Antimicrobial, mechanical, and moisture barrier properties of low pH whey protein-based edible films containing p-aminobenzoic or sorbic acids

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.