Survival of Escherichia coli in Banana Peels after Sanitation with Sodium Hypochlorite and during Simulated Export Transport Conditions

The efficacy of sodium hypochlorite for banana sanitation was assessed and the survival of Escherichia coli on bananas during simulated export transport from Costa Rica to the United States was evaluated. Bananas (Musa spp., AAA group, Cavendish sub-group) were surface inoculated with E. coli ATCC 25922 (7 log CFU/g) and then immersed for five minutes in sodium hypochlorite solutions (0, 50, 100, 150 and 200 ppm) adjusted to pH 7. The population of inoculated E. coli on banana surface was monitored during simulated export transport conditions (14 ± 1°C; 85–90% relative humidity; clusters packed in polyethylene bags and cardboard boxes). E. coli was enumerated at 0, 1, 5, 7, 12 and 14 days of storage using Tripticase Soy and MacConkey agars incubated at 35 ± 2°C for 24 h. Trials were performed in triplicate. A 100 ppm or higher concentration of sodium hypochlorite yielded at least a 3-log reduction of E. coli. No significant differences (P ≥ 0.05) were found between 100 and 200 ppm of sanitizer. Storage time significantly influenced (P ≤ 0.05) the E. coli population. Approximate 3-log reduction of E. coli was obtained the first day of storage, but afterwards the population remained constant (3–4 log CFU/g).