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

The inactivation of Byssochlamys fulva conidiospores and Neosartoria fische ri ascospores suspended in different fruit juices by high pulsed electric f ields (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 f ruit juice. The inactivation of B. fulva conidiospores depended on the trea tment time (number of pulses x width of pulses), electric field intensity a nd fruit juice in which they were treated. The conidiospore inactivation in creased when the applied number of pulses was increased. At a constant inpu t voltage (30 kV) the hierarchy of effectiveness for conidiospore inactivat ion was cranberry > grape > pineapple > orange > apple > tomato. In cranber ry juice the population of B. fulva conidiospores decreased almost six log cycles after two pulses, while in tomato juice it decreased less than one l og cycle after the same treatment. In apple juice, after eight pulses of tr eatment at 32.3 kV/cm the number of survivors decreased three log cycles, a nd at 41.7 kV/cm this number decreased six log cycles. N. fischeri ascospor es suspended in cranberry juice were not inactivated by PEF, even after 40 pulses of treatment at 51.0 kV/cm.