FOOD GRADE QUALITY OF PLASTICS AND …

1 47 PLASTICS IN food PACKAGINGFOOD GRADE QUALITY OF PLASTICS AND REGULATIONSC hapter3 food GRADE QUALITYOF PLASTICS ANDREGULATIONSB aldev RajFood Packaging Technology DepartmentCentral food Technological Research InstituteMysore 570 020 (INDIA)48 PLASTICS IN food PACKAGINGC hapter 349 PLASTICS IN food PACKAGINGFOOD GRADE QUALITY OF PLASTICS AND REGULATIONSC hapter 3 food GRADE QUALITY OFPLASTICS AND REGULATIONSROLE OF additives INPLASTICSIn addition to the basic polymers, plasticsalso contain additional chemical compo-nents called additives , which are added insmall amounts to alter the properties of thepolymers in the desired way and/or simplifytheir processing. Only fillers and softeners(plasticizers) are used at high concentrationto increase volume and/or weight to improvesoftening, flexibility, elasticity, malleabilityand processability. Other additives aremostly low molecular weight componentslike stabilizers, anti-oxidants, antistaticagents, light stabilizers (UV absorbers),lubricants (slip agents), optical brighteners,etc.

2 Polymer packaging materials may alsocontain small quantities of monomers,oligomers as well as polymerization catalystsand regulators, cross-linking agents,emulsifer agents, etc. These additives alongwith low molecular weight non-polymericcomponents, which occur from plasticpackaging materials, possess high is likely that some transfer of low-molecularweight non-polymeric components willoccur from the plastic packaging materialinto the packaged content, therebycontaminating the product with the risk oftoxic hazard to the consumer. However, it isto be remembered that useful properties ofthe PLASTICS are not manifested without theaddition of these additives . Therefore,guidelines for proper use of PLASTICS for foodpackaging applications have beenformulated all over the world, which arenecessary to safeguard health of over the safety-in-use of plasticsas food packaging materials arisesprincipally from the possible toxicity of otherlow molecular weight constituents that maybe present in the package and hence, getleached into the foodstuff during storage.

3 Asstated above, such constituents arise fromtwo sources:Polymerisation residues includingmonomers, oligomers (with a molecularweight up to about 200), catalysts (mainlymetallic salts and organic peroxides),solvents, emulsifiers and wetting agents, rawmaterial impurities, plant contaminants,inhibitors, decomposition and side more volatile gaseous monomers,such as ethylene, propylene and vinylchloride, usually fall in concentration with50 PLASTICS IN food PACKAGINGC hapter 3time, but very low levels may persist in thefinished product almost indefinitely. Styreneand acrylonitrile residues are more difficultto aids such as antioxidants,antiblock agents, antistatic agents, heat andlight stabilizers, plasticisers, lubricants andslip agents, pigments, fillers, mould releaseagents and fungicides are added to assistproduction processes or to enhance theproperties and stability of the final may be present in amounts varyingfrom only a few parts per million up toseveral parts per compounds of the first group arepresent inadvertently, there is not much thatcan be done to remove them.

4 However, theefforts made by the industry to reduce vinylchloride monomer levels in particular,illustrates the advantages of optimummanufacturing processes on the purity ofthe final product. Chemicals added delibe-rately during formulation to alter theprocessing, mechanical or other propertiesof the polymer are likely to be present ingreater amounts than polymerizationresidues and should be subjected to strictquality control. They are normally restrictedto compounds appearing on an approvedlist for food contact use. A brief account ofthe functions of some major additives ispresented below:Antiblock AgentsThese are added to roughen the surfaceof thin films and, hence, prevent themsticking together during machine is most commonly used because itspoor solubility in most polymers helps toincrease the surface concentration and sointroduces irregularity. Similarly, slipadditives such as fatty acids and amides areused to reduce prevent degradation of the polymerby reacting with atmospheric oxygen duringmoulding operations at high temperaturesor when used in contact with hot foods andto prevent deterioration during storage.

5 Deri-vatives of phenols and organic sulphidesare the most frequently used of these compounds are classified asheat AgentsSince all PLASTICS are good electricalinsulators (and are in fact used on a largescale for this purpose) they will retainelectrostatic charges produced by frictionfrom contact with processing of static electricity can causeproblems through the pick-up of dust,adhesion between layers or particles ofplastics, sparking, electrical shock andpossibly fire hazards. Most antistatic agentsare glycol derivatives or quaternary ammo-nium compounds; both increase the electricalconductivity and plate-out onto the surfaceof are added to reduce frictionalforces and are usually low to mediummolecular weight hydrocarbons. Theyshould possess good solubility with theplastic, low volatility and be relatively are added to make the productmore flexible and less brittle.

6 They are usuallyhigh molecular weight esters. The plasticizeralso gives the material the limp and tackyqualities found in cling films. About 80%of all plasticizers are used in PVC. Typically51 PLASTICS IN food PACKAGINGFOOD GRADE QUALITY OF PLASTICS AND regulations phthalic esters such as dioctyl phthalate(DOP), also known as di-2-ethylhexyladipate(DEHA) are used as StabilizersThese are needed to protect the productfrom deterioration by sunlight or evensupermarket lighting. Products containingvitamin C are particularly susceptible to thisform of Property ModifiersThe optical properties of a material froma technological aspect are normally describedin terms of their ability to transmit light, toexhibit colour and reflect light from thesurface ( , gloss). The majority of foodpackaging films are unpigmented, but someare coloured by the addition of principal pigments used as colourantsin packaging are carbon black, whitetitanium dioxide, red iron oxide, yellowcadmium sulfide, molybdate orange,ultramarine blue, blue ferric ammonium ferricammonium, ferrocyanide, chrome green, andblue and green copper RetardantsAlthough most packaging materials arecombustible, their lack of flame resistance isdisregarded in most food packagingapplications.

7 For example, thermoformedpolystyrene cups and plates are combus-tible; the risk of fire must be balanced againstthe possible toxicity of flame AgentsFoaming or blowing agents are used forthe production of cellular products and arenormally classified into physical andchemical types, according to whether thegeneration of gases to produce the cells takesplace through a physical transition or sublimation or by a chemicalprocess decomposition reactions whichresult in evolution of gases. In food packagingapplications, physical blowing agents arenormally used. For example, expanded andextruded polystyrene foams use a fluoro-carbon or light aliphatic hydrocarbon suchas pentane as the blowing AgentsAntimicrobials such as algicides,bactericides and fungicides can be added topolymers to prevent the growth of micro-organisms. However, their use in foodpackaging is rare because of the possibilityof migration into the food OF ADDITIVESThe ingredients in the PLASTICS packagingmaterials may cause toxicity as a result oftheir migration to the foodstuffs in which thelatter are packed.

8 Therefore, positive lists ofconstituents ( additives ) to be used inrespective PLASTICS in contact with foodstuffs,pharmaceuticals and drinking water havebeen specified. The manufacturer has tofollow a Good Manufacturing Practice(GMP) using only those additives listed inthe positive list. Prior to categorizing anyplastics as toxic, evidence regarding degreeof migration of their constituents has to beascertained. In general, migration andextraction studies need to be simultaneouslyconducted on actual foodstuffs underconditions, which are slightly more stringentthan those encountered in normal usage. Itis, however, not always possible to analyseactual foodstuffs for the nature and quantityof migrants from the PLASTICS . In order tosimplify such assessment, food simulants/extractants have to be substituted for theactual foodstuffs. Further, it is also very52 PLASTICS IN food PACKAGINGC hapter 3difficult to estimate all the migrantsindividually.

9 Hence, as a good measure, theoverall migration of all the migrants puttogether is considered for safe use, unlessthey are especially toxic and their limits ModelThe extent of migration of a substancedepends on its concentration in the material,the extent to which it is bound or mobilewithin the matrix of the material, the thicknessof the packaging material, the nature of thefood with which the material is in contact(dry, aqueous, fatty, acidic, alcoholic), thesolubility of the substance in the food , theduration of contact and a system of polymer/ food as presentedin the figure below, we have the food on theleft which can migrate into the polymer layerson the right side, along with an intermediatelayer of swollen polymer with a profile of themigrating food component. On the otherhand, we have a concentration gradient ofthe considered additives , where we assumethat we have a certain diffusion in theundisturbed polymer layer and a muchimproved mobility of the additive in theswollen layer and concentration jump at particularly considered theconsequence of the model.

10 The followinggeneral formula relates the migration of anadditive. In a system where a cut of theplastic P into a food F at a certain time t, iskept at constant temperature, the modelpredicts direct proportionality of migrationof the concentration CPA of the consideredadditive in the polymer and to the squareroot of time (t).MFA (T) = CPA tMFA (T) is concentration of migratingadditive A into test food F, at a temperatureT and is is a proportionality ,CAFis concentration of additivesin food CFPis concentration of food inpolymerCAP+Fis concentration of additive inpolymer and food , which haspenetrated into concentration of additive inpolymerINDIAN STANDARDS FOROVERALL MIGRATION(IS: 9845-1998)CFTRI drafted IS:9845-1998 for Determi-nation of overall migration of constituents ofplastics materials and articles intended tocome in contact with foodstuffs - method ofanalysis (second-revision) which is nowimplemented to be followed for overallmigration of PLASTICS constituents for theirfood GRADE QUALITY in the country.