Control of Listeria monocytogenes in San Daniele Dry Cured Ham by Different Technologies: Reduction of L. Monocytogenes in Dry Cured Ham

Abstract

Dry cured ham can be contaminated by L. monocytogenes. It originates from raw meat, from processing plants and room. For this reason, it is sometimes impossible to eliminate it from dry cured ham. However, it is possible to prevent or minimize contamination, and to inhibit or stop its growth. The aim of this paper was to produce and validate different methods for post-processing application in San Daniele dry-ham in order to reduce the concentration of L. monocytogenes by 2–3 log CFU/cmq, or to try and completely eliminate it (0 tolerance). An additional goal was to validate the degree of lethality. The methods used included chemical solutions (1.5% sodium lactate, 1% sodium diacetate, a mix solution of 1.5/1.0% sodium lactate/diacetate), ionized air, water and ozonized air, hydrogen peroxide solution, essential oils, and microbial protective starter (Leuconostoc carnosum). The samples, represented by surfaces of San Daniele dry cured ham (both meat and pig-skin parts), were inoculated with different concentrations of a mix of five L. monocytogenes biotypes. After the inoculum, the samples were treated with the above-mentioned technologies. To assess the effects of each treatment, the survived cells of L. monocytogenes were counted by EN/ISO 11290-2 method. Chemical solutions reduced the concentration of L. monocytogenes by 2–3 log CFU/cmq, ionized air by 3 log CFU/cmq, water and ozonized air respectively by 1–2 log CFU/cmq and 1–3 log CFU/cmq, hydrogen peroxide solution by 2–3 log CFU/cmq, essential oils by 1–3 log CFU/cmq, and microbial protective starter by 3 log CFU/cmq. The resulting data demonstrated that the investigated technologies allowed to eliminate from 1 to 3 log of L. monocytogenes from dry cured ham, both meat and pig skin. The results showed high reproducibility and repeatability, so we recommend using these methods as a post-processing application in San Daniele dry cured ham production.