Effect of pH on the effectiveness of whey protein/glycerol edible films containing potassium sorbate to control non-O157 shiga toxin-producing Escherichia coli in ready-to-eat foods

- The addition of PS to acidic WPC/Gly films led to inhibit the growth of STEC pathogens obtained from foods.
- PS release from films did not be affected by WPC/Gly films pH.
- Transparency improved with the incorporation of PS into more acidic films.
- WPC/Gly films may be useful to inactivate post-processing contaminants on ready-to-eat foods.
- The incorporation of antimicrobial agents to WPC/Gly edible films may have supplementary applications in food packaging.

Potassium sorbate (PS) (0.5%, 1.0% and 1.5% w/w) was included into whey protein concentrate (WPC)/glycerol (Gly) edible films at pH 5.2 and 6.0. The films inhibited or retarded the growth of Shiga toxin-producing Escherichia coli (STEC) pathogens in both diffusion and barrier tests. Bacterial growth inhibition was dependent on PS content at both pH values. PS release was not affected by pH. Scanning electron microscopy (SEM) was used to analyze the microstructure of the films and gain a better understanding of their optical parameters. Acidic control films (pH 5.2) prepared without PS were the least transparent. SEM micrographs confirmed the greater structural heterogeneity of these films, coinciding with opacity. The incorporation of PS into WPC/Gly films improved transparency and produced a smoother surface than acidic control ones. The utilization of active packaging based on whey proteins and organic acids to control and prevent the dissemination of STEC pathogens may be an effective, safe, ecological and relatively inexpensive alternative to be used in the food packaging industry.