Natamycin based sol–gel antimicrobial coatings on polylactic acid films for food packaging

In this work a comprehensive study on a new active packaging obtained by a hybrid organic–inorganic coating with antimicrobial properties was carried out. The packaging system based on polylactic acid was realised by sol–gel processing, employing tetraethoxysilane as a precursor of the inorganic phase and polyvinyl alcohol as the organic component, and incorporating natamycin as the active agent. Films with different organic–inorganic ratios (in a range between 1:19 and 1:4) were prepared, and the amount of antimycotic entrapped was found to be modulated by the sol composition, and was between 0.18 and 0.25 mg/dm2. FTIR microspectroscopic measurements were used to characterise the prepared coatings. The antifungal properties of the films were investigated against mould growth on the surface of commercial semi-soft cheese. The release of natamycin from the films to ethanol 50% (v/v) was studied by means of HPLC UV-DAD. The maximal level released was about 0.105 mg/dm2, which is far below the value allowed by legislation.