Innovative bio-based food packaging
The BIOPACK project focused on developing new types of proactive bio-based packaging material for grated, sliced and whole cheeses. These novel materials were based on polyactides (PLA) and chitosan and were further modified using plasma coating or nanoclay incorporation. Chitosan is a bioactive natural polymer aimed for modification of PLA packaging materials as it features a very high gas barrier and antimicrobial properties. A wide range of chitosan forms were evaluated including initial chitosan, microcystalline chitosan (MCCh), chitosan salts and modified chitosan salts. Selected chitosan forms were employed for coating of PLA film surface resulting in a one-sided coating, double-sided coating, and a third application with chitosan in-between a two-layered PLA film. Despite poor adhesion of chitosan to the PLA film surface and coating heterogeneity, the latest modified microcrystalline chitosan-PLA coating was significantly improved in terms of moisture sensitivity. All forms displayed a satisfactory oxygen permeability rate, an excellent antimicrobial activity and biological activity within the investigated incubation times and temperatures. Particularly, chitosan salts and modified chitosan salts demonstrated high bacteriostatic and bactericidal activity against E. coli. Additionally, a chitosan salt (lactate) is biodegradable and further investigations are required for other modified chitosan forms. Chitosan was also successfully used for compounding with PLA granulate, yet only chitosan preparates with a good thermo-stability could be applied for preparation of PLA/chitosan composites with suitable properties. Very good thermo-stability was found for initial chitosan, while several chitosan forms displayed a satisfactory thermo-stability. Further research on the compounding process is still needed as the chitosan compounded PLA films didn't meet the key requirements of cheese packaging due to insufficient mechanical and barrier properties. Apart from cheese packaging PLA/chitosan materials could also find useful applications in products demanding medium and high oxygen barriers and where the water vapour transmission rate is not critical. The technology has an increased potential for other applications, such as other food packaging including meat and dairy products, fruit, vegetables and dry powdery products. Producers of food packaging materials and microbiology experts are sought for further collaborations.
