Inactivation of Alicyclobacillus acidoterrestris spores in apple juice by supercritical carbon dioxide

We investigated the lethal effect of supercritical carbon dioxide (SC-CO2; temperature: 65, 70 °C, pressure: 80, 100, 120 bar, time: 10–40 min) on Alicyclobacillus acidoterrestris spores (106–107 spores/ml) suspended in apple juice. A. acidoterrestris spores were completely inactivated by SC-CO2 to undetectable levels in above 65 °C, 100 bar for 40 min and 70 °C, 80 bar for 30 min. The SC-CO2 did not affect (p > 0.05) the pH and ˚Brix of apple juice. In electron microscopic observations, the surface and internal morphological changes and extraction of intracellular materials of the treated spores were observed. Our results indicate that SC-CO2 can effectively kill A. acidoterrestris spores in apple juice with no changes to the quality of the juice and also provides a complementary understanding of inactivation action of SC-CO2.