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United States Department of Agriculture

Agricultural Research Service

Research Project: INTEGRATED APPROACH TO PROCESS AND PACKAGE TECHNOLOGIES

Location: Residue Chemistry and Predictive Microbiology

Title: Inactivation of Salmonella enterica serovar Typhimurium and quality maintenance of cherry tomatoes treated with gaseous essential oils

Authors
item Yun, Juan -
item Fan, Xuetong
item Li, Xihong -

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 7, 2012
Publication Date: March 1, 2013
Citation: Yun, J., Fan, X., Li, X. 2013. Inactivation of Salmonella enterica serovar Typhimurium and quality maintenance of cherry tomatoes treated with gaseous essential oils. Journal of Food Science. 78(3)458-464.

Interpretive Summary: Fresh tomatoes have been linked with a number of Salmonella outbreaks since 1998 in the United States. Techniques that can effectively inactivate the bacterial pathogen are needed. In the study, essential oils and their major components used as gaseous antimicrobial were investigated for their efficacy in inactivating the bacterium. Results revealed that Salmonella population on tomato fruit could be reduced by more than 99.99% without negatively impacting fruit quality after treatment with the naturally occurring plant extracts and their major constitutes. Therefore, gaseous essential oils provide effective alternatives to synthetic chemical sanitizers for the produce industry to enhance the microbial safety of tomatoes.

Technical Abstract: The antimicrobial activity of the essential oils (EOs) from cinnamon bark, oregano, mustard and of their major components cinnamaldehyde, carvacrol, and allyl isothiocyanate (AIT) were evaluated as a gaseous treatment to reduce Salmonella enterica serovar Typhimurium in vitro and on tomatoes. In diffusion tests, mustard EO and AIT showed the greatest inhibition of Salmonella, followed by cinnamon EO and cinnamaldehyde, while oregano and carvacrol showed the least inhibition. SEM images of S. Typhimurium on tomatoes suggest that the EOs and their major components damaged the bacterial cell wall and membrane, and the damage was more obvious after post-treatment storage at 10C for 4 and 7 days. Salmonella on inoculated tomatoes was reduced by more than 5 log CFU/g by mustard EO and AIT, by 4.56 and 3.79 log CFU/g following cinnamon EO and cinnamaldehyde treatments, respectively, and 1.54 and 3.37 log CFU/g after oregano EO and carvacrol treatments, respectively. Mustard EO and AIT induced discoloration, softening, and loss of the vitamin C and lycopene during 21 days of storage at 10C, while treatment with cinnamon EO and cinnamaldehyde did not result in significant changes in tomato quality. Tomatoes treated with oregano EO had better quality compared with non-treated samples after storage. Therefore, treatment with cinnamon and oregano EO and their major components appeared to be feasible for inactivation of Salmonella on tomatoes and maintaining quality.

Last Modified: 7/25/2014