2.4 Evaluation of antimicrobial activity
All hydrodistilled-essential oils and ethyl acetate
extracts of citrus peels from seven citrus cultivars were tested
for antimicrobial activity against foodborne pathogens by
broth microdilution assay. Twenty microliter of microbial
suspension (cultured and diluted as mentioned above to
yield 106
CFU/ml or spores/ml) was added to 180 microliter
of medium broth to yield a final concentration of 105
CFU/
ml in each well. The extracts were added at the two-fold
dilution manner, ranging from 0.07 to 2.25 mg/ml (dry mass
of crude extract or essential oil), in a 96-well microtiterplate,
which was incubated at 37oC. The microbial growth was
determined at 24 h of incubation by measuring the absorption
at 600 nm. The lowest concentration of crude citrus
extract/hydrodistillated oils required to completely inhibit