Stochastic modeling of S. cerevisiae inactivation by supercritical CO2

Pasteurization of S. cerevisiae in a simple substrate with supercritical CO(2) was performed at 36 degrees C on a laboratory multibatch apparatus of a total volume of 150 mL. The pressure values ranged from 100 to 300 bar. The results show a clear dependence between inactivation ratio and increase of pressure. A mathematical modeling of the process was exploited to fit the experimental evidences: inactivation curves were analyzed using a stochastic model based on the multihit model (1). The nonlinear survival curve shows a shoulder and a tail which represent the lag and the resistant phase, respectively. The meaning of the nonlinear relationship between inactivation ratio and time is also discussed; the effect of pressure on the values assumed by the parameters of the model proposed was investigated.