Antimicrobial, mechanical, and physicochemical properties of ethylene vinyl alcohol (EVOH) extruded films blended with propolis
Somayeh Hajinezhad, Bibi Marzieh Razavizadeh, Razieh Niazmand, Ismael Ghasemi
Abstract
Antimicrobial packaging is used for improving shelf life of food. Propolis is a natural substance with antimicrobial effects that can be applied in packaging. The current study investigated the mechanical and antimicrobial properties of active packaging films of ethylene vinyl alcohol including propolis. Crude propolis was added to the polymer matrix at different ratios (20%, 15%, 10%, 5%, and 0%; w/w) and the films were primed by extrusion method. The mechanical attributes of the films showed that the incorporation of propolis to the EVOH film reduced the elongation to tear of the films and decreased the tensile strength. Scanning electron microscopy images also demonstrated that the films had a more heterogeneous morphology than pure ethylene vinyl alcohol and propolis particles had a good distribution within the polymer matrixes. Agglomeration did not observe. In addition, water permeability (WVP) and oxygen permeability (OTR) decreased with raising propolis percentage in comparison with the control film significantly (p < .05). Differential scanning calorimetry test showed that an increase propolis in the polymer matrix reduced the crystallization temperature and increased the crystallinity percentage. Antimicrobial effect on Aspergillus Niger and Saccharomyces cerevisiae, Staphylococcus aureus, and Escherichia coli was increased with increased percentage of propolis in the blended films. However, its effect on Gram-positive Staphylococcus aureus was much more than the other microorganisms studied.