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ARS Home » Northeast Area » Wyndmoor, Pennsylvania » Eastern Regional Research Center » Food Safety and Intervention Technologies Research » Research » Publications at this Location » Publication #277511
Title: Antimicrobial activity of oregano oil on iceberg lettuce with different attachment conditions

Author
item GUNDUZ, GULTEN - Ege University
item Niemira, Brendan
item GONUL, SAHIKA - Ege University
item KARAPINAR, MEHMET - Ege University

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/9/2012
Publication Date: 5/1/2012
Citation: Gunduz, G.T., Niemira, B.A., Gonul, S.A., Karapinar, M. 2012. Antimicrobial activity of oregano oil on iceberg lettuce with different attachment conditions. Journal of Food Science. 77(7):412-415.

Interpretive Summary: In this study, the antimicrobial activity of oregano oil was investigated under different attachment conditions of Salmonella spp. to iceberg lettuce. Inoculated lettuce was either not dried or dried for various times up to 120 minutes, under either static air or moving air. Washing iceberg lettuce with 500 ppm oregano oil for 1, 5 and 10 min reduced the population of Salmonella spp. by (respectively) 95.0%, 97.8% and 99.5%. These reductions were seen following the most challenging inoculation conditions, an inoculum drying period of 120 minutes under moving air. Across all inoculation conditions, increasing in the treatment time significantly increased the reductions in the populations of Salmonella spp. Browning and softening of the lettuce leaf surface was observed after 10 min of treatment with oregano oil. For each treatment time, attachment times and drying under static vs. moving air did not significantly affect the antimicrobial efficacy of the various oregano oil treatments. The results obtained in this study suggest that oregano oil can effectively reduce populations of Salmonella, even for populations that are firmly attached to lettuce leaf surfaces. This information will be useful to processors seeking alternative chemical means of improving the safety of fresh and fresh-cut fruits and vegetables.

Technical Abstract: In this study, the antimicrobial activity of oregano oil was investigated under different attachment conditions of Salmonella spp. to iceberg lettuce. Inoculated lettuce was either not dried or dried for 30 min, 60 min or 120 min, under either static air or moving air. Washing iceberg lettuce with 500 ppm oregano oil for 1, 5 and 10 min reduced the population of Salmonella spp. by (respectively) 1.3, 1.65 and 2.28 log cfu/g following the most challenging inoculation conditions, an inoculum drying period of 120 min under moving air. Across all inoculation conditions, increasing in the treatment time significantly increased the reductions in the populations of Salmonella spp. Browning and softening of the lettuce leaf surface was observed after 10 min of treatment with oregano oil. For each treatment time, attachment times and drying under static vs. moving air did not significantly affect the antimicrobial efficacy of the various oregano oil treatments. The results obtained in this study suggest that oregano oil can effectively reduce populations of Salmonella attached to lettuce leaf surfaces.