T7-09 Practical Validation of Surface Pasteurization of Cantaloupe

Monday, July 27, 2015: 11:00 AM
C124 (Oregon Convention Center)
Chelsea Kaminski, University of California, Davis, CA
Adrian Sbodio, University of California, Davis, CA
Renee Leong, University of California, Davis, CA
Trevor Suslow, University of California, Davis, CA
Introduction: Commercial adoption of surface pasteurization for whole cantaloupes was initiated following outbreaks of Listeria monocytogenes and Salmonella linked to cantaloupes without the benefit of adequate validation data.

Purpose: In response, hot water pasteurization, in combination with antimicrobials, was evaluated on cantaloupe under laboratory and commercial packing conditions for effectiveness against rind-attached and planktonic bacteria.

Methods: A recirculating laboratory-scale wash system was used to establish process parameters. Ultimately, twenty cantaloupes were harvested and received four treatments: a heated wash (65°C, 45 s), a 30 ppm peroxyacetic acid (PAA) spray, or a heated wash followed by PAA spray, with untreated melons providing initial populations of native microbiota. Melons inoculated with Listeria innocua and an attenuated Salmonella Typhimurium were similarly treated. At a commercial facility, melons were collected every 30 min prior to heated wash, following wash (~64°C), following heated wash and a 50 ppm PAA spray, and after final pack. Wash water was quantified for bacterial populations.

Results: In laboratory studies, application of PAA alone did not significantly reduce (P > 0.05) populations of heterotrophs, coliforms, or Enterobacteriaceae on melon rinds (3.6, 2.1, and 2.6 log CFU/cm2) and was ineffective following the heated wash. All treatments more effectively reduced inoculated strains (2.3 - 4.3 log CFU/cm2) than native microbiota (-1.1 - 2.2 log CFU/cm2). Under commercial packing, similar populations (P > 0.05) of coliforms, E. coli, and Enterobacteriaceae (2.5, 1.5, and 2.5 log MPN/100 ml) were maintained in the wash water throughout packing. While the heated wash, with and without PAA spray, were equally as effective against attached bacteria, samples of the final product contained ~1.9 log CFU/cm2 greater populations (n = 40). 

Significance: Although a pasteurization treatment may enhance reductions of attached bacteria and prevent build-up in the recirculating water, care must be taken to prevent re-contamination of melons during final packing.