Verena Jost, Department of Materials Development, Fraunhofer Institute, Process Engineering & Packaging (Germany) considered the special needs of sustainable packaging for food: an application where the protection and safety of the product are paramount. Any change which has even a minor negative effect on the usable life of the food will cancel out a large benefit in sustainability of the pack.
Coating PP and PET films with a biopolymer barrier has given insufficient adhesion unless corona treatment can be used. Even then the biofilm tends to be more brittle and easily cracked than the traditional coat. So additives have to be added to the biopolymer to increase flexibility; Glycerol, Sorbitol, PEG 200 and Propylene glycol have been found effective. Cast films of whey protein, corn starch and dextrin plus 25-40% of these plasticisers have higher water vapour and oxygen permeability, lower tensile strength and higher elongation than the controls. Uses of the plasticised biopolymers as coatings to improve the barrier properties of food wrapping paper are being developed.
(from a paper given at the Biopolymer World Conference, Venice, April 2012)