P3-139 Uneven Distribution of Microorganisms on the Surface of Field-grown Cantaloupes

Wednesday, July 31, 2013
Exhibit Hall (Charlotte Convention Center)
Shefali Dobhal, Oklahoma State University, Stillwater, OK
Guodong Zhang, U.S. Food and Drug Administration, College Park, MD
Dhiraj Gautam, Oklahoma State University, Stillwater, OK
Chris Timmons, Oklahoma State University, Stillwater, OK
Li Ma, Oklahoma State University, Stillwater, OK
Introduction: Cantaloupes have been implicated in a number of foodborne illness outbreaks due to contamination with human pathogens such as Salmonella and Listeria monocytogenes.  However, we have limited understanding on the potential microbial contamination routes, especially in field production.

Purpose: The objectives of this study were to assess the distribution of microorganisms on the surface (top and bottom) of field-grown cantaloupes and to evaluate the effect of washing on removal of these microbes from the cantaloupe surface.

Methods: Mature cantaloupes were harvested from a local organic farm in Central Oklahoma. The microbial population on the surface (top and bottom) of the cantaloupes was assayed for total aerobic bacteria, coliforms, and mold and yeasts, before and after washing with chlorine water (200 ppm) for 2 min.

Results: The microbial populations on the bottom surface (in direct contact with soil) of the cantaloupes were significantly higher (P < 0.05), ranging from 2.19 to 2.24 log CFU/cm2 (aerobic bacteria); 1.47 to 1.69 log CFU/cm2 (coliforms); and 1.94 to 2.06 log CFU/cm2 (mold and yeasts), than those on the top surface (in contact with air). Washing treatment had no significant effect (P ≥ 0.05) on the populations of total aerobic and total coliform bacteria on both surfaces; however, a significant decrease (P < 0.05) in the populations of yeast and molds was observed on the bottom portion of the cantaloupe after washing.

Significance: This study demonstrates that microorganisms are unevenly distributed on the surface of field-grown cantaloupe, with the areas that are in direct contact with soil (bottom) being more contaminated than others. Additionally, washing with chlorinated water had minimal effect on removing contaminating microorganisms from the cantaloupe surface. Field production practices that minimize direct contact of cantaloupes with the soil may serve as a control strategy for ensuring a safer product.