The brewing of carbonated beverages in the domestic context has traditionally been a two stage process employing a primary fermentation in which the bulk of fermentable material in a liquor is converted into alcohol and carbon dioxide by the metabolism of yeast at one atmosphere pressure.

A carbonated beverage is produced by decanting the liquor into a second, sealed container and allowing the remaining, or additional fermented material to be metabolised under pressure and thereby force more C02 into solution.

The problem with this method is controlling the secondary fermentation such that the correct amount of C02 is produced.

Too little and the result is a flat beverage.

Too much and bottles will burst.

Further, different styles of beverage, for example, spritz, beer, and Champagne, each contain different amounts of C02, thus adding another level of complexity for the brewer.

Careful use of a hydrometer and some calculation will often overcome these problems, but even experienced brewers can be defeated by variations in materials, or in subsequent ambient storage conditions.

It is an object of this invention to greatly simplify the brewing process, making the use of the hydrometer unnecessary and reducing the risk of burst bottles to insignificant levels.

It is another object of this invention to produce carbonated beverages of different levels of dissolve C02 by means of brewing under different, preset pressure levels.

It is a further object of the invention to provide an integrated package for fermentable liquors, for example fruit juice, such that a consumer may purchase, brew and consume a carbonated beverage all from a single container, simply and safely.

It is a further object of the invention to modify the brewing process facilitated by the invention to allow choice of alcohol content in brewed beverages from less than 1% to around 20%.

The invention consists of an outer rigid member in the upper face of which is formed one or more apertures; and an elastomeric membrane containing a substantially linear slit such that under ambient pressure when the membrane is brought sealingly into contact with a container by means of the rigid member the slit forms a closed valve, which, under elevated pressure, progressively deforms outwardly through one of said apertures, opening at a predetermined pressure and allowing excess gas to escape, and closing at a predetermined pressure, thereby maintaining said container at a specified pressure, which may take any value from 1 to 4 atmospheres, being controlled by means of aperture diameter and membrane characteristics.

Closures incorporating pressure relief valves are generally well known in the trade and literature.

The membrane valve in this case is formed from sheet material, the punching and slitting operations being performed in one simultaneous operation. Working within this method of manufacture, it has been found that determining the operating characteristics of these valves is a matter of controlling the following variables: Elastomeric properties of membrane and membrane thickness.

Diameter of aperture formed in the upper face of the outer rigid member.

Extent of elastic deformation of membrane whilst slit is machined.

Cutting characteristics, including length, of incision tool.

It is noted that many combinations of material and aperture size may be employed to achieve a desired result across a wide range of operating pressures. It is therefor possible to apply the closure to a wide range of existing containers, for example, glass bottles, soda bottles and wide necked polymer bottes, as illustrated in Figs. 1-5, each of which is a bisecting cross section view.

Fig. 1 shows the closure applied to a screwed neck bottle at ambient pressure. The membrane (1) is freely located within the outer rigid member (2), and is brought sealingly into position on the bottle neck (4) as the outer rigid cap is tightened into a closed position. At this stage the membrane is substantially flat, with the slit forming a closed valve across the aperture (3) sealing against both escape of contents, when the bottle is shaken, and intrusion of extraneous microbes, during the early stages of fermentation, as pressure within the bottle moves up from ambient to the preset level.

Fig. 2 shows the closure at operating pressure, the membrane (5) being progressively deformed outwardly through the aperture until the slit opens to allow the excess gases of fermentation to escape. As fermentation subsides, or is halted, and the production of gas declines, the valve re-closes, maintaining the bottle at the pressure appropriate for the chosen level of carbonation. Typical values for these operating pressures are; spritz style: 1.5 atmospheres, beer style: 2 atmospheres, Champagne style: 3 atmospheres.

The configuration of Figs. 1 & 2, is perhaps the most appropriate where the closure is to be used for repeated cycles of brewing, in that it can be easily disassembled for washing and sterilising. Yet it is cheap enough to be used in one-use or disposable applications.

In these configurations the membrane containing the slit/valve extends wholly over the inside upper face of the outer rigid member, and thus both the sealing and valving functions are performed by the same membrane.

However, an 0 ring may be used to perform the sealing function inside the outer rigid member with the membrane incorporating the valve extending over the whole of the inside face of the outer rigid member, or merely over a small portion in excess of the actual aperture, in this case being bonded in position over the aperture.

It is also understood that the aperture need not be centrally located in the outer rigid member.

Fig. 2A shows how an additional aperture in the outer rigid member might be formed to accommodate a pressure dispensing capability (1) for the container, whilst maintaining the relief valve. In such an embodiment, the membrane will probably be bonded to the outer rigid cap to ensure alignment of the apertures and their respective slit/perforation in the membrane (the membrane being punched at (2) with a perforation of smaller diameter than the dispensing tube (1) to effect an elastomeric seal around said tube.) Given the economical nature of the method of manufacture of these closures, and, as one highly preferred application of the closure is the brewing of commercially available fruit juice, it will be seen from the closure so described that an advantageous embodiment would include a dose of yeast within the cap, thus allowing the consumer to brew directly in the bottle of purchase. The package of purchase then also becomes the brewing apparatus.

Fig. 4 shows the closure where the outer rigid cap is formed with an aperture and membrane valve brought sealingly into position over a container as before. In this embodiment the outer rigid cap consists of two parts; a main body, which is substantially similar to the simple forms of the closure, together with a rigid sleeve section (13) which is screwed or pressed into a closed position as in Fig. 4a. In this position the closure holds a dose of yeast, (12) (which may be granulated, tablette or encapsulated), in a fixed, Substitute Sheet (Rule 26) RO/AU sealed position between the membrane and a cavity (11) formed as an integral part of the outer rigid member. So fixed and sealed the yeast is kept dry and immobilised during transit and storage. The whole closure being encased in a thin film sleeve (14) to ensure tamper-proofing and the exclusion of foreign matter. In such a configuration, the yeast and liquid contents of the container are kept apart until the consumer peels off the outer sleeve and unscrews the upper sleeve and shakes the bottle. Fig. 5 shows the bottle just prior to shaking, which will bring yeast and liquid into mutual contact, (the upper and lower sections of the outer rigid member being connected by communicating passages), which is at this stage prevented from escaping the bottle by the membrane valve (10) being substantially flat and in a closed position.

Having set the fermentation in progress, it continues at ambient temperature in the sealed bottle until such point as the pressure in container opens the valve and allows excess gas to escape to the atmosphere.

Whilst the arrangement in Fig. 5 illustrates an upward opening outer rigid sleeve, it could equally be employed to house a capsule of liquid yeast which would be intentionally ruptured by a downward repositioning of the rigid outer sleeve.

It will be apparent that the closures and containers so disclosed form part of a method of producing carbonated alcoholic beverages across a wide range of carbonation values and also make possible the safe brewing of beverages across a wide range of alcohol content.

The method comprises six elements, disclosed as follows; 1) A vessel capable of safely operating at the appropriate pressure for the desired level of carbonation.

2) A sealing and venting method for said vessel.

3) Fermentable material placed in said vessel.

4) A dose of yeast brought into contact with fermentable material.

5) Means of establishing the alcohol content of fermenting or fermented material.

Substitute Sheet (Rule 26) RO/AU 6) Means of halting the fermentation at any stage in the fermentation process.

Dealing with each of these elements in turn: 1) Suitable vessels are to be found in many forms, for example, the soft drink or soda bottle, glass beer or champagne bottes, wide necked fruit juice bottes, and others.

2) The sealing and venting of such a vessel may take many forms; the two operations may be achieved by one elastomeric membrane, or by any of a vast variety of pressure relief mechanisms. The vessel must be sealed so as to maintain the chosen operating pressure and also vented to allow excess gases of fermentation to escape.

3) Fermentable material may take many forms and may embody an abundance of fermentable material such that the limiting factor in the production of alcohol is the alcohol tolerance of the yeast, such material being susceptible to the halting step (6), or they may be self limiting by being formulated so that fermentation exhausts the available fermentable material at some point below the alcohol tolerance of the yeast. Fermentable materials may be liquids, syrups, concentrates or powders.

4) Yeast is brought into contact with the fermentable material in the appropriate proportion to establish fermentation.

5) Means of estimating the alcohol content will take two general forms: A) use of prior data to establish the likely alcohol content of the liquor.

Each fermentable liquor and each variety of brewing yeast will, in concert, exhibit a particular fermentation profile. That is, the rate at which fermentable material is converted into alcohol and C02 will be to some degree peculiar to each liquor/yeast combination (and also a function of temperature and pressure). In practice, a generalised profile as shown in Fig. 6 will usually be adequate for estimating the alcohol content at any point in the fermentation profile.

Based on this relationship, a suitable graphical representation can be consulted without recourse to opening the container and making physical measurement.

B) Measurement directly by means of hydrometer or other means requiring contact with fermenting material.

Substitute Sheet (Rule 26) RO/AU 6) Means of halting fermentation. Fermentation typically exhausts itself when all the fermentable material in a liquor is converted into alcohol and C02, or the yeast reaches its alcohol tolerance level. Such self limiting processes are one route to a halted fermentation but refrigeration to a temperature below that where the yeast is active is a convenient and effective option.

One preferred embodiment of this process would consist of; 1) The standard soda bottle, carbonated soft drink bottle or wide mouth juice bottle.

2) Closure for said bottle incorporating a pressure relief mechanism.

3) Fruit based fermentable material.

4) Granulated yeast.

5) Printed fermentation profile attached to bottle.

6) Use of domestic refrigeration at 5 degrees Celsius or less, combined with a yeast active at 10 degrees Celsius or greater.

A carbonated alcoholic beverage is thus brewed in a vented container at ambient temperature, set at an operating pressure commensurate with the chosen level of carbonation. Fermentation continues for a time period which corresponds with the chosen level of alcohol (as read off fermentation profile). Fermentation is arrested by refrigerating the container to a temperature at which the yeast is inactive, at which point the alcohol content remains substantially fixed. The beverage is now ready for consumption at the consumer's leisure. This method has the added advantage of being able to re-carbonate the contents of containers where consumption is spread over two or more sittings. By the simple expedient of allowing the container to remain unrefrigerated for a few hours the yeast reactivates, and, as long as the pressure relieved closure is in place, safely re-carbonates the beverage.