Efficacy of washing with hydrogen peroxide followed by aerosolized antimicrobials as a novel sanitizing process to inactivate Escherichia coli O157:H7 on baby spinach.

Aerosolization was investigated as a potential way to apply allyl isothiocyanate (AIT), hydrogen peroxide (H(2)O(2)), acetic acid (AA) and lactic acid (LA) on fresh baby spinach to control Escherichia coli O157:H7 during refrigeration storage. In this study, baby spinach leaves were dip-inoculated with E. coli O157:H7 to a level of 6 log CFU/g and stored at 4°C for 24 h before treatment. Antimicrobials were atomized into fog-like micro-particles by an ultrasonic nebulizer and routed into a jar and a scale-up model system where samples were treated. Samples were stored at 4°C for up to 10 days before the survival of the cells was determined. A 2-min treatment with 5% AIT resulted in a >5-log reduction of E. coli O157:H7 on spinach after 2 days refrigeration regardless if the samples were pre-washed or not; however, this treatment impaired the sensory quality of leaves. Addition of LA to AIT improved the antimicrobial efficacy of AIT. In the jar system, washing with 3% H(2)O(2) followed by a 2-min treatment of 2.5% LA+1% AIT or 2.5% LA+2% AIT reduced E. coli O157:H7 population by 4.7 and >5 log CFU/g, respectively, after 10 days refrigeration. In the scale-up system, up to 4-log reduction of bacterial population was achieved for the same treatments without causing noticeable adverse effect on the appearance of leaves. Thus, this study demonstrates the potential of aerosolized AIT+LA as a new post-washing intervention strategy to control E. coli O157:H7 on baby spinach during refrigeration storage.

Huang Y ，Ye M ，Chen H 《-》

Effect of single or combined chemical and natural antimicrobial interventions on Escherichia coli O157:H7, total microbiota and color of packaged spinach and lettuce.

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.

Poimenidou SV ，Bikouli VC ，Gardeli C ，Mitsi C ，Tarantilis PA ，Nychas GJ ，Skandamis PN ... -  《-》

Development of an antimicrobial sachet containing encapsulated allyl isothiocyanate to inactivate Escherichia coli O157:H7 on spinach leaves.

A sachet releasing allyl isothiocyanate (AIT) vapor was developed and its effectiveness as an antimicrobial packaging system for fresh spinach was evaluated. AIT was encapsulated in calcium alginate beads (AIT beads) and the release of AIT as affected by temperature and relative humidity (RH) was determined. The release rate of AIT from beads increased with increased temperature, but was not significantly affected by RH. A low-density polyethylene (LDPE) sachet containing AIT beads (AIT sachet) was prepared and the rate of release of AIT as affected by film thickness and temperature was studied. The release of AIT from sachets increased significantly with decreased LDPE thickness and increased temperature. Finally, antimicrobial effects of the AIT sachet against Escherichia coli O157:H7 and molds and yeasts (MY) on fresh spinach leaves were determined. E. coli O157:H7 and MY had similar sensitivities to AIT vapor. The number of E. coli O157:H7 on spinach leaves (5.6logCFU/leaf) decreased by 1.6-2.6logCFU/leaf at 4°C and 2.1-5.7logCFU/leaf at 25°C within 5days. The reduction of E. coli O157:H7 was significantly greater at 85% RH than at 43% RH. Reductions on control leaves (no AIT sachet) did not exceed 1.2logCFU/leaf under any of the test conditions. Results of the study will be useful when developing antimicrobial packaging systems to increase the microbiological safety and extend the shelf life of spinach and possibly other fresh produces.

Seo HS ，Bang J ，Kim H ，Beuchat LR ，Cho SY ，Ryu JH ... -  《-》

Electrostatic spraying of food-grade organic and inorganic acids and plant extracts to decontaminate Escherichia coli O157:H7 on spinach and iceberg lettuce.

The prevalence of foodborne illnesses is continually on rise. In the U.S.A., Escherichia coli O157:H7 (E. coli) has been associated with several outbreaks in minimally processed foods. Spinach and lettuce pose higher food safety risks and recurring food recalls suggest the insufficiency of current disinfection strategies. We aimed at offering a natural antimicrobial alternative using organic acids (malic, tartaric, and lactic acids [MA, TA, and LA, respectively]) and grape seed extract (GSE) and a novel application method using electrostatic spraying to evenly distribute the antimicrobials onto produce. Spinach and lettuce samples were washed, sanitized with sodium hypochlorite solution (6.25 mL/L), dip inoculated in water containing E. coli (7.0 log CFU/mL) for 24 h, and rewashed with sterile water to remove nonadhered pathogens. The samples were sprayed electrostatically with MA, LA, and GSE alone and in combinations and for comparison, with phosphoric acid (PA) and pH controls with deionized water adjusted to 1.5/2.3/3.6 and stored at 4 °C. When combined with LA (3%), MA (3%) showed 2.1 to 4.0 log CFU/g reduction of E. coli between the days 1 and 14 on spinach and 1.1 to 2.5 log CFU/g reduction on lettuce. Treatment with PA (1.5%) and PA (1.5%)-GSE (2%) exhibited 1.1 to 2.1 log CFU/g inhibition of E. coli on spinach during the 14-d storage. Our findings demonstrated the efficacy of electrostatic spraying of MA, LA, and GSE on fresh produce to improve the safety and lower the public health burden linked to produce contamination. Electrostatic spraying is an emerging technique that can be adopted to improve the distribution and application of antimicrobials during fresh produce sanitation. Relatively simple and quick, the process can access most/all parts of produce surface and offer protection from food pathogens. The use of malic and lactic acids with or without grape seed extract can serve as effective antimicrobials when sprayed electrostatically, lowering the risk from postcontamination issues with spinach and iceberg lettuce. This application technology can be extended to improve the commercial food safety of other produce, fruits, poultry, and meat.

Ganesh V ，Hettiarachchy NS ，Griffis CL ，Martin EM ，Ricke SC ... -  《-》

Effect of chemical sanitizer combined with modified atmosphere packaging on inhibiting Escherichia coli O157:H7 in commercial spinach.

Lee SY ，Baek SY 《-》