A glass vial containing sandalwood oil, an essential oil.Image credit: Itineranttrader, Wikimedia CommonsEssential oils are aromatic oily liquids extracted from different parts of plants (roots, peels, leaves, seeds, fruits, barks) and have been shown to be a good source of antioxidative and antimicrobial properties.  Essential oils act as antioxidants in several different ways, such as free radical scavengers, termination of peroxides, prevent lipid oxidation (spoiling), and more. 

Essential oil incorporation into packaging may improve water vapor barrier properties of protein-based films, increase the strength of the film and resistance to stretching, decrease transparency, and help prevent food spoilage by interacting with the films other properties. 

Read the abstract in the Journal of Food Science here.