Effect of naturally occurring antimicrobials and chemical preservatives on the growth of Aspergillus Parasiticus.

Effect of water activity (aw, 0.99), pH (4.5) and
their interaction on the growth inhibition of Aspergillus
parasiticus was studied on potato dextrose agar (PDA) using
various antimicrobial agents (citral, carvacrol, eugenol,
cineole, thymol guaiacol, vanillin, anethol, potassium sorbate
and sorbic acid). The results demonstrate that colony
diameter (mm) exhibited a constant increase with time (zero
order kinetics) for all antimicrobials evaluated. Eugenol and
sorbic acid inhibited the test fungi at 300 and 600 ppm,
respectively. Radial growth rate (RGR) of A. parasiticus was
significantly (p<0.05) different among different antimicrobials
as well as the concentrations tested. However, this
difference was not observed with higher concentration of
citral, eugenol, vanillin and sorbic acid. Among the
antimicrobials evaluated potassium sorbate, cineole, anethol
and guaiacol were least effective. Thymol, eugenol and
carvacrol were more effective in inhibiting A. parasiticus
even with low concentration (150 ppm) as their mean RGR
was zero even after 20 days of incubation (pH 4.5).