In vitro antibacterial and antioxidant properties of chitosan edible films incorporated with Thymus moroderi or Thymus piperella essential oils

The aim of this work was to evaluate chitosan edible films incorporated with the EOs of two aromatic herbs, Thymus moroderi and Thymus piperella for (i) the growth inhibition of some bacterial strains (ii) their total phenolic content (TPC), and (iii) their antioxidant activity by means of three different antioxidant tests to define if the chitosan edible films incorporated with these EOs could be used as natural active films for food use. The agar disc diffusion method was used to determine the antibacterial activities of chitosan edible films. For the antioxidant activity, three different analytical assays were used (DPPH, FRAP and FIC). The chitosan films containing T. piperella EO (CH + TPEO) were more effective (p < 0.05) against Serratia marcenscens and Listeria innocua than chitosan films containing T. moroderi EO (CH + TMEO), while no statistically differences were found (p > 0.05) between CH + TPEO and CH + TMEO against Aeromonas hydrophila and Achromobacter denitrificans. The CH + TMEO films showed lower (p < 0.05) antioxidant activity, at all concentrations and with all methods assayed, than CH + TPEO. The antioxidant activity occurred in a concentration dependent manner. The results showed that chitosan edible films incorporated with T. piperella and T. moroderi EOs could be used as active films due to its excellent antibacterial and antioxidant activities.