Bactericidal and bacteriostatic effects of sodium polyphosphate emulsifying salts on selected targets in processed cheese

Processed cheeses (PC) are products with extended shelf-lives, they have in their composition such additives as emulsifying salts and preservatives. Emulsifying salts are used due their desirable emulsification properties, however, little is known about their inhibitory activity against microorganisms that can survive and multiply in these products; jeopardizing cheese quality or even posing as hazards to consumers. The aim is to determine how mixtures of emulsifying salts (ESSP: emulsifying salt composed of short polyP; BSLP: bacteriostatic salt composed of long polyP; and trisodium citrate) can influence the microbial populations in PC during 90 days of storage. A total of 14 treatments (T1 - T14) were evaluated against eight target strains (Bacillus cereus INV 10(3); Bacillus subtilis ATCC 19659; Bacillus thuringiensis CFBP 3476; Clostridium perfringens ATCC 13124; Enterococcus faecalis FAIR-E 179; Listeria monocytogenes Scott A; Pseudomonas fluorescens 07A; and Staphylococcus aureus ATCC 6538) inoculated into PC. A treatment composed of emulsifying salts without antimicrobial effect (ESSP 1.5%) was considered as the positive growth control, and another treatment composed of antimicrobial additives (nisin and potassium sorbate) was considered as the negative growth control. Bacterial growth was analyzed using ANOVA and Tukey (p < 0.05), based on selected treatment grouping. Most treatments resulted in some level of bactericidal or bacteriostatic effect against the target microorganisms. Bactericidal activity was evident against Bacillus spp., and bacteriostatic effect was clear against C. perfringens, E. faecalis, L. monocytogenes and S. aureus (p < 0.05) during the storage period. T13, composed of 1.5% BSLP, presented results comparable to those observed for the negative control for bacterial inhibition in PC samples during 90 days of storage. T13 was able to reduce the B. cereus INV 10(3) and B. thuringiensis CFBP 3476 population more than the negative control (p < 0.001), as well as present better results for the inhibition of C. perfringens ATCC 13124 and L. monocytogenes Scott A by the end of storage. The performance of the negative control was better than T13 only against S. aureus - ATCC 6538 (p < 0.001). Taken together, the results contribute to expanding the understanding of emulsifying salt application in PC, with a focus on microbiological safety and shelf-life.