Abstract
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 (3141 °C), pressure (100350 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 °C, a reduction of 6.7 log-cycleswas obtained after 140 min of treatment. However, when HPU (40 W±5 Wand 30 kHz) was applied during the SC-CO2 treatments, a reduction of 7 log-cycleswas achieved after 2 min of treatment for all pressures and temperatures applied. The effect of increasing pressure (from 100 to 350 bar, 36 °C) or temperature (from 31 to 41 °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.
