Antimicrobial activity of lemongrass oil against Salmonella enterica on organic leafy greens

Abstract

Aims: We investigated the antimicrobial effectiveness of lemongrass essential oil on organic leafy greens, romaine and iceberg lettuces and mature and baby spinach, inoculated with Salmonella Newport. The influences of exposure times and abuse temperatures on bacterial survival were also investigated.

Methods and results: Leaf samples were washed, inoculated with Salm. Newport (6-log CFUml(-1) ) and dried. Inoculated leaves were immersed in solutions containing 0·1, 0·3 or 0·5% lemongrass oil in phosphate-buffered saline for 1 or 2min and then individually incubated at 4 or 8°C. Samples were taken at day 0, 1 and 3 for the enumeration of survivors. Compared to the PBS control, romaine and iceberg lettuces, and mature and baby spinach samples showed between 0·6-1·5-log, 0·5-4·3-log, 0·5-2·5-log and 0·5-2·2-logCFUg(-1) reductions in Salm. Newport by day 3, respectively.

Conclusions: The antimicrobial activity of lemongrass oil against Salm. Newport was concentration and time dependent. The antimicrobial activity increased with exposure time; iceberg samples treated for 2min generally showed greater reductions (P<0·05) than those treated for 1min (c.1-log reduction difference for 0·3 and 0·5% treatments). Few samples showed a difference between refrigeration and abuse temperatures.

Significance and impact of the study: This study demonstrates the potential of lemongrass oil solutions to inactivate Salm. Newport on organic leafy greens.