EFFECT OF VANILLIN CONCENTRATION, PH AND INCUBATION-TEMPERATURE ON ASPERGILLUS-FLAVUS, ASPERGILLUS-NIGER, ASPERGILLUS-OCHRACEUS AND ASPERGILLUS-PARASITICUS GROWTH

The effects of incubation temperature (10-30 degrees C), pH (3.0-4.0) and vanillin concentration (350-1200 ppm) on the growth of Aspergillus flavus, Aspergillus niger, Aspergillus ochraceus and Aspergillus para siticus were evaluated using potato-dextrose agar adjusted to wafer ac tivity (a(w)) 0.98. The radial growth rates after a lag period followe d zero-order kinetics with constants that varied from 0 (no growth) to 0.63 mm h(-1). The lag period depended on vanillin concentration, pH and incubation temperature. The germination time and the radial growth rates were significantly affected by the three studied variables (P<0 .001). The inhibitory conditions (no growth after 30 days) depend on t he type of mold. A niger, the most resistant species, was inhibited at 15 degrees C, pH 3.0 and 1000 ppm. For A. ochraceus, the most sensiti ve, the inhibitory conditions in presence of 500 ppm vanillin were pH 3.0 and temperature less than or equal to 25 degrees C or pH 4.0 with temperature less than or equal to 15 degrees C. (C) 1997 Academic Pres s Limited.