Abstract: Pressure increasing process should be considered because of the different increasing rates of different high-hydrostatic pressures of different equipments and compression heating with the pressure-transmitting fluid. For two strains of Bacillus spores (Bacillus coagulan, Bacillus stearothermophilus ATCC 12980) which are heat-resisted usually in low-acid food, the effects of pressure increasing process on their inactivation, germination, and injury were studied. The results showed that the low target pressure (≤300 MPa) and low initial temperature (≤60 ℃) have more effects on germination of the two Bacillus spores; The percentage of the numbers of germinant and active spores is high accounting for the total numbers of pressure-induced germinant spores after depressurization (the maximum is about 90%); The inactivation rates are both about-1.5 log of the two Bacillus spores, and inactivation rate and injury rate are similar at low target pressure (≥500 MPa) and low initial temperature (≥80 ℃). Furthermore, the different effects on spores at the atmospheric pressure (0.1 MPa) and pressure-assisted thermal processing were compared. The effects on the inactivation and germination of spores by the pressure-assisted thermal processing are more obvious than the thermal processing at the atmospheric pressure, but heat still is an important factor which damnifies the spores.

Key words: high pressure-assisted thermal processing, pressure increasing process, Bacillus spores, inactivation, germination, injury