Inactivation kinetics and cell morphology of E.coli and S.carevisiae trated with ultrasound-assited supercritical CO2

Autores UPV
Revista Food Research International


The inactivation kinetics of Escherichia coli (E. coli) and Saccharomyces cerevisiae (S. cerevisiae) cells in apple juice subjected to supercritical carbon dioxide (SC-CO2) assisted by high power ultrasound (HPU) at different pressures (100¿350 bar, 36 °C) and temperatures (31¿41 °C, 225 bar) were studied. On average, shorter process times were required to achieve the total inactivation of S. cerevisiae (2¿6 min) in apple juice than E. coli (7 min). The inactivation kinetics of E. coli and S. cerevisiae were satisfactorily described by the Peleg Type A and theWeibull model, respectively, considering temperature and pressure as model parameters. Transmission electron microscopy (TEM) and light microscopy (LM) techniques were used to study the cellular changes of SC-CO2 (350 bar, 36 °C, 5 min) and SC-CO2+HPU (350 bar, 36 °C, 5 min, 40W)treated cells. TEMand LMimages revealed that 5 min of SC-CO2 treatment generated minor morphological modifications, although no inactivation of the cells was obtained. However, 5 min of SC-CO2+HPU treatment totally inactivated the population of both microorganisms. SC-CO2 + HPU produced the degradation of the internal cell content and the disruption of the cell wall and plasmalemma, which prevented the possible regrowth of the cells during refrigerated storage.