tharanathan2003.pdf

Biodegradable filmsand compositecoatings: past,

present and future

R.N. TharanathanDepartment of Biochemistry and Nutrition, CentralFood Technological Research Institute, Mysore-570

013, India (tel: +91-821-514876; fax: +91-821-517233; e-mail: [email protected])

Food packaging is concerned with the preservation andprotection of all types of foods and their raw materials,particularly from oxidative and microbial spoilage and alsoto extend their shelf-life characteristics. Increased use ofsynthetic packaging films has led to serious ecological pro-blems due to their total non-biodegradability. Continuousawareness by one and all towards environmental pollutionby the latter and as a result the need for a safe, eco-friendlyatmosphere has led to a paradigm shift on the use of bio-degradable materials, especially from renewable agriculturefeedstock and marine food processing industry wastes.Such an approach amounts to natural resource conserva-tion and recyclability as well as generation of new, innova-tive design and use. Their total biodegradation toenvironmentally friendly benign products such as CO2, waterand quality compost is the turning point which needs to becapitalized and encashed. Polymer cross-linking and graftcopolymerization of natural polymers with synthetic mono-mers are other alternatives of value in biodegradablepackaging films. Although their complete replacement forsynthetic plastics is just impossible to achieve and perhapsmay be even unnecessary, at least for a few specific appli-cations our attention and needful are required in the daysto come. No doubt, eventually BIOPACKAGING will be ourfuture.# 2003 Elsevier Science Ltd. All rights reserved.

IntroductionFood packaging, an important discipline in the area

of food technology, concerns preservation and protec-tion of all types of foods and their raw materials, as wellfrom oxidative and microbial spoilage. Petrochemicalbased plastics such as polyolefins, polyesters, poly-amides, etc. have been increasingly used as packagingmaterials, because of their availability in large quantitiesat low cost and favourable functionality characteristicssuch as good tensile and tear strength, good barrierproperties to O2 and aroma compounds and heat seal-ability. On the contrary they have a very low watervapour transmission rate and most importantly they aretotally non-biodegradable, and therefore lead to envir-onmental pollution, which pose serious ecological pro-blems. Hence, their use in any form or shape has to berestricted and may be even gradually abandoned to cir-cumvent problems concerning waste disposal (Thar-anathan & Saroja, 2001). Of late, there is a paradigmshift imposed by the growing environmental awarenessby all to look for packaging films and processes, whichare biodegradable and therefore compatible with theenvironment. In a sense, biodegradability is not only afunctional requirement but also an important environ-mental attribute. Thus, the concept of biodegradabilityenjoys both user-friendly and eco-friendly attributes,and the raw materials are essentially derived from eitherreplinishable agricultural feedstocks or marine foodprocessing industry wastes, and therefore it capitalizeson natural resource conservation with an underpinningon environmentally friendly and safe atmosphere. Anadditional advantage of biodegradable packagingmaterials is that on biodegradation or disintegration andcomposting they may act as fertilizer and soil condi-tioner, facilitating better yield of the crops. Though a bitexpensive, biopackaging is tomorrow’s need for packa-ging especially for a few value added food products.Food, either in its processed form or in the raw

material stage, depending upon its water activity andtemperature of storage is highly perishable and there-fore needs a careful technological intervention to pre-serve it longer. Quality food preservation is a seriousconcern in the present day food processing operations.The post harvest losses of our farm produce, for exam-ple, the fruits and vegetables are significant, rangingfrom 15 to 20%. These losses are mainly due to

0924-2244/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved.doi:10.1016/S0924-2244(02)00280-7

Trends in Food Science & Technology 14 (2003) 71–78

Review

improper handling and unsound post-harvest technolo-gies being practiced. Transportation from the produc-tion center to far off places for marketing accounts foradditional losses due to spoilage. Availability of farmproduce with freshness, enhanced shelf-life, better fla-vour/aroma and textural characteristics with a highernutritional value is the need of the day.

Packaging filmsThe commonly used packaging films are shown in

Table 1. Although a total replacement of syntheticplastics by the biodegradable materials is just impos-sible, at least for some specific applications such areplacement seems obvious and useful. Towards thisend, there exists a huge business opportunity. Never-theless, such a replacement by biodegradable materialswould also allow us preserve or extend our expensive,dwindling petroleum resources, and helps us save onour foreign exchange. Essential prerequisites of a goodpackaging film (Kader, 1989) are:

1. allow for a slow but controlled respiration
(reduced O2 absorption) of the commodity;
2. allow for a selective barrier to gases (CO2) and
water vapour;
3. creation of a modified atmosphere with respect to
internal gas composition, thus regulating theripening process and leading to shelf-life exten-sion;
4. lessening the migration of lipids—of use in con-
fectionery industry;
5. maintain structural integrity (delay loss of
chlorophyll) and improve mechanical handling;
6. serve as a vehicle to incorporate food additives
(flavour, colours, antioxidants, antimicrobialagents) and
7. prevent (or reduce) microbial spoilage during
extended storage.
Biodegradable composites and packaging filmsAll the above prerequisites can be met with by poly-

mer composites, whose composition and formulationvary from commodity to commodity. Biopolymers fromagricultural feed stocks and other resources have the

ability upon blending and/ or processing to result insuch packaging materials. Their functionality can bebetter expressed by using in combination with otheringredients such as plasticizers and additives. Thepotential uses for such biopolymeric packaging materi-als are:

1. use and throw, disposable packaging materials,
2. routine consumer goods for day-to-day use, such
as plates, cups, containers, egg boxes, etc.,3. disposable personal care napkins/ sanitary pads,

diapers, etc.,4. lamination coating, and
5. bags for agricultural mulching (nersary).
Two types of biomolecules, viz., hydrocolloids andlipids, are generally used in combination for the pre-paration of biodegradable packaging films or compo-sites. Individually they lack structural integrity andcharacteristic functionality. For example, hydrocolloids,being hydrophilic are poor moisture barriers, a propertycompensated by adding lipids, which are very goodmoisture barriers. Composite films are in fact a mixtureof these and other ingredients in varying proportions,which determine their barrier (to H2O, O2, CO2 andaroma compounds) and other mechanical properties.Sometimes a composite film formulation can be tailormade to suit to the needs of a specific commodity orfarm produce. For example, oranges having a thick peelare prone to anaerobic conditions, which lead to anearly senescence and spoilage if the composite film isrich in lipids. Phase separation encountered during thepreparation of composites is overcome by using emulsi-fying agents. Use of plasticizers such as glycerin,enthylene glycol, sorbitol, etc. in the film formula-tions or composites is advantageous to impart plia-bility and flexibility, which improves handling(Garcia, Martino, & Zanitzky, 2000). Use of plastici-zers reduces the brittleness of the film by interferingwith the hydrogen bonding between the lipid andhydrocolloid molecules.The use of wax coating of fruits by dipping is one of

the age-old methods, that was in vogue in the early 12thcentury (Krochta, Baldwin, & Nisperos-Carriedo, 1994).This was practiced in China, essentially to retard water

Table 1. Packaging films commonly used

Film type
Monomeric unit Characteristics
Polyethylene
Ethylene Desirable mechanical properties, heat sealable Polyvinylidene Vinylidene Desirable H2O/O2 barrier, not very strong, heat sealable Polyester Ethyleneglycol+terephthalic acid Desirable mechanical properties, poor H2O/O2 barrier, not heat sealable Polyamide (Nylon) Diamine+various acids Desirable strength, heat sealable, poor H2O/O2 barrier Cellophane Glucose (cellulose) Desirable strength, good H2O/O2 barrier, not heat sealable.
72 R.N. Tharanathan / Trends in Food Science & Technology 14 (2003) 71–78

transpiration losses in lemon and oranges. Later fatcoating of food products, specifically called ‘‘larding’’was in vogue in England. Sausage casing used very com-monly nowadays is nothing but a material derived from aprotein source (gelatin). Usually a film thickness of �2.5mm is employed, and coating is done by several methods.Films are preformed thin membranous structures, whichare used after being formed separately, whereas in coat-ings the thin film is formed directly on the commodity.Dip method coating is the commonly used method for

fruits, vegetables and meat products. In here the com-modity is directly dipped into the composite coatingformulations (in aqueous medium), removed andallowed to air dry, whereby a thin membranous film isformed over the commodity surface. Continuous dip-ping builds up decay organisms, soil and trash in thedipping solution, which needs to be removed for betterperformance characteristics.The coating can also be done by a foam application

method. Emulsions are usually applied by this method.In here extensive tumbling action is necessary to breakthe foam for uniform distribution of the coating solu-tion, over the commodity surface. Coating by sprayingis the conventional method generally used in most of thecases. Due to high pressure (60–80 psi) less coatingsolution is required to give a better coverage. Program-mable spray systems are available for automation dur-ing such operations.Biodegradable packaging films are generally prepared

by wet casting of the aqueous solution on a suitablebase material and later drying. Choice of the basematerial is important to obtain films, which can beeasily removed without any tearing and wrinkling.Infrared drying chambers are advantageous in that theyhasten the drying process (Tharanathan, Srinivasa, &Ramesh, 2002). Optimum moisture content (�5–8%) isdesirable in the dried film for its easy peel off from oneedge of the base material.Biopolymeric films cannot generally be extrusion

blown, like synthetic polymers, as they do not havedefined melting points and undergo decompositionupon heating.Film formation generally involved inter- and intra

molecular associations or cross-linking of polymerchains forming a semi-rigid 3D network that entrapsand immobilizes the solvent. The degree of cohesiondepends on polymer structure, solvent used, tempera-ture and the presence of other molecules such as plasti-cizers. The presence of lipids in the compositeformulations or film provides an appealing glassy finishover the commodity surface.The various naturally occurring biopolymeric materi-

als of use in composite film making and coating for-mulations are shown in Fig. 1. Coating compositesbased on such biomolecules have brought a surge ofnew types of packaging materials into use. These bio-

molecules are compatible amongst themselves and withother hydrocolloids, surfactants and additives, and theiraqueous solutions are usually stable at acidic and neu-tral pH. The composite solutions are preserved forextended/repeated use by adding benzoic acid, sorbicacid or their sodium salts.Polysaccharides are known for their structural com-

plexity and functional diversity (Tharanathan, 2002).Primary structures of some of the polysaccharidehydrocolloids and their derivatives are shown in Fig. 2.Linear structure of some of these polysaccharides, forexample, cellulose (1,4-b-d-glucan), amylose (a compo-nent of starch, 1,4-a-d-glucan), chitosan (1,4-b-d-glu-cosamine polymer), renders their films tough, flexibleand transparent. Their films are resistant to fats andoils. Cross-linking, for example, of chitosan with alde-hydes make the film much more tough, water insoluble(or swellable) and highly resistant.Cellophane, a regenerated cellulose film is made by

the viscose process. Some of the cellulose esters likecellulose acetate propionate and butyrate are thermo-plastic products of commercial importance. The anioniccellulose ether, carboxymethyl cellulose (CMC), beingwater soluble and compatible with other (bio-)mole-cules, has excellent film forming properties (Fig. 3).CMC films are capable of reducing oil pick-up in deep-fat-fried foods. CMC of a degree of substitution 0.7 isusually used in such applications. The barrier andmechanical properties of cellulose-based films aredependent on the molecular weight of cellulose (seeTable 2), higher the molecular weight better is theproperties (Krochta et al., 1994).TAL-Prolong and Semperfresh are two commercially

available composite coating formulations based onCMC (Nisperos-Carriedo, Baldwin, & Shaw, 1992).

Fig. 1. Naturally occurring biopolymers of use in biodegradablepackaging films and composites.

R.N. Tharanathan / Trends in Food Science & Technology 14 (2003) 71–78 73

They contain sucrose fatty acid ester, sodium salt ofCMC and emulsifier. Available in powder or granularform, their aqueous solution (0.5–2% concentration) isused for shelf-life extension of banana and other fruits.Coated banana showed decreased O2 levels and climac-teric rise in ethylene production and delayed chlorophyllloss. Coating of TAL-Prolong (1%) on mangoes showeddelayed ripening with an extended shelf-life. Nature-Sealis another cellulose-based coating formulation used fordelayed ripening of tomatoes and mangoes.Starch is another raw material in abundance, espe-

cially from corn, having thermoplastic properties upondisruption of its molecular structure (Tharanathan,

1995; Tharanathan & Saroja, 2001). Preponderance ofamylose (>70%) in amylomaize starches gives stronger,more flexible films. Branched structure of amylopectingenerally leads to films with poor mechanical properties(decreased tensile strength and elongation). Substitutionof the hydroxyl groups in the molecule weaken thehydrogen bonding ability and thereby improves freeze-thaw stability and solution clarity. Ether linkage tendsto be more stable than the ester linkage. Hydroxypropylstarch composites are used for the preservation of can-dies, raisins, nuts and dates from oxidative rancidity(Arvanitoyannis, Nakayama, & Aiba, 1998). Graftcopolymerization of synthetic monomers such as acrylo-

Fig. 2. Chemical structures of (a) cellulose, (b) amylose, (c) chitosan and (d) pullulan.


nitrile (AN), a precursor of acrylic fibers and plastics,onto starch provides an excellent method for preparingstarch-polymer (S-g-PAN) composites, which are shownto be biodegradable (Saroja, Shamala, & Tharanathan,

2000). A starch graft poly(methylacrylate) copolymerhas been developed for use in agricultural mulching, thatwould degrade during growing season (Dennenberg,Bothast, & Abbott, 1978). Utilization of the starch por-tion by the fungi exposes the plastic polymer for enhancedbiodegradability by microbial and oxidative degradation.Research on biodegradable plastics based on starch

began in the 1970s and continues today at various labsall over the world. Technologies have been developedfor continuous production of extrusion blown films andinjection-molded articles containing 50% or more ofstarch. Water sensitivity of such films has been reducedby lamination with poly(vinyl chloride) (Shogren,Fanta, & Doane, 1993). Combination of urea with cer-tain polyols provides better plasticization of starch withgood quality films (Doane, 1992). Melted or destruc-turized starch, obtained by disruption of the granulararchitecture resulting in loss of crystallinity, hasemerged as a new type of thermoplastic material forcommercial development. To increase the compatibility

Fig. 3. Carboxymethylcellulose, DS=10.

Table 2. Properties of cellulose-based packaging films

Mol. wt. (Da)
O2ml.m/m2 s.Pa
Watervapourng. m/m2 s.Pa

Tensilestrength(MPa)

Elongation(%)

Methylcellulose
13,000 3.1 0.084 55.62 11.16 20,000 3.6 0.094 56.15 18.51 41,000 4.6 0.103 61.15 20.71
Hydroxypropyl cellulose
100,000 3.0 0.052 14.79 32.76 370,000 3.2 0.059 15.32 203.53 LDPE 11.32 0.006 13.1–27.6 100–965
Fig. 4. Structures of (a) high-methoxyl and (b) low methoxyl pectin.


of hydrophilic starch with the hydrophobic plasticmatrix, starch granules have been surface treated, forexample with silanes (Doane, 1992). Pro-oxidants cansometimes be added to enhance oxidative degradationof the synthetic polymer.Pectin, is a complex anionic polysaccharide composed

of b-1,4-linked d-galacturonic acid residues, wherein theuronic acid carboxyls are either fully (HMP, highmethoxy pectin) or partially (LMP, low methoxy pectin)methyl esterified (Fig. 4). HMP forms excellent films.Plasticized blends of citrus pectin and high amylosestarch give strong, flexible films, which are thermallystable up to 180�C. Pectin is also miscible with poly(vinylalcohol) in all proportions. Potential commercial usesfor such films are water soluble pouches for detergentsand insecticides, flushable liners and bags, and medicaldelivery systems and devices. These films are solutioncasted by air-drying at ambient temperature. Starch-based plastic foams formed by blending starch withpolylactic acid are used as loose-fill cushioning materialsto protect against shock and vibration during transpor-tation (Fang & Hanna, 2000). Laminated films frompectin and chitosan together with either glycerol or lac-tic acid as a plasticizer have been prepared (Fishman,Friedman, and Huang, 1994).Starch derived products such as dextrins or glucose

are extensively used as a component of the fermentationmedium. Glucose can be fermented to lactic acid, whichcan be polymerized to polylactic acid polymers andcopolymers. Their use as biodegradable plastics is ofconsiderable interest and demand (Narayan, 1993).Conversion of lactic acid to its dehydrated dimer, thelactide followed by ring opening polymerization to highmolecular weight polymers or further copolymerizationwith caprolactone gives packaging films of high value.Bacterial fermentation of glucose, acetic acid and feedstocks gives novel thermoplastic polyesters such as poly-3-hydroxybutyrate (PHB) (Savenkova et al., 2000).These polymers (Fig. 5) either alone or in combination

with synthetic plastics or starch (Ke & Sun, 2000) pro-duce excellent packaging films.PHB is a thermoplastic biopolyester accumulated as a

reserve of carbon and energy by a number of bacteria(Lee, 1996). Its exceptional stereo-chemical regularityleads to progressive crystallization with aging, thusmaking it brittle. This has been overcome by incor-poration of comonomers by grafting. For example,copolymers of PHB with 3-hydroxyvalerate are pro-duced by using specific additives in the growth medium(Byrom, 1992). Such an approach, though improves theproperties of PHB, is not cost effective, because thecopolymer costs are higher, and its toxicity leads tolower production yields and also its presence affectsPHB crystallization kinetics, which results in longerprocessing cycle times. Nevertheless, PHB could betoughened by the process of annealing by conditioningin an oven, a process that widens its application possi-bilities (De Koning & Lemstra, 1993). To overcome theescalating cost economics, genetically engineered plantsharboring the bacterial PHA biosynthesis genes arebeing developed (Lee, 1996), which hopefully may turn-out PHAs competitive with the conventional plastics.The polymorphic Aureobasidium pullulans secretes a

polysaccharide pullulans, which is commercially a usefulhydrocolloid of value (Seviour, Stasinopoulos, Auer, &Gibbs, 1992). It can be extruded as films, which arebiodegradable, it is resistant to oils and grease, hasexcellent O2 permeability rates and is nontoxic. It is ana-glucan consisting of repeating maltotriose residuesjoined by 1,6-linkages (Fig. 2). Pullulan is of use in bio-degradable packaging film industry.Free standing films have been prepared from chitosan

and its derivatives, and their mechanical, barrier andbiodegradation characteristics studied (Kittur, Kumar,& Tharanathan, 1998). Cross-linked chitosan films offergreater strength and resistance for handling. By beingantifungal and antimicrobial, chitosan-based films andcoating formulations have additional value addition(Tharanathan & Kittur, in press). Chitosan-based com-posite coating formulations (Kittur, Saroja, Habi-bunnisa, & Tharanathan, 2001) as well as films(Srinivasa et al., 2002) have been shown to prolong theshelf-life of banana, mango and capsicum. Applicationof chitosan induces the production of plant defenceenzymes such as chitinase. A composite formulationcalled Nutri-Save, based on derivatized chitosan, isextensively used for shelf-life extension of apples, pears,pomegranates, etc.Proteinaceous hydrocolloids of plant and animal ori-

gin are used in some specific coating formulations. Theyprovide a good barrier to O2 and CO2, but not to water.Nevertheless, such films supplement the nutritionalvalue of coated food. Zein, the corn protein fraction,upon casting from aqueous aliphatic alcoholic solutionsform tough, glossy and grease-resistant films. By adding
Fig. 5. General structure of polyhydroxyalkanoates.

glycerine or by cross-linking the tensile strength of thefilms is further improved. Edible films have been pro-duced by heating sunflower proteins to 85�C and solu-tion casting (Meixueir, van Garcia, & Silvestre, 2000).Film formation in such proteins is through inter-molecular disulphide bridges and hydrogen bonds accom-panied by surface dehydration. Whey proteins (20% oftotal milk proteins) when appropriately processed produceflexible but brittle films (Kaya & Kaya, 2000).Collagen films have traditionally been used for pre-

paring edible sausage casing (Hood, 1987). Collagen is amajor constituent of skin, tendon and connective tissuesand it is the most prevalent and widely distributedfibrous protein in the animals. Gelatin, resulting frompartial hydrolysis of collagen, produces flexible toughfilms when cast together with glycerine or sorbitol. Pro-teinaceous films may sometimes lead to potential aller-genic reactions in some individuals because of proteinmodification, deficiency in essential amino acids, etc.Wax coatings are naturally found on fruit and vege-

table surfaces, where they help prevent moisture loss,especially in the dry humid season. Preservation of freshand dry fruits and nuts by was coatings have beenpracticed since time immemorial. Bees wax, paraffinwax, candelilla wax (an oily exudate of the candelillaplant grown in USA/Mexico), etc. are some of the waxpreparations used in such applications. They are alsoused as micro-encapsulation agents, especially for spiceflavouring substances.Shellac, composed of complex mixtures of aliphatic,

alicyclic hydroxy acid polymers, is a secretion of theinsect Laecifer lacca. It is used as confectioners glaze on

candies. Free fatty acids have also been used in somecomposites. By a careful selection of the fatty acid type(its chain length and type of derivatization) and itsconcentration, composite formulations with variableperformance characteristics can be tailor made for spe-cific applications. Formulations prepared by compositemixture of hydrocolloid, emulsifiers and lipid moleculeshave shown considerable promise for shelf-life extensionof several agri-horticultural produce (Krochta et al.,1994).Polyethylene terephthalate (PET), a polyester has

recently been introduced as a biodegradable packagingmaterial (The Science, 1997). This material can be recy-cled, incinerated or land-filled, but it is mainly intendedfor disposal by composting, where it undergoes soildegradation to CO2 and water. Upon complete disin-tegration (�8 weeks), it enriches soil as shown by posi-tive indications of plant germination and seedlingemergence, earthworm weight gain and mortality, andmicrobial population density. By soil-enrichment meth-ods, microbes have been isolated that degrade majorpetrochemical based compounds such as phthalic acid,isophthalic acid, terephthalic acid and their esters,which find extensive use in the manufacture of syntheticplastic films.Addition of natural polymers like starch into poly-

ethylene is another approach to make them biodegrad-able. Starch-LDPE films (containing up to 30% starch)have been shown to be biodegradable upon composting.The most attractive feature of the biopolymer-based

packaging films/composites is their total biodegrad-ability. As a result they fit perfectly well in the ecosys-

Fig. 6. The carbon cycle of biodegradable polymers.


tem, and save our world from growing ecological pol-lution caused by non-biodegradable plastics, which areessentially petroleum-based. A number of aerobic andanaerobic microorganisms have been identified for bio-degradation. The carbon cycle involving the biopolymerdegradation is shown in Fig. 6.

Future strategySynthetic polymers are gradually being replaced by

biodegradable materials especially those derived fromreplenishable, natural resources. More than the origin,the chemical structure of the biopolymer that deter-mines its biodegradability. Use of such biopackagingswill open up potential economic benefits to farmers andagricultural processors. Bilayer and multicomponentfilms resembling synthetic packaging materials withexcellent barrier and mechanical properties need to bedeveloped. Cross-linking, either chemically or enzyma-tically, of the various biomolecules is yet anotherapproach of value in composite biodegradable films.Innovative techniques of preserving food safety andstructural-nutritional integrity as well as completebiodegradability must be adopted. Eventually bio-packaging constitutes a niche market and that will beour future. Sustained multidisciplinary research effortsby chemists, polymer technologists, microbiologists,chemical engineers, environmental scientists andbureaucrats are needed for a successful implementationand commercialization of biopolymer-based eco-friendly packaging materials. Undoubtedly, biode-gradation offers an attractive route to environmentalwaste management.

AcknowledgementsThe author thanks Mr. A.B. Vishu Kumar for excel-

lent assistance in type setting the manuscript.

References

The Science (1997). Editorial article, 1–2 OctoberArvanitoyannis, I., Nakayama, A., & Aiba, S. (1998). Edible films

made from hydroxypropyl starch and gelatin and plasticized bypolyols and water. Carbohydrate Polymers, 36, 105–119.

Byrom, D. (1992). Production of poly-b-hydroxybutyrate-poly–b-hydroxy valerate copolymers. FEMS Microbiological Reviews,103, 247–250.

De Koning, G. T. M., & Lemstra, P. J. (1993). Crystallization phe-nomena in bacterial poly[(R)-3-huydroxybutyrate]: 2. Embrittle-ment and rejuvenation. Polymer, 34, 4089–4094.

Dennenberg, R. J., Bothast, R. J., & Abbot, T. P. (1978). A new bio-degradable plastic made from starch graft poly(methylacrylate)copolymer. Journal of Applied Polymer Science, 22, 459–465.

Doane, W. M. (1992). USDA research on starch-based biodegrad-able plastics. Staerke, 44, 293–295.

Fang, Q., & Hanna, M. A. (2000). Functional properties of polylacticacid-starch-based loose fill packaging films. Cereal Chemistry, 77,779–783.

Fishman, M.L., Friedman, R.B., & Huang, S.J. (Eds.) (1994). Polymersfrom agricultural coproducts. ACS Symposium series 575.Washington, DC: American Chemical Society

Garcia, M. A., Martino, M. N., & Zanitzky, N. E. (2000). Micro-structural characterization of plasticized starch-based films.Staerke, 52, 118–124.

Hood, L. L. (1987). Collagen in sausage casings. Advances in MeatResearch, 4, 109–129.

Kader, A. A. (1989). Modified atmosphere packaging of fruits andvegetables. Critical Reviews in Food Science and Nutrition, 28, 1–30.

Kaya, S., & Kaya, A. (2000). Microwave drying effects on propertiesof whey protein isolate edible films. Journal of Food Engineering,43, 91–96.

Ke, T., & Sun, X. (2000). Physical properties of poly-(lactic acid) andstarch composites with various blending ratios. Cereal Chem-istry, 77, 761–768.

Kittur, F. S., Kumar, K. R., & Tharanathan, R. N. (1998). Functionalpackaging properties of chitosan films. Zeitschrift Fur Lebensmit-tel Unterschung and Forsuchung, A, 206, 44–47.

Kittur, F. S., Saroja, N. S., Habibunnisa, & Tharanathan, R. N. (2001).Polysaccharide based composite coating formulations for shelf-life extension of fresh banana and mango. European FoodResearch and Technology, 213, 306–311.

Krochta, J.M., Baldwin, E.A., & Nisperos-Carriedo, M.O. (Eds.) (1994).Edible coatings and films to improve food quality. Basel: Tech-nomic Publishing Company, Inc

Lee, S. Y. (1996). Bacterial polyhydroxyalkanoates. Biotechnologyand Bioengineering, 49, 1–14.

Meixueir, F. A., vanGarcia, C., & Silvestre, F. (2000). Biodegradablefilms from isolate of sunflower (Helianthus annus) proteins. Jour-nal of Agricultural and Food Chemistry, 48, 3032–3036.

Narayan, R. (1993). Biodegradable plastics in opportunities for inno-vation: Biotechnology. National Institute of Standards and Tech-nology Monograph, NIST-GCR-93-633, 135

Nisperes-Carriedo, M. O., Baldwin, E. A., & Shaw, P. E. (1992).Development of edible coating for extending post-harvest life ofselected fruits and vegetables. Proceedings of Florida State Hor-ticultural Science, 104, 122–125.

Saroja, N., Shamala, T. R., & Tharanathan, R. N. (2000). Biode-gradation of starch-g-polyacrylonitrile, a packaging material byBacillus cereus. Process Biochemistry, 36, 119–125.

Savenkova, L., Gercberga, Z., Nikolaeva, V., Dzene, A., Bibers, I., &Kalmin, M. (2000). Mechanical properties and biodegradationcharacteristics of poly-(hydroxy butyrate)-based films. ProcessBiochemistry, 35, 573–579.

Seviour, R. J., Stasinopoulos, S. J., Auer, D. P. F., & Gibbs, P. A.(1992). Production of pullulan and other exopolysaccharides byfilamentous fungi. Critical Reviews in Biotechnology, 12, 279–298.

Shogren, R. L., Fanta, G. F., & Doane, W. M. (1993). Development ofstarch based plastics—a reexamination of selected polymersystems in historical perspective. Staerke, 45, 276–280.

Srinivasa, P.C., Revathy, B., Ramesh, M.N., Harish Prashanth, K.V.,& Tharanathan, R.N. (2002). Storage studies of mango packedusing biodegradable chitosan films. Storage Technology, 215,504–508.

Tharanathan, R. N. (1995). Starch—the polysaccharide of highabundance and usefulness. Journal of Scientific and IndustrialResearch, 54, 452–458.

Tharanathan, R. N. (2002). Food derived carbohydrates—structuralcomplexity and functional diversity. Critical Reviews in Bio-technology, 22, 65–84.

Tharanathan, R.N. & Kittur, F.S. (in press). Chitin—the undisputedbiomolecule of great potential. Critical Reviews in Food Scienceand Nutrition

Tharanathan, R. N., & Saroja, N. (2001). Hydrocolloid-based packa-ging films—alternate to synthetic plastics. Journal of Scientificand Industrial Research, 60, 547–559.

Tharanathan, R. N., Srinivasa, P. C., & Ramesh, M. N. (2002). Aprocess for production of biodegradable films from poly-saccharides. Indian patent 0085/DEL/02.


Documents

tharanathan2003.pdf