Abstract
The application of starch films, such as food packaging materials, has been restricted due to poor mechanical and barrier properties. However, the addition of a reinforcing agent, cellulose nanofibers (CNF) and also thymol, into the films, may improve the properties of films. This work investigates the effects of incorporating different concentrations of thymol (3, 5, 7, and 10 wt.%) on physical, mechanical, water vapor barrier, and antibacterial properties of corn starch films, containing 1.5 wt.% CNF produced using the solvent casting method. The addition of thymol does not significantly affect the color and opacity of the films. It is found that the tensile strength and Young’s modulus of the films decreases from 10.6 to 6.3 MPa and from 436.9 to 209.8 MPa, respectively, and the elongation at break increased from 110.6% to 123.5% with the incorporation of 10 wt.% thymol into the films. Furthermore, the addition of thymol at higher concentrations (7 and 10 wt.%) improved the water vapor barrier of the films by approximately 60.0%, from 4.98 × 10—9 to 2.01 × 10—9 g/d.m.Pa. Starch/CNF/thymol bionanocomposite films are also found to exhibit antibacterial activity against Escherichia coli. In conclusion, the produced starch/CNF/thymol bionanocomposite films have the potential to be used as antibacterial food packaging materials.
Highlights
Petroleum-based plastics, such as polyethylene (PE), polypropylene (PP), and polyamide (PA), are often used for food packaging due to their good physicochemical and processing properties [1]
The antibacterial properties of the starch/cellulose nanofibers (CNF) bionanocomposite films incorporated with different concentrations of thymol were demonstrated in vitro through the disc diffusion method against E. coli bacteria
Starch/CNF bionanocomposite films incorporated with different concentrations of thymol were successfully produced and investigated
Summary
Petroleum-based plastics, such as polyethylene (PE), polypropylene (PP), and polyamide (PA), are often used for food packaging due to their good physicochemical and processing properties [1]. This leads to a large percentage of global plastic pollution, as they are non-degradable and inconvenient to be recycled because they are usually contaminated with food. Among the various sources of starch, corn starch has the highest amylose content, which can vary from 22.4 to 67.8% [4]. Given that the film-forming properties of starch are dependant on the amylose content in the starch, films produced from corn starch are more rigid and strong [5]
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