A laboratory scale continuous flow unit was set up and used to study the effect of pulsed electric fields (PEF) pretreatments on the inactivation of microbial population by high pressure carbon dioxide (HPCD). McIlvaine buffer solution inoculated with Escherichia coli cells ATCC26 were pretreated with PEF (25 °C) at different field strength (E=6-12 kV/cm) and energy input (WT=10-40 J/mL) and then processed with HPCD (25 °C) at pressures of 8.0, 11.0 and 14.0 MPa and holding times of 4, 7 and 11 min. Results showed that treating microbial suspensions only with PEF the maximum inactivation level achieved was 2.25 Log-cycles at 12 kV/cm and 40 J/mL. On the other hand, when the bacterial cells were treated only with HPCD, the inactivation level was almost independent on the applied CO2 pressure, while gradually increased by increasing the holding time up to a maximum value of 2.41 Log-cycles. The combination of PEF and HPCD treatment (8.0 MPa) resulted in a marked increase of the microbial inactivation with increasing the field strength, energy input and holding time. In particular, a clear synergistic effect was evident for holding times longer than 4 min regardless the PEF treatment intensity applied.
Microbial inactivation by a combined PEF-HPCD treatment in a continuous flow system
PATARO, GIANPIERO;DONSI', Giorgio;FERRARI, Giovanna
2012-01-01
Abstract
A laboratory scale continuous flow unit was set up and used to study the effect of pulsed electric fields (PEF) pretreatments on the inactivation of microbial population by high pressure carbon dioxide (HPCD). McIlvaine buffer solution inoculated with Escherichia coli cells ATCC26 were pretreated with PEF (25 °C) at different field strength (E=6-12 kV/cm) and energy input (WT=10-40 J/mL) and then processed with HPCD (25 °C) at pressures of 8.0, 11.0 and 14.0 MPa and holding times of 4, 7 and 11 min. Results showed that treating microbial suspensions only with PEF the maximum inactivation level achieved was 2.25 Log-cycles at 12 kV/cm and 40 J/mL. On the other hand, when the bacterial cells were treated only with HPCD, the inactivation level was almost independent on the applied CO2 pressure, while gradually increased by increasing the holding time up to a maximum value of 2.41 Log-cycles. The combination of PEF and HPCD treatment (8.0 MPa) resulted in a marked increase of the microbial inactivation with increasing the field strength, energy input and holding time. In particular, a clear synergistic effect was evident for holding times longer than 4 min regardless the PEF treatment intensity applied.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
