A comparison of ozonation and chlorination for the disinfection of stainless steel surfaces.

Ozonated water and chlorinated sanitizer were compared for effectiveness against biofilms of milk spoilage bacteria. Stainless steel plates were incubated in UHT-pasteurized milk inoculated with pure cultures of either Pseudomonas fluorescens (ATCC 949) or Alcaligenes faecalis (ATCC 337). After incubation, the plates were removed and rinsed in sterile PBS. A control rinsed stainless steel plate was swabbed and plated on standard plate count agar. A second rinsed stainless steel plate was covered and treated for 2 min with a commercial chlorinated sanitizer (dichloro-s-triazinetrione), prepared according to the manufacturer's recommendations; after treatment, the plate was rinsed twice in sterile PBS, swabbed, and plated on standard plate count agar. A third rinsed stainless steel plate from the culture was placed in ozonated deionized H2O (.5 ppm of ozone) for 10 min, rinsed twice as described, swabbed, and plated. Both ozonation and chlorination reduced bacteria populations by > 99% at initial cell densities in the range of approximately 1.24 x 10(5) to 8.56 x 10(5) cfu/cm2 for P. fluorescens and 1.53 x 10(4) to 8.56 x 10(5) cfu/cm2 for A. faecalis in milk films on stainless steel surfaces.