Inactivation ofGiardia murisUsing Ozone and Ozone-Hydrogen Peroxide

Abstract

The disinfection effects of the ozone molecule alone and that of ozone decomposition products when inactivating Giardia muris cysts were investigated at bench-scale using two different ozone demand-free laboratory buffer systems. The first water was a 0.05 M phosphate buffer with hydrogen peroxide added at a 10:1 weight ratio. The second water was a 0.05 M phosphate -0.01 M bicarbonate buffer which quickly scavenged radical species from ozone decomposition. The C3H/HeN mouse model was used to assess the infectivity of ozone treated cysts.The phosphate-bicarbonate buffer system had significantly greater (P < 0.05) inactivation of G. muris cysts than that observed in the phosphate bufferperoxide system where ozone was completely decomposed in less than 120 s. Consequently, the design of ozone disinfection processes should maintain ozone residual for disinfection prior to the addition of hydrogen peroxide for the oxidation of other compounds.

Inactivation ofEscherichia coliO157:H7,SalmonellaTyphimurium andListeria monocytogenesin apple juice at different pH levels by gaseous ozone treatment

“…() and Labatiuk et al . () also reported that direct reaction with molecular ozone is more effective for inactivation of micro‐organisms than reaction with radicals arising from decomposition of ozone molecules. Second, the combination effect of ozone with low pH.…”

“…Ozone is more stable at low than at high pH (Khadre et al 2001), which means direct reaction with ozone molecules accounts for the majority of pathogen inactivation in low pH apple juice. Finch et al (1992) and Labatiuk et al (1994) also reported that direct reaction with molecular ozone is more effective for inactivation of micro-organisms than reaction with radicals arising from decomposition of ozone molecules. Second, the combination effect of ozone with low pH.…”

Ozone Processing for Food Preservation: An Overview on Fruit Juice Treatments

“…It has not been well established whether molecular ozone, the radical species or both are responsible for inactivation of microorganisms. Some researchers have suggested that direct reaction with molecular ozone is the predominant mechanism for inactivation of microorganisms, e.g., E. coli, (Finch et al, 1992;Labatiuk et al, 1994;Hunt and Marinas, 1997) while others suggest indirect reactions with radicals to be responsible for inactivation (Bancroft et al, 1984). It is likely that the relative importance of direct and indirect reactions with ozone in determining microbial inactivation responses will vary between microorganisms.…”

Microbial differentiation and changes in susceptibility to antimicrobial agents

“…Halogens (chlorine‐releasing agents and iodine) and ozone are the disinfectants of choice for ridding water supplies of viable cysts, a highly important role when it is considered that only one cyst is required to produce an infection (Jarroll 1988, 1999; Fraker et al . 1992; Labatuik et al . 1994).…”