Development of Predictive Reduction Models for Escherichia coli as a Function of Sodium Dichloroisocyanurate and Chlorine Dioxide Concentration and Exposure Time

Introduction: There is increasing concern regarding misusing disinfectants and sanitizers such as ethanol, sodium hypochlorite, and hydrogen peroxide for food contact surfaces in the food industry. Examining the efficacy of the concentration of currently used disinfectants and sanitizers is urgently required in the Korean society.

Purpose:   This study aimed to develop predictive reduction models for Escherichia coli in suspension, as a function of sodium dichloroisocyanurate (SDIC), chlorine dioxide (CD), and exposure time using response surface methodology.

Methods:  Under clean condition (bovine albumin 0.3g/L), Escherichia coli ATCC 10536 (initial inoculum, 8-9 log₁₀CFU/mL) in tryptic soy broth was treated with different concentrations of SDIC (100 and 200 ppm) or CD (5, 20, and 35 ppm) for different exposure times (0.5, 2.5, and 5 min for SDIC or 1, 3, and 5 min for CD) following a central composite design. The polynomial reduction models for SDIC or CD on E. coli were used under the clean condition.

Results:  Escherichia coli reduction by 200 ppm SDIC for 0.5, 2.5, and 5 minutes was 0.92, 1.65, and 4.36 log₁₀ CFU/mL, respectively. Also, E. coli reduction by 35 ppm CD for 1, 3, and 5 minutes was 2.49, 2.70, and 3.65 log₁₀ CFU/mL, respectively. The predictive response surface quadratic polynomial models developed were Y=0.28275-0.013382X₁-0.11310X₂+3.44500E^-003X₁X₂+8.16214E^-005X₁² (R²=0.90) for SDIC and Y=0.43231-0.056492X₁-0.097771X₂+9.24167E^-003X₁X₂+3.06333E^-003X₁² (R²=0.99) for CD, where Y was the bacterial reduction (log₁₀CFU/mL), X₁ was the concentration and X₂ was the exposure time.

Significance:  Our predictive reduction models should be validated in developing the optimal concentration and exposure time of disinfectants and sanitizers for inhibiting E. coli on food contact surfaces in the food industry.