Almost 3 log of inactivation of spores were achieved using
35 kV cm1 at 50 C and using 10 pulses (Fig. 2b). However, the main
drawbacks are the limitations of the system. Application of PEF at
higher than 10 pulses with the above mentioned conditions will
increase the temperature to higher than 80 C, allowing the milk to
boil inside the treatment chamber and stopping the process because
of electric arcing, which is a very common problem using this novel
technology when high temperatures are reached. Electrical breakdown
of the system can be one of the limiting factors in PEF technology
and result from the presence of bubbles acting as impurities
in the liquid (Góngora-Nieto, Pedrow, Swanson, & Barbosa-Cánovas,
2003). However, in recent years, significant research has been
conducted on the improvement of PEF systems to reduce electrical
breakdown (S. Toepfl, German Institute of Food Technology,
personal communication; K. Kempes, Diversified Technologies, Inc
personal communication). Nevertheless, in Fig. 2b, two interesting
effects can be observed in spore inactivation: the antagonistic effect
of mild thermal treatment (40 C); and a positive effect when more
intense thermal treatment (50 C) is applied. Similar results were
observed for whole milk. However, similar results were also obtained
when spores of B. cereus in skim milk were pressure-treated