The principal mechanisms of microbial inactivation in OH are thermal in nature. Recent research indicates that OH may present mild non-thermal cellular damage due to the presence of the electric field. The principal reason for the additional effect of ohmic treatment may be its low frequency (usually 50e60 Hz), which allows cell walls to build up charges and form pores. As a main consequence of this effect, the D value observed for the microbial inactivation under ohmic heating is reduced when compared to traditional heating methods. This reduction has been observed for Bacillus licheniformis and Escherichia coli (Pereira et al., 2007), Bacillus subtilis Streptococcus thermophilus, and Byssochlamys fulva.