Effect of chitosan molecular weight on the antimicrobial activity and release rate of carvacrol-enriched films

Edible films based on three types of chitosan which differ on their molecular weight were developed as carriers of carvacrol. Stable film forming dispersions were obtained and the one developed from chitosan with higher molecular weight presented higher viscosity and larger carvacrol droplets. Olive oil and 96% ethanol were used as food-simulating solvents to determine the carvacrol release rate from the chitosan matrices. The release of carvacrol was much faster when it was submerged in ethanol. Besides, the higher the chitosan molecular weight employed in the films formulation, the faster the release rate towards both solvents. The films showed antimicrobial effectiveness against the gram-negative bacteria Pseudomona fragi, Shewanella putrefaciens and Aeromonas hydrophila, common spoilers of fish and seafood products. Thus, in order to slowdown the carvacrol release rate, the use of chitosan with a low molecular weight and technical applications targeted for low-moderate fat content products is suggested. [Display omitted] •Antimicrobial chitosan-carvacrol edible films from chitosans with different molecular weights.•Film forming dispersions with higher viscosity presented larger carvacrol droplets.•The higher the chitosan molecular weight, the faster the release rate to solvents.•The carvacrol release resulted much faster towards ethanol than to pure olive oil.•Chitosan-carvacrol films effective against gram-negative fish spoilers.