The effect of crisping, misting, and storage temperature on the survival or growth of Listeria monocytogenes and natural psychrotrophic bacteria on romaine lettuce.

This article investigates the effects of retail handling practices—specifically crisping, misting, and storage temperature—on the growth of Listeria monocytogenes and natural psychrotrophic bacteria on unbagged whole heads of romaine lettuce. The study found that crisping lettuce by immersion in electrolyzed water (EW), which contains free chlorine (~55 ppm), significantly reduced L. monocytogenes populations more than tap water or no crisping, and this reduction persisted during refrigerated storage at 5 °C and 15 °C. Misting with tap water for 24 hours had a modest additional effect in lowering L. monocytogenes on non-crisped lettuce but did not significantly affect populations on EW-crisped lettuce or natural psychrotrophic bacteria. Storage temperature influenced the growth of natural psychrotrophic bacteria but had less impact on L. monocytogenes populations. The findings suggest that using electrolyzed water during crisping can enhance microbial safety of romaine lettuce in retail settings, while misting and temperature control play more limited roles.