Antioxidant activity and physical properties of hydroxypropylmethylcellulose films enriched with essential oils

In this study, the antioxidant activity and physical properties, such as water vapour permeability (WVP), oxygen permeability (OP), mechanical and optical properties of hydroxypropylmethylcellulose (HPMC) films containing essential oils of clove buds, sage and oregano were evaluated. Clove essential oil showed higher antioxidant activity in 2,2-diphenyl-1-picryl hydrazine (DPPH) radical-scavenging assay (IC50 = 2.71 µg•ml-1) and in a reduction power assay (IC50 = 53.54 µg•ml-1) but, in beta-carotene-bleaching test, butylated hydroxytoluene (BHT) showed higher (IC50 = 62.86 µg•ml-1) antioxidant activity. The results showed that addition of essential oils into HPMC films led to a significant decrease in WVP (2.30–1.49 ng•Pa-1m-1s-1), OP (488.78–235.95 ml•µm•kPa-1m-2d-1), colour differences (0–38.91), tensile strength (27.35–7.21 MPa), elongation at break (23.6–17.9%) and elastic modulus (537.54–202.12 MPa). Also, soybean oil without antioxidant was packed by HPMC films and some soybean oil samples after addition of the same essential oils and packed in glass bottles stored at accelerated conditions. The HPMC films combined with essential oils showed a moderate effect against soybean oil oxidation. In comparison between the films, HPMC film combined with clove essential oil was the most effective protectant against oxidation (43.3%).