Inactivation of Alicyclobacillus acidoterrestris using high pressure homogenization and dimethyl dicarbonate

Vegetative cells and spores of five strains of Alicyclobacillus acidoterrestris (N-1100, N-1108, N-1096, SAC, and OS-CAJ) were screened for their sensitivity to high pressure homogenization (HPH, 0 to 300 MPa) in Bacillus acidoterrestris thermophilic broth. The most and least resistant strains, SAC and OS-CAJ, respectively, were further tested for their sensitivity to inactivation or growth inhibition by dimethyl dicarbonate (DMDC, 250 ppm). The combined effects of HPH and DMDC were then evaluated against SAC spores over a 24-h period after treatment. HPH alone significantly inactivated (P < 0.05) vegetative cells of all five strains. SAC vegetative cells were least affected by HPH, with only about a 0.5-log reduction after the 300-MPa treatment. Spores were not significantly reduced by HPH for any of the five strains. DMDC reduced the initial vegetative cell population by 2 log CFU/ml and significantly increased the time to reach stationary phase. For spores, a 0.5-log decrease from the initial spore population was achieved and growth was not significantly delayed. No significant difference was found between the two strains. Treatment with DMDC plus HPH slightly enhanced the inactivation effect over a 24-h period compared with treatment with HPH alone, but these differences were statistically inconsistent. Although HPH and DMDC treatments may help control vegetative cells of A. acidoterrestris, these treatments may not provide adequate overall control. Neither treatment, alone or in combination, is very effective against spores.