Abstract: Synergetic killing effects of mild heat and high hydrostatic pressure on Bacillus spores were studied with colorimetric assay. The results indicated that the rates of leakage of 2,6-pyridinedicarboxylic acid from spores of B.subtilis and B. stearothermophilus treated with mild heat and high hydrostatic pressure are increased significantly (p<0.05). Under several treatment groups (at 50, 60, 70℃ and 550, 600MPa), DPA leakage of spores of B.subtillis and B.stearothermophilus is not different strongly from control group (121℃, 30min) (p>0.05), and structures of spores are destroyed completely, while permeability barriers of spores are demolished. Damage of physical structure of spores is probably the reason for the mild heat and high hydrostatic pressure-induced inactivation of spores of B.subtillis and B.stearothermophilus.

Key words: high hydrostatic pressure (HHP), Bacillus subtilis, Bacillus stearothermophilus, spore, 2,6- pyridinedicarboxylic acid (DPA)