Ultrasound-assisted supercritical CO2 treatment in continuous regime: Application in Saccharomyces cerevisiae inactivation

Laboratory continuous regime equipment was designed and built for supercritical CO2 microbial inactivation assisted by high power ultrasound (SC-CO2-HPU). Apple juice, previously inoculated with 1 -10 x 10(7) CFU/mI of Saccharomyces cerevisiae, was treated in the equipment at different juice residence times (3.06-9.2 min), temperatures (31-41 degrees C) and pressures (100-300 bars). Inactivation ratios were fitted to a hybrid (boolean-real) model in order to study the effect of the process variables. The maximum inactivation achieved by the system was 7.8 log-cycles. The hybrid model demonstrated that HPU has a significant effect on inactivation after shorter residence times. A multi -objective optimization performed with the hybrid model showed that 6.8 log cycles of inactivation could be obtained after a minimum residence time (3.1 min) with HPU application, whereas under the same conditions but without HPU, the inactivation would be 4.3 log -cycles. Therefore, the ultrasound assisted continuous system has shown a great potential for microbial inactivation using SC-CO2 under mild process conditions. (C) 2016 Elsevier Ltd. All rights reserved.