Purpose: Here we investigated the microbial quality and safety of cantaloupes and the effectiveness of a commercial processing line employing a chlorine dioxide wash in improving these properties.
Methods: Determination of total plate counts (TPC) and fecal coliform counts (FCC) was performed for individual cantaloupes pre and post wash using the FDA BAM soak method, as well as for environmental samples using environmental sponges. Investigations for presence of Listeria monocytogenes and Salmonella spp. were performed by pooling soak supernatants, selective enrichments, and Modified Moore Swab bacterial concentrates, followed by testing with Neogen Reveal 2.0 lateral flow kits (LFD). Confirmation was done via selective plating, Riboprinting, biochemical testing, 16s sequencing, and real time PCR with pathogen-specific MicroSEQ assays.
Results: TPC were statistically (t-test, P < 0.05) lower for pre-wash (avg. 1.61 × 107 CFU/ml, n = 97) compared to post-wash cantaloupes (average of 5.20 × 107 CFU/ml, n = 93). In contrast, FCC were lower for post-wash (avg. 4.85 × 101) compared to pre-wash cantaloupes (avg. 2.44 × 102). No statistical differences in TPC or FCC were observed between environmental swabs samples taken upstream or downstream of the washing step (n = 23). L. monocytogenes was not detected; however, LFD and real time PCR results indicated the presence of Salmonella spp. in both pre (4 out of 10 by LFD; 3 out of 10 by PCR) and post-wash (10 out of 10 by LFD; 7 out 10 by PCR) cantaloupe pooled samples (isolates later confirmed by other methods as Citrobacter spp. and Proteus spp.).
Significance: This study supports the finding that commercial cantaloupe processing lines employing chlorine dioxide as an intervention step are not effective in improving microbial quality and safety of cantaloupes.