RESPONSE SURFACE MODELING OF LISTERIA MONOCYTOGENES INACTIVATION ON LETTUCE TREATED WITH ELECTROLYZED OXIDIZING WATER

Electrolyzed oxidizing water has been estimated that it has strong bactericidal activity and has been widely used as a disinfectant for inactivating microbial organisms. The combined effects of temperature (15-35C), chlorine concentration of electrolyzed oxidizing water (30-70 ppm) and treatment time (1-5 min) on the reduction of Listeria monocytogenes in lettuce were investigated. Reductions of 1.39-2.79 log(10) cfu/g were observed in different combinations of the three factors. Also, a quadratic equation for L. monocytogenes inactivation kinetic was developed by multiple regression analysis using response surface methodology. The predicted values were shown to be significantly in good agreement with experimental values because the adjusted determination coefficient (R-2(Adj)) was 0.9578 and the level of significance was P < 0.0001. Besides, average mean deviation (E%), bias factor (B-f) and accuracy factor (A(f)), which are validation indicators of the model were 0.0218, 1.0003 and 1.0220, respectively. Thus, predicted model showed a good correlation between the experimental and predicted values, indicating success at providing reliable predictions of L. monocytogenes growth in lettuce.