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United States Department of Agriculture

Agricultural Research Service

Title: Effect of Cell Surface Charge and Hydrophobicity on Attachment of 16 Salmonella Serovars to Cantaloupe Rind and Decontamination with Sanitizers

Authors
item Ukuku, Dike
item Fett, William

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 21, 2006
Publication Date: August 1, 2006
Citation: Ukuku, D.O., Fett, W.F. 2006. Effect of cell surface charge and hydrophobicity on attachment of 16 salmonella serovars to cantaloupe rind and decontamination with sanitizers . Journal of Food Protection. 69(8):1835-1843.

Interpretive Summary: Adherence of bacteria to the cantaloupe rind is favored by surface irregularities such as roughness, crevices, and pits, thus reducing the ability of washing or sanitizer treatments to remove or inactivate attached cells. In this study attachment strength and the efficacy of washing cantaloupes, previously inoculated with Salmonella at 4 to 5 log CFU/cm2, with water, 2.5% H2O2, or 200 ppm chlorine for 2 min with agitation was compared periodically up to 7 days in storage at 5 or 25 deg C post inoculation. The results of this study showed that the strength of attachment for 16 Salmonella strains representing 12 serovars varied during storage at 5 and 25 deg C. From 30 min to 168 h all Salmonella strains showed increased strength of attachment to whole cantaloupe surfaces. The average strength of attachment increased from 0.152 to 0.198 at 25 deg C within 2 h after inoculation. From 4 h to 168 h, the average strength of attachment increased from 0.263 to 0.987 at 25 deg C. The efficacy of the chlorine treatment in eliminating Salmonella from the cantaloupe surface varied depending on the interval between inoculation and treatment. A 4 log reduction was achieved when treatment was applied within 30 min after inoculation, but at 6 h to 7 days of storage at 5 or 25 deg C, population reductions were approximately 2.5 logs. Salmonella was not detected in fresh-cut pieces prepared from melons sanitized within 2 h of inoculation and sanitizing treatment, but was detected in pieces prepared from melons sanitized after storage for six h or longer. The results of this study suggests that to test the efficacy of sanitizer treatments in reducing populations of bacteria inoculated on cantaloupe surfaces, the sanitizers should be applied at 6 h or more hours after inoculation.

Technical Abstract: Strong adherence of bacteria to the cantaloupe rind is favored by surface irregularities such as roughness, crevices, and pits, thus reducing the ability of washing or sanitizer treatments to remove or inactivate attached cells. In this study attachment strength and the efficacy of washing cantaloupes, previously inoculated with Salmonella at 4 to 5 log CFU/cm2, with water, 2.5% H2O2, or 200 ppm chlorine for 2 min with agitation was compared periodically up to 7 days in storage (5 or 25 deg C) post inoculation. The strength of attachment for 16 Salmonella strains representing 12 serovars varied during storage at 5 and 25 deg C. From 30 min to 2 h all Salmonella strains showed increased strength of attachment to whole cantaloupe surfaces. The average strength of attachment increased from 0.152 to 0.198 at 25 deg C. From day 3 to 7, the average strength of attachment increased from 0.833 to 0.866 at 5 deg C and from 0.927 to 0.987 at 25 deg C. Overall, cantaloupe related strains did not attach more strongly than the cantaloupe related strains tested. Washing with water within 30 min post inoculation, but not thereafter, was effective in reducing the populations of attached Salmonella on cantaloupe surfaces. The efficacy of the chlorine treatment in eliminating Salmonella from the cantaloupe surface varied depending on the interval between inoculation and treatment. A 4 log reduction was achieved when treatment was applied within 30 min post inoculation, but at 6 h to 7 days of storage at 5 or 25 deg C, population reductions were approximately 2.5 logs. Salmonella was not detected in fresh-cut pieces prepared from melons sanitized within 2 h, but was detected in pieces prepared from melons sanitized after storage for six h or longer. To test the efficacy of sanitizer treatments in reducing populations of bacteria inoculated on cantaloupe surfaces, the sanitizers should be applied at 6 h or more hours after inoculation.

Last Modified: 3/30/2015
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