2.6. Determination of antimicrobial activity of the carrot juice
essential oil with different treatments
The antimicrobial activity of the essential oil with different
treatments was evaluated using the standardised filter paper disk
diffusion method as described previously (Gao et al., 2011). Briefly,
100 ml of a suspension containing approximately 107 colonyforming
units (CFU)/ml of bacteria and 104 spore/ml of fungus
were spread on nutrient agar (NA) and potato dextrose agar
(PDA), respectively. Filter paper disks (6 mm in diameter) were
impregnated with 10 lL (4 mg/ml) of dilutions in dimethyl sulfoxide
(DMSO, Sigma) of the essential oil and placed onto the solid
medium (20 ml) plates. The diameter of inhibition zones (DIZ)
was measured after 24 h of incubation at 37 C for bacteria, after
4–5 d of incubation at 28 C for A. niger and after 24 h of incubation
at 25 C for Yeast. Ten microlitres of gentamicin (4 mg/ml) and
DMSO were used as positive and negative controls respectively.
Tests were performed in triplicate.