Until recently, ohmic heating was commonly thought to kill microorganisms through a thermal effect. However a growing body of evidence suggests that non-thermal effects may occur. Our aim was to determine the kinetics of inactivation of Geobacillus stearothennophilus spores (ATCC 7953) under ohmic and conventional heating using a specially constructed test chamber with capillary sized cells to eliminate potential sources of error and ensure that identical thermal histories were experienced both by conventionally and ohmically heated samples. Ohmic treatments at frequencies of 60 Hz and 10 kHz were compared with conventional heating at 121, 125 and 130 degrees C for four different holding times. Both ohmic treatments showed a general trend of accelerated spore inactivation. It is hypothesized that vibration of polar dipicolinic acid molecules (DPA) and spore proteins to electric fields at high temperature conditions may result in the accelerated inactivation. (C) 2011 Elsevier Ltd. All rights reserved.