Edible films based on gelatin, carboxymethyl cellulose, and their blends as carriers of potassium salts of iso-α-acids: Structural, physicochemical and antioxidant properties

Abstract

Edible films based on gelatin/carboxymethyl cellulose (GEL/CMC) blends (100/0, 75/25, 50/50, 25/75, and 0/100) incorporated with increasing concentrations (0, 15, 30, 60 mg/100g) of potassium salts of iso-α-acids (KIAA) were prepared and characterized. Mixing of GEL with CMC at 50/50 and 25/75 ratios yielded films with phase-separated microparticles. Incorporation of KIAA into the CMC100 carrier resulted in rough and opaque films. The films became more amorphous with the increasing concentration of CMC. Consequently, the higher polysaccharide content was accompanied by lower tensile strength (TS) and elastic modulus (EM). All films with the high concentration of KIAA (60 mg/100g) displayed reduced TS and EM. The control GEL-rich films exhibited significantly lower water vapor permeability (WVP) than the films with the medium- and high-levels of CMC. The KIAA-protein interactions were most likely responsible for the slight decrease in the WVP value of the GEL100 film. In general, an increase in the KIAA concentration resulted in darker yellow-green films with reduced UV/Vis transparency. As expected, the KIAA content in the films decreased over time. Probably due to the high pH, the CMC-rich films exhibited the best ability to stabilize KIAA. The CMC100 films exhibited over 10-fold weaker antiradical potential than the GEL100 films. The highest concentration of KIAA (60 mg/100g) was not an effective dose to cause a significant improvement in the antioxidant potential of all films. The antioxidant activity of the films decreased during storage.