Combination of supercritical CO2 and high-power ultrasound for the inactivation of fungal and bacterial spores in lipid emulsions

For the first time, this study addresses the intensification of supercritical carbon dioxide (SC-CO2) treatments using high-power ultrasound (HPU) for the inactivation of fungal (Aspergillus niger) and bacterial (Clostridium butyricum) spores in oil-in-water emulsions. The inactivation kinetics were analyzed at different pressures (100, 350 and 550 bar) and temperatures (50, 60, 70, 80, 85 degrees C), depending on the microorganism, and compared to the conventional thermal treatment. The inactivation kinetics were satisfactorily described using the Weibull model. Experimental results showed that SC-CO2 enhanced the inactivation level of both spores when compared to thermal treatments. Bacterial spores (C. butyricum) were found to be more resistant to SC-CO2 + HPU, than fungal (A. niger) ones, as also observed in the thermal and SC-CO2 treatments. The application of HPU intensified the SC-CO2 inactivation of C. butyricum spores, e.g. shortening the total inactivation time from 10 to 3 min at 85 degrees C. However, HPU did not affect the SC-CO2 inactivation of A. niger spores. The study into the effect of a combined SC-CO2 + HPU treatment has to be necessarily extended to other fungal and bacterial spores, and future studies should elucidate the impact of HPU application on the emulsion's stability.

Automated summary

This study investigated the intensification of supercritical carbon dioxide (SC-CO2) treatments using high-power ultrasound (HPU) for inactivating fungal and bacterial spores in oil-in-water emulsions. The results showed that HPU enhanced the inactivation of bacterial spores, but had limited impact on fungal spores.