Biobased barrier coatings for food packaging applications

Green economy, also referred to as biobased economy, utilizes biomass derived raw materials for high-volume applications, such as packaging. Barrier properties are extremely important for biobased food packaging materials as gas, water vapor, grease, aroma and UV-transmission through packaging reduce the quality of food resulting shorter shelf-lives, increased costs and eventually more waste. Biopolymers, such as cellulose, pectin, xylan, starch or chitosan can be used as coating raw materials for paper&board and biobased films and exploited as safe and environmentally sustainable alternatives for synthetic barrier packaging materials. For example, cellulose nanofibrils (CNF) is one of the most promising innovations for forest sector especially due to its excellent barrier properties. Biopolymers can be further reinforced with inorganic nanoplatelets such as montmorillonite based nanoclays. Due to their high aspect ratios of up to 1000, these nanolayered silicates have been widely studied as regards the barrier properties. High-barrier requirements can be reached with additional surface treatment technologies such as sol-gel, ALD or plasma-deposited thin coatings. By plasma deposition the precursors can be chemically grafted on film surface by covalent bonding. Atmospheric plasma activation is also a versatile way to enable the use of sol-gel coatings with polymeric packaging materials. Alternatively, an Al2O3 coating layer grown using the ALD technique could provide an answer to the need for high-quality barrier films. ALD is a surface-controlled, layer-by-layer, thin-film deposition technique based on self-limiting gas-solid reactions. Current trends in the packaging industry are towards lighter weight materials for reduction of raw material use, transportation costs, and minimizing the amount of waste. Interest in sustainable materials combined with barrier improving fillers will continue to growth. As single layer biopolymer films rarely have competitive edge against synthetic films, the combination of individual layers to multilayer structures is necessary. By multilayer structures the barrier properties of biobased materials may be dramatically improved