Foodborne pathogen inactivation in fruit juices utilizing commercial scale high-pressure processing: Effects of acidulants and pH.

The effects of juice pH, type of acidulant, and post-treatment refrigeration on the high-pressure processing (HPP) inactivation of O157:H7, , and in acid beverages were evaluated. Inoculated apple, orange, and grape juices (at their original pH and adjusted to pH 4.00, 4.50, and 5.00) were treated at 550 MPa for 1 min at 5 °C. In addition, inoculated model solutions acidified to a pH of 5.00 with acetic, citric, malic, and tartaric acids were treated at 400 MPa for 1 min at 5 °C. The effect of refrigerated storage for 24 h after treatment on pathogen inactivation in both experiments was also assessed. A greater than 5-log reduction of the three pathogens inoculated was achieved in all juices immediately after HPP at the juices' original pH, and of under all experimental conditions. Refrigerated storage for 24 h after HPP treatment improved the inactivation of O157:H7, to >5-log reduction, at pH 4.00 in apple juice and of in the three juices at pH 4.00. The type of acidulant did not significantly (> 0.01) affect or inactivation in acidified model solutions but a greater than 5-log reduction after HPP was only achieved for when acetic acid was used. The effectiveness of HPP for pathogen inactivation depended largely on product pH and the target pathogen of concern.