Effect of lauric acid and nisin-impregnated soy-based films on the growth of Listeria monocytogenes on turkey bologna.

Research in development of antimicrobial packaging applications for further processed meats has become more common with recent outbreaks of contamination of these products. In this present study, lauric acid (8%, wt/wt) and 2.5% pure nisin (4%, wt/wt) were incorporated singly and together into thermally compacted soy films. Biocide-impregnated films were compared to control films containing no biocide for inhibition of Listeria monocytogenes in liquid medium and on turkey bologna surface. L. monocytogenes suspended in 1% peptone medium exposed to control films increased from 106 to 10(9) after 48 h exposure at 22 C. Films with nisin alone suppressed cell numbers 1 log cfu/mL after 2 h but cell numbers increased to 10(8) after 24 and 48 h at 22 C. Films containing lauric acid and nisin completely eliminated detectable cells from a 10(6) culture after 8 h of exposure to the liquid medium (22 C). Refrigerated bologna exposed to control films increased by 0.5 log from 10(6) after 21 d at 4 C. Nisin films reduced cell numbers on turkey bologna from 10(6) to 10(5) after 21 d, as did films containing nisin and lauric acid. Films with lauric acid alone reduced L. monocytogenes culture from 10(6) to < 102 after 48 h and by 1 log on turkey bologna after 21 d.