Diffusion of acetic and propionic acids from chitosan-based antimicrobial packaging films

The diffusion of acetic or propionic acids from thin (44 to 54 mu m) chitosan-based antimicrobial packaging films in which they were incorporated was measured after immersion of the films in water, and the effects of pH (5.7, 6.4, or 7.0) and temperature (4 degrees C, 10 degrees C, or 24 degrees C) on diffusion were investigated, The kinetics of acetic- and propionic-acid release deviated from the Fickian model of diffusion. Diffusion was found to be unaffected by pH in the range of values tested, but a decrease in temperature from 24 degrees C to 4 degrees C resulted in a reduction of diffusion coefficients from 2.59 x 10(-12) m(2).s(-1) to 1.19 x 10(-12) m(2).s(-1) for acetic acid and from 1.87 x 10(-12) m(2).s(-1) to 0.91 x 10(-12) m(2).s(-1) for propionic acid. The effect of temperature on diffusion was well (r(2) > 0.9785) described by an Arrhenius-type model with activation energies of 27.19 J.mole(-1) (acetic) and 24.27 J.mole(-1) (propionic), Incorporation of lauric acid or essential oils (cinnamaldehyde or eugenol) into the chitosan film at the time of preparation produced a subsequent reduction in the diffusion of acetic or propionic acid, and maximum effects were obtained with lauric acid and cinnamaldehyde incorporated to final concentrations of 1.0% and 0.5% (w/w), respectively.