Characterization of biodegradable films based on extracellular polymeric substances extracted from the thermophilic microalga Graesiella sp.

Abstract

In this research, a new type of biodegradable film based on the extracellular polymeric substances (EPS) and isolated from the thermophilic microalga Graesiella sp., was formulated and characterized. The EPS film was 0.221 mm thick. Atomic force microscopy and scanning electron microscopy images revealed a homogeneous character with a lamellar microstructure. The EPS film displayed yellowish color, high transparency, high ultraviolet barrier properties, and low oxygen (0.008 SI), and water-vapor permeability (0.037 SI). Film tensile strength (16.24 MPa) and elongation at break (4.76%) were in the range of common biofilms and the thermal analyses showed high transition temperature (126 °C) and high thermal stability (up to 800 °C). Compared to ascorbic acid, results indicated that the EPS film shows a higher antioxidant activity, mainly as β-carotene anti-bleaching (84%), DPPH- free radical scavenging ability (80%), and ferrous iron-chelating (55%). Graesiella sp., EPS film effects on beef meat packaging were studied during nine days of cold storage. Compared to polyvinylchloride-packed meat, EPS-packed meat samples showed higher stability of color (redness = 13.6) and pH (5.85) during storage and low proliferation of total viable counts (4.04 CFU·g−1) and Pseudomonas bacteria (4.09 CFU·g−1). They also exhibit lower drip loss (9%) and less metmyoglobin (32%), heme iron (4.87 μg·g−1) total volatile basic nitrogen (TVB-N = 22.96 mg·kg−1), and lipid oxidation (MDA = 0.025 mg·kg−1). The obtained results highlight the potential for use of microalgae EPS as a new film-forming material that could be applied in beef meat preservation.