Biodegradable films based on poly(lactic acid) coatings and natural olive-wastewater extracts for active food packaging

The goal of this work was to develop innovative, 100% biodegradable films with antioxidant effectiveness, based on poly(lactic acid) (PLA) and a natural olive wastewater extract (OWE). Active PLA coatings were realized by spreading a PLA/OWE coating solution, with an OWE amount up to 20 wt%, on a Poly(lactic acid)/Poly(butylene adipate-co-terephthalate) substrate. The study of active films antioxidant activity and release kinetics in foods with high lipid content was accomplished using 95% ethanol as food simulant. Preliminary shelf-life tests on a sensitive greasy food matrix (i.e. avocado fruits) were also carried out, in order to qualitatively examine the films potential in limiting fruit oxidative/browning phenomena. Finally, the effect of the OWE on the films color and photo-oxidative stability under natural light exposure was also examined. The results pointed out the influence of the morphology and distribution of the active agent on the coatings release rate, and the antioxidant activity and equilibrium time increased by increasing the antioxidant concentration. The shelf-life tests highlighted the promising perspectives for the films in retarding the oxidation/browning reactions of short shelf-life foods, and pave the way to more in-depth investigations on the most appropriate strategies to prevent the transfer of the OWE brown color while keeping intact the benefits of the antioxidant packaging.