multilayer films a solution for demanding food packaging applications english

8/10/2019 Multilayer Films a Solution for Demanding Food Packaging Applications English

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Thin walledcontainers the packaging ofchoice

ISO 22000 a newglobal standard for

food safetyDietary fibre thehealthy approach

Revolutionising theMultigrain Process

Biodegradableplastics for the foodindustry

Thin walledcontainers the packaging ofchoice

ISO 22000 a newglobal standard for

food safetyDietary fibre thehealthy approach

Revolutionising theMultigrain Process

Biodegradableplastics for the foodindustry

food Issue 3 Spring 2006T H E Q U A RT E R LY M A G A Z I N E F O R T H E F O O D A N D B E V E R A G E I N D U S T R I E S I N E U R O P E

ANALYSIS

PACKAGING

INGREDIENTS

PROCESSING


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packaging

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any kind of impact, to ensure highproduction efficiency, to supportenvironmental sustainability and toprovide maximum shelf appeal.

In terms of protection, the

packaged food must be protectedagainst aromas and odours, gases(e.g. oxygen, nitrogen and carbondioxide), water vapour, light, fat,temperature, chemical andmechanical impacts. Thepackaging must ensure that theinteraction between theenvironment and the packagedfood is minimal.

Multilayer filmsSuch a multitude of requirements

cant be fulfilled with packagingfilms based on a single polymer.While such a polymer might beappropriate in terms of fulfillingone specific requirement it maywell possess other propertieswhich are disadvantageous andunsuitable for the production offood packaging. Therefore, thefood packaging industry requiresmultilayer films to combine theadvantages of each single polymerinto one film and thus balance andcompensate for their individualdisadvantages.

Multilayer films can be producedeither by lamination or by co-extrusion. In the laminationprocess, two or more films arebonded together using adhesivesto produce a composite filmstructure. The co-extrusionprocess combines several layersof individual polymers into one filmso that they benefit from theirdifferent chemical and mechanicalstrengths. The combination of thedifferent polymer layers is variableand will be done according to the

The time people spend cooking isdecreasing, which in turnincreases demand for preparedfood with minimum cooking times.And there is simultaneously agrowing demand for products withlonger shelf life but the samenutritional value and aromaticproperties; and an increasingfocus on a healthy lifestyle, sothat the demand for bio-food issteadily rising.

The requirements forpackagingIn addition, the growing number ofsingle households and householdswith elderly people living alonecauses an increasing demand forsingle packs with a high level ofconvenience and features such aslightweight packaging, and easy-to-open, re-closable containers.

Production security andtraceability of the productionprocess is a prerequisite,including, for example, theimplementation of certain qualityand hygiene standards toguarantee food safety andconsumer security. A goodexample is the hygienerequirements applicable to theproduction of ready meals, whichare designed to be heated andconsumed by the final customerwithout undergoing aseptictreatment such as boiling orgrilling. The issues of tamperevidence and intelligent packagingsystems are therefore becomingmore and more significant.

The requirements a food packagehas to fulfil are thus becomingmore and more demanding, andinclude, among others, the need toprotect the packed food against

Multilayer films: a solution fordemanding food packaging applicationsNowadays we are witnessing a significant change in food consumption habits. Sales of fresh foodover the counter are decreasing as more and more consumers prefer to use cold shelves wherethey can find the product prepared and packaged without having to wait. More than two thirds ofpurchase decisions are made on impulse at the shelf. We also observe a snack and ready to eatphenomenon going on in Europe.

requirements of the package.

An example of an application formultilayer films is the foodpackaging industrys demand forbarrier packaging films. Within the

food packaging industry, two mainpackaging techniques are appliedin order to increase the shelf lifeof the packaged food: modifiedatmosphere packaging (MAP) andvacuum packaging.

Vacuum packagingIn vacuum packaging all theatmosphere inside the package isevacuated in order to create avacuum. Vacuum packagingimproves the freshness of thepacked goods and increases theirshelf life by preventingmicrobiological deterioration. Italso prevents the product fromshrinking or drying. Vacuumpackaged products maintain theirhumidity, outward appearance andaromas, and are not exposed tooxygen.

Graph 1 shows the interaction avacuum packaged food productwill have with its environment andwhich barrier properties thepackaging material has topossess.

Graph 1


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Modified atmospherepackaging

Modified atmosphere packagingimproves the preservation of thepacked goods by replacing theatmosphere that surrounds theproduct in the package with amodified atmosphere (a mixture ofinert gases). Within the package,the modified atmosphere controlsthe chemical, enzymatic andmicrobiological reactions of theproduct without significantlychanging its chemical structure.Modified atmosphere packaging isused for a wide range of productssuch as meat, pasta and sometypes of cheeses.

The modified atmosphere used forfood packaging is a combinationof three gases: oxygen (O 2),carbon dioxide (CO 2) and nitrogen(N 2). The combination of thesethree depends on the goods to bepacked.

Nitrogen is an inert gas that is

soluble in water or other gases. Itsubstitutes the oxygen inside the

package and stabilises it. It alsomakes the atmosphere moveinside the package, preventing theproduct from sticking. This isespecially important for packingsliced products. Carbon dioxide issoluble in water and fats and in aminimum concentration of 20%prevents fungal and bacterialgrowth. Oxygen is used in

packaging for fresh meat, often incombination with carbon dioxideand/or nitrogen. The combinationof all three helps to preserve the

red colour of meat throughout itsshelf life.

Graph 2 shows the interaction aMAP packaged food product willhave with its environment andwhich barrier properties thepackaging material has topossess.

Selecting the polymersThe polymers which have to becombined into a multilayer barrierfilm are selected once the specific

requirements of the food productto be packed have been defined,and the expected shelf life of thepackage, aspects of environmental

sustainability, shelf appeal at thepoint of sale and productionefficiency etc have been specified.

The main property of the polymerto be taken into consideration forthe production of barrier films isits rate of permeability to gasesand water vapour (see Graph 3).

PVC, PET, Nylon, PVdC andEVOH, for example, offer a goodbarrier to gas transmission.However, their effectiveness as abarrier to water vapour is oftennot high enough for many foodpackaging applications.

PE, PP and EVA offer a highbarrier to water vapour, whichhelps to prevent a moist productlosing humidity and becoming dryand conversely a dry productattracting humidity and becomingmoist. On the other hand, theirbarrier to gases is not highenough: they cannot keep themodified atmosphere inside thepackage.

The barrier property of amultilayer film will always beinfluenced by the thickness of thepolymer layers.

Film productiontechnologyThe permeability rates of watervapour and oxygen are alsoinfluenced by the film productiontechnology applied. Technologiessuch as blending co-polymers,changing the specific polymerweight with additives, creatingcrystalline structures andorientating the film also have animpact on the barrier properties ofthe film. For example, the barrierproperty of a bi-oriented PP filmagainst water vapour, oxygen andnitrogen is twice as high as thebarrier property of an un-orientedPP-film.

Other factors that must be takeninto consideration are that thebarrier properties of the packagingmaterial may change due tothermal impacts during thepackaging process (e.g.pasteurisation and sterilisation) orbe affected by otherenvironmental influences. For

The barrier property of a

multilayer film willalways beinfluenced by thethickness of thepolymer layers

Graph 2

Graph 3


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such as LDPE, mPE, Surlyn andEVA are typical sealing layers.

Peelability: To make the openingof the sealed package easier.

Transparency: The transparencyof the package is important forthe visibility of the product. An

anti-fog treatment can be appliedto the base and top films toprevent water droplets forming onthe surface of the package.

Thermoformability: The wallsof the thermoformed tray musthave a minimum thickness toensure that the barrier propertiesof the film are maintained.

Temperature resistance:Prepared food is often designed tobe heated in the oven ormicrowave without removing thepackage. In this case, the packagemust be able to resist heat for acertain period of time. As

example, polymers which contain-OH-groups (e.g. EVOH) becomesofter when they absorb humidity.Their diffusion and permeabilityincreases and the barrier propertyof the film is thus reduced. Withinthe broad range of barrierpolymers applied in the food

packaging industry only thepolymer PVdC shows barrierproperties that are not influencedby humidity.

TemperatureThe temperature of the packedgoods is also essential for bothgood functioning of the packagingas well as its barrier properties,because the diffusion of oxygenincreases the higher thetemperature is. Therefore thepackaged food should beuninterruptedly maintained at alow temperature throughout thechain.

Besides providing a barrier tooxygen and water vapour, barrierfilms applied for the production ofMAP packages must also fulfilother requirements, such as, forexample:

Sealability: By sealing the trayand top film hermetically we canprevent any opening of thepackage and preserve theatmosphere within it throughoutthe products shelf life. Polymers

temperature-resistant-polymersoften lack additional, requiredproperties, they have to becombined with other polymers tomake them suitable for such food

packaging. PP, for example, has ahigh level of heat resistance but alow barrier property againstoxygen. The combination of PPwith an EVOH layer(PP/EVOH/PP) can solve thisproblem. In addition, manyproducts undergo pasteurisationor sterilisation treatment duringthe packaging process. Thepackaging film must resist thehigh temperatures it will have to

bear during this sequence.

About KlcknerPentaplast

Klckner Pentaplast is a worldleading producer of films forpharmaceutical, food and technicalapplications. With 24 productionsites in 13 countries andapproximately 3,900 employees,kp generates revenues of morethan h 1.1billion. Its foodpackaging films are marketedunder the master brand name:Pentafood . The product rangeincludes a full spectrum of rigidand flexible films and poucheswhich are based on the polymersPA, PE, PET, PVC, PP and PSamongst others. For theproduction of films, blow and cast-extrusion, calandering andlamination processes are applied.In Europe, Pentafood films are

produced at ten differentproduction sites each of which isfully dedicated to therequirements of the foodpackaging industry and furnishedwith the latest, state-of-the-artproduction technology.

Valeska HauxStrategic Marketing & CommunicationsKlckner Pentaplast GmbH & Co AGwww.kpfilms.com

Note: The content of this article isconsistent with our knowledge at the timeof printing. We do not take anyresponsibility for the said content.

With 24 productionsites in 13 countriesand approximately3,900 employees, kpgenerates revenues of more than h 1.1billion

The following graph shows the different areas of application ofKlckner Pentaplasts rigid mono- and multilayer films depending ontheir barrier properties and their level of temperature resistance.

P L A

P P

P S / P E T G

P P / P E

P C / A P E T / P C

P E T B l e n

d / P E

P S / P E

C - P

E T

P V C

P E T

A P E T / P E T B / A P E T

P E T / P E E P E T B l e n

d / P E

P P / E V O H / P E

E P P / E V O H / P E

P P / P A / P E

P S / E V O H / P E

P S / E V O H / P E

P V C / E V O H / P E

P P / P A / P P

P P / E V O H / P P

P E T / E V O H / P E

E P E T B l e n

d / E V O H / P E

E P S / E V O H / P E

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multilayer films a solution for demanding food packaging applications english

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