Characterization of SPI-based edible films incorporated with cinnamon or ginger essential oils

Film-forming emulsions were formulated by combining soy protein isolate (SPI) with two essential oils (cinnamon, C and ginger, G), and films were obtained by casting. Regardless of the oil type and amount, a narrow distribution of small particles was obtained. The oil type significantly affected the film’s mechanical properties. Films with ginger oil were less resistant and less stretchable than those with cinnamon oil (p < 0.01). The water vapour permeability of SPI films was not reduced for the range of oil content studied. Cinnamon oil affected the optical properties more markedly than ginger oil. The topography of the surfaces revealed some aggregation of ginger oil during the drying step. The differences between the lipid–protein interactions developed for each essential oil determined the observed behaviour.