Cetylpyridinium Chloride (CPC) Spray Treatments Reduce Salmonella on Cantaloupe Surfaces

Introduction: Melons can be contaminated at centralized packaging facilities during post-harvest operations and are susceptible to microbial cross contamination due to contaminated water tanks, grading/sorting equipment, transport vehicles, and workers. Appropriate post-harvest washing and sanitizing procedures can help control Salmonellaand other pathogens on cantaloupe or other melons.  Since the surfaces of cantaloupes are highly rough or irregular, bacteria can easily attach to these surfaces and become difficult to remove. 

Purpose: Cetylpyridinium chloride (CPC) is the active ingredient of some antiseptic oral mouthrinses, and has a broad antimicrobial spectrum with a rapid bactericidal effect on Gram-positive pathogens. The spray application of CPC solutions to cantaloupe may reduce the level of Salmonella surface contamination. 

Methods: Cantaloupe (Athena and Hale's Best Jumbo cultivars) ring plugs (2.5 cm. dia.) were inoculated with a broth culture of Salmonella Michigan (approx. 1.0 x 10⁹ CFU/ml).  After 15 min, plugs were sprayed with 10 ml of a CPC solution (0, 0.2, 0.5 or 1.0%) and held at 37°C for 1 h and 24 h.  Melon plugs were diluted with Butterfield's Phosphate Buffer, shaken and sonicated, and solutions were enumerated on tryptic soy agar.  Texture, quality and color of additional melon samples were evaluated after CPC spray treatments over 14 days storage at 4°C.

Results: A 1.0% (vol/vol) application of CPC reduced Salmonella levels 4.2 - 6.3 log CFU/ml in comparison to the control (P < 0.01).  No significant differences (P > 0.05) were observed in the texture and color of CPC treated melons. Salmonella levels on melons, treated with 1.0% CPC, were lower after 1 h storage as compared to 24 h. And the Hale's Best Jumbo cultivar was more susceptible to CPC treatments than the Athena cultivar.

Significance:  A surface spray application of cetylpyridinium chloride (CPC) can be an alternative antimicrobial post-harvest treatment to reduce pathogen contamination of cantaloupe melons.