ARS | Publication request: Essential oils reduce Escherichia coli O157:H7 and Salmonella on iceberg and romaine lettuce without affecting produce quality

Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: February 9, 2012
Publication Date: June 25, 2012
Citation: Yossa, N., Patel, J.R., Millner, P.D., Lo, Y. 2012. Essential oils reduce Escherichia coli O157:H7 and Salmonella on iceberg and romaine lettuce without affecting produce quality. Annual Meeting of the Institute of Food Technologists. Paper No. 043-33.

Technical Abstract: Foodborne outbreaks associated with the consumption of fresh produce have increased. In an effort to identify natural antimicrobial agents as fresh produce wash; the effect of essential oils in reducing enteric pathogens on iceberg and romaine lettuce was investigated. Cut lettuce pieces (3 x 2 cm) were inoculated with a five-strain cocktail of E. coli O157:H7 or Salmonella (6 log CFU/g), air-dried for ca. 30 min, and then immersed in a treatment solution containing 5 ppm free chlorine, cinnamaldehyde or sporan (800 and 1000 ppm), alone or in combination with 200 ppm acetic acid (20%), for 1 min. Treated leaves were spin-dried and stored at 4°C. Samples were taken on days 0, 2, 7, and 14 for E. coli O157:H7, Salmonella, total coliform, mesophilic and psychrotrophic bacterial populations, and for yeasts and fungi. Up to 3 log reductions in E. coli O157:H7 populations were observed on iceberg lettuce following treatment with cinnamaldehyde-Tween (800T) and Sporan with acetic acid (1000SV). Likewise, Sporan with acetic acid (1000SV) significantly reduced E. coli O157:H7 populations on romaine lettuce at day 0. Cinnamaldehyde alone (800C) or in combination with acetic acid (1000CV) reduced (P < 0.05) E. coli 0157:H7 by up to 3 log cfu/g compared with chlorine at day 14. The effect of essential oils was comparable to chlorine in reducing Salmonella populations on iceberg and romaine lettuce throughout the storage time. The natural microflora of treated lettuce leaves increased during the storage time, but remained the same as those treated with chlorine and control (water). The texture and the color of iceberg and romaine lettuce treated with essential oils were not different from the control lettuce after 10 days. This study demonstrates that Sporan with acetic acid (1000SV) could be used as an effective lettuce wash without adversely affecting leaf color and texture.