title: Antimicrobial activity of plant essential oils against Escherichia coli O157:H7 and Salmonella on lettuce.
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. Lettuce pieces were inoculated with a five-strain cocktail of Escherichia coli O157:H7 or Salmonella enterica (5 log CFU/g) 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 to determine the surviving populations of E. coli O157:H7, Salmonella, total coliforms, mesophilic and psychrotrophic bacteria, and yeasts and molds during the 14-day storage period. The effect of treatments on lettuce color and texture was also determined. Cinnamaldehyde-Tween (800 ppm, 800T) reduced E. coli O157:H7 by 2.89 log CFU/g (p<0.05) on iceberg lettuce at day 0; Sporan(®)-acetic acid (1000SV) reduced E. coli O157:H7 and Salmonella on iceberg and romaine lettuce by 2.68 and 1.56 log CFU/g (p<0.05), respectively, at day 0. The effect of essential oils was comparable to that of 5 ppm free chlorine in reducing E. coli O157:H7 and Salmonella populations on iceberg and romaine lettuce throughout the storage time. The natural microbiota on treated lettuce leaves increased during the storage time, but remained similar (p>0.05) to 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 14 days of storage. This study demonstrates the potential of Sporan(®) and cinnamaldehyde as effective lettuce washes that do not affect lettuce color and texture.
authors.affiliation: Department of Nutrition and Food Science, University of Maryland, College Park, MD, USA.
authors.forename: Nadine
authors.initials: N
authors.lastname: Yossa
authors.forename: Jitendra
authors.initials: J
authors.lastname: Patel
authors.forename: Patricia
authors.initials: P
authors.lastname: Millner
authors.forename: Sadhana
authors.initials: S
authors.lastname: Ravishankar
authors.forename: Y Martin
authors.initials: YM
authors.lastname: Lo
mesh_terms: D019342:Acetic Acid / Q000494:pharmacology; D000171:Acrolein / Q000031:analogs & derivatives / Q000494:pharmacology; D000890:Anti-Infective Agents / Q000494:pharmacology*; D002713:Chlorine / Q000494:pharmacology; D015169:Colony Count, Microbial; D004202:Disinfectants / Q000494:pharmacology; D019453:Escherichia coli O157 / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D005511:Food Handling; D005516:Food Microbiology; D018545:Lactuca / Q000382:microbiology*; D009822:Oils, Volatile / Q000494:pharmacology*; D018515:Plant Leaves / Q000382:microbiology; D010938:Plant Oils / Q000494:pharmacology; D019779:Salmonella enterica / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D013997:Time Factors
chemical_list: D000890:Anti-Infective Agents; D004202:Disinfectants; D009822:Oils, Volatile; D010938:Plant Oils; D002713:Chlorine; D000171:Acrolein; D019342:Acetic Acid; C012843:cinnamaldehyde