The researchers coated the surface of whole cantaloupes with mixtures containing chitosan, LAE, CO, and EDTA, and then inoculated the fruits with foodborne pathogens: L. monocytogenes
, S. enterica
and E. coli
O157:H7. After storing the cantaloupes at room temperature (21 °C), the researchers investigated changes in the number of bacteria on the surface of the fruit. They also assessed characteristics of the cantaloupes that reflect fruit quality.
During 14-day storage, “[c]hitosan coating with 0.1% LAE, 0.1% EDTA, and 1% CO was the most effective for inactivating foodborne pathogens inoculated on cantaloupes,” the authors write. S. enterica
was particularly sensitive: “This coating caused a >3 log CFU/cm2
reduction of Escherichia coli
O157:H7 and Listeria monocytogenes
immediately after coating, and reduced Salmonella enterica
to below the detection limit during a 14-day storage.”
In addition, they state that the antimicrobial coating reduced the levels of total molds and yeasts on the surface of cantaloupes to the detection limit, and delayed the appearance of visible molds. But visible mold growth was seen on the coated fruits after 4 days of storage. One possible reason for this is that “the coating may not totally block access to oxygen which is required for mold growth,” they note. Other strategies are therefore needed to effectively inhibit molds and yeasts on cantaloupes during their normal shelf life.
Dr. Ma and colleagues also found that the antimicrobial treatments—especially 0.1% LAE, 0.1% EDTA, and 1% CO—significantly slowed ripening of the cantaloupes during storage. After day 6, compared with uncoated fruits, coated cantaloupes were significantly more reddened, less yellowed, and more firm. Although the reason for delayed ripening was unclear, the authors suggest that the treatments may decrease respiration rate or enzyme activity, both of which are responsible for the ripening process. However, the treatments did not affect other quality-associated characteristics such as cantaloupe weight or total solids content.
“These observations suggest that these novel coating formulations have potential to improve the safety and quality of whole cantaloupes,” the authors conclude. “However, the specific role of the antimicrobials must still be elucidated.”
Dr. Parry graduated from the University of Liverpool, England in 1997 and is a board-certified veterinary pathologist. After 13 years working in academia, she founded Midwest Veterinary Pathology, LLC where she now works as a private consultant. She is passionate about veterinary education and serves on the Indiana Veterinary Medical Association’s Continuing Education Committee. She regularly writes continuing education articles for veterinary organizations and journals, and has also served on the American College of Veterinary Pathologists’ Examination Committee and Education Committee.
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