Biopolimeros

Biopolymer Coatings on Paper Packaging Materials
Khaoula Khwaldia, Elmira Arab-Tehrany, and Stephane Desobry

ABSTRACT: Increased environmental concerns over the use of certain synthetic packaging and coatings in combination with consumer demands for both higher quality and longer shelf life have led to increased interest in alternative packaging materials research. Naturally renewablebiopolymers can be used as barrier coatings on paper packaging materials. These biopolymer coatings may retard unwanted moisture transfer in food products, are good oxygen and oil barriers, are biodegradable, and have potential to replace current synthetic paper and paperboard coatings. Incorporation of antimicrobial agents in coatings to produce active paper packaging materials provides an attractiveoption for protecting food from microorganism development and spread. The barrier, mechanical, and other properties of biopolymer-coated paper are reviewed. Existing and potential applications for bioactive coatings on paper packaging materials are discussed with examples.

Introduction
Paper is widely used in packaging applications and is biodegradable and therefore perfectly safe for theenvironment. Paper consists of a porous cellulose structure made up of microfibrils, which are composed of long-chain cellulose molecules in a crystalline state with amorphous regions regularly disrupting the crystalline structure. The hydrophilic nature of cellulose, due to the OH sites in the basic unit of cellulose (C 6 H 10 O 5 ) and fiber network porosity, limits the water-vapor-barrier properties ofpaper. Paper packaging also easily absorbs water from the environment or from the food and looses its physical and mechanical strengths. Moisture migration can occur in paper by diffusion of water vapor through the void spaces as well as in condensed form through the fiber cell walls (Bandyopadthay and others 2002). Paper is often associated with other materials, such as plastic materials andaluminum, for their good barrier properties that could be advantageously combined with paper stiffness. Paper is coated with ethyl vinyl alcohol (EVOH), a polymer with excellent oxygen-barrier properties, when gas barrier properties are requested (Zhang and others 1999, 2001). However, because of the polar groups of EVOH at the origin of the hydrophilic character of the polymer at high relativehumidity, an additional polymer layer based on polyolefins is used to prevent water sorption (Despond and others 2005). Polyolefins are generally chosen as paper coating materials to overcome porosity and hygroscopicity of
MS 20090740 Submitted 8/1/2009, Accepted 9/10/2009 . Author Khwaldia is with Inst. Natl. de Recherche et d’Analyse Physico-chimique, INRAP, Pole ˆ Technologique de Sidi Thabet 2020Sidi Thabet, Tunisia. Authors Arab-Tehrany and Desobry are with Laboratoire d’Ingenierie des Biomolecules, ENSAIA, 2 ´ ´ av. de la foret de Haye-BP 172 54505, Vandoeuvre-les-Nancy cedex, France. ˆ ` Direct inquiries to author Khwaldia (E-mail: khaoula_khwaldia@yahoo.fr).

paper. Unfortunately, the obtained material loses its biodegradation and recyclability characteristics due to the addition ofsynthetic polymer layers. Natural polymers can be used as barrier coatings on paper packaging materials. Such biodegradable coatings have the potential to replace current synthetic paper coatings, such as polyethylene, polyvinyl alcohol, rubber latex, and fluorocarbon in food packaging applications (Chan and Krochta 2001a, 2001b). Agriculturally derived alternatives to synthetic paper coatingsprovide an opportunity to strengthen the agricultural economy and reduce importation of petroleum and its derivatives. Naturally renewable biopolymers have been the focus of much research in recent years because of interest in their potential use as edible and biodegradable films and coatings for food packaging. The properties, technology, functionalities, and potential uses of biopolymer films and...