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 degrees C, pressure: 80, 100, 120 bar, time: 10-40 min) on Alicyclobacillus acidoterrestris spores (10(6)-10(7) spores/ml) suspended in apple juice. A. acidoterrestris spores were completely inactivated by SC-CO2 to undetectable levels in above 65 degrees C, 100 bar for 40 min and 70 degrees 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. (C) 2009 Elsevier B.V. All rights reserved.