Investigating Physicochemical Characteristics of the Starch-polyvinyl Alcohol Active Films Containing Thyme Essential Oil and Its Emulsion

Abstract

Background and Objectives: Recently, studies have been carried out on effects of various essences on biodegradable films. The aim of this study was to investigate physicochemical characteristics of starch-polyvinyl alcohol active film containing thyme essential oil and its emulsion. Materials and Methods: To produce active films, after preparing starch-polyvinyl alcohol solution, various concentrations of thyme essential oil (1, 3 and 5) and 10 concentration of thyme emulsions (emulsion 1, 3 and 5) were used. Results: Based on the results, films containing essential oil and emulsion included similar effects on all physicochemical, mechanical and microbial characteristics of the film. Thus, addition of thyme essential oil and its emulsion to the film caused significant (p < 0.05) increases in the parameters of thickness, moisture absorption over time, contact angle and antioxidant activity of the films. Increases affected microbial characteristics of the films and both of them increased the area of growth inhibition of Escherichia coli and Staphylococcus aureus. The FTIR results showed that all films included a broad absorption band at 3000–3700 cm2, which was caused by the free stretching vibration of intramolecular and intermolecular hydroxyl groups. For the scanning microscopic structure or SEM results, it showed that the surface of the films loaded with the essential oil was rougher, also showing a little accumulation with increasing concentration. Conclusion: In general, prepared films included good quality and microbial load on foods, which could be used as active packages. © 2024, National Nutrition and Food Technology Research Institute. All rights reserved.