Additive and Aw influence on Listeria monocytogenes behavior in Dry-cured ham packaged both under vacuum and under map conditions

The aim of the paper was to study the behaviour of L. monocytogenes in dry-cured ham in relation to MAP and under-vacuum at different time of storage temperature. Dry-cured ham was cut in pieces and inoculated with a suspension of different strains of L. monocytogenes. Before the packaging, the surfaces of each piece were spread with a solution of sodium lactate (1.5%), of sodium diacetate (1%), and of a mix solution of sodium lactate/sodium diacetate (1.5%/1%). A control without any added additive was also prepared. Then the samples were packaged under vacuum and in MAP (15% CO2/85% N2) and stored at 4°C for 60 days. At 0, 15, 30, 45, 60 days the samples were collected in triplicate and analysed to detect the behaviour or the survival of L. monocytogenes. Data demonstrated that the concentration of L. monocytogenes decreased both in MAP and in under-vacuum packaging. The decreasing is independent from the added additive. It seemed that also the Aw value (0.90) of the control samples could reduce the concentration of L. monocytogenes on the surface of dry-cured ham. In all samples the concentration of L. monocytogenes could be reduced by 2 log after 60 days of storage at 4°C.