Release of nisin from methylcellulose-hydroxypropyl methylcellulose film formed on low-density polyethylene film

Low-density polyethylene film was coated with a solution containing a high-molecular-weight or low-molecular-weight methylcellulose and hydroxypropyl methylcellulose. Films contained 10000, 7500, 5000, 2500, or 0 IU/cm(2) nisin. Film samples were placed into peptone water, and 10-muL samples were removed and placed onto spiral plated lawns of Listeria monocytogenes. Zones of inhibition were measured using a caliper. Films containing 5000, 7500, and 10000 IU/cm(2) nisin inhibited L. monocytogenes after 30 min; films with 7500 and 10000 IU/cm(2) nisin inhibited L. monocytogenes after 60 min and 8 h, respectively. No zones of inhibition were observed after 24 h and 4 d for all films. After 8 d, zones of inhibition were observed for films with a levels of nisin except 2500 IU/cm(2). Films with 0 and 2500 IU/cm(2) nisin did not produce zones of inhibition throughout the study. Molecular weight of the cellulose-based carrier had no effect on inhibition of L. monocytogenes. A standard curve of inhibition was developed using solutions of 10000, 7500, 5000, 2500, or 0 IU/cm(2) nisin applied directly to lawns of L. monocytogenes. The amount of inhibition using a direct application of a solution was 25% to 50% more effective for inhibition of L. monocytogenes compared with the coated film samples. Overall, the coated film samples were effective for inhibition of L. monocytogenes, particularly when 7500 and 10000 IU/cm(2) nisin were used, but the release of nisin was not controlled and did not provide consistent inhibition throughout the 8-d study.