Controlled Release System by Active Gelatin Film Incorporated with β-Cyclodextrin-Thymol Inclusion Complexes

Essential oils such as thymol are added to food packaging film to obtain active films with antimicrobial and antioxidant properties. However, thymol is insoluble in water, and release rate of thymol is usually too fast. Therefore, a need exists to increase thymol solubility and to deliver thymol in a controlled manner from film matrix to food surface. In this study, spray dried inclusion complexes of beta-cyclodextrin/thymol (1:1 molar ratio) was incorporated into gelatin solution to obtain active gelatin films. Both inclusion complexes and active films showed sustained release of thymol. Physical properties and thymol release kinetics were evaluated for active films. For gelatin films with 8.25% (mass ratio) inclusion complexes, complete thymol release took 235 h, compared with 38 h for thymol release from inclusion complexes. The diffusion coefficient reached 2.04 x 10(-15) m(2) s(-1).