Salmonella recovery from tomato fruit surfaces as affected by ethylene

Abstract

The effect of ethylene on the survival of Salmonella cells residing on unwounded surfaces of tomato (Solanum lycopersicum) fruit was investigated in this study. Inoculated fruit were stored in flow-through chambers that were adjusted to maintain an environment simulating a tomato ripening room. Fruit were held at 20 °C and ≥95% relative humidity after surface inoculation with the low virulence and rifamycin-resistant pathogen S. enterica ssp. enterica serovar Typhimurium strain LT2 (S. Typhimurium). Tomato fruit were treated either with a continuous flow (rate, ≈200 mL·min-1) of air or with ≥150 μL·L-1 ethylene in air. Bacterial recovery at 0, 24, 48, and 72 h after initiation of treatment showed that total populations of the S. Typhimurium cells declined in both the air and ethylene treatments during the first 24 to 48 h of storage, then increased to near initial levels by 72 h, similar to decline and recovery reported by other researchers in nonethylene treatment trials. These results suggest that although Salmonella can survive on the surfaces of tomato fruit in typical ripening rooms, proliferation of Salmonella is neither promoted nor inhibited by ethylene exposure.