Résumé :
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A variety of wholesale and retail packaged vegetables and salads were inoculated with a mixture of strains of Listeria monocytogenes and incubated at 4 and 10 °C. Whole rutabagas, butternut squash, and onions, as well as packaged Caesar salad, carrots, coleslaw mix, and stir-fry vegetables were purchased from local supermarkets in the Ottawa area. L. Monocytogenes population levels remained constant on all fresh-cut vegetables stored at 4 °C for 9 days, except for carrots and butternut squash: counts of cell numbers declined on carrots and increased on the butternut squash. Fresh-cut vegetables stored at 10 °C, however, supported good growth oft. Monocytogenes on all vegetables tested, except for chopped carrots, where the population decreased approximately 2 log units over a 9-day storage period. As in the situation with the produce stored at 4 °C, butternut squash supported the highest rate of cell growth. In addition, Caesar salad and coleslaw mix were kept at 25 °C for 1 or 2 days before subsequent storage at 4 or 10 °C to simulate extreme temperature-abuse conditions. In Caesar salad stored at 4 °C, by day 6 an initial 24- and 48-h temperature abuse at 25 °C led to a 1.21- and 2.55-log-unit population increase, respectively, over the control.
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