Trends in Food Science & Technology 32 (2013) 128e141

Review

* Corresponding author.

0924-2244/$ - see front matter � 2013 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.tifs.2013.06.003

Application of

bioplastics for food

packaging

Nanou Peelmana,b,

Peter Ragaerta,b,*,

Bruno De Meulenaerb,Dimitri Adonsc, Roos Peetersc,

Ludwig Cardond,e,Filip Van Impef andFrank Devliegherea

aLaboratory of Food Microbiology and Food

Preservation, Department of Food Safety and Food

Quality (Partners in Food2Know), Ghent University,Coupure Links 653, 9000 Ghent, Belgium

bResearch Group Food Chemistry and Human

Nutrition, Department of Food Safety and Food

Quality (Partners in Food2Know), Ghent University,

Coupure Links 653, 9000 Ghent, Belgium (Ghent

University, Faculty of Bioscience Engineering,

Department of Food Safety and Food Quality, Coupure

Links 653, 9000Ghent, Belgium. Tel.:D32 9 264 99 30;

fax: D32 9 225 55 10; e-mail: peter.ragaert@ugent.be)cXIOS Hogeschool Limburg, Department of Applied

Engineering Sciences, Research Group Packaging

Technology e VerpakkingsCentrum, Universitaire

Campus, Agoralaan, Gebouw H, 3590

Diepenbeek, BelgiumdCentre for Polymer and Material Technologies CPMT,

Associated Faculty of Applied Engineering Sciences,

University College Ghent, Voskenslaan 362, 9000

Ghent, BelgiumeDepartment of Materials Science & Engineering,

Ghent University, Technologiepark 903, 9052Ghent, Belgium

fBelgian Packaging Institute (IBE-BVI), Z.1 e

Researchpark 280, 1731 Zellik, Belgium

This review provides state of the art information on the perfor-

mance of bioplastics materials, focusing on food packaging. It

gives an overview of the main materials used for producing

biobased films, their limitations, solutions thereof, possible ap-

plications and a state of the art on bioplastics already used as a

food packaging material.

Furthermore an inventory on bioplastics was made in the

context of a research project. Important characteristics

regarding packaging material are summarized in an extended

table, which shows a big variety (e.g. permeability, tensile

properties), suggesting a wide range of food products can be

packed in biobased polymer films.

IntroductionFood packaging is becoming increasingly important in thefood industry, where advances in functionality such as con-venience and portioning are gaining more attention.Furthermore, there is also an increased awareness on sus-tainability, which can in general be achieved on differentlevels. On the level of raw materials, use of recycled mate-rials or use of renewable resources are two strategies toreduce CO2 emissions and the dependency on fossil re-sources. The production process is another level where ad-justments, e.g. toward a more energy-efficient process, canbe made. A final level where efforts can be done to increasesustainability is waste management. Next to reuse and recy-cling of used materials, production of packaging which isbiodegradable and/or compostable contributes to reducingthe municipal solid waste problem. Biodegradable poly-mers are polymers that are capable of undergoing decom-position into CO2, CH4, H2O, inorganic compounds orbiomass through predominantly the enzymatic action of mi-croorganisms. Some of these polymers can also be com-postable, which means decomposition takes place in acompost site at a rate consistent with known compostablematerials (Siracusa, Rocculi, Romani, & Dalla Rosa,2008; Song, Murphy, Narayan, & Davies, 2009).

In the last decade, there has been an increased interest fromthe food, packaging and distribution industry toward the devel-opment and application of bioplastics for food packaging.

According to the European Bioplastics organization,bioplastics can be defined as plastics based on renewableresources (biobased) or as plastics which are biodegradableand/or compostable. Recently the attention in the pack-aging industry regarding the use of bioplastics has been

Nomenclature

AA ascorbic acidCA cellulose acetateCMC carboxymethyl celluloseDCL double-coated laminatesHDPE high-density polyethyleneHP high pressureHPMC hydroxypropyl methyl celluloseLBG locust bean gumLDPE low-density polyethyleneMAP modified atmosphere packagingMFC microfibrillar celluloseMMT montmorilloniteMWNT multi-walled nanotubesOMMT organically modified montmorilloniteOPLA oriented PLAOTR oxygen transmission ratePCL polycaprolactonePE polyethylenePEF polyethylene furanoatePEO polyethylene oxidePET polyethyleneterephthalatePHA polyhydroxyalkanoatePHB polyhydroxybutyratePHBV poly(3-hydroxybutyrate-hydroxyvalerate)PHV polyhydroxyvaleratePIP poly-cis-1,4-isoprenePLA polylactidePP polypropylenePS polystyrenePVA polyvinylacetatePVC polyvinylchloridePVdC polyvinylidene chlorideRH relative humiditySCL single-coated laminatesSPI soy protein isolateSWNT single-wall nanotubesTPS thermoplastic starchTPZ thermoplastic zeinWPI whey protein isolateWVP water vapor permeabilityWVTR water vapor transmission rate

129N. Peelman et al. / Trends in Food Science & Technology 32 (2013) 128e141

shifting from compostable/biodegradable materials towardbiobased materials (Molenveld, 2010).

This article gives an overview of the main bioplastics, themost common limitations and possible solutions thereof andthe current or possible use in food packaging. Furthermore,several characteristics of different biobased films were inves-tigated with respect to their application in the food pack-aging area. Regarding the type of bioplastics described inthis review, partly conventional materials such as polyeth-ylene (PE) and polyethyleneterephthalate (PET) made from

renewable resources are not discussed, as their propertiesdo not differ from the crude oil based PE and PET.

MaterialsPLA

PLA (polylactide) is a family of biodegradable thermo-plastic polyester made from renewable resources which isnowadays seen as one of the most promising polymers forcommercial use as a substitute for low-density polyethylene(LDPE) and high-density polyethylene (HDPE), polystyrene(PS) and polyethyleneterephthalate (PET). It is produced byconversion of corn, or other carbohydrate sources, intodextrose, followed by a fermentation into lactic acid.Through direct polycondensation of lactic acid monomersor through ring-opening polymerization of lactide, PLA pel-lets are obtained. Since lactic acid exist as two optical iso-mers, L- and D-lactic acid, three different stereochemicalcompositions of lactide can be found, i.e. L,L-lactide, D,D-lactide and L,D-lactide. This stereochemical composition de-termines the final properties of the polymer. The processingpossibilities of this transparent material are very wide,ranging from injection molding and extrusion over castfilm extrusion to blow molding and thermoforming(Bogaert & Coszach, 2000; Drumright, Gruber, & Henton,2000; Jamshidian, Tehrany, Imran, Jacquot, & Desobry,2010; Joshi, 2008; Liu, 2006; Rasal, Janorkar, & Hirt,2010; Siracusa et al., 2008; S€odergard & Stolt, 2002).

StarchStarch is a widely available and easy biodegradable natural

resource. To produce a plastic-like starch-based film, high-water content or plasticizers (glycerol, sorbitol) are necessary.These plasticized materials (application of thermal and me-chanical energy) are called thermoplastic starch (TPS) andconstitute an alternative for polystyrene (PS). Starch-basedthermoplastic materials (e.g. blends of TPS with synthetic/biodegradable polymer components, like polycaprolactone,polyethylene-vinyl alcohol or polyvinyl alcohol) have beensuccessfully applied on industrial level for foaming, filmblowing, injection molding, blow molding and extrusion ap-plications (Bastioli, 1998; Chivrac, Pollet, & Av�erous, 2009;Joshi, 2008; Mensitieri et al., 2011; Weber, 2000).

PHAThe polyhydroxyalkanoates (PHA) family are biode-

gradable thermoplastic polymers, produced by a wide rangeof microorganisms. The polymer is produced in the micro-bial cells through a fermentation process and then harvestedby using solvents such as chloroform, methylene chlorideor propylene chloride. More than 100 PHA compositesare known, of which polyhydroxybutyrate (PHB) is themost common. The PHAs have potential as a substitutefor many conventional polymers, since they possess similarchemical and physical properties (Cyras, Commisso, &V�azquez, 2009; Farinha, 2009; Lunt, 2009; Sanchez-Garcia, Gimenez, & Lagaron, 2008; Singh, 2011).

130 N. Peelman et al. / Trends in Food Science & Technology 32 (2013) 128e141

CelluloseCellulose is the most widely spread natural polymer and

is derived by a delignification from wood pulp or cottonlinters. It is a biodegradable polysaccharide which can bedissolved in a mixture of sodium hydroxide and carbon di-sulphide to obtain cellulose xanthate and then recast into anacid solution (sulfuric acid) to make a cellophane film.Alternatively, cellulose derivatives can be produced byderivatization of cellulose from the solvated state, via ester-ification or etherification of hydroxyl groups. Especiallythese cellulose derivatives were the subject of recentresearch. Cellulose esters like cellulose (di)acetate and cel-lulose (tri)acetate need addition of additives to producethermoplastic materials. Most of them can be processedby injection molding or extrusion. Cellulose ethers like hy-droxypropyl cellulose and methyl cellulose are water-soluble, except for ethyl cellulose and benzyl cellulose.Ethyl cellulose can be used for extrusion, laminating ormolding after addition of plasticizers or other polymers.Most of these derivatives show excellent film-formingproperties, but are too expensive for bulk use (Cyraset al., 2009; Liu, 2006; Petersen et al., 1999; Shen,Haufe, & Patel, 2009; Weber, 2000; Zepnik, Kesselring,Kopitzky, & Michels, 2010).

Other materialsThe main advantages and disadvantages of some other

raw materials are listed in Table 1.

Main limitationsThe use of bioplastics as food packaging materials is

subjected to different limitations, restricting at this moment

Table 1. Raw materials, their origin and their advantages and disadvantag

Raw material Origin Advantages

Zein Main protein of corn - Good film-forming properties

dissolving in ethanol and acet

- Good tensile and moisture bar

properties

Chitosan Derivative of chitin - Antimicrobial and antifungal

- Good mechanical properties

- Low oxygen and carbon dioxi

permeability

Soy proteinisolate(SPI)

Derived from soybean

Whey proteinisolate

Waste stream ofcheese industry

- Good oxygen (comparable to

and aroma barrier

(Wheat) Glutenderived films

Waste stream of wheatstarch industry

- Low cost

- Good oxygen barrier

- Good film-forming properties

their use. Besides a higher price level compared to conven-tional plastics, the concerns on availability as well as on theuse of land to produce bioplastics, there are major limita-tions on the functionality.

Brittleness, thermal instability, low melt strength, diffi-cult heat sealability, high water vapor and oxygen perme-ability restrict the use of PLA films for many foodpackaging applications (Cabedo, Feijoo, Villanueva,Lagar�on, & Gim�enez, 2006; Jamshidian et al., 2010;Mensitieri et al., 2011; Rhim, Hong, & Ha, 2009).

Because of the hydrophilic nature of starch and cellu-lose, packaging materials based on these materials have alow water vapor barrier, which causes a limited long-termstability and poor mechanical properties (sensitive to mois-ture content). Other drawbacks are bad processability, brit-tleness and vulnerability to degradation (Cyras et al., 2009;G�asp�ar, Benk�o, Dogossy, R�eczey, & Czig�any, 2005; Joshi,2008; Liu, 2006; M€uller, Laurindo, & Yamashita, 2011;Shen et al., 2009; Yu, Dean, & Li, 2006).

Brittleness (due to high glass transition and melting tem-peratures), stiffness, poor impact resistance and thermalinstability are finally also factors limiting the applicationof PHA/PHB films as food packaging (Cyras et al., 2009;Liu, 2006; Modi, 2010; Yu et al., 2006).

This has resulted in increasing research on improvingthe functionality of bioplastics, which is described in thenext paragraph.

Improving the properties of bioplasticsA large amount of studies have investigated different

strategies to improve the properties of bioplastics. Specif-ically in terms of increasing barrier capacities toward

es.

Disadvantages Reference

after

one

rier

- Brittle (use of plasticizers

can overcome this)

Ghanbarzadeh et al.(2006),Sozer and Kokini (2009)

activity

de

- High water sensitivity Darmadji and Izumimoto(1994),Jo, Lee, Lee, and Byun(2001),Suyatma et al. (2004)

- Poor mechanical properties

- High sensitivity to moisture

Rhim et al. (2007)

EVOH) - Moderate moisture barrier

- Plasticizer necessary to create

easy to handle films

Galietta et al. (1998),Kokoszka, Debeaufort,Lenart, and Voilley(2010), Mat�e & Krochta(1996), McHugh, Aujard,and Krochta (1994),McHugh, Aujard, andKrochta and Krochta(1994)

- High sensitivity to moisture

- Brittle

Zhong & Yuan (2013),T€ure, G€allstedt, andHedenqvist (2012)

131N. Peelman et al. / Trends in Food Science & Technology 32 (2013) 128e141

gasses and water, following techniques, described in detailin subsequent paragraphs, could be used.

CoatingIn general, it can be stated that coating biobased films is

a suitable tool to improve the properties of these films.Coating consists of applying an additional thin layer ofanother material on top of the biobased films. As illustratedby the examples below, especially the barrier properties,like oxygen and water vapor permeability and oil andgrease resistance and to a lesser extent mechanical proper-ties, like tensile strength and elasticity can be enhanced byapplying such a coating. Different types of coating, bio-based and non-biobased, can be used.

The coating of PLA with PLA-Si/SiOx, PCL-Si/SiOx(polycaprolactone) or PEO-Si/SiOx (polyethylene oxide)enhanced the barrier (oxygen and water vapor) properties,which makes the PLA films applicable as a packaging ma-terial for medium shelf life products in combination withmodified atmosphere packaging (MAP) (sliced processedmeat, fresh meat, cheeses, vegetables) (Iotti, Fabbri,Messori, Pilati, & Fava, 2009). Similarly, Hirvikorpi,V€ah€a-Nissi, Nikkola, Harlin, and Karppinen (2011) re-ported that a thin (25 nm) AlOx-coating can significantlyimprove the water vapor and oxygen barrier of several poly-mers (PLA-coated board, PLA film, nano-fibrillated cellu-lose film, PHB). PLA-coated paperboard (PLA: 35 g/m2)coated with AlOx showed decreasing OTR values from420 to 12 and 400 to 2 cm3/m2/105 Pa/day for respectively310 g/m2 board and 210 g/m2 board. The WVTR valuesdecreased from 65 to 1 and 75 to 1 g/m2/day for respec-tively 310 g/m2 board and 210 g/m2 board.

Coating of SPI films with PLA raised the tensile strengthfrom 2.8 MPa up to 17.4 MPa and the elongation from165.7% up to 203.4%. Water vapor permeability decreased20- to 60-fold, depending on the PLA concentration in thecoating solution (Rhim, Lee, & Perry, 2007).

Coating of an acetylated cellulose film with PHB re-sulted in lower WVP values, higher elastic modulus andtensile strength for films containing 10% or more PHBand better strain at break for films containing 15% ormore PHB (Cyras et al., 2009). A nitrocellulose or PVdCcoating on cellophane improved both O2 and H2O barrierproperties (Shen et al., 2009). In general, Popa and Belc(2007) stated that chitosan may be used as a biobasedcoating on polymers with poor gas barrier properties.

BlendsNanotechnology

General information. Nanotechnology is generally definedas the creation and utilization of structures with at least onedimension in the nanometer length scale (10�9 m). Thesestructures are called nanocomposites and could exhibit mod-ifications in the properties of the materials or create novelproperties and phenomena to the materials. To achieve these

modifications, a good interaction between the polymer ma-trix (continuous phase) and the nanofiller (discontinuousphase) is desired (Lagaron & Lopez-Rubio, 2011).

Incorporation of the filler into the polymer matrix can beachieved using in situ polymerization (dissolution of thenanoparticles in the monomer solution before polymeriza-tion), solvent intercalation (use of a solvent to enhancethe affinity between the nanoparticles and the matrix) andmelt intercalation (addition of the nanoparticles duringextrusion) (Chivrac et al., 2009; Shen, Simon, & Cheng,2002).

Among the different nanoparticles which could be usedto reinforce a biopolymer, nanoclays have attracted mostattention. These nanoclays, like montmorillonite, belongto the family of phyllosilicates and have a structure basedon the pyrophillite structure Si4Al2O10(OH)2. They are ag-gregates of stacked, ultrafine layered particles (tactoids).The thickness of one layer (or platelet) is in the order of1 nm. Depending on the interaction between the contin-uous and the discontinuous phase, different polymereclayinteractions occur: tactoid, intercalated and exfoliated.When the affinity between the clay and the polymer israther low, the clay interlayer does not expand and theclay tactoid structures remain as such in the polymer ma-trix. In this way, no true nanocomposite is formed. Whenthe affinity between the clay and the polymer is moderate,medium expansion of the clay interlayer occurs. The poly-mer can partly penetrate the clay interlayer, leading to anintercalated structure, which is still a layered structure.When the affinity between the clay and the polymer ishigh, the layered structure of the clay is lost and an exfo-liated structure is formed by dispersion of the clay into thepolymer matrix (Arora & Padua, 2010; Chivrac et al.,2009).

Since a high surface-to-volume ratio has the greatest ef-fect on the properties of the polymer, the exfoliated struc-ture is the ultimate goal. A good dispersion is affected bythe hydrophobic/hydrophilic character of the polymer andthe clay. Different chemical modification to make the sur-face of the nanoclay more hydrophobic, such as cationicexchange, use of ionomers, block copolymers adsorptionand organosilane grafting, are sometimes necessary toimprove intercalation/exfoliation into the polymer matrix.Also modification of the polymer and/or adding compatibi-lizing agents can lead to a more homogenous dispersion(Arora & Padua, 2010; Chivrac et al., 2009; Silvestre,Duraccio, & Cimmino, 2011).

Effect of the use of nanoparticles on materialproperties. Incorporation of nanoparticles is an excellentway to improve the performance of biobased films. Fromthe examples discussed below it can be concluded thatalmost all the shortcomings, which limit the use of bio-based plastics as food packaging, can be overcome bymaking use of this technique. However, an importantpossible drawback is, at least partly, the reported negative

132 N. Peelman et al. / Trends in Food Science & Technology 32 (2013) 128e141

effect on the elongation at break, especially in PLA films.The effect of the incorporation of nanoparticles, espe-cially on the barrier properties, can be explained by the‘confinement effect’. Polymer molecules can be‘confined’ between the dispersed nanoparticles, providinga tortuous path, forcing the water and gas molecules totravel a longer path for diffusion through the film, therebyimproving the barrier properties. The thermal stabilitycan be explained by a slower diffusion of volatile decom-position products within the nanocomposite (Damme,2008; Kumar, Sandeep, Alavi, & Truong, 2011; Nielsen,1967; Silvestre et al., 2011).

Properties of PLA/clay composite films can be improvedby choosing the proper type of nanoclay and its optimumconcentration (Rhim et al., 2009). Oxygen barrier proper-ties of amorphous PLA increased by 50% by using chemi-cally modified kaolinite. Addition of kaolinite nanofillers toPLA films is a feasible strategy to improve both thermalstability and mechanical properties (Bentz, 2011; Cabedoet al., 2006). Combination of PLA with montmorillonite-layered silicate ameliorated the barrier properties andmade it applicable for food packaging (Arora & Padua,2010). Strength and modulus of a PLA matrix increasedby applying bentonite but it deteriorated the elongation(Petersson & Oksman, 2006). Sanchez-Garcia et al.(2010a) observed that addition of mica-based nanoclaysto PLA caused a diminished UV transmittance. Addingzeolite type 4 particles enhanced the tensile strength andmodulus of elasticity, but lowered the elongation at break.The changes occurred proportional to the zeolite loading(Yuzay, Auras, & Selke, 2009).

Incorporation of organically modified montmorillonite(OMMT, Cloisite) into thermoplastic starch (TPS) raisedthe tensile strength with 28%, the elongation at breakwith 21% and reduced the water vapor permeability with50% (Park, Lee, Park, Cho, & Ha, 2002). Avella et al.(2005) reported similar results. Addition of clay (montmo-rillonite) to TPS increased tensile strength, elongation atbreak and Young modulus at 15% relative humidity(RH), but only increased tensile strength and Youngmodulus at 60% RH. Mixing of this bionanocompositewith Ecoflex had a negative impact on the reinforcing ef-fect of the clay, but heightened the elongation at breakeven more.

Sanchez-Garcia and Lagaron (2010a) reported a lowerwater and oxygen permeability and a good UV-barrier ofa poly(3-hydroxybutyrate-hydroxyvalerate) (PHBV) filmafter incorporation of a mica-based clay. Reductions in wa-ter permeability of 61%, 76% and 47% were found forrespectively 1 wt%, 5 wt% and 10 wt% of clay. A reductionin oxygen permeability of 32% was found for 5 wt% ofclay. Raising the clay content did not result in furtherdecrease of the oxygen permeability. PHBV films with 1,3, 5 and 10 wt% of carbon nanofibers resulted in respec-tively 14, 5, 21 and 58% lower oxygen permeability, while1, 5 and 10 wt% of nanotubes decreased the oxygen

permeability with respectively 62, 10 and 33% (Sanchez-Garcia et al., 2010b).

Incorporation of chitosan nanoparticles in hydroxypropylmethyl cellulose (HPMC) resulted in better tensile strength(from 30.7 to 66.9 MPa) and barrier properties (De Moura,Avena-Bustillos, McHugh, Krochta, & Mattoso, 2008).Similarly, mixing of MMT (montmorillonite) with TPZ(thermoplastic zein) resulted in improved mechanical prop-erties. Stress at break increased from 6.68MPa to 13.98MPafor respectively pure TPZ and TPZþ 10%MMT (Mensitieriet al., 2011).

Migration and legal issues. Incorporation of nanoclays inbiobased food packaging has a high potential, but beforethese new materials can be commercially used, the extentof migration of the nanoclays from the packaging materialinto the food has to be investigated. Up to now, only fewstudies on the migration of nanoclays from biobased pack-aging to food are present in literature. Avella et al. (2005)found very low migration of MMT from films of potato-starch and potato starch polyester blends into foodsimulants. Also Mauricio-Iglesias, Peyron, Guillard, andGontard (2010) reported low migration of MMT fromwheat gluten/MMT films into food simulants. Althoughthese results are reassuring, the current knowledge onmigration of nanoclays and their effect on the humanhealth and environment is too limited and further researchis necessary before these products can be put on themarket for use as a food packaging material (Silvestreet al., 2011; Sorrentino, Gorrasi, & Vittoria, 2007).

At present, no specific regulation for nanoparticles is es-tablished, meaning that Regulation (EC) 1935/2004 is stillapplicable for nanomaterials. In 2009, EFSA concluded itsassessment of the potential risks of nanotechnologies forfood and feed, stating that a cautious, case-by-caseapproach is needed as many uncertainties remain over itssafe use (Silvestre et al., 2011; Sorrentino et al., 2007).

CelluloseAnother way to improve the properties of biobased films

is the addition of the biopolymer cellulose. The most pro-nounced effect of this embodiment was the reduced watervapor permeability, but also several mechanical properties,like tensile strength and Young’s modulus were influenced.Also here, the crucial point seems to be the elongation atbreak.

Dias, M€uller, Larotonda, and Laurindo (2011) andM€uller, Laurindo, and Yamashita (2009) observed that theincorporated cellulose fibers were well cemented inthe plasticized starch polymer matrix. This is because thechemical similarity between starch and natural fibers pro-vides a strong interaction (Av�erous, Fringant, & Moro,2001; Lu, Weng, & Cao, 2006). The positive effect of theincorporation of cellulose fibers on the water permeabilityof (starch-based) films is related to the highly crystallineand hydrophobic character of the fibers. As for the

133N. Peelman et al. / Trends in Food Science & Technology 32 (2013) 128e141

nanoclays, addition of cellulose fibers decreases the watervapor transmission by increasing the diffusion path lengththrough the film (tortuous path). However, this effect canbe reversed by adding too much fibers, causing congrega-tion (Kristo & Biliaderis, 2007; M€uller et al., 2009).

Addition of cellulose fibers to starch-based films (madeof rice flour) diminished the water vapor permeability with35% (plasticized with glycerol) or 14% (plasticized withsorbitol) and increased the tensile strength and Young’smodulus, without altering the elongation at break (Diaset al., 2011). M€uller et al. (2009) also found reinforcementof starch films and lower water vapor permeability afterincorporation of cellulose fibers. Also, application of car-boxymethyl cellulose (CMC) in starch-based films showeda decrease of the water vapor permeability with increasingCMC content (Ghanbarzadeh, Almasi, & Entezami, 2011).Addition of 5 wt% ZnO-CMC to plasticized pea starchimproved tensile strength (from 3.9 to 9.8 MPa) and watervapor permeability, but reduced the elongation at break(from 42.2 to 25.8%) (Yu, Yang, Liu, & Ma, 2009).

G�asp�ar et al. (2005) tested the effect of different natu-ral additives (cellulose, hemicellulose, zein and poly-ε-caprolactone) on the water resistance of a starch-basedfilm (70% corn starch þ 30% glycerol). Hemicelluloseand zein filled starch-based film showed better tensilestrength and modulus than the pure film, but elongationof all four filled films was lower than the pure TPS (ther-moplastic starch). Water resistance of cellulose, hemicel-lulose, zein and polycaprolactone filled films was bettercompared to pure TPS, but the zein filled film showedthe lowest water uptake after 14 days.

Sanchez-Garcia et al. (2008) investigated the effect ofcellulose fibers in PHBV films. Water permeabilitydecreased with 52% for 10 wt% fiber content and with71% for 1 wt% fiber content. Alternatively, Cyras,Commisso, Mauri, and V�azquez (2007) investigated the in-fluence of PHB on cellulose paper and found that additionof PHB with more than 10 wt% had a positive influence onwater vapor permeability (WVP) and on the mechanicalstrength of the cellulose paper.

According to Petersson and Oksman (2006) incorpora-tion of microcrystalline cellulose (MCC) showed no reduc-tion in the oxygen permeability of PLA. In contrast,Sanchez-Garcia and Lagaron (2010b) found up to 90% ox-ygen permeability reduction for PLA after addition of 1, 2,3, or 5 wt% cellulose nanowhiskers (CNW).

OthersVarious other materials can be used to improve the prop-

erties of a biobased material. Several of them are describedin the following paragraphs. Among them, especiallyblends of two biobased materials seems to have a great po-tential. When blending materials, compatibility is a majorchallenge. Enhancing this compatibility for immisciblepolymers can be done by the introduction of a reactivefunctional group, chemical modification (e.g. of the

hydroxyl groups of starch with a hydrophobic compound)or esterification (Thiebaud et al., 1997). Although most ofthe blended polymers seemed immiscible and/or incompat-ible (see next paragraph), positive effects of blending wereobserved.

Although PLA and PCL were clearly immiscible,Cabedo et al. (2006) observed no extensive voiding and de-bonding at the interphase, suggesting some sort of compat-ibility. Suyatma, Copinet, Tighzert, and Coma (2004) foundthat chitosan and PLA were immiscible and incompatible,due to the absence of specific interaction between bothpolymers. This incompatibility leads to decreased mechan-ical properties when blending those two polymers. A blendof PHB/PLA prepared by casting after dissolution in chlo-roform (3% w/v), evaporation at room temperature and vac-uum drying for 24 h, suggested immiscibility of bothpolymers in the amorphous state. Melt blending, evapora-tion under reduced pressure and maintaining the blend at190 �C for 30 min implied greater miscibility. A possibleexplanation is that transesterification between PHB andPLA chains at 190 �C leads to the production of block co-polymers. These polymers will act to compatibilize bothpolymers and improve their miscibility (Zhang, Xiong, &Deng, 1996). Furthermore, also PHB and HV and PHBVand PLA seemed to be mostly immiscible, although someinteractions between the polymers were observed. HigherPLA concentrations lead to more compatibility, but renderthe material more difficult to process (Modi, 2010). Incontrast with the above, starch and PHB have been reportedto be significantly compatible (Koller & Owen, 1996).

Blending PLA with PCL (polycaprolactone) reduces thebrittleness and slightly increases the thermal stability of thePLA film, but decreases the barrier properties proportionalto the amount of PCL added. Loss of barrier properties canbe reversed by adding kaolinite nanoclays. Combination ofPLA with starch, plasticizers (glycerol/sorbitol) or otherdegradable polyesters can diminish the brittleness of thefilm (Cabedo et al., 2006). Addition of PLA to a chitosanfilm had a positive effect on water vapor permeability andsensitivity to moisture, but decreased the tensile strengthand elasticity modulus (Suyatma et al., 2004).

Incorporation of 3-hydroxyvalerate (HV) in PHB, result-ing in PHBV, increased the impact strength, elongation atbreak, tensile strength and decreased the Young’s modulus,making the film tougher and more flexible, with increasingHV content (Modi, 2010; Shen et al., 2009). BlendingPHBV with PLA had a positive effect on elasticitymodulus, elongation at break, flexural strength for manydifferent blends, but tensile strength did not improve inany of them. Similarly, Zhang et al. (1996) reportedimproved mechanical properties for PHB/PLA blendscompared with ordinary PHB. Further, PVA (polyvinylace-tate) grafted on PIP (poly-cis-1,4-isoprene) and blendedwith PHB showed better tensile properties and impactstrength than PHB/PIP blends, which were immiscible(Modi, 2010; Yoon et al., 1999).

134 N. Peelman et al. / Trends in Food Science & Technology 32 (2013) 128e141

Thermoplastic starch (TPS) blended with PHA had a pos-itive effect on barrier properties and hydrolytic and UV sta-bility of the starch-based film and diminished processingtemperature resulting in less starch degradation (Shenet al., 2009). Blends of TPS with natural rubber appearedto be less brittle than TPS alone (Yu et al., 2006). Additionof locust bean gum (LBG) improved the tensile strength,but lowered the elongation of starch-based films. However,elongation significantly improved after gamma irradiation.Also the WVP improved with increasing irradiation dose(Kim, Jo, Park, & Byun, 2008). Blending agar with starchhad a positive effect on the microstructure of the starchfilm. WVP and mechanical properties were enhanced (Wu,Geng, Chang, Yu, & Ma, 2009). Fam�a, Gerschenson, andGoyanes (2009) stated that blending starch with wheatbran reduced theWVP of the film and improved the mechan-ical properties with increasing wheat bran fiber content.

Chemical/physical modificationAnother way to improve the performance of bioplastics

is by chemical and/or physical modification. Modificationcan have a positive effect on mechanical properties and wa-ter vapor permeability of materials as such, but modifica-tion can also be a tool to enhance compatibility betweentwo polymers. For the latter, mostly starch has been modi-fied to improve their hydrophobicity, making them morecompatible with hydrophobic materials.

WVP of starch films decreased after addition of citricacid. A 10% (w/w) citric acid content showed the greatestreduction. This can be explained by the multi carboxyl struc-ture of citric acid. These groups can interact with the hydrox-yl groups of the starch, which results in a reduction ofavailable OH groups. Furthermore, strong hydrogen boundscan be formed, preventing retrogradation and recrystalliza-tion. Mechanical properties can also be improved, becausecitric acid can serve as a cross-linking agent(Ghanbarzadeh et al., 2011; Shi et al., 2008; Thiebaudet al., 1997). Oxygen permeability and hydrophobicity ofmicrofibrillar cellulose (MFC) films can be improved byacetylation with acetic anhydride. Film thicknesses between42 and 47 mm lead to oxygen permeability values requiredfor modified atmosphere packaging application(Rodionova, Lenes, Eriksen, & Gregersen, 2011).

Flexible and water resistant starch films can be made byheating gelatinized starch in an anhydrous suspension withlithium chloride in the presence of an organic solvent (Fanget al., 2005).

Chemical modification by cross-linking cellulose acetatewith tri-sodium tri-meta phosphate led to materials withimproved mechanical properties (higher tensile strength),lower water up take and slower degradation kinetics. Thiscan be explained by the cross-linking of some of the hy-droxyl groups that were present in the cellulose acetateblend (Demirg€oz et al., 2000).

Incorporation of starch modified by epichlorohydrin incomparison with native starch in an LLDPE film resulted

in higher tensile strength and elongation. Crosslinked starchis more hydrophobic because it has more carbon chainsthan native starch. This causes better compatibility of thestarch with the LLDPE film (Kim & Lee, 2002). Yin, Li,Liu, and Li (2005) found that boric acid serves as an excel-lent cross-linking agent for starch with poly (vinyl alcohol)(PVA). A film with good water resistance and mechanicalproperties could be made.

According to Gennadios, Weller, and Testin (1993) thewater vapor and oxygen barrier properties of a wheat glutenderived film can be improved by partial substitution of thewheat gluten with hydrolyzed keratin, probably due to link-ages between the two proteins. A better water vapor barrierwas also obtained by soaking a wheat gluten film in CaCl2and then in distilled water or by soaking it in a solution at apH of 7.5. These processes also provided higher tensilestrength and are probably caused by respectively cross-linking of Ca2þ in the film structure and by protein insolu-bility at a pH equal to the isoelectric point of wheat gluten.According to Rhim, Gennadios, Fu, Curtis, and Milford(1999) UV irradiation of a wheat gluten based filmincreased the tensile strength by 20%, suggesting cross-linking within the film structure. However, the cross-linking seemed insufficient for an effect on the WVP.

Possible applicationSeveral studies have investigated the possible use of bio-

based material for food packaging, especially in compari-son with traditional packaging materials. At present itappears that mainly for fresh (respiring) produce, like fruitsand vegetables, fresh meat and fresh juices various bio-based options are available, but also fat rich products couldbe packed in biobased packaging. For these products, bio-based packaging can even have a positive effect on thefood product in comparison to the conventional packaging.It can be concluded that at present the main focus for bio-based packaging are short shelf life applications and dryproducts that do not require high oxygen and/or water va-por barrier.

PLASeveral studies on PLA based packaging have shown that

they could replace some of the conventional packaging for anumber of food products. Koide and Shi (2007) evaluated themicrobiological and physicochemical quality of whole greenpeppers packed in a PLAbased film (Tohcello, 25 mm, Japan)compared to LDPE and perforated LDPE. Results showed nosignificant difference in hardness, ascorbic acid concentra-tion and color after 1 week of storage at 10 �C, but for thePLA film coliform bacteria counts were lower. Fresh cutromaine lettuce can be packed in thermoformed orientedPLA (OPLA) during storage at 10 �C (Benyathiar et al.,2009). Almenar, Samsudin, Auras, Harte, and Rubino(2008, Almenar, Samsudin, Auras, and Harte, 2010) statedthat PLA containers (Versapack�, 8 oz.,Wilkinson IndustriesInc., USA) are possibly applicable for commercial post

135N. Peelman et al. / Trends in Food Science & Technology 32 (2013) 128e141

harvest packaging of blueberries. In contrast to the conven-tional PET container, an equilibrium modified atmospherecould be developed inside the PLAcontainers. This increasedthe shelf life of the blueberries. Sensory evaluations showedthat consumers preferred blueberries packed in PLA con-tainers for one or two weeks over the blueberries packed inconventional containers. Haugaard, Weber, Danielsen, andBertelsen (2002) reported that PLA packaging (thermo-formed cups, Autobar, France) is suitable for storage of fresh,unpasteurized orange juice at 4 �C for 14 days. Colorchanges, ascorbic acid (AA) degradation and limonenescalping were most effectively prevented by PLA whencompared to PS and HDPE.

StarchResearch on starch-based films has shown that they could

be suitable alternatives to conventional plastics for differentfood products. Cannarsi, Baiano,Marino, Sinigaglia, andDelNobile (2005) demonstrated that two biodegradable filmsbased on starch (1 blend of starch and polyester and 1 blendof 3 biodegradable/biobased polyesters, Novamont, Italy)could be used to replace PVC films to pack fresh cut beefsteaks. Furthermore, Ifezue (2009) found Mater-Bi� (blendof starch with biodegradable synthetic polymers like PCL

Table 2. Current applications of bioplastics.

Packaging application Biopolymer C

PLACoffee and tea Cardboard cups coated with PLA KBeverages PLA cups MFresh salads PLA bowls MCarbonated water, freshjuices, dairy drinks, .

PLA bottles B

Freshly cut fruits, wholefruits, vegetables, bakerygoods, salads

Rigid PLA trays and packs A

Organic pretzels, potato chips PLA bags SP

Yoghurt PLA jars S

Frozen fries PLA films (Bio-Flex) MOrganic fruit and vegetables PLA packaging MPasta PLA packaging BHerbs PLA packaging APrepared sandwiches,pasta salads

PLA bowls, packaging D

Bread Paper bags with PLA window DOrganic poultry PLA bowls, absorb pads D

Starch-basedMilk chocolates Cornstarch trays C

foOrganic tomatoes Corn-based packaging Ip

CCelluloseKiwi Biobased trays wrapped

with cellulose filmW

Potato chips Metalized cellulose film BOrganic pasta Cellulose-based packaging BSweets Metalized cellulose film Q

or PVOH) to be superior to perforated LDPE, PLA and Eco-flex to packwhole fresh celery, especially regardingmechan-ical performance. Also Kantola and Helen (2001) stated thatthe quality of tomatoes packed in PLA-coated cardboardcovered with a perforated Mater-Bi� bag remained as goodas when packed in LDPE (low-density polyethylene) bagsduring 3 weeks.

PHA/PHBReplacement of conventional films by PHA/PHB based

films could be possible according to several investigations.Levkane, Muizniece-Brasava, and Dukalska (2008) investi-gated the effect of pasteurization on a meat salad packed inconventional (PE, PP) and biobased packaging (PLA, PHB)and found that PHB films could be successfully used topack this type of food. Haugaard, Danielsen, andBertelsen (2003) found that orange juice simulant and dres-sing packed in PHB resulted in the same quality changescompared to HDPE, which means commercial juices andother acidic beverages and dressings or other fatty foodscould possibly be packed in PHB. Furthermore, Bucci,Tavares, and Sell (2005) stated that PP can be replacedby PHB for packaging of fat rich products (mayonnaise,margarine and cream cheese) according to physical,

ompany Reference

LM Jager (2010)osburger (Japan) Sudesh and Iwata (2008)cDonald’s Haugaard et al. (2003)iota, noble, . Sudesh and Iwata (2008)

sda (retailer) Koide and Shi (2007)Jager (2010)

nyder’s of Hanover,epsiCo’s Frito-lay

Weston, 2010

tonyfield (Danone) Haugaard et al. (2001), Jager(2010)

cCain Nieburg, 2010ont Blanc Primeurs Highlights in bioplasticsiorigin Highlights in bioplasticssda (retailer) Highlights in bioplasticselhaize (retailer) Delhaize-press release (2007)

elhaize (retailer) Delhaize-press release (2007)elhaize (retailer) Delhaize-press release (2007)

adbury Schweppesod group, Marks & Spencer

Highlights in Bioplastics,website European bioplastics

er supermarkets (Italy),oop Italia

Highlights in Bioplastics,website European bioplastics

al-Mart Blakistone and Sand (2007)

oulder Canyon Website European bioplasticsirkel Website European bioplasticsualitystreet, Thornton Website European bioplastics

Table 3. Main characteristics multilayered biobased films.

Film Shape(tr [ transparant)n-tr [ nontransparant)

Permeability Thicknessa

(mm)Seal conditionsb Modulus c (Mpa) Tensile strain at breakc (%)

O2a (cc/m2 d)

23�C e 75% RHH2O

a (g/m2 d)38�C e 90% RH

T P t

(�C) kN/m2 (s) MD TD MD TD

Natureflex� N913(cellulose-based)

Flex. film (tr) 9.9 10.1 55 100e170 69 0.5 >3000 >1500 22 70

Natureflex� N931(cellulose-based)

Flex. film (n-tr) 3.4 5.0 44 120e170 69 0.5 >3000 >1500 20 44

Ecoflex þ Ecovio/Ecovio/Ecoflex þEcovio

Flex. film (n-tr) 815.0 216.4 55 70e85 400 1.6 596.8 � .3 8.1 � 2.0 294.0 � 27.0 316.8 � 43.3

Metallized PLA Flex. film (n-tr) 25.4 2.3 20 70e80 411 1.6 2289.6 � 54.1 3270.5 � 307.0 5.1 � 0.7 5.9 � 0.3Cellophane�/Metallayer/PLA

Flex. film (n-tr) 9.1 9.7 46 105 420 1.6 2885.8 � 5.4 2256.7 � 65.3 30.4 � 1.1 45.5 � 9.5

Paper/AlOx/PLA Flex. film (n-tr) 45.7 6.0 91 120 600 1 2394.8 � 63.7 1276.9 � 113.1 6.1 � 0.4 9.4 � 0.5Bioska 504(multilayer PLA)

Flex. film (tr) 617.6 275.1 34 60 414 1,6 921.3 � .7 924.7 � 94.6 185.3 � 9.3 169.7 � 59.9

Natureflex�/PLA Flex. film (tr) 11.01 11.3 60 60e75 415 1.6 942.4 � .4 718.9 � 12.6 30.8 � 3.8 99.7 � 10.0Cellophane�/PLA Flex. film (tr) 10.5 13.8 100 60e80 420 1.6 534.2 � .5 571.5 � 35.8 43.6 � 4.7 99.5 � 5.5PHB/Ecoflex Flex. film (tr) 142.1 80.6 87 70e80 410 1.6 146.7 � .0 109.4 � 7.1 701.2 � 60.4 721.6 � 30.0Xylophane A(coated on paper)

Flex. film (n-tr) 3.7 24.3 100(coating ¼ 9)

170* /f / 593.7 � .5 / 8.3 � 0.4 /

Xylophane B(coated on paper)

Flex. film (n-tr) 6.0 23.9 100(coating ¼ 9)

170* / / 618.6 � .1 / 8.0 � 0.1 /

PLA tray Tray (tr) 46.8 3.8 200e300 / / / / / / /

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E

54

27

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12

Film Tensile stress at breakc (N/mm2) Print-ability Used Food approved(1935/2004)

Biobased(Vincotte)e

Origin Provider

MD TD Cooling Freezer Pasteurization

Natureflex� N913(cellulose-based)

125 70 YES OK NO NO YES ** Non-food Bastin-Pack nv,Be_Natural

Natureflex� N931(cellulose-based)

80 45 YES OK OK NT YES **** Non-food Be_Natural

Ecoflex þ Ecovio/Ecovio/Ecoflex þ Ecovio

23.1 � 0.2 19.9 � 0.9 YES OK OK NT YES ** Non-food þ corn BPI Formipac

Metallised PLA 66.4 � 7.8 86.7 � 6.2 YES OK OK NO YES **** corn VitraCellophane�/M/PLA 98.8 � 1.7 71.1 � 4.9 / NT NT NT / **** Non-food þ corn Be_NaturalPaper/AlOx/PLA 79.0 � 1.7 54.7 � 3 YES NT NT NO YES **** corn Be_NaturalBioska 504 (multilayer PLA) 23.9 � 0.6 20.5 � 2.4 YES OK OK NO YES **** Be_NaturalNatureflex�/PLA 56.2 � 1.2 34.0 � 1.1 / NT NT NT / *** Non-food þ corn Segers&BalcaenCellophane�/PLA 54.5 � 1.4 35.2 � 0.7 / NT NT NT / *** Non-food þ corn Segers&BalcaenPHB/Ecoflex 25.5 � 1.8 21.0 � 1.1 / NT NT NT Food contact

safe**** corn þ cereals Roychem BVBA

Xylophane A (coatedon paper)

32.4 � 1.0 / / NO NO NO NT **** Non-food Xylophane

Xylophane B (coatedon paper)

34.3 � 0.5 / / NO NO NO NT **** Non-food Xylophane

PLA tray / / / / / / / / / HoGent

a Measured at Packaging Center, Xios Hogeschool, Hasselt, Belgium/From technical sheet.b Measured at Belgian Packaging Institute (IBE-BVI), Zellik, Belgium.c Meaured at University College Ghent, Ghent, Belgium (except Natureflex N913 and N931).d NT ¼ not tested.e 20e40% biobased ¼ *, 40e60% biobased ¼ **, 60e80% biobased ¼ ***, >80% biobased ¼ ****.f /¼ no information or not yet tested.

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mechanical (dynamic compression and impact resistance),sensorial and dimensional (dimensions, volumetric capac-ity, weight and thickness) tests. Similarly, Muizniece-Brasava and Dukalska (2006) stated that PHB materialsare suitable materials for storage of sour cream.

CelluloseDifferent studies on cellulose-based films showed that

they could be an alternative for packaging several foodproducts. Popa and Belc (2007) stated that paper and board,based on cellulose, are the most widely used renewablepackaging materials nowadays. Also a lot of cellulose de-rivatives are produced commercially, of which cellulose ac-etate (CA) is the most commonly used for food packaging(fresh produce, baked goods).

Makino and Hirata (1997) showed that a laminate ofchitosan-cellulose and PCL had a similar film permeabilityas LDPE, which makes this laminate a possible MAP pack-aging for fresh produce (shredded lettuce, cabbage, to-matoes, sweet corn and broccoli). Usability wasconfirmed by computer simulation. Popa and Belc (2007)found that coating of cellophane with nitrocellulose orPVdC (polyvinylidine chloride) improved barrier propertiesand this film could be used for packaging of candies, pro-cessed meat, cheese and baked goods. Furthermore, Rhimand Kim (2009) stated that paperboard coated with PLAcould be used as a substitute for PE-coated paperboard inmanufacturing 1-way paper cups or containers for highmoisture foods (beverage cartons, ice cream containers).

Current applicationsAn overview of current applications is listed in Table 2.

From this table it can be concluded that of the different bio-based materials on the market, PLA is the most commer-cially used one. Furthermore, it can be stated that themain market for bioplastics nowadays are short shelf lifeproducts, like fresh fruits and vegetables and long shelflife products, like potato chips and pasta.

Main characteristics of different bioplasticsAn overview of the main characteristics of various

multilayered biobased films, collected from several com-panies, was made (Table 3). Several physical and mechan-ical properties (e.g. gas and water vapor permeability) andsome other characteristics (e.g. amount biobased) wereexamined or provided by the companies.

This table shows that the investigated materials cover abroad range for the different physical and mechanical char-acteristics that were examined. Considering gas and watervapor permeabilities, it can be stated that the materialsare ranging from low barrier to high barrier films. Consid-ering the tensile properties, elastic and less elastic films andfilms with high and low strength can be found in the table.This means that these films could be used for a wide rangeof packaging applications.

Concerning the other characteristics, not all of them weretested for every film, since several films are still in the testphase. All of the films that were already tested are printable.All the tested films can be used for refrigerated storage,except for Natureflex� N913 and Xylophane A and B andfor frozen storage, except for Xylophane A and B. For appli-cations where pasteurization is needed, none of the testedfilms can be used. Most of the films are already foodapproved (according to regulation 1935/2004). All the filmsare at least 40% biobased and derived from non-food rawmaterials or corn.

Considering the variation in film characteristics dis-played in Table 3, it can be stated that multilayered bio-based films have properties which make them applicablefor use as a packaging material for various types of foods,ranging from short shelf life products, over medium shelflife to long shelf life products.

ConclusionNowadays biobased packaging materials are mostly

used to pack short shelf life products, like fresh fruits andvegetables, and long shelf life products, like pasta andchips, which do not need very high oxygen and/or waterbarrier properties. However, the inventory of films showsa wide variety in properties, which could make them alsoapplicable as a packaging material for other food productswith stricter conditions, like MAP packaging. Storage testsand tests on the industrial packaging machines shouldbe performed to make sure that these films can be usedcommercially. It can be concluded that biobased materialsoffer great potential for the packaging industry. It is how-ever important to realize that a thorough evaluation of thefunctional properties of a biobased material is essentialbefore it can be used as an alternative for traditional filmmaterials.

AcknowledgmentsThis review paper and extended table was obtained in

the framework of a collective research (CO 095062) sup-ported by the Institute for the Promotion of Innovation byScience and Technology in Flanders, Belgium (IWT) andby 22 participating companies in close collaboration with5 research institutes.

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