Increasing consumer demand for microbiologically safer foods, greater convenience, smaller packages, and longer product shelf life is forcing the industry to develop new food-processing, cooking, handling, and packaging strategies. Nonfluid ready-to-eat foods are frequently exposed to postprocess surface contamination, leading to a reduction in shelf life. The food industry has at its disposal a wide range of nonedible polypropylene- and polyethylene-based packaging materials and various biodegradable protein- and polysaccharide-based edible films that can potentially serve as packaging materials. Research on the use of edible films as packaging materials continues because of the potential for these films to enhance food quality, food safety, and product shelf life. Besides acting as a barrier against mass diffusion (moisture, gases, and volatiles), edible films can serve as carriers for a wide range of food additives, including flavoring agents, antioxidants, vitamins, and colorants. When antimicrobial agents such as benzoic acid, sorbic acid, propionic acid, lactic acid, nisin, and lysozyme have been incorporated into edible films, such films retarded surface growth of bacteria, yeasts, and molds on a wide range of products, including meats and cheeses. Various antimicrobial edible films have been developed to minimize growth of spoilage and pathogenic microorganisms, including Listeria monocytogenes, which may contaminate the surface of cooked ready-to-eat foods after processing. Here, we review the various types of protein-based (wheat gluten, collagen, corn zein, soy, casein, and whey protein), polysaccharide-based (cellulose, chitosan, alginate, starch, pectin, and dextrin), and lipid-based (waxes, acylglycerols, and fatty acids) edible films and a wide range of antimicrobial agents that have been or could potentially be incorporated into such films during manufacture to enhance the safety and shelf life of ready-to-eat foods.

: Low pH (5.2) whey protein isolate‐based edible films containing p‐aminobenzoic acid (PABA) or sorbic acid (SA) were developed and assessed for inhibition of Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella Typhimurium DT104 in a disc diffusion assay. Water vapor permeability (WVP), tensile strength (TS), and percent elongation (%E) were also determined. Using 1.5% PABA and SA, average inhibition zone diameters were 21.8, 14.6, 13.9, and 26.7, 10.5, 9.7 mm for L. monocytogenes, E. coli O157:H7, and S. Typhimurium DT104, respectively. Three strains of S. Typhimurium DT104 were resistant to 0.5% SA. Addition of PABA and SA increased %E, but decreased TS. WVP was not affected by 0.5% and 0.75% SA; however, PABA increased WVP.

Whey protein isolate (WPI) films (pH 5.2) containing 0.5 to 1.0% p-aminobenzoic acid (PABA) and/or sorbic acid (SA) were assessed for antimicrobial and mechanical properties while in contact with sliced bologna and summer sausage that were inoculated with Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella enterica subsp. enterica serovar Typhimurium DT104. WPI films containing SA or PABA decreased L. monocytogenes, E. coli, and S . Typhimurium populations by 3.4 to 4.1, 3.1 to 3.6, and 3.1 to 4.1 logs, respectively, on both products after 21 d at 4 °C. Background flora was inhibited compared with controls. Film tensile strength decreased while % elongation remained unchanged following 72 h of product contact.

Whey protein isolate (WPI) films (pH 5.2) containing p-aminobenzoic acid (PABA) were heat-sealed to form casings. Hot dogs prepared with WPI, collagen, or natural casings were cooked, surface-inoculated to contain 10 3 Listeria monocytogenes CFU/g, and examined for numbers of L. monocytogenes, mesophilic aerobic bacteria (MAB), lactic acid bacteria (LAB), and yeast/mold during 42 d of storage at 4°C. Listeria populations on hot dogs prepared with WPI-1.0%-PABA casings remained relatively unchanged; however, numbers of Listeria on hot dogs prepared with WPI-0.0%-PABA, collagen, and natural casings increased about 2.5 logs during 42 d of refrigerated storage. Populations of MAB, LAB, and mold on WPI-1.0%-PABA casings were 1 to 3 logs lower compared to others casings.