Effect of storage temperature on the survival or growth of Listeria monocytogenes on whole and fresh-cut produce

Abstract

Whole and fresh-cut produce are minimally processed and, therefore susceptible to microbial contamination. This study examined the survival or growth of Listeria monocytogenes on whole, and fresh-cut produce at different storage temperatures. Fresh fruits (cantaloupes, pears, pineapples, papayas, and watermelon) and vegetables (broccoli, cauliflower, lettuce, kale, and green bell peppers) were cut into 25 g pieces and were spot inoculated with 0.5 mL (8 Log CFU/mL) of Listeria monocytogenes. Inoculated fresh-cut samples were stored at 4°C or 13°C for 6 days. To represent the outer surface of the produce, cantaloupes and green bell pepper disks (20 cm2) were cut with the rind and spot inoculated on the rind part with 0.5 mL of inoculum and were stored at 24°C for 8 days or 4°C for 14 days respectively. Listeria count on all fresh-cut samples except broccoli and cauliflower remained similar throughout the storage time at 4°C. At 13°C, Listeria counts increased significantly (p1 log was observed at both storage conditions. Listeria levels significantly increased in fresh-cut lettuce 13°C but remained stable on kale, cauliflower, and broccoli. Listeria growth was not favored on rind samples with levels remaining stable on cantaloupe rind (8 days at 24°C) and was below the detectable limit of the test on bell pepper after 14 days of storage at 4°C. The results obtained during this experiment serve to establish Listeria monocytogenes ability to survive in the fresh-cut produce stored at 4°C, as well as the favorable growth environment created in these surfaces at 13°C.