首页|Effects of direct and in-package pulsed light treatment on inactivation of E. coli O157:H7 and reduction of microbial loads in Romaine lettuce
Effects of direct and in-package pulsed light treatment on inactivation of E. coli O157:H7 and reduction of microbial loads in Romaine lettuce
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NSTL
Elsevier
The microbial safety of fresh produce continues to be a real concern. Novel nonthermal technologies are required to lessen the risk of pathogen contamination. The objective of this research was to develop and evaluate the effects of direct and in-package pulsed light (PL) treatment on the survival of E. coli O157:H7 in Romaine lettuce. Treatment influence on reduction of background microbial loads of Romaine lettuce was also explored. A three strain-cocktail of E. coli O157:H7 was selected for inoculum preparation for their link with foodborne outbreaks. Surface inoculated Romaine lettuce pieces (2.5 x 2.5 cm) was subjected to pulsed light treatment for a maximum of 1 min (63 J/cm(2)). Polyethylene (PE) films of 0.00254, 0.00508 and 0.00762 cm thickness with ample UV transmission (54-83%) ability were used for packaging. PL treatment of 10 s, equivalent to a dose of 10.5 J/cm(2), was considered optimum beyond which wilting of leaves was observed. Both direct and in-package treatment provided greater than 1 log reduction of the pathogen in 1 s (1.05 J/cm(2)). Direct treatment resulted in 2.68 +/- 0.37 log CFU/g reduction of E. coli O157:H7 at optimal dose, whereas log reductions were decreased to 2.52 +/- 0.19, 2.31 +/- 0.34 and 2.18 +/- 0.25 log CFU/g for Romaine lettuce in 0.00254, 0.00508 and 0.00762 cm thickness packaging enclosures respectively. The decrease in log reductions was not significantly (P > 0.05) affected by film thickness. No significant difference (P > 0.05) in E. coli O157:H7 decontamination efficacy between packaged and unpackaged Romaine lettuce was observed due to PL treatment. The initial total aerobic bacteria and mold and yeast populations were also reduced significantly (P < 0.05) by >1 log, due to the treatment. Overall, the results of this work demonstrate that PL treatment may be used to enhance microbial safety and reduce post processing contamination of packaged Romaine lettuce.
NSTL
Elsevier
