Survival of Listeria monocytogenes on a conveyor belt material with or without antimicrobial additives

Survival of Listeria monocytogenes on a conveyor belt material with or without antimicrobial additives, in the absence or presence of food debris from meat, fish and vegetables and at temperatures of 10, 25 and 37 °C was investigated. The pathogen survived best at 10 °C, and better at 25 °C than at 37 °C on both conveyor belt materials. The reduction in the numbers of the pathogen on belt material with antimicrobial additives in the first 6 h at 10 °C was 0.6 log unit, which was significantly higher (P < 0.05) than the reduction of 0.2 log unit on belt material without additives. Reductions were significantly less (P < 0.05) in the presence of food residue. At 37 °C and 20% relative humidity, large decreases in the numbers of the pathogen on both conveyor belt materials during the first 6 h were observed. Under these conditions, there was no obvious effect of the antimicrobial substances. However, at 25 °C and 10 °C and high humidity (60-75% rh), a rapid decrease in bacterial numbers on the belt material with antimicrobial substances was observed. Apparently the reduction in numbers of L. monocytogenes on belt material with antimicrobial additives was greater than on belt material without additives only when the surfaces were wet. Moreover, the presence of food debris neutralized the effect of the antimicrobials. The results suggest that the antimicrobial additives in conveyor belt material could help to reduce numbers of microorganisms on belts at low temperatures when food residues are absent and belts are not rapidly dried.