Uneven distribution of microorganisms on the surface of field-grown cantaloupes

Cantaloupes have been implicated in a number of foodborne illness outbreaks due to contamination with human pathogens. However, we have limited understanding on the potential microbial contamination routes, especially in the production fields. We hypothesized that the soil upon which cantaloupe fruit rest can be a source of microbial contamination. Microbial populations on the surfaces of field-grown cantaloupes were enumerated and the effect of washing on the removal of microorganisms from the cantaloupe surfaces was evaluated. The microbial populations on the lower surface (in direct contact with soil) of the cantaloupes were significantly higher (p < 0.05), averaging 2.21 log CFU/cm2 (aerobic bacteria); 1.62 log CFU/cm2 (coliforms); and 2.02 log CFU/cm2 (molds and yeasts), compared to those on the upper surface (exposed to the air). Washing significantly reduced only the populations of yeasts and molds on the lower surfaces of cantaloupes. Scanning electron micrographs showed more microbe-like bodies on the lower surface of cantaloupe than on the top. This study revealed an uneven distribution of microbial populations on the surfaces of field-grown cantaloupes, suggesting that direct contact with soil can be a major source of microbial contamination to fruits. Field production practices that minimize direct contact of cantaloupes with the soil may serve as a control strategy for ensuring a safer product. Also, more effective surface cleaning methods should be explored.