Physicochemical properties of alginate/polycaprolactone-based films containing essential oils

Oregano, savory, and cinnamon essential oils (EOs) 1% (w/v) were separately incorporated as natural antioxidant agents in alginate/polycaprolactone-based films. Films were then treated in 2 or 20% (w/v) CaCl2 solutions in order to generate insoluble films. The mechanical properties and the insoluble matter of films were determined. Intermolecular interactions between film components and alginate cross-linkage were characterized by Fourier transform infrared (FTIR) spectroscopy. Surface morphology of the polymer membrane was determined by scanning electron microscopy (SEM) analysis. Antiradical properties of films were also evaluated following a modified colorimetric method using the N,N-diethyl-p-phenylenediamine (DPPD) discoloration test. Results showed that films treatment with CaCl2 (20%) solution increased the percentage of insoluble matter in films but did not enhance their mechanical properties. FTIR analysis showed higher interactions in films treated in CaCl2 solutions despite the concentration used (2 vs 20%). The SEM observations of films showed a smoother surface with a higher density when films were treated in CaCl2 (20%) solution. The DPPD test showed that the oregano-based films had the highest antiradical properties.