This work studies the effect of electric field strength, treatment time, process temperature, and pulse width on the inactivation of Lactobacillus plantarum inoculated in an orange juice-milk based beverage. For any given quantity of energy applied, the highest degree of inactivation was achieved with high field intensities and short treatment times. The inactivation curve had different slopes, one up to application of 200-285 x 10(3) J L-1, a second stage up to application of 813-891 x 10(3) J L-1 in which the inactivation did not increase significantly, and a third stage up to application of 1069-1170 x 10(3) J L-1. When the process temperature was raised to 55 degrees C the inactivation increased by 0.5 cycles, achieving an energy saving of up to 60%. No increase in inactivation was achieved when the pulse width was increased from 2.5 x 10(-6) to 4 x 10(-6) s. The inactivation achieved with L. plantarum in this beverage is less than that reported by other authors in foods with a simpler composition. (c) 2006 Elsevier Ltd. All rights reserved.