Application of high power ultrasound in the supercritical carbon dioxide inactivation of Saccharomyces cerevisiae

[EN] The objective of the study was to analyze the influence of high power ultrasound (HPU) on the supercritical carbon dioxide (SC-CO2) inactivation kinetics of Saccharomyces cerevisiae and to determine the effect of the temperature (31-41 degrees C), pressure (100-350 bar) and composition of the medium (YPD Broth, apple and orange juice) on the process of inactivation. Using a batch-mode SC-CO2 at 350 bar and 36 degrees C, a reduction of 6.7 log-cycles was obtained after 140 min of treatment. However, when HPU (40 W +/- 5 W and 30 kHz) was applied during the SC-CO2 treatments, a reduction of 7 log-cycles was achieved after 2 mm of treatment for all pressures and temperatures applied. The effect of increasing pressure (from 100 to 350 bar, 36 degrees C) or temperature (from 31 to 41 degrees C, 225 bar) did not significantly influence this inactivation level. The application of ultrasound leads to a vigorous agitation and cavitation which could accelerate the SC-CO2 dissolving in the medium. This accelerates the penetration of CO2 into cells and its inactivation mechanisms. In batch operations the application of HPU increases the speed of reaching saturation solubility of CO2 in many liquid media and significantly reduces microbial inactivation times. (C) 2013 Elsevier Ltd. All rights reserved.