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°C) were used. The D-values obtained were 0-14 min at 8 MPa and 38°C, and 0.15 min at 10 MPa and 36°C. 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°C in the media, including significant levels of CO₂, and the CO₂ resistance constant was Z_temp.(γ) = 7.2 γ. 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.