Synthesis and characterization of casein-based films with decanoic acid, ethanol and glycerol

Abstract

This study investigated the effect of glycerol, decanoic acid, and ethanol concentration on the mechanical, optical, and rheological properties of casein-based films. Edible films, a sustainable alternative to plastics, were developed from casein due to its exceptional film-forming and barrier properties. However, casein-only films are typically brittle, necessitating the use of plasticizers like glycerol. It was hypothesized that incorporating ethanol and decanoic acid, would improve the mechanical properties of the films while reducing the amount of glycerol necessary to reach desirable mechanical properties. Film-forming solutions were prepared using two different solvent systems: distilled water (0% ethanol) and 50% ethanol, and different concentrations of decanoic acid (0, 10 and 20%). The film’s mechanical properties (tensile strength and elongation at break), optical properties (absorbance), and the film-forming dispersions’ rheological properties (apparent viscosity) were characterized. Results showed that increasing ethanol content generally led to higher absorbance and reduced transparency. In contrast, higher concentrations of decanoic acid increased the apparent viscosity of the film-forming dispersions without ethanol. The study concluded that formulations with 20% decanoic acid combined with 20% glycerol, with or without ethanol, showed potential for use as packaging materials, as they balanced strength and flexibility. Although these films were classified as opaque, their suitability depends on the specific food application.