Inactivation of mold ascospores and conidiospores suspended in fruit juices by pulsed electric fields

The inactivation of Byssochlamys fulva conidiospores and Neosartoria fischeri ascospores suspended in different fruit juices by high pulsed electric fields (PEF) was studied. A continuous coaxial treatment chamber was used to apply the treatments. The molds were exposed to exponential decay pulses (2 Hz) of different duration periods (2-3.3 mu s) depending on the type of fruit juice. The inactivation of B. fulva conidiospores depended on the treatment time (number of pulses x width of pulses), electric field intensity and fruit juice in which they were treated. The conidiospore inactivation increased when the applied number of pulses was increased. At a constant input voltage (30 kV) the hierarchy of effectiveness for conidiospore inactivation was cranberry > grape > pineapple > orange > apple > tomato. In cranberry juice the population of B. fulva conidiospores decreased almost six log cycles after two pulses, while in tomato juice it decreased less than one log cycle after the same treatment. In apple juice, after eight pulses of treatment at 32.3 kV/cm the number of survivors decreased three log cycles, and at 41.7 kV/cm this number decreased six log cycles. N. fischeri ascospores suspended in cranberry juice were not inactivated by PEF, even after 40 pulses of treatment at 51.0 kV/cm.