P-003. Inactivation of Inoculated Escherichia coli O157:H7, Listeria monocytogenes and Salmonella Poona on Whole Cantaloupe by Chlorine Dioxide Gas

B. S. M. Mahmoud, R. H. Linton;
Purdue Univ., West Lafayette, IN.

The objectives of this investigation were to study the inactivation of inoculated Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Poona on whole cantaloupe by ClO2 at different concentrations (0.5, 1.0, 1.5, 3.0 and 5.0 mg/l) for 10 min and determine the effect of ClO2 gas on the quality and shelf life of whole cantaloupe during storage at 22oC for 12 days. A 100 µl inoculation of each targeted organism was spotted onto the surface (5 cm2) of cantaloupe rind (approximately 8-9 log CFU/ml) separately, air dried (60 min), and then treated with ClO2 gas at 22°C and 90-95% relative humidity for 10 min. Surviving bacterial populations on cantaloupe surfaces were determined using a membrane transferring method with a non-selective media followed by a selective media. More than a 4.6, 4.3, and 5.0 log CFU/5cm2 reduction of E. coli O157:H7, L. monocytogenes and S. Poona was achieved after treatment with 5.0 mg/l ClO2 gas, respectively for 10 min. Furthermore, treatment with ClO2 gas significantly (p<0.05) reduced the initial microflora (mesophilic bacteria, psychrotrophic bacteria, and yeasts and molds) on cantaloupe and kept them significantly lower than the untreated control during storage at 22oC for 12 days. Treatment with ClO2 gas did not significantly (p>0.05) affect the color of whole cantaloupe and extended the shelf life to 9 days compared to 3 days for the untreated control, when stored at ambient temperature (22oC).