Experimental study and modeling of nisin diffusion in agarose gels

Research in safety of processed food has focused on the use of anti-microbial compounds to suppress pathogenic bacteria growth such as Listeria monocytogenes and Staphylococcus aureus. Previous studies developed an anti-microbial edible film, incorporating the bacteriocin nisin. Nisin effectiveness was based on both nisin desorption from the film and its diffusion in the food product. In this present work., and as a preliminary study, nisin diffusion in agarose gel was investigated. The apparent diffusion coefficients were calculated, taking into account factors influencing the diffusion rates such as nisin concentration, diffusion time and temperature. Influence of agarose content on nisin diffusion was also evaluated. As a result, Fick's second law well represented nisin diffusion in agarose gel. In 3% (w/w) gel, the diffusion coefficient values varied between 1.92 x 10(-11) and 8.14 x 10(-11) m(2) s(-1) for temperatures ranged between 5.4 and 22.3 degreesC. Diffusion phenomena satisfied Arrhenius relationship. Agarose content from 3% to 6% did not have any effect on nisin diffusion. However, agarose content of 8% significantly reduced nisin diffusion in agarose gel cylinders. (C) 2003 Elsevier Ltd. All rights reserved.