WO2001056904A1

WO2001056904A1 - Beverage infusion packages and materials therefor

Info

Publication number: WO2001056904A1
Application number: PCT/GB2001/000270
Authority: WO
Inventors: John Edward Rose
Original assignee: J R Crompton Limited
Priority date: 2000-02-02
Filing date: 2001-01-25
Publication date: 2001-08-09
Also published as: AU2001230332A1; GB0002339D0

Abstract

A beverage infusion package comprising a bag of a porous, fibrous tissue containing a beverage precursor material (e.g. coffee) wherein the tissue has laminated thereto a barrier film of a water soluble material, e.g. poly(vinyl alcohol). The barrier film serves to reduce, inhibit or prevent oxidation or other deterioration of the beverage precursor material. There is thus no need to enclose the package in a foil wrapper to maintain the beverage precursor material 'fresh'. Moreover the barrier film is water soluble and dissolves during infusion of the package.

Description

BEVERAGE INFUSION PACKAGES AND MATERIALS THEREFOR

The present invention relates to a beverage infusion packages (e.g. tea bags, coffee bags and the like) and other package having a content which needs to be kept "fresh" and which is to be "treated" with water whilst within the package. The invention also relates to a porous, fibrous web materials for use in producing such packages.

Beverage infusion packages such as tea bags comprise a particulate beverage precursor material, e.g. tea leaves or ground coffee, in a bag, sachet, pouch or the like (all conveniently referred to herein as a bag) of a porous, fibrous (usually cellulosic) material. This material typically has a basis weight of 10 to 30 g m^"2 and is often referred to as "tissue" or "tissue paper". The tissue may be of the "heat seal" or "non- heat seal" type

To produce a beverage, the package is infused with hot water. This may be done, for example, by immersing the package in hot water, pouring hot water onto the package, or heating water and the bag in a microwave oven.

The infusion package may be of a size, and contain an amount of the beverage precursor material, so as to be intended for producing a single cup of the beverage. Alternatively the package may be of a "catering size" and as such intended to produce a multitude of cups of the beverage. Such a "catering size" package may for example contain ground coffee as the beverage precursor material and be used in a commercial coffee - making machine.

A disadvantage of such packages is that, unless special precautions are taken, there may be oxidation or other deterioration (e.g. loss of flavour components by volatalisation) of the beverage precursor material during storage of the package. To this end, it has been previously been the practice, particularly for "catering size" infusion packages, to enclose the package in a sealed foil wrapper within which may be provided an atmosphere of nitrogen. Whilst such measures do indeed avoid oxidation and other deterioration of the beverage precursor material during storage, there is the disadvantage that the manufacturer of the wrapped package has to carry out the operations of, firstly, producing the package itself and, secondly enclosing it in the foil wrapper. This latter step is not only an additional step in the production process but results in a much reduced production rate and increase in material costs. There is the further disadvantage that the outer foil wrapper does need to be removed before the infusion package can be used. Although removal of the wrapper is a simple operation, it is nevertheless regarded as a time-consuming step particularly in catering establishments where speed may be of the essence in producing beverages. Furthermore if the package is removed from its wrapper and not immediately used then the aforementioned problems of oxidation and other deterioration of the beverage precursor material once again occur. An additional disadvantage is that the foil wrapper has an impact in the environment.

It is therefore an object of the present invention to obviate or mitigate the above mentioned disadvantages.

According to a first aspect of the present invention there is provided a beverage infusion package comprising a bag of a porous, fibrous tissue containing a beverage precursor material wherein said tissue has laminated thereto a barrier film of a water soluble material.

The invention also provides, in a second aspect, a material for use informing the bag of a beverage infusion package, said material comprising a porous fibrous tissue having laminated thereto a barrier film a water soluble material.

The barrier film serves to reduce, inhibit or prevent oxidation or other deterioration of the beverage precursor material by virtue of providing a substantially gas impermeable layer. If desired, the package may contain an atmosphere of nitrogen (or other non-toxic inert gas) which is retained in the package by virtue of the gas impermeability of the barrier film and thus acting further to prevent oxidation or other deterioration. The barrier film is however water soluble and dissolves during infusion of the package so that the film is "automatically" removed allowing the beverage to be infused in the normal way.

Thus it will be appreciated that the present invention provides an infusion package which allows the beverage precursor material to be maintained "fresh" and which can be used without the need to remove the package from an outer foil wrapper. In addition, the water-soluble barrier film does not detract from the normally expected infusion (brewing) rate nor form the normal taste, appearance or "mouth feel" of the infusion. Additionally, the film reduces the amount of "dust" (of the beverage precursor material) which would otherwise be lost from the package during its storage.

The barrier film should be of a non-toxic food grade material which has the required gas permeability and water solubility properties.

The film may, for example, have a thickness of 1 to 70 microns, more preferably 1 to 15 microns, and most preferably 1 to 10 microns.

Preferably the film is insoluble in cold water but dissolves in water at a temperature above 70°C.

It is preferred that the barrier film is of poly(vinyl alcohol).

The poly(vinyl alcohol) is preferably one having a degree of hydrolysis of at least 60%, more preferably at least 80%, and most ideally at least 85%. The degree of hydrolysis may, for example, be 95% to 99%.

Preferably also the poly(vinyl alcohol) is one for which a 4% aqueous solution at 20°C has a viscosity of 5 to 100 mPa.s (preferably 25 to 30 mPa.s). The molecular weight of the poly(vinyl alcohol) may for example be 20,000 to 200,000. Poly(vinyl alco 10I) has excellent flavour retaining properties due to its low gas permeability (to oxygen, nitrogen and carbon dioxide) although this permeability is dependent on the degree of hydrolysis of the poly(vinyl alcohol) and the relative humidity of the environment to which the film is subjected. Generally the higher the degree of hydrolysis the lower will be the gas permeability of the film for a given relative humidity. For a given degree of hydrolysis an increase in humidity will increase the gas permeability. Permeability of the film may also be controlled by inclusion of appropriate additives.

Suitable examples of poly(vinyl alcohol) for use in the invention are available from Hoechst under the trade mark Mowiol. Particularly suitable grade are Mowiol 26-88 and Mowiol 28-99, in which designations the number proceeding the hyphen is the viscosity, in mPa.s, of a 4% solution in water at 20°C and the number subsequent to the hyphen is the degree of hydrolysis. Also suitable for use in the invention is Airvol 528 (88% hydrolysed) and Airvol 125 (99% hydrolysed).

The film may be "pre-formed" (i.e. produced separately of the tissue) and then laminated thereto. Such a film maybe produced by traditional methods such as film blowing and casting, using the materials disclosed in GB-A-2 291 831 obtained from Environmental Polymers Ltd. This film may be laminated to the tissue web by "hot welding" or by "solvent bonding.

The film may be laminated by passing it through a suitable heated calender stack to hot weld the components to form a composite.

The temperature of the unit would depend on a number of factors

* The degree of hydro lyses of the PVOH film.

* The thickness of the PVOH film

* The speed of the lamination process

* The "nip" pressure applied to the calender stack rolls. Typically at a line speed of 240 mtrs/min and a linear nip pressure of between 5 to 50 Kg/cm the calender stack would be heated to between 180°C to 240°C depending on the degree of hydrolysis.

The product could alternatively be laminated by applying the above pressure range to the composite in the presence of a fine mist of water (warm or cold depending on degree of hydrolysis). This would be applied between the paper and PVOH film just prior to the in-going nip of the pressure rolls and act as an adhesive aid by causing the contact surface of the PVOH to become partially mobile and tacky.

Alternatively the film may be formed in situ on the tissue, either as the latter is produced on the paper-making machine or in a separate operation post-manufacture of the tissue.

The in situ formation of the film may be effected by a coating technique such as

Extrusion Coating Coextrusion Coating

> Gravure Coating

> Blade Coating

> Roll Coating

> Air I nife Coating"

The laminate may be produced by passing the tissue through a unit that is suitable for applying a "functional coating".

The term "functional coating" refers to coatings other than traditional pigmented coatings for printed papers. The functional properties that the coatings can impart to paper include appearance, protection and control of surface properties. The properties are by-and-large derived from the film properties of the polymeric materials employed.

The success of functional coating generally depends on the uniformity of the coating. A continuous "film" is particularly important for barrier properties.

The selection of the coating method relies on a number of factors such as the strength, wettability, porosity, density and smoothness of the tissue and the formulation of the coating such as total solids, type of solvent (water or organic), surface tension and viscosity.

The prefeired method, other than laminating with a pre-formed film, is extrusion coating which is sometimes refereed to as extrusion laminating.

This method briefly involves mixing the coating formulation via an extruder unit and metering the homogeneous mixture under pressure through a slotted die to form a "free film". This "free film" is then drawn down to the desired thickness by the stretching affect of running the base tissue web at a higher speed than the exit speed of the polymer film. The film is then subsequently combined with the tissue substrate by passing the material through a chilled metal roll and a rubber-covered pressure roll.

The extrusion coating method can if desired achieve very low lay down rates of high molecular weight polymers which makes them ideal for coating food - packaging papers.

The tissue will generally have a basis weight of 10 to 50gm^" , more typically 10 to 30 gm^"2' e.g. 10-20 gm^"2.

The tissue may be of the "heat seal" or "non-heat seal" type. "Heat seal" tissue comprises two or more layers wet-laid in succession one on top of the other. One layer contains only cellulosic fibres and the other (or at least one other layer) incorporates thermoplastic fibres. The "heat seal" tissue may for example be that produced by J.R. Crompton Ltd under the name SUPERSEAL (Registered Trade Mark). Alternatively the "heat seal" tissue may be as disclosed in WO- A- 9836128 (J.R. Crompton). A beverage infusion package is produced from such tissue by forming the bag such that layers of the tissue incorporating thermoplastic fibres are juxtaposed and then heat sealed. With such a "heat seal" tissue, the water-soluble film will generally be provided on the side of the tissue incorporating the thermoplastic fibres and as such will be on the inner side of the bag containing the beverage precursor material.

"Non-heat seal" tissue generally (but not necessarily) comprises a single wet- laid layer of cellulosic fibres and in some instances approved synthetic fibres such as viscose rayon. Alternatively the "non-heat seal" tissue may be produced by laying successive layers (possibly of differing composition) one on top of the other (e.g. as described in WO-A-9601839). In the case of "non-heat seal" tissue, the water soluble film may be provided either on the outer surface or inner surface of the bag containing the beverage precursor material.

The tissue may have a degree of "openness" in its structure commensurate of that with conventional tissues used for forming beverage infusion packages. The water-soluble film does however allow the tissue to have a significantly more open structure. With a tissue of more open structure, the laminate of the tissue and water- soluble film would be more transparent (than for a tissue of conventional "openness"). Furthermore, a faster infusion would be obtained and it would be possible to use smaller infusion material particle sizes which would have a beneficial cost impact for the tea/coffee packer.

Although the invention has been described with specific reference to beverage infusion bags it will be appreciated that it may equally be applied to other packages having an outer bag of tissue and a content which needs to be kept "fresh" and which is to be "treated" with water whilst within the package.

Claims

1. A beverage infusion package comprising a bag of a porous, fibrous tissue containing a beverage precursor material wherein said tissue has laminated thereto a barrier film of a water soluble material.

2. A package as claimed in claim 1 wherein the film has a thickness of 1 to 70 microns.

3. A package as claimed in claim 2 wherein the film has a thickness of 1 to 15 microns.

4. A package as claimed in 3 wherein the film has a thickness of 1 to 10 microns.

5. A package as claimed in any one of claims 1 to 4 wherein the barrier film is cold water insoluble but dissolves in water at a temperature above 70°C.

6. A package as claimed in any one of claims 1 to 5 wherein the barrier film is of poly(vinyl alcohol).

7. A package as claimed in claim 6 wherein the poly(vinyl alcohol) has a degree of hydrolysis of at least 60%.

8. A package as claimed in claim 7 wherein the poly(vinyl alcohol) has a degree of hydrolysis of at least 80%.

9. A package as claimed in claim 8 wherein the poly(vinyl alcohol) has a degree of hydrolysis of at least 85%.

10. A package as claimed in any one of claims 6 to 9 wherein the poly(vinyl alcohol) is one for which a 4% aqueous solution at 20°C has a viscosity of 25 to 30 mPa.s.

11. A package as claimed in any one of claims 1 to 10 wherein the tissue has a basis weight of 10 to 50 gm^"2.

12. A package as claimed in claim 11 wherein the tissue has a basis weight of 10 to 20 gm^"2.

13. A package as claimed in any one of claims 1 to 12 wherein the tissue is of the "heat seal" type.

14. A package as claimed in any one of claims 1 to 12 wherein the tissue is of the "non-heat seal" type.

15. A package as claimed in any one of claims 1 to 14 wherein the beverage precursor material is tea.

16. A package as claimed in any one of claims 1 to 14 wherein the beverage precursor material is coffee.

17. A material for use in forming the bag of a beverage infusion package, said material comprising a porous fibrous tissue having laminated thereto a barrier film of a water soluble material.

18. A material as claimed in claim 17 wherein the film has a thickness of 1 to 70 microns.

19. A material as claimed in claim 18 wherein the film has a thickness of 1 to 15 microns.

20. A material as claimed in 19 wherein the film has a thickness of 1 to 10 lOmicrons.

21. A material as claimed in any one of claims 17 to 20 wherein the barrier film is cold water insoluble but dissolves in water at a temperature above 70°C.

22. A material as claimed in any one of claims 17 to 21 wherein the barrier film is of poly(vinyl alcohol).

23. A material as claimed in claim 22 wherein the poly(vinyl alcohol) has a degree of hydrolysis of at least 60%.

24. A material as claimed in claim 23 wherein the poly(vinyl alcohol) has a degree of hydrolysis of at least 80%.

25. A material as claimed in claim 24 wherein the poly(vinyl alcohol) has a degree of hydrolysis of at least 85%.

26. A material as claimed in any one of claims 22 to 25 wherein the poly(vinyl alcohol) is one for which a 4% aqueous solution at 20°C has a viscosity of 25 to 30 mPa.s.

27. A material as claimed in any one of claims 17 to 26 wherein the tissue has a basis weight of 10 to 30 gm^"2.

28. A material as claimed in claim 27 wherein the tissue has a basis weight of 10 to 20 gm^"2.

29. A material as claimed in any one of claims 17 to 28 wherein the tissue is of the "heat seal" type.

30. A material as claimed in any one of claims 17 to 29 wherein the tissue is of the "non-heat seal" type.

31. A method of producing a material for use in forming the bag of a beverage infusion package, said method comprising preparing a laminate of a porous fibrous tissue and a barrier film of a water soluble material.

32. A method as claimed in claim 31 wherein the material is as defined in any one of claims 17 to 30.

33. A method as claimed in claim 31 or 32 wherein the laminate is prepared by laminating to said tissue a pre-formed film of the water soluble material.

34. A method as claimed in claim 33 wherein laminating is effected by "hot welding" or by "solvent bonding".

35. A method as claimed in claim 34 wherein lamination is effected by "hot welding" by passing the tissue and the pre-formed film through a heated calender.

36. A method as claimed in claim 31 or 32 wherein the laminate is prepared by forming the film in situ on the tissue.

37. A method as claimed in claim 36 wherein the film is formed by Extrusion Coating, Coextrusion Coating, Gravure Coating, Blade Coating, Roll Coating and Air Knife Coating.