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The diffusion of acetic or propionic acids from thin (44 to 54 mm) 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°C, 10°C, or 24°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°C to 4°C resulted in a reduction of diffusion coefficients from 2.59 × 10 -12 m 2 .s -1 to 1.19 × 10 -12 m 2 .s -1 for acetic acid and from 1.87 × 10 -12 m 2 .s -1 to 0.91 × 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.

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