Inactivation of Salmonella Senftenberg 775W by ultrasonic waves under pressure at different water activities

The inactivation of Salmonella Senftenberg 775W by ultrasonic waves (20 kHz, 117 μm) under pressure (175 kPa) treatments at sublethal (manosonication; MS) and lethal temperatures (manothermosonication; MTS) in media of different water activities has been investigated. Heat decimal reduction time values increased up to eighteen fold when the water activity was decreased from > 0.99 to 0.93 at 65 °C, but hardly increased the MS resistance. In reduced water activity media (aw of 0.96 and 0.93) a synergistic lethal effect was observed between heat and ultrasound under pressure, being the inactivation rate of Salmonella Senftenberg 775W three times faster than the expected additive rate considering an effect of both bacterial lethal processes. An empirical mathematical equation enabled to predict the DMS and DMTS values obtained at different temperatures and aw in the ranges investigated of Salmonella serovars and also the microbial level of inactivation due to the synergistic lethal effect of MTS treatments in media of reduced aw.This work could be useful for improving sanitation and preservation treatments of foods, especially those in which components protect microorganisms to heat.