Inactivation of Bacillus stearothermophilus by pulsed electric field

B. Stearothermophilus remains alive even under intense electric field, sinc e spores formed are highly resistant to damage from electric field effects. This paper describes the effects of pulsed electric field on B, Stearother mophilus (ATCC no. 12 980), An aqueous suspension of B, Stearothermophilus spores was placed between parallel planar electrodes and subjected to pulse d electric fields of up to 180 kV/cm, which are obtained from a high-voltag e pulsed voltage generator. Either a Blumlein generator or a magnetic compr ession circuit with a semiconductor opening switch was used as the pulsed v oltage generator. The spores that survived the treatment were detected by a colony counting method. The growth activities were measured using a microb ial calorimetry technique, The temperature and pH of the spore suspension r emained unchanged during the treatment. It was found that the growth activi ty of B. Stearothermophilus was affected by the pulsed electric field, whil e no remarkable lethal effect was observed in the range of up to 40 kV/cm.