GB2491007A

GB2491007A - Inclusion for controlling or modifying the atmosphere in packaging comprising reactive material within a semi-permeable envelope

Info

Publication number: GB2491007A
Application number: GB1207858.0A
Authority: GB
Inventors: John Hirst; Nigel Parker
Original assignee: EMCO PACKAGING SYSTEMS Ltd
Current assignee: EMCO PACKAGING SYSTEMS Ltd
Priority date: 2011-05-18
Filing date: 2012-05-04
Publication date: 2012-11-21
Anticipated expiration: 2032-05-04
Also published as: GB201207858D0; GB201108336D0; WO2012156685A2; WO2012156685A3; GB2491007B

Abstract

The inclusion comprises fill material 18 that reacts with water vapour to generate oxygen, and absorb or generate carbon dioxide, within an envelope 10. The envelope comprises a permeable support layer 12 laminated to a water vapour control layer 14. The water vapour control layer 14 is impermeable to liquid water, but permeable to water vapour and gases, and comprises a 10-20 Âµm thick polyamide or polyethylene film. The preferred support layer 12 is non-woven polyethylene fabric. Preferably the reactive fill material 18 comprises sodium carbonate peroxyhydrate, calcium bentonite clay or zeolite, sodium chloride, and sodium carbonate or sodium hydrogen carbonate and citric acid. The inclusion is used in modified atmosphere and controlled atmosphere packaging systems, for food.

Description

I

PACKAGING INCLUSION FOR CONTROLLING OR MODIFYING THE

ATMOSPHERE IN PACKAGING

Field of the Invention

The invention relates to a combined oxygen generating and carbon dioxide absorbing or generating packaging inclusion, in the form of a gas permeable envelope, containing a water vapour activated mixture.

Description of the Related Art

The of rapid expansion of retail convenience foods into a wide array of ready to eat' and ready to cook' fresh and thus relatively short shelf life products represents a still rapidly growing market, representing a range of packaging formats.

The majority of these packaging formats, however, rely on either modified atmosphere (MA), or to a lesser, but growing extent, controlled atmosphere (CA) packaging systems.

Modified Atmosphere Packaging (MAP) includes: -a hermetic pack closure, gas permeable packaging materials with gas transmission rates, which, in concert with the respiratory activity of the product, will allow a pack atmosphere of a predetermined composition to be established, known as an Equilibrium Modified Atmosphere (EMA), usually within the range 5% -10% 02, 5% -10% CO2 and 80% -90% N2, assisted on occasion by the option of partial replacement, at the time of packing, of the ambient atmosphere within the pack, by a pack atmosphere with a composition approaching, or matching, that of the intended EMA.

This technology relies on micro-perforated (5Opm-lOOpm diameter) films and is mainly employed in horizontal or vertical, form, fill and seal pouches, in which there is generally a large surface area to product mass ratio.

If the product is packed in a heat-sealed tray, only the lidding film is effectively available for gas transmission, providing a very poor surface area to product mass ratio. MAP, unsupported by an active pack inclusion, is unlikely to be able to achieve or maintain an EMA throughout an extended shelf life.

It is, however, possible to employ active packaging in the form of 02 generator/CO2 absorber, or generator, inclusions. These will be able to prevent anaerobiosis, but due to the gas permeability of the packaging, can not be guaranteed to precis&y maintain a target EMA.

Controlled Atmosphere Packaging (CAP) on the other hand, uses: -a hermetic closure, gas impermeable/barrier packaging materials, the complete replacement, at the time of packing, of the ambient atmosphere within the pack by a pack atmosphere of a predetermined gas composition, which is not intentionally allowed to be modified by the respiratory activity of the packed product, and the support of the pre-determined pack atmosphere by the employment of active packaging in the form of 02 generator/CO2 absorber, or generator inclusions.

GB 2 450 860 describes a system of this type. In the system, according to GB 2 450 860, a packaging inclusion is in the form of a sachet containing a formulation with the main active ingredient being sodium carbonate peroxyhydrate. This compound generates oxygen and absorbs carbon dioxide when activated by water vapour. A number of powder materials, including the sodium carbonate peroxyhydrate, sodium carbonate, anhydrous sodium chloride and zeolite or Bentonite clay are mixed and enclosed in a permeable envelope.

However, although the effective operating life of such a packaging inclusion is suitable for short periods, for example when used with highly perishable foodstuffs, such as soft fruit, it has not proved suitable for deployment over longer periods, particularly in combination with the requirement that the sachet is small and discreet. There remains a need for an improved device, which can operate for longer periods without being too large.

A further issue with the arrangement of GB 2 450 860 is that the sachet described in that document cannot be allowed to come into contact with water in liquid form. Water in liquid form can often be present in packaging, for example drip-loss' or severe condensation if the packaging is rapidly cooled.

Sum mary of the Invention According to the invention there is provided a packaging device, comprising: an envelope, impermeable to liquid water and permeable to water vapour and gases; a fill material contained in the envelope, which is activated by water vapour to generate oxygen and absorb carbon dioxide; and wherein the envelope is of a laminate material which comprises a permeable support layer and a control layer of polyamide or polyethylene having a thickness of 10pm to 2Opm.

The inventors have realised that the control layer should have sufficient gas permeability and allow water vapour to permeate without allowing liquid water to pass. By limiting the water vapour transmission rate and oxygen transmission rate, the operational life of the packaging device in use may be extended.

The control layer may have a water vapour transmission rate of lOg to 200g/m2 in 24 hours at I bar and 23 °C and 85% relative humidity and an oxygen transfer rate in the range 650cm3-20,000cm3/m2 in 24 hours at 1 bar at 23°C.

The water vapour transmission rate and oxygen transfer rate may be selected by choosing a suitable thickness of the control layer. Thicker layers of polyamide or polyethylene give reduced transfer rates.

Significant improvements in the operational life of the product may be achieved by introducing the control layer with controlled water vapour transmission rate and oxygen transfer rate. The inventor has, however, additionally discovered that further benefits may be obtained by selectively modifying the relative composition of the mixture of compounds comprising the fill material. The fill material may comprise an active ingredient that generates oxygen and absorbs carbon dioxide when activated by water vapour; and a water vapour control that absorbs water vapour in order to regulate the reaction of the active ingredient, wherein the active ingredient is present in an amount from 25% to 65%, and the water vapour control is present in an amount from 25% to 65%.

The introduction of the control layer, with the additional control over the water vapour transmission rates, effectively supplements the water vapour control function of the fill material formulation, thus allowing, in some applications, the percentage composition of those component compounds exercising this function to be reduced. The major consequence of this is the ability to reduce the size of the active pack inclusions.

In a preferred embodiment, the permeable support layer is a non-woven polyethylene fabric. The density may be 45 g/m2-55g1m2.

A polyurethane adhesive may be used to bond the layers of the laminate together.

In another aspect of the invention there is provided a packaging device, comprising: an envelope, impermeable to liquid water and permeable to gas; a fill material contained in the envelope, which is activated by water vapour to generate oxygen and absorb carbon dioxide; and wherein the envelope is of a laminate material comprising a permeable support layer and a control layer, the control layer having a water vapour transmission rate of lOg to gIm2 in 24 hours at 1 bar and 23 °C and 85% relative humidity and an oxygen transmission rate in the range 650cm3-20,000cm3/m2 in 24 hours at 1 bar at 23°C In a further aspect of the invention there is provided a packaging device, comprising: an envelope, impermeable to liquid water and permeable to gas; a fill material contained in the envelope, which is activated by water vapour to generate oxygen and absorb carbon dioxide; wherein the fill material comprises: an active ingredient that generates oxygen and absorb carbon dioxide when activated by water vapour; and a water vapour control that absorbs water vapour to regulate the reaction of the active ingredient, wherein the active ingredient is present in an amount from 25% to 65%, and the water vapour control is present in an amount from 25% to 65%.

Further aspects of the invention relate to packaging which contains the packaging device.

Detailed Description

An embodiment of the invention is a device having an envelope fabricated from a composite material, impermeable to liquid water, but permeable to water vapour and gases and containing a formulation, including sodium carbonate peroxyhydrate, which is capable, on hydration, of both generating oxygen and subsequently absorbing carbon dioxide, being designed to maintain a predetermined percentage composition of oxygen and carbon dioxide in both modified atmosphere (MA) and controlled atmosphere (CA) packed foods and related products, by actively compensating for changes within the pack atmosphere.

This device has been designed as an active inclusion, for use within both MA and CA retail packaging, in order to establish and maintain a stable, predetermined percentage composition of oxygen and carbon dioxide within a pack atmosphere, which will allow a quality maintained, extended shelf life of the packed product.

A further goal is to allow the device to operate within the presence of free aqueous liquids in the packaging, if present. Some foodstuffs and other materials can give rise to drip-loss' or condensation in the packaging.

The device envelope 10 of the embodiment contains a fill material 18 formulation of a mixture of four or five compounds. The formulation of the fill material of the device, in terms of the percentage composition of the constituent compounds, is designed to effect the pack atmosphere control required and is thus specific to the product packed and will therefore vary from product to product. Specific formulations are described below.

The mass of the fill material formulation of the device, is designed to effect the shelf life required and is thus specific to the product packed and will therefore vary from product to product.

In order to allow the fill material formulations to perform optimally, the envelope of the device is required to be impermeable to liquid water but to have both a suitable water vapour transmission rate (WVTR) and a high oxygen transmission rate (OTR).

To achieve this, the material, from which the envelope is fabricated, is a bi-laminate with an inner polymer film layer supported by an outer layer of a dense, non-woven polymer fabric.

In order to retain fully the fill material formulation selected, both dry and hydrated, when in contact with food and in the presence of free liquid water, the envelope 10 of the device is of a laminate material comprising a porous support layer 12 and a water impermeable layer 14, the water control layer having a water transfer rate of lOg to 200g/m2 in 24 hours at 23 °C and 85% relative humidity and an oxygen transfer rate in the range 650cm3-20,000cm3Im2 in 24 hours at 1 bar at 23°C.

The water vapour transmission rate may be measured by employing a commercially available water permeation analyser such as the MOCON PERMATRAN-W Model 3/33, which is designed to test this property of packaging films and has integral automatic relative humidity generation. The machine measures according to the ASTM standard F-1249.

The oxygen transmission rate may be measured by employing a commercially available oxygen transmission rate analyser, such as the M000N OX-TRAN Model 1/50, which is designed to test this property of packaging films. The machine measures according to the ASTM standard F-1927.

In a particular embodiment, the envelope is a bi-laminate material, consisting of an outer, permeable, printed, layer 12 of a non-woven, opaque 45 g/m2 -55g/m2 polyethylene fabric, bonded with a polyurethane adhesive to an inner, water impermeable layer 14 of either polyamide (PA) film, with a thickness of lOp -20p or polyethylene (PE) film, with a thickness of lop -2Op.

The polymer film layer, depending on the water vapour and gas transmission requirements demanded by the activity of the packed product, is either polyamide (PA), with a thickness of 10pm -2Opm or polyethylene (PE), with a thickness of 10pm -2Opm or polyethylene terephthalate (PET), also known as polyester, with a thickness of 10pm - 2Opm or polypropylene (PP) with a thickness of 10pm -2Opm. For many applications, PA is preferred.

The supporting layer is TYVEK; a permeable, non-woven polyethylene fabric, which in this case will have a density of 45g/sm -55g/sm. This material is not an effective barrier to water vapour, oxygen or carbon dioxide.

The inner and outer layers are bonded together with a polyurethane adhesive, or a material of equivalent properties and performance, the composition and thickness of which will have a negligible effect on either the WVTR or OTR of the inner layer or the laminate in general.

In the simplest construction of the device, the envelope material is fabricated into a sachet 20, which allows the inward passage of water vapour, the outward passage of oxygen and the inward or outward passage of carbon dioxide; the latter two gases at both a relatively high rate and high pressure.

In this format, the device can be manufactured using existing vertical, or horizontal, form, fill and seal technology, where the seals themselves can be heat bonded or dielectrically or ultrasonically welded.

In this format, the device is intended to be placed, generally unsecured, within the primary packaging of the packed product.

In an alternative construction of the device, the envelope material is thermoformed in a shallow concave, rectangular, or discoid chamber, into which the fill material is deposited. It is then lidded with a gas impermeable membrane of APET, or a material of equivalent properties and performance, and sealed by heat bonding or dielectric, or ultrasonic welded.

In this format, the device can be manufactured using modified, horizontal tray forming and lidding technology.

In this format, the device is intended to be placed and secured, in a pre-determined position, on the inner surface of the primary packaging of the packed product.

The size and thus the exposed surface area of either of the formats of the device is designed to effect the pack atmosphere control required and is thus specific to the product packed and will therefore vary from product to product.

In either of the above formats, the device can be readily manufactured in a range of sizes The size and thus the exposed surface area of either of the formats of the device is designed to effect the shelf life required and is thus specific to the product packed and will therefore vary from product to product.

The device is designed for deployment within the packaging of product, such as a food product or a related product, in which there is free water present and where the oxygen and carbon dioxide composition of the pack atmosphere is required to be maintained at predetermined levels.

The device is designed to perform effectively when subject to intermittent contact with or occasional immersion by free water.

The criteria, which this device aims at are:-to be discrete and unobtrusive within the retail pack, to fully retain the fill material and any reaction products, to allow high levels of gas transmission, to allow high levels of water vapour transmission, to be impervious to water in its liquid form, to provide an opaque outer surface which will allow print of high definition, to meet all current materials in contact with food' regulations.

The inventor has now realised that the composition of the atmosphere that works most effectively depend on the pack contents. Some products, for example, have longer shelf lives in the presence of controlled amounts of carbon dioxide and some have longer shelf lives when the presence of carbon dioxide is minimised.

To address these needs, alternative formulations of fill material may be used.

In the device, where a level of carbon dioxide absorption is required, the fill material is a mixture composed of the following: -sodium carbonate peroxyhydrate, in the form of medium fine granules calcium Bentonite clay, or alternatively a zeolite, in the form of a fine powder.

sodium carbonate in the form of medium fine granules sodium chloride, as a fine crystalline powder In the device, where a level of carbon dioxide generation is required, the fill material is a mixture composed of the following: -sodium carbonate peroxyhydrate, in the form of medium fine granules, calcium Bentonite clay, or alternatively a zeolite, in the form of a fine powder.

sodium chloride, in the form of a fine, crystalline powder sodium hydrogen carbonate, in the form of a fine powder citric acid, in the form of a fine powder (or another, relatively low molecular weight organic food acid with equivalent properties and performance) The formulation of the fill material, in terms of the percentage composition of the constituent compounds, is designed to effect the pack atmosphere control desired and is thus specific to the product packed and will vary from product to product.

In deployment, the following compounds, where included in the formulation, are activated by contact with water, in the form of water vapour, which is present in the pack atmosphere, namely: sodium carbonate peroxyhydrate, sodium carbonate, sodium hydrogen carbonate with citric acid.

The oxygen generating reaction formulae are as follows: -H20 Na2CO3.3/2H20 -* Na2CO3 + 3/2H202 -) Na2CO3 + 3/2H20 + 3/402 sodium carbonate peroxyhydrate Thus, sodium carbonate peroxyhydrate constitutes an oxygen generating formulation.

The carbon dioxide absorbing reaction is as follows: -Na2003 + 002 + H20 -* 2NaHCO3 sodium carbonate Thus, sodium carbonate constitutes a carbon dioxide absorbing formulation since it absorbs carbon dioxide on activation by water.

The carbon dioxide generating reaction is as follows: - 3NaHCO3 + C6H307 4 C6H507Na3 + 3H20 + 3C02 sodium hydrogen citric carbonate acid Thus, a combination of sodium hydrogen carbonate and citric acid constitutes a carbon dioxide generating formulation.

Compared with the formulations proposed in GB 2 450 860 the fill material proposed in the present invention includes a relatively smaller amount of Bentonite clay (or zeolite) and sodium chloride to restrict the availability of water vapour to active components, reduce the rate of reaction and hence extend the lifetime.

In order to control the rates of reactions and allow them to continue over a pre-determined, extended period, the availability of water is regulated by both the selection of the gauge and material of the polymer control layer of the sachet and the predetermined percentage composition of both the sodium chloride component and the calcium Bentonite clay component (or alternatively a zeolite), which are strongly hydroscopic and absorb water vapour from the pack atmosphere much more readily than does either the sodium carbonate peroxyhydrate, sodium carbonate or sodium hydrogen carbonate and citric acid, effectively restricting the amount of water, in the form water vapour, available to the latter compounds.

Thus, the combination of Bentonite clay, zeolite and/or sodium chloride constitutes a control formulation.

The calcium Bentonite clay component (or alternatively a zeolite), as a finely particulate material, has a very large capacity to absorb water, as water vapour, from the atmosphere.

Bentonite clays and zeolites are aluminosilicates of alkali metals. They have three dimensional crystalline frameworks of tetrahedral silica or alumina anions strongly bonded at all corners. These structures contain -Si-O-Al-linkages that form surface pores of uniform diameter and enclose regular internal cavities and channels of discrete sizes and shapes, depending on the chemical composition and crystal structure structures of the specific zeolite involved. The pore sizes range from 2.0 to 4.3 Angstroms and the enclosed cavities both the mineral cations and water molecules, the latter being capable of desorption as well as adsorption.

A particular set of percentages of the fill composition, where significant levels of carbon dioxide in the pack atmosphere are not required, for extended life are: -sodium carbonate peroxyhydrate 30% to 50%, preferably 35% to 45% calcium Bentonite clay, or alternatively a zeolite, 20% to 50 %, preferably 30% to 45% sodium chloride, 5% to 25%, preferably 10% to 20% sodium carbonate 2% to 10%, preferably 3% to 8% In a particular embodiment, the following percentages may be used: sodium carbonate peroxyhydrate 40.0% calcium Bentonite clay, or alternatively a zeolite, 40.0% sodium chloride, 15.0% sodium carbonate 5.0% Suitable percentages of the fill composition where significant levels of carbon dioxide in the pack atmosphere are not required, for extended life are: -sodium carbonate peroxyhydrate 25% to 50%, preferably 30% to 40% calcium Bentonite clay, or alternatively a zeolite 20% to 50 %, preferably 30% to 45% sodium chloride 5% to 25%, preferably 10% to 20% sodium hydrogen carbonate 2% to 10%, preferably 3% to 8% citric acid 1 % to 6%, preferably 2% to 5%.

In a particular embodiment, the following percentages may be used: sodium carbonate peroxyhydrate 36.0% calcium Bentonite clay, or alternatively a zeolite 39.0% sodium chloride 15.0% sodium hydrogen carbonate 6.5% citric acid 3.5%.

Note in particular that GB 2 450 860 proposed up to 16% Bentonite clay, for example.

The amount of Bentonite clay in these formulations for long lifetime is greater.

Apart from the composition, the mass of a fill material formulation is also determined by the particular demands placed on the pack atmosphere by the packed product concerned and the requirements it imposes on the former in order to maintain the predetermined, optimum gas composition for the shelf life desired.

The dimensions of a sachet and thus surface area will reflect both the mass and formulation of the fill material required to effect the pack atmosphere control desired but, even when hydrated, it is anticipated that it will form a relatively discrete an unobtrusive packaging inclusion.

Embodiments of the invention incorporate the device into packaging containing product.

The packaging may be used to contain various perishable products, such as fresh fruit and vegetables. The retail life of longer lasting plant and animal based products and derived products of similar nature may also be extended to, for example, ready to eat' and ready to cook' recipe dishes, smoked or smokeless tobacco products, pharmaceutical products, specialised chemical products, natural remedies and the like.

Experiments have shown that packages containing active packaging inclusions as described can both maintain elevated levels of oxygen and control carbon dioxide levels in the pack atmosphere for as much as twenty five weeks. In particular, the use of a water vapour transmission control layer of polyamide greatly extends the retail life when compared with packages containing active packaging inclusions where such a polymer is not present.

Claims

CLAIMS1. An active packaging inclusion, comprising an envelope, a fill material contained in the envelope, which is activated by water vapour to generate oxygen and absorb or generate carbon dioxide; and wherein the envelope is impermeable to liquid water and permeable to water vapour and gases, and comprises a laminate material comprising a permeable support layer and a water vapour control layer, wherein the water vapour control layer is a polyamide or polyethylene film having a thickness of 10pm to 2Opm.
2. An active packaging inclusion according to claim 1, the water vapour control layer having a water vapour transmission rate of lOg to 200g/m2 in 24 hours at 23 00 and 85% relative humidity and an oxygen transmission rate in the range 650cm3- 20,000cm3/m2 in 24 hours at I bar at 23°C.
3. An active packaging inclusion according to claim I or 2 wherein the permeable support layer is an outer layer of non-woven, polyethylene fabric.
4. An active packaging inclusion according to claim I or 2 wherein the permeable support layer is an inner layer of non-woven, polyethylene fabric.
5. An active packaging inclusion according to claim 3 wherein the density of the non-woven, polyethylene fabric is 35 gIm2-65g1m2.
6. An active packaging inclusion according to any preceding claim wherein a polyurethane adhesive bonds the layers of the laminate material together.
7. An active packaging inclusion according to any preceding claim, wherein the fill material comprises: an active ingredient, sodium carbonate peroxyhydrate, that generates oxygen and absorbs carbon dioxide when activated by water vapour; and water vapour control ingredients, calcium Bentonite clay (or zeolite) and sodium chloride, that absorb water vapour to regulate the reaction of the active ingredient, wherein the active ingredient is present in an amount from 25% to 65%, and the water vapour control ingredients are present in an amount from 25% to 65%.
8 An active packaging inclusion according to claim 6, further comprising a carbon dioxide absorbing ingredient from 2% to 10%.
9. An active packaging inclusion according to any preceding claim wherein the fill material comprises: 30% to 60% by weight sodium carbonate peroxyhydrate; 20% to 50 % by weight calcium Bentonite clay or zeolite; 5% to 25% by weight sodium chloride, and 2% to 10% by weight sodium carbonate.
An active packaging inclusion according to claim 8 wherein the fill material comprises: 35% to 45% by weight sodium carbonate peroxyhydrate, 30% to 45% by weight calcium Bentonite clay or a zeolite, 10% to 20% by weight sodium chloride, 3% to 8% by weight sodium carbonate.
11. An active packaging fill material formulation according to claim 6, further comprising a carbon dioxide generating ingredient from 4% to 15% by weight.
12. An active packaging inclusion according to any of claims I to 6 or 10 wherein the fill material formulation comprises: 25% to 50% by weight sodium carbonate peroxyhydrate; to 50 % by weight calcium Bentonite clay or zeolite; 5% to 25% by weight sodium chloride, and 2% to 10% by weight sodium hydrogen carbonate, and 1 % to 6% by weight citric acid.
13. An active packaging inclusion according claim 11 wherein the fill material formulation comprises: 30% to 40% by weight sodium carbonate peroxyhydrate; 30% to 45% by weight calcium Bentonite clay or zeolite; 10% to 20% by weight sodium chloride, and 3% to 8% by weight sodium hydrogen carbonate, and 2% to 5% by weight citric acid.
14. A package for perishable products requiring a predetermined pack atmosphere composition in relation to oxygen and carbon dioxide, comprising a gas and water vapour impermeable outer housing, and an active packaging inclusion according to any preceding claim.
15. A package for perishable products requiring a predetermined pack atmosphere composition in relation to oxygen and carbon dioxide, comprising a gas permeable outer housing, and an active packaging inclusion according to any of claims I to 12.