The Effect of Temperature-Assisted High Hydrostatic Pressure on the Survival of Alicyclobacillus acidoterrestris Inoculated in Orange Juice throughout Storage at Different Isothermal Conditions

The purpose of this work was to investigate the population dynamics of the spores and vegetative cells of A. acidoterrestris in orange juice treated with temperature-assisted HHP and stored in different isothermal conditions. For this reason, the spores of two A. acidoterrestris strains were inoculated in commercial orange juice and subjected to HHP treatment at 600 MPa/60 degrees C for 5 and 10 min. Inoculated samples were subsequently stored at 4, 12 and 25 degrees C for 60 days. During storage, the population of A. acidoterrestris was determined before and after heat shock at 80 degrees C for 10 min in order to estimate the quantity of spores and any remaining vegetative cells on the Bacillus acidoterrestris medium agar. Results showed that spore populations decreased by 3.0-3.5 log cycles directly after HHP treatment. Subsequently, no significant changes were observed throughout storage regardless of temperature and bacterial strain. However, at 25 degrees C, an increase of 0.5-1.0 log cycles was noticed. For the remaining vegetative cells, the results illustrated that HHP treatment could eliminate them during storage at 4 and 12 degrees C, whereas at 25 degrees C inactivation was strain-dependent. Therefore, temperature-assisted HHP treatment could effectively inactivate A. acidoterrestris spores in orange juice and ensure that the inhibitory effect could be maintained throughout storage at low temperatures.