A COMPARISON OF OZONATION AND CHLORINATION FOR THE DISINFECTION OF STAINLESS-STEEL SURFACES

Ozonated water and chlorinated sanitizer were compared for effectivene ss against biofilms of milk spoilage bacteria. Stainless steel plates were incubated in UHT-pasteurized milk inoculated with pure cultures o f either Pseudomonas fluorescens (ATCC 949) or Alcaligenes faecalis (A TCC 337). After incubation, the plates were removed and rinsed in ster ile PBS. A control rinsed stainless steel plate was swabbed and plated on standard plate count agar. A second rinsed stainless steel plate w as covered and treated for 2 min with a commercial chlorinated sanitiz er (dichloro-s-triazinetrione), prepared according to the manufacturer 's recommendations; after treatment, the plate was rinsed twice in ste rile PBS, swabbed, and plated on standard plate count agar. A third ri nsed stainless steel plate from the culture was placed in ozonated dei onized H2O (.5 ppm of ozone) for 10 min, rinsed twice as described, sw abbed, and plated. Both ozonation and chlorination reduced bacteria po pulations by >99% at initial cell densities in the range of approximat ely 1.24 x 10(5) to 8.56 x 10(5) cfu/cm(2) for P. fluorescens and 1.53 x 10(4) to 8.56 x 10(5) cfu/cm(2) for A. faecalis in milk films on st ainless steel surfaces.