Info

20-min

30-min

90-min

Microorganism

exposure

exposure

exposure

Bacillus subtilis

9/20°

16/20

0/20

Bacillus stearothermophilus

4/20

4/20

0/20

Clostridium sporogenes

3/20

1/20

0/20

Staphylococcus aureus

0/20

0/20

0/20

Salmonella choleraesuis

0/20

0/20

0/20

Pseudomonas aeruginosa

0/20

0/20

0/20

Mycobacterium phiel

0/20

0/20

0/20

Aspergillus niger

0/20

0/20

0/20

Polio 1

0/10

0/10

0/10

Herpes simplex 1

0/10

0/10

0/10

"The number of growers out of the number possible.

"The number of growers out of the number possible.

spectrum of microorganisms encountered in the medical environment from the most resistant bacterial spores, B. subtilis, to the relatively sensitive lipid containing viruses, Herpes simplex 1. Ozone exposure conditions in the medical sterilizer were 12 to 14% ozone concentrations in oxygen, ambient temperature, and 85 to 95% relative humidity. Foodborne human pathogenic bacteria, molds, and viruses are represented by the spectrum of microorganisms listed in the table. In addition, ozone is effective in killing foodborne and waterborne parasites, such as Giar-dia lamblia and Cyrptosporidum parvum.

Reduction of the population of a specific microorganism by a given fraction depends uniquely on the product of the ozone concentration level, C, and exposure time, t. Different microorganisms' mortalities are easily compared by means the "C • t" product for the same reductions (9). For example, the C • t for B. subtilis is much greater than for Herpes simplex 1 for the same population reduction. Furthermore, comparison of disinfection in air and water can be made on a media mass fraction basis, that is, normalization of C • t to the mass of the fluid (10). Using the ratio of the mass of water to air, for example, indicates that a C • t would have to be 500 times greater in air for the same disinfection capability in water. For disinfection applications to food compared to medical sterilization, not only are the specific microorganisms anticipated quite different, the reduction objectives are much lower. In food disinfection, the objective is to reduce the foodborne microorganism populations to level preventing sickness and not to achieve clinical sterilization or twice the C • t required to achieve a zero population.

Besides destroying microorganisms, like mycotoxin-producing molds, ozone has the potential to destroy the mycotoxin itself. For example, patulin found at high levels in some natural apple juice and produced by several Penicillium species can be oxidized and decomposed by ozone rendering it harmless. Research in the oxidation of herbicide and pesticide residue by ozone has also demonstrated promise (11).

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