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) chitos an-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 t o be unaffected by pH in the range of values tested, but a decrease in temp erature from 24 degrees C to 4 degrees C resulted in a reduction of diffusi on 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 energie s of 27.19 J.mole(-1) (acetic) and 24.27 J.mole(-1) (propionic), Incorporat ion of lauric acid or essential oils (cinnamaldehyde or eugenol) into the c hitosan film at the time of preparation produced a subsequent reduction in the diffusion of acetic or propionic acid, and maximum effects were obtaine d with lauric acid and cinnamaldehyde incorporated to final concentrations of 1.0% and 0.5% (w/w), respectively.