Inactivation of Salmonella spp. and Escherichia coli O157:H7 on different food commodities by volatile antimicrobials
Obaidat, Mohammad M.
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We determined the ability of carvacrol, cinnamaldehyde and ally isothiocyanate (AIT) in their vapor phase to inactivate E. coli O157:H7 and Salmonella spp. in whole and sliced tomatoes and their effect against E. coli O157:H7 on the surface and within lettuce and spinach tissues. Cultural and microscopic methods were employed to confirm inactivation of internalized cells on lettuce. Tomatoes samples were treated with various concentrations of antimicrobial in the vapor phase at 4, 10, and 25 ºC in a closed container. Lettuce and spinach were treated at 0, 4, and 10 ºC. On tomatoes, AIT was the most effective antimicrobial followed by cinnamaldehyde. An 8.3 µl/liter AIT reduced Salmonella and E. coli O157:H7 between tomato slices by 1.0 to 3.5 log depending on storage temperature. The same concentration reduced the pathogens to detection limit on tomatoes surface. On lettuce surface, 4 µl/liter AIT, 40 µl/liter carvacrol and cinnamaldehyde reduced O157:H7 by > 4.0 log at 0 and 4 ºC in 4 days and at 10 ºC in 2 days. However, within lettuce tissue, 16 µl/liter AIT, 80 µl/liter carvacrol and cinnamaldehyde reduced the pathogen by 4.0 log at 0 ºC and 2.0 to 4.0 log at 4 ºC in 4 days. These concentrations also reduced the pathogen population by 1.0 to 3.0 log at 10 ºC in 2 days. Inactivating the pathogen on spinach was 1.0 log and 3.0 log less on the surface and within the tissue, respectively, compared to lettuce. Surface disinfection and CSLM micrographs supported the results obtained on lettuce tissue. Following surface disinfection more reduction occurred on infiltrated pathogens compared to water washed samples. The data supports using antimicrobials in the vapor phase may improve the safety of refrigerated sliced tomatoes and leafy greens marketed in packages containing enclosed headspace.