Nanocomposites of kaolin modified with oregano essential oil for application in antibacterial packaging

Active packaging aims to extend the shelf life of products and is normally obtained via direct incorporation of additives into the polymer matrices. However, this incorporation may cause some losses by volatilization during processing and rapid release during application. This study consisted of modifying clay minerals (halloysite (Hal) and kaolinite (Kaol)) with oregano essential oil (OEO) and incorporating them into a polymer matrix of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV). The modification method used – sonication followed by vacuum application – did not change the morphologies of the clay minerals and resulted in similar OEO incorporation efficiencies (43% and 45% for Kaol and Hal, respectively, using a 1:10 clay:oil ratio). However, Hal:10-OEO sample provided a slow OEO evaporation in temperatures suitable for microbial growth and was chosen for the preparation of PHBV nanocomposites. The PHBV/Hal:10-OEO/OEO composition presented the lowest oxygen permeability. The use of Hal:10-OEO modified clay also enabled a controlled release of OEO, resulting in an antimicrobial activity against E. coli close to the satisfactory value of 2 log units' reduction and 30% of antioxidant activity after 48 h of OEO release in food simulant medium, being promising for application in active packaging.