Physicochemical, thermal, mechanical, optical, and barrier characterization of chia (Salvia hispanica L.) mucilage-protein concentrate biodegradable films.

In this study, the effect of chia mucilage (CM) and protein concentrate (CPC) contents on the physicochemical, thermal, mechanical, and optical characteristics of developed films was evaluated. Films were prepared dissolving CM:CPC mixtures (1% w/v) in seven ratios (0:1, 1:4, 1:2, 1:1, 2:1, 4:1, 1:0). Microstructure of treatments with higher CM revealed the formation of polysaccharide granules. A semicrystalline behavior was manifested in 1:0, which decreased as CPC content in the formulations increased. Contact angle values obtained for 1:1 and 2:1 were the highest (61.24° and 62.44°), evidencing less affinity to water than other films. TGA analysis suggest that films showed thermal stability at less than 225 °C. Melting temperatures above 85 °C were found for all films in the evaluated range (50 °C to 200 °C) of DSC analysis. Higher CM concentrations in films increased the force required to break them (13.5 MPa) and their elongation capacity (5.20%). As the CM ratio in formulations was increased, the color difference was lower (ΔE = 27.45), water vapor permeability was higher (10.9 × 10-11  g/m·s·Pa), but transparency was statistically the same for all treatments (6.62 to 7.26). After analyzing all films properties, 2:1 formulation corresponding to 25:75% w/v mixtures of CM:CPC would be the best option for use in food packaging.