Purpose: Our objective was to evaluate Salmonella internalization into mature green tomatoes with cooler pulp temperatures at various temperature differentials, simulating repacking operations.
Methods: Green tomatoes (21°C) were submerged into a 6 log CFU/ml, six strain Salmonella cocktail, maintained at 26, 24, 21, 18, or 16°C (± 5, ± 3, 0°C temperature differentials) for up to 5 minutes. To serve as positive controls, tomatoes were submerged for 30 min. Following submersion, tomatoes were surface sterilized, the stem scar and blossom end skin removed, and cores recovered. Cores were cut into three segments: an upper segment just below the stem scar (A), a middle segment (B), and a lower segment just above the blossom end (C). Salmonella populations in each segment were enumerated by MPN analysis following standard US FDA BAM methods. The effect of temperature differential on Salmonella populations in each segment was analyzed using ANOVA.
Results: Salmonella populations internalized into segment A at -5, -3, 0, 3, 5°C temperature differentials were < 0.08 ± 0.0, 3.5 ± 0.8, < 0.0 8± 0.0, 0.3 ± 0.3, 0.3 ± 0.4, and 0.3 ± 0.6, 0.6 ± 1.0, 0.1 ± 0.1, < 0.08 ± 0.0, < 0.08 ± 0 log MPN/segment, at 30 and 120 s respectively. No significant differences (P ≥ 0.5) in Salmonella internalization into 21°C green tomatoes exist between temperature differentials at either time point. While not significant, internalized Salmonella populations are 0.49 log and 0.27 log MPN/segment greater at -3 and -5°C temperature differentials than those at 3 and 5°C temperature differentials after 120 s submersion.
Significance: Salmonella internalized into 21°C green tomatoes at low levels through the stem scar under all conditions tested; inoculum populations (6 log CFU/ml) are higher than expected under typical repacking operations where sanitizers would be used to prevent cross-contamination through water.