Determination of antioxidant activity of surface‐treated PET films coated with rosemary and clove extracts

Abstract

Commercial PET films were surface treated and subsequently coated with either rosemary (RME) or clove (CE) extracts. Surface treatments involved (1) corona treatment, (2) chemical modification, and (3) plasma treatment. Radical scavenging activity (RSA) of both pure plant extracts and coated film extracts were determined using the 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) method. RME‐coated films showed a % RSA of 25.6%, 22.4%, and 24.1% for plasma, chemical modification, and corona treatment, respectively, at an extract concentration of 1402 ppm, respectively, while pure RME showed a %RSA of 16.0%. Respective %RSA values for CE were 25.0% for plasma, 25.2% for chemically modified, and 25.2% for corona‐treated films at 1402 ppm, while pure CE showed a %RSA of 47.6%. Thiobarbituric acid (TBA) test, performed on ground fish muscle wrapped in all types of employed films, showed a remarkable decrease in the degree of fish oxidation ranging between 50.0 and 80.0% after 6 days of storage. Contact angle measurements confirmed that surface chemically modified films had the highest adhesion strength followed by corona and plasma‐treated films. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X‐ray photoelectron spectroscopy (XPS) data also supported contact angle measurements. Finally, the oxygen permeability of surface‐treated films did not differ from untreated films indicating that surface treatment did not affect film barrier properties.