Hygroscopicity of pectin-propolis films: sorption isotherms and thermodynamic properties

Abstract

ABSTRACT: Bio-based materials from proteins, polysaccharides, and lipids have been studied as biodegradable alternatives to synthetic plastics, as well as matrices for incorporation of bioactive substances. In this context, pectin is a polysaccharide used to produce flexible food packaging films. Propolis is a complex mixture of resinous substances with antimicrobial and other biological properties that can be used to generate active food packaging. However, the application of such materials is still limited due to their hydrophilic nature. Thus, this experimentally evaluated the sorption isotherms and isothermal heat of sorption of pectin-propolis films at temperatures of 15, 25, 30, and 35 °C, and determined the mathematical model that best fits the experimental data obtained. The pectin was extracted from pequi mesocarp, a widely consumed fruit in the Brazilian cerrado biome that generates large amounts of peels (exocarp and mesocarp) which are discarded. Among the mathematical models studied, the Sigma Copace model was found to best represent the hygroscopic behavior of the pectin-propolis films. The isothermal heat of sorption decreased with increasing water content, and the films presented similar behavior to agricultural products. The understanding of such film’s behavior contributed to the application of pectin-propolis films produced using pequi mesocarp as a pectin source.

Keywords

• mathematical modeling
• mesocarp
• Sigma Copace model