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applications, including replacing synthetic polymer coat-

ings on paper or on other synthetic plastics (18, 19).

Besides being derived from renewable resources, they

are biodegradable; and when used as coatings for paper

or plastic, they have potential for being more easily

separated to make the paper or plastic more easily

recyclable.

Plasticizers

Like synthetic polymer ﬁlms, edible ﬁlms often require

incorporation of low-molecular-weight plasticizers to im-

prove ﬁlm ﬂexibility and durability. Plasticizers generally

interrupt polymer chain-to-chain interactions and lower

the glass-transition temperature (T

), resulting in greater

ﬂexibility but also, unfortunately, increased ﬁlm perme-

ability. Plasticizing materials acceptable for edible ﬁlms

include sucrose, glycerol, sorbitol, propylene glycol, poly-

ethylene glycol, fatty acids, and monoglycerides. Depend-

ing on the composition, size, and shape of plasticizer

selected for a certain polysaccharide or protein ﬁlm-for-

mer, the effect on barrier properties relative to the im-

provement of mechanical properties can be minimized (20,

21). Water is also a plasticizer for polysaccharide and

protein edible ﬁlms. Thus, ﬁlm moisture content as af-

fected by content of other plasticizers and the surrounding

relative humidity can have a dramatic effect on edible-ﬁlm

properties.

Other Additives

Edible ﬁlms can be considered active packaging, because

their edibility provides a function beyond passive barrier.

Edible ﬁlms show promise for being additionally active

through incorporation of antioxidants (22), antimicrobials

(23–27), nutrients, nutraceuticals, ﬂavors and colors to

enhance food safety, nutrition, and quality (28–30). For

some food-coating applications, addition of surfactant to a

ﬁlm formulation may be necessary to ensure good surface

wetting, spreading, and adhesion (31).

FILM MANUFACTURE

Methods for forming ﬁlms include a wet (solvent) casting

method and a dry (extrusion) method (32). Besides solvent

casting, lipid ﬁlms and coatings can also be formed from a

melt.

Solvent Casting

This approach to forming edible ﬁlms from aqueous,

aqueous–ethanol, or ethanol solutions or dispersions is

similar to production of certain synthetic ﬁlms (e.g., poly-

vinyl chloride) by solvent casting. The solution or disper-

sion is spread on a smooth surface. After the solvent

evaporates, a ﬁlm can be stripped from the surface. With

the exception of collagen, corn zein, and wheat gluten,

most of the polysaccharide and protein ﬁlm-forming ma-

terials are soluble in water. This can be an advantage in

terms of ﬁlm manufacture and use, but makes ﬁlms whose

properties are especially vulnerable to moisture. Corn zein

and wheat gluten ﬁlms must be formed from aqueous–

ethanol solution or from an aqueous dispersion, but

provide a somewhat improved moisture barrier compared

to other protein-based ﬁlms formed from aqueous solution.

Wax ﬁlms, layers, or coatings can be formed from ethanol

solution. Edible-ﬁlm production that requires ethanol

necessitates appropriate safety measures and solvent

recovery for commercialization. Water-insoluble whey

protein ﬁlms result from heat-treated aqueous whey pro-

tein solutions due to denaturation and subsequent inter-

molecular crosslinking of individual whey protein

molecules (33).

Edible ﬁlms from methyl cellulose (MC) and hydroxy-

propylmethyl cellulose (HPMC) are manufactured com-

mercially by solvent casting on a continuous belt, with

subsequent drying, removal, and winding of the resulting

ﬁlm. Such ﬁlms can be formed into edible, water-soluble

pouches for food ingredients. Gelatin capsules cast from

aqueous solution ﬁnd broad use in the pharmaceutical

industry. Hard capsule halves are formed on steel pins by

dipping into gelatin solution, followed by drying and

removal from the pins (34). After a drug is ﬁlled into a

hard capsule half, two interlocking halves are joined to

form the full capsule. Soft capsules containing a drug or

vitamin are formed from two previously formed sheets of

plasticized gelatin by injection of the drug at the moment

when the two sheets are brought together between the

rotating halves of roller dies (35).

Polysaccharide–lipid bilayer ﬁlms with excellent moist-

ure-barrier properties have been produced from aqueous–

ethanol solutions of cellulose derivatives with lipids (36,

37). As the solvent evaporates, phase separation results in

bilayer formation. Lipid layers or coatings can be formed

directly from ethanol solution or aqueous emulsion. Stable

emulsions of lipids in proteins or polysaccharides produce

well-dispersed composite ﬁlms with improved moisture

barrier compared to protein or polysaccharide ﬁlms alone,

but inferior moisture barrier compared to bilayer ﬁlms.

Research efforts continue to develop composite edible

ﬁlms with good moisture-barrier properties (17, 18).

Extrusion

Water-insoluble, edible collagen ﬁlm sausage casings and

meat wraps are made by regenerating collagen that is

extracted from animal hides. Collagen casings and wraps

are produced by extruding a viscous, aqueous suspension

of puriﬁed acidiﬁed collagen into a neutralizing coagula-

tion bath, followed by washing, plasticizing, and drying

(38). Some polysaccharides and proteins display thermo-

plastic behavior, and this property is being explored for

edible-ﬁlm production by thermoplastic extrusion (39).

Successful, efﬁcient production of edible ﬁlms using con-

ventional extrusion equipment would improve commercia-

lization opportunities.

Molten Casting

Lipid ﬁlms, layers, and coatings can be produced by cool-

ing of a melt to produce a solid structure. Challenges

include the high temperatures required for some melts,

ﬁlm thickness control, adhesion, and brittleness of some

458 FILM, EDIBLE

materials. Forming a lipid layer from a melt on a precast

polysaccharide or protein ﬁlm is an alternative approach

for manufacturing an edible composite ﬁlm with good

moisture-barrier properties.

FOOD AND DRUG COATING

Formation of edible ﬁlms as coatings on foods and drugs

generally consists of solvent casting directly on the food or

drug surface. Application of ﬁlm-forming solution, suspen-

sion, or emulsion can be by dipping, spraying, dripping, or

enrobing.

Fruits and Vegetables

Edible coatings on whole and minimally processed fruits

and vegetables generally serve to reduce moisture loss,

improve appearance, and, in some cases, control oxygen

and carbon dioxide exchange and/or carry an antimicro-

bial (40–42). Materials commonly used include beeswax,

carnauba wax, candelilla wax, shellac, and mineral oil.

These materials cannot form stand-alone ﬁlms, but form

continuous coatings on the fruit or vegetable surface. Film

coatings based on polymeric materials such as cellulose

derivatives, chitosan, and proteins have been developed to

reduce oxygen and carbon dioxide exchange for respira-

tion and ripening-rate reduction. Coating solution or

emulsion is most typically sprayed or dripped onto the

fruit or vegetable and/or onto a bed of brushes rotating

either below or above the produce, followed by drying.

Thorough distribution of the coating over the entire fruit

or vegetable is dependent on a clean, dry produce surface

and suitable surface tension and viscosity of the coating

formulation.

Confections, Nuts, and Drug Tablets

Edible coatings on confections, nuts, and tablets serve to

resist moisture change, reduce oxygen uptake, improve

structural integrity, and make the product more palatable

by adding gloss and/or ﬂavor or, in the case of drugs, by

masking ﬂavor and improving ingestibility (43, 44). Ma-

terials commonly used include shellac, corn zein, cellulose

derivatives, waxes, and acetylated monoglycerides. The

most common method of coating involves controlled spray-

ing (or ladeling) and drying of coating formulations on the

product surface in a rotating, horizontal drum-like cham-

ber called a ‘‘pan.’’ Formation of a uniform coating depends

on good product coverage, thorough product tumbling

action to help distribute the coating formulation, and

rapid drying to allow gradual buildup of the coating.

Coatings can also be formed on product surfaces in a

ﬂuidized-bed system. Coating formulations are sprayed

into a ﬂuidized-bed of the product, where tumbling action

spreads the coating formulation and the ﬂuidizing air

dries the coating. This method is commonly used in the

pharmaceutical industry, but has potential for use in

coating foods such as nuts that have consistent size and

shape (45). Successful pan-coating and ﬂuidized-bed-coat-

ing depend on suitable coating-formulation surface ten-

sion and viscosity.

Other Foods

Many other foods have been considered for coating to

improve quality and safety. Coatings have been developed

for meat, poultry, and seafood to prevent moisture loss and

oxidation and to improve color, ﬂavor, and microbial

stability (43, 46, 47). Such coatings can be applied by

dipping, spraying, foaming or brushing. Coatings and

batter-and-breading ingredients have been studied and

commercialized for reducing fat uptake in fried foods (48,

49). Application is normally by dipping, brushing, spray-

ing or enrobing. Requirements of edible ﬁlms and coatings

are especially stringent for military and outer-space food

applications (50). Edible coatings have also been devel-

oped for use in low-energy osmotic dehydration of foods, to

reduce solute uptake without slowing water removal (51).

FILM PHYSICAL PROPERTIES

Standard methods for testing packaging materials are

used to detemine properties of edible ﬁlms. Depending

on which food or drug application is considered, different

barrier, mechanical, surface, and optical properties are of

most interest. Tables 1–3 compare the permeability and

mechanical properties of edible ﬁlms made from represen-

tative materials presently used or proposed for use. It is

essential to understand that plasticizer content and test

conditions (temperature and relative humidity) have im-

portant effects on ﬁlm properties. Increasing relative

humidity increases the moisture content of polysacchar-

ide- and protein-based ﬁlms, resulting in increased perme-

ability and decreased strength. Thus, comparison of

edible-ﬁlm properties must be approached with caution.

Because of their polar hydrophilic nature, polysacchar-

ides and proteins form ﬁlms that are poor moisture

barriers compared to the low-density polyethylene

(LDPE) packaging ﬁlm commonly used to protect foods

and drugs from moisture (Table 1). However, when poly-

saccharides or proteins are combined with edible waxes or

fatty acids in composite ﬁlms where the polysaccharide or

protein provides ﬁlm structural integrity, ﬁlms with mod-

erate-to-good moisture-barrier properties result. HPMC-

and MC-based composite ﬁlms have been developed which

are bilayer in nature, with resulting excellent moisture

barrier properties. This occurs because the water-vapor

permeabilities of waxes and fatty acids rival that of LDPE.

In the case of wax coatings on fruit and vegetable surfaces,

it is not necessary to use the ﬁlm-forming and lipid-

supporting nature of an edible polymer.

The polar nature of polysaccharides and proteins re-

sults in ﬁlms that are good oxygen barriers at low-to-

intermediate relative humidity (rh) (Table 2). Polysacchar-

ide and protein ﬁlms are better oxygen barriers at 50% rh

than is LDPE ﬁlm, which is a poor oxygen barrier. Protein

edible ﬁlms appear to be better oxygen barriers than

polysaccharide, resin, or lipid ﬁlms, with permeabilities

approaching

that of the

excellent oxygen barrier provided

by ethylene–vinyl alcohol copolymer (EVOH) at low-to-

intermediate rh (see Ethylene–vinyl alcohol copolymer).

In addition, the molecular composition and literature data

FILM, EDIBLE 459

for polysaccharide and protein edible ﬁlms suggest that

they are good lipid and aroma barriers.

Edible ﬁlms appear to have tensile strength (TS) and

elongation (E) values roughly between those of LDPE and

polystyrene (Table 3). Plasticizer level has a dramatic

effect on properties, with tensile strength decreasing and

elongation increasing with increased plasticizer content.

Edible ﬁlm toughness values (approximately TS E) are

far below that of LDPE ﬁlm commonly used to make bags

and pouches. However, they are sufﬁcient to allow many

applications. Small pouches are being produced success-

fully from HPMC for food ingredients, and casings and

Table 2. Oxygen Permeabilities of Selected Edible Films Compared to Synthetic Polymer Films

Film Test Conditions Permeability [(cm

mm)/(m

day kPa)] Reference

HPMC 241C, 50% rh 272 (61)

MC 241C, 50% rh 97 (61)

Collagen RT, 63% rh 23.3 (62)

WPI:Gly (2.3:1) 231C, 50% rh 76.1 (63)

WPI:Sor (2.3:1) 231C, 50% rh 4.3 (63)

Shellac 291C, 55% rh 212 (58)

BW 251C, 0% rh 931 (59)

LDPE 231C, 50% rh 1870 (64)

EVOH (70% VOH) 231C, 0% rh 0.1 (64)

EVOH (70% VOH) 231C, 95% rh 12 (64)

HPMC = hydroxypropylmethyl cellulose, MC = methyl cellulose, WPI = whey protein isolate, Gly = glycerol, Sor = sorbitol, BW = beeswax, LDPE = low-density

polyethylene, EVOH = ethylen e–vinyl alcohol copolymer, VOH = vinyl alcohol.

Table 1. Water-Vapor Permeabilities of Selected Edible Films Compared to Low-Density Polyethylene Film

Film Test Conditions

Permeability [(g mm)/(m

day kPa)] Reference

HPMC:PEG (9:1) 251C, 85/0% rh 6.5 (36)

SA:PA:HPMC:PEG 251C, 85/0% rh 0.048 (36)

BW/SA:PA:MC:HPMC:PEG 251C, 97/0% rh 0.058 (37)

HPMC 271C, 0/85% rh 9.1 (52)

HPMC:SA (1.25:1) 271C, 0/85% rh 0.026 (52)

Amylose 251C, 100/0% rh 31.6 (53)

Zein:Gly (4.9:1) 211C, 85/0% rh 9.6 (54)

Gluten:Gly (3.1:1) 211C, 85/0% rh 53 (54)

WPI:Gly (4:1) 251C, 0/77% rh

70 (55)

WPI:BW:Sor (3.5:1.8:1) 251C, 0/98% rh

5.3 (56)

Na caseinate 251C, 0/81% rh

37 (57)

Ca caseinate:BW (1.7:1) 251C, 0/97% rh

3.6 (57)

Shellac 301C, 0/84% rh 0.72 (58)

BW 251C, 0/100% rh 0.021 (59)

LDPE 381C, 90/0% rh 0.079 (60)

Relative humidities are those on top and bottom sides of ﬁlm (top/bottom).

Corrected rh shown; HPMC = hydroxypropylmethyl cellulose, MC = methyl cellulose, SA = stearic acid, PA = palmitic acid, BW = beeswax, PEG = polyethylene

glycol, WPI = whey protein isolate, Gly = glycerol, Sor = sorbitol, LDPE = low-density po lyethylene.

Table 3. Mechanical Properties of Selected Edible Films Compared to Synthetic Polymer Films

Film Tensile Strength (MPa) Elongation (%) References

HPMC 69 10 (61)

MC 62 10 (62)

Starch 49 7 (53)

Amylose 70 23 (53)

Collagen:Cell:Gly (3.4:0.8:1) 3–11 25–50 (65)

Zein:PEG + Gly (2.6–5.9:1) 3–28 6–213 (66)

Gluten:Gly (2.5:1) 3 276 (67)

WPI:Gly (2.3:1) 14 31 (63)

LDPE 9–17 500 (68)

Polystyrene 35–55 1 (69, 70)

HPMC = hydroxypropylmethyl cellulose, MC = methyl cellulose, cell = cellulose, Gly = glycerol, PEG = polyethylene glycol, WPI = whey protein isolate,

LDPE = low-density polyethylene.

460 FILM, EDIBLE

wraps are being produced from collagen. Other edible ﬁlm

materials are also being explored for these uses. Edible

ﬁlms formed as coatings on food or drug products do not

require the mechanical properties of stand alone ﬁlms

used as wraps, pouches, or casings.

MATERIAL AND APPLICATION TRENDS

Much research in recent years has been devoted to

quantiﬁcation of the barrier and mechanical properties

of edible ﬁlms produced from both old and new materials.

Although most effort has been devoted to moisture and

oxygen permeabilities and tensile properties, increased

attention has been given to aroma-barrier (71), surface

(72), optical (72, 73), and sensory (74) properties and

consumer attitudes (75). Availability of such data should

lead to more rational selection of edible-ﬁlm and coating

systems for food and drug design. Besides the various

waxes, acetylated monoglycerides, shellac, zein, collagen,

gelatin, MC, and HPMC in current use in food and drug

products, wheat gluten, soy protein, casein, whey protein,

triglycerides, fatty acids, alginate, carrageenan, aloe vera,

and chitosan are among materials that have received

increased attention as potentially useful materials in

edible ﬁlms. New coating materials being developed in-

clude water-based proteins and polysaccharides to replace

ethanol-based shellac and corn zein in some applications

(76). Of particular interest have been multicomponent

ﬁlm-forming formulations that combine the advantages

of the individual components. For example, multicompo-

nent composites have potential for combining the ﬁlm-

forming and oxygen-barrier properties of a polysaccharide

or protein with the moisture-barrier properties of a lipid.

Considerable research is also being devoted to improv-

ing the efﬁciencies of forming edible ﬁlms as coatings on

foods and to quantiﬁcation of the effects of coatings on food

moisture gain or loss, food oxidation, fruit and vegetable

respiration, and product gloss. Advantages can be derived

from ability to extrude edible ﬁlms as an alternative to

solvent casting for some applications. In addition to the

current uses mentioned earlier, edible ﬁlm coatings have

been studied or proposed for applications ranging from (a)

prevention of moisture loss, browning, and microbial

growth with fresh-cut fruits and vegetables to (b) preven-

tion of moisture migration and oxidation in frozen foods.

Interest in increased food quality and shelf life has

resulted in research on incorporation of antioxidants in

edible ﬁlms to complement their oxygen-barrier proper-

ties. Increased concern with food safety has resulted in

research on the ability of edible ﬁlms to provide antimi-

crobial compounds to the surfaces of foods. Incorporation

of antimicrobials in edible ﬁlms and coatings prevents

their rapid diffusion into the food interior, maintaining a

minimum inhibitory concentration at the food surface for

longer periods of time. Table 4 shows representative

antimicrobial-incorporated edible ﬁlms that have shown

ability to inhibit bacterial growth.

CONCLUSIONS

Edible ﬁlms comprised of proteins, polysaccharides, lipids,

and/or resins and other edible components have much

potential for complementing conventional packaging for

improvement of food and drug quality and safety. Utiliza-

tion of an edible ﬁlm, formed into a pouch or formed as a

coating, can reduce the amount and improve the recycl-

ability of the conventional packaging. Investigation of new

materials, development of new ﬁlm-forming and coating

methods, and determination of ﬁlm and coating properties

have increased the possibilities for commercial applica-

tions. Addition of antioxidants and antimicrobials to ed-

ible ﬁlms and coatings can enhance their protective

function. Interest in increased food quality and safety

and decreased and more sustainable packaging, along

with improved edible-ﬁlm properties and economics, will

result in increased use of edible ﬁlms in the future.

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Table 4. Bacterial Inhibition Effects of Selected Antimicrobial-Incorporated Edible Films

Film Base

Material

Antimicrobial Agent Target Microorganisms References

HPMC Nisin Micrococcus luteus, Listeria innocua,

Listeria monocytogenes,

Staphylococus aureus

(77, 78)

Chitosan Chitosan L. innocua, L. monocytogenes (79)

SPI Lauric acid, nisin L. monocytogenes (80)

SPI Citric acid, lactic acid, malic acid,

Tartaric acid, nisin

L. monocytogenes, E. coli O157:H7,

Salmonella gaminara

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SPI, CZ Lysozyme, nisin, EDTA L. plantarum, E. coli (82)

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WPI Lactoperoxidase system, Lysozyme L. monocytogenes (86, 87)

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HPMC = hydroxypropylmethyl cellulose, SPI = soy protein isolate, CZ = corn zein, WPI = whey protein isolate.

FILM, EDIBLE 461

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51. M. Mya Kin, W. Zhou and C. Perera, Int. J. Food Eng. 1(1), 1–

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52. R. D. Hagenmaier and P. E. Shaw, J. Agric. Food Chem. 38(9),

1799–1803 (1990).

462 FILM, EDIBLE

53. I. A. Wolff, H. A. Davis, J. E. Cluskey, L. J. Gundrum, and C.

E. Rist, I&EC 43(4), 915–919 (1951).

54. H. J. Park and M. S. Chinnan, J. Food Eng. 25, 497–507

(1995).

55. T. H. McHugh, J. F. Aujard, and J. M. Krochta, J. Food Sci.

59(2), 416–419, 423 (1994).

56. T. H. McHugh and J. M. Krochta, J. Food Process. Preserv. 18,

173–188 (1994).

57. R. J. Avena-Bustillos and J. M. Krochta, J. Food Sci. 58(4),

904–907 (1993).

58. R. D. Hagenmaier and P. E. Shaw, J. Agric. Food Chem. 39(5),

825–829 (1991).

59. I. K. Greener, Physical Properties of Edible Films and Their

Components, Ph.D. thesis, University of Wisconsin, Madison,

WI, 1992.

60. S. A. Smith, ‘‘Polyethylene, Low Density’’ in M. Bakker, ed.,

The Wiley Encyclopedia of Packaging Technology, Wiley, New

York, 1986.

61. Anonymous, A Food Technologist’s Guide to Methocel Pre-

mium Food Gums, The Dow Chemical Co., Midland, MI, 1990.

62. E. R. Lieberman and S. G. Gilbert, J. Polym. Sci. Symp. No.

41, 33–43 (1973).

63. T. H. McHugh and J. M. Krochta, J. Agric. Food Chem. 42(4),

841–845 (1994).

64. M. Salame, in M. Bakker, ed., The Wiley Encyclopedia of

Packaging Technology, Wiley, New York, 1986.

65. L. L. Hood, in A. M. Pearson, T. R. Dutson, and A. J. Bailey,

eds., Advances in Meat Research, Van Nostrand Reinhold,

New York, 1987.

66. B. L. Butler and P. J. Vergano, ASAE Paper No. 946551,

ASAE, St. Joseph, MI, 1994.

67. A. Gennadios, C. L. Weller, and R. F. Testin, ASAE Paper No.

90-6504, ASAE, St. Joseph, MI, 1990.

68. J. H. Briston, in M. Bakker, ed., The Wiley Encyclopedia of

Packaging Technology, Wiley, New York, 1986.

69. J. S. Houston, in M. Bakker, ed., The Wiley Encyclopedia of

Packaging Technology, Wiley, New York, 1986.

70. J. F. Hanlon, Handbook of Package Engineering, Technomic

Publishing, Lancaster, PA, 1992.

71. K. S. Miller and J. M. Krochta, Trends Food Sci. & Technol. 8,

228–237 (1997).

72. S.-I. Hong, J. H. Han, and J. M. Krochta, J. Appl. Polymer Sci.

92, 335–343 (2004).

73. K. L. Dangaran and J. M. Krochta, Int. J. Food Sci. Technol.

42, 1094–1100 (2007).

74. Y. Zhao and M. McDaniel, in J. H. Han, ed., Innovations in

Food Packaging,

Elsevier Academic

Press, New York, 2005,

pp. 434–454.

75. V. C. H. Wan, C. M. Lee and S.-Y. Lee, J. Sensory Studies

22(3), 353–366 (2007).

76. K. L. Dangaran and J. M. Krochta, The Manufacturing

Confectioner 83(1), 61–65 (2003).

77. V. Coma, I. Sebti, P. Pardon, A. Deschamps, and H. Pichavant,

J. Food Prot. 64, 470–475 (2001).

78. I. Sebti, F. Ham-Pichavant, and V. Coma, J. Agric. Food

Chem. 50, 4290–4294 (2002).

79. V. Coma, A. Martial-Gros, S. Garreau, A. Copinet, F. Salin,

and A. Deschamps, J. Food Sci. 67, 1162–1169 (2002).

80. P. L. Dawson, G. D. Carl, J. C. Acton, and I. Y. Han, Poultry

Sci. 81, 721–726 (2002).

81. S. Eswaranandam, N. S. Hettiarachchy, and M. G. Johnson, J.

Food Sci. 69, FMS79–FMS84 (2004).

82. T. Padgett, I. Y. Han, and P. L. Dawson, J. Food Prot. 61,

1330–1335 (1998).

83. A. Cagri, Z. Ustunol, and E. T. Ryser, J. Food Sci. 66, 865–870

(2001).

84. A. Cagri, Z. Ustunol, and E. T. Ryser, J. Food Sci. 67, 2317–

2324 (2002).

85. A. Cagri, Z. Ustunol, W. Osburn, and E. T. Ryser, J. Food Sci.

68, 291–299 (2003).

86. S. Min, L. J. Harris, and J. M. Krochta, J. Food Sci. 70, M317–

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87. S. Min, L. J. Harris, J. H. Han, and J. M. Krochta, J. Food

Prot. 68, 2317–2325 (2005).

88. S. Min, L. J. Harris, and J. M. Krochta, J. Food Sci. 70, M332–

M338 (2005).

89. S. Min, L. J. Harris and J. M. Krochta, J. Food Prot. 69, 784–

793 (2006).

Further Reading

R. Ahvenainen, P. Myllarinen, and K. Poutanen, European Food

& Drink Review, Summer, 73, 75, 77–80 (1997).

M. Anker, Edible and Biodegradable Films and Coatings for Food

Packaging—A Literature Review, SIK, Gotegorg, Sweden, 1996.

I. Arvanitoyannis and L. G. M. Gorris, in F. A. R. Oliveira, J. C.

Oliveira, M. E. Hendrickx, D. Knorr, and L. G. M. Gorris, eds.,

Processing Foods—Quality Optimization and Process Assess-

ment,

CRC Press, Boca Raton, FL, 1999, pp. 357–370.

E. A. Baldwin,

in M. S. Rahman, ed., Handbook of Food Preserva-

tion, Marcel Dekker, New York, 1999, pp. 577–609.

S. Chapman and L. Potter, Edible Films and Coatings: A Review,

Campden & Chorleywood Food Research Association Group,

Chipping Campden, UK, 2004.

F. Debeaufort, J.-A. Quezada-Gallo and A. Voilley, Crit. Rev. Food

Sci. Nutr. 38(4), 299–313 (1998).

N. Gontard and S. Guilbert, in M. Mathlouthi, ed., Food Packa-

ging and Preservation, Blackie Academic & Professional,

London, 1994, pp. 159–181.

S. Guilbert, in M. Mathlouthi, ed., Food Packaging and Preserva-

tion, Elsevier Applied Science Publishers, New York, 1986, pp.

371–394.

S. Guilbert and N. Gontard, in P. Ackermann, M. Ja

gerstad, and

T. Ohlsson, eds., Foods and Packaging Materials—Chemical

Interactions, The Royal Society of Chemistry, Cambridge,

England, 1995, pp. 159–168.

S. Guilbert, B. Cuq and N. Gontard, Food Add. Contam. 14(6–7),

741–751 (1997).

S. Guilbert and N. Gontard, in J. H. Han, ed., Innovations in Food

Packaging, Elsevier Academic Press, New York, 2005, pp. 263–

276.

J. H. Han and A. Gennadios, in J. H. Han, ed., Innovations in Food

Packaging, Elsevier Academic Press, New York, 2005, pp. 239–

262.

J. J. Kester and O. R. Fennema, J. Food Sci. 40(12), 47–59

(1986).

J. M. Krochta, E. A. Baldwin, and M. Nisperos-Carriedo, eds.,

Edible Coatings and Films to Improve Food Quality, Tech-

nomic Publishing, Lancaster, PA, 1994.

J. M. Krochta, in S. Damodaran and A. Paaraf, eds., Food Proteins

and their Applications in Foods, Marcel Dekker, New York,

1997, pp. 529–549.

FILM, EDIBLE 463

J. M. Krochta and C. L. C. De Mulder-Johnston, Food Technol.,

51(2), 61–74 (1997).

M. O. Martin-Polo, in G. V. Barbosa-Canovas and J. Welti-Chanes,

eds., Food Preservation by Moisture Control, Technomic Pub-

lishing, Lancaster, PA, 1995.

A. Nussinovitch, Leatherhead Food RA Food Industry Journal,

1(3), 174–188 (1998).

A. Nussinovitch, Water Soluble Polymer Applications in Foods,

Blackwell Science, Oxford, UK, 1995.

C. Quinn, Food Manufacture, Aug. 28, 42 (2007).

FILM, FLEXIBLE PVC

ANIL G. DOSHI

Bordon, Inc., Resinite Division,

North Andover, Massachusetts

Flexible poly(vinyl chloride) (PVC) ﬁlm is well established

as a versatile, cost-effective packaging material. The

ability of PVC to accept and respond to a range of additives

makes it a unique and popular packaging material. A

variety of production processes are used to manufacture

PVC ﬁlm for a variety of applications. Film can be

produced by blown or cast extrusion, calendaring, or

solution casting in thicknesses ranging from 0.0004 in.

to W0.004 in. It can be produced as a highly ﬂexible,

permeable stretch ﬁlm or an oriented shrink ﬁlm.

PVC resins, the principal component of PVC ﬁlms, are

made by polymerizing vinyl chloride monomer using

suspension, emulsion, or bulk polymerization. PVC resin

is a free-ﬂowing white powder. Of the approximately 11

billion pounds of PVC resin produced in the United States

in 1994, about half a billion pounds went into packaging

applications (1). Flexible PVC packaging ﬁlm applications

are estimated to have consumed about 200 10

lb of PVC

resin.

COMPOSITION

The ingredients used in manufacturing of ﬂexible PVC ﬁlms

depend on the intended applications. The selection of the

proper additive type and level are key parameters that

inﬂuence the characteristics of the PVC packaging ﬁlm.

Food packaging, the single largest application for ﬂexible

PVC ﬁlms, requires the use of ingredients sanctioned by the

Food & Drug Administration (FDA). Non-food-packaging

applications offer a broader range of additive selection.

RESIN

Suspension polymerized PVC resin, having a K value of

about 66–68, is typically used to produce ﬂexible PVC

packaging ﬁlms. The resin is usually classiﬁed as ﬁlm-

grade, indicating good absorptivity, a very low level of gels

and contamination, and very good heat stability.

PLASTICIZER

Plasticizers are the major additives, and their prime pur-

pose is to impart ﬂexibility (2). Essentially, all PVC packa-

ging ﬁlms contain one or more plasticizers. Food-packaging

applications require the use of only FDA-sanctioned plas-

ticizer. Because of the balance of plasticizing efﬁciency, cost,

and availability, adipate plasticizers are most commonly

used. For non-food-packaging applications, the plasticizer

choice is vast, but the majority that are used are nontoxic

and often FDA-sanctioned. Phthalate and adipate esters

are dominant in such applications. Most ﬂexible PVC ﬁlm

formulations also use an oil epoxide, typically epoxidized

soybean oil. This additive, frequently called a secondary

plasticizer, imparts ﬂexibility as well as considerable heat

stability during processing.

HEAT STABILIZERS

The main function of a heat stabilizer is to prevent

discoloration during processing (3). Heat-stabilizer selec-

tion for ﬂexible PVC ﬁlm is a complex matter, dictated by

the application, manufacturing process and interaction

with other additives. For food-contact applications, stea-

rates of calcium, magnesium, and zinc are most often

used. They are relatively inefﬁcient and are often boosted

by oil epoxies and phosphites. For nonfood applications,

organometallic salts of barium and zinc are popular and

offer excellent heat stability.

LUBRICANTS

Lubricants are added to PVC compounds to facilitate

processing and control processing rate (4). The effective-

ness of lubricants depends on their marginal or complete

insolubility in PVC compounds. External lubricants reduce

sticking of the melt to hot-metal surfaces; montan ester

waxes, parafﬁns, and low-molecular-weight polyethylenes

are commonly used. Internal lubricants affect the frictional

properties of the resin particle surface during processing

and thus control the fusion rate of the resin. Fatty acids,

esters, and metallic soaps are frequently used.

OTHER COMPONENTS

Most other components of a ﬂexible PVC ﬁlm are added to

impart a speciﬁc physical property. Esters of multifunc-

tional alcohols, with the proper hydrophobic–hydrophilic

balance, are added at low levels to impart antifog and

antistatic properties. Inorganic additives such as clay or

talc, as well as organic additives such as amides, can be

added for slip and antiblock properties. Pigments may be

added for tinting and coloring.

METHODS OF MANUFACTURE

Essentially all ﬂexible PVC packaging ﬁlms are produced

from externally plasticized resin containing other addi-

tives; this is extruded through a ﬁlm-forming die. Two;

basic methods are used: blown-ﬁlm extrusion and slot-die-

464 FILM, FLEXIBLE PVC

cast extrusion. The blown ﬁlm process dominates PVC

packaging ﬁlm production.

PVC resin is blended with selected additives using a high-

intensity mixer . Mixing time varies with the actual formula-

tion used as well as the equipment. Mixing is complete when

the compound (blend of resin and additives) is once again dry

and free-ﬂowing and the additives are completely dispersed.

The compound is typically heated, through shear energy, to

230–2601F and then discharged to a ribbon blender to be

further mixed and cooled to the desired temperature. This

compound is often referred to as dry blend.

Dry blend may be pelletized for later use or fed directly

to a blown-ﬁlm extruder. Equipment needs to be expressly

designed for the heat-sensitive PVC compound, requiring

streamlined ﬂow with no ‘‘dead spots.’’ The ﬁlm is wound

using surface or center winders and sold in roll form, in a

variety of widths. Flexible PVC ﬁlm can also be preferen-

tially or biaxially oriented to provide shrink characteris-

tics. This is usually accomplished by using a two-roll

orienting unit or bubble inﬂation under controlled tem-

peratures and strain rates. Tentering equipment can also

be used, usually with slot-die-cast extrusion equipment.

MARKETS

Food Packaging

Most ﬂexible PVC ﬁlm is used for packaging food products,

particularly fresh red meat. Properly formulated ﬂexible

PVC stretch ﬁlms features high oxygen permeability,

toughness, resilience, and clarity, making it ideal for in-

store wrapping of fresh meat. Packaging of fresh fruits

and vegetables in ﬂexible PVC ﬁlm is primarily performed

in-store. Films are formulated for high gas transmission

rates and provide excellent shelf life to the respiring

produce, including sensitive mushrooms.

Packaging of chilled, tray-packed poultry parts is often

done with ﬂexible PVC ﬁlm. The toughness and resilience

of PVC ﬁlm, plus its good heat sealability in a wet

environment, make it a material of choice in this centra-

lized packaging application.

The ability to be readily printed with solvent- and

water-based inks, without the need for any special surface

treatment, have ﬁgured prominently in both meat and

poultry packaging, for brand identiﬁcation and merchan-

dising. A recent development has been the imprinting of a

safe handling label, mandated by USDA, on the ﬁlm itself.

This ensures 100% compliance at the store level on all

packages of raw meat.

Institutional packaging is the second-largest food-wrap

application for ﬂexible PVC ﬁlm. These ﬁlms, in a thick-

ness range of 0.4–0.6 mil (10–15 mm), are wound on rolls

and placed in dispenser boxes with a cutter blade. They

are used in institutional kitchens, cafeterias, restaurants,

and caterers to overwrap food trays, salads, glassware,

and utensils. The ﬁlms feature excellent cling, clarity,

stretch, and dispensability.

Properly formulated ﬂexible PVC ﬁlms are also used for

frozen-food storage, as well as in boxed beef operations

and in-store bakeries and delicatessens.

Table 1. Typical Properties of 1-mil (25.4 lm) Flexible PVC Film

Property

ASTM Test

Method

Flexible PVC

Meat Package

Stretch Film

Flexible PVC

Dispenser Film

Flexible PVC

Shrink Bundle

Film

Speciﬁc gravity D1505 1.23 1.27 1.3

Yield, in.

/(lb mil) [m

/(kg mm)] 22,400 [1254] 21,600 [1210] 21,400 [1198]

Haze, % D1003 1.2 1.0 2.5

Tensile strength, psi (MPa) D882 MD

5000 (34.5) 5500 (37.9) 15,000 (103)

4500 (31) 5500 (37.9) 5500 (37.9)

Elongation, % D882 MD 275 300 90

TD 375 325 275

Tear strength, gf/mil (N/mm) D1922 MD 300 (116) 325 (125) 335 (129)

TD 450 (175) 500 (193) 575 (222)

Change in linear dimensions at 2121F

(1001C) for 30 min, %

D1204

MD NA

NA 45

TD 10

Service temperature 20–150 0–150 10–150

1F(1C), range (29–66) (18–66) (12–66)

Heat-seal temperature 290–320 290–340 280–330

1F(1C), range (143–160) (143–171) (138–166)

Oxygen permeability, (cm

mil)/

(100 in.

day atm) [(cm

 mm)/

day kPa)] 731F (231C), 50% rh

D1434 860 [3342] 340 [1321] NA

Water-vapor transmission rate,

(g mil)/100 in.

day) [(g mm)/

day)], 1001F (381C), 90% rh

16 [6.3] 10 [3.9] NA

MD, machine direction.

TD, transverse direction.

NA, not available.

FILM, FLEXIBLE PVC 465

Nonfood Packaging

Oriented PVC ﬁlms are widely used to overwrap boxed

goods such as games and toys. One of the newer applica-

tions for oriented, ﬂexible PVC is in the bundling of

multiple aseptic packs. Ranging in thickness from 0.6 to

1.2 mils (15 to 30 mm), such ﬁlms provide high shrink at

low temperatures, resulting in a ﬁrm unitized pack, with-

out any distortions, offering merchandising appeal.

Heavy-gauge ﬂexible PVC, 2–6 mils (51–152 mm), has

been used as a component of windowed cards for many

years. Toughness, formability, good dielectric sealability,

and merchandisability are properties that lend them-

selves to the packaging of hardware, ﬂashlights, and

automobile parts.

Table 1 lists typical physical properties of the main

types of ﬂexible PVC packaging ﬁlms.

BIBLIOGRAPHY

1. Modern Plast. 00, 64 (1994).

2. J. K. Sears and J. R. Darby, The Technology of Plasticizers,

John Wiley & Sons, New York 1982, pp. 35, 305.

3. H. A. Sarvetnick, Polyvinyl Chloride, Van Nostrand Reinhold,

New York, 1969, p. 88.

4. Ibid., p. 1214.

FILM, FLUOROPOLYMER

A. B. ROBERTSON

Allied Fibers and Plastics

Updated by Staff

INTRODUCTION

Fluoropolymers are a family of materials that have a

general parafﬁnic structure with some or all of the

hydrogen atoms replaced by ﬂuorine. All members of

the ﬂuoropolymer family are available in ﬁlm form, but

only Aclar ﬁlm is used extensively in specialty packaging

applications. Honeywell is a supplier of Aclar ﬁlm. Some

of its useful properties are extremely low transmission of

moisture vapor and relatively low transmission of other

gases, inertness to most chemicals, outstanding resis-

tance to forces that cause weathering (UV radiation and

ozone), transparency, and useful mechanical properties

from cryogenic temperatures to temperatures as high as

3001F (1501C). The initial interest in Aclar ﬁlm was for

packaging military hardware, but its water-vapor-trans-

mission properties led to interest by pharmaceutical

companies for packaging moisture sensitive products

(see Pharmaceutical Packaging). Available in several

grades, Aclar is more expensive than most thermoplastic

ﬁlms.

COMPOSITION AND EXTRUSION

Aclar is a trade name (Honeywell) for ﬁlm made from

Aclon, a modiﬁed PCTFE (polychlorotriﬂuoroethylene)

ﬂuoropolymer that contains greater than 95 wt% chloro-

triﬂuoroethylene (1). It is converted to ﬁlm by melt extru-

sion (see Extrusion). It is a difﬁcult thermoplastic to

extrude because it has a very high melt viscosity and a

low, critical, shear rate for melt fracture. The commer-

cially available ﬁlms have different machine-direction and

cross-direction properties because some orientation is

induced during fabrication. Aclar 22 ﬁlms have good tear

strength and can be used unsupported as well as in

thermoformable laminates (see Laminating; Thermoform-

ing). Aclar 33, made from a different copolymer, offers

superior dimensional stability and resistance to chemicals

and water vapor transmission.

FABRICATION

Aclar ﬁlm can be heat-sealed (see Sealing, Heat), lami-

nated, printed, thermoformed, metallized (see Metalliz-

ing), and sterilized (see Healthcare Packaging). The

unsupported and laminated varieties can be handled

and processed on most common converting and packaging

machines. Unsupported and laminated ﬁlms can be heat-

sealed by machines that employ constant heat, thermal

impulse, radiofrequency, or ultrasonic energy. In some

cases, special precautions must be observed.

Most Aclar ﬁlm for packaging is converted to some type

of laminate. It can be laminated to paper, polyethylene

(low and medium density), and to preprimed PVC, alumi-

num foil, polyester, nylon 6, and cellophane. A typical

extrusion lamination (see Extrusion Coating; Multilayer

Flexible Packaging) uses molten LDPE as an adhesive

between the ﬂuoropolymer ﬁlm and one of the substrates

listed above. An MDPE tie layer produces a laminate with

better properties at elevated temperatures. Laminates can

also be produced by adhesive lamination. In that case the

Aclar ﬁlm should be preprimed. Preprimed ﬁlm can be

bonded to polymeric substrates with two-component ur-

ethane adhesives. The adhesive system is applied in water

or organic solvent, and the liquid is evaporated in an oven.

Because of its low surface energy, Aclar ﬁlm does not have

acceptable bond strength to most substrates unless the

ﬁlm is corona-treated (see Surface Modiﬁcation) to in-

crease its surface energy. With corona treatment, the

ﬁlm can be laminated to aluminum and steel foils by

using an epoxy-polyamide curing adhesive.

All grades and gauges can be thermoformed. Typical

thermoforming temperatures are 350–4001F (175–2051C).

It is done close to, but not above, the melting point of the

ﬁlm. One of the important uses of Aclar ﬁlm is the use of

thermoformed laminated Aclar 22A/PVC in blister packs

for ethical drugs. Heavier gauges (5–10 mil or 127–254 mm)

of unsupported Aclar ﬁlm can be thermoformed using

ceramic or quartz heating units. Thermoformed ﬁlm and

laminates should be quick-quenched to maintain low

crystallinity and prevent brittleness.

466 FILM, FLUOROPOLYMER

Table 1. Approximate Comparative Transmission

Rates

Films

Moisture

Vapor, g

mil/(100 in.

d)

[g mm/(m

d)]

mil/(100 in.

d atm)

[cm

mm/(m

d kPa)]

Aclar 33C

0.025 [0.01]

7 [27.2]

16 [62.2]

Aclar 22C

0.045 [0.018]

15 [58.3]

2.5 [9.7]

40 [155]

Aclar 22A

0.041 [0.016]

12 [46.6]

2.5 [9.7]

30 [117]

PVDC

0.20 [0.78]

0.8–1.0 [3.1–3.9]

0.12–0.16 [0.47–0.62] 3.0–4.6 [11.7–17.9]

Polyethylene

Low-density

1.0–1.5 [0.4–0.6]

300–700 [1166–2720] 130–260 [505–1010]

1400–2800 [5440–10,879]

Medium-density

0.4–1.0 [0.16–0.4]

170–500 [661–1943] 100–120 [389–466]

500–1500 [1943–5828]

High-density

0.3–0.7 [0.12–0.28]

34–250 [132–971]

40–55 [155–214]

250–720 [971–2798]

Nylon-6

19–20 [7.5–7.9]

2.6 [10.1]

0.9 [3.5]

9.7 [37.7]

Fluorinated ethylene polypropylene (FEP)

0.4–0.5 [0.16–0.20]

750–1000 [2914–3886] 300–400 [1166–15

54] 1600–2000 [6217–7771]

Poly(vinyl ﬂuoride) (PVF)

2.0–3.2 [0.79–1.3]

3.0–3.3 [11.7–12.8]

0.25–0.70 [1.0–2.7] 11–15 [42.7–58.3]

Polyester

1.0–3.0 [0.4–1.2]

4.0–8.0 [15.5–31]

0.7–1.0 [2.7–3.9]

12–25 [46.6–97.1]

ASTME 96 at 100

1F (381

C) and 90% rh.

Dry gas at room temperature.

467