AU2002229420A1 - Liquid food and wine storage bladder within a container - Google Patents

Description

LIQUID FOOD AND WINE STORAGE BLADDER WITHIN A CONTAINER

Field of the Invention

This invention relates to the storage and optional maturation (by slow-oxidation, polymerisation, infusion) of certain bulk liquid foods such as wine, whisky, edible oils, vinegar and certain liquid spices, such as "Tabasco". Such foods are subject to oxidation and aerobic spoilage by the presence of excess amounts of air-oxygen, but are generally self-preserving against anaerobic bacterial activity by means of their chemical makeup.

a particular aspect, the invention relates to storing liquid foods in flexible bladders, the walls of which are semi-permeable to dissolved (rather than air) oxygen and which may contain infusion bags of Oak chips or sawdust. These bladders are suspended in a tank of water or other liquid of similar density to the stored food within the bladder and fully enclosed in and supported by the surrounding liquid. The dissolved oxygen content of the suspension liquid is then varied to further control the rate of oxygen permeation into the stored liquid food.

Background of the Invention

The traditional means of bulk-storing "self-preserving" liquid foods has been in above-ground stainless steel vessels, typically ranging in volume from about 5,000 litres up to about 500,000 litres. Such storage is required to be oxygen-excluding, but is not required to be aseptic, as the high alcohol content of wine, the lack of free water and it's dissolved oxygen in edible oil and the presence of vinegar in Tabasco all suppress anaerobic bacterial activity.

Stainless steel vessels have certain advantages, being non-rusting, completely impermeable to oxygen and easy to clean. However, they also have certain disadvantages. They can impart metal ions into the stored liquid food, "iron taint", they are expensive to construct in terms of cost per litre stored, especially in smaller sizes, they require thermal insulation and they usually require manual cleaning inside. Furthermore, being of rigid construction and fixed volume (except in certain special cases), there is rarely an exact match between the available volume of liquid to be stored and the fixed volume of the tank. To prevent excessive air-oxygen contact with the stored food, the resulting air head-space, or "ullage" generally must be flushed with an inert gas or the liquid free-surface blanketed with (10% more dense) carbon dioxide, often self-generated by fermentation.

Accordingly, in recent years there have been a number of flexible collapsible containers introduced for bulk-storing and/or transporting drinking water, wine and liquid foods. The most common of these are flat pillow-pouches, laid out on the ground and capable of holding many thousands of litres. However, being self- supporting against the internal pressure of the contents, all are required to be constructed from heavily-reinforced materials and to utilize bonded joints requiring adhesive materials that may taint sensitive foodstuffs such as polyurethanes which contain iso-cyanurates.

Another common type of flexible bulk pouches are used to transport wines. These so- called Flexitanks are constructed from heavy-walled laminates and are installed in 6M and 12M shipping containers. Similarly to on-ground pouches, these have adhesive bonded seams and are not suited to long-term storage as they are can taint wines and are permeable to oxygen.

The next most-common storage system for self-preserving liquid foods are traditional wooden barrels, typically from 200 to 1,000 litres in capacity. Foods such as wine, whisky and certain liquid spices, have been found to benefit in a number of ways from such barrel-maturation. These befits include reduction of astringency, enhancement of colour and development of integrated character. This results from a complex series time-dependent, sequential chemical changes, notably slow-oxidation, condensation and polymerization reactions. Some flavour elements from the wood are also infused into the liquid adding desirable additional characters. The chemical changes that occur in barrel maturation require an extended period of time, from months to years, to bring to completion. Stainless steel tanks are generally unsuitable for such maturation, even when Oak infusion elements such as wooden staves or chips are included, as they are completely impermeable to air and oxygen.

Moutounet, Mazauric, St. Pierre and Hanocq in their study "Gaseous Exchange in Wines Stored in Barrels", Journal des Sciences et Techniques de la Tonnellerie, Vol. 4, 1998 (herein incorporated by reference) and others, have recently shown that air (and it's oxygen) continuously enters barrelled wine via micro-pores in the wooden staves and the stave-to-stave joints. This study describes the mechanism by which water and alcohol vapour in liquors, permeating outwards through the wooden barrel walls and evaporating, is exchanged continuously with small amounts of air.

The continued availability of this small amount of air-oxygen, the initial dissolved oxygen within the stored liquid and that which is randomly added during barrel topping-off initiate a progressive series of time-sequential "redox" reactions. These are sustained not only by the continuing air-oxygen entry into the barrel, but also, in wine, by the oxidative reaction products such as hydrogen peroxide from earlier reactions in the sequence.

It is these reactions which give rise to "maturation" and it is a primary purpose of this invention to replicate these in a non-barrel environment. Various means which aim to achieve this, exist in the prior art.

Relevant Prior Art

Micro-oxygenation involves the storage of wine in stainless steel tanks, usually with added wooden elements to infuse oak character, to which measured small amounts of oxygen are added by micro-bubbling, over an extended time period. This technique has been shown to soften and reduce astringency in wine, but does not allow completion of the full maturation process, as undesirable oxidative side-effects or "fast-oxidation" limits the time period over which this technique can be effectively applied.

The CSIRO-developed "Fermentabag" described in AU-A-41605/85 (herein incorporated by reference) comprises an inner bag containing fermenting grape must and an outer bag containing cooling water. Both bags are then placed in and restrained by a rigid outer container. The 10% greater density of the grape must effectively forces all of the cooling eater in the outer bag to the top and thus the inner bag is in direct contact with the rigid outer container and is not cushioned or supported by the water containing outer bag. Futhermore, the inner bag is subject to internal carbon-dioxide gas pressure which effectively prevents the entry of oxygen by permeation through the inner bag walls.

More recently, a further development of the "Fermentabag", described in PCT/AUOO/01247 and published as WO 01/28889 Al, uses an outer bag supported by a rigid outer container to apply pressure via a pressurized fluid, to an inner bag containing wine grapes or grape must between the bags. The purpose is the assist in crushing the grapes to extract the juice, which is then fermented. In one embodiment the "inner bag is comprised of gas permeable sheet material to permit micro- oxygenation of the must". This is reportedly (Australian Financial Review Wed. 26/9/2001) made "from the same CSIRO-developed, multi-layer plastic material used in the fermenting bag. This material allows for specific amounts of air to be passed through the film to the wine and allows for a "micro-oxygenation" effect similar to that of an Oak barrel". There is no disclosure as to controlling the dissolved oxygen content of the outer bag fluid as a means of controlling the permeation of gas into the inner bag. There is also no disclosure as to the matching of densities of the outer bag fluid and the must. If the outer bag fluid is water, the extracted juice, being some 10%) higher in density, will displace it in the outer bag, removing liquid support of the inner bag by the outer bag.

Derwent Abstract Accession No. 71-77387S and JP 46041597 (Tokyo Nippon Yoki Kogyo K) 1971 discloses a synthetic resin vessel with a high oxygen permeation rate to be used to mature wine in less than 40 days of storage. This utilizes a "dry membrane" that is in direct contact with the air, rather than with oxygenated water.

The system for aseptic holding of fermentable liquids in flexible containers, as described in PCT/SE86/00292 and published as WO 86/07578 discloses "flexible containers which are immersed in water or another liquid. The surrounding liquid is kept in outer tanks made of concrete or plastic. Since the containers, when they are filled with liquid product are immersed in liquid, the loads acting on the container wall remain low". Also disclosed therein is the use of variable density supporting fluid to match the density of the stored liquid, temperature control of the stored contents by controlling the temperature of the surrounding supporting fluid, use of oxygen-impermeable material in the walls of the flexible container and the suppression of dissolved oxygen in the supporting fluid, as a means to reducing or preventing oxidation of the contents. The use of a separate vent port in the container to remove gas during filling, the use of an internal supporting element to prevent blocking of the fill/empty port by the flexible container wall material and the use of a ballast weight or float to control the attitude of the bladder in the tank, are not disclosed.

It is to be understood that the foregoing recitation of prior art should not be regarded as any form of statement or admission that it comprises a part of the common general knowledge in the art.

Disclosure of the Invention

Accordingly, the invention provides a method for storing liquid foods and wines that are not subject to anaerobic bacterial infection, comprising an outer tank containing water, wine or any other supporting fluid, into which a liquid-tight empty bladder or bladders are first submerged, then filled with liquid food or any other liquid requiring storage. The system of our invention may be combined with a number of preferred features, specifically:

two closable ports are provided on each bladder for the attachment of hoses or valves, a fill/empty port and a vent port for venting any accidental overfill, gas or remaining head-space air

a means to control the attitude of a submerged bladder so that access is maintained to the aforesaid ports at all times and so that the maximum number of individual bladders can be incorporated into a tank in an orderly way

an internal support element or other means to prevent the walls of the bladder from drifting into and blocking off the port during emptying.

A means to control the permeation of oxygen through the bladder walls, from that which may be dissolved in the external supporting liquid and a means to prevent the loss of volatiles in the stored food, such as ethanol and/or certain flavour elements in the contained food.

In the case of wine, most suitably the rate of oxygen transmission into the bladder is to be controlled such that the combined rate of oxygen transmission from all sources is to be less than 40cc/litre of wine/yr. More suitably the combined rate of oxygen transmission should be less than 20cc/litre of wine/yr.

The rate of oxygen transmission through the bladder may be controlled in a number of ways. For example, at the lower limit the supporting liquid in the tank may not contain any significant level of dissolved oxygen, such as de-oxygenated water, alcohol or mixtures thereof. Oxygen scavengers such as sulphur dioxide may also be used to remove oxygen from the tank liquid.

The use of multi-layer co-extrusion for constructing the films of our bladders allows several individual material layers to be extruded together into a single film, to provide films with a desirable special mix of properties. For example, such a film can, at the same time, allow a controlled level of oxygen permeation (by means of a certain thickness of an oxygen control polymer layer or oxygen barrier layer such as ethylene vinyl alcohol), provide a barrier to solvent and flavour transfer such as is imparted by Nylon and be easy to fabricate into liquid-tight large bladders by providing inner seal layers of readily heat-sealable polyethylene. Such joins do not then require additional chemically aggressive adhesive for bonding the seams.

Where the membrane used for the pouch is comprised of multiple layers of plastics film it is preferred that at least one of such layers thus be a pre-set thickness of material which has low permeability to oxygen, a so-called oxygen barrier layer. For storage of wine, the oxygen permeability of the resulting composite, multi-layer membrane is to be less than 100 cc of pure oxygen/m²/24 hours at STP and 100% RH. More suitably its permeability will be less than 20 cc of pure oxygen (4 cc of air oxygen) /m²/24 hours at 100% RH. For a bladder with a total membrane surface area of 10m² in a tank liquid filled pure oxygen saturated water at STP, this equates to a maximum of about 200 cc of O₂ per 24 hours or 20.8 cc/litre of wine/year for a bladder containing 3,500 litres of wine.

Some oxygen barrier layer materials are moisture sensitive, so it may be desirable to add moisture barrier layers on each side of the oxygen barrier layer. It may also be desirable to comprise into the multi-layer membrane, a layer or layers of material which have low permeability to ethanol and/or volatile flavour compounds for wine or other stored liquid foods. Other layers may provide physical and chemical protection for the stored liquid food and it may be desirable to add reinforcing layers to mechanically strengthen the final composite membrane.

Additionally, we provide for optionally measuring and controlling the dissolved oxygen content of the supporting liquid in the tank, which allows adjustment of the rate of oxygen permeation into the liquid in the bladder for those foods requiring maturation.

Provision is also made for the optional addition of an Oak infuser bag, comprising a cloth bag containing toasted or plain Oak chips or sawdust.

Furthermore, by installing the outer tank and it's supporting liquid mostly below- ground, natural cooling and earth-sheltered insulation is afforded to the liquid within the bladders, because there is a low barrier to heat transfer trough the thin bladder walls. If additional cooling is required, it is a simple matter to re-circulate the tank liquid through a refrigeration tube heat exchanger or to utilize other direct cooling or heating means in the tank liquid, such as evaporative cooling and solar heating.

Such bladders can be used part-filled by partially collapsing them to remove any head-space and can be sized to store a wide range of grades and volumes of products in a single, low-cost water storage tank installation. They can also be constructed hygienically, so that no initial washing or other surface treatment is required, unlike the need to food-acid treat stainless steel tanks prior to each filling to suppress ferric ion formation. Furthermore, they can be economically disposed of after use, reducing the cost of cleaning labour, water and chemicals.

The advantages of utilizing an external, liquid-filled tank to support the bladders are significant. By fully submerging the bladders in external liquid of similar density to the bladder contents there is no load or stress in the bladder walls such as occurs in non-supported liquid pouches or in the extremities of box-supported liquid pouches from the internal static head of the contained fluid. By similar density, we mean a supporting fluid that is no more than 10% more dense or 5% less dense than the contents of the bladders.

Bladders that are suspended in a liquid inside a rigid tank are very well protected and not vulnerable to accidental damage. The greatest risk of accidental damage occurs when the bladder is first loaded into the tank. In order to reduce the risk of leaks due to snagging or abrasion, we have found it desirable to build up the wall of the bladder from a number of thinner plies, rather than one single thicker ply, so that damage to an outer ply does not cause the bladder to leak. This also aids oxygen barrier by providing at least one dry interface between the two films and also renders the bladder more flexible and easier to handle.

Especially important to our invention is the ability to use relatively thin films that can be quickly and reliably heat-fabricated into liquid-tight bladders. Furthermore the use of thin polymer membrane films rather than heavily reinforced, rubber or PNC-coated laminates allows these bladders to be made up of minimal weights of heat-sealable, no-taint polymers such as polyethylene and polyamide (Nylon).

Brief Description of the Drawings

Figure 1 shows an isometric view of an apparatus according to the invention

Figure 2 shows an isometric view of an alternative form of apparatus according to the invention

Figure 3 shows an isometric view of another alternative form of the apparatus according to the invention

Figure 4 shows an isometric view of a differently shaped bladder according to another alternative form of the apparatus of the invention. Detailed Description of the Drawings

Figure 1 show is a partially transparent view of a preferred embodiment of a bulk- storage bladder (1) installed in a wine, water or other liquid-filled tank (2), made of steel, plastic, concrete or composite resin material.

In this embodiment, the aforesaid bladder is provided with two ports detachably connected to a flexible fill-hose (13) and a flexible vent hose (12). On the top end of the fill hose (13) a stop valve (3) is fitted in a location that is easily accessible for the attachment of a pump (not shown) that may be used to fill or empty the bladder. On the end of this vent tube (12), or incorporated within it, is an optional one-way check valve (5) which can allow the continuous discharge of gas or excess liquid, without allowing the return of air back into the inside of the bladder.

In this embodiment, the means to control and maintain a generally upright attitude of the bladder in the tank is provided for by a metal (usually stainless steel) ballast weight (8) inserted into a pocket fabricated into the bladder and by an air-inflated flotation chamber (7) provided with an inflation valve and also fabricated into the bladder.

The bladder is first installed in the tank through the top tank access cover (10) in a collapsed and longitudinally folded condition, but with the ballast weight inserted and the floatation chamber inflated.

As the collapsed bladder is lowered into the liquid-filled tank, the ballast weight ensures that the bottom of the bladder remains at the lowest point, whereas the flotation chamber keeps the highest point of the bladder and the fill and vent hose ports at or near to the surface of the external liquid.

During filling of the bladders via the fill hose (13), it is necessary to continuously vent-off via the vent tube (12) any build up of pockets of gas, which may be in- solution and cause frothing, may arise due to residual fermentation, or be made up of air pumped-in with the liquid contents. Such gas, if not controlled both by maintaining the bladder in an upright attitude and by continuously venting it away, will otherwise accumulate in the bladder where it can disrupt the filling or accumulate in a fold of the part-collapsed bladder, causing it to roll over and sink the fill ports. Should this be allowed to happen, it can be very difficult, if not impossible to right the bladder without damaging it, due to the great mass and inertia of the liquid usually contained within .

Another important requirement is to prevent damage to the bladder by accidental overfilling. By providing the second (vent) port and hose (12) any excess liquid can be discharged outside the tank, rather than internally pressurizing and perhaps tearing open, the bladder.

For trouble-free emptying of the bladders, a fluid-conducting spacer and film support element (4) is provided within the bladder and is restrained by top (21) and bottom tethers, which are trapped within the end-seams during fabrication of the bladder.

Located adjacent to and directly behind the port attached to hose (13) this prevents the bladder wall-film drifting into and blocking the port and hose (13) during emptying.

This is a natural result of the Bernoulli effect, where static pressure is lower in regions of flow. The flow in the vicinity of the port causes a pressure drop there, which pulls the film into the port opening. Accordingly, this fluid-conducting spacer provides a flow path flow to the fill/empty port, even when the bladder is close to empty and the film is being sucked strongly together and towards the port.

If Oak (or any other wood) infusion is to be carried out, the bladder can be provided with a porous, generally filter-cloth infusion bag (20) in which wood chips or sawdust can be contained. In this embodiment, the infusion bag (20) is closed with plastic ties, which are also sealed into the end seams of the bag to install and hold-down the sack into the liquid. Such a bag can be fitted during bladder fabrication, or a part of the end seams can be left open for later fitting and sealing-in of a bag. It may be desirable to move the bladder about in a tank, especially when many of them are to be installed in a large, open-top tank. For that purpose a reinforced ring (11) is welded into the bladder material adjacent to the flotation chamber and a through-hole is punched. The bladder may be tethered with a rope or wire tether, or pulled about with a boat-hook on the end of a long handle.

In case it is desired to further tether or otherwise restrain the bladder, or to provide other convenient locations from which to move the bladder about or to help retrieve an emptied bladder, further reinforced tether points are provide on the bladder at corners (9) and (10).

At all times during filling, emptying and storage of the bladders, it is necessary to keep a sufficient level (14) of supporting liquid in the outer tank, to keep any bladders fully submerged. Otherwise they may be easily damaged by the internal partly- unsupported weight of the contents. In this embodiment, this is achieved by means of an electrical level detection switch (15), which can operate a pump to add additional supporting liquid through one of the tank ports (16) or (17), whenever the liquid level falls below the pre-set signal level.

Temperature control and/or oxygenation of the tank liquid can be done by circulation through an external pump circuit, with a heating/cooling/aeration device in this flow circuit (not shown). Typically water may be pumped into the tank port (16) and discharged through port (17) or vice- versa.

Finally, tank liquid temperature or dissolved oxygen monitoring either within the aforesaid flow circuit, or separately by introducing a measuring probe into the tank liquid by means of the measuring-port (18).

Figure 2 shows a partially transparent view of another embodiment of the invention, comprising a bulk-storage bladder (1) of a different design, installed in a wine, water or other liquid-filled tank (2), also made of steel, plastic, concrete or composite resin material. In this embodiment, the bladder (1) is provided with two ports at (5) and (6), at each end of the bladder side-wall. These are detachably connected to rigidly mounted through ports in the outer tank. In this embodiment the filling and emptying would be done through port (6) and the venting through port (5) and the bladder is held upright by it's port connections.

If desired, additional bladder restraint can be provided by means of the attachment points (3) and (4), also rigidly mounted to the tank side-wall.

Such an arrangement fully controls the attitude of the bladder and maintains a convenient access point for fill and vent pipe connection, without having to open the outer tank. As previously supporting liquid level and recirculation is provided by means of the tank inlet port (7) and the tank outlet port (8).

An advantage of this embodiment is that an internal fluid-conducting spacer element may not be required, due to the gravity emptying from the bottom discharge point (6) of the bladder.

A disadvantage of this embodiment is that the tank must be emptied before access can be gained to fit new bladders, making it suited for use only with a relatively small tank fitted with only a few bladders.

Figure 3 shows yet another embodiment of the invention, wherein the bladders (1) are constructed with one side gusseted-in (9) before cross seaming to close the top and bottom ends.

When filled, bladders constructed like this will assume a pie-wedge shape, which can be designed to close-pack radially, into a closed circular tank (2). In this embodiment, the bladders are connected via side ports (5) and (6), to a vertically directed top vent tube (4) and a radially directed fill/empty tube (3), both of which penetrate the outer tank wall, for easy external access.

The tank is maintained full by a liquid supply (10) connected to a cistern type float valve. For emptying or re-circulation, the tank liquid can be drawn out via port (7). When filling pre-installed empty bags, excess tank liquid can be discharged via a U- trap (8), which isolates the liquid in the tank, from the outside atmosphere, should that be desirable, for example when it is desired to minimise dissolved oxygen in the tank fluid.

Figure 4 shows a bladder (1) shaped by double gusseting (9) and (3), to have a generally rectangular cross-section when filled. In this embodiment, designed for close packing bladders into a large in-ground outer tank of rectangular cross-section (not shown). The bladder ports (6) and (7) are located on the top of the bladders and the fill port would generally be connected to a rigidly-mounted long fill-pipe (not shown) which may be connected with a number of adjacent bladders.

In this embodiment, an internal fluid conducting strip (4) is tethered (2) only into the top seam and is made to hang down into the bladder contents by means of a ballast weight (5). A further ballast weight (8), fitted to the base of the bladder, ensures it retains an upright attitude in the tank, as it is filled or emptied.

It is to be understood that the word comprising as used throughout the specification is to be interpreted in its inclusive form ie. use of the word comprising does not exclude the addition of other elements.

It is to be understood that various modifications of and/or additions to the invention can be made without departing from the basic nature of the invention. These modifications and/or additions are therefore considered to fall within the scope of the invention.

Claims (22)

Claims

1. A container for bulk storage of liquid foods and wine comprising:

a liquid-tight bladder to contain the stored liquid having a filling port for filling and emptying and a venting port for venting any overfill, gas or head space air,

- a tank containing supporting liquid of similar density to the stored liquid in the bladder,

- control means to control the attitude of said bladder,

- support means to prevent the walls of said bladder from drifting into and closing off the filling port during emptying.

2. The container of claim 1 wherein the bladder walls are made up of two or more physically separate plies.

3. The container of claim 1 or claim 2 wherein the support means comprises a fluid conducting element.

4. The container of claim 1 or claim 2 wherein the bladder is provided with the filling port low in the side-wall for gravity discharge of it's contents.

5. The container of any one of claims 1 to 3 wherein the means to control the attitude of the bladder in the outer tank, comprises a ballast weight and/or the support means.

6. The container of any one of claims 1 to 4 wherein the means to control the attitude of the bladder in the outer tank, comprises a flotation chamber or attachment.

7. The container of any one of claims 1 to 3 wherein the means to control the attitude of the bladder in it's tank, comprises a ballast weight and a flotation chamber or attachment.

8. The container of any one of claims 1 to 3 wherein the means to control the attitude of the bladder in the outer tank, comprises a rigid connection to at least one bladder port.

9. The method of any one of claims 1 to 3 wherein the means to control the attitude of the bladder in the outer tank, comprises a rigid connection to both bladder ports.

10. The method of any one of claims 1 to 9 wherein the material of construction of the bladder includes a component to control the rate of permeation of dissolved oxygen from the supporting fluid outside the bladder into the stored liquid within the bladder.

11. The method of any one of claims 1 to 10 wherein additional means is provided to measure and control the dissolved oxygen content of the supporting fluid in the outer tank.

12. The method of any one of claims 1 to 11 wherein the temperature of the supporting fluid is controlled.

13. The method of any one of claims 1 to 11 wherein the bladders are provided with a wedge-shaped cross-section, to close-pack into a circular tank.

14. The method of any one of claims 1 to 11 wherein the bladders are provided with a rectangular-shaped cross-section, to close-pack into a rectangular tank.

i 15. The container according to any one of the preceding claims wherein the combined oxygen transmission characteristics of the tank, bladder and any other air or fluid dissolved oxygen sources are such that the total rate of oxygen transmission into the stored liquid is less than 40 cc/litre of stored liquid/yr.

16. The container according to claim 15 wherein the bladder comprises material with low oxygen permeability.

17. The container according to claim 15 or claim 16 wherein the bladder has walls comprising multiple layers of plastic film.

18. The container according to claim any one of the claims 15 to 17 wherein the bladder has been formed by heat sealing the bladder walls together.

19. The container according to any one of claims 15 to 18 wherein the bladder walls comprise at least three layers of plastic film with at least one of the layers comprising an oxygen barrier material.

20. The container according to claim 19 wherein the bladder walls comprise: - an external reinforcing layer and ethanol barrier layer at least one oxygen barrier layer - an internal reinforcing layer and ethanol barrier layer an inner water seal layer.

21. The container according to claim 19 wherein, the external reinforcing layer and ethanol barrier comprises polyamide, at least one oxygen barrier layer comprising one of ENOH, PNDC or metallized PET and the inner water seal layer comprises polyethylene.

22. The method of any one of claims 1 to 16, wherein the bladder is fitted with » an internal infusion bag or other solid or porous element that contains oak chips, sawdust or extract, to enable the imparting of oak characters to the stored liquid.