Incorporation of hydroxypropyl-β-cyclodextrins into chitosan films to tailor loading capacity for active aroma compound carvacrol

• HP-β-CD and coadjuvants can tailor carvacrol sorption capacity of chitosan films.
• Carvacrol sorption kinetics depends on the plasticization degree of the films.
• Release kinetics of carvacrol is controlled by environmental relative humidity.
• Films exhibited long-lasting antimicrobial properties against E. coli and S. aureus.

Chitosan incorporating hydroxypropyl-β-cyclodextrins and glycerol films capable of modulating loading capacity and release of carvacrol have been developed. Films were obtained by casting and conditioned at different relative humidities (RH) prior to immersion in liquid carvacrol. Incorporation of cyclodextrins in the chitosan matrix slightly increased sorption of carvacrol and it was necessary to use glycerol and water as coadjuvants to control loading of the films with the volatile. Good agreement was found between carvacrol retention and plasticization of the film by glycerol and water. The kinetics of carvacrol sorption by the films was evaluated at 25 °C. Diffusion coefficients of sorption varied from 0.011 × 10−14 m2/s for films incorporating 35% glycerol and conditioned at 0% RH to 1.9 × 10−14 m2/s for films incorporating 35% glycerol and conditioned at 75% RH. Release of carvacrol from the films was greatly affected by RH. The films showed antimicrobial activity against Staphylococcus aureus and Escherichia coli after 20 days of storage at 25 °C and 43% environmental RH. These films could be useful in the design of systems for delivering active volatiles.

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