Seaweed-based Films for Potential Food Packaging Applications

Abstract

The focus on environmental issues and the challenges related to traditional plastic materials has triggered the use of bio-based packaging materials. Alginate is a natural biopolymer with good film-forming properties. In addition, the high accessibility, low cost, biodegradability, and composability of biopolymers make them desirable candidates for use in more sustainable food packaging systems. However, their commercial application is limited due to low thermal stability, brittleness, and poor mechanical and water barrier properties. The incorporation of natural fillers such as seaweed may potentially enhance the properties of biopolymer films. In this study, we investigated the effect of seaweed powder as a bio-filler in alginate-based films at different concentrations (10, 30, and 50%, w/w alginate) and particle sizes (100 and 200 μm) on film mechanical, barrier, antioxidant, and antimicrobial properties which are essential for food packaging applications. In addition, selected films were prepared with glycerol (10% w/w), plasma activated water (PAW), and seaweed extract solution (50% w/w) processed at different temperatures (25, 70, and 100°C). All films were produced using the solvent casting method. The addition of seaweed powder did not have any positive effect on the mechanical properties of the alginate films. However, the barrier (water vapor transmission rate) and antioxidant properties were improved with seaweed filler addition regardless of concentration. Similar results were also observed with the glycerol-containing alginate films. The mechanical properties (tensile strength and modulus, but not elongation at break) of the films prepared with PAW improved as compared to the films prepared in distilled water, while a significant decrease was observed when incorporated with seaweed filler. The films prepared in PAW also showed improved barrier properties compared to those prepared in distilled water. Moreover, the barrier and antioxidant properties, as well as the tensile modulus, of the alginate films prepared in seaweed extract solution (50% w/w) improved as compared to pure alginate. The antimicrobial activity of the alginate film-forming solution with seaweed bio- fillers was confirmed on Escherichia coli and Staphylococcus aureus at 37°C in combination with PAW, and at 10°C, regardless of PAW treatment. A more pronounced inhibitory effect was observed on the Gram-positive S. aureus than on the Gram-negative E. coli, which has been attributed to the different composition and structure of the respective cell walls. This study has demonstrated the potential of seaweed filler in combination with PAW towards enhanced functionality and bioactivity of alginate films for potential food packaging applications.