Morphological and Mechanical Characterization of Films Incorporating Porphyran Extracted from Porphyra Dioica

Abstract

This paper studies the effects of glycerol plasticizers and/or alginate, pectin, and carboxymethylcellulose polysaccharides on the mechanical and physical properties of porphyran-based films to evaluate the films’ ability to be used as food packaging. Films were characterized in terms of their composition, microstructural and morphological features, thermal properties, water interaction, and mechanical performance. All films are homogeneous, transparent, and slightly brownish in color. The structures are amorphous and crosslinked, showing the films’ thermoset nature. Moisture content and water solubility depend on the second polysaccharide added to the porphyran, but they both increase with the addition of glycerol to the formulations; water vapor permeability is strongly affected by the second polysaccharide in the formulation. The films display stiff and brittle mechanical behavior, but ductility increases significantly in formulations containing glycerol plasticizers. The barrier and mechanical performance values of the materials produced were found to be lower than those reported for commercial food packaging. The formulations containing glycerol displayed lower water vapor permeability values, ranging from 2.98 for porphyran/carboxymethylcellulose/glycerol to 6.65 mm·g·d−1·m−2·kPa−1 for porphyran/alginate/glycerol films. All films, except porphyran/glycerol and porphyran/alginate/glycerol, had ultimate tensile strengths above 10 MPa—the threshold value that ensures that a package is ductile enough to withstand handling and forming operations. Furthermore, the porphyran/pectin/glycerol and porphyran/carboxymethylcellulose/glycerol films displayed sufficiently high ductility values of 2.94 and 3.10%, respectively. These results indicate that the studied porphyran/pectin/glycerol and porphyran/carboxymethylcellulose/glycerol formulations have a combination of physical and mechanical properties that ensure adequate film integrity and function through the complete food packaging supply chain. The results here reported represent an opportunity to extend the scope of porphyran films to applications in the dry food packaging industry.