WO2006026801A1

WO2006026801A1 - Improved process for packaging wine in aluminium containers

Info

Publication number: WO2006026801A1
Application number: PCT/AU2004/001750
Authority: WO
Inventors: Gregory John Charles Stokes; Steven John Anthony Barics
Original assignee: Barokes Pty Ltd
Priority date: 2004-09-10
Filing date: 2004-12-13
Publication date: 2006-03-16
Also published as: EP1796969A1; AU2004210603A1; EP1796969A4; AU2006203684A1

Abstract

An improved method of packaging red or white, still or carbonated wine in two piece aluminium cans. The wine has less than 35 ppm of free sulphur dioxide, less than 330 ppm of chloride anions and less than 800 ppm of sulfate anions. The method involves filling an aluminium container body with the wine and sealing the container with an aluminium closure such that the gauge pressure within the can is at least 170 kPa and wherein the inner surfaces of the aluminium container are coated with a corrosion resistant coating and wherein the equilibrium head space composition after packaging has the composition of at least 95% w/w of nitrogen, less than 5% w/w of carbon dioxide, and less than 2% w/w of oxygen; and wherein the temperature of the wine at the time of filling the can body is at 10 degree Celsius. The wines exhibit excellent performance after storage or the quality of the wine does not deteriorate significantly on storage.

Description

IMPROVED PROCESS FOR PACKAGING WINE IN ALUMINIUM CONTAINERS

This invention relates to an improved process for packaging wine in aluminium containers. More particularly, the invention relates to an improved process where the wines are still wines. Background of the Invention

It has been proposed for over twenty years that packaging wine successfully in aluminium cans is a very worthwhile commercial objective. This is set out in an article by CHURCH, Fred L., "Next Aluminium Target: Cans for Wine, Water, Juices", Modern Metals, Volume 36 No. 12, issue 1981 at pp. 28, 30, 32 and 34.

Despite this objective being clearly stated over twenty years ago, there has been no evidence of successful packaging of wine in two-piece aluminium cans until the last couple of years when wine was successfully packaged in two-piece aluminium cans by Barokes Pty Ltd, an Australian based company. Part of the explanation for this long period of time between the clear statement of the commercial goal and its attainment is the requirement for long shelf life of the packaged product.

For wine based products it is accepted that shelf lives of a year or more are required. Such is not the case with some other beverages such as beer where consumers appear to accept a slight deterioration in the packaged product. In these products the development of turbidity or haze after extended storage appears to be acceptable. The objective with packaging wine in aluminium cans is not simply to produce a product that may be consumed a short time after packaging but after extended periods of storage under adverse conditions. Under harsh conditions of elevated temperatures, there is the increased possibility of corrosion of the aluminium can. Furthermore, wine is characterised as having sulfur dioxide levels that accelerate the degradation of the polymeric lining on the inside of the can and then the aluminium itself. The taste of wine products is adversely affected by levels of aluminium cations above relatively low threshold levels. In patent application WO 03/029089 Barokes disclosed a method of successfully packaging wine in two-piece aluminium cans. The contents of that specification are incorporated into this specification by this reference. In the Barokes' invention, the inventors found that by producing wines within specified parameters and then canning that wine under defined conditions, a satisfactory product could be achieved. A satisfactory product was one defined as having satisfactory shelf life as assessed by smell, appearance and taste. Upper limits are placed on chloride and sulfate anion concentration. As well as influencing can corrosion, these anions can also affect taste. It is known that chloride ions can impart a salty taste and that sulfates can impart a bitter taste. These are two of the four basic tastes detected by the taste buds situated on the tongue: bitter, salt, acid and sweet.

The Barokes¹ wine in a can product is an innovative product that has a potential market with existing wine drinkers as well as a potential market with consumers who are not already wine drinkers. The Barokes' product has been packaged in 250 ml slim line cans which have appeal to both these potential markets. The traditional, existing wine drinker market tends to pour the wine in the can into a glass before drinking the wine. The new wine drinker market is more likely to drink the wine directly from the can. The Barokes¹ product is canned under pressures of at least 170 kPa.

The pressure is gauge pressure and is determined at 20°C. The pressure in the head space confers mechanical strength to the aluminium can. It also may influence the rate of chemical reactions within the wine. It is well known that chemical equilibria and reaction rates may vary with pressure according to the Chartelier principle. This principle is exploited in the high pressure pasteurisation of food being pioneered by Food Science Australia. Wine is a complex product which undergoes many chemical reactions on storage. A change in head space pressure may lead to a change in the rate of some of these chemical reactions, particularly those associated with a change in molecular volume or the formation of volatiles. In wine, such reactions are quite likely to occur. Over extended periods of time of months, head space pressure differences between cans of as little as 300 kPa may lead to detectable changes in the rate of reactions in wine. These differences may lead to differences in the taste and/or flavour of wine on storage.

It has been observed that some of the Barokes' canned wines, prepared as in WO 03/029089, when poured into a drinking glass exhibit a slight spritzig characteristic. This evidences itself by the formation of bubbles at the interface between the inner surface of the drinking glass and the wine. While not adversely affecting the flavour of the wine, this characteristic is considered by some traditional wine drinkers to be deleterious, at least visually, and is undesirable and considered a negative feature compared to traditional bottled wine. Clearly this is not perceived as a fault by consumers who drink the wine directly from the can. It is also only a problem associated with still table wines.

It would be desirable to have an improved process for packaging still wine in aluminium containers where the formation of bubbles in a glass of wine poured from the container is reduced or eliminated. Summary of the Invention

This invention provides in one form an improved method of packaging still wine in aluminium containers by preparing wine characterised in that it has less than 35 ppm of free SO₂, less than 300 ppm of chloride anions and less than 800 ppm of sulfate anions, filling the container body with the wine and sealing the container with an aluminium closure such that the gauge pressure within the can is at least 170 kPa and wherein the inner surfaces of the aluminium container are coated with a corrosion resistant coating and wherein the equilibrium head space composition after packaging has the composition: Nitrogen: at least 95% w/w

Carbon Dioxide: less than 5% w/w

Oxygen: less than 2% w/w, and wherein the temperature of the wine at the time of filling the can body is at least 10°C. Preferably the temperature of the wine at the time of filling the container body is in the range 10 to 25°C, more preferably 15 to 25°C, and most preferably 20 to 25°C. Preferably the level of carbon dioxide in the packaged wine is 0.8% w/w maximum.

Preferably the carbon dioxide head space concentration is less than 3% w/w. Preferably the wine packaged by the process has a maximum carbon dioxide level of 0.6% w/w.

Preferably the wine, when a white wine, has a free sulfur dioxide level in the range 5 to 30 ppm.

Preferably the wine is further characterised as having total nitrites less than 1 ppm and total nitrite plus nitrates less than 10 ppm.

Preferably the aluminium container is a two-piece aluminium can.

Preferably the increase in aluminium content in wine that is stored in the container for three months in the upright position at 30°C is at maximum of 30%. Detailed Description of the Invention

Carbon dioxide has an important role in wine making and wine. It has been reported by Bryce Rankine in "Making Good Wine - A Manual of Winemaking Practice for Australia and New Zealand" that dissolved carbon dioxide is present in wine and that higher levels are generally required in white wines than red wines. The presence of carbon dioxide contributes to the flavour of the wine. He notes that when the carbon dioxide level is in excess of 1.2 grams per litre, gas tends to force corks out of bottled wine. This is probably explained by the solubility of carbon dioxide in wine. As is well known, the solubility of gases in liquid, including wine, decreases with temperature. At a temperature of approximately 25 °C, carbon dioxide has a solubility in wine at ordinary atmospheric pressure of 1.2 g/litre. Accordingly, at higher temperatures than 25°C the carbon dioxide when at levels of at least 1.2 g/litre is forced into the small volume of the neck, referred to as the ullage, above the wine in a corked bottle of wine. Rankine suggests that a mixture of carbon dioxide and nitrogen may be used in the ullage in a bottled wine. He suggests that for a dry red wine the wine should have a ullage gas composition of 2 parts nitrogen and 1 part carbon dioxide. For white wines he suggests a ratio of 1 :3 of nitrogen: carbon dioxide in the ullage.

The composition of the atmosphere above the wine has several different characteristics depending on whether the wine is in a conventional bottle or in a can. Because of the basic cylindrical shape of a can, the surface area of wine in a can exposed to the atmosphere at the top of the can is much greater than is the case for wine in a conventional glass necked bottle. In a conventional 750 ml glass bottle, the internal diameter of the neck is approximately 20 mm. This calculates as a surface area of approximately 300mm or 0.4mm /ml of wine. For a typical slim line 250mm aluminium can, the surface area is approximately 2100mm² or 8.5mm²/ml of wine. From these calculations it is clear that there is approximately 20 times greater contact between the wine and the atmosphere at the top of a can compared to the situation in a bottle. Accordingly, the teachings relating to bottled wine and the composition of the ullage are found to be not applicable to canned wine. For canned wine we have found that the levels of oxygen in the head space in a canned wine need to be significantly lower than for a comparable bottled wine. A further difference between canned wine and bottled wine is as a result of differences between the thermal expansion coefficients for wine glass bottles and two-piece aluminium cans. It is known for bottled wine that a typical table wine increases in volume by 0.65% when the temperature increases from 2O⁰C to 4O⁰C. The volume of the glass bottles increases by approximately 0.05% for the same temperature increase. This provides a net increase of 0.60% or 4.5 ml in a 750 ml glass bottle. This difference in thermal expansion means that for glass bottles, corks may be forced partially out of the neck or pressure is increased in the head space. We have conducted experiments and have found with 250 ml slim line two-piece aluminium cans, that the internal volume change of the can approximates the volume change of wine over the temperature range of 4°C to 25°C. While the experiments did not extend to higher temperatures, it is to be expected that the thermal expansion coefficients would be similar at these high temperatures. A consequence of the matching of thermal expansion coefficients is that the head space volume in the can is likely to be relatively consistent with temperature. This is desirable in a canned product.

We have also found that for a canned still wine it is desirable to have the wine stored in the can to have a dissolved carbon dioxide level less than 0.8g per litre at 1O⁰C and normal pressure. Preferably there should be less than 0.6g per litre of dissolved carbon dioxide at 10⁰C and normal pressure. Normal pressure refers to atmospheric pressure.

We have found that it is desirable to can the wine under conditions that introduce essentially only nitrogen into the head space during the canning operation. We have also found it desirable to make still wines that lead to relatively low levels of dissolved carbon dioxide. This contrasts to carbonated wines where it is desirable to have high levels of carbon dioxide in the wine so that when the pressure is reduced by pulling the ring tab on the can, bubbles are formed from the release of dissolved carbon dioxide. Carbon dioxide is a product of fermentation and typically thirty to fifty times the volume of wine that is fermented is produced as carbon dioxide. Although most of the evolved carbon dioxide diffuses into the atmosphere, some of the carbon dioxide remains dissolved in the wine. The amount that remains dissolved in the wine is a function of temperature, lower temperatures leading to higher levels of dissolved carbon dioxide. By appropriate temperature control of the wine, the levels may be reduced to the desired levels. In a standard carbonated beverage canning line, the beverage is typically cooled to 4°C for canning. This enables the maximum amount of carbon dioxide to be dissolved. As the temperature increases, the solubility of carbon dioxide decreases. We have found that for still wines it is preferred that the wine for canning is held at a temperature of at least 10⁰C prior to canning to allow any excess dissolved carbon dioxide to be removed. The temperature of the wine is preferably at or close to room temperature as at these higher temperatures the solubility of carbon dioxide in wine is even lower. However, if higher temperatures are used, oxidation and loss of volatiles can be a problem. Reduction in oxidation is one reason why previous canning was carried out at 4°C. However, we have found that although the rate of oxidation of the wine may be 10 or 20 times greater at 20°C than 4°C, the wine canned at 2O⁰C is superior to the wine canned at 4°C.

It is also important that sources of carbon dioxide are kept to a minimum. One potential source is the use of carbon dioxide in the wine production. A second potential source is the wine canning process. A third source is secondary fermentation after canning.

The first source can be controlled by using nitrogen blankets and nitrogen as the source of inert gas in the wine production process.

In the canning process, carbon dioxide introduction is minimised by using nitrogen as the source of inert gas. We have found it desirable to purge the can with nitrogen before filling with the wine. We have found it preferable that the nitrogen used is a relatively pure grade and that best results are achieved with the purity level is at least 99.5%. While excess levels of dissolved carbon dioxide may be reduced to the desired levels, it is preferable that the wine producing and wine canning processes that are used are such that reduction of the carbon dioxide level in the wine is not required.

The third source is controlled in conventional wine making processes by the addition of sulfur dioxide and control of pH. It is also controlled by the levels of bacteria and yeast in the wine. We have found best results are achieved when the bacteria count is < 10 CFU per 100ml and the yeast count is < 10 CFU per 100ml. CFU refers to colony forming unit. A CFU is a single microorganism or a cluster of microorganisms which when cultured on a suitable nutrient will form a visible colony with an impregnant on the surface of or distributed throughout the adsorbent or carrier. We have found that very low levels of oxygen in the head space reduce the likelihood of further yeasts growing and leading to additional fermentation. Preferably the dissolved level of oxygen in the wine is less than 1 ppm and more preferably less than 0.5 ppm. For canning wine it is required to use relatively low levels of sulfur dioxide. We have also found that a pasteurisation step may be introduced after the wine is produced to prevent further fermentation. In conventional wine making processes, usually the increased levels of alcohol produced and sulfur dioxide levels are sufficient to prevent further fermentation.

It is desirable to avoid pasteurisatiaon with wine and we have found that by using sterilisation filters that this step may be avoided. Suitable filtration products are supplied by Cuno, and include Zeta Plus® (0.5 μm) and BevASSURE™ (0.45 μm) filters. These remove suspended yeasts and ensure ^■ microbiological stability. Best results are achieved where a sterile-grade filter pad is followed by final filtration with a membrane filter.

It is preferred that sources of carbon dioxide are reduced to provide canned wines with the desired levels of carbon dioxide. The alternative of producing wines with higher than the desired levels of carbon dioxide and removing the excess carbon dioxide involves additional steps. Furthermore, these additional steps may lead to deleterious effects, such as loss of flavour. In this specification, reference to values for analytes in wine, gas composition, dimensions, volumes and pressure refer to the values as determined under standard laboratory conditions of 20⁰C unless the context provides otherwise.

The preferred containers for the process of the present invention are two-piece aluminium cans. These have been widely used in Australia for beverages since the 1980's. Two-piece aluminium cans have an integral base and side walls formed typically by a drawing, wall ironing and lacquering process. Other suitable containers for the present invention include "bottle cans". These are essentially an aluminium can with a screw cap. These containers have the advantage that they are resealable. Smaller bottle cans up to 300ml which are particularly suitable for wine look like a regular can with a conical top and a screw cap. The bottle cans have been developed in Japan by the Daiwa Can Company.

The invention will be further described by reference to a preferred, non-limiting, example. Example In this example, a wine is prepared and canned according to the invention and compared to a wine produced and canned according to the process described in

WO 03/029089. A white chardonnay wine was produced from chardonnay grapes grown in South Eastern Australia from the 2003 vintage. The wine was produced according to the general wine making techniques described in WO 03/029089. The wine had the following characteristics:

Nitrite mg/L 0.1

Nitrate mg/L 3.2 Sulfate mg/L 430

Phosphate mg/L 70

Cl 46 pH 3.44

Free SO₂ (mg/L) 20.0 Total SO₂ (mg/L) ^■ 134.7

Ethanol (v/v) 13.5

Titratable Acidity (g/L as Tartaric Acid) 6.8

The wine was produced by generally excluding oxygen and removing the carbon dioxide produced from fermentation. Nitrogen blankets were used in the handling and maturation of the wine. The wine so produced had a dissolved carbon dioxide level of 0.6 g/litre and a dissolved oxygen level of 0.7 g/litre. The wine was filtered using a Zeta Plus 6OH filter (0.5 μm) and a bev ASSURE 0.45 μm filter. The wine was then canned at 10°C using carbon dioxide free filling line to produce a canned wine with 0.6 g/litre of carbon dioxide and a head space in the can of 96% nitrogen, and less than 1% oxygen. Liquid nitrogen (99.5% grade) was added before closure to produce a gauge pressure of 175 kPa.

The can of wine stored at 10°C was poured into a glass and the amount of bubbles formed was negligible. A comparative wine was produced with a carbon dioxide level of 1.5 g/litre and a head space composition of 90% nitrogen and 10% carbon dioxide. The wine was prepared using similar methods except that nitrogen blankets were not used to the same extent in the wine production. This wine was canned at 4°C using both carbon dioxide and nitrogen in the head space of the can. This wine exhibited a slight spritzig characteristic and bubbles were produced at the wine/glass interface when the wine was poured into a glass. This comparative wine was assessed as being inferior to the canned wine prepared according to the present invention.

Since modifications within the spirit and scope of the invention may be readily effected by persons skilled in the art, it is to be understood that the invention is not limited to the particular embodiment described, by way of example, hereinabove.

Claims

The claims defining the invention are as follows:

1. An improved method of packaging still wine in aluminium containers by preparing wine characterised in that it has less than 35 ppm of free SO₂, less than 300 ppm of chloride anions and less than 800 ppm of sulfate anions, filling the container body with the wine and sealing the container with an aluminium closure such that the gauge pressure within the can is at least 170 kPa and wherein the inner surfaces of the aluminium container are coated with a corrosion resistant coating and wherein the equilibrium head space composition after packaging has the composition: Nitrogen: at least 95% w/w Carbon Dioxide: less than 5% w/w Oxygen: less than 2% w/w, and wherein the temperature of the wine at the time of filling the can body is at least 10⁰C.

2. A process as defined in claim 1 wherein the temperature of the wine at the time of filling the container body is in the range 10 to 25 °C.

3. A process as defined in claim 1 wherein temperature of the wine at the time of filling the container body is in the range 15 to 25⁰C.

4. A process as defined in claim 1 wherein temperature of the wine at the time of filling the container body is in the range 20 to 25⁰C.

5. A process as defined in any one of claims 1 to 4 wherein the level of carbon dioxide in the packaged wine is 0.8% w/w maximum.

6. A process as defined in any one of claims 1 to 5 wherein the wine, when a white wine, has a free sulfur dioxide level in the range 5 to 30 ppm.

7. A process as defined in any one of claims 1 to 6 wherein the wine is further characterised as having total nitrites less than 1 ppm and total nitrite plus nitrates less than 10 ppm.

8. A process as defined in any one of claims 1 to 7 wherein the aluminium container is a two-piece aluminium can.

9. A process as defined in any one of claims 1 to 8 wherein the increase in aluminium content in wine that is stored in the container for three months in the upright position at 30°C is a maximum of 30%.

10. Packaged wine when prepared by a process as defined in any one of claims 1 to 9.

DATED this 13 ,t^mh day of December, 2004

BAROKES PTY LTD

By their Patent Attorneys: