Use of food grade acetic organic acid to prevent Listeria monocytogenes in mozzarella cheese

Objective of the present study was to evaluate the ability of acetic acid to inhibit the growth of L. monocytogenes when added to artificial brine for mozzarella storage. L. monocytogenes inoculated in mozzarella packages were divided in ten series for the treatment with acetic acid at different concentrations: 6.25 mM (ac1), 12.49 mM (ac2), 18.375 mM (ac3), 24.98 mM (ac4), 49.96 mM (ac5), 75 mM (ac6), 99.92 mM (ac7), 133.2 mM (ac8) and 149.87 mM (ac9); moreover, a control series was prepared. All the samples were maintained at 8 ◦ C and analysed at t0 and after 2, 5 and 10 days in triplicate. When applied to brine, acetic acid resulted effective only when its concentration was above 24.98 mM (ac4): in this case no growth was recorded during the sampling sessions. ac1, ac2 and ac3 series, also showed a lower growth with final increases of 2.69, 1.50 and 1.02 Log CFU/g, respectively. With concentrations above 49.96 mM (ac5), counts were always below the detection limit. pH values showed the acidifying effect of treatment exerted. The lowest concentrations of acetic acid with anti- microbial effect did not have significant repercussion on the sensorial characteristics of mozzarella cheese.