Eugenol-loaded LLDPE films with antioxidant activity by supercritical carbon dioxide impregnation

• Eugenol-loaded LLDPE films were obtained by supercritical CO2 impregnation at 45 °C.
• Higher impregnation yields were obtained at slow depressurization (0.5–1 MPa/min).
• Films showed antioxidant activity via DPPH inhibition.
• High pressure impregnation reduced polymer crystallinity and ductility but not its tensile strength.

In this work, linear low density polyethylene (LLDPE) films were impregnated with eugenol using supercritical CO2 impregnation, as a strategy for obtaining a loaded material to be potentially applied in active food packaging. Eugenol, the main component of clove oil, is well known as a natural antioxidant and antimicrobial agent. Impregnation runs were performed in a lab-scale high pressure stirred cell at 45 °C during 4 h, and the effect of pressure (10, 12 and 15 MPa) and depressurization rate (0.5, 1 and 5 MPa/min) on impregnation yield was evaluated. Yields of 1–6% (w/w) were achieved, with higher values at low depressurization rate. Film samples were characterized by infra-red spectroscopy (FTIR) and differential scanning calorimetry (DSC). FTIR analysis suggested that the distribution of eugenol in the films is not totally homogeneous. DSC revealed a decrease in the crystallinity degree in the impregnated samples as well as in films subjected to pressurization with CO2 but not loaded with eugenol. Changes in mechanical properties were also investigated in a texturometer. A decrease of LLDPE Young modulus and ductility was observed after high pressure impregnation, although tensile strength was not significantly affected. Finally, the antioxidant activity of the eugenol-loaded films was assessed via the DPPH inhibition test.

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