Inhibitory activity of an emulsifying salt polyphosphate (JOHA HBS®) used in processed cheese: An in vitro analysis of its antibacterial potential

In the present study, the inhibitory activity of a commercial polyphosphate (JOHA® HBS) was tested in vitro against 21 bacterial strains. Firstly, the antimicrobial activity of JOHA® HBS, at different concentrations (from 0.5 to 2.0%) was evaluated in different agar and broth media (namely, Brain Heart Infusion: BHI; Nutrient: NT; Plate Count: PCA; Trypticase Soy: TSA/B), using streak assay (agar) and culture enumeration (broth). Further more, the bacterial inhibition of JOHA® HBS (at different concentrations, from 0.2% to 3.0%) was evaluated both on NT agar and broth medium, by streak assay, agar-spot method, and by spot-on-the-lawn and well diffusion method. Finally, the JOHA® HBS antimicrobial activity was tested on NT agar at pH 6.3. Results of the streak assay on NT agar showed that 11 out the 21 tested strains were highly inhibited at 0.5% of JOHA® HBS. Interestingly, at adjusted pH levels, JOHA® HBS concentrations of 1.0% (w/v) were able to inhibit the same targets, confirming the antimicrobial effect of JOHA® HBS. This study reveals that NT medium and agar based tests are required to properly test the inhibitory activity of polyphosphates. Furthermore, results confirmed the antimicrobial activity of JOHA® HBS, at low concentrations, against target bacteria of interest to the dairy industry.