A comprehensive study on the inactivation of Escherichia coli under nonthermal technologies: High hydrostatic pressure, pulsed electric fields and ultrasound

The inactivation of Escherichia coli under selected treatments using high hydrostatic pressure (HHP), pulsed electric fields (PEF), and ultrasound (US) was studied in apple juice. HHP was carried out from 300 to 600 MPa (0.5–7 min, 21 °C), PEF was applied from 23.07 to 30.76 kV/cm (20–40 °C) using up to 21 pulses, and US was performed in continuous and pulsed mode at 120 μm and temperature from 50 to 60 °C (0–30 min). The best treatment was HHP that inactivated 7 log of bacterial cells in less than 1 min. US also showed positive results (>6 log reduction) after 5 min when temperature was kept at 60 °C regardless of the operation mode. Inactivation with PEF showed about 5 log reduction using the highest electric field strength. The color of the juice showed some changes after processing; the L* value parameter was significantly different (p