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

Abstract

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.

Physicochemical and Antimicrobial Properties of Biopolymer-Candelilla Wax Emulsion Films Containing Potassium Sorbate – A Comparative Study

“…It is important to note that SPI films were the only one of the control films that exhibited wax bloom visible to the naked eye, which, however, was reduced after addition of KS. In accordance with the present results, previous studies on whey protein films have also demonstrated that the addition of KS (0.5-1.5 %) could enhance film transparency (Pérez et al 2014). It was an interesting observation that the addition of KS significantly enhanced UV-blocking properties (especially in the middle UV) of all tested films.…”

“…The results of our study seem to be partially consistent with these findings. In a study described by Pérez et al (2014), the MICs of KS for pathogenic strains of E. coli at pH 6.0 were 2.5-5.0 mg/ml. These authors showed that the activity of KS was strongly dependent on pH; the KS concentrations needed to inhibit microbial growth in a liquid medium at pH 6.0 was 2-4 levels higher than at pH 5.2.…”

“…Low concentrations of KS (0.05 to 0.3 % by weight) are sufficient to reduce microbial growth in food, but the use of KS is effective up to pH 6.5. Consequently, the pH of the packaging material and the food to which packaging is applied are important parameters (Pérez et al 2014;Theron and Rykers 2011). Numerous trials have been aimed at the invention of an appropriate technology for KS-containing antimicrobial polymer materials.…”

“…Numerous trials have been aimed at the invention of an appropriate technology for KS-containing antimicrobial polymer materials. A great deal of research has been dedicated to developing active packages through the use of edible films and coatings (Basch et al 2013;Famá et al 2005;Flores et al 2007;Garcia et al 2012;Kristo et al 2008;Mehyar et al 2014;Ofman et al 2004;Floros 2001, 2003;Pérez et al 2014;Sayanjali et al 2011;Shen et al 2010;Valencia-Chamorro et al 2008). The application of these kinds of materials is one of the innovations of packaging technology aiming to improve the mechanical properties of the food, minimize respiration in fruits and vegetables, limit the movement of moisture and other gases, provide antimicrobial or antioxidant capabilities to the product, enhance the sensory properties, and extend the shelf life of the product.…”

Role and importance of the awareness for whey in dairy sector at an international level

“…Moreover, they have a great capacity to form films (Chen et al, 1995;Pérez et al, 2002;Javanmard, 2009). Because of the fact that they are edible and biodegradable, using whey proteins to manufacture films has gained a great deal of popularity among producers (Krochta and Mulder-Johnston, 1997;Ramos et al, 2012;Pérez et al, 2014 ).…”