EP0753468A1

EP0753468A1 - Beverage container with means for frothing the beverage and method of frothing the beverage

Info

Publication number: EP0753468A1
Application number: EP95201112A
Authority: EP
Inventors: Antien Frances Zuidberg; Albertus Prins
Original assignee: Whitbread PLC; Whitbread and Co Ltd; Heineken Technical Services BV
Current assignee: Whitbread PLC; Heineken Supply Chain BV
Priority date: 1995-04-28
Filing date: 1995-04-28
Publication date: 1997-01-15

Abstract

The invention is directed to a system for the controlled enhancement of release of gas bubbles from beverages, said system comprising a microporous membrane having pores of 20 to 100 µm in diameter at distances from each other ranging from 2.5 to 15 times the diameter of the pores, the outher surface of the membrane being substantially hydrophylic when in contact with the beverage and the walls of the pores being hydrophobic.

Description

The present invention is directed to the controlled enhancement of the release of gas from beverages, more in particular from carbonated beverages, such as beer.
When dispensing carbonated beverages from either tap or from cans there tends to be a considerable difference in the type and quality of the foam that is produced. Especially with beer this is important as the consumer has very distinct and high demands on the quality of the head of foam.
Recently the interest in systems for dispensing beverages, such as beer, from cans has grown considerably. Various proposals have been made for systems that produce ber from cans with an improved head of foam.
In WO-A 91/07326 a system has been described consisting of a closed pressurized can provided with a hollow insert located in the container. The insert contains gas under pressure that upon opening of the container is jetted into the liquid. This jet causes the evolution of small bubbles of gas, generating further bubbles, so that as the beer is dispensed from the container a good head of foam is generated. Other systems provide for a hollow container from which a mixture of gas and beer is jetted.
These systems have some disadvantages which severely limit their use. In the first place it is to noted, that they are very susceptible to overflowing when the temperature is too high, that is to say at temperatures above about 15°C.
Also the foaming may be so massive, that only low carbonated ales can be packed in this way. Finally the inserts may require larger cans, resulting in a cost increase of the packaging, transport and storage.
Another approach to the improvement of the foaming of beverages when dispensed from a container is the use of so-called 'active surfaces'. WO-A 93/04945, the contents of which is incorporated herein by way of reference, discloses the use of a nucleation promoting agent in a container, said nucleation promoting agent being a material capable of carrying entrapped stabilised gas bubbles in contact with the beverage. According to the description this system comprises either a sheet of Tyvek, or a sheet of polytetrafluoroethylene, which is in contact with the beverage and is incorporated in the container, for example in the from of a folded sheet held in the interior of the container.
In WO-A 94/16967, the contents of which is incorporated herein by way of reference, another system for the use of active surfaces has been disclosed, namely based on contact between the beverage and the active surface only when the container is opened and the content thereof is poured. As active surfaces various systems have ben disclosed, such as materials having a rough surface, glass, sand, etc. Also it is mentioned that an active surface may comprise a material having a pore size of 5 to 250 µm, with a hydrophobic cavity and a hydrophylic outer.
The invention aims at providing an improved system for enhancing the release of gas from a beverage, based on the use of active surfaces (either in continuous contact with beer, as in WO-A 93/04945, or kept separate therefrom as in WO-A 94/16967).
The invention is based on the insight in the phenomena of bubble generation and more in particular on lengthy scientific studies on the theories behind bubble generation, especially from carbonated beverages, such as beer.
The invention resides in a system for the controlled enhancement of release of gas bubbles from beverages, said system comprising a microporous membrane having pores of 20 to 100 µm in diameter at distances from each other ranging from 2.5 to 15 times the diameter of the pores, the outher surface of the membrane being substantially hydrophylic when in contact with the beverage and the walls of the pores being hydrophobic.
The microporous membrane is based on a plastic material having hydrophobic properties, the outer surface of which may have been treated to become hydrophylic. Preferably the material of the microporous membrane is selected from the group of polyamides, polyolefins, styrene polymers, polyesters and thermosetting resins. Treatment of the outer surface of the membrane, if necessary, can be carried out in a manner known in the art, for example by oxidising the surface or by reaction of surface groups with suitable hydrophylic compounds. Some polymers possess sufficient hydrophilicity by itself.
The hydrophylic properties can be determined on the basis of the contact angle of water or of the beverage on the surface. In case the contact angle is smaller than 90° the surface has hydrophobic properties and a contact angle larger than 90° indicates hydrophylic properties.
The structure of the system for the controlled enhancement of foaming can be selected from a wide range of possibilities. In the most simple form it may consist simply of a sheet of a membrane having the required pore structure and surface properties. The material can be present in the container in various ways, such as a lining of the wal or the top of the container, as a folded sheet being held in place by a clip, or is some sort of separate compartment, where it comes into contact with the beverage after opening.
The pores in the membrane may go through the membrane, and in that situation it is preferred that both surfaces of the membrane are hydrophylic. In another embodiment the pores may be closed on one end of the membrane, either because they do not go through the material, or because the membrane is covered on one side with a substantially gas-impermeable material.
The pores can be provided in the membrane during production thereof, for example by providing a sufficiently dense woven material, wherein the interspaces between the fibres of the woven material provide the pores. In the alternative, and this is preferred, the membrane consists of a sheet of a substantially gas-impermeable material, which is provided with pores during or after production of the sheet, for example by the use of laser beams. The diameter and the distance of the pores can easily be controlled in this way. It is preferred, that the diameter of all pores is substantially the same over the whole surface of the membrane as this improves the homogeneity of the foam produced.
The distance of the pores is determined as the heart-to-heart distance of the pores. Preferably the pores are distributed over the surface of the membrane in a regular pattern, whereby it is remarked that the nature of the pattern is not very critical. Essential are especially the distances between the pores, which should not be outside the ranges given, as otherwise the foaming behaviour and the structure of the foam obtained are insufficient.
In a preferred embodiment of the invention the system comprises an enclosed gasreservoir having substantially hydrophobic properties and at least one membrane, said membrane having pores of 20 to 100 µm in diameter at distances from each other ranging from 2.5 to 15 times the diameter of the pores, the outher surface of the membrane being substantially hydrophylic when in contact with the beverage and the inner surface and at least part of the walls of the pores being hydrophobic, whereas said gasreservoir comprises a matrix of porous, preferably hydrophobic material.
It has been found that a structure consisting of, on the one hand a membrane having the specified structure and properties, and on the other hand an enclosed gas reservoir provides an excellent, controlled enhancement of the foaming.
The porosity of the matrix of porous material ranges from 5 to 95 vol.%, preferably from 50 to 75 vol.%.
Preferably said gasreservoir is based on a matrix-material selected from the group of woven and non-woven plastic fibre material, or porous ceramic materials.
The system may be constructed in various ways, for example as a flat structure, whereby the gas reservoir is covered on one side by the membrane, whereas on the other side either a membrane or a substantially gas impermeable material is present.
The materials used in this specific embodiment of the invention for the membrane and the way in which the system is present in the container are substantially the same as described in relation to the most simple embodiment of the system of the invention.
The invention is now elucidated on the basis of the figure, wherein in figure 1 a multilayer membrane is shown. In figure 2 a schematic view of the outer membrane of figure 1 is given.
In figure 1 the multilayer membrane consists of two outer membranes having a hydrophylic side and a hydrophobic side, with pores of 30 µm diameter. The shortest interval distance between the pores is 125 µm, and the number of pores is about 6400 pores/cm². The pores walls are also hydrophobic.
Wedged between the two hydrophobic sides of the outer membranes is the hydrophobic gasreservoir, in this case a porous hydrophobic membrane. In order the prevent leakage of liquid, the membranes have been sealed at the edges, resulting in a pouch-like structure.
Figure 2 gives a schematic view of the outer membranes of figure 1, the pores and the pattern of the pores being clearly visible. In this figure 1 denotes the outer membrane of figure 1, 2 indicates the hydrophylic side and 3 designates the pores having hydrophylic walls.

Claims

System for the controlled enhancement of release of gas bubbles from beverages, said system comprising a microporous membrane having pores of 20 to 100 µm in diameter at distances from each other ranging from 2.5 to 15 times the diameter of the pores, the outher surface of the membrane being substantially hydrophylic when in contact with the beverage and the walls of the pores being hydrophobic.
System according to claim 1, wherein the microporous membrane is based on a plastic material having hydrophobic properties, the outer surface of which has been treated to become hydrophylic.
System according to claims 1 or 2, wherein the material of the microporous membrane is selected from the group of polyamides, polyolefins, styrene polymers, polyesters and thermosetting resins.
System according to claim 1-3, said system comprising an enclosed gasreservoir having substantially hydrophobic properties and at least one membrane, said membrane having pores of 20 to 100 µm in diameter at distances from each other ranging from 2.5 to 15 times the diameter of the pores, the outher surface of the membrane being substantially hydrophylic when in contact with the beverage and the inner surface and at least part of the walls of the pores being hydrophobic.
System according to claim 4, wherein the gasreservoir comprises a matrix of porous material.
System according to claim 4 or 5, wherein the porosity of the matrix ranges from 5 to 95 vol.%, preferably from 50 to 75 vol.%.
System according to claim 4-6, wherein the gasreservoir is based on a material selected from the group of woven and non-woven plastic fibre material, or porous ceramic materials.
System according to claim 4-7, wherein the at least one side of the gasreservoir is enclosed by the membrane and at least one other side is enclosed by a substantially gas-impermeable material.
System according to claim 4-8, wherein at least two sides of the gasreservoir are enclosed by a membrane.
System according to claim 1-9 in the shape of a flat, optionally folded material, a lining for a can or an insert for a capsule.
Method of the controlled enhancement of release of gas bubbles from beverages, said method comprising contacting the beverage with at least one system according to claims 1-10.
Method according to claim 11, wherein the system is submerged in the beverage.
Method according to claim 11, wherein the beverage comes in contact with the system during the pouring of the beverage from a container.
Pressurised, sealed container of gasified beverage, comprising gasified beverage and at least one system for the controlled enhancement of release of gas bubbles from beverages according to claim 1-10.