Cassava starch films containing rosemary nanoparticles produced by solvent displacement method

Abstract

Cassava starch films containing rosemary nanoparticles were successfully produced using a simple approach. Different concentrations (5 and 20% w/w) of ethanolic extracts of rosemary were added to the film-forming aqueous blends containing cassava starch and glycerol, and in this way, rosemary nanoparticles were produced by the solvent displacement. The formulations added of the lowest extract amount led to films containing well distributed rosemary nanoparticles within the matrix. In contrast, higher extract concentration provoked the formation of agglomerates of nanoparticles within the films. Fourier transform infrared spectroscopy and thermogravimetric analysis suggested that the availability of hydroxyl groups within the starch matrix was decreased due to the presence of the rosemary-related compounds. Tensile properties of the cassava starch films were also influenced by the addition of rosemary extract. It was found that the rosemary nanoparticles were able to act as a reinforcement of the starch matrix increasing the elastic modulus and the tensile strength of the films up to 4.0-fold and 2.5-fold, respectively; while the strain at break was slightly decreased, compared with the control films. Finally, the release kinetics of rosemary polyphenols from cassava starch active films to aqueous and fatty food simulants was analyzed. In the aqueous medium, all active films released a polyphenols amount above 60% within the first hour of assay. In contrast, the release rate of rosemary polyphenols into ethanol (i.e. a fatty food simulant) was slower compared with the aqueous one.