Characterization of L-Polylactide and L-Polylactide-Polycaprolactone Co-Polymer Films for Use in Cheese-Packaging Applications

摘要

Impact-modified and unmodified L-polylactide and L-polylactide-polycaprolactone co-polymer films were evaluated for their suitability as materials for cheese packaging. The polymers were in some cases compounded with nanoclays as a possible route to enhanced barrier properties and/or with cyclodextrin complexes designed to provide slow release of encapsulated antimicrobials for control of mould growth on packaged cheeses. The materials demonstrated complete biodegradation under controlled composting conditions and the extruded films had acceptable transparency. Moisture uptake by films and a decrease in polymer molecular weight with time of exposure to high humidity were identified as areas of concern, although the polymer stability experiments were undertaken at 25℃ and stability at normal cheese storage temperatures (～4℃) is expected to be better. Nanoclay addition enhanced the thermal stability of the polymer but reduction of oxygen and water vapour permeability to target levels through incorporation of 5% w/w nanoclay was not achieved, possibly in part due to inadequate dispersion of the nanoclays in the chosen polymer matrices. On the positive side, a novel impact-modified polylactide was developed that overcame problems with brittleness in unmodified L-polylactide and L-polylactide-polycaprolactone co-polymer films, and tests indicated that a cyclodextrin-encapsulated antimicrobial (allyl isothiocyanate) incorporated in L-polylactide-polycaprolactone co-polymer films would be effective in controlling fungi on packaged cheeses. Migration of substances from the L-polylactide or L-polylactide-polycaprolactone films into cheese is not expected to be a problem.