Mathematical model to describe the release of an antimicrobial agent from an active package constituted by carvacrol in a hydrophilic EVOH coating on a PP film

Antimicrobial active packaging is a novel technology in which a chemical compound (or mixture) is purposely incorporated into a packaging material to be released into the food to protect it from deterioration. The effectiveness of an antimicrobial package is strongly related to the balance between the controlled release of the active compound and microbial growth kinetics. This work characterizes and models the release of carvacrol from an EVOH coating on a PP film which can be employed as an active packaging system. The kinetics and extent of carvacrol mass transport within the packaging components were fully characterized as a function of relative humidity. As expected, water uptake by the EVOH coating acts as a triggering mechanism for activity. The partition equilibrium for carvacrol in the complex film largely favors (10,000-fold) the EVOH layer in dry conditions, although in humid conditions the solubility in both polymers is very close (4-fold). Kinetically, the presence of humidity increases the value of D for carvacrol in EVOH from 3 . 10(-19) m(2)/s in dry conditions to 3 . 10(-15) m(2)/s in a wet environment. After the experimental characterization of carvacrol transport, the efficiency of the release of carvacrol was estimated with a novel mathematical model based on the finite element method and successfully compared with the evolution of carvacrol concentration in a real packaging system. The model developed can be employed in the optimization of package design in order to ensure the maintenance of a specific concentration of the active agent in the headspace, high enough to prevent potential growth of a particular foodborne spoiling or pathogenic microorganism on the preserved foodstuffs. This model could easily be extended to similar packaging systems as long as an inventory of experimental data for all the parameters and coefficients involved is available, sufficiently complete to fulfill all the mathematical requirements demanded by the model. (C) 2011 Elsevier Ltd. All rights reserved.