title: Effect of single or combined chemical and natural antimicrobial interventions on Escherichia coli O157:H7, total microbiota and color of packaged spinach and lettuce.
abstract: Aqueous extract of Origanum vulgare (oregano), sodium hypochlorite (60 and 300 ppm of free chlorine), Citrox® (containing citric acid and phenolic compounds [bioflavonoids] as active ingredients), vinegar, lactic acid, and double combinations of Citrox, lactic acid and oregano were evaluated against Escherichia coli O157:H7 and total mesophilic microbiota on fresh-cut spinach and lettuce and for their impact on color of treated vegetables. Spinach and lettuce leaves were inoculated with E. coli O157:H7 to a level of 5-6 log CFU/g and immersed in washing solutions for 2 or 5 min at 20 °C, followed by rinsing with ice water (30s). Bacterial populations on vegetables were enumerated immediately after washing and after storage of the samples at 5 °C for 7 days under 20% CO2: 80% N2. No significant post-washing microbial reductions were achieved by chlorinated water, whereas after storage total microbiota was increased by 2.4 log CFU/g on lettuce. Vinegar wash was the most effective treatment causing E. coli O157:H7 reductions of 1.8-4.3 log CFU/g. During storage, pathogen was further decreased to below the detection limit level (<2 log CFU/g) and total microbiota exhibited the highest reductions compared to other treatments. Lactic acid reduced pathogen by 1.6-3.7 log CFU/g after washing; however levels of total microbiota increased by up to 2 log CFU/g on packaged lettuce during storage. Washing lettuce samples with oregano for 2 min resulted in 2.1 log CFU/g reduction of E. coli O157:H7. When Citrox was combined with oregano, 3.7-4.0 log CFU/g reduction was achieved on spinach and lettuce samples, with no significant effect on color parameters. Additionally, rinsing with ice water after decontamination treatments contributed to maintenance of color of the treated vegetables. In conclusion, the results indicated that vinegar, lactic acid or oregano aqueous extract alone or in combination, as alternative washing solutions to chlorine, may be effectively used to control E. coli O157:H7 and sustain acceptable appearance of fresh cut spinach and lettuce.
authors.affiliation: Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, 118 55 Athens, Greece; Laboratory of Food Microbiology and Biotechnology, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, 118 55 Athens, Greece.
authors.forename: Sofia V
authors.initials: SV
authors.lastname: Poimenidou
authors.affiliation: Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, 118 55 Athens, Greece.
authors.forename: Vasiliki C
authors.initials: VC
authors.lastname: Bikouli
authors.affiliation: Laboratory of Food Chemistry, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, 118 55 Athens, Greece.
authors.forename: Chryssavgi
authors.initials: C
authors.lastname: Gardeli
authors.affiliation: Laboratory of Chemistry, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, 118 55 Athens, Greece.
authors.forename: Christina
authors.initials: C
authors.lastname: Mitsi
authors.affiliation: Laboratory of Chemistry, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, 118 55 Athens, Greece.
authors.forename: Petros A
authors.initials: PA
authors.lastname: Tarantilis
authors.affiliation: Laboratory of Food Microbiology and Biotechnology, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, 118 55 Athens, Greece.
authors.forename: George-John
authors.initials: GJ
authors.lastname: Nychas
authors.affiliation: Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, 118 55 Athens, Greece. Electronic address: pskan@aua.gr.
authors.forename: Panagiotis N
authors.initials: PN
authors.lastname: Skandamis
mesh_terms: D019342:Acetic Acid / Q000494:pharmacology; D000890:Anti-Infective Agents / Q000494:pharmacology; D015169:Colony Count, Microbial; D003116:Color; D019453:Escherichia coli O157 / Q000187:drug effects*; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D018545:Lactuca / Q000382:microbiology* / Q000592:standards; D031341:Origanum / Q000737:chemistry; D010936:Plant Extracts / Q000494:pharmacology; D018724:Spinacia oleracea / Q000382:microbiology* / Q000592:standards
chemical_list: D000890:Anti-Infective Agents; D010936:Plant Extracts; D019342:Acetic Acid
keywords: Combined treatments; Decontamination; Escherichia coli O157:H7; Lettuce; Natural antimicrobials; Spinach