Effect of Storage Temperature on the Behaviour of Escherichia coli O157 : H7 and Salmonella enterica Serotype Typhimurium on Salad Vegetables

The behaviour of Escherichia coli O157:H7 and Salmonella Typhimurium on fresh lettuce (Lactuca sativa), cucumber (Cucumis sativus) epidermis and parsley (Petroselinum sativum) under different storage temperatures was studied. Inoculated vegetable pieces were stored at 10 °C, 20 °C and 30 °C and E. coli O157:H7 and S. Typhimurium were enumerated by plate count.At 10 °C, both E. coli O157:H7 and S. Typhimurium declined slowly on all three vegetables whereas at higher temperatures the behaviour was markedly different. On parsley and lettuce at 20 °C S. Typhimurium population returned to roughly the starting count at the end of the experiment whereas it increased in cucumber. Growth of up to 0.9 log cfu/g was observed on parsley for E. coli O157:H7, but population changes on the other vegetables were negligible at 20 °C. At 30 °C growth was observed on all three vegetables for both E. coli O157:H7 and S. Typhimurium.