Antioxidant and Antimicrobial Characterization of Active Films Based on Yeast Biomass and Thymol

Yeast biomass is a novel source for the production of biodegradable films and, joint to the incorporation of certain compounds from essential oils, it is possible to design promising active materials for food preservation. In this work, thymol was incorporated into yeast biomass matrices to develop bioactive films and this compound was satisfactory, retained by them without phase separation. IR spectra showed that thymol interacted with proteins and polysaccharides, but thymol did not substantially modify the mechanical properties, colour, and thermal decomposition of films. The active compound provided great antioxidant and antimicrobial capacity to the films. The inhibition of the ABTS•+ radical was higher than 80% by the addition of 8 or 10 wt% of thymol. Release of thymol from films to fatty food simulants at 4 °C, 25 °C, and 40 °C was fitted by the Crank model and diffusion coefficients at 40 °C were one order of magnitude higher than diffusion coefficients at 4 °C. Regarding antimicrobial activity, 10 wt% satisfactorily inhibited the growth of E. coli. The promising antioxidant and antimicrobial capacity of the active yeast biomass-thymol films could be used in the protection of fatty foods.