The influence of dissolved CO2 concentration on the death kinetics of Saccharomyces cerevisiae

Aims: The effects of temperature and concentration of dissolved CO2 on the inactivation of Saccharomyces cerevisiae were investigated using a plug-flow system. Methods and Results: Several combinations of pressure (4, 6, 8, 10 mega-Pa (MPa)) and temperature (30, 34, 36, 38 degreesC) were used. The D-values obtained were 0.14 min at 8 MPa and 38 degreesC, and 0.15 min at 10 MPa and 36 degreesC. The log D-values were related linearly to the treatment temperature and to the dissolved CO2 concentration. The thermal resistance constant (z(CO2),(T)) was 9.5 degreesC in the media, including significant levels of CO2, and the CO2 resistance constant was z(temp).(gamma) = 7.2 gamma. Conclusions: This work has shown that inactivation followed first-order death kinetics, and the effects of temperature and CO2 concentration were consistent through the critical temperature and pressure of CO2. Therefore, it is feasible to estimate D-values at any temperature and any CO2 concentration. Significance and Impact of the Study: Non-thermal inactivation of micro-organisms in acidic beverages could be realized by the present technique.