Allyl isothiocyanate reduces Salmonella enterica Michigan and Listeria monocytogenes on the surface of whole cantaloupe (Cucumis melo L.).
Duckson, Margaret Anne
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Since 2006 there have been four Salmonella enterica and one Listeria monocytogenes foodborne outbreaks linked to whole cantaloupe fruit. No post-harvest intervention to reduce potential contamination on cantaloupe currently exists. The complex surface topography of netted cantaloupes aids bacterial attachment. This research evaluates the use of allyl isothiocyanate (AITC; a natural antimicrobial) to reduce populations of S. enterica Michigan and L. monocytogenes on the surface of cantaloupe. Fifty �[BULLET]l of S. Michigan or L. monocytogenes was inoculated onto whole ��[BULLET]Athena��[BULLET] or ��[BULLET]Hales Best Jumbo��[BULLET] (��[BULLET]HBJ��[BULLET]) cantaloupe fruit in 22 mm diameter circles and allowed to dry for 90 min. resulting in 6.60 log CFU/g. Cantaloupe received either AITC liquid or vapor, sterile deionized water, 200 ppm sodium hypochlorite per circle, or no treatment. All cantaloupes were stored in separate sealed glass desiccators for 1 or 24 h at 25�[BULLET]C or 35�[BULLET]C. To enumerate the bacteria following treatment, 22 mm sections of the rind were removed, homogenized and plated onto appropriate agar. Headspace analysis using Gas Chromatography-Mass Spectrometry (GC-MS) quantified the concentration of each AITC vapor treatment. The texture quality of the pericarp tissue of whole cantaloupes was evaluated after 24 h treatments, followed by two weeks of storage at 4�[BULLET]C. The concentration of vapor ranged from 3.4 to 19.6 �[BULLET]l AITC/L inside the desiccators. The liquid treatment reduced (P < 0.05) S. Michigan populations on ��[BULLET]Athena��[BULLET] (3 log CFU/g) and L. monocytogenes on ��[BULLET]HBJ��[BULLET] (2.6 log CFU/g). The longer exposure time to the AITC vapor (24 h versus 1 h) resulted in a greater reduction of both S. Michigan and L. monocytogenes on ��[BULLET]Athena��[BULLET] and treatments at 35�[BULLET]C reduced microbial populations up to 4.5 times greater (P < 0.05). The highest vapor concentration reduced (P < 0.05) both pathogens at least 3.0 log CFU/g on ��[BULLET]Athena��[BULLET] at 25�[BULLET]C. Generally, bacterial pathogens from the surface of ��[BULLET]Athena��[BULLET] cantaloupe were reduced more than pathogens inoculated on the surface of ��[BULLET]HBJ.��[BULLET] The application of AITC liquid or vapor is a natural alternative post-harvest treatment to 200 ppm free chlorine to reduce the level of bacterial contamination on cantaloupe surfaces for certified organic production.
- Doctoral Dissertations