Kinetics of the Inactivation of Vibrio parahaemolyticus in Weakly Acidic Sodium Chlorite Solution

The kinetics of the inactivation of Vibrio parahaemolyticus in sodium chlorite (NaClO₂) solution was studied in the weakly acidic pH range of 4.0 to 6.5 and at various temperatures. The logarithmic reduction of the survival ratio depended on the concentration-time product, and all the inactivation curves showed a linear reduction phase. The first-order inactivation rate constant (k) increased by approximately twice for every 0.44 unit fall in pH. During the inactivation experiments, no formation of chlorine dioxide occurred. These data indicated that undissociated HClO₂ was the active species governing the inactivation of V. parahaemolyticus. It was also shown that the use of weakly acidic NaClO₂ solutions containing high concentrations of ionized ClO₂^- gave slower kinetics of the inactivation, whereas it could achieve the significant reduction of viable cells of more than 4-log. The k value showed an Arrhenius-type temperature dependence in the temperature range of 5 to 40℃. The apparent activation energy for the inactivation of V. parahaemolyticus was estimated to be 43.5 kJ/mol. The k value increased by approximately 1.8 times for every 10℃ rise in temperature.