Vanillin and pH synergistic effects on mold growth

The combined effects of pH (3.0-4.0) and vanillin concentration (500-1,000 ppm) on the growth of Aspergillus flavus, A. niger, A. ochraceus and A. parasiticus were evaluated in potato-dextrose agar adjusted to a water activity 0.98. Mold germination time and radial growth rates (RGR) were significantly affected by the variables (p<0.05). For equal concentration of the antimicrobial the reduction in pH had important effects lowering the RGR. The lag time increased as vanillin concentration increased and pH decreased. The inverse lag times of each mold could be described by second order polynomials.