the container.

The inventors consider that the use of anti-oxidising and /or antibacterial compound is optional. This is pictorially represented in the Fig.2 by the use of dotted lines about step 12. By way of example only the solution may consist of distilled water; metabisulphite in the solution range of lOppm to 600ppm; hydrogen peroxide in the range of 5 to 15 %; or oxalic acid in the range 5 to 15 %.

At step 14 the container is sealed such that liquid can not escape. This can be achieved by heat sealing along the opening of the container however other sealing techniques will be readily available.

At step 16, the containers (about 50 of them) are added to a pressure chamber, an example of the chamber is depicted in Fig. 3. The pressure chamber depicted in Fig. 3 is one of the smaller versions available. It has a capacity of 25litres while there are versions in a range up to a capacity of 250 litres. Each chamber has associated high-pressure water pump/s that create the internal water pressures required. The pressure chamber is filled with water to totally submerging its contents.

As stated previously in conjunction with the description of step 3 in Fig. 1 pressure within the chamber is raised to within a range 30,000 to 87,000 psi as indicated in step 18 of Fig. 2. It is merely by way of example that this pressure range is used in this embodiment.

It may be found that lower or higher pressures may be required to provide the desired outcome, which is to permeate the cork or timber with the solution or to leech out the potentially harmful mould genera.

As described previously, it is thought to be of no consequence how fast that pressure level is reached. It is a characteristic of the distribution of the pressure that once a required pressure is reached the various cork taint components distributed throughout the cork material will cease to act as a damaging agent in the cork material.

It is also thought to be of no consequence how fast or slow the pressure is returned to atmospheric pressure so that the containers can be retrieved from the chamber.

It is a preference though, that the pressure be maintained while there is anti- oxidising and /or antibacterial compounds in the container, as the pressure will ensure that those compounds are forced throughout the cork material. It is also a preference that the pressure is applied for a period as noted in step 20, that is in the range 30 seconds to three minutes (180 seconds). The period will be readily determined by experiment for the different corks and timbers to be treated. Again, this step is shown in dotted lines, as it is an optional step.

At the described pressure level and above, the liquid bearing the anti-oxidising and/or antibacterial compound will permeate the volume of all the corks located in the container as indicated in step 22. Each cork will thus be provided with a store of anti-oxidising and /or antibacterial compounds that will destroy cork taint promoting agents that may enter the cork after the pressure treatment described herein.

The determination of whether the mould genera has been eliminated or suitably reduced is a matter of scientific analysis.

One such method is the use of Solid Phase Micro Extraction (SPME), which provides an absolute measurement of TCA. The SPME process involves using Gas Chromatography (GC) and Mass Spectrometry detection (MS). The first step involves using a sealed container to soak the cork in liquid, distilled water. Then, a fibre of PDMS (polydimethyl siloxy) is introduced into the headspace above the cork. This fibre attracts molecules of TCA (2,4,6 - Trichloroanisole) - the chemical most closely associated with cork taint. The fibre is then put into the Gas Chromatograph (GC), which separates the compounds so they can be measured. In cork quality control programs, the liquid is usually a cork soak containing an unknown amount of TCA. A cork soak either is deemed acceptable (pass) or rejected (fails) based on statistical criteria. Releasable TCA is the concentration of TCA in a cork soak after it reaches equilibrium. Only a small portion of the cork's total TCA is transferred to a soak solution the rest is bound to the cork. The TCA measurement technique described is therefore a released TCA measurement and there is still work to be done to find a definitive correlation between the released amount of TCA and the amount in the cork.

Other TCA measurement techniques exist.

The chamber 24 depicted in Fig.3 is preferably a Fresher Under Pressure Ultra High Pressure apparatus manufactured by Flow International Incorporated of 2350064^th Avenue South - Kent, Washington 98032 USA. This apparatus is merely an example of equipment that has been found suitable for this method of treatment of cork as disclosed herein.

This apparatus uses water 26 to apply uniform pressure about the entire volume of the product 28 or container/s located in the chamber 24. The water is typically treated and non-gaseous. As described previously the water is used to apply the required pressure in a uniform manner hence there are no shear forces and product is not crushed or damaged in any way. The application of forces using hydrostatic means and the maintenance of the products structural integrity meets industry expectations however some amount of product 28 drying may be required. The apparatus is filed with water using input and output valves 30, and a product access and exit opening (not shown) is used. The internal pressure is increased when an external water pump is used to force water 32 (typically itself anti-fungal treated and non-gaseous) behind a moveable piston 34.

It will be appreciated by those skilled in the art, that the invention is not restricted in its use to the particular application described. Neither is the present invention restricted in its preferred embodiment with regard to the particular elements and /or features described or depicted herein. It will be appreciated that various modifications can be made without departing from the principles of the invention. Therefore, the invention should be understood to include all such modifications within its scope.

Claims

THE CLAIMS DEFINING THE -NVENHON ARE AS FOLLOWS:

1. A method of treatment to eliminate mould genera from cork and timber includes the steps: a) placing cork and /or timber in a chamber containing a liquid; and b) raising the liquid pressure inside said chamber containing said cork and/or timber.

2. A method according to claim 1 wherein said liquid pressure inside said chamber is raised to a level within a range 30,000 to 87,000 psi.

3. A method according to claim 1 wherein said liquid contains an anti- oxidising and /or antibacterial liquid.

4. A method according to claims 1, 2 or 3 wherein said cork and/or timber is in its raw form.

5. A method according to claims 1, 2 or 3 wherein said cork and/or timber is in a processed shape.

6. A method according to any preceding claim wherein said pressure in said chamber is maintained for a predetermined time being in the range 30 to 180 seconds.

7. A method of treatment to eliminate mould genera from cork and timber includes the steps: a) placing cork or timber in a container containing a liquid and sealing said container; b) placing said container in a chamber containing a liquid; and c) raising the liquid pressure inside the chamber containing said container.

8. A method according to claim 6 wherein the liquid pressure inside said chamber is raised to a level within the range 30,000 to 87,000 psi.

9. A method according to claim 7 or 8 wherein said container is liquid impermeable.

10. A method according to claims 7, 8 or 9 wherein said container contains an anti-oxidising and/or antibacterial liquid.

11. A method according to claims 7, 8, 9 or 10 wherein gas is excluded from said container before being sealed.

12. A method according to claims 7, 8, 9, 10 or 11 wherein said cork or timber is in its raw form.

13. A method according to claims 7, 8, 9, 10 or 11 wherein said cork or timber is in a processed shape.

14. A method according to claims 7, 8, 9, 10 or 11 wherein said pressure in said chamber is maintained for a predetermined time being in the range 30 to 180 seconds.

15. A method according to any preceding claim wherein the liquid in said chamber is water.