Effect of time before storage and storage temperature on survival of Salmonella inoculated on fresh-cut melons

Abstract

The effects of a waiting period at room temperature (∼22 °C) before refrigerating fresh-cut watermelon, cantaloupe and honeydew pieces contaminated with Salmonella on survival of the inoculated pathogen were investigated. Whole cantaloupes, honeydew melons and watermelons were washed with water, and fresh-cut pieces from individual melons were prepared and inoculated with a five strain cocktail of Salmonella at 10 5 cfu/ml. Populations of aerobic mesophilic bacteria, yeast and mold and Pseudomonas spp. were higher for fresh-cut cantaloupe than for fresh-cut watermelon and honeydew immediately after preparation. Populations of Salmonella, aerobic mesophilic bacteria, yeast and mold and Pseudomonas ssp. in fresh-cut melons left at room temperature for up to 5 h before refrigeration were significantly ( P < 0.05 ) higher than populations in fresh-cut melons stored at 5 °C immediately after preparation. Populations of Salmonella recovered in fresh-cut melon after inoculation with the cocktail of Salmonella strains averaged 2 log 10 cfu/g for all three types of melons. Populations in fresh-cut watermelon and honeydew pieces declined by 1 log when stored immediately at 5 °C for 12 days, while the populations in fresh-cut cantaloupe did not show significant ( P > 0.05 ) changes. Populations of Salmonella in fresh-cut melons stored immediately at 10 °C for 12 days increased significantly ( P < 0.05 ) from 2.0 to 3.0 log 10 cfu/g in watermelon, 1.9 to 3.0 log 10 cfu/g in honeydew and 2.0 to 3.6 log 10 cfu/g in cantaloupe pieces. Holding freshly prepared, contaminated fresh-cut melon pieces at 22 °C for 3 h or more prior to refrigerated storage would increase the chances of Salmonella proliferation, especially if the fresh-cut melons were subsequently stored at an abusive temperature.