Recent outbreaks of food-borne pathogens over the past years in Europe and the United States have demonstrated the devastating epidemiological and economical outcomes of these events. Thus, over the past decade there is an immense effort to develop antimicrobial packaging systems. The increasing consumer health concern and growing demand for healthy foods have stimulated the use of natural biopreservatives, such as essential oils (EOs), defined as GRAS (generally recognized as safe) antimicrobial agents. The highly volatile nature of EOs, which is advantageous for their efficient diffusion and mode of action, presents a major obstacle for their incorporation with synthetic polymers via conventional high-temperature melt compounding and processing.
Two types of inorganic carriers i.e., layered nanoclays and Halloysite nanotubes (HNTs), are modified with a model EO, carvacrol (CV, originating from Oregano and Thyme). Thermal gravimetric analysis shows that the thermal stability of CV within these hybrids is significantly enhanced, allowing for melt compounding of CV at elevated temperatures, suitable for polymer processing. The inorganic carriers-CV hybrids are melt-compounded with common polyolefins (at temperatures of 140-250°C), including low-density polyethylene (LDPE) and polypropylene (PP), followed by subsequent cast or blown extrusion for film production. The resulting films exhibit highly potent and long-lasting (up to two years) antimicrobial activity against a variety of food-borne bacteria species and fungi, while the corresponding polymer/CV films (no carrier) demonstrate activity for up to several weeks. This is the first work to report on polymer/EOs systems with a wide and prolonged antimicrobial activity.
