Submitted to: International Journal of Food Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/17/2013
Publication Date: 6/27/2013
Citation: Todd, J., Friedman, M., Patel, J.R., Jaroni, D., Ravishankar, S. 2013. The antimicrobial effects of cinnamon oil against multi-drug resistant Salmonella Newport on organic leafy greens. International Journal of Food Microbiology. 166:193-199. Interpretive Summary: Natural antimicrobials may be used as an alternative to chlorine for treating organic leafy greens at the post-harvest level to prevent pathogen contamination. We evaluated cinnamon oil as a produce wash for reducing Salmonella enterica on four organic leafy vegetables (iceberg and romaine lettuce and natural and baby spinach). Leaf samples inoculated with Salmonella Newport were immersed in 0.1 -0.5% cinnamon oil concentrations for 1-2 min and then stored at 4 or 8°C for 3 days. Surviving S. Newport populations were determined during storage. After 24 h, Salmonella were undetectable in romaine and organic lettuce treated with 0.3% cinnamon oil; whereas 0.5% cinnamon treatment was required to reduce salmonella to undetectable level in baby spinach. The antibacterial activity of cinnamon oil increased with its concentration and exposure time. Storage temperature also influenced the effect of cinnamon oil on the survival of S. Newport on mature spinach, romaine lettuce, and baby spinach. Cinnamon oil should be evaluated further for its antimicrobial activity against other enteric pathogens. This information should be useful to other scientists, regulatory agencies and the fresh produce industry.
Technical Abstract: There is generally no kill-step when preparing salad vegetables, so there is a risk for foodborne illness outbreaks due to consumption of these vegetables. Some essential oils have antimicrobial activities and could provide a natural way to reduce pathogens on fresh produce. The use of a cinnamon oil treatment may reduce the risk presented from consuming raw salad vegetables. The objective of this study was to investigate the antimicrobial activity of cinnamon oil wash against Salmonella enterica on organic leafy greens. Organic romaine and iceberg lettuce, and organic baby and mature spinach were inoculated with Salmonella Newport and then dip treated in a phosphate buffered saline (PBS) control and 3 different concentrations (0.1, 0.3, and 0.5% v/v suspensions in PBS) of cinnamon oil. The treatment time varied at either 1 or 2 min, and storage temperature varied at either 4 or 8°C. Samples were taken at days 0, 1, and 3 for enumeration of surviving S. Newport. For romaine and iceberg lettuces, S. Newport was not recovered on day 1 for 2 min 0.3% and 0.5% cinnamon oil treatments. For mature spinach, S. Newport was not recovered by day 1 for the 2 min 0.3% and 0.5% cinnamon oil treatments stored at 4°C. For baby spinach, there was no recovery of S. Newport by day 1 for all of the 0.5% treatments. There was no recovery of S. Newport by day 3 for both 2 min and 1 min treatments of 0.1% cinnamon oil stored at 8°C. Overall, the cinnamon oil treatments were concentration and time dependent with higher treatment concentrations and longer treatment times providing the greatest reduction in the S. Newport population on the leafy greens. In addition, the treatments had a residual effect with the greatest reduction generally seen on the last day of sampling. Storage temperature exhibited an effect on the survival of S. Newport on mature spinach, romaine lettuce, and baby spinach. Based on the results of this study, cinnamon oil has the potential to be used as a treatment option for washing organic baby and mature spinaches, and iceberg and romaine lettuces.