Growth of Bacillus cereus on solid media as affected by agar, sodium chloride, and potassium sorbate

The effect of two independent variables: microstructure, as modified by the agar content (1.0, 4.0, 7.0%), and water activity (a(w)), as modified by t he NaCl content (0.5, 2.5, 4.5%), in the absence or in the presence of pota ssium sorbate (0.0; 2,000 ppm) on Bacillus cereus growth on solid media was studied. The time to visible growth (TVG) and the radial growth rate (RGR) of colonies were evaluated. TVG was not affected by microstructure and K-s orbate, although when a(w) was reduced, TVG tended to increase. RGR depende d on linear effects of microstructure and a(w) variables and their interact ion. When K-sorbate was added to cultural media, RGR was reduced significan tly. However, in the presence of K-sorbate, RGR was found to change only wh en a(w) vas varied.