Kinetics of sterilization ofLactobacillus breviscells by the application of high voltage pulses

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Abstract
The technique of irreversible electroporation has been successfully applied to cause a lethal effect onLactobacillus breviscells suspended in phosphate buffer solution, Na2HPO4/NaH2PO4· H2O (0.845/0.186 mM) between parallel plane electrodes. Tests were carried out at different temperatures (24,45,60, and 80°C) to determine if there was a synergistic effect of temperature and electric pulse treatment on the destruction ofL. brevis. Experimental results indicate that the viability (logN/N0; whereN0andNare the number of cells survived per milliliter before and after pulse voltage application, respectively) ofL. brevisdecreased with electric field strengthEand temperatureTand treatment timett. The relations between log(N/N0) andttand log(N/N0) andEindicate that higher field strengths are more effective than higher treatment times in causing destruction ofL. breviscells. It was also found that as the temperature of the liquid medium containingL. breviscells increased from 24 to 60°C, the death rate ofL. breviscells increased with a decrease in the total treatment timett(pulse width × number of pulses applied). The application of an electric field strengthE= 25 kV/cm at 60°C and treatment timett= 10 ms resulted in very high destruction levels ofL. breviscells (N/N0= 10−9). In comparison with existing steam sterilization technology, this new method of sterilization using relatively low temperature and short treatment time could prove to be an excellent method to minimize thermal denaturation of important nutrient components in liquid media. © John Wiley & Sons, Inc.

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