Inactivation of Listeria monocytogenes on beef bologna and Cheddar cheese using an antimicrobial polyvinylidene chloride-based food wrap
P. LIMJAROEN1, B. Harte1, H. E. LOCKHART1, and E. T. Ryser2. (1) School of Packaging, Michigan State University, 130 Packaging Building, East Lansing, MI 48824, (2) Department of Food Science and Human Nutrition, Michigan State University, 2108 S. Anthony Hall, East Lansing, MI 48824
Listeria monocytogenes continues to pose a major threat to the food industry as a post-processing contaminant. Commonly found in home refrigerators, this psychrotrophic pathogen can readily contaminate refrigerated foods and grow in some products to potentially hazardous levels.
This study investigated the ability of a newly developed antimicrobial polyvinylidene chloride-based food wrap to inactivate L. monocytogenes and extend the shelf-life of beef bologna and Cheddar cheese.
Sorbic acid-containing polyvinylidene chloride (Saran F-310) films were made by a solvent-casting method using methyl ethyl ketone. Polyvinylidene chloride film solutions containing 0, 1.5 and 3.0% sorbic acid were cast on glass plates (23 x 33 cm) and dried at 85°C for 5 minutes. These films were aseptically cut and placed between 3-mm thick slices of commercially produced beef bologna which were previously surface inoculated with L monocytogenes at a level of 103 CFU/g. Locally purchased Cheddar cheese was cut into 3 x 3 x 2.5 cm cubes, surface inoculated to contain 105 L. monocytogenes CFU/g, wrapped with 0, 1.5 or 3% sorbic acid films and store at 4°C. Both products were examined at appropriate intervals for numbers of L. monocytogenes, mesophilic aerobic bacteria, lactic acid bacteria, and yeast/mold using Modified Oxford Agar, Plate Count Agar, MRS Agar, and Rose Bengal Agar, respectively.
Films containing 1.5 and 3.0% sorbic acid decreased L. monocytogenes populations 0.61 and 1.25 logs, respectively, on bologna after 28 days of refrigerated storage and 0.8 and 1.33 logs, respectively on Cheddar cheese after 35 days of storage; whereas Listeria populations increased 5.84 logs and remained constant on bologna and Cheddar cheese, respectively, for the sorbic acid-free controls.
These films, which also inhibited mesophilic bacteria, lactic acid bacteria and yeast/mold, may be useful in enhancing the safety and shelf-life of bologna and Cheddar cheese.
Session 100B, Food Packaging