Reduction of foodborne pathogens in parsley by an improved formulation containing lime and oregano extracts

Parsley (Petroselinum crispum-Apiaceae) has been reported as a vehicle for Salmonella and E. coli O157:H7; and Shigella sonnei has been responsible for shigellosis outbreaks. Plant-derived extracts have been proposed as alternatives to reduce food contamination without modifying food properties, and several extracts have decreased pathogenic bacterial growth in vegetables. The objective of this study was to reduce E. coli O157:H7, Salmonella and Shigella levels inoculated in parsley, after washing with an improved formulation of edible vegetable extracts. Extracts from five edible plants, resuspended in ethanol, were tested for antimicrobial activity and the minimum bactericidal concentration (MBC) determined. Extract mixtures were analysed for synergistic activity. The mixture exhibiting synergism was used to wash parsley samples previously inoculated with 10 5 bacterial cells/ g. Following 0, 1, 3, 5, and 7 d, viable bacterial counts were determined. Chlorine, Citrol, and ethanol were used as controls. Mexican lime and Mexican oregano extracts (4.3 - 4.8 and 1.5 - 2.0 mg/ml MBC, respectively) were selected. Synergistic antimicrobial effects were observed under a 1.25:0.19 mg/ml mixture. The mixture exhibited a > 2 log reduction in the bacterial level in parsley on the first day. In this study, we followed a simple, low cost, and laboursaving extraction system. The antimicrobial efficacy of the improved formulation was clearly demonstrated on parsley. Considering human health and environmental hazards associated with chlorine use, the Mexican lime:oregano mixture provides a viable alternative to chlorine, and is equally effective at significantly reducing bacterial pathogens associated with outbreaks stemming from leafy green vegetables.