κ-Carrageenan/poly(vinyl alcohol) functionalized films with gallic acid and stabilized with metallic ions

Given the environmental issues caused by the extensive use of conventional petroleum-based packaging, this work proposes functional films based on commercial kappa-carrageenan (kappa c), poly(vinyl alcohol) (PVA), and gallic acid (GA) prepared by the casting method. Metallic ions in the kappa c composition stabilized the films, supporting processability and suitable mechanical properties. However, the incorporated GA amount (6.25 and 10 wt%) in the films created from an aqueous kappa c solution at 3.0 % wt/v (kappa c3) prevented crystalline domains in the resulting materials. The kappa c3/GA6.25 and kappa c3/GA10 films had less tensile strength (8.50 +/- 0.61 and 10.28 +/- 0.65 MPa) and high elongation at break (2.36 +/- 0.16 and 1.19 +/- 0.17 %) compared to the other samples, respectively. Low kappa c contents (kappa c2.5/GA6.25 and kappa c2.5/GA10) promoted stiff films and less permeability to water vapor (5.36 +/- 0.51 and 3.76 +/- 0.02 [x10- 12 g(Pa x m x s)-1], respectively. The kappa c/GA weight ratio also influenced the film wettability, indicating water contact angles (WCAs) between 55 and 74 degrees. The surface wettability implies a low oil permeability and high water swelling capacity of up to 1600 %. The kappa c/GA also played an essential role in the film's antimicrobial action against Staphylococcus aureus and Escherichia coli. Thus, the kappa c3/GA10 film showed suitable physical, chemical, and biological properties, having the potential to be applied as food coatings.

Automated summary

This study proposes a method for preparing functional films using commercial kappa-carrageenan, poly(vinyl alcohol), and gallic acid. The films exhibit suitable mechanical properties and antimicrobial action, making them potential candidates for food coatings.