ABSTRACT
The present research compared the effect of chlorine dioxide (CD) gas, aqueous CD and aqueous sodium hypochlorite (SHC) treatments on the inactivation of a five strain mixture of Listeria monocytogenes - containing biofilms. Four day old biofilms were developed on a stainless steel (SS 304) coupon by using a mixture of five cultures of L. monocytogenes (Scott A, N1-227, 103M, 82 and 311) using a 100% relative humidity (RH) dessicator for incubation at room temperature (22 ± 2 °C). After biofilm development, coupons were rinsed and dried for 2 h and treated with 0.3 mg/l CD gas at 75% RH, 7 mg/l of aqueous CD and 50 mg/l SHC. Initial log(10) population of biofilm cells before CD gas, aqueous CD and SHC treatment was 4.80, 5.09 and 4.95 log(10) CFU/cm(2). The Weibull model was used to fit non-linear survivor curves. Treatments and time points of 0.3 mg/l CD gas and 7 mg/l aq. CD solution were significantly different (p < 0.05). A 10 min treatment of 0.3 mg/l CD gas, 7 mg/l of aq. CD, and 50 mg/l SHC resulted in reductions of 3.21, 3.74 and 3.09 log(10) CFU/cm(2), respectively. At 10 min, all treatments were not statistically different (p > 0.05). Low levels of CD (0.3 mg/l CD gas and 7 mg/l aq. CD solution) for 10 min resulted in similar log reductions compared to 50 mg/l SHC.
