In vitro and in situ inhibition of some food-borne pathogens by essential oils from date palm (Phoenix dactylifera L.) spathe.

Essential oils extracted by hydro-distillation form date palm spathe (byproduct from date palm plants) were tested for their antibacterial activity against some food-borne pathogens. Listeria monocytogenes ATCC 7644, Staphylococcus aureus ATCC 29243, Salmonella enterica subsp. enterica serovar Enteritidis ATCC 13076 and E. coli ATCC 25922 were inhibited (11-13 mm inhibition zones) by spathe essential oils (SEOs) using the agar well assay (in vitro test). Staphylococcus aureus ATCC 29243 and E. coli ATCC 25922 were not detected in chicken meat treated with 1% (v/w) SEOs and subjected to abusive storage conditions (20 °C for 18 h). When treated with 0.5% SEO, counts of S. aureus and E. coli increased by only 0.2 and 0.7 log₁₀ cfu/g, respectively, compared to the initial inoculated level in meat samples stored at 20 °C for 18 h. SEOs possessed DPPH radical scavenging activity with IC₅₀ of 0.61 μg/ml. Forty one compounds were major constituents detected by GC-MS analysis of SEOs. 3,4-Dimethoxytoluene (38.12%) and 5,9-Undecadien-2-one (12.45%) were major compounds in extracted oils. Density and refractive index of SEOs were 0.987 and 1.5905, respectively. SOEs are added-value products from date palm, which could be employed in food industry and pharmaceuticals. The study is the first report on antibacterial activity of SEOs against L. monocytogenes ATCC 7644 and other standard food-borne pathogens in agar diffusion assay and food model (chicken meat). DPPH radical scavenging activity of SEOs has not previously been documented.