Natamycin release from alginate active films to liquid and semi-solid media

Alginate films containing natamycin as the antimicrobial agent were developed and its release from the films to liquid and semi-solid media with different water activities was evaluated. In samples immersed in liquid media, the release rate of natamycin increased with an increase in the water activity of the solutions. Effective diffusivities were estimated by fitting Fick’s second law to the data, obtaining values ranging from 0.52 × 10 –12 to 5.30 × 10 –12 cm 2 /s. The amount of natamycin that migrated to the semi-solid media indicated incomplete release, with 85% of the initial mass released in gels and only 33% released in cheese samples. This highlights the importance of evaluating the release behavior in real systems. The films were applied to slices of semi-hard cheese, previously inoculated with Aspergillus niger and Penicillium roqueforti . Colony counts on the surface of cheese samples sandwiched between active films were one log cycle lower than that in uncovered slices. Cheese samples covered with control films (without natamycin) also yielded fewer colonies but were not as effective.